4360985
Opposite Interplay Between the Canonical WNT/β-Catenin Pathway and PPAR Gamma: A Potential Therapeutic Target in Gliomas
In gliomas, the canonical Wingless/Int (WNT)/β-catenin pathway is increased while peroxisome proliferator-activated receptor gamma (PPAR-γ) is downregulated. The two systems act in an opposite manner. This review focuses on the interplay between WNT/β-catenin signaling and PPAR-γ and their metabolic implications as potential therapeutic target in gliomas. Activation of the WNT/β-catenin pathway stimulates the transcription of genes involved in proliferation, invasion, nucleotide synthesis, tumor growth, and angiogenesis. Activation of PPAR-γ agonists inhibits various signaling pathways such as the JAK/STAT, WNT/β-catenin, and PI3K/Akt pathways, which reduces tumor growth, cell proliferation, cell invasiveness, and angiogenesis. Nonsteroidal anti-inflammatory drugs, curcumin, antipsychotic drugs, adiponectin, and sulforaphane downregulate the WNT/β-catenin pathway through the upregulation of PPAR-γ and thus appear to provide an interesting therapeutic approach for gliomas. Temozolomide (TMZ) is an antiangiogenic agent. The downstream action of this opposite interplay may explain the TMZ-resistance often reported in gliomas.
45265
Genetics of adult glioma.
Gliomas make up approximately 30% of all brain and central nervous system tumors and 80% of all malignant brain tumors. Despite the frequency of gliomas, the etiology of these tumors remains largely unknown. Diffuse gliomas, including astrocytomas and oligodendrogliomas, belong to a single pathologic class but have very different histologies and molecular etiologies. Recent genomic studies have identified separate molecular subtypes within the glioma classification that appear to correlate with biological etiology, prognosis, and response to therapy. The discovery of these subtypes suggests that molecular genetic tests are and will be useful, beyond classical histology, for the clinical classification of gliomas. While a familial susceptibility to glioma has been identified, only a small percentage of gliomas are thought to be due to single-gene hereditary cancer syndromes. Through the use of linkage studies and genome-wide association studies, multiple germline variants have been identified that are beginning to define the genetic susceptibility to glioma.
14693017
Isolation and Characterization of Tumorigenic, Stem-like Neural Precursors from Human Glioblastoma
Transformed stem cells have been isolated from some human cancers. We report that, unlike other brain cancers, the lethal glioblastoma multiforme contains neural precursors endowed with all of the critical features expected from neural stem cells. Similar, yet not identical, to their normal neural stem cell counterpart, these precursors emerge as unipotent (astroglial) in vivo and multipotent (neuronal-astroglial-oligodendroglial) in culture. More importantly, these cells can act as tumor-founding cells down to the clonal level and can establish tumors that closely resemble the main histologic, cytologic, and architectural features of the human disease, even when challenged through serial transplantation. Thus, cells possessing all of the characteristics expected from tumor neural stem cells seem to be involved in the growth and recurrence of adult human glioblastomas multiforme.
4430962
Identification of human brain tumour initiating cells
The cancer stem cell (CSC) hypothesis suggests that neoplastic clones are maintained exclusively by a rare fraction of cells with stem cell properties. Although the existence of CSCs in human leukaemia is established, little evidence exists for CSCs in solid tumours, except for breast cancer. Recently, we prospectively isolated a CD133+ cell subpopulation from human brain tumours that exhibited stem cell properties in vitro. However, the true measures of CSCs are their capacity for self renewal and exact recapitulation of the original tumour. Here we report the development of a xenograft assay that identified human brain tumour initiating cells that initiate tumours in vivo. Only the CD133+ brain tumour fraction contains cells that are capable of tumour initiation in NOD-SCID (non-obese diabetic, severe combined immunodeficient) mouse brains. Injection of as few as 100 CD133+ cells produced a tumour that could be serially transplanted and was a phenocopy of the patient's original tumour, whereas injection of 105 CD133- cells engrafted but did not cause a tumour. Thus, the identification of brain tumour initiating cells provides insights into human brain tumour pathogenesis, giving strong support for the CSC hypothesis as the basis for many solid tumours, and establishes a previously unidentified cellular target for more effective cancer therapies.
3345100
The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary
The 2016 World Health Organization Classification of Tumors of the Central Nervous System is both a conceptual and practical advance over its 2007 predecessor. For the first time, the WHO classification of CNS tumors uses molecular parameters in addition to histology to define many tumor entities, thus formulating a concept for how CNS tumor diagnoses should be structured in the molecular era. As such, the 2016 CNS WHO presents major restructuring of the diffuse gliomas, medulloblastomas and other embryonal tumors, and incorporates new entities that are defined by both histology and molecular features, including glioblastoma, IDH-wildtype and glioblastoma, IDH-mutant; diffuse midline glioma, H3 K27M–mutant; RELA fusion–positive ependymoma; medulloblastoma, WNT-activated and medulloblastoma, SHH-activated; and embryonal tumour with multilayered rosettes, C19MC-altered. The 2016 edition has added newly recognized neoplasms, and has deleted some entities, variants and patterns that no longer have diagnostic and/or biological relevance. Other notable changes include the addition of brain invasion as a criterion for atypical meningioma and the introduction of a soft tissue-type grading system for the now combined entity of solitary fibrous tumor / hemangiopericytoma—a departure from the manner by which other CNS tumors are graded. Overall, it is hoped that the 2016 CNS WHO will facilitate clinical, experimental and epidemiological studies that will lead to improvements in the lives of patients with brain tumors.
20356267
Targeted delivery of antitumoral therapy to glioma and other malignancies with synthetic chlorotoxin (TM-601)
Targeted therapies for cancer is a rapidly advancing field, but the identification of tumor-specific ligands has proven difficult. Chlorotoxin (CTX) is a small, 36 amino acid neurotoxin isolated from the venom of the Giant Yellow Israeli scorpion Leiurus Quinquestriatus. Interestingly, the peptide has been found to preferentially bind to a variety of human malignancies, but shows little or no binding to normal human tissues. A synthetic version of this peptide (TM-601) has been manufactured and covalently linked to iodine 131 (131I-TM-601) as a means of targeting radiation to tumor cells. Preclinical studies and Phase I clinical trials have been completed in patients with recurrent glioma, a type of malignant brain tumor. These studies demonstrated that intracavitary dosing of 131I-TM-601 appears safe, minimally toxic, and binds malignant glioma with high affinity and for long durations. A Phase II trial of this agent using higher doses of radioactivity and repeated local administrations is underway. In addition, enrolment has begun in a Phase I trial evaluating whether systemically delivered 131I-TM-601 can be used to image metastatic solid tumors and primary gliomas. Due to its small size, selective tumor binding properties, minimal toxicity and relative ease of manipulation, CTX represents a potentially important targeting agent for many cancers.
29217381
Primary brain tumours in adults
The most frequent primary brain tumours in adults are gliomas and primary CNS lymphomas. In gliomas, molecular genetic analysis plays an increasing part in classification and treatment planning, a feature well illustrated by the chemosensitive oligodendrogliomas. Unfortunately, management of glioblastoma is still mainly palliative. Incidence of primary CNS lymphoma has increased strikingly in the past 20 years; substantial progress has been achieved in patients who are immunocompetent with the addition of methotrexate-based chemotherapy to radiotherapy, but the potential neurotoxic effects of this combination in elderly patients is worrisome.
205269411
CBTRUS statistical report: primary brain and central nervous system tumors diagnosed in the United States in 2005-2009.
T he objective of CBTRUS Statistical Report: Primary Brain and Central Nervous System Tumors Diagnosed in the United States in 2005–2009 is to provide a current and comprehensive review of the descriptive epidemiology of primary brain and central nervous system (CNS) tumors in the United States population. CBTRUS has obtained data on all primary brain and CNS tumors from the Centers for Disease Control and Prevention, National Program of Cancer Registries (NPCR) and the National Cancer Institute, Surveillance, Epidemiology and End Results (SEER) program for diagnosis years 2005–2009. Incidence counts and rates of primary malignant and non-malignant brain and CNS tumors are documented by histology, gender, age, race, and Hispanic ethnicity.
11232699
Novel approaches to glioma drug design and drug screening
Introduction: Gliomas are considered the most malignant form of brain tumors, and ranked among the most aggressive human cancers. Despite advance standard therapy the prognosis for patients with gliomas remains poor. Chemotherapy has played an important role as an adjuvant in treating gliomas. The efficacy of the chemotherapeutic drug is limited due to poor drug delivery and the inherent chemo- and radio-resistance. Challenges of the brain cancer therapy in clinical settings are; i) to overcome the chemo- and radio-resistance, ii) to improve drug delivery to tumors and iii) the development of effective drug screening procedures. Areas covered: In this review, the authors discuss clinically important chemotherapeutic agents used for treating malignant gliomas along with novel drug design approaches. The authors, furthermore, discuss the in vitro and in vivo drug screening procedures for the development of novel drug candidates. Expert opinion: The development of novel and highly potent chemotherapeutic agents for both glioma and glioma stem cells (GSCs) is highly important for future brain cancer research. Thus, research efforts should be directed towards developing innovative molecularly targeted antiglioma agents in order to reduce the toxicity and drug resistance which are associated with current forms of therapy. Development of novel pre-clinical drug screening procedures is also very critical for the overall success of brain cancer therapies in clinical settings.
44445916
The Molecular and Genetic Basis of Neurological Tumours
There are no effective therapies for many tumours of the nervous system. This is, in part, a consequence of their location within relatively inaccessible tissues. It is also likely, however, that the unique characteristics of the cells that give rise to these tumours create a set of conditions that facilitate tumour development. Here, we consider recent advances in molecular genetics, the development of mouse models and developmental neurobiology as they relate to tumours of neuroectodermal origin. It is likely that these advances will provide insight into underlying mechanisms and provide a rational framework for the development of effective interventions.
39688
Recent advances in therapy for glioblastoma.
Glioblastoma is the most common primary malignant brain tumor in adults and is a challenging disease to treat. The current standard of care includes maximal safe surgical resection, followed by a combination of radiation and chemotherapy with temozolomide. Despite that, recurrence is quite common, and so we continue to search for more effective treatments both for initial therapy and at the time of recurrence. This article will review recent advances in therapy for glioblastoma, including surgery, radiotherapy, cytotoxic chemotherapies, molecularly targeted agents, and immunotherapy; the role of antiangiogenic agents in the treatment of glioblastoma is discussed in a separate article in this issue of the Archives.
3262543
Proximal events in Wnt signal transduction
The Wnt family of secreted ligands act through many receptors to stimulate distinct intracellular signalling pathways in embryonic development, in adults and in disease processes. Binding of Wnt to the Frizzled family of receptors and to low density lipoprotein receptor-related protein 5 (LRP5) or LRP6 co-receptors stimulates the intracellular Wnt–β-catenin signalling pathway, which regulates β-catenin stability and context-dependent transcription. This signalling pathway controls many processes, such as cell fate determination, cell proliferation and self-renewal of stem and progenitor cells. Intriguingly, the transmembrane receptor Tyr kinases Ror2 and Ryk, as well as Frizzled receptors that act independently of LRP5 or LRP6, function as receptors for Wnt and activate β-catenin-independent pathways. This leads to changes in cell movement and polarity and to the antagonism of the β-catenin pathway.
21322621
Molecular cloning, expression and characterization of human peroxisome proliferator activated receptors gamma 1 and gamma 2.
We describe the molecular cloning and expression of cDNAs encoding human PPAR gamma 1 and PPAR gamma 2. Our sequences are distinct from the published sequence at 3 positions, resulting in nonconservative amino acid substitutions. In humans, PPAR gamma mRNA is expressed in spleen, bone marrow, liver, testis, skeletal muscle and brain, in addition to fat. Three thiazolidinediones were found to 1) displace a radiolabeled thiazolidinedione from both receptors with essentially the same IC50s and 2) to transactivate both PPAR gamma isoforms with similar EC50s in transient cotransfection assays utilizing the adipocyte-specific aP2 promoter. Saturating concentrations of these 3 thiazolidinediones altered the conformation of in vitro synthesized PPAR gamma protein producing a 27 kDa protease-resistant fragment. These results indicate that the antidiabetic effects of thiazolidinediones in humans are likely to be mediated via binding to and transactivation of PPAR gamma 1 and gamma 2.
30643431
Identification of c-MYC as a target of the APC pathway.
The adenomatous polyposis coli gene (APC) is a tumor suppressor gene that is inactivated in most colorectal cancers. Mutations of APC cause aberrant accumulation of beta-catenin, which then binds T cell factor-4 (Tcf-4), causing increased transcriptional activation of unknown genes. Here, the c-MYC oncogene is identified as a target gene in this signaling pathway. Expression of c-MYC was shown to be repressed by wild-type APC and activated by beta-catenin, and these effects were mediated through Tcf-4 binding sites in the c-MYC promoter. These results provide a molecular framework for understanding the previously enigmatic overexpression of c-MYC in colorectal cancers.
6135804
The cyclin D1 gene is a target of the beta-catenin/LEF-1 pathway.
beta-Catenin plays a dual role in the cell: one in linking the cytoplasmic side of cadherin-mediated cell-cell contacts to the actin cytoskeleton and an additional role in signaling that involves transactivation in complex with transcription factors of the lymphoid enhancing factor (LEF-1) family. Elevated beta-catenin levels in colorectal cancer caused by mutations in beta-catenin or by the adenomatous polyposis coli molecule, which regulates beta-catenin degradation, result in the binding of beta-catenin to LEF-1 and increased transcriptional activation of mostly unknown target genes. Here, we show that the cyclin D1 gene is a direct target for transactivation by the beta-catenin/LEF-1 pathway through a LEF-1 binding site in the cyclin D1 promoter. Inhibitors of beta-catenin activation, wild-type adenomatous polyposis coli, axin, and the cytoplasmic tail of cadherin suppressed cyclin D1 promoter activity in colon cancer cells. Cyclin D1 protein levels were induced by beta-catenin overexpression and reduced in cells overexpressing the cadherin cytoplasmic domain. Increased beta-catenin levels may thus promote neoplastic conversion by triggering cyclin D1 gene expression and, consequently, uncontrolled progression into the cell cycle.
206824155
Genome-Wide Profiling of Peroxisome Proliferator-Activated Receptor γ in Primary Epididymal, Inguinal, and Brown Adipocytes Reveals Depot-Selective Binding Correlated with Gene Expression
ABSTRACT Peroxisome proliferator-activated receptor γ (PPARγ) is a master regulator of adipocyte differentiation and function. We and others have previously mapped PPARγ binding at a genome-wide level in murine and human adipocyte cell lines and in primary human adipocytes. However, little is known about how binding patterns of PPARγ differ between brown and white adipocytes and among different types of white adipocytes. Here we have employed chromatin immunoprecipitation combined with deep sequencing to map and compare PPARγ binding in in vitro differentiated primary mouse adipocytes isolated from epididymal, inguinal, and brown adipose tissues. While these PPARγ binding profiles are overall similar, there are clear depot-selective binding sites. Most PPARγ binding sites previously mapped in 3T3-L1 adipocytes can also be detected in primary adipocytes, but there are a large number of PPARγ binding sites that are specific to the primary cells, and these tend to be located in closed chromatin regions in 3T3-L1 adipocytes. The depot-selective binding of PPARγ is associated with highly depot-specific gene expression. This indicates that PPARγ plays a role in the induction of genes characteristic of different adipocyte lineages and that preadipocytes from different depots are differentially preprogrammed to permit PPARγ lineage-specific recruitment even when differentiated in vitro.
13911866
Wnt/beta-Catenin Signaling in Glioma
Extensive data have shown that Wnt/beta-catenin signaling is associated with various disease pathologies, including an important role in tumorigenesis. Here, we review the regulation of Wnt/beta-catenin signaling in glioma, with particular focus on the expression signatures of the main components in Wnt/beta-catenin signaling, the role of key factors in Wnt/beta-catenin signaling, and crosstalk with other signaling pathways. Finally, we discuss the involvement of microRNAs in Wnt/beta-catenin signaling in glioma. This review reveals new insights into the role of Wnt/beta-catenin signaling in gliomagenesis, and highlights new therapeutic approaches for glioma, based on the modulation of the Wnt/beta-catenin pathway.
16727350
Circadian rhythms, Wnt/beta-catenin pathway and PPAR alpha/gamma profiles in diseases with primary or secondary cardiac dysfunction
Circadian clock mechanisms are far-from-equilibrium dissipative structures. Peroxisome proliferator-activated receptors (PPAR alpha, beta/delta, and gamma) play a key role in metabolic regulatory processes, particularly in heart muscle. Links between circadian rhythms (CRs) and PPARs have been established. Mammalian CRs involve at least two critical transcription factors, CLOCK and BMAL1 (Gekakis et al., 1998; Hogenesch et al., 1998). PPAR gamma plays a major role in both glucose and lipid metabolisms and presents circadian properties which coordinate the interplay between metabolism and CRs. PPAR gamma is a major component of the vascular clock. Vascular PPAR gamma is a peripheral regulator of cardiovascular rhythms controlling circadian variations in blood pressure and heart rate through BMAL1. We focused our review on diseases with abnormalities of CRs and with primary or secondary cardiac dysfunction. Moreover, these diseases presented changes in the Wnt/beta-catenin pathway and PPARs, according to two opposed profiles. Profile 1 was defined as follows: inactivation of the Wnt/beta-catenin pathway with increased expression of PPAR gamma. Profile 2 was defined as follows: activation of the Wnt/beta-catenin pathway with decreased expression of PPAR gamma. A typical profile 1 disease is arrhythmogenic right ventricular cardiomyopathy, a genetic cardiac disease which presents mutations of the desmosomal proteins and is mainly characterized by fatty acid accumulation in adult cardiomyocytes mainly in the right ventricle. The link between PPAR gamma dysfunction and desmosomal genetic mutations occurs via inactivation of the Wnt/beta-catenin pathway presenting oscillatory properties. A typical profile 2 disease is type 2 diabetes, with activation of the Wnt/beta-catenin pathway and decreased expression of PPAR gamma. CRs abnormalities are present in numerous pathologies such as cardiovascular diseases, sympathetic/parasympathetic dysfunction, hypertension, diabetes, neurodegenerative diseases, cancer which are often closely inter-related.
34784842
Vasculogenesis and angiogenesis initiation under normoxic conditions through Wnt/β-catenin pathway in gliomas
Abstract The canonical Wnt/β-catenin pathway is up-regulated in gliomas and involved in proliferation, invasion, apoptosis, vasculogenesis and angiogenesis. Nuclear β-catenin accumulation correlates with malignancy. Hypoxia activates hypoxia-inducible factor (HIF)-1α by inhibiting HIF-1α prolyl hydroxylation, which promotes glycolytic energy metabolism, vasculogenesis and angiogenesis, whereas HIF-1α is degraded by the HIF prolyl hydroxylase under normoxic conditions. We focus this review on the links between the activated Wnt/β-catenin pathway and the mechanisms underlying vasculogenesis and angiogenesis through HIF-1α under normoxic conditions in gliomas. Wnt-induced epidermal growth factor receptor/phosphatidylinositol 3-kinase (PI3K)/Akt signaling, Wnt-induced signal transducers and activators of transcription 3 (STAT3) signaling, and Wnt/β-catenin target gene transduction (c-Myc) can activate HIF-1α in a hypoxia-independent manner. The PI3K/Akt/mammalian target of rapamycin pathway activates HIF-1α through eukaryotic translation initiation factor 4E-binding protein 1 and STAT3. The β-catenin/T-cell factor 4 complex directly binds to STAT3 and activates HIF-1α, which up-regulates the Wnt/β-catenin target genes cyclin D1 and c-Myc in a positive feedback loop. Phosphorylated STAT3 by interleukin-6 or leukemia inhibitory factor activates HIF-1α even under normoxic conditions. The activation of the Wnt/β-catenin pathway induces, via the Wnt target genes c-Myc and cyclin D1 or via HIF-1α, gene transactivation encoding aerobic glycolysis enzymes, such as glucose transporter, hexokinase 2, pyruvate kinase M2, pyruvate dehydrogenase kinase 1 and lactate dehydrogenase-A, leading to lactate production, as the primary alternative of ATP, at all oxygen levels, even in normoxic conditions. Lactate released by glioma cells via the monocarboxylate lactate transporter-1 up-regulated by HIF-1α and lactate anion activates HIF-1α in normoxic endothelial cells by inhibiting HIF-1α prolyl hydroxylation and preventing HIF labeling by the von Hippel-Lindau protein. Increased lactate with acid environment and HIF-1α overexpression induce the vascular endothelial growth factor (VEGF) pathway of vasculogenesis and angiogenesis under normoxic conditions. Hypoxia and acidic pH have no synergistic effect on VEGF transcription.
18074845
Thermodynamics in cancers: opposing interactions between PPAR gamma and the canonical WNT/beta-catenin pathway
Cancer cells are the site of numerous metabolic and thermodynamic abnormalities. We focus this review on the interactions between the canonical WNT/beta-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR gamma) in cancers and their implications from an energetic and metabolic point of view. In numerous tissues, PPAR gamma activation induces inhibition of beta-catenin pathway, while the activation of the canonical WNT/beta-catenin pathway inactivates PPAR gamma. In most cancers but not all, PPAR gamma is downregulated while the WNT/beta-catenin pathway is upregulated. In cancer cells, upregulation of the WNT/beta-catenin signaling induces dramatic changes in key metabolic enzymes that modify their thermodynamic behavior. This leads to activation of pyruvate dehydrogenase kinase1 (PDK-1) and monocarboxylate lactate transporter. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-coenzyme A (acetyl-CoA) in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. This leads to aerobic glycolysis in spite of the availability of oxygen. This phenomenon is referred to as the Warburg effect. Cytoplasmic pyruvate is converted into lactate. The WNT/beta-catenin pathway induces the transcription of genes involved in cell proliferation, i.e., MYC and CYCLIN D1. This ultimately promotes the nucleotide, protein and lipid synthesis necessary for cell growth and multiplication. In cancer, activation of the PI3K-AKT pathway induces an increase of the aerobic glycolysis. Moreover, prostaglandin E2 by activating the canonical WNT pathway plays also a role in cancer. In addition in many cancer cells, PPAR gamma is downregulated. Moreover, PPAR gamma contributes to regulate some key circadian genes. In cancers, abnormalities in the regulation of circadian rhythms (CRs) are observed. CRs are dissipative structures which play a key-role in far-from-equilibrium thermodynamics. In cancers, metabolism, thermodynamics and CRs are intimately interrelated.
17688164
Interactions between PPAR Gamma and the Canonical Wnt/Beta-Catenin Pathway in Type 2 Diabetes and Colon Cancer
In both colon cancer and type 2 diabetes, metabolic changes induced by upregulation of the Wnt/beta-catenin signaling and downregulation of peroxisome proliferator-activated receptor gamma (PPAR gamma) may help account for the frequent association of these two diseases. In both diseases, PPAR gamma is downregulated while the canonical Wnt/beta-catenin pathway is upregulated. In colon cancer, upregulation of the canonical Wnt system induces activation of pyruvate dehydrogenase kinase and deactivation of the pyruvate dehydrogenase complex. As a result, a large part of cytosolic pyruvate is converted into lactate through activation of lactate dehydrogenase. Lactate is extruded out of the cell by means of activation of monocarboxylate lactate transporter-1. This phenomenon is called Warburg effect. PPAR gamma agonists induce beta-catenin inhibition, while inhibition of the canonical Wnt/beta-catenin pathway activates PPAR gamma.
17128575
Opposite Interplay between PPAR Gamma and Canonical Wnt/Beta-Catenin Pathway in Amyotrophic Lateral Sclerosis
The opposite interplay between peroxisome proliferator-activated receptor gamma (PPAR gamma) and Wnt/beta-catenin signaling has led to the categorization of neurodegenerative diseases (NDs) as either NDs in which PPAR gamma is downregulated while the canonical Wnt/beta-catenin pathway is upregulated [amyotrophic lateral sclerosis (ALS), Parkinson’s disease, Huntington’s disease, multiple sclerosis, Friedreich’s ataxia] or NDs in which PPAR gamma is upregulated while the canonical Wnt/beta-catenin signaling is downregulated (bipolar disorder, schizophrenia, Alzheimer’s disease). ALS, a common adult-onset debilitating ND, is characterized by a chronic and progressive degeneration of upper and lower motor neurons resulting in muscular atrophy, paralysis, and ultimately death. The intent of this review is to provide an analysis of the integration of these two opposed systems, i.e., canonical Wnt/beta-catenin and PPAR gamma, in ALS. Understanding this integration may aid in the development of novel ALS therapies. Although the canonical Wnt/beta-catenin pathway is upregulated in ALS, riluzole, an enhancer of the canonical Wnt signaling, is classically prescribed in this disease in humans. However, studies carried out on ALS transgenic mice have shown beneficial effects after treatment by PPAR gamma agonists partly due to their anti-inflammatory effects.
13777024
Aerobic Glycolysis Hypothesis Through WNT/Beta-Catenin Pathway in Exudative Age-Related Macular Degeneration
Exudative age-related macular degeneration (AMD) is characterized by molecular mechanisms responsible for the initiation of choroidal neovascularization (CNV). Inflammatory processes are associated with upregulation of the canonical WNT/beta-catenin pathway in exudative AMD. We focus this review on the link between WNT/beta-catenin pathway activation and neovascular progression in exudative AMD through activation of aerobic glycolysis for production of angiogenic factors. Increased WNT/beta-catenin pathway involves hexokinase 2 (HK2) and pyruvate kinase M2 (PKM2). WNT/beta-catenin pathway stimulates PI3K/Akt pathway and then HIF-1alpha which activates glycolytic enzymes: glucose transporter (Glut), pyruvate dehydrogenase kinase 1 (PDK1), lactate dehydrogenase A (LDH-A), and monocarboxylate lactate transporter (MCT-1). This phenomenon is called aerobic glycolysis or the Warburg effect. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-CoA in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. Cytosolic pyruvate is converted into lactate through the action of LDH-A. In exudative AMD, high level of cytosolic lactate is correlated with increase of VEGF expression, the angiogenic factor of CNV. Photoreceptors in retina cells can metabolize glucose through aerobic glycolysis to protect them against oxidative damage, as cancer cells do.
206737822
PPARγ agonists: Potential treatments for exudative age-related macular degeneration.
Choroidal neovascularization (CNV) characterizes the progression of exudative age-related macular degeneration (AMD) with the deterioration in the central vision. Vascular inflammation, and overproduction of inflammatory cytokines, growth factors and aberrant endothelial cell migration, initiate defective blood vessel proliferation in exudative AMD. CNV formation is initiated by the interplay between inflammation, the hallmark of exudative AMD, and the activation of WNT/β-catenin pathway. Upregulation of WNT/β-catenin pathway involves activation of PI3K/Akt pathway and then the Warburg effect to produce lactate. Lactate production generates VEGF expression and then participates to the initiation of CNV in exudative AMD. WNT/β-catenin pathway and PPARγ act in an opposite manner in several diseases. We focus this review on the interplay between PPARγ and canonical WNT/β-catenin pathway and the anti-inflammatory role of PPARγ in exudative AMD. In exudative AMD, PPARγ agonists downregulate inflammation and the WNT/β-catenin pathway. PPARγ agonists can appear as promising treatment against the initiation and the progression of CNV in exudative AMD.
40701525
Glycogen: The forgotten cerebral energy store
The brain contains a significant amount of glycogen that is an order of magnitude smaller than that in muscle, but several‐fold higher than the cerebral glucose content. Although the precise role of brain glycogen to date is unknown, it seems affected by focal activation, neurotransmitters, and overall electrical activity and hormones. Based on its relatively low concentration, the role of brain glycogen as a significant energy store has been discounted. This work reviews recent experimental evidence that brain glycogen is an important reserve of glucose equivalents: (1) glial glycogen can provide the majority of the glucose supply deficit during hypoglycemia for more than 100 min, consistent with the proposal that glial lactate is a fuel for neurons; (2) glycogen concentrations may be as high as 10 μmol/g, substantially higher than was thought previously; (3) glucose cycling in and out of glycogen amounts to ∼1% of the cerebral metabolic rate of glucose (CMRglc) in human and rat brain, amounting to an effective stability of glycogen in the resting awake brain during euglycemia and hyperglycemia, (4) brain glycogen metabolism/concentrations are insulin/glucose sensitive; and (5) after a single episode of hypoglycemia, brain glycogen levels rebound to levels that exceed the pre‐hypoglycemic concentrations (supercompensation). This experimental evidence supports the proposal that brain glycogen may be involved in the development of diabetes complications, specifically impaired glucose sensing (hypoglycemia unawareness) observed clinically in some diabetes patients under insulin treatment. It is proposed further that brain glycogen becomes important in any metabolic state where supply transiently cannot meet demand, such conditions that could occur during prolonged focal activation, sleep deprivation, seizures, and mild hypoxia. © 2003 Wiley‐Liss, Inc.
19684581
Wnt meets Warburg: another piece in the puzzle?
One of the most common abnormalities of cancer cells is their predilection to engage in a high rate of glycolysis despite the continued availability of oxygen. First described by Otto Warburg, this phenomenon of aerobic glycolysis (or the Warburg effect) has recently been proposed to result from cancer‐associated alterations in signal transduction pathways. In this issue of The EMBO Journal, Pate et al provide further support for this hypothesis by demonstrating that Wnt signaling plays an important role in establishing aerobic glycolysis as a mechanism to support in vivo cancer cell proliferation.
29300457
The Organization, Promoter Analysis, and Expression of the Human PPARγ Gene*
PPARγ is a member of the PPAR subfamily of nuclear receptors. In this work, the structure of the human PPARγ cDNA and gene was determined, and its promoters and tissue-specific expression were functionally characterized. Similar to the mouse, two PPAR isoforms, PPARγ1 and PPARγ2, were detected in man. The relative expression of human PPARγ was studied by a newly developed and sensitive reverse transcriptase-competitive polymerase chain reaction method, which allowed us to distinguish between PPARγ1 and γ2 mRNA. In all tissues analyzed, PPARγ2 was much less abundant than PPARγ1. Adipose tissue and large intestine have the highest levels of PPARγ mRNA; kidney, liver, and small intestine have intermediate levels; whereas PPARγ is barely detectable in muscle. This high level expression of PPARγ in colon warrants further study in view of the well established role of fatty acid and arachidonic acid derivatives in colonic disease. Similarly as mouse PPARγs, the human PPARγs are activated by thiazolidinediones and prostaglandin J and bind with high affinity to a PPRE. The human PPARγ gene has nine exons and extends over more than 100 kilobases of genomic DNA. Alternate transcription start sites and alternate splicing generate the PPARγ1 and PPARγ2 mRNAs, which differ at their 5′-ends. PPARγ1 is encoded by eight exons, and PPARγ2 is encoded by seven exons. The 5′-untranslated sequence of PPARγ1 is comprised of exons A1 and A2, whereas that of PPARγ2 plus the additional PPARγ2-specific N-terminal amino acids are encoded by exon B, located between exons A2 and A1. The remaining six exons, termed 1 to 6, are common to the PPARγ1 and γ2. Knowledge of the gene structure will allow screening for PPARγ mutations in humans with metabolic disorders, whereas knowledge of its expression pattern and factors regulating its expression could be of major importance in understanding its biology.
7246740
β-Catenin Signalling in Glioblastoma Multiforme and Glioma-Initiating Cells
Glioblastoma multiforme (GBM) is a commonly occurring brain tumor with a poor prognosis. GBM can develop both “de novo” or evolve from a previous astrocytoma and is characterized by high proliferation and infiltration into the surrounding tissue. Following treatment (surgery, radiotherapy, and chemotherapy), tumors often reappear. Glioma-initiating cells (GICs) have been identified in GBM and are thought to be responsible for tumors initiation, their continued growth, and recurrence. β-catenin, a component of the cell-cell adhesion complex and of the canonical Wnt pathway, regulates proliferation, adhesion, and migration in different cell types. β-catenin and components of the Wnt canonical pathway are commonly overexpressed in GBM. Here, we review previous work on the role of Wnt/β-catenin signalling in glioma initiation, proliferation, and invasion. Understanding the molecular mechanisms regulating GIC biology and glioma progression may help in identifying novel therapeutic targets for GBM treatment.
2234299
Pyruvate Dehydrogenase Kinase as a Potential Therapeutic Target for Malignant Gliomas
Metabolic aberrations in the form of altered flux through key metabolic pathways are the major hallmarks of several life-threatening malignancies including malignant gliomas. These adaptations play an important role in the enhancement of the survival and proliferation of gliomas at the expense of the surrounding normal/healthy tissues. Recent studies in the field of neurooncology have directly targeted the altered metabolic pathways of malignant tumor cells for the development of anti-cancer drugs. Aerobic glycolysis due to elevated production of lactate from pyruvate regardless of oxygen availability is a common metabolic alteration in most malignancies. Aerobic glycolysis offers survival advantages in addition to generating substrates such as fatty acids, amino acids and nucleotides required for the rapid proliferation of cells. This review outlines the role of pyruvate dehydrogenase kinase (PDK) in gliomas as an inhibitor of pyruvate dehydrogenase that catalyzes the oxidative decarboxylation of pyruvate. An in-depth investigation on the key metabolic enzyme PDK may provide a novel therapeutic approach for the treatment of malignant gliomas.
14477577
Wnt/β-Catenin Signaling in Development and Disease
A remarkable interdisciplinary effort has unraveled the WNT (Wingless and INT-1) signal transduction cascade over the last two decades. Wnt genes encode small secreted proteins that are found in all animal genomes. Wnt signaling is involved in virtually every aspect of embryonic development and also controls homeostatic self-renewal in a number of adult tissues. Germline mutations in the Wnt pathway cause several hereditary diseases, and somatic mutations are associated with cancer of the intestine and a variety of other tissues.
37346391
The promise and perils of Wnt signaling through beta-catenin.
Wnt pathways are involved in the control of gene expression, cell behavior, cell adhesion, and cell polarity. In addition, they often operate in combination with other signaling pathways. The Wnt/beta-catenin pathway is the best studied of the Wnt pathways and is highly conserved through evolution. In this pathway, Wnt signaling inhibits the degradation of beta-catenin, which can regulate transcription of a number of genes. Some of the genes regulated are those associated with cancer and other diseases (for example, colorectal cancer and melanomas). As a result, components of the Wnt/beta-catenin pathway are promising targets in the search for therapeutic agents. Information about Wnt pathways is available both in canonical terms and at the species level. In addition to the canonical Wnt/beta-catenin pathway, information is now available for Drosophila, Caenorhabditis elegans, and Xenopus. The STKE Connections Maps for these pathways provide an important tool in accessing this large body of complex information.
669448
Wnt signaling in disease and in development
ABSTRACTThe highly conserved Wnt secreted proteins are critical mediators of cell-to-cell signaling during development of animals. Recent biochemical and genetic analyses have led to significant insight into understanding how Wnt signals work. The catalogue of Wnt signaling components has exploded. We now realize that multiple extracellular, cytoplasmic, and nuclear components modulate Wnt signaling. Moreover, receptor-ligand specificity and multiple feedback loops determine Wnt signaling outputs. It is also clear that Wnt signals are required for adult tissue maintenance. Perturbations in Wnt signaling cause human degenerative diseases as well as cancer.
40792587
The Wnt inhibitory factor 1 (WIF1) is targeted in glioblastoma and has a tumor suppressing function potentially by induction of senescence.
Gene expression-based prediction of genomic copy number aberrations in the chromosomal region 12q13 to 12q15 that is flanked by MDM2 and CDK4 identified Wnt inhibitory factor 1 (WIF1) as a candidate tumor suppressor gene in glioblastoma. WIF1 encodes a secreted Wnt antagonist and was strongly downregulated in most glioblastomas as compared with normal brain, implying deregulation of Wnt signaling, which is associated with cancer. WIF1 silencing was mediated by deletion (7/69, 10%) or epigenetic silencing by promoter hypermethylation (29/110, 26%). Co-amplification of MDM2 and CDK4 that is present in 10% of glioblastomas was associated in most cases with deletion of the whole genomic region enclosed, including the WIF1 locus. This interesting pathogenetic constellation targets the RB and p53 tumor suppressor pathways in tandem, while simultaneously activating oncogenic Wnt signaling. Ectopic expression of WIF1 in glioblastoma cell lines revealed a dose-dependent decrease of Wnt pathway activity. Furthermore, WIF1 expression inhibited cell proliferation in vitro, reduced anchorage-independent growth in soft agar, and completely abolished tumorigenicity in vivo. Interestingly, WIF1 overexpression in glioblastoma cells induced a senescence-like phenotype that was dose dependent. These results provide evidence that WIF1 has tumor suppressing properties. Downregulation of WIF1 in 75% of glioblastomas indicates frequent involvement of aberrant Wnt signaling and, hence, may render glioblastomas sensitive to inhibitors of Wnt signaling, potentially by diverting the tumor cells into a senescence-like state.
13517160
Turcot syndrome (glioma polyposis): a case report.
Turcot's syndrome (glioma-polyposis) is a rare hereditary disorder characterized by association of colonic polyposis with primary tumors of the central nervous system. We report a case of a 27-year-old male diagnosed with Turcot's syndrome after an autopsy. The patient survived for more than two decades after his initial presentation with medulloblastoma at the age of five years. Such a long survival is exceptional in patients with this syndrome. Based on the genetic mutations, the patients with Turcot's syndrome are classified into adenomatous polyposis coli (APC) group or hereditary non-polyposis colon cancer (HNPCC) group. The article highlights the contrasting features of the two groups.
6136692
Wnt inhibitory factor-1 regulates glioblastoma cell cycle and proliferation
Wnt proteins are powerful regulators of cell proliferation and differentiation, and activation of the Wnt signalling pathway is involved in the pathogenesis of several types of human tumours. Wnt inhibitory factor-1 (WIF-1) acts as a Wnt antagonist and tumour suppressor. Previous studies have shown that reducing expression of the WIF-1 gene aberrantly activates Wnt signalling and induces the development of certain types of cancers. In the present study, we examined the expression of WIF-1 in human primary glioblastoma multiforme (GBM) tumours. Studies using semiquantitative reverse transcription-polymerase chain reaction and immunohistochemical analysis revealed that WIF-1 expression is lower in human GBM than in normal brain tissue. To clarify the role of WIF-1, we transfected U251 human glioblastoma-derived cells, which do not express WIF-1, with the pcDNA3.1-WIF1 vector to restore WIF-1 expression. The results of cell proliferation, colony formation and apoptosis assays, as well as flow cytometry, indicate that exogenous WIF-1 has no effect on U251 cell apoptosis, but does arrest cells at the G(0)/G(1) phase and inhibit cell growth. Collectively, our data suggest that WIF-1 is a potent inhibitor of GBM growth.
7166440
Downregulation of WIF-1 by hypermethylation in astrocytomas.
Wnt inhibitory factor-1 (WIF-1) acts as a Wnt antagonist and tumor suppressor, but hypermethylation of WIF-1 gene promoter and low expression of WIF-1 activate Wnt signaling aberrantly and induce the development of several human tumors. By using RT-PCR, immunohistochemistry and methylation-specific PCR, we analyzed the expression and methylation of WIF-1 in 4 normal brain tissues, 35 freshly resected astrocytoma tissues and 4 glioblastoma-derived cell lines. Significant downregulation of WIF-1 mRNA and protein expression levels was observed in astrocytoma tissues compared with normal brain tissues. Significant association between WIF-1 downregulation and pathological grade of astrocytomas was found. WIF-1 gene aberrant methylation was observed in 19 of 35 (54.29%) tumor samples. The promoter methylation tumors showed low WIF-1 protein and mRNA expression, whereas the promoter unmethylation tumors displayed high protein and mRNA expression levels. Moreover, complete absence of WIF-1 mRNA expression was observed in four cell lines, whereas treatment with demethylating agent, 5-aza-2'-deoxycytidine, restored WIF-1 expression. Our results suggested that the WIF-1 gene is frequently silenced in astrocytoma by aberrant promoter methylation. This may be an important mechanism in astrocytoma carcinogenesis.
30344019
Functional interaction between peroxisome proliferator-activated receptor gamma and beta-catenin.
Studies have demonstrated cross talk between beta-catenin and peroxisome proliferator-activated receptor gamma (PPARgamma) signaling pathways. Specifically, activation of PPARgamma induces the proteasomal degradation of beta-catenin in cells that express an adenomatous polyposis coli-containing destruction complex. In contrast, oncogenic beta-catenin is resistant to such degradation and inhibits the expression of PPARgamma target genes. In the present studies, we demonstrate a functional interaction between beta-catenin and PPARgamma that involves the T-cell factor (TCF)/lymphocyte enhancer factor (LEF) binding domain of beta-catenin and a catenin binding domain (CBD) within PPARgamma. Mutation of K312 and K435 in the TCF/LEF binding domain of an oncogenic beta-catenin (S37A) significantly reduces its ability to interact with and inhibit the activity of PPARgamma. Furthermore, these mutations render S37A beta-catenin susceptible to proteasomal degradation in response to activation of PPARgamma. Mutation of F372 within the CBD (helices 7 and 8) of PPARgamma disrupts its binding to beta-catenin and significantly reduces the ability of PPARgamma to induce the proteasomal degradation of beta-catenin. We suggest that in normal cells, PPARgamma can function to suppress tumorigenesis and/or Wnt signaling by targeting phosphorylated beta-catenin to the proteasome through a process involving its CBD. In contrast, oncogenic beta-catenin resists proteasomal degradation by inhibiting PPARgamma activity, which requires its TCF/LEF binding domain.
25054872
Peroxisome-proliferator-activated receptor gamma suppresses Wnt/beta-catenin signalling during adipogenesis.
The Wnt/beta-catenin signalling pathway appears to operate to maintain the undifferentiated state of preadipocytes by inhibiting adipogenic gene expression. To define the mechanisms regulating suppression of Wnt/beta-catenin signalling, we analysed the beta-catenin expression in response to activation of transcription factors that regulate adipogenesis. The results show an extensive down-regulation of nuclear beta-catenin that occurs during the first few days of differentiation of 3T3-L1 preadipocytes and coincides with the induction of the adipogenic transcription factors, C/EBPbeta (CCAAT-enhancer-binding protein) and PPARgamma (peroxisome-proliferator-activated receptor). To assess the role of each of these factors in this process, we conditionally overexpressed C/EBPbeta in Swiss mouse fibroblasts using the TET-off system. Abundant expression of C/EBPbeta alone had minimal effect on beta-catenin expression, whereas expression of C/EBPbeta, in the presence of dexamethasone, induced PPARgamma expression and caused a measurable decrease in beta-catenin. In addition, exposure of cells expressing both C/EBPbeta and PPARgamma to a potent PPARgamma ligand resulted in an even greater decrease in beta-catenin by mechanisms that involve the proteasome. Our studies also suggest a reciprocal relationship between PPARgamma activity and beta-catenin expression, since ectopic production of Wnt-1 in preadipocytes blocked the induction of PPARgamma gene expression. Moreover, by suppressing beta-catenin expression, ectopic expression of PPARgamma in Wnt-1-expressing preadipocytes rescued the block in adipogenesis after their exposure to the PPARgamma ligand, troglitazone.
24411854
Peroxisome proliferator-activated receptor gamma activation can regulate beta-catenin levels via a proteasome-mediated and adenomatous polyposis coli-independent pathway.
The transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma) belongs to the family of nuclear hormone receptors and consists of two isotypes, PPARgamma1 and PPARgamma2. Our earlier studies have shown that troglitazone (TZD)-mediated activation of PPARgamma2 in hepatocytes inhibits growth and attenuates cyclin D1 transcription via modulating CREB levels. Because this process of growth inhibition was also associated with an inhibition of beta-catenin expression at a post-translational level, our aim was to elucidate the mechanism involved. beta-Catenin is a multifunctional protein, which can regulate cell-cell adhesion by interacting with E-cadherin and other cellular processes via regulating target gene transcription in association with TCF/LEF transcription factors. Two adenomatous polyposis coli (APC)-dependent proteasomal degradation pathways, one involving glycogen synthase kinase 3beta (GSK3beta) and the other involving p53-Siah-1, degrade excess beta-catenin in normal cells. Our immunofluorescence and Western blot studies indicated a TZD-dependent decrease in cytoplasmic and membrane-bound beta-catenin, indicating no increase in its membrane translocation. This was associated with a reduction in E-cadherin expression. PPARgamma2 activation inhibited GSK3beta kinase activity, and pharmacological inhibition of GSK3beta activity was unable to restore beta-catenin expression following PPARgamma2 activation. Additionally, this beta-catenin degradation pathway was operative in cells, with inactivating mutations of both APC and p53. Inhibition of the proteasomal pathway inhibited PPARgamma2-mediated degradation of beta-catenin, and incubation with TZD increased ubiquitination of beta-catenin. We conclude that PPARgamma2-mediated suppression of beta-catenin levels involves a novel APC/GSK3beta/p53-independent ubiquitination-mediated proteasomal degradation pathway.
24111328
Wnt signaling and forebrain development.
Components of the Wnt signaling pathway are expressed in a tightly regulated and spatially specific manner during development of the forebrain, and Wnts are key regulators of regional forebrain identity. Wnt signaling from the cortical hem regulates the expansion and cell-type specification of the adjacent neuroepithelium and, in conjunction with Bmp, Fgf, and Shh signaling, controls dorsal-ventral forebrain patterning. Subsequently, Wnt signaling dynamically regulates the behavior of cortical progenitor cells, initially promoting the expansion of radial glia progenitor cells and later inducing neurogenesis by promoting terminal differentiation of intermediate progenitor cells. A role for Wnt signaling in cell-type specification has also been proposed.
24480929
Wnt signaling: multiple functions in neural development
Abstract.Wnt signaling has proven to be essential for neural development at various stages and across species. Wnts are involved in morphogenesis and patterning, and their proliferation-promoting role is a key function in stem cell maintenance and the expansion of progenitor pools. Moreover, Wnt signaling is involved in differentiation processes and lineage decision events during both central and peripheral nervous system development. Additionally, several reports point to a role of Wnt signaling in axon guidance and neurite outgrowth. This article reviews and consolidates the existing evidence for the functions of Wnt signaling in neural development.
14838107
Wnts in adult brain: from synaptic plasticity to cognitive deficiencies
During development of the central nervous system the Wnt signaling pathway has been implicated in a wide spectrum of physiological processes, including neuronal connectivity and synapse formation. Wnt proteins and components of the Wnt pathway are expressed in the brain since early development to the adult life, however, little is known about its role in mature synapses. Here, we review evidences indicating that Wnt proteins participate in the remodeling of pre- and post-synaptic regions, thus modulating synaptic function. We include the most recent data in the literature showing that Wnts are constantly released in the brain to maintain the basal neural activity. Also, we review the evidences that involve components of the Wnt pathway in the development of neurological and mental disorders, including a special emphasis on in vivo studies that relate behavioral abnormalities to deficiencies in Wnt signaling. Finally, we include the evidences that support a neuroprotective role of Wnt proteins in Alzheimer’s disease. We postulate that deregulation in Wnt signaling might have a fundamental role in the origin of neurological diseases, by altering the synaptic function at stages where the phenotype is not yet established but when the cognitive decline starts.
8743917
Wnt signaling in the vertebrate central nervous system: from axon guidance to synaptic function.
Regulation of cell signaling by Wnt proteins is critical for the formation of neuronal circuits. Wnts modulate axon pathfinding, dendritic development, and synaptic assembly. Through different receptors, Wnts activate diverse signaling pathways that lead to local changes on the cytoskeleton or global cellular changes involving nuclear function. Recently, a link between neuronal activity, essential for the formation and refinement of neuronal connections, and Wnt signaling has been uncovered. Indeed, neuronal activity regulates the release of Wnt and the localization of their receptors. Wnts mediate synaptic structural changes induced by neuronal activity or experience. New emerging evidence suggests that dysfunction in Wnt signaling contributes to neurological disorders. In this article, the attention is focused on the function of Wnt signaling in the formation of neuronal circuits in the vertebrate central nervous system.
3195846
Wnt/β-catenin and its Diverse Physiological Cell Signaling Pathways in Neurodegenerative and Neuropsychiatric Disorders
Wnt signaling is a fundamental pathway in embryogenesis which is evolutionary conserved from metazoans to humans. Much of our understanding of Wnt signaling events emerged from key developmental studies in drosophila, zebra fish, xenopus, and mice. Considerable data now exists on the role of Wnt signaling beyond these developmental processes and in particular its role in health and disease. The focus of this special issue is on Wnt/β-catenin and its diverse physiological cell signaling pathways in neurodegenerative and neuropsychiatric disorders. This special issue is composed of six reviews and two original articles selected to highlight recent advances in the role of Wnt signaling in CNS embryonic development, in adult brain function, in neurodegenerative conditions such as Alzheimer’s disease, schizophrenia, NeuroAIDS, and in gliomas. The finding that β-catenin can translocate to the nucleus where it binds to TCF/LEF transcription factors to regulate target gene expression was a seminal observation that linked β-catenin/LEF to T cell development and differentiation. We also provide a nostalgic look on recent advances in role of Wnts in T cell development and maturation. These reviews highlight the extensive body of work in these thematic areas as well as identify knowledge gaps, where appropriate. Understanding Wnt function under healthy and diseased conditions may provide a therapeutic resource, albeit it a challenging one, in diseases where dysfunctional and/or diminished Wnt signaling is a prominent player in the disease process.
13920198
Wnt your brain be inflamed? Yes, it Wnt!
The roles of Wnts in neural development, synaptogenesis, and cancer are generally well characterized. Nonetheless, evidence exists that interactions between the immune and nervous systems control major brain regenerative processes ranging from physiological or pathological (reparative) regeneration to neurogenesis and synaptic plasticity. Recent studies describe deregulated Wnt-Fzd signaling in degenerative and inflammatory central nervous system (CNS) disorders, and the expression of Wnt signaling components in the immune system, and in immune-like cells of the mammalian CNS. This would suggest a likely involvement of Wnts in inflammation-driven brain damage and inflammation-directed brain repair. Here, we review how Wnts modulate neuroimmune interactions and offer a perspective on the most challenging therapeutic opportunities for those CNS diseases where injury-reactive Wnt-flavored inflammation precedes secondary neurodegeneration.
25504472
Functional Characterization of WNT7A Signaling in PC12 Cells
WNT factors represent key mediators of many processes in animal development and homeostasis and act through a receptor complex comprised of members of the Frizzled and low density lipoprotein-related receptors (LRP). In mammals, 19 genes encoding Wingless and Int-related factor (WNTs), 10 encoding Frizzled, and 2 encoding LRP proteins have been identified, but little is known of the identities of individual Frizzled-LRP combinations mediating the effects of specific WNT factors. Additionally, several secreted modulators of WNT signaling have been identified, including at least three members of the Dickkopf family. WNT7A is a WNT family member expressed in the vertebrate central nervous system capable of modulating aspects of neuronal plasticity. Gene knock-out models in the mouse have revealed that WNT7A plays a role in cerebellar maturation, although its function in the development of distal limb structures and of the reproductive tract have been more intensely studied. To identify a receptor complex for this WNT family member, we have analyzed the response of the rat pheochromocytoma cell line PC12 to WNT7A. We find that PC12 cells are capable of responding to WNT7A as measured by increased β-catenin stability and activation of a T-cell factor-based luciferase reporter construct and that these cells express three members of the Frizzled family (Frizzled-2, -5, and -7) and LRP6. Our functional analysis indicates that WNT7A can specifically act via a Frizzled-5·LRP6 receptor complex in PC12 cells and that this activity can be antagonized by Dickkopf-1 and Dickkopf-3.
24099578
DKK1 Antagonizes Wnt Signaling without Promotion of LRP6 Internalization and Degradation*
DKK1 is a secreted protein that antagonizes Wnt signaling and plays essential roles in vertebrate embryogenesis including head induction, skeletal development, and limb patterning. DKK1 is also implicated in osteoporosis, arthritis, and cancer and represents a potential therapeutic target for the treatment of these diseases. DKK1 is a high affinity antagonistic ligand for LRP6, which is a Wnt coreceptor that acts together with the Frizzled serpentine receptor to initiate Wnt signal transduction. Two different models have been proposed to account for the mechanism by which DKK1 antagonizes LRP6 function. One model suggests that DKK1 binding to LRP6 disrupts Wnt-induced Frizzled-LRP6 complex formation, whereas the other model proposes that DKK1 interaction with LRP6 promotes LRP6 internalization and degradation, thereby reducing the cell surface LRP6 level. To clarify the molecular basis of DKK1 action, we examined how DKK1 affects the endogenous LRP6 in several mammalian cell lines including mouse embryonic fibroblasts. Here we show that DKK1 inhibits Wnt signaling but induces neither LRP6 down-regulation from the cell surface nor reduction of total LRP6 protein level and that DKK1 has no effect on the rate of continuous internalization of LRP6 and the half-life (about 4.7 h) of LRP6. We conclude that DKK1 inhibition of LRP6 is independent of LRP6 internalization and degradation.
13935650
Secreted antagonists of the Wnt signalling pathway
The extracellular antagonists of the Wnt signalling pathway can be divided into two broad classes. Both classes of molecule prevent ligand-receptor interactions, but by different mechanisms: members of the first class, which include the sFRP (secreted Frizzled-related protein) family, WIF (Wnt inhibitory factor)-1 and Cerberus, primarily bind to Wnt proteins; the second class comprises certain members of the Dickkopf (Dkk) family, which bind to one subunit of the Wnt receptor complex. In addition, there are other protein interactions that contribute to Wnt antagonist function. Moreover, certain sFRPs and Dkks do not antagonise Wnt function, which suggests that these families have as-yet-undiscovered functions.
9300321
DKK1, a negative regulator of Wnt signaling, is a target of the β-catenin/TCF pathway
Wnt signaling plays an important role in embryonic development and tumorigenesis. These biological effects are exerted by activation of the β-catenin/TCF transcription complex and consequent regulation of a set of downstream genes. TCF-binding elements have been found in the promoter regions of many TCF target genes and characterized by a highly conserved consensus sequence. Utilizing this consensus sequence, we performed an in silico screening for new TCF target genes. Through computational screening and subsequent experimental analysis, we identified a novel TCF target gene, DKK1, which has been shown to be a potent inhibitor of Wnt signaling. Our finding suggests the existence of a novel feedback loop in Wnt signaling.
7459170
Beyond Wnt inhibition: new functions of secreted Frizzled-related proteins in development and disease
The secreted Frizzled-related proteins (SFRPs) are a family of soluble proteins that are structurally related to Frizzled (Fz) proteins, the serpentine receptors that mediate the extensively used cell-cell communication pathway involving Wnt signalling. Because of their homology with the Wnt-binding domain on the Fz receptors, SFRPs were immediately characterised as antagonists that bind to Wnt proteins to prevent signal activation. Since these initial studies, interest in the family of SFRPs has grown progressively, offering new perspectives on their function and mechanism of action in both development and disease. These studies indicate that SFRPs are not merely Wnt-binding proteins, but can also antagonise one another's activity, bind to Fz receptors and influence axon guidance, interfere with BMP signalling by acting as proteinase inhibitors, and interact with other receptors or matrix molecules. Furthermore, their expression is altered in different types of cancers, bone pathologies, retinal degeneration and hypophosphatemic diseases, indicating that their activity is fundamental for tissue homeostasis. Here we review some of the debated aspects of SFRP-Wnt interactions and discuss the new and emerging roles of SFRPs.
9561740
β‐catenin is a target for the ubiquitin–proteasome pathway
β‐catenin is a central component of the cadherin cell adhesion complex and plays an essential role in the Wingless/Wnt signaling pathway. In the current model of this pathway, the amount of β‐catenin (or its invertebrate homolog Armadillo) is tightly regulated and its steady‐state level outside the cadherin–catenin complex is low in the absence of Wingless/Wnt signal. Here we show that the ubiquitin‐dependent proteolysis system is involved in the regulation of β‐catenin turnover. β‐catenin, but not E‐cadherin, p120cas or α‐catenin, becomes stabilized when proteasome‐mediated proteolysis is inhibited and this leads to the accumulation of multi‐ubiquitinated forms of β‐catenin. Mutagenesis experiments demonstrate that substitution of the serine residues in the glycogen synthase kinase 3β (GSK3β) phosphorylation consensus motif of β‐catenin inhibits ubiquitination and results in stabilization of the protein. This motif in β‐catenin resembles a motif in IκB (inhibitor of NFκB) which is required for the phosphorylation‐dependent degradation of IκB via the ubiquitin–proteasome pathway. We show that ubiquitination of β‐catenin is greatly reduced in Wnt‐expressing cells, providing the first evidence that the ubiquitin–proteasome degradation pathway may act downstream of GSK3β in the regulation of β‐catenin.
15856518
The JNK- and AKT/GSK3β- Signaling Pathways Converge to Regulate Puma Induction and Neuronal Apoptosis Induced by Trophic Factor Deprivation
The AKT, GSK3 and JNK family kinases have been implicated in neuronal apoptosis associated with neuronal development and several neurodegenerative conditions. However, the mechanisms by which these kinase pathways regulate apoptosis remain unclear. In this study we have investigated the role of these kinases in neuronal cell death using an established model of trophic factor deprivation induced apoptosis in cerebellar granule neurons. BCL-2 family proteins are known to be central regulators of apoptosis and we have determined that the pro-apoptotic family member Puma is transcriptionally up-regulated in trophic factor deprived neurons and that Puma induction is required for apoptosis in vitro and in vivo. Importantly, we demonstrate that Puma induction is dependent on both JNK activation and AKT inactivation. AKT is known to regulate a number of downstream pathways, however we have determined that PI3K-AKT inactivation induces Puma expression through a GSK3β-dependent mechanism. Finally we demonstrate that the JNK and AKT/GSK3β pathways converge to regulate FoxO3a-mediated transcriptional activation of Puma. In summary we have identified a novel and critical link between the AKT, GSK3β and JNK kinases and the regulation of Puma induction and suggest that this may be pivotal to the regulation of neuronal apoptosis in neurodegenerative conditions.
13449245
GSK3 signalling in neural development
Recent evidence suggests that glycogen synthase kinase 3 (GSK3) proteins and their upstream and downstream regulators have key roles in many fundamental processes during neurodevelopment. Disruption of GSK3 signalling adversely affects brain development and is associated with several neurodevelopmental disorders. Here, we discuss the mechanisms by which GSK3 activity is regulated in the nervous system and provide an overview of the recent advances in the understanding of how GSK3 signalling controls neurogenesis, neuronal polarization and axon growth during brain development. These recent advances suggest that GSK3 is a crucial node that mediates various cellular processes that are controlled by multiple signalling molecules — for example, disrupted in schizophrenia 1 (DISC1), partitioning defective homologue 3 (PAR3), PAR6 and Wnt proteins — that regulate neurodevelopment.
33010159
GSK3: a multifaceted kinase in Wnt signaling.
GSK3 is one of the few signaling mediators that play central roles in a diverse range of signaling pathways, including those activated by Wnts, hedgehog, growth factors, cytokines, and G protein-coupled ligands. Although the inhibition of GSK3-mediated beta-catenin phosphorylation is known to be the key event in Wnt-beta-catenin signaling, the mechanisms that underlie this event remain incompletely understood. The recent demonstration of GSK3 involvement in Wnt receptor phosphorylation illustrates the multifaceted roles that GSK3 plays in Wnt-beta-catenin signaling. In this review, we will summarize these recent results and offer explanations, hypotheses, and models to reconcile some of these observations.
20847300
Mechanisms regulating glioma invasion.
Glioblastoma (GBM) is the most aggressive, deadliest, and most common brain malignancy in adults. Despite the advances made in surgical techniques, radiotherapy and chemotherapy, the median survival for GBM patients has remained at a mere 14 months. GBM poses several unique challenges to currently available treatments for the disease. For example, GBM cells have the propensity to aggressively infiltrate/invade into the normal brain tissues and along the vascular tracks, which prevents complete resection of all malignant cells and limits the effect of localized radiotherapy while sparing normal tissue. Although anti-angiogenic treatment exerts anti-edematic effect in GBM, unfortunately, tumors progress with acquired increased invasiveness. Therefore, it is an important task to gain a deeper understanding of the intrinsic and post-treatment invasive phenotypes of GBM in hopes that the gained knowledge would lead to novel GBM treatments that are more effective and less toxic. This review will give an overview of some of the signaling pathways that have been shown to positively and negatively regulate GBM invasion, including, the PI3K/Akt, Wnt, sonic hedgehog-GLI1, and microRNAs. The review will also discuss several approaches to cancer therapies potentially altering GBM invasiveness.
12632351
PPAR Regulation of Inflammatory Signaling in CNS Diseases
Central nervous system (CNS) is an immune privileged site, nevertheless inflammation associates with many CNS diseases. Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear hormone receptors that regulate immune and inflammatory responses. Specific ligands for PPARα, γ, and δ isoforms have proven effective in the animal models of multiple sclerosis (MS), Alzheimer's disease, Parkinson's disease, and trauma/stroke, suggesting their use in the treatment of neuroinflammatory diseases. The activation of NF-κB and Jak-Stat signaling pathways and secretion of inflammatory cytokines are critical in the pathogenesis of CNS diseases. Interestingly, PPAR agonists mitigate CNS disease by modulating inflammatory signaling network in immune cells. In this manuscript, we review the current knowledge on how PPARs regulate neuroinflammatory signaling networks in CNS diseases.
21812924
Differential expression of peroxisome proliferator-activated receptors (PPARs): tissue distribution of PPAR-alpha, -beta, and -gamma in the adult rat.
Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily that can be activated by various xenobiotics and natural fatty acids. These transcription factors primarily regulate genes involved in lipid metabolism and also play a role in adipocyte differentiation. We present the expression patterns of the PPAR subtypes in the adult rat, determined by in situ hybridization using specific probes for PPAR-alpha, -beta and -gamma, and by immunohistochemistry using a polyclonal antibody that recognizes the three rat PPAR subtypes. In numerous cell types from either ectodermal, mesodermal, or endodermal origin, PPARs are coexpressed, with relative levels varying between them from one cell type to the other. PPAR-alpha is highly expressed in hepatocytes, cardiomyocytes, enterocytes, and the proximal tubule cells of kidney. PPAR-beta is expressed ubiquitously and often at higher levels than PPAR-alpha and -gamma. PPAR-gamma is expressed predominantly in adipose tissue and the immune system. Our results suggest new potential directions to investigate the functions of the different PPAR subtypes.
38820927
Peroxisome proliferator-activated receptor gamma in diabetes and metabolism.
The peroxisome proliferator-activated receptor gamma (PPAR-gamma) has been the focus of intense research during the past decade because ligands for this receptor have emerged as potent insulin sensitizers used in the treatment of type 2 diabetes. Recent advances include the discovery of novel genes that are regulated by PPAR-gamma, which helps explain how activation of this adipocyte-predominant transcription factor regulates glucose and lipid homeostasis. Increased levels of circulating free fatty acids and lipid accumulation in non-adipose tissue have been implicated in the development of insulin resistance. This situation is improved by PPAR-gamma ligands, which promote fatty acid storage in fat depots and regulate the expression of adipocyte-secreted hormones that impact on glucose homeostasis. The net result of the pleiotropic effects of PPAR-gamma ligands is improvement of insulin sensitivity, although undesired side-effects limit the utility of this therapy. It might be possible to dissociate the anti-diabetic and adverse effects through selective modulation of PPAR-gamma activity.
44539527
PPAR(gamma) and glucose homeostasis.
Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor involved in the control of metabolism. Research on PPARgamma is oriented towards understanding its role in insulin sensitization, which was inspired by the discovery that antidiabetic agents, the thiazolidinediones, were agonists for PPARgamma. PPARgamma stimulation improves glucose tolerance and insulin sensitivity in type 2 diabetic patients and in animal models of insulin resistance through mechanisms that are incompletely understood. Upon activation, PPARgamma heterodimerizes with retinoid X receptor, recruits specific cofactors, and binds to responsive DNA elements, thereby stimulating the transcription of target genes. Because PPARgamma is highly enriched in adipose tissue and because of its major role in adipocyte differentiation, it is thought that the effects of PPARgamma in adipose tissue are crucial to explain its role in insulin sensitization, but recent studies have highlighted the contribution of other tissues as well. Although relatively potent for their insulin-sensitizing action, currently marketed PPARgamma activators have some important undesirable side effects. These concerns led to the discovery of new ligands with potent antidiabetic properties but devoid of certain of these side effects. Data from human genetic studies and from PPARgamma heterozygous knockout mice indicate that a reduction in PPARgamma activity could paradoxically improve insulin sensitivity. These findings suggest that modulation of PPARgamma activity by partial agonists or compounds that affect cofactor recruitment might hold promise for the treatment of insulin resistance.
7228505
PPARs, Cardiovascular Metabolism, and Function: Near- or Far-from-Equilibrium Pathways
Peroxisome proliferator-activated receptors (PPAR α, β/δ and γ) play a key role in metabolic regulatory processes and gene regulation of cellular metabolism, particularly in the cardiovascular system. Moreover, PPARs have various extra metabolic roles, in circadian rhythms, inflammation and oxidative stress. In this review, we focus mainly on the effects of PPARs on some thermodynamic processes, which can behave either near equilibrium, or far-from-equilibrium. New functions of PPARs are reported in the arrhythmogenic right ventricular cardiomyopathy, a human genetic heart disease. It is now possible to link the genetic desmosomal abnormalitiy to the presence of fat in the right ventricle, partly due to an overexpression of PPARγ. Moreover, PPARs are directly or indirectly involved in cellular oscillatory processes such as the Wnt-b-catenin pathway, circadian rhythms of arterial blood pressure and cardiac frequency and glycolysis metabolic pathway. Dysfunction of clock genes and PPARγ may lead to hyperphagia, obesity, metabolic syndrome, myocardial infarction and sudden cardiac death, In pathological conditions, regulatory processes of the cardiovascular system may bifurcate towards new states, such as those encountered in hypertension, type 2 diabetes, and heart failure. Numerous of these oscillatory mechanisms, organized in time and space, behave far from equilibrium and are “dissipative structures”.
13794944
Vascular PPARgamma controls circadian variation in blood pressure and heart rate through Bmal1.
Thiazolidinediones (TZDs) are PPARgamma activators that exhibit vasculoprotective properties. To determine the vascular function of PPARgamma, we analyzed Tie2Cre/flox and SM22Cre/flox mice. Unexpectedly, both knockout strains exhibited a significant reduction of circadian variations in blood pressure and heart rate in parallel with diminished variations in urinary norepinephrine/epinephrine excretion and impaired rhythmicity of the canonical clock genes, including Bmal1. PPARgamma expression in the aorta exhibited a robust rhythmicity with a more than 20-fold change during the light/dark cycle. Rosiglitazone treatment induced aortic expression of Bmal1 mRNA, and ChIP and promoter assays revealed that Bmal1 is a direct PPARgamma target gene. These studies have uncovered a role for vascular PPARgamma as a peripheral factor participating in regulation of cardiovascular rhythms.
39979939
PPARs and molecular mechanisms of transrepression.
In the last few years, PPARs have emerged as key regulators of inflammatory and immune responses. However, the mechanistic basis of the anti-inflammatory effects of peroxisome proliferator-activated receptors (PPARs) remains poorly understood. Accumulating evidence suggests that these effects result from inhibition of signal-dependent transcription factors that mediate inflammatory programs of gene activation. Several mechanisms underlying negative regulation of gene expression by PPARs have been described. Recent studies, using siRNA, microarray analysis and macrophage-specific knockout mice, have highlighted PPARs molecular transrepression mechanism in macrophages. Identification of their mechanism of action should help promote the understanding of the physiologic roles that PPARs play in immunity and contribute to the development of new therapeutic agents.
22974645
Suppression of canonical Wnt/beta-catenin signaling by nuclear plakoglobin recapitulates phenotype of arrhythmogenic right ventricular cardiomyopathy.
Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC) is a genetic disease caused by mutations in desmosomal proteins. The phenotypic hallmark of ARVC is fibroadipocytic replacement of cardiac myocytes, which is a unique phenotype with a yet-to-be-defined molecular mechanism. We established atrial myocyte cell lines expressing siRNA against desmoplakin (DP), responsible for human ARVC. We show suppression of DP expression leads to nuclear localization of the desmosomal protein plakoglobin and a 2-fold reduction in canonical Wnt/beta-catenin signaling through Tcf/Lef1 transcription factors. The ensuing phenotype is increased expression of adipogenic and fibrogenic genes and accumulation of fat droplets. We further show that cardiac-restricted deletion of Dsp, encoding DP, impairs cardiac morphogenesis and leads to high embryonic lethality in the homozygous state. Heterozygous DP-deficient mice exhibited excess adipocytes and fibrosis in the myocardium, increased myocyte apoptosis, cardiac dysfunction, and ventricular arrhythmias, thus recapitulating the phenotype of human ARVC. We believe our results provide for a novel molecular mechanism for the pathogenesis of ARVC and establish cardiac-restricted DP-deficient mice as a model for human ARVC. These findings could provide for the opportunity to identify new diagnostic markers and therapeutic targets in patients with ARVC.
44608772
The Wnt/beta-catenin signaling pathway targets PPARgamma activity in colon cancer cells.
Control of colon cell fate in adenocarcinomas is disrupted, in part, due to aberrant Wnt/beta-catenin signaling. The nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) has been implicated in the development of colon cancers. In the adenomatous polyposis coli multiple intestinal neoplasia (APCMin) mouse cancer model, PPARgamma expression in the colonic mucosa is markedly altered. In addition, PPARgamma protein levels are elevated, possibly through sequestration by activated beta-catenin in colon cancer cell lines. Induction of the Wnt/beta-catenin pathway by LiCl also elevated PPARgamma levels and induced PPARgamma-dependent reporter and endogenous target genes. Mechanistically, PPARgamma, through interactions with beta-catenin and T cell transcription factor (Tcf)-4, may be a determinant of cell fate and is likely a target of the Wnt pathway in cancer cells.
32318159
Gene expression profile of adipocyte differentiation and its regulation by peroxisome proliferator-activated receptor-gamma agonists.
PPAR gamma is an adipocyte-specific nuclear hormone receptor. Agonists of PPAR gamma, such as thiazolidinediones (TZDs), promote adipocyte differentiation and have insulin-sensitizing effects in animals and diabetic patients. Affymetrix oligonucleotide arrays representing 6347 genes were employed to profile the gene expression responses of mature 3T3-L1 adipocytes and differentiating preadipocytes to a TZD PPAR gamma agonist in vitro. The expression of 579 genes was significantly up- or down-regulated by more than 1.5-fold during differentiation and/or by treatment with TZD, and these genes were organized into 32 clusters that demonstrated concerted changes in expression of genes controlling cell growth or lipid metabolism. Quantitative PCR was employed to further characterize gene expression and led to the identification of beta-catenin as a new PPAR gamma target gene. Both mRNA and protein levels for beta-catenin were down-regulated in 3T3-L1 adipocytes compared with fibroblasts and were further decreased by treatment of adipocytes with PPAR gamma agonists. Treatment of db/db mice with a PPAR gamma agonist also resulted in reduction of beta-catenin mRNA levels in adipose tissue. These results suggest that beta-catenin plays an important role in the regulation of adipogenesis. Thus, the transcriptional patterns revealed in this study further the understanding of adipogenesis process and the function of PPAR gamma activation.
20540231
Thermodynamic Aspects and Reprogramming Cellular Energy Metabolism during the Fibrosis Process
Fibrosis is characterized by fibroblast proliferation and fibroblast differentiation into myofibroblasts, which generate a relaxation-free contraction mechanism associated with excessive collagen synthesis in the extracellular matrix, which promotes irreversible tissue retraction evolving towards fibrosis. From a thermodynamic point of view, the mechanisms leading to fibrosis are irreversible processes that can occur through changing the entropy production rate. The thermodynamic behaviors of metabolic enzymes involved in fibrosis are modified by the dysregulation of both transforming growth factor β (TGF-β) signaling and the canonical WNT/β-catenin pathway, leading to aerobic glycolysis, called the Warburg effect. Molecular signaling pathways leading to fibrosis are considered dissipative structures that exchange energy or matter with their environment far from the thermodynamic equilibrium. The myofibroblastic cells arise from exergonic processes by switching the core metabolism from oxidative phosphorylation to glycolysis, which generates energy and reprograms cellular energy metabolism to induce the process of myofibroblast differentiation. Circadian rhythms are far-from-equilibrium thermodynamic processes. They directly participate in regulating the TGF-β and WNT/β-catenin pathways involved in energetic dysregulation and enabling fibrosis. The present review focusses on the thermodynamic implications of the reprogramming of cellular energy metabolism, leading to fibroblast differentiation into myofibroblasts through the positive interplay between TGF-β and WNT/β-catenin pathways underlying in fibrosis.
42712152
The Myofibroblast: TGFβ-1, A Conductor which Plays a Key Role in Fibrosis by Regulating the Balance between PPARγ and the Canonical WNT Pathway
Myofibroblasts are non-muscular contractile cells that occur physiologically in organs such as in stem villi of the human placenta during normal pregnancies. They have the ability to contract and relax in response to changes in the volume of the intervillous chamber. Myofibroblasts are also found in many pathological states, and are involved in wound healing and fibrosis processes in several organs such as liver, lung, kidney, and heart. During fibrosis, the contractile phenomenon is a relaxation-free mechanism, associated with the synthesis of collagen in the extracellular matrix (ECM), which leads to irreversible fibrosis, tissue retraction and finally apoptosis of the myofibroblasts. The molecular motor of myofibroblasts is the non-muscle myosin type II (NMII). Differentiation of fibroblasts into myofibroblast is largely regulated by the Transforming Growth Factor-β1 (TGF-β1). This system regulates the canonical WNT/β-catenin pathway in a positive manner and PPARγ in a negative manner. WNT/β-catenin promotes fibrosis while PPARγ prevents fibrosis. This review focuses on the contractile properties of myofibroblasts and on the TGF-β1 conductor which regulates the antagonism between PPARγ and the canonical WNT/β-catenin pathway.
18512446
A potential link between peroxisome proliferator-activated receptor signalling and the pathogenesis of arrhythmogenic right ventricular cardiomyopathy.
AIMS
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is characterized by major fibro-fatty replacement of the right ventricle (RV). We hypothesized that changes in peroxisome proliferator-activated receptor (PPAR) signalling contributed to myocardium fatty accumulation and contractile dysfunction in ARVC.


METHODS AND RESULTS
Real-time quantitative reverse transcriptase-polymerase chain reaction and western blotting were used to assess cardiac expression of PPARalpha and gamma and two of their downstream target genes--medium-chain acyl-CoA dehydrogenase (MCAD) and phosphoenolpyruvate carboxykinase (PEPCK)--in both RV and left ventricle (LV) from five controls and five ARVC patients. In vitro motility assays were used to analyse functional properties of myosin. In the RV, sliding velocity was nearly two-fold lower in ARVC than in controls, whereas a 10% reduction in velocity values was noted between ARVC and non-failing myocardium in the LV. In controls, PPARalpha and MCAD mRNA and protein levels were higher in the RV compared with the LV. In ARVC, the expression of PPARalpha and MCAD mRNA and/or proteins was decreased in both RV and LV. RV from ARVC was also characterized by a dramatic activation of the PPARgamma pathway, as attested by the increase in PPARgamma mRNA and protein (500 and 270%, respectively, each P < 0.001) and by the induction of PEPCK gene. In contrast, the LV of ARVC heart exhibited no changes in the expression of the PPARgamma regulatory pathway compared with control.


CONCLUSION
ARVC is associated with major disturbances in the PPARalpha and PPARgamma signalling pathway in the RV that may contribute to intracellular lipid overload and severe myosin dysfunction.
2277031
Differential molecular interactions of beta-catenin and plakoglobin in adhesion, signaling and cancer.
Plakoglobin and beta-catenin are homologous proteins functioning in cell adhesion and transactivation. Their activities are controlled by three types of interactions: those with cadherins in adherens junctions, linking them to the actin cytoskeleton; interactions in the nucleus, where they bind to transcription factors and stimulate gene expression; interactions of free cytoplasmic beta-catenin with axin and adenomatous polyposis coli (APC) protein which target it for degradation. Studies in the past year have demonstrated the complex interplay between these three types of interactions and the different behavior of beta-catenin and plakoglobin in their involvement in morphogenesis and tumorigenesis strongly suggesting that catenins play key roles in adhesion-mediated signaling.
43456478
Differential Mechanisms of LEF/TCF Family-Dependent Transcriptional Activation by β-Catenin and Plakoglobin
ABSTRACT β-Catenin and plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. β-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous β-catenin. We show here, by DNA mobility shift analysis, that the formation of a plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing β-catenin-LEF-DNA. Moreover, in plakoglobin-transfected cells plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous β-catenin, whose level is elevated by plakoglobin transfection, formed a β-catenin–LEF–DNA complex. Removal of the N- and C-terminal domains of both β-catenin and plakoglobin (leaving the armadillo repeat domain intact) induced plakoglobin-LEF-DNA complex formation and also enhanced β-catenin–LEF–DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous β-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of β-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous β-catenin levels. These results suggest that overexpression of plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.
20163877
Spectrum of clinicopathologic manifestations of arrhythmogenic right ventricular cardiomyopathy/dysplasia: a multicenter study.
OBJECTIVES
The aim of the present investigation was to redefine the clinicopathologic profile of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC), with special reference to disease progression and left ventricular (LV) involvement.


BACKGROUND
Long-term follow-up data from clinical studies indicate that ARVC is a progressive heart muscle disease that with time may lead to more diffuse right ventricular (RV) involvement and LV abnormalities and culminate in heart failure.


METHODS
Forty-two patients (27 male, 15 female; 9 to 65 years old, mean [+/-SD] age 29.6 +/- 18) from six collaborative medical centers, with a pathologic diagnosis of ARVC at autopsy or heart transplantation, and with the whole heart available, were studied according to a specific clinicomorphologic protocol.


RESULTS
Thirty-four patients died suddenly (16 during effort); 4 underwent heart transplantation; 2 died as a result of advanced heart failure; and 2 died of other causes. Sudden death was the first sign of disease in 12 patients; the other 30 had palpitations, with syncope in 11, heart failure in 8 and stroke in 3. Twenty-seven patients experienced ventricular arrhythmias (ventricular tachycardia in 17), and 5 received a pacemaker. Ten patients had isolated RV involvement (group A); the remaining 32 (76%) also had fibrofatty LV involvement that was observed histologically only in 15 (group B) and histologically and macroscopically in 17 (group C). Patients in group C were significantly older than those in groups A and B (39 +/- 15 years vs. 20 +/- 8.8 and 25 +/- 9.7 years, respectively), had significantly longer clinical follow-up (9.3 +/- 7.3 years vs. 1.2 +/- 2.1 and 3.4 +/- 2.2 years, respectively) and developed heart failure significantly more often (47% vs. 0 and 0, respectively). Patients in groups B and C had warning symptoms (80% and 87%, respectively, vs. 30%) and clinical ventricular arrhythmias (73% and 82%, respectively, vs. 20%) significantly more often than patients in group A. Hearts from patients in group C weighed significantly more than those from patients in groups A and B (500 +/- 150 g vs. 328 +/- 40 and 380 +/- 95 g, respectively), whereas hearts from both group B and C patients had severe RV thinning (87% and 71%, respectively, vs. 20%) and inflammatory infiltrates (73% and 88%, respectively, vs. 30%) significantly more often than those from group A patients.


CONCLUSIONS
LV involvement was found in 76% of hearts with ARVC, was age dependent and was associated with clinical arrhythmic events, more severe cardiomegaly, inflammatory infiltrates and heart failure. ARVC can no longer be regarded as an isolated disease of the right ventricle.
23431148
WNT/β-catenin Signaling Pathway and Downstream Modulators in Low- and High-grade Glioma.
BACKGROUND
Aberrant activation of the canonical Wingless-type MMTV integration site family (WNT)/β-catenin signaling pathway is critical for gliomas.


MATERIALS AND METHODS
In 74 gliomas of different histological grade and in 24 glioblastoma cell lines, protein expression of WNT member 3a (WNT3a), β-catenin and transcription factor 4 (TCF4) was investigated by immunohistochemistry, western blotting, immunofluorescence and immunocytochemistry. In tumors and cell lines, WNT3A expression was assessed at the mRNA level by quantitative real-time polymerase chain reaction.


RESULTS
WNT3a was overexpressed at the protein and mRNA levels in malignant astrocytic tumors and cell lines. Cytoplasmic expression of β-catenin was detected in high-grade gliomas and cell lines, with evidence of nuclear translocation on fractionated protein extracts. Activating mutations in the β-catenin encoding gene (CTNNB1) were excluded by direct sequencing. TCF4 was statistically correlated with Ki-67/MIB-1 and cyclin D1 labeling indices.


CONCLUSION
Expression of WNT3a, cytoplasmic β-catenin and TCF4 was significantly associated with the histological malignancy grade and with a worse prognosis for patients with glioma.
39211681
Wnt/beta-Catenin pathway in human glioma: expression pattern and clinical/prognostic correlations
Gliomas are the most common primary intracranial tumors. Understanding the molecular basis of gliomas’ progression is required to develop more effective therapies. The Wnt/β-catenin signaling cascade is an important signal transduction pathway in human cancers. Although, overactivation of this pathway is a hallmark of several forms of cancer, little is known about its role in human gliomas. Here, we aimed to determine the clinical significance of Wnt/β-catenin pathway components in gliomas. Immunohistochemical staining was performed to detect the expression patterns of Wnt1, β-catenin and Cyclin D1 in the biopsies from 96 patients with primary gliomas. Kaplan–Meier survival and Cox regression analyses were performed to evaluate the prognosis of patients. Cytoplasmic staining pattern of Wnt1, membranous, cytoplasmic and nuclear accumulation of β-catenin, and nuclear localization of Cyclin D1 were demonstrated by immunohistochemical staining. The Wnt1 expression significantly correlated with the expression of Cyclin D1 (P < 0.0001). The ratio of tumors with a cytoplasmic–nuclear pattern or a cytoplasmic pattern of β-catenin was significantly higher in Wnt1-positive (P < 0.01) and Cyclin D1-positive (P < 0.01) tumors than in Wnt1-negative and Cyclin D1-negative tumors, respectively. The protein expression levels of Wnt1, β-catenin and Cyclin D1 were all positively correlated with the Karnofsky performance scale (KPS) score and World Health Organization (WHO) grades of patients with gliomas. Furthermore, Wnt1, cytoplasmic–nuclear β-catenin and Cyclin D1 status were all the independent prognostic factors for glioma patients (P = 0.01, 0.007 and 0.005, respectively). These results provide convincing evidence that the Wnt/β-catenin pathway correlated closely with the progression of gliomas and might be a novel prognostic marker for this neoplasm.
2360593
Activation of Wnt/β-catenin/Tcf signaling pathway in human astrocytomas
Astrocytomas are the most common form of primary brain tumors. Understanding the molecular basis of development and progression of astrocytomas is required to develop more effective therapies. Although, over activation of Wnt/beta-catenin/Tcf pathway is a hallmark of several forms of cancer, little is known about its role in human astrocytomas. Here, we report the evidence that Wnt/beta-catenin/Tcf signaling pathway is constitutively activated in astrocytic tumors. In the present study, human astrocytic tumors with different clinical grades were analyzed for mRNA expression of Dvl-1, Dvl-2, Dvl-3, beta-catenin, c-myc and cyclin D1 and protein levels of beta-catenin, Lef1, Tcf4, c-Myc, N-Myc, c-jun and cyclin D1. RT-PCR analysis demonstrated the overexpression of Dvl-3, beta-catenin, c-myc and cyclin D1 in astrocytomas. Western blotting revealed upregulation of beta-catenin, Lef1, Tcf4 and their target proteins in the core tumor tissues in comparison to peritumor and normal brain tissues. The protein and mRNA levels were positively correlated with the histological malignancy. Cytoplasmic and nuclear accumulation of beta-catenin, nuclear localization of Lef1, Tcf4, c-Myc, N-Myc, c-jun and cyclin D1 were demonstrated by immunohistochemical staining. Our studies tend to suggest that Wnt/beta-catenin/Tcf signaling pathway is implicated in malignancy of astrocytomas.
39825460
Activation of canonical WNT/β-catenin signaling enhances in vitro motility of glioblastoma cells by activation of ZEB1 and other activators of epithelial-to-mesenchymal transition.
Here we show that activation of the canonical WNT/β-catenin pathway increases the expression of stem cell genes and promotes the migratory and invasive capacity of glioblastoma. Modulation of WNT signaling alters the expression of epithelial-to-mesenchymal transition activators, suggesting a role of this process in the regulation of glioma motility. Using immunohistochemistry in patient-derived glioblastoma samples we showed higher numbers of cells with intranuclear signal for β-catenin in the infiltrating edge of tumor compared to central tumor parenchyma. These findings suggest that canonical WNT/β-catenin pathway is a critical regulator of GBM invasion and may represent a potential therapeutic target.
25365463
β-catenin and Gli1 are prognostic markers in glioblastoma
Glioblastomas (GBMs), the most common primary malignancies of the central nervous system, are highly aggressive and heterogeneous, and remain a dramatic therapeutic challenge. Markers mirroring the complex molecular profile of GBMs that are predictive of patient outcomes are needed to define novel multi-targeted treatment strategies. Resistance to current GBM therapies is partly due to a subpopulation of stem-like and other self-renewing cells (hereafter called glioma stem-like cancer cells, GSCC), which are therefore of key interest as therapeutic entry points. Wnt and Hedgehog are among the main pathways involved in GSCC renewal. β-catenin and Gli1 are markers of Wnt and Hedgehog activation respectively and both pathways are known to be altered in gliomas. To date, there are no investigations of Gli1 protein expression in GBM tissue, and recently a high expression of β-catenin has been found to have a poor prognostic impact in GBM patients in a study. We have therefore quantified the positivity for β-catenin, Gli1, as well as Ki-67, p53, and EGFR proteins on immunohistochemically-stained GBM sections from 106 patients in an investigation for potential predictive biomarkers. Correlation between these markers and survival was evaluated by pair-wise Pearson correlation coefficient and by bi-dimensional hierarchical clustering, followed by survival estimations using linear regression models and classification trees. We demonstrated that both β-catenin and, for the first time, Gli1 proteins are highly predictive markers of short survival, being found in 75 and 90% of the highly predictive trees, respectively, whereas Ki-67, p53 and EGFR were under 30% and thus, not considered as predictive. Our results indicate a role of β-catenin and Gli1 in GBM malignant behaviour, and suggest that inhibiting members of Wnt and Hedgehog pathways could be a valuable therapeutic strategy for GBM patients. See commentary: A magnifying glass on glioblastoma stem cell signaling pathways
206537328
PLAGL2 regulates Wnt signaling to impede differentiation in neural stem cells and gliomas.
A hallmark feature of glioblastoma is its strong self-renewal potential and immature differentiation state, which contributes to its plasticity and therapeutic resistance. Here, integrated genomic and biological analyses identified PLAGL2 as a potent protooncogene targeted for amplification/gain in malignant gliomas. Enhanced PLAGL2 expression strongly suppresses neural stem cell (NSC) and glioma-initiating cell differentiation while promoting their self-renewal capacity upon differentiation induction. Transcriptome analysis revealed that these differentiation-suppressive activities are attributable in part to PLAGL2 modulation of Wnt/beta-catenin signaling. Inhibition of Wnt signaling partially restores PLAGL2-expressing NSC differentiation capacity. The identification of PLAGL2 as a glioma oncogene highlights the importance of a growing class of cancer genes functioning to impart stem cell-like characteristics in malignant cells.
2944241
Temozolomide downregulates P-glycoprotein expression in glioblastoma stem cells by interfering with the Wnt3a/glycogen synthase-3 kinase/β-catenin pathway.
BACKGROUND
Glioblastoma multiforme stem cells display a highly chemoresistant phenotype, whose molecular basis is poorly known. We aim to clarify this issue and to investigate the effects of temozolomide on chemoresistant stem cells.


METHODS
A panel of human glioblastoma cultures, grown as stem cells (neurospheres) and adherent cells, was used.


RESULTS
Neurospheres had a multidrug resistant phenotype compared with adherent cells. Such chemoresistance was overcome by apparently noncytotoxic doses of temozolomide, which chemosensitized glioblastoma cells to doxorubicin, vinblastine, and etoposide. This effect was selective for P-glycoprotein (Pgp) substrates and for stem cells, leading to an investigation of whether there was a correlation between the expression of Pgp and the activity of typical stemness pathways. We found that Wnt3a and ABCB1, which encodes for Pgp, were both highly expressed in glioblastoma stem cells and reduced by temozolomide. Temozolomide-treated cells had increased methylation of the cytosine-phosphate-guanine islands in the Wnt3a gene promoter, decreased expression of Wnt3a, disrupted glycogen synthase-3 kinase/β-catenin axis, reduced transcriptional activation of ABCB1, and a lower amount and activity of Pgp. Wnt3a overexpression was sufficient to transform adherent cells into neurospheres and to simultaneously increase proliferation and ABCB1 expression. On the contrary, glioblastoma stem cells silenced for Wnt3a lost the ability to form neurospheres and reduced at the same time the proliferation rate and ABCB1 levels.


CONCLUSIONS
Our work suggests that Wnt3a is an autocrine mediator of stemness, proliferation, and chemoresistance in human glioblastoma and that temozolomide may chemosensitize the stem cell population by downregulating Wnt3a signaling.
12749295
FoxM1 promotes β-catenin nuclear localization and controls Wnt target-gene expression and glioma tumorigenesis.
Wnt/β-catenin signaling is essential for stem cell regulation and tumorigenesis, but its molecular mechanisms are not fully understood. Here, we report that FoxM1 is a downstream component of Wnt signaling and is critical for β-catenin transcriptional function in tumor cells. Wnt3a increases the level and nuclear translocation of FoxM1, which binds directly to β-catenin and enhances β-catenin nuclear localization and transcriptional activity. Genetic deletion of FoxM1 in immortalized neural stem cells abolishes β-catenin nuclear localization. FoxM1 mutations that disrupt the FoxM1-β-catenin interaction or FoxM1 nuclear import prevent β-catenin nuclear accumulation in tumor cells. FoxM1-β-catenin interaction controls Wnt target gene expression, is required for glioma formation, and represents a mechanism for canonical Wnt signaling during tumorigenesis.
34801495
Wnt3a mediated activation of Wnt/β-catenin signaling promotes tumor progression in glioblastoma
Presence of a distinct population of cells that drives tumor progression supports the hierarchical model of tumor development in Glioblastoma (GBM) and substantiates the cancer stem cell hypothesis. Amongst the various developmental signaling pathways that are aberrantly activated, we here show that activated Wnt/β-catenin signaling pathway plays a critical role in malignant transformation and tumor progression in gliomas. We demonstrate that Wnt ligands - Wnt1 and Wnt3a are expressed in a graded manner in these tumors as well as over-expressed in glioma stem cell-lines. A selective inhibition of Wnt signaling pathway by selective knock-down of its ligands Wnt1 and Wnt3a in glioma-derived stem-like cells led to decreased cell proliferation, cell migration and chemo-resistance. Furthermore, Wnt silencing in glioma cells reduced the capacity to form intra-cranial tumors in vivo. Taken together, our study indicates Wnt/β-catenin signaling pathway as an essential driver of glioma tumorigenesis, recognizing role of Wnt3a as an oncogene and thereby offering novel therapeutic strategies for management of these tumors.
3136582
Downregulation of Wnt2 and β-catenin by siRNA suppresses malignant glioma cell growth
Increasing evidence suggests that aberrant activation of Wnt signaling is involved in tumor development and progression. Our earlier study on gene expression profile in human gliomas by microarray found that some members of Wnt family were overexpressed. To further investigate the involvement of Wnt signaling in gliomas, the expression of core components of Wnt signaling cascade in 45 astrocytic glioma specimens with different tumor grades was examined by reverse transcription-PCR and immunohistochemistry. Wnt2, Wnt5a, frizzled2 and β-catenin were overexpressed in gliomas. Knockdown of Wnt2 and its key mediator β-catenin in the canonical Wnt pathway by siRNA in human U251 glioma cells inhibited cell proliferation and invasive ability, and induced apoptotic cell death. Furthermore, treating the nude mice carrying established subcutaneous U251 gliomas with siRNA targeting Wnt2 and β-catenin intratumorally also delayed the tumor growth. In both in vitro and in vivo studies, downregulation of Wnt2 and β-catenin was associated with the decrease of PI3K/p-AKT expression, indicating the interplay between Wnt/β-catenin and PI3K/AKT signaling cascades. In conclusion, the canonical Wnt pathway is of critical importance in the gliomagenesis and intervention of this pathway may provide a new therapeutic approach for malignant gliomas.
21333323
Role of Wnt5a in the proliferation of human glioblastoma cells.
Wnt5a operates as either a tumor suppressor or a tumor stimulator, according to tumor type. The functions of Wnt5a in human glioblastoma (GBM) have yet to be determined. We initially evaluated the expression of Wnt5a in human glioma. The results of immunohistochemical analyses have revealed that Wnt5a expression was higher in human GBM than in normal brain tissue and low-grade astrocytoma. In order to assess the role of Wnt5a on proliferation in human glioblastoma cells, we employed U87MG and GBM-05, a newly established GBM cell line. GBM-05 was established from a patient diagnosed with GBM. GBM-05 cells were shown to express Nestin, but did not express GFAP and Map2ab. GBM-05 cells formed infiltrating brain tumors after being intracerebrally transplanted into nude mice, and xenotransplanted GBM-05 cells were observed to differentiate into neuronal and astrocyte lineages. Wnt5a expression in the xenotransplanted tumors was higher than that detected in the surrounding brain tissues. The overexpression of Wnt5a increased the proliferation of GBM-05 and U87MG in vitro. By way of contrast, the downregulation of Wnt5a expression as the result of RNA interference reduced proliferation from GBM-05 and U87MG cells in vitro, and reduced tumorigenicity in vivo. Our data indicate that Wnt5a signaling is an important regulator in the proliferation of human glioma cells.
20626131
Relationship between the Expression of E-, N-cadherins and beta-catenin and Tumor Grade in Astrocytomas
Cadherins are cell-surface glycoproteins that mediate Ca2+-dependent, homophilic cell–cell adhesion. The classical cadherins, E- and N-cadherins, connect to beta-catenin, the lining protein. There appears to be a relationship between their dysfunction and tumor invasion and metastasis. The aim of our study was to examine the possibility of a relationship between alterations in the E- and N-cadherin and catenin expression and malignancy in astrocytomas. Forty-five astrocytomas (18 glioblastomas, 16 anaplastic astrocytomas, and 11 diffuse astrocytomas) were collected and stained immunohistochemically for cadherins and beta-catenin. None of the astrocytomas were immunoreactive for E-cadherin. N-cadherin and beta-catenin were present at cell–cell borders in 61% of glioblastomas and 31% of anaplastic astrocytomas. The incidence of immunoreactivity for N-cadherin and beta-catenin increased significantly with the histological grade of astrocytomas (p=0.001, by Kruskal–Wallis test). Moreover, in anaplastic astrocytomas and glioblastomas, the Ki-67 labeling indices in both N-cadherin-positive and beta-catenin-positive cases were higher than that in negative cases (p=0.05 and 0.03, respectively, by Fisher's exact test). These results suggest that the expression of N-cadherin or beta-catenin may be related to the biological behavior of astrocytomas.
38311104
Proteomic analysis of β‐catenin activation in mouse liver by DIGE analysis identifies glucose metabolism as a new target of the Wnt pathway
The Wnt/β‐catenin signaling pathway has been increasingly implicated in liver development and physiology. Aberrant activation of this pathway is one of the major genetic events observed during the process of human HCC development. To gain insight into the mechanism underlying β‐catenin action in the liver, we conducted a quantitative differential proteomic analysis using 2‐D DIGE combined with MS, in mice with liver‐specific deletion of Apc resulting in acute activation of β‐catenin signaling (ApcKOliv mice). We identified 94 protein spots showing differential expression between mutant ApcKOliv and control mice, corresponding to 56 individual proteins. Most of the proteins identified were associated with metabolic pathways, such as ammonia and glucose metabolism. Our analysis showed an increase in lactate dehydrogenase activity together with a downregulation of two mitochondrial ATPase subunits (ATP5a1 and ATP5b). These observations indicate that β‐catenin signaling may induce a shift in the glucose metabolism from oxidative phosphorylation to glycolysis, known as the “Warburg effect”. Imaging with 18F‐fluoro‐2‐deoxy‐D‐glucose‐positron emission tomography suggests that the specific metabolic reprogramming induced by β‐catenin in the liver does not imply the first step of glycolysis. This observation may explain why some HCCs are difficult to assess by fluoro‐2‐deoxy‐D‐glucose‐positron emission tomography imaging.
7200927
Rethinking the Warburg effect with Myc micromanaging glutamine metabolism.
The MYC oncogene, which is frequently deregulated in human cancers, encodes a master transcription factor c-Myc (herein termed Myc) that integrates cell proliferation with metabolism through its regulation of thousands of genes including microRNAs (miRNA). In addition to its known function in regulating the cell cycle and glucose metabolism, recent studies document a role for Myc in stimulating glutamine catabolism, in part through the repression of miRNAs miR-23a and miR-23b. These observations suggest an additional level of complexity in tumor metabolism, which includes the commensal metabolic relationship between hypoxic and nonhypoxic regions of tumors as well as the surrounding stroma. Thus, a reevaluation of cancer metabolism considering glutamine catabolism with a better understanding of the tumor histological complexity is needed before cancer metabolism can be effectively targeted in therapy.
14302639
Mitotic and mitogenic Wnt signalling
Canonical Wnt signalling plays an important role in development, tissue homeostasis, and cancer. At the cellular level, canonical Wnt signalling acts by regulating cell fate, cell growth, and cell proliferation. With regard to proliferation, there is increasing evidence for a complex interaction between canonical Wnt signalling and the cell cycle. Mitogenic Wnt signalling regulates cell proliferation by promoting G1 phase. In mitosis, components of the Wnt signalling cascade function directly in spindle formation. Moreover, Wnt signalling is strongly activated in mitosis, suggesting that ‘mitotic Wnt signalling’ plays an important role to orchestrate a cell division program. Here, we review the complex interplay between Wnt signalling and the cell cycle.
8168438
Myc regulates a transcriptional program that stimulates mitochondrial glutaminolysis and leads to glutamine addiction
Mammalian cells fuel their growth and proliferation through the catabolism of two main substrates: glucose and glutamine. Most of the remaining metabolites taken up by proliferating cells are not catabolized, but instead are used as building blocks during anabolic macromolecular synthesis. Investigations of phosphoinositol 3-kinase (PI3K) and its downstream effector AKT have confirmed that these oncogenes play a direct role in stimulating glucose uptake and metabolism, rendering the transformed cell addicted to glucose for the maintenance of survival. In contrast, less is known about the regulation of glutamine uptake and metabolism. Here, we report that the transcriptional regulatory properties of the oncogene Myc coordinate the expression of genes necessary for cells to engage in glutamine catabolism that exceeds the cellular requirement for protein and nucleotide biosynthesis. A consequence of this Myc-dependent glutaminolysis is the reprogramming of mitochondrial metabolism to depend on glutamine catabolism to sustain cellular viability and TCA cycle anapleurosis. The ability of Myc-expressing cells to engage in glutaminolysis does not depend on concomitant activation of PI3K or AKT. The stimulation of mitochondrial glutamine metabolism resulted in reduced glucose carbon entering the TCA cycle and a decreased contribution of glucose to the mitochondrial-dependent synthesis of phospholipids. These data suggest that oncogenic levels of Myc induce a transcriptional program that promotes glutaminolysis and triggers cellular addiction to glutamine as a bioenergetic substrate.
20655189
Deregulation of Glucose Transporter 1 and Glycolytic Gene Expression by c-Myc*
Unlike normal mammalian cells, which use oxygen to generate energy, cancer cells rely on glycolysis for energy and are therefore less dependent on oxygen. We previously observed that the c-Myc oncogenic transcription factor regulates lactate dehydrogenase A and induces lactate overproduction. We, therefore, sought to determine whether c-Myc controls other genes regulating glucose metabolism. In Rat1a fibroblasts and murine livers overexpressing c-Myc, the mRNA levels of the glucose transporter GLUT1, phosphoglucose isomerase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, and enolase were elevated. c-Myc directly transactivates genes encoding GLUT1, phosphofructokinase, and enolase and increases glucose uptake in Rat1 fibroblasts. Nuclear run-on studies confirmed that the GLUT1 transcriptional rate is elevated by c-Myc. Our findings suggest that overexpression of the c-Myc oncoprotein deregulates glycolysis through the activation of several components of the glucose metabolic pathway.
24455208
Distinct regulatory properties of pyruvate dehydrogenase kinase and phosphatase isoforms.
The mammalian pyruvate dehydrogenase complex (PDC) plays central and strategic roles in the control of the use of glucose-linked substrates as sources of oxidative energy or as precursors in the biosynthesis of fatty acids. The activity of this mitochondrial complex is regulated by the continuous operation of competing pyruvate dehydrogenase kinase (PDK) and pyruvate dehydrogenase phosphatase (PDP) reactions. The resulting interconversion cycle determines the fraction of active (nonphosphorylated) pyruvate dehydrogenase (E1) component. Tissue-specific and metabolic state-specific control is achieved by the selective expression and distinct regulatory properties of at least four PDK isozymes and two PDP isozymes. The PDK isoforms are members of a family of serine kinases that are not structurally related to cytoplasmic Ser/Thr/Tyr kinases. The catalytic subunits of the PDP isoforms are Mg2+-dependent members of the phosphatase 2C family that has binuclear metal-binding sites within the active site. The dihydrolipoyl acetyltransferase (E2) and the dihydrolipoyl dehydrogenase-binding protein (E3BP) are multidomain proteins that form the oligomeric core of the complex. One or more of their three lipoyl domains (two in E2) selectively bind each PDK and PDP1. These adaptive interactions predominantly influence the catalytic efficiencies and effector control of these regulatory enzymes. When fatty acids are the preferred source of acetyl-CoA and NADH, feedback inactivation of PDC is accomplished by the activity of certain kinase isoforms being stimulated upon preferentially binding a lipoyl domain containing a reductively acetylated lipoyl group. PDC activity is increased in Ca2+-sensitive tissues by elevating PDP1 activity via the Ca2+-dependent binding of PDP1 to a lipoyl domain of E2. During starvation, the irrecoverable loss of glucose carbons is restricted by minimizing PDC activity due to high kinase activity that results from the overexpression of specific kinase isoforms. Overexpression of the same PDK isoforms deleteriously hinders glucose consumption in unregulated diabetes.
20108952
Enzymes involved in l-lactate metabolism in humans.
l-lactate formation occurs via the reduction of pyruvate catalyzed by lactate dehydrogenase. l-lactate removal takes place via its oxidation into pyruvate, which may be oxidized or converted into glucose. Pyruvate oxidation involves the cooperative effort of pyruvate dehydrogenase, the tricarboxylic acid cycle, and the mitochondrial respiratory chain. Enzymes of the gluconeogenesis pathway sequentially convert pyruvate into glucose. In addition, pyruvate may undergo reversible transamination to alanine by alanine aminotransferase. Enzymes involved in l-lactate metabolism are crucial to diabetes pathophysiology and therapy. Elevated plasma alanine aminotransferase concentration has been associated with insulin resistance. Polymorphisms in the G6PC2 gene have been associated with fasting glucose concentration and insulin secretion. In diabetes patients, pyruvate dehydrogenase is down-regulated and the activity of pyruvate carboxylase is diminished in the pancreatic islets. Inhibitors of fructose 1,6-bisphosphatase are being investigated as potential therapy for type 2 diabetes. In addition, enzymes implicated in l-lactate metabolism have revealed to be important in cancer cell homeostasis. Many human tumors have higher LDH5 levels than normal tissues. The LDHC gene is expressed in a broad range of tumors. The activation of PDH is a potential mediator in the body response that protects against cancer and PDH activation has been observed to reduce glioblastoma growth. The expression of PDK1 may serve as a biomarker of poor prognosis in gastric cancer. Mitochondrial DNA mutations have been detected in a number of human cancers. Genes encoding succinate dehydrogenase have tumor suppressor functions and consequently mutations in these genes may cause a variety of tumors.
23093679
Pyruvate Dehydrogenase Complex Activity Controls Metabolic and Malignant Phenotype in Cancer Cells*
High lactate generation and low glucose oxidation, despite normal oxygen conditions, are commonly seen in cancer cells and tumors. Historically known as the Warburg effect, this altered metabolic phenotype has long been correlated with malignant progression and poor clinical outcome. However, the mechanistic relationship between altered glucose metabolism and malignancy remains poorly understood. Here we show that inhibition of pyruvate dehydrogenase complex (PDC) activity contributes to the Warburg metabolic and malignant phenotype in human head and neck squamous cell carcinoma. PDC inhibition occurs via enhanced expression of pyruvate dehydrogenase kinase-1 (PDK-1), which results in inhibitory phosphorylation of the pyruvate dehydrogenase α (PDHα) subunit. We also demonstrate that PDC inhibition in cancer cells is associated with normoxic stabilization of the malignancy-promoting transcription factor hypoxia-inducible factor-1α (HIF-1α) by glycolytic metabolites. Knockdown of PDK-1 via short hairpin RNA lowers PDHα phosphorylation, restores PDC activity, reverts the Warburg metabolic phenotype, decreases normoxic HIF-1α expression, lowers hypoxic cell survival, decreases invasiveness, and inhibits tumor growth. PDK-1 is an HIF-1-regulated gene, and these data suggest that the buildup of glycolytic metabolites, resulting from high PDK-1 expression, may in turn promote HIF-1 activation, thus sustaining a feed-forward loop for malignant progression. In addition to providing anabolic support for cancer cells, altered fuel metabolism thus supports a malignant phenotype. Correction of metabolic abnormalities offers unique opportunities for cancer treatment and may potentially synergize with other cancer therapies.
36759050
Mitochondrial activation by inhibition of PDKII suppresses HIF1a signaling and angiogenesis in cancer
Most solid tumors are characterized by a metabolic shift from glucose oxidation to glycolysis, in part due to actively suppressed mitochondrial function, a state that favors resistance to apoptosis. Suppressed mitochondrial function may also contribute to the activation of hypoxia-inducible factor 1α (HIF1α) and angiogenesis. We have previously shown that the inhibitor of pyruvate dehydrogenase kinase (PDK) dichloroacetate (DCA) activates glucose oxidation and induces apoptosis in cancer cells in vitro and in vivo. We hypothesized that DCA will also reverse the ‘pseudohypoxic’ mitochondrial signals that lead to HIF1α activation in cancer, even in the absence of hypoxia and inhibit cancer angiogenesis. We show that inhibition of PDKII inhibits HIF1α in cancer cells using several techniques, including HIF1α luciferase reporter assays. Using pharmacologic and molecular approaches that suppress the prolyl-hydroxylase (PHD)-mediated inhibition of HIF1α, we show that DCA inhibits HIF1α by both a PHD-dependent mechanism (that involves a DCA-induced increase in the production of mitochondria-derived α-ketoglutarate) and a PHD-independent mechanism, involving activation of p53 via mitochondrial-derived H2O2, as well as activation of GSK3β. Effective inhibition of HIF1α is shown by a decrease in the expression of several HIF1α regulated gene products as well as inhibition of angiogenesis in vitro in matrigel assays. More importantly, in rat xenotransplant models of non-small cell lung cancer and breast cancer, we show effective inhibition of angiogenesis and tumor perfusion in vivo, assessed by contrast-enhanced ultrasonography, nuclear imaging techniques and histology. This work suggests that mitochondria-targeting metabolic modulators that increase pyruvate dehydrogenase activity, in addition to the recently described pro-apoptotic and anti-proliferative effects, suppress angiogenesis as well, normalizing the pseudo-hypoxic signals that lead to normoxic HIF1α activation in solid tumors.
3133925
Wnt signaling directs a metabolic program of glycolysis and angiogenesis in colon cancer
Much of the mechanism by which Wnt signaling drives proliferation during oncogenesis is attributed to its regulation of the cell cycle. Here, we show how Wnt/β‐catenin signaling directs another hallmark of tumorigenesis, namely Warburg metabolism. Using biochemical assays and fluorescence lifetime imaging microscopy (FLIM) to probe metabolism in vitro and in living tumors, we observe that interference with Wnt signaling in colon cancer cells reduces glycolytic metabolism and results in small, poorly perfused tumors. We identify pyruvate dehydrogenase kinase 1 (PDK1) as an important direct target within a larger gene program for metabolism. PDK1 inhibits pyruvate flux to mitochondrial respiration and a rescue of its expression in Wnt‐inhibited cancer cells rescues glycolysis as well as vessel growth in the tumor microenvironment. Thus, we identify an important mechanism by which Wnt‐driven Warburg metabolism directs the use of glucose for cancer cell proliferation and links it to vessel delivery of oxygen and nutrients.
12280721
Hypoxia-inducible Factor 1 Activation by Aerobic Glycolysis Implicates the Warburg Effect in Carcinogenesis*
Cancer cells display high rates of aerobic glycolysis, a phenomenon known historically as the Warburg effect. Lactate and pyruvate, the end products of glycolysis, are highly produced by cancer cells even in the presence of oxygen. Hypoxia-induced gene expression in cancer cells has been linked to malignant transformation. Here we provide evidence that lactate and pyruvate regulate hypoxia-inducible gene expression independently of hypoxia by stimulating the accumulation of hypoxia-inducible Factor 1α (HIF-1α). In human gliomas and other cancer cell lines, the accumulation of HIF-1α protein under aerobic conditions requires the metabolism of glucose to pyruvate that prevents the aerobic degradation of HIF-1α protein, activates HIF-1 DNA binding activity, and enhances the expression of several HIF-1-activated genes including erythropoietin, vascular endothelial growth factor, glucose transporter 3, and aldolase A. Our findings support a novel role for pyruvate in metabolic signaling and suggest a mechanism by which high rates of aerobic glycolysis can promote the malignant transformation and survival of cancer cells.
22959752
Expression of monocarboxylate transporter MCT1 in normal and neoplastic human CNS tissues
Expression of monocarboxylate transporter MCT1 was studied in archival tissues from human CNS using antibodies to the carboxyl-terminal end of MCT1. Sections of neocortex, hippocampus and cerebellum of brains from 10 adult autopsy patients who died from other than CNS disease, and from archival surgical biopsy specimens of 83 primary CNS and eight non-CNS tumors were studied. MCT1 immunoreactivity was present in microvessels and, ependymocytes of normal CNS tissues similar to that reported for MCT1 expression in rat brains. MCT1 immunoreactivity was strongest in ependymomas, hemangioblastomas and high grade glial neoplasms, and weakest in low grade gliomas. Increased MCT1 expression in high grade glial neoplasms may provide a potential therapeutic target for treatment of some CNS neoplasms.
30958881
MiR-218 reverses high invasiveness of glioblastoma cells by targeting the oncogenic transcription factor LEF1.
The invasive behavior of glioblastoma multiforme (GBM) cells is one of the             most important reasons for the poor prognosis of this cancer. For invasion, tumor             cells must acquire an ability to digest the extracellular matrix and infiltrate             the normal tissue bordering the tumor. Preventing this by altering effector molecules             can significantly improve a patient's prognosis. Accumulating evidence suggests             that miRNAs are involved in multiple biological functions, including cell invasion,             by altering the expression of multiple target genes. The expression levels of             miR-218 correlate with the invasive potential of GBM cells. In this study, we             found that miR-218 expression was low in glioma tissues, especially in GBM. The             data showed an inverse correlation in 60 GBM tissues between the levels of miR-218             and MMP mRNAs (MMP-2, -7 and -9). Additionally, ectopic expression of miR-218             suppressed the invasion of GBM cells whereas inhibition of miR-218 expression             enhanced the invasive ability. Numerous members of the MMP family are downstream             effectors of the Wnt/LEF1 pathway. Target prediction databases and luciferase             data showed that LEF1 is a new direct target of miR-218. Importantly, western             blot assays demonstrated that miR-218 can reduce protein levels of LEF1 and MMP-9.             We, therefore, hypothesize that miR-218 directly targets LEF1, resulting in reduced             synthesis of MMP-9. Results suggest that miR-218 is involved in the invasive behavior             of GBM cells and by targeting LEF1 and blocking the invasive axis, miR-218-LEF1-MMPs,             it may be useful for developing potential clinical strategies.
11087034
Mechanisms of glioma cell invasion.
Invasive growth is one of the characteristics of gliomas--local infiltration into the surrounding nerve tissue decisively restricts all treatment strategies. Particularly the merit of all local treatment modalities is queried. The question whether a glioma represents a diffuse disease of the CNS or a local disturbance with unrestrained expansion tendency is still at issue. Understanding of the invasion mechanisms is of importance inasmuch as biologically reasonable and effective strategies of limiting and suppressing glioma invasion can only hence be derived. The affinity of glioma cells towards certain structures of the extracellular matrix as well as taking advantage of tumour vascularisation with regard to extension play a decisive role. Still not fully understood are tumour host interactions. Future thinking will have to take into account these interactions as well as evidence to be derived from development neurobiology and regeneration capacity of the CNS. The present review is meant to give a short overview and disclose many questions.
23674090
Elevated levels of M(r) 92,000 type IV collagenase in human brain tumors.
Local invasive growth is one of the key features of primary malignant brain tumors accompanied by remodeling of the vasculature and destruction of normal brain tissue. Tissue invasiveness is an essential biological function used by a tumor to overcome the various barriers to its progression. The expression of metalloproteases has been shown to play a critical role in the invasive process in a number of tumors; however, their expression in human brain tumors has not been previously reported. In this study we showed metalloprotease activities at M(r) 240,000, 123,000, 92,000, 72,000, and 67,000 in brain tumor extracts. These enzyme activities were inhibited by EDTA, an inhibitor of metalloproteases. Significant increases in levels of protease bands at M(r) 92,000, 123,000, and 240,000 were observed in glioblastoma and metastatic lung tumors. Enzymatic inhibition and Western blotting with M(r) 92,000 type IV collagenase antibody confirmed the presence of M(r) 92,000 type IV collagenase in all samples. Quantitative analysis by densitometry showed 8-10-fold and 6-8-fold increases in M(r) 92,000 type IV collagenase activity in glioblastoma and metastatic lung carcinoma samples, respectively, when compared with normal brain, meningioma, astrocytoma, metastatic colon, and breast carcinoma samples. These findings provide evidence for elevated levels of metalloproteases in glioblastomas and suggest a therapeutic target for minimizing the invasive propensity of gliomas using protease inhibitors.
31527442
Frequent promoter hypermethylation of Wnt pathway inhibitor genes in malignant astrocytic gliomas
Aberrant activation of wingless (Wnt) signaling is involved in the pathogenesis of various cancers. Recent studies suggested a role of Wnt signaling in gliomas, the most common primary brain tumors. We investigated 70 gliomas of different malignancy grades for promoter hypermethylation in 8 genes encoding members of the secreted frizzled‐related protein (SFRP1, SFRP2, SFRP4, SFRP5), dickkopf (DKK1, DKK3) and naked (NKD1, NKD2) families of Wnt pathway inhibitors. All tumors were additionally analyzed for mutations in exon 3 of the β‐catenin gene (CTNNB1). While none of the tumors carried CTNNB1 mutations, we found frequent promoter hypermethylation of Wnt pathway inhibitor genes, with at least one of these genes being hypermethylated in 6 of 16 diffuse astrocytomas (38%), 4 of 14 anaplastic astrocytomas (29%), 7 of 10 secondary glioblastomas (70%) and 23 of 30 primary glioblastomas (77%). Glioblastomas often demonstrated hypermethylation of 2 or more analyzed genes. Hypermethylation of SFRP1, SFRP2 and NKD2 each occurred in more than 40% of the primary glioblastomas, while DKK1 hypermethylation was found in 50% of secondary glioblastomas. Treatment of SFRP1‐, SFRP5‐, DKK1‐, DKK3‐, NKD1‐ and NKD2‐hypermethylated U87‐MG glioblastoma cells with 5‐aza‐2′‐deoxycytidine and trichostatin A resulted in increased expression of each gene. Furthermore, SFRP1‐hypermethylated gliomas showed significantly lower expression of the respective transcripts when compared with unmethylated tumors. Taken together, our results suggest an important role of epigenetic silencing of Wnt pathway inhibitor genes in astrocytic gliomas, in particular, in glioblastomas, with distinct patterns of hypermethylated genes distinguishing primary from secondary glioblastomas.
31335282
The oncogenic activation of beta-catenin.
The activation of beta-catenin to an oncogenic state can result from the inactivation of the tumor suppressor adenomatous polyposis coli (APC), by direct mutation in the beta-catenin gene, or by the activation of wnt receptors. Once activated, beta-catenin most likely promotes tumor progression through its persistent interaction with one or more of its numerous downstream targets.
10721630
Promoter methylation of WNT inhibitory factor-1 and expression pattern of WNT/β-catenin pathway in human astrocytoma: pathologic and prognostic correlations
WNT inhibitory factor-1 (WIF1) is an antagonist of the WNT signaling pathway. We investigated the relationship between WIF1 promoter methylation and regulation of the WNT/β-catenin signaling pathway, tumor grade, and survival in patients with astrocytoma. This study included 86 cases of astrocytoma, comprising 20 diffuse astrocytomas and 66 glioblastomas. In addition, 17 temporal lobectomy specimens from patients with epilepsy were included as controls. The ratio of methylated DNA to total methylated and unmethylated DNA (% methylation) was measured by methylation- and unmethylation-specific PCR. Representative tumor tissue was immunostained for WIF1, β-catenin, cyclin D1, c-myc, and isocitrate dehydrogenase 1. Levels of WIF1 promoter methylation, mRNA expression, and protein expression in a glioblastoma cell line were compared before and after demethylation treatment. The mean percent methylation of the WIF1 promoter in astrocytomas was higher than that in control brain tissue. WIF1 protein expression was lower in the tumor group with >5% methylation than in the group with <5% methylation. Cytoplasmic β-catenin staining was more frequently observed in tumors with a low WIF1 protein expression level. Demethylation treatment of a glioblastoma cell line increased WIF1 mRNA and protein expression. Increased WIF1 promoter methylation and decreased WIF1 protein expression were not related to patient survival. In conclusion, WIF1 expression is downregulated by promoter methylation and is an important mechanism of aberrant WNT/β-catenin pathway activation in astrocytoma pathogenesis.
27937045
PPAR delta: a dagger in the heart of the metabolic syndrome.
Obesity is a growing threat to global health by virtue of its association with insulin resistance, glucose intolerance, hypertension, and dyslipidemia, collectively known as the metabolic syndrome or syndrome X. The nuclear receptors PPARalpha and PPARgamma are therapeutic targets for hypertriglyceridemia and insulin resistance, respectively, and drugs that modulate these receptors are currently in clinical use. More recent work on the less-described PPAR isotype PPARdelta has uncovered a dual benefit for both hypertriglyceridemia and insulin resistance, highlighting the broad potential of PPARdelta in the treatment of metabolic disease. PPARdelta enhances fatty acid catabolism and energy uncoupling in adipose tissue and muscle, and it suppresses macrophage-derived inflammation. Its combined activities in these and other tissues make it a multifaceted therapeutic target for the metabolic syndrome with the potential to control weight gain, enhance physical endurance, improve insulin sensitivity, and ameliorate atherosclerosis.
25843121
Rat PPARs: quantitative analysis in adult rat tissues and regulation in fasting and refeeding.
PPARs are members of the nuclear hormone receptor superfamily and are primarily involved in lipid metabolism. The expression patterns of all 3 PPAR isotypes in 22 adult rat organs were analyzed by a quantitative ribonuclease protection assay. The data obtained allowed comparison of the expression of each isotype to the others and provided new insight into the less studied PPAR beta (NR1C2) expression and function. This isotype shows a ubiquitous expression pattern and is the most abundant of the three PPARs in all analyzed tissues except adipose tissue. Its expression is especially high in the digestive tract, in addition to kidney, heart, diaphragm, and esophagus. After an overnight fast, PPAR beta mRNA levels are dramatically down-regulated in liver and kidney by up to 80% and are rapidly restored to control levels upon refeeding. This tight nutritional regulation is independent of the circulating glucocorticoid levels and the presence of PPAR alpha, whose activity is markedly up-regulated in the liver and small intestine during fasting. Finally, PPAR gamma 2 mRNA levels are decreased by 50% during fasting in both white and brown adipose tissue. In conclusion, fasting can strongly influence PPAR expression, but in only a few selected tissues.
40485523
Neuronal differentiation of embryonic midbrain cells by upregulation of peroxisome proliferator-activated receptor-gamma via the JNK-dependent pathway.
Our previous study showed that the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist 15-deoxy-PGJ(2) has the promoting ability to differentiate neuronal PC12 cells. To expand our study, the effect of 15-deoxy-PGJ(2) on the differentiation of embryonic midbrain cells into dopaminergic neuronal cells was investigated in this study. The relationship between cell differentiation with activation of PPAR-gamma and the possible signal pathway were also investigated. 15-Deoxy-PGJ(2) increased neurite extension, a typical characteristic of the differentiation of embryonic midbrain cells isolated from 12-day rat embryos in a dose-dependent manner. The expression of differentiation markers, neurofilament, tyrosine hydroxylase, and nestin, was also increased by the treatment of 15-deoxy-PGJ(2). Consistent with the increasing effect on cell differentiation, 15-deoxy-PGJ(2) increased the expression and transcriptional activity of PPAR-gamma in cultured embryonic midbrain cells. In addition, the expression of PPAR-gamma and NeuN in the differentiated neuron of fetus (17 days) and adult rat brain was co-localized. Furthermore, treatment of PPAR-gamma antagonist bisphenol A diglycidyl ether blocked 15-deoxy-PGJ(2)-induced neuronal differentiation of embryonic midbrain cells and expression of PPAR-gamma. To elucidate the possible signal pathway, the activation of mitogenic-activated protein (MAP) kinase family was determined. 15-Deoxy-PGJ(2) (0.5 microM) increased activation of Jun N-terminal kinase (JNK) and p38 kinase but not extra-signal response kinase (ERK). In addition, NGF (50 ng/ml) further increased the 15-deoxy-PGJ(2)-induced JNK activation. Moreover, pretreatment of specific inhibitor of JNK SP600125 blocked the 15-deoxy-PGJ(2)-induced JNK activation. This inhibition correlated well with the inhibition of neurite extension and expression of PPAR-gamma induced by 15-deoxy-PGJ(2). The present results therefore indicate that 15-deoxy-PGJ(2) stimulates differentiation of embryonic midbrain cells into dopaminergic neuronal cells, and its effect may be PPAR-gamma and JNK signal pathway dependent.
37172824
Terminal differentiation of human breast cancer through PPAR gamma.
We have previously demonstrated that PPAR gamma stimulates the terminal differentiation of adipocyte precursors when activated by synthetic ligands, such as the antidiabetic thiazolidinedione (TZD) drugs. We show here that PPAR gamma is expressed at significant levels in human primary and metastatic breast adenocarcinomas. Ligand activation of this receptor in cultured breast cancer cells causes extensive lipid accumulation, changes in breast epithelial gene expression associated with a more differentiated, less malignant state, and a reduction in growth rate and clonogenic capacity of the cells. Inhibition of MAP kinase, shown previously to be a powerful negative regulator of PPAR gamma, improves the TZD ligand sensitivity of nonresponsive cells. These data suggest that the PPAR gamma transcriptional pathway can induce terminal differentiation of malignant breast epithelial cells and thus may provide a novel, nontoxic therapy for human breast cancer.
10712853
Loss-of-function mutations in PPAR gamma associated with human colon cancer.
The gamma isoform of the peroxisome proliferator-activated receptor, PPAR gamma, regulates adipocyte differentiation and has recently been shown to be expressed in neoplasia of the colon and other tissues. We have found four somatic PPAR gamma mutations among 55 sporadic colon cancers: one nonsense, one frameshift, and two missense mutations. Each greatly impaired the function of the protein. c.472delA results in deletion of the entire ligand binding domain. Q286P and K319X retain a total or partial ligand binding domain but lose the ability to activate transcription through a failure to bind to ligands. R288H showed a normal response to synthetic ligands but greatly decreased transcription and binding when exposed to natural ligands. These data indicate that colon cancer in humans is associated with loss-of-function mutations in PPAR gamma.
22466491
Peroxisome Proliferator-Activated Receptor Agonists and Bladder Cancer: Lessons from Animal Studies
This article reviews available animal studies on the possible link between the use of peroxisome proliferator-activated receptor (PPAR) agonists and bladder cancer, with further discussion on the possible implications to humans. Carcinogenicity studies suggest that the PPARγ agonist pioglitazone and dual PPARα/γ agonists such as ragaglitazar, muraglitazar, and naveglitazar may increase the risk of bladder cancer in a dose-responsive pattern in rats. It is interesting that bladder cancer related to PPAR agonists shows remarkable species- and sex-specificity and has a predilection to occur in the ventral dome of bladder in rodents. While male rats treated with pioglitazone or muraglitazar have a higher propensity to develop bladder cancer than female rats, mice of both sexes do not develop bladder cancer even when exposed to very high doses. Direct genotoxicity or cytotoxicity of PPAR agonists is unlikely to be the mode of action because most of the parent compounds or their metabolites of the PPAR agonists are neither mutagenic nor genotoxic, and they are rarely excreted in the urine; but a receptor-mediated PPAR effect cannot be excluded. Some suggest a “urolithiasis hypothesis” referring to the formation of urinary solids and calculi, which subsequently causes bladder necrosis, regenerative proliferation, hypertrophy, and cancer. However, whether these animal findings could have human relevance is not yet fully understood. Some argue that the urolithiasis-induced bladder cancer might be rat-specific and would probably not be applicable to humans. An effect of increased urinary growth factors induced by PPAR agonists has also been proposed, but this requires more investigations. Before fully clarified, a balance between the risks and benefits of the use of pioglitazone, an approved oral antidiabetic agent that has recently been linked to an increased but not yet confirmed risk of bladder cancer in humans, should be justified for individual use.
20205987
Inhibition of human lung cancer cell growth by the peroxisome proliferator-activated receptor-gamma agonists through induction of apoptosis.
Peroxisome proliferator-activated receptors (PPARs), members of the nuclear hormone receptors superfamily, have an important regulatory role in adipogenesis and inflammation. PPAR-gamma ligands induce terminal differentiation and growth inhibition of human breast cancer cells and prostatic cancer cells. In this study, we demonstrated that PPAR-gamma, but not PPAR-alpha, was expressed in human lung cancer cell lines by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. We also found that the synthetic PPAR-gamma agonist thiazolidinedione compounds (troglitazone) and the endogenous PPAR-gamma ligand, 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), inhibited the growth of human lung cancer cells through the induction of apoptosis. However, PPAR-alpha agonist (bezafibrate) and other prostanoids (PGE(2), PGF(2alpha)) did not induce apoptosis. These findings suggest that PPAR-gamma may play an important role in the pathogenesis of lung cancer and that PPAR-gamma agonist may be useful therapeutic agents in the treatment of human lung cancer.
45779977
A novel PPAR alpha/gamma dual agonist inhibits cell growth and induces apoptosis in human glioblastoma T98G cells.
AIM
To examine the effect of a novel peroxisome proliferator-activated receptor (PPAR) alpha/gamma dual agonist TZD18 on cell proliferation and apoptosis in human glioblastoma T98G cells and its possible mechanism.


METHODS
RT-PCR, MTT, TUNEL, Flow cytometry, and Western blot analysis were employed.


RESULTS
TZD18 inhibited the growth of T98G cells in a concentration-dependent manner, which was associated with a G1 to S cell cycle arrest. Besides, significant apoptosis was induced after treatment with a non-toxic dose of TZD18. During the process, the expression of Bcl-2 protein was down-regulated, while that of Bax and p27kip proteins was up-regulated, and the activity of caspase-3 was elevated. However, this effect appeared to be PPARalpha and PPARgamma independent since their antagonists could not reverse this effect.


CONCLUSIONS
TZD18, a novel PPARalpha/gamma dual agonist, inhibited cell growth and induce apoptosis in human glioblastoma T98G cells in vitro, indicating a therapeutic potential for TZD18 in the treatment of glioblastoma.
8380120
Ligands for PPARγ and RAR Cause Induction of Growth Inhibition and Apoptosis in Human Glioblastomas
High-grade gliomas are characterized by a rapid proliferation rate, invasiveness and angiogenesis. Our previous data indicated that the combination of ligands for peroxisome proliferator-activated receptor γ (PPARγ) and retinoic acid receptor (RAR) induces apoptosis of breast cancer cells in vitro and in a murine model. In this study, we have shown that 11 glioblastoma cell lines and nine fresh glioblastoma tissue samples from patients expressed high-levels of PPARγ. In contrast, glia from nine healthy human brains expressed very low levels of PPARγ. No mutations or polymorphisms of the PPARγ gene were observed in these cell lines. The effect of the PPARγ ligand Pioglitazone (PGZ) either in the absence or in the presence of a RAR ligand [all-trans retinoic acid (ATRA)] on the proliferation and apoptosis of glioblastoma cells was examined using two glioblastoma cell lines (N39 and DBTRG05MG). PGZ and/or ATRA inhibited significantly the proliferation of both cell lines. Flow cytometry analysis showed that G1 cell cycle arrest was induced by these ligands. In addition, apoptosis occurred in both cell lines treated with either PGZ or ATRA, which was associated with a downregulation of bcl-2 and an upregulation of bax proteins. An enhanced effect was observed when PGZ and ATRA were combined. Furthermore, treatment of fresh glioblastoma tissue from patients with PGZ, either alone or in combination with ATRA, induced a significant level of tumor cell apoptosis together with a downregulation of bcl-2 protein level as compared with untreated control brain tissue. Taken together, our data demonstrated that PGZ, either alone or in combination with ATRA, induced apoptosis and inhibited proliferation of glioblastoma cells, and more interestingly, induced apoptosis of fresh glioblastoma cells from patients. Therefore, we conclude that these ligands may possess adjuvant therapeutic potential for patients with glioblastoma.
28241081
Peroxisome proliferator-activated receptor γ agonist pioglitazone inhibits β-catenin-mediated glioma cell growth and invasion
Gliomas are the most common primary tumors of the central nervous system. Rapid proliferation and diffuse brain invasion of these tumors are likely to determine the unfavorable prognosis. Recent studies have shown that ligand activation of peroxisome proliferator-activated receptor γ (PPARγ) can induce differentiation and inhibit proliferation of several cancer cells. In this study, we identified pioglitazone, one PPARγ ligand in particular, suppressed human glioma cells proliferation, migration, and induced glioma cells apoptosis. Concomitantly, expression level of β-catenin protein, a key molecule in carcinogenesis, was decreased in glioma cells treated with pioglitazone. Noteworthy, knockdown of β-catenin expression using siRNA technology mimicked the anti-neoplastic potency of pioglitazone. These results indicate that β-catenin is one of the mediators for pioglitazone to suppress glioma cells growth and invasion. Due to its capacity to counteract β-catenin and glioma cell proliferation and migration, pioglitazone represents a promising drug for adjuvant therapy of glioma and other highly migratory tumor entities.
384819
Inhibition of in Vivo Glioma Growth and Invasion by Peroxisome Proliferator-Activated Receptor γ Agonist Treatment
The peroxisome proliferator-activated receptor γ (PPARγ), a member of the nuclear hormone receptor family, represents a possible new target in glioma therapy. Because PPARγ plays a crucial role in regulation of insulin sensitivity, synthetic agonists are already in clinical use for type II diabetes treatment. Beyond these metabolic effects, PPARγ agonists exhibit antineoplastic effects. In this study, we investigated the antineoplastic effects of the PPARγ agonist pioglitazone in glioma cells. Pioglitazone reduced cellular viability of rat, human, and PPARγ-overexpressing glioma cells in vitro in a time- and concentration-dependent manner. No antineoplastic effects were induced by pioglitazone in glioma cells overexpressing a PPARγ mutant. Furthermore, proliferation was reduced by pioglitazone, as measured by Ki-67 immunoreactivity, in vitro. Continuous intracerebral infusion of pioglitazone into gliomas induced by intrastriatal injection of C6 cells reduced tumor volumes by 83%. Oral administration of pioglitazone reduced tumor volumes by 76.9%. Subsequent brain tissue analysis revealed induction of apoptotic cell death. Ki-67 expression and BrdU incorporation revealed a reduction of proliferation in vivo. Reduced invasion of C6 cells and lower matrix metalloproteinase 9 levels in vivo indicate pioglitazone-mediated reduction of invasion. Together, these data indicate that pioglitazone may be of potential use in treatment of malignant gliomas.
24734604
PPARγ and RXRγ ligands act synergistically as potent antineoplastic agents in vitro and in vivo glioma models
Glioblastoma represent the most common primary brain tumor in adults and are currently considered incurable. We investigated antiproliferative and anti‐invasive mechanisms of 6‐OH‐11‐O‐hydroxyfenantrene (IIF), a retinoid X receptor ligand, and pioglitazone (PGZ), a peroxisome proliferator‐activated receptor γ activator, in three different glioblastoma cell lines. A dose‐dependent reduction of tumor invasion and strong decrease of matrix metalloproteinases 2 and 9 expression was observed, especially when a combination therapy of IIF and PGZ was administered. Combined treatment also markedly reduced proliferation and induced apoptosis in all glioma cell lines tested. This was in particular accompanied by decrease of antiapoptotic proteins Bcl2 and p53, while simultaneously pro‐apoptotic cytochrome c, cleaved caspase 3, Bax and Bad levels increased. These in vitro findings were further substantiated in a murine glioma model in vivo, where oral administration of PGZ and IIF resulted in significantly reduced tumor volume and proliferation. Of note, treatment with nuclear receptor ligands was not only effective when the treatment was initiated shortly after the intraparenchymal seeding of the glioma cells, but even when initiated in the last third of the observation period. Collectively, our results demonstrate the effectiveness of a combined treatment of ligands of proliferator‐activated receptor and retinoid X receptor against glioblastoma.
16492284
Pioglitazone Effect on Glioma Stem Cell Lines: Really a Promising Drug Therapy for Glioblastoma?
Glioblastoma multiforme (GBM) represents one of the most frequent malignant brain tumors. Current therapies do not provide real solutions to this pathology. Their failure can be ascribed to a cell subpopulation with stem-like properties called glioma stem cells (GSCs). Therefore, new therapeutic strategies GSC-targeted are needed. PPARγ, a nuclear receptor involved in lipid metabolism, has already been indicated as a promising target for antineoplastic therapies. Recent studies have reported that synthetic PPARγ agonists, already in clinical use for the treatment of type II diabetes, exhibit antineoplastic effects in a wide range of malignant tumor cells, including glioma cells. We investigated the effect of the synthetic PPARγ agonist Pioglitazone on viability, proliferation, morphology, and differentiation in six GSC lines isolated from GBM patients. We also analyzed Pioglitazone-induced changes in transcriptional levels of Wnt/β catenin related genes. Results showed that response to Pioglitazone was heterogeneous inducing an evident decrease of cell viability and proliferation only in a subset of GSC lines. We did not find any sign of cell differentiation neither observing cell morphology nor analyzing the expression of stemness and differentiation markers. Moreover, Wnt/β signaling pathway was only mildly affected from a transcriptional point of view after Pioglitazone exposure.
7555466
β-Catenin overexpression in malignant glioma and its role in proliferation and apoptosis in glioblastma cells
Abstractβ-Catenin, a core component of Wnt/β-catenin signaling, has been shown to be a crucial factor in a broad range of tumors, while its role in glioma is not well understood. In this study, the expression of β-catenin in astrocytic glioma tissues with different grade and human normal cerebral tissues was examined using reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. We found a higher expression level of β-catenin in astrocytic glioma patients with high grade in comparison with the normal controls. Additionally, siRNA was transfected into human U251 glioblastoma cells by liposome after the design of siRNA was confirmed to effectively inhibit the expression of β-catenin by RT-PCR. Compared to the control siRNA group, siRNA-mediated knockdown of β-catenin in human U251 cells inhibited cell proliferation, resulted in cell apoptosis, and arrested cell cycle in G0/G1. Additionally, downregulation of β-catenin decreased the expression level of cyclin D1, c-Myc and c-jun. Taken together, these results indicate that overexpression of β-catenin may be an important contributing factor to glioma progression.
215214010
Identification of SOX2 as a novel glioma-associated antigen and potential target for T cell-based immunotherapy
Prognosis for patients suffering from malignant glioma has not substantially improved. Specific immunotherapy as a novel treatment concept critically depends on target antigens, which are highly overexpressed in the majority of gliomas, but the number of such antigens is still very limited. SOX2 was identified by screening an expression database for transcripts that are overexpressed in malignant glioma, but display minimal expression in normal tissues. Expression of SOX2 mRNA was further investigated in tumour and normal tissues by real-time PCR. Compared to cDNA from pooled normal brain, SOX2 was overexpressed in almost all (9 out of 10) malignant glioma samples, whereas expression in other, non-malignant tissues was almost negligible. SOX2 protein expression in glioma cell lines and tumour tissues was verified by Western blot and immunofluorescence. Immunohistochemistry demonstrated SOX2 protein expression in all malignant glioma tissues investigated ranging from 6 to 66% stained tumour cells. Human leucocyte antigen-A*0201-restricted SOX2-derived peptides were tested for the activation of glioma-reactive CD8 þ cytotoxic T lymphocytes (CTLs). Specific CTLs were raised against the peptide TLMKKDKYTL and were capable of lysing glioma cells. The abundant and glioma-restricted overexpression of SOX2 and the generation of SOX2-specific and tumour-reactive CTLs may recommend this antigen as target for T-cell-based immunotherapy of glioma. Malignant glioma represents the most common type of primary brain tumours in the United States (Hofman et al, 2006). Despite aggressive treatment with surgical resection followed by radio-therapy and chemotherapy, these tumours ultimately recur (Butowski et al, 2006). The median survival of patients suffering from glioblastoma multiforme (GBM), the highest-grade malignant astrocytoma, has not improved significantly over the past decades, remaining at about 12 months (Legler et al, 1999). The infiltrative nature of the tumour, the impracticality of optimal resection and the comparative intolerance of the normal brain for cytotoxic therapies together lead to a 5-year survival rate that is below 2% (Surawicz et al, 1998). This extraordinary high morbidity has triggered a desperate search for novel and more specific therapeutic approaches. The use of either antibody-based or T-cell-mediated immu-notherapy to selectively kill remnant glioma cells that could not be completely removed by surgery because of the infiltration of the tumour into the surrounding brain tissue has received increasing attention. Several animal models suggested that GBM may be amenable to immune therapeutic approaches (Sampson et al, 1996; Okada et al, 1998) and the identification of humoral as well as cellular immune responses in brain tumour patients …
42231118
Induction of apoptosis in human and rat glioma by agonists of the nuclear receptor PPARgamma.
Malignant astrocytomas are among the most common brain tumours and few therapeutic options exist. It has recently been recognized that the ligand-activated nuclear receptor PPARgamma can regulate cellular proliferation and induce apoptosis in different malignant cells. We report the effect of three structurally different PPARgamma agonists inducing apoptosis in human (U87MG and A172) and rat (C6) glioma cells. The PPARgamma agonists ciglitazone, LY171 833 and prostaglandin-J2, but not the PPARalpha agonist WY14643, inhibited proliferation and induced cell death. PPARgamma agonist-induced cell death was characterized by DNA fragmentation and nuclear condensation, as well as inhibited by the synthetic receptor-antagonist bisphenol A diglycidyl ether (BADGE). In contrast, primary murine astrocytes were not affected by PPARgamma agonist treatment. The apoptotic death in the glioma cell lines treated with PPARgamma agonists was correlated with the transient up-regulation of Bax and Bad protein levels. Furthermore, inhibition of Bax expression by specific antisense oligonucleotides protected glioma cells against PPARgamma-mediated apoptosis, indicating an essential role of Bax in PPARgamma-induced apoptosis. However, PPARgamma agonists not only induced apoptosis but also caused redifferentiation as indicated by outgrowth of long processes and expression of the redifferentiation marker N-cadherin in response to PPARgamma agonists. Taken together, treatment of glioma cells with PPARgamma agonists may hold therapeutic potential for the treatment of gliomas.
8546416
PPARγ Agonists Promote Oligodendrocyte Differentiation of Neural Stem Cells by Modulating Stemness and Differentiation Genes
Neural stem cells (NSCs) are a small population of resident cells that can grow, migrate and differentiate into neuro-glial cells in the central nervous system (CNS). Peroxisome proliferator-activated receptor gamma (PPARγ) is a nuclear receptor transcription factor that regulates cell growth and differentiation. In this study we analyzed the influence of PPARγ agonists on neural stem cell growth and differentiation in culture. We found that in vitro culture of mouse NSCs in neurobasal medium with B27 in the presence of epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) induced their growth and expansion as neurospheres. Addition of all-trans retinoic acid (ATRA) and PPARγ agonist ciglitazone or 15-Deoxy-Δ12,14-Prostaglandin J2 (15d-PGJ2) resulted in a dose-dependent inhibition of cell viability and proliferation of NSCs in culture. Interestingly, NSCs cultured with PPARγ agonists, but not ATRA, showed significant increase in oligodendrocyte precursor-specific O4 and NG2 reactivity with a reduction in NSC marker nestin, in 3–7 days. In vitro treatment with PPARγ agonists and ATRA also induced modest increase in the expression of neuronal β-III tubulin and astrocyte-specific GFAP in NSCs in 3–7 days. Further analyses showed that PPARγ agonists and ATRA induced significant alterations in the expression of many stemness and differentiation genes associated with neuro-glial differentiation in NSCs. These findings highlight the influence of PPARγ agonists in promoting neuro-glial differentiation of NSCs and its significance in the treatment of neurodegenerative diseases.
14108864
PPARγ agonists regulate the expression of stemness and differentiation genes in brain tumour stem cells
Background:Brain tumour stem cells (BTSCs) are a small population of cancer cells that exhibit self-renewal, multi-drug resistance, and recurrence properties. We have shown earlier that peroxisome proliferator-activated receptor gamma (PPARγ) agonists inhibit the expansion of BTSCs in T98G and U87MG glioma. In this study, we analysed the influence of PPARγ agonists on the expression of stemness and differentiation genes in BTSCs.Methods:The BTSCs were isolated from T98G and DB29 glioma cells, and cultured in neurobasal medium with epidermal growth factor+basic fibroblast growth factor. Proliferation was measured by WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2 H-5-tetrazolio]-1,3-benzene disulphonate) and 3H thymidine uptake assays, and gene expression was analysed by quantitative reverse--transcription PCR and Taqman array. The expression of CD133, SRY box 2, and nanog homeobox (Nanog) was also evaluated by western blotting, immunostaining, and flow cytometry.Results:We found that PPARγ agonists, ciglitazone and 15-deoxy-Δ12,14-ProstaglandinJ2, inhibited cell viability and proliferation of T98G- and DB29-BTSCs. The PPARγ agonists reduced the expansion of CD133+ BTSCs and altered the expression of stemness and differentiation genes. They also inhibited Sox2 while enhancing Nanog expression in BTSCs.Conclusion:These findings highlight that PPARγ agonists inhibit BTSC proliferation in association with altered expression of Sox2, Nanog, and other stemness genes. Therefore, targeting stemness genes in BTSCs could be a novel strategy in the treatment of glioblastoma.
16461463
Differential activation of catalase expression and activity by PPAR agonists: Implications for astrocyte protection in anti-glioma therapy☆
Glioma survival is dismal, in part, due to an imbalance in antioxidant expression and activity. Peroxisome proliferator-activated receptor (PPAR) agonists have antineoplastic properties which present new redox-dependent targets for glioma anticancer therapies. Herein, we demonstrate that treatment of primary cultures of normal rat astrocytes with PPAR agonists increased the expression of catalase mRNA protein, and enzymatic activity. In contrast, these same agonists had no effect on catalase expression and activity in malignant rat glioma cells. The increase in steady-state catalase mRNA observed in normal rat astrocytes was due, in part, to de novo mRNA synthesis as opposed to increased catalase mRNA stability. Moreover, pioglitazone-mediated induction of catalase activity in normal rat astrocytes was completely blocked by transfection with a PPARγ-dominant negative plasmid. These data suggest that defects in PPAR-mediated signaling and gene expression may represent a block to normal catalase expression and induction in malignant glioma. The ability of PPAR agonists to differentially increase catalase expression and activity in normal astrocytes but not glioma cells suggests that these compounds might represent novel adjuvant therapeutic agents for the treatment of gliomas.
14326218
LPA Induces Colon Cancer Cell Proliferation through a Cooperation between the ROCK and STAT-3 Pathways
Lysophosphatidic acid (LPA) plays a critical role in the proliferation and migration of colon cancer cells; however, the downstream signaling events underlying these processes remain poorly characterized. The aim of this study was to investigate the signaling pathways triggered by LPA to regulate the mechanisms involved in the progression of colorectal cancer (CRC). We have used three cell line models of CRC, and initially analyzed the expression profile of LPA receptors (LPAR). Then, we treated the cells with LPA and events related to their tumorigenic potential, such as migration, invasion, anchorage-independent growth, proliferation as well as apoptosis and cell cycle were evaluated. We used the Chip array technique to analyze the global gene expression profiling that occurs after LPA treatment, and we identified cell signaling pathways related to the cell cycle. The inhibition of these pathways verified the conclusions of the transcriptomic analysis. We found that the cell lines expressed LPAR1, -2 and -3 in a differential manner and that 10 μM LPA did not affect cell migration, invasion and anchorage-independent growth, but it did induce proliferation and cell cycle progression in HCT-116 cells. Although LPA in this concentration did not induce transcriptional activity of β-catenin, it promoted the activation of Rho and STAT-3. Moreover, ROCK and STAT-3 inhibitors prevented LPA-induced proliferation, but ROCK inhibition did not prevent STAT-3 activation. Finally, we observed that LPA regulates the expression of genes related to the cell cycle and that the combined inhibition of ROCK and STAT-3 prevented cell cycle progression and increased the LPA-induced expression of cyclins E1, A2 and B1 to a greater degree than either inhibitor alone. Overall, these results demonstrate that LPA increases the proliferative potential of colon adenocarcinoma HCT-116 cells through a mechanism involving cooperation between the Rho-ROCK and STAT3 pathways involved in cell cycle control.
34587801
STAT3 inhibition by WP1066 suppresses the growth and invasiveness of bladder cancer cells.
Signal transducer and activator of transcription 3 (STAT3) regulates the expression of genes mediating cell survival, proliferation and angiogenesis and is aberrantly activated in various types of malignancies, including bladder cancer. We examined whether it could be a novel therapeutic target for bladder cancer using the STAT3 inhibitor WP1066. In T24 and UMUC-3 bladder cancer cells, 5 µM WP1066 prevented the phosphorylation of STAT3 and 2.5 µM WP1066 decreased cell survival and proliferation significantly (P<0.01). WP1066 also induced apoptosis accompanied by the suppression of the expression of Bcl-2 and Bcl-xL in T24 cells. Moreover, the covered area in a wound and the number of cells invading through a Matrigel chamber decreased significantly (P<0.01) when cells were treated with WP1066. The activities of MMP-2 and MMP-9 were also decreased by treatment with 10 µM WP1066. Our results revealed that using WP1066 to inhibit the STAT3 signaling pathway suppressed the viability and invasiveness of bladder cancer cells effectively and could be a novel therapeutic strategy against bladder cancer.
7379450
STAT3 Oligonucleotide Inhibits Tumor Angiogenesis in Preclinical Models of Squamous Cell Carcinoma
Purpose Signal transducer and activator of transcription 3 (STAT3) has shown to play a critical role in head and neck squamous cell carcinoma (HNSCC) and we have recently completed clinical trials of STAT3 decoy oligonucleotide in patients with recurrent or metastatic HNSCC. However, there is limited understanding of the role of STAT3 in modulating other aspects of tumorigenesis such as angiogenesis. In this study, we aimed to examine the effects of STAT3 decoy oligonucleotide on tumor angiogenesis. Experimental Design A STAT3 decoy oligonucleotide and small interfering RNA (siRNA) were used to inhibit STAT3 in endothelial cells in vitro and in vivo. The biochemical effects of STAT3 inhibition were examined in conjunction with the consequences on proliferation, migration, apoptotic staining, and tubule formation. Additionally, we assessed the effects of STAT3 inhibition on tumor angiogenesis using murine xenograft models. Results STAT3 decoy oligonucleotide decreased proliferation, induces apoptosis, decreased migration, and decreased tubule formation of endothelial cells in vitro. The STAT3 decoy oligonucleotide also inhibited tumor angiogenesis in murine tumor xenografts. Lastly, our data suggest that the antiangiogenic effects of STAT3 decoy oligonucleotide were mediatedthrough the inhibition of both STAT3 and STAT1. Conclusions The STAT3 decoy oligonucleotidewas found to be an effective antiangiogenic agent, which is likely to contribute to the overall antitumor effects of this agent in solid tumors.Taken together with the previously demonstrated antitumor activity of this agent, STAT3 decoy oligonucleotide represents a promising single agent approach to targeting both the tumor and vascular compartments in various malignancies.
45228451
STAT3 is essential for the maintenance of neurosphere‐initiating tumor cells in patients with glioblastomas: A potential for targeted therapy?
Glioblastoma (GBM), the highest‐grade form of gliomas, is the most frequent and the most aggressive. Recently, a subpopulation of cells with stem cells characteristics, commonly named “tumor‐initiating stem cells” (TISCs) or “cancer stem cells” (CSCs) were identified in GBM. These cells were shown to be highly resistant to chemotherapeutic drugs and to ionizing radiations. Consequently, the knowledge of the signals that regulate the functions and survival of TISCs is crucial. In our work, we describe a neurosphere‐initiating cell (NS‐IC) assay to quantify TISC/CSCs from patients with GBM and show that these cells are tumorigenic in vivo. We demonstrate that the intracellular signal transducer and activator of transcription STAT3 is constitutively activated by phosphorylation preferentially on serine 727 in these cells. Moreover, we demonstrate that the selective inhibition of STAT3 by the chemical compound Stattic or by siRNA STAT3 abrogates TISC/CSC proliferation and NS‐IC suggesting that self‐renewal of GBM “stem‐like” cells depends on the presence of STAT3 for their maintenance. Finally, we show that inhibition of STAT3 by Stattic sensitizes TISC/CSCs to the inhibitory action of Temozolomide with a strong synergistic effect of both drugs. Overall, these results suggest that strategies focused on STAT3 inhibition are efficient at the level of “stem‐like” cells and could be of interest for therapeutic purposes in patients with malignant GBM.
8685570
STAT3 Activation in Glioblastoma: Biochemical and Therapeutic Implications
Signal transducer and activator of transcription 3 (STAT3) is a potent regulator of gliomagenesis through its induction of angiogenesis, host immunosuppression, and tumor invasion. Gain of function mutations result in constitutive activation of STAT3 in glioma cells, making STAT3 an attractive target for inhibition in cancer therapy. Nevertheless, some studies show that STAT3 also participates in terminal differentiation and apoptosis of various cell lines and in glioma with phosphatase and tensin homolog (PTEN)-deficient genetic backgrounds. In light of these findings, the utility of STAT3 as a prognostic indicator and as a target of drug therapies will be contingent on a more nuanced understanding of its pro- and anti-tumorigenic effects.
40477299
The Jak/STAT pathway.
The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway mediates cellular responses to cytokines (e.g., IL-6) and growth factors (e.g., EGF).
16552365
Transcription Factor STAT3 as a Novel Molecular Target for Cancer Prevention
Signal Transducers and Activators of Transcription (STATs) are a family of transcription factors that regulate cell proliferation, differentiation, apoptosis, immune and inflammatory responses, and angiogenesis. Cumulative evidence has established that STAT3 has a critical role in the development of multiple cancer types. Because it is constitutively activated during disease progression and metastasis in a variety of cancers, STAT3 has promise as a drug target for cancer therapeutics. Recently, STAT3 was found to have an important role in maintaining cancer stem cells in vitro and in mouse tumor models, suggesting STAT3 is integrally involved in tumor initiation, progression and maintenance. STAT3 has been traditionally considered as nontargetable or undruggable, and the lag in developing effective STAT3 inhibitors contributes to the current lack of FDA-approved STAT3 inhibitors. Recent advances in cancer biology and drug discovery efforts have shed light on targeting STAT3 globally and/or specifically for cancer therapy. In this review, we summarize current literature and discuss the potential importance of STAT3 as a novel target for cancer prevention and of STAT3 inhibitors as effective chemopreventive agents.
42017989
Activated STAT3 Regulates Hypoxia-Induced Angiogenesis and Cell Migration in Human Glioblastoma
BACKGROUND:Glioblastoma is the most common primary brain tumor, with typical histopathologic findings, pseudopalisading necrosis, and microvascular proliferation, all of which are associated with a poor prognosis. Hypoxia is known to affect these morphological features, but the underlying molecular mechanism has been poorly understood. OBJECTIVE:To determine the role of signal transducer and activator of transcription 3 (STAT3) in the malignant progression of glioblastoma under hypoxic conditions. METHODS:We studied STAT3 activation by hypoxic stress and its effect on hypoxia-induced angiogenesis and cell migration using U87, A172, T98, and U373 human glioblastoma cell lines. RESULTS:All four glioblastoma cells analyzed expressed detectable levels of STAT3 phosphorylation. Hypoxic stress markedly increased phosphorylated STAT3 level in a time-dependent fashion, and activated STAT3 was translocated into the nucleus. Hypoxic conditions led to a 30-50% increase in angiogenesis and cell migration, but these effects were significantly attenuated by small interfering ribonucleic acid-mediated knockdown of STAT3. Furthermore, STAT3 activation was associated with an elevated expression of hypoxic inducible factor-1, vascular endothelial growth factor, matrix metalloproteinase 2, and TWIST messenger ribonucleic acid and protein, which may play a critical role in hypoxia-induced angiogenesis and migration. CONCLUSION:STAT3 plays an important role in glioblastoma angiogenesis and migration triggered by hypoxia. Therefore, STAT3 might be a target for control of pseudopalisading necrosis and angiogenesis in glioblastoma.
2794399
Knockdown of STAT3 expression by RNAi suppresses growth and induces apoptosis and differentiation in glioblastoma stem cells.
Glioblastoma is a highly lethal brain tumor of the human primary nervous system tumors. Previous studies demonstrated that glioblastoma stem cells were able to initiate and reform the original cancer. In this study, we found that there were expression and activation of STAT3, a key signal transduction factor and oncoprotein, in human glioblastoma stem cells (GSCs). STAT3 plays a key role in proliferation, apoptosis and differentiation in embryonic stem cells and several cancer types. To investigate the effects of STAT3 on human GSCs, the expression and activation of STAT3 were suppressed by RNAi mediated with lentivirus. We demonstrated that siRNA of STAT3 significantly suppressed STAT3 expression and activation and resulted in inhibition of cell growth in GSCs. Knockdown of STAT3 induces apoptosis and reduces significantly expression of Bcl-2 and cyclin-D in human primary GSCs, whereas no significance was achieved in BAX and caspase-3 expression. Inhibition of STAT3 expression is associated not only with decreasing of CD133+ cell proportion and increasing of GFAP and MBP expression, but also with decrease of the capacity to initiate a tumor in human primary GSCs. Together, these studies suggest that STAT3 is an important target for human GSCs in regulation of GSCs growth, apoptosis, differentiation and tumorigenic potential.
24328427
STAT3 Is Required for Proliferation and Maintenance of Multipotency in Glioblastoma Stem Cells
Signal transducer and activator of transcription 3 (STAT3) regulates diverse cellular processes, including cell growth, differentiation, and apoptosis, and is frequently activated during tumorigenesis. Recently, putative glioblastoma stem cells (GBM‐SCs) were isolated and characterized. These cells can self‐renew indefinitely in culture, are highly tumorigenic, and retain the ability to differentiate in culture. We have found that treatment of GBM‐SCs with two chemically distinct small molecule inhibitors of STAT3 DNA‐binding inhibits cell proliferation and the formation of new neurospheres from single cells. Genetic knockdown of STAT3 using a short hairpin RNA also inhibits GBM‐SC proliferation and neurosphere formation, confirming that these effects are specific to STAT3. Although STAT3 inhibition can induce apoptosis in serum‐derived GBM cell lines, this effect was not observed in GBM‐SCs grown in stem cell medium. Markers of neural stem cell multipotency also decrease upon STAT3 inhibition, suggesting that STAT3 is required for maintenance of the stem‐like characteristics of these cells. Strikingly, even a transient inhibition of STAT3 leads to irreversible growth arrest and inhibition of neurosphere formation. These data suggest that STAT3 regulates the growth and self‐renewal of GBM‐SCs and is thus a potential target for cancer stem cell‐directed therapy of glioblastoma multiforme. STEM CELLS 2009;27:2383–2392
39134544
On-target JAK2/STAT3 inhibition slows disease progression in orthotopic xenografts of human glioblastoma brain tumor stem cells.
BACKGROUND
Glioblastoma multiforme (GBM) is characterized by an aggressive clinical course, therapeutic resistance, and striking molecular heterogeneity. GBM-derived brain tumor stem cells (BTSCs) closely model this molecular heterogeneity and likely have a key role in tumor recurrence and therapeutic resistance. Emerging evidence indicates that Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)3 is an important mediator of tumor cell survival, growth, and invasion in a large group of GBM. Here, we used a large set of molecularly heterogeneous BTSCs to evaluate the translational potential of JAK2/STAT3 therapeutics.


METHODS
BTSCs were cultured from GBM patients and MGMT promoter methylation, and the mutation statuses of EGFR, PTEN, and TP53 were determined. Endogenous JAK2/STAT3 activity was assessed in human GBM tissue, BTSCs, and orthotopic xenografts by immunohistochemistry and Western blotting. STAT3 short hairpin (sh)RNA, cucurbitacin-I, and WP1066 were used to inhibit JAK2/STAT3 activity in vitro and in vivo.


RESULTS
The JAK2/STAT3 pathway was demonstrated to be highly activated in human GBM, molecularly heterogeneous BTSCs derived from these tumors, and BTSC xenografts. STAT3 shRNA knockdown or cucurbitacin-I and WP1066 administration resulted in on-target JAK2/STAT3 inhibition and dramatically reduced BTSC survival regardless of endogenous MGMT promoter methylation or EGFR, PTEN, and TP53 mutational status. BTSC orthotopic xenografts maintained the high levels of activated JAK2/STAT3 seen in their parent human tumors. Intraperitoneal WP1066 reduced intratumoral JAK2/STAT3 activity and prolonged animal survival.


CONCLUSION
Our study demonstrates the in vitro and in vivo efficacy of on-target JAK2/STAT3 inhibition in heterogeneous BTSC lines that closely emulate the genomic and tumorigenic characteristics of human GBM.
25419506
15d-PGJ2 and Rosiglitazone Suppress Janus Kinase-STAT Inflammatory Signaling through Induction of Suppressor of Cytokine Signaling 1 (SOCS1) and SOCS3 in Glia*
Peroxisome proliferator-activated receptor (PPAR)-γ agonists are now emerging as therapeutic drugs for various inflammatory diseases. However, their molecular mechanism of action remains to be elucidated. Here we report a novel mechanism that underlies the PPAR-γ agonist-mediated suppression of brain inflammation. We show that 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and rosiglitazone reduce the phosphorylation of STAT1 and STAT3 as well as Janus kinase 1 (JAK1) and JAK2 in activated astrocytes and microglia. The PPAR-γ agonist-mediated reduction in phosphorylation leads to the suppression of JAK-STAT-dependent inflammatory responses. The effects of 15d-PGJ2 and rosiglitazone are not mediated by activation of PPAR-γ. 15d-PGJ2 and rosiglitazone rapidly induce the transcription of suppressor of cytokine signaling (SOCS) 1 and 3, which in turn inhibit JAK activity in activated glial cells. In addition, Src homology 2 domain-containing protein phosphatase 2 (SHP2), another negative regulator of JAK activity, is also involved in their anti-inflammatory action. Our data suggest that 15d-PGJ2 and rosiglitazone suppress the initiation of JAK-STAT inflammatory signaling independently of PPAR-γ, thus attenuating brain inflammation.
35011892
Interruption of β-catenin suppresses the EGFR pathway by blocking multiple oncogenic targets in human glioma cells
Malignant gliomas are the most common type of intrinsic central nervous system (CNS) tumors with high mortality and morbidity. β-catenin is overexpressed in human glioblastoma and knockdown of β-catenin inhibits glioblastoma cell proliferation and invasive ability, and induces apoptotic cell death. Furthermore, treating the nude mice carrying established subcutaneous LN229 gliomas with siRNA targeting β-catenin intratumorally also delayed the tumor growth. However, the mechanisms of down-regulation of β-catenin that represses glioblastoma malignancy behavior remain to be elucidated. We utilized text-mining of MEDLINE abstracts with natural language processing to establish the β-catenin biologic association network, and identified several interactions of this network with the EGFR pathway. In both in vitro and in vivo studies, our results confirmed down-regulation of β-catenin induced reduced expression of EGFR, STAT3 and AKT1 mRNA and protein, besides, the level of phosphorylated Akt also decreased. A similar reduction in expression of CyclinD1, MMP2 and MMP9, downstream genes of the EGFR pathway, was observed. These results suggest that the Wnt/β-catenin pathway regulates glioma cell proliferation and invasion, in part via the EGFR pathway.
24824552
beta-Catenin/TCF pathway upregulates STAT3 expression in human esophageal squamous cell carcinoma.
Precise roles of beta-catenin/TCF pathway involved in esophageal tumorigenesis remain elusive. Here we found STAT3 overexpression in esophageal cancer cells and tissues, and its overexpression in esophageal squamous cell carcinoma (ESCC) tissues correlated with beta-catenin cytoplasmic/nuclear accumulation. A functional TCF binding element was detected in STAT3 promoter which specifically bound to TCF4. Transfected beta-catenin induced STAT3 transcriptional activity dose-dependently, and also enhanced STAT3 mRNA and protein levels. These inductions were specifically abolished by dominant-negative TCF4. These results suggest that STAT3 is a target of beta-catenin/TCF pathway and might participate in esophageal tumorigenesis.
12542738
New perspectives in glioblastoma antiangiogenic therapy
Glioblastoma (GB) is highly vascularised tumour, known to exhibit enhanced infiltrative potential. One of the characteristics of glioblastoma is microvascular proliferation surrounding necrotic areas, as a response to a hypoxic environment, which in turn increases the expression of angiogenic factors and their signalling pathways (RAS/RAF/ERK/MAPK pathway, PI3K/Akt signalling pathway and WTN signalling cascade). Currently, a small number of anti-angiogenic drugs, extending glioblastoma patients survival, are available for clinical use. Most medications are ineffective in clinical therapy of glioblastoma due to acquired malignant cells or intrinsic resistance, angiogenic receptors cross-activation and redundant intracellular signalling, or the inability of the drug to cross the blood-brain barrier and to reach its target in vivo. Researchers have also observed that GB tumours are different in many aspects, even when they derive from the same tissue, which is the reason for personalised therapy. An understanding of the molecular mechanisms regulating glioblastoma angiogenesis and invasion may be important in the future development of curative therapeutic approaches for the treatment of this devastating disease.
1866452
Aberrant Signaling Pathways in Glioma
Glioblastoma multiforme (GBM), a WHO grade IV malignant glioma, is the most common and lethal primary brain tumor in adults; few treatments are available. Median survival rates range from 12–15 months. The biological characteristics of this tumor are exemplified by prominent proliferation, active invasiveness, and rich angiogenesis. This is mainly due to highly deregulated signaling pathways in the tumor. Studies of these signaling pathways have greatly increased our understanding of the biology and clinical behavior of GBM. An integrated view of signal transduction will provide a more useful approach in designing novel therapies for this devastating disease. In this review, we summarize the current understanding of GBM signaling pathways with a focus on potential molecular targets for anti-signaling molecular therapies.
24806543
The contribution of epidermal growth factor receptor (EGFR) signaling pathway to radioresistance in human gliomas: a review of preclinical and correlative clinical data.
PURPOSE
The epidermal growth factor receptor (EGFR) pathway is frequently upregulated in high-grade gliomas via gene amplification and by specific mutations that render EGFR constitutively active (EGFRvIII).


METHODS AND MATERIALS
This review highlights EGFR's role in mediating radiation resistance in gliomas: underlying molecular mechanisms, with discussion of relevant preclinical and clinical correlative data.


RESULTS
Preclinical and emerging clinical data suggest that EGFR signaling plays a potentially important role in mediating radiation resistance in human gliomas.


CONCLUSIONS
Targeting EGFR alone, or in combination with its downstream mediators, represents a promising new approach for the management of glioma patients.
26029604
Molecular determinants of the response of glioblastomas to EGFR kinase inhibitors.
BACKGROUND
The epidermal growth factor receptor (EGFR) is frequently amplified, overexpressed, or mutated in glioblastomas, but only 10 to 20 percent of patients have a response to EGFR kinase inhibitors. The mechanism of responsiveness of glioblastomas to these inhibitors is unknown.


METHODS
We sequenced kinase domains in the EGFR and human EGFR type 2 (Her2/neu) genes and analyzed the expression of EGFR, EGFR deletion mutant variant III (EGFRvIII), and the tumor-suppressor protein PTEN in recurrent malignant gliomas from patients who had received EGFR kinase inhibitors. We determined the molecular correlates of clinical response, validated them in an independent data set, and identified effects of the molecular abnormalities in vitro.


RESULTS
Of 49 patients with recurrent malignant glioma who were treated with EGFR kinase inhibitors, 9 had tumor shrinkage of at least 25 percent. Pretreatment tissue was available for molecular analysis from 26 patients, 7 of whom had had a response and 19 of whom had rapid progression during therapy. No mutations in EGFR or Her2/neu kinase domains were detected in the tumors. Coexpression of EGFRvIII and PTEN was significantly associated with a clinical response (P<0.001; odds ratio, 51; 95 percent confidence interval, 4 to 669). These findings were validated in 33 patients who received similar treatment for glioblastoma at a different institution (P=0.001; odds ratio, 40; 95 percent confidence interval, 3 to 468). In vitro, coexpression of EGFRvIII and PTEN sensitized glioblastoma cells to erlotinib.


CONCLUSIONS
Coexpression of EGFRvIII and PTEN by glioblastoma cells is associated with responsiveness to EGFR kinase inhibitors.
207485732
Targeting the EGFR signaling pathway in cancer therapy
Introduction: Cancer is a devastating disease; however, several therapeutic advances have recently been made, wherein EGFR and its family members have emerged as useful biomarkers and therapeutic targets. EGFR, a transmembrane glycoprotein is a member of the ERBB receptor tyrosine kinase superfamily. EGFR binds to its cognate ligand EGF, which further induces tyrosine phosphorylation and receptor dimerization with other family members leading to enhanced uncontrolled proliferation. Several anti-EGFR therapies such as monoclonal antibodies and tyrosine kinase inhibitors have been developed, which has enabled clinicians to identify and treat specific patient cohorts. Areas covered: This review covers the basic mechanism of EGFR activation and the role of EGFR signaling in cancer progression. Furthermore, current developments made toward targeting the EGFR signaling pathway for the treatment of epithelial cancers and a summary of the various anti-EGFR therapeutic agents that are currently in use are also presented in this review. Expert opinion: EGFR signaling is a part of a complex network that has been the target of effective cancer therapies. However, a further understanding of the system is required to develop an effective anticancer regimen. A combination therapy that comprises an anti-EGFR and a chemotherapeutic/chemopreventive agent will exhibit a multi-pronged approach that can be developed into a highly attractive and specific molecular oriented remedy.
3069078
PI3K and STAT3: a new alliance.
UNLABELLED
Recent proteomic data have uncovered an interdependence of PI3K and STAT3. In PI3K-tranformed murine cells, STAT3 is phosphorylated on Y705 and activated in a PI3K-dependent manner. Dominant negative STAT3 interferes with PI3K-induced oncogenic transformation. Phosphorylation of STAT3 in PI3K-transformed murine cells is mediated by the TEC kinase BMX. Observations on glioblastoma stem cells reveal similar critical roles for STAT3 and BMX. The new data document an important role of STAT3 in PI3K-driven oncogenic transformation and mark BMX as a promising therapeutic target that could enhance the effectiveness of PI3K inhibitors.


SIGNIFICANCE
The PI3K–TOR and STAT3 signaling pathways represent two distinct regulatory networks. The discovery of a functional link between these pathways is significant for our understanding of PI3K- and STAT3-driven oncogenic mechanisms and identifies the TEC kinase BMX as a new cancer target.
29321530
PI3K and cancer: lessons, challenges and opportunities
The central role of phosphoinositide 3-kinase (PI3K) activation in tumour cell biology has prompted a sizeable effort to target PI3K and/or downstream kinases such as AKT and mammalian target of rapamycin (mTOR) in cancer. However, emerging clinical data show limited single-agent activity of inhibitors targeting PI3K, AKT or mTOR at tolerated doses. One exception is the response to PI3Kδ inhibitors in chronic lymphocytic leukaemia, where a combination of cell-intrinsic and -extrinsic activities drive efficacy. Here, we review key challenges and opportunities for the clinical development of inhibitors targeting the PI3K–AKT–mTOR pathway. Through a greater focus on patient selection, increased understanding of immune modulation and strategic application of rational combinations, it should be possible to realize the potential of this promising class of targeted anticancer agents.
18072294
Targeting the PI3K/AKT/mTOR signaling pathway in glioblastoma: novel therapeutic agents and advances in understanding
Glioblastoma multiforme (GBM) is a grade IV astrocytoma with a median survival of 12 months despite current multi-modal treatment options. GBM is distinguished clinicopathologically into primary and secondary subtypes. Mutations of phosphatase and tensin homolog, and subsequent upregulation of the downstream protein kinase B/mammalian target of rapamycin (mTOR) signaling pathway, are commonly seen in primary GBM and less predominantly in secondary GBM. While investigations into targeted treatments of mTOR have been attempted, feedback regulation within the mTOR signaling pathway may account for therapeutic resistance. Currently, rapamycin analogs, dual-targeted mTOR complex 1 and 2 agents as well as dual mTOR and phosphatidylinositol-3 kinase-targeted agents are being investigated experimentally and in clinical trials. This review will discuss the experimental potential of these agents in the treatment of GBM and their current stage in the GBM drug pipeline. Knowledge obtained from the application of these agents can help in understanding the pathogenesis of GBM as well as delineating subsequent treatment strategies.
2982680
Circulating endothelial progenitor cells are involved in VEGFR-2-related endothelial differentiation in glioma.
Endothelial progenitor cells (EPCs) play important roles in maintaining endothelial integrity and tumor vascularization. However, the differentiation of EPCs in the neoangiogenesis of gliomas has not yet been fully elucidated. The purpose in this study was to investigate the profile of EPC differentiation in rat C6 glioma using magnetic resonance imaging (MRI), a non-invasive monitoring assay. To achieve this goal, we isolated EPCs from rat bone marrow and identified them by detecting CD34, CD133, and VEGFR-2, the markers of EPCs. Coexpression of Ac-LDL and UEA-1 in EPCs was also determined. To dynamically monitor the migration of circulating cells, the EPCs were labeled with ultrasmall superparamagnetic iron oxide (USPIO) and injected by tail vein into rats bearing C6 glioma. MRI was performed at 24, 48, and 96 h after injection. The distribution and differentiation of EPCs were confirmed by histology. We found that the USPIO-labeled EPCs appeared at the tumor periphery where a large number of CD105-positive cells appeared at 24 h after injection by using MRI scanning. Ninety-six hours after injection, immunohistochemistry and Prussian blue staining were used to observe the labeled EPCs in the tumor tissue. We found that many of the labeled EPCs were overlapped with VEGFR-2-positive endothelial cells, but not CD105- or CD34-positive cells. These results suggest that EPCs can cross the blood-brain barrier from peripheral blood and home to tumors, where they differentiate into endothelial cells, including VEGFR-2-positive endothelial cells. MRI is a useful method for dynamically tracking the migration of USPIO-labeled EPCs.
31412828
Nuclear factor-κB in glioblastoma: insights into regulators and targeted therapy.
Nuclear factor-κB (NF-κB) is a ubiquitous transcription factor that regulates multiple aspects of cancer formation, growth, and treatment response. Glioblastoma (GBM), the most common primary malignant tumor of the central nervous system, is characterized by molecular heterogeneity, resistance to therapy, and high NF-κB activity. In this review, we examine the mechanisms by which oncogenic pathways active in GBM impinge on the NF-κB system, discuss the role of NF-κB signaling in regulating the phenotypic properties that promote GBM and, finally, review the components of the NF-κB pathway that have been targeted for treatment in both preclinical studies and clinical trials. While a direct role for NF-κB in gliomagenesis has not been reported, the importance of this transcription factor in the overall malignant phenotype suggests that more rational and specific targeting of NF-κB-dependent pathways can make a significant contribution to the management of GBM.
10051014
NF-κB and STAT3 in glioblastoma: therapeutic targets coming of age
Since we last addressed the roles of NF-κB and JAK/STAT3 signaling in glioblastoma (GBM) 5 years ago, tremendous strides have been made in the understanding of these two pathways in glioma biology. Contributing to prosurvival mechanisms, cancer stem cell maintenance and treatment resistance, both NF-κB and STAT3 have been characterized as major drivers of GBM. In this review, we address general improvements in the molecular understanding of GBM, the structure of NF-κB and STAT3 signaling, the ways in which these pathways contribute to GBM and advances in preclinical and clinical targeting of these two signaling cascades.
21592324
The transcription factor HIF-1alpha plays a critical role in the growth factor-dependent regulation of both aerobic and anaerobic glycolysis.
Mammalian cells are believed to have a cell-intrinsic ability to increase glucose metabolism in response to hypoxia. Here we show that the ability of hematopoietic cells to up-regulate anaerobic glycolysis in response to hypoxia is dependent on receptor-mediated signal transduction. In the absence of growth factor signaling, hematopoietic cells fail to express hypoxia-inducible transcription factor (Hif-1alpha) mRNA. Growth factor-deprived hematopoietic cells do not engage in glucose-dependent anabolic synthesis and neither express Hif-1alpha mRNA nor require HIF-1alpha protein to regulate cell survival in response to hypoxia. However, HIF-1alpha is adaptive for the survival of growth factor-stimulated cells, as suppression of HIF-1alpha results in death when growing cells are exposed to hypoxia. Growth factor-dependent HIF-1alpha expression reprograms the intracellular fate of glucose, resulting in decreased glucose-dependent anabolic synthesis and increased lactate production, an effect that is enhanced when HIF-1alpha protein is stabilized by hypoxia. Together, these data suggest that HIF-1alpha contributes to the regulation of growth factor-stimulated glucose metabolism even in the absence of hypoxia.
205243417
Metabolic regulation of hematopoietic stem cells in the hypoxic niche.
Tissue homeostasis over the life of an organism relies on both self-renewal and multipotent differentiation of stem cells. Hematopoietic stem cells (HSCs) reside in a hypoxic bone marrow environment, and their metabolic status is distinct from that of their differentiated progeny. HSCs generate energy mainly via anaerobic metabolism by maintaining a high rate of glycolysis. This metabolic balance promotes HSC maintenance by limiting the production of reactive oxygen species, but leaves HSCs susceptible to changes in redox status. In this review, we discuss the importance of oxygen homeostasis and energy metabolism for maintenance of HSC function and long-term self-renewal.
23123229
Acetylation targets the M2 isoform of pyruvate kinase for degradation through chaperone-mediated autophagy and promotes tumor growth.
Most tumor cells take up more glucose than normal cells but metabolize glucose via glycolysis even in the presence of normal levels of oxygen, a phenomenon known as the Warburg effect. Tumor cells commonly express the embryonic M2 isoform of pyruvate kinase (PKM2) that may contribute to the metabolism shift from oxidative phosphorylation to aerobic glycolysis and tumorigenesis. Here we show that PKM2 is acetylated on lysine 305 and that this acetylation is stimulated by high glucose concentration. PKM2 K305 acetylation decreases PKM2 enzyme activity and promotes its lysosomal-dependent degradation via chaperone-mediated autophagy (CMA). Acetylation increases PKM2 interaction with HSC70, a chaperone for CMA, and association with lysosomes. Ectopic expression of an acetylation mimetic K305Q mutant accumulates glycolytic intermediates and promotes cell proliferation and tumor growth. These results reveal an acetylation regulation of pyruvate kinase and the link between lysine acetylation and CMA.
27912091
PKM2 promotes glucose metabolism and cell growth in gliomas through a mechanism involving a let-7a/c-Myc/hnRNPA1 feedback loop
Tumor cells metabolize more glucose to lactate in aerobic or hypoxic conditions than non-tumor cells. Pyruvate kinase isoenzyme type M2 (PKM2) is crucial for tumor cell aerobic glycolysis. We established a role for let-7a/c-Myc/hnRNPA1/PKM2 signaling in glioma cell glucose metabolism. PKM2 depletion via siRNA inhibits cell proliferation and aerobic glycolysis in glioma cells. C-Myc promotes up-regulation of hnRNPA1 expression, hnRNPA1 binding to PKM pre-mRNA, and the subsequent formation of PKM2. This pathway is downregulated by the microRNA let-7a, which functionally targets c-Myc, whereas hnRNPA1 blocks the biogenesis of let-7a to counteract its ability to downregulate the c-Myc/hnRNPA1/PKM2 signaling pathway. The down-regulation of c-Myc/hnRNPA1/PKM2 by let-7a is verified using a glioma xenograft model. These results suggest that let-7a, c-Myc and hnRNPA1 from a feedback loop, thereby regulating PKM2 expression to modulate glucose metabolism of glioma cells. These findings elucidate a new pathway mediating aerobic glycolysis in gliomas and provide an attractive potential target for therapeutic intervention.
8872564
β-Catenin signaling initiates the activation of astrocytes and its dysregulation contributes to the pathogenesis of astrocytomas
Astrocytes are the most abundant cell of the CNS and demonstrate contact inhibition in which a nonproliferative, nonmotile cellular state is achieved once stable intercellular contacts are formed between mature cells. Cellular injury disrupts these intercellular contacts, causing a loss of contact inhibition and the rapid initiation of healing. Dysregulation of the molecular pathways involved in this process is thought to lead to an aggressive cellular state associated with neoplasia. We investigated whether a comparable correlation exists between the response of astrocytes to injury and the malignant phenotype of astrocytomas. We discovered that the loss of contact inhibition plays a critical role in the initiation and regulation of reactive astrocytes in the healing of wounds. In particular, injury of the astrocytes interrupts and destabilizes the cadherin-catenin complexes at the cell membrane leading to nuclear translocation of β-catenin and characteristic changes associated with the activation of astrocytes. Similar signaling pathways are found to be active—but dysregulated—in astrocytomas. Inhibition of β-catenin signaling diminished both the response of astrocytes to injury and induction of the malignant phenotype of astrocytomas. The findings shed light on a unique mechanism associated with the pathogenesis of astrocytomas and provide a model for the loss of contact inhibition that may broadly apply to understanding the mechanisms of tissue repair and tumorigenesis in the brain.
7194806
Tyrosine Phosphorylation Inhibits PKM2 to Promote the Warburg Effect and Tumor Growth
Tyrosine phosphorylation of pyruvate kinase M2 gives tumor cells a metabolic advantage. A Malignant Metabolic Switch Cancer cells show aberrant metabolism, consuming more glucose than do healthy cells and producing lactate even in the presence of abundant oxygen, rather than shifting to oxidative phosphorylation. This phenomenon is called the Warburg effect, after Otto Warburg, who described it many years ago. Building on recent research implicating inhibition of the M2 isoform of the glycolytic enzyme pyruvate kinase (PKM2) by phosphotyrosine binding as critical to the Warburg effect—and tumorigenesis—Hitosugi et al. explored the role of signaling from oncogenic forms of the fibroblast growth factor receptor type 1 (FGFR1) in mediating this metabolic switch. They found that FGFR1, a receptor tyrosine kinase, phosphorylated a tyrosine residue (Y105) on PKM2 itself. Further analysis revealed that this tyrosine residue was commonly phosphorylated in human cancers and that a mutant form of PKM2 lacking this tyrosine residue inhibited both “Warburg metabolism” and tumor growth. They thus propose that phosphorylation of PKM2 by oncogenic tyrosine kinases provides the very phosphotyrosine that binds to and inhibits PKM2 to induce the Warburg effect and promote tumor growth. The Warburg effect describes a pro-oncogenic metabolism switch such that cancer cells take up more glucose than normal tissue and favor incomplete oxidation of glucose even in the presence of oxygen. To better understand how tyrosine kinase signaling, which is commonly increased in tumors, regulates the Warburg effect, we performed phosphoproteomic studies. We found that oncogenic forms of fibroblast growth factor receptor type 1 inhibit the pyruvate kinase M2 (PKM2) isoform by direct phosphorylation of PKM2 tyrosine residue 105 (Y105). This inhibits the formation of active, tetrameric PKM2 by disrupting binding of the PKM2 cofactor fructose-1,6-bisphosphate. Furthermore, we found that phosphorylation of PKM2 Y105 is common in human cancers. The presence of a PKM2 mutant in which phenylalanine is substituted for Y105 (Y105F) in cancer cells leads to decreased cell proliferation under hypoxic conditions, increased oxidative phosphorylation with reduced lactate production, and reduced tumor growth in xenografts in nude mice. Our findings suggest that tyrosine phosphorylation regulates PKM2 to provide a metabolic advantage to tumor cells, thereby promoting tumor growth.
14191904
VEGF Promotes Proliferation of Human Glioblastoma Multiforme Stem-Like Cells through VEGF Receptor 2
Cancer stem-like cells, which have been described as tumor-initiating cells or tumor-propagating cells, play a crucial role in our fundamental understanding of glioblastoma multiforme (GBM) and its recurrence. GBM is a lethal cancer, characterized by florid vascularization and aberrantly elevated vascular endothelial growth factor (VEGF). VEGF promotes tumorigenesis and angiogenesis of human GBM stem-like cells (GBSCs). However, whether and how VEGF contributes to GBSCs proliferation remain largely uncertain. In this study, human GBSCs were isolated from surgical specimens of glioblastoma and cultured in medium favored for stem cell growth. Neural Colony-Forming Cell Assay and ATP assay were performed to measure GBSC proliferation under normoxia (20% O2) and hypoxia (1% O2). Our observations demonstrate that exogenous VEGF stimulates GBSC proliferation in a dose-dependent manner via VEGF Receptor 2 (VEGFR2); while VEGF Receptor 1 (VEGFR1) has a negative feedback effect on VEGFR2 when cells were exposed to higher concentration of VEGF. These results suggest that suppressing VEGFR2-dependent GBSC proliferation is a potentially therapeutic strategy in GBM.
23481028
Inactivation of PI3K/AKT signaling inhibits glioma cell growth through modulation of β-catenin-mediated transcription
Aberrant Wnt/β-catenin signaling contributes to the development of many cancers, including glial tumorigenesis. While cross talk between the Wnt/β-catenin and PI3K/AKT signaling pathways has been proposed, the impact of PI3K/AKT inhibition on β-catenin signaling in glioma remains unknown. In the present study, we report decreased cell proliferation and invasive ability upon the LY294002-induced inhibition of PI3K in both U251 and LN229 human glioblastoma cells in vitro. Pharmacologic inhibition of PI3K resulted in the downregulation of several members of the β-catenin pathway, including Fra-1, c-Myc, and cyclin D1. Downregulation impacted β-catenin-mediated transcription, as LY294002 decreased β-catenin/TCF transcriptional activity, determined by the reporter assay. Similar results were observed in vivo, as intratumoral injection of LY294002 downregulated the expression of the components of the β-catenin pathway and delayed tumor growth in nude mice harboring subcutaneous LN229 xenografts. These results suggest that the PI3K/AKT signaling pathway regulates glioma cell proliferation, in part via repression of the Wnt/β-catenin pathway.
638930
The antiproliferative effect of indomethacin-loaded lipid-core nanocapsules in glioma cells is mediated by cell cycle regulation, differentiation, and the inhibition of survival pathways
Despite recent advances in radiotherapy, chemotherapy, and surgical techniques, glioblastoma multiforme (GBM) prognosis remains dismal. There is an urgent need for new therapeutic strategies. Nanoparticles of biodegradable polymers for anticancer drug delivery have attracted intense interest in recent years because they can provide sustained, controlled, and targeted delivery. Here, we investigate the mechanisms involved in the antiproliferative effect of indomethacin-loaded lipid-core nanocapsules (IndOH-LNC) in glioma cells. IndOH-LNC were able to reduce cell viability by inducing apoptotic cell death in C6 and U138-MG glioma cell lines. Interestingly, IndOH-LNC did not affect the viability of primary astrocytes, suggesting that this formulation selectively targeted transformed cells. Mechanistically, IndOH-LNC induced inhibition of cell growth and cell-cycle arrest to be correlated with the inactivation of AKT and β-catenin and the activation of GSK-3β. IndOH-LNC also induced G0/G1 and/or G2/M phase arrest, which was accompanied by a decrease in the levels of cyclin D1, cyclin B1, pRb, and pcdc2 and an increase in the levels of Wee1 CDK inhibitor p21WAF1. Additionally, IndOH-LNC promoted GBM cell differentiation, observed as upregulation of glial fibrillary acidic protein (GFAP) protein and downregulation of nestin and CD133. Taken together, the crosstalk among antiproliferative effects, cell-cycle arrest, apoptosis, and cell differentiation should be considered when tailoring pharmacological interventions aimed at reducing glioma growth by using formulations with multiples targets, such as IndOH-LNC.
24590496
High β-catenin/Tcf-4 activity confers glioma progression via direct regulation of AKT2 gene expression.
Recent data suggest that the β-catenin/Tcf-4 signaling pathway plays an important role in human cancer tumorigenesis. However, the mechanism of β-catenin/Tcf-4 signaling in tumorigenesis is poorly understood. In this study, we show that Tcf-4 protein levels were significantly elevated in high-grade gliomas in comparison with low-grade gliomas and that Tcf-4 levels correlated with levels of AKT2. Reduction of β-catenin/Tcf-4 activity inhibited glioma cell proliferation and invasion in vitro and tumor growth in vivo. This effect of β-catenin/Tcf-4 activity was mediated by AKT2, and in vivo binding of β-catenin/Tcf-4 to the AKT2 promoter was validated using the chromatin immunoprecipitation assay and luciferase reporter assays. Taken together, we have demonstrated that Tcf-4 is associated with glioma progression and that AKT2 is a new member of the genes that are regulated by β-catenin/Tcf-4.
21438599
Differentiation of SWO-38 glioma cells induced by CDA-2 is mediated by peroxisome proliferator-activated receptor γ
Glioma remains one of the most lethal human tumors in spite of the progress in radiotherapy, chemotherapy, and surgical techniques. Cell differentiation agent-2 (CDA-2) is an extraction from healthy human urine consisting of primary organic acids and peptides, and it has been demonstrated to inhibit growth and induce differentiation in glioma and other cell lines. However, the mechanism remains unclear. Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptors (NHRs) which are involved in cellular differentiation and proliferation. In this study, we investigated if CDA-2 induced differentiation of SWO-38 glioma cells is mediated by PPARγ. CDA-2 induced differentiation of SWO-38 cells was characterized by typical morphological changes, increased expression of GFAP, inhibition of proliferation and G0/G1 cell cycle arrest. CDA-2 also triggered up-regulation of PPARγ, GFAP and PTEN protein and a reduction of COX-2 protein. However, the effects of CDA-2 on SWO-38 cells could be partly reversed by GW9662, an irreversible PPARγ antagonist. Our investigation demonstrated that CDA-2 could be a potential drug for tumor differentiation therapy, and activation of the PPARγ pathway might be a crucial factor in glioma differentiation induced by CDA-2.
3449415
Cyclooxygenase-2 in glioblastoma multiforme.
Glioblastoma multiforme (GBM) represents the most prevalent brain primary tumor, yet there is a lack of effective treatment. With current therapies, fewer than 5% of patients with GBM survive more than 5 years after diagnosis. Mounting evidence from epidemiological studies reveals that the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) is correlated with reduced incidence of GBM, suggesting that cyclooxygenase-2 (COX-2) and its major product within the brain, prostaglandin E2 (PGE2), are involved in the development and progression of GBM. Here, we highlight our current understanding of COX-2 in GBM proliferation, apoptosis, invasion, angiogenesis, and immunosuppression by focusing on recent in vitro and in vivo experimental data. We also discuss the feasibility of COX-2 as a therapeutic target for GBM in light of the latest human studies.
8019067
Aberrantly activated Cox-2 and Wnt signaling interact to maintain cancer stem cells in glioblastoma.
Glioblastoma recurrence after aggressive therapy typically occurs within six months, and patients inevitably succumb to their disease. Tumor recurrence is driven by a subpopulation of cancer stem cells in glioblastoma (glioblastoma stem-like cells, GSCs), which exhibit resistance to cytotoxic therapies, compared to their non-stem-cell counterparts. Here, we show that the Cox-2 and Wnt signaling pathways are aberrantly activated in GSCs and interact to maintain the cancer stem cell identity. Cox-2 stimulates GSC self-renewal and proliferation through prostaglandin E2 (PGE2), which in turn activates the Wnt signaling pathway. Wnt signaling underlies PGE2-induced GSC self-renewal and independently directs GSC self-renewal and proliferation. Inhibition of PGE2 enhances the effect of temozolomide on GSCs, but affords only a modest survival advantage in a xenograft model in the setting of COX-independent Wnt activation. Our findings uncover an aberrant positive feedback interaction between the Cox-2/PGE2 and Wnt pathways that mediates the stem-like state in glioblastoma.
17565615
NSAIDs Inhibit Tumorigenesis, but How?
Numerous epidemiologic studies have reported that the long-term use of nonsteroidal anti-inflammatory drugs (NSAID) is associated with a significant decrease in cancer incidence and delayed progression of malignant disease. The use of NSAIDs has also been linked with reduced risk from cancer-related mortality and distant metastasis. Certain prescription-strength NSAIDs, such as sulindac, have been shown to cause regression of precancerous lesions. Unfortunately, the extended use of NSAIDs for chemoprevention results in potentially fatal side effects related to their COX-inhibitory activity and suppression of prostaglandin synthesis. Although the basis for the tumor growth–inhibitory activity of NSAIDs likely involves multiple effects on tumor cells and their microenvironment, numerous investigators have concluded that the underlying mechanism is not completely explained by COX inhibition. It may therefore be possible to develop safer and more efficacious drugs by targeting such COX-independent mechanisms. NSAID derivatives or metabolites that lack COX-inhibitory activity, but retain or have improved anticancer activity, support this possibility. Experimental studies suggest that apoptosis induction and suppression of β-catenin–dependent transcription are important aspects of their antineoplastic activity. Studies show that the latter involves phosphodiesterase inhibition and the elevation of intracellular cyclic GMP levels. Here, we review the evidence for COX-independent mechanisms and discuss progress toward identifying alternative targets and developing NSAID derivatives that lack COX-inhibitory activity but have improved antineoplastic properties. Clin Cancer Res; 20(5); 1104–13. ©2013 AACR.
37115465
Exisulind induction of apoptosis involves guanosine 3',5'-cyclic monophosphate phosphodiesterase inhibition, protein kinase G activation, and attenuated beta-catenin.
Sulindac sulfone (exisulind), although a nonsteroidal anti-inflammatory drug derivative, induces apoptosis in tumor cells by a mechanism that does not involve cyclooxygenase inhibition. SW480 colon tumor cells contain guanosine 3',5'-monophosphate (cGMP) phosphodiesterase (PDE) isoforms of the PDE5 and PDE2 gene families that are inhibited by exisulind and new synthetic analogues. The analogues maintain rank order of potency for PDE inhibition, apoptosis induction, and growth inhibition. A novel mechanism for exisulind to induce apoptosis is studied involving sustained increases in cGMP levels and cGMP-dependent protein kinase (PKG) induction not found with selective PDE5 or most other PDE inhibitors. Accumulated beta-catenin, shown to be a substrate for PKG, is decreased by exisulind, suggesting a mechanism to explain apoptosis induction in neoplastic cells harboring adenomatous polyposis coli gene mutations.
9308546
Sulindac and its metabolites inhibit invasion of glioblastoma cells via down‐regulation of Akt/PKB and MMP‐2
Non‐steroidal anti‐inflammatory drug (NSAID), sulindac has chemopreventive and anti‐tumorigenic properties, however, the molecular mechanism of this inhibitory action has not been clearly defined. The Akt/protein kinase B, serine/threonine kinase is well known as an important mediator of many cell survival signaling pathways. In the present study, we demonstrate that down‐regulation of Akt is a major effect of anti‐invasiveness property of sulindac and its metabolites in glioblastoma cells. Myristoylated Akt (MyrAkt) transfected U87MG glioblastoma cells showed increase invasiveness, whereas DN‐Akt transfected cells showed decrease invasiveness indicating that Akt potently promoted glioblastoma cell invasion. MMP‐2 promoter and enzyme activity were up‐regulated in Akt kinase activity dependent manner. Sulindac and its metabolites down‐regulated Akt phosphorylation, inhibited MMP‐2 production, and significantly inhibited invasiveness of human glioblastoma cells. In addition, sulindac and LY294002, a selective inhibitor of phosphoinositide 3‐kinase (PI3K), synergistically inhibited the invasion of glioblastoma cells. Furthermore, only celecoxib showed Akt phosphorylation reduction and an anti‐invasivness in glioblastoma cells, whereas aspirin, ketoprofen, ketorolac, and naproxen did not. In conclusion, our results provide evidence that down‐regulation of Akt pathway and MMP‐2 may be one of the mechanisms by which sulindac and its metabolites inhibit glioblastoma cell invasion. © 2004 Wiley‐Liss, Inc.
23242667
Eicosanoids and cancer
Eicosanoids, including prostaglandins and leukotrienes, are biologically active lipids that have been implicated in various pathological processes, such as inflammation and cancer. This Review highlights our understanding of the intricate roles of eicosanoids in epithelial-derived tumours and their microenvironment. The knowledge of how these lipids orchestrate the complex interactions between transformed epithelial cells and the surrounding stromal cells is crucial for understanding tumour evolution, progression and metastasis. Understanding the molecular mechanisms underlying the role of prostaglandins and other eicosanoids in cancer progression will help to develop more effective cancer chemopreventive and/or therapeutic agents.
26518480
Low-Dose Chemotherapy in Combination with COX-2 Inhibitors and PPAR-Gamma Agonists in Recurrent High-Grade Gliomas – A Phase II Study
Objectives: Combined treatment approaches targeting tumor as well as other cells contributing to tumor progression may control chemorefractory malignancies. Methods: A phase II trial was initiated to analyze the activity of continuously administered pioglitazone and rofecoxib combined with low-dose chemotherapy (capecitabine or temozolomide) in patients with high-grade gliomas (glioblastoma or anaplastic glioma). Results: Fourteen patients were evaluable for response and toxicity. Major side effects were palmoplantar erythema, edema and motor neuropathy grade 3. Disease stabilizations lasting longer than 3 months were noted in 4 of 14 patients (29%). Clinical responses did not correspond to immunohistochemical staining for cyclooxygenase 2, peroxisome proliferator-activated receptor-γ and CD31. Discussion: The study demonstrates that this novel regimen is moderately active and well tolerated in patients with high-grade gliomas. As a comparably small proportion of patients responded, the regimen might only be suitable for a subset of highly selected patients.
22591210
Inhibition of PDE5 by Sulindac Sulfide Selectively Induces Apoptosis and Attenuates Oncogenic Wnt/β-Catenin–Mediated Transcription in Human Breast Tumor Cells
Nonsteroidal anti-inflammatory drugs (NSAID) such as sulindac sulfide (SS) display promising antineoplastic properties, but toxicities resulting from COX inhibition limit their clinical use. Although COX inhibition is responsible for the anti-inflammatory activity of SS, recent studies suggest that phosphodiesterase (PDE) 5 inhibition and activation of cyclic guanosine monophosphate (cGMP) signaling are closely associated with its ability to induce apoptosis of tumor cells. However, the underlying mechanisms responsible for apoptosis induction, factors that influence sensitivity of tumor cells to SS, and the importance of PDE5 for breast tumor cell growth have not been established. Here we show that SS can induce apoptosis of breast tumor cells, which predominantly rely on PDE5 for cGMP hydrolysis but not normal mammary epithelial cells, which rely on PDE isozymes other than PDE5 for cGMP hydrolysis. Inhibition of PDE5 and activation of protein kinase G (PKG) by SS was associated with increased β-catenin phosphorylation, decreased β-catenin mRNA and protein levels, reduced β-catenin nuclear localization, decreased T-cell factor/lymphoid enhancer factor (Tcf/Lef) promoter activity, and decreased expression of Wnt/β-catenin–regulated proteins. Suppression of PDE5 with siRNA or known PDE5 inhibitors was sufficient to selectively induce apoptosis and attenuate β-catenin–mediated transcription in breast tumor cells with minimal effects on normal mammary epithelial cells. These findings provide evidence that SS induces apoptosis of breast tumor cells through a mechanism involving inhibition of PDE5 and attenuation of oncogenic Wnt/β-catenin–mediated transcription. We conclude that PDE5 represents a novel molecular target for the discovery of safer and more efficacious drugs for breast cancer chemoprevention. Cancer Prev Res; 4(8); 1275–84. ©2011 AACR.
46719630
New NSAID targets and derivatives for colorectal cancer chemoprevention.
Clinical and preclinical studies provide strong evidence that nonsteroidal anti-inflammatory drugs (NSAIDs) can prevent numerous types of cancers, especially colorectal cancer. Unfortunately, the depletion of physiologically important prostaglandins due to cyclooxygenase (COX) inhibition results in potentially fatal toxicities that preclude the long-term use of NSAIDs for cancer chemoprevention. While studies have shown an involvement of COX-2 in colorectal tumorigenesis, other studies suggest that a COX-independent target may be at least partially responsible for the antineoplastic activity of NSAIDs. For example, certain NSAID derivatives have been identified that do not inhibit COX-2 but have demonstrated efficacy to suppress carcinogenesis with potential for reduced toxicity. A number of alternative targets have also been reported to account for the tumor cell growth inhibitory activity of NSAIDs, including the inhibition of cyclic guanosine monophosphate phosphodiesterases (cGMP PDEs), generation of reactive oxygen species (ROS), the suppression of the apoptosis inhibitor protein, survivin, and others. Here, we review several promising mechanisms that are being targeted to develop safer and more efficacious NSAID derivatives for colon cancer chemoprevention.
10701409
New insights into the role of COX 2 in inflammation
Cyclo-oxygenase (COX) is responsible for the synthesis of bioactive prostanoids, the inhibition of which serves as the basis for the mode of action of clinically used nonsteroidal anti-inflammatory drugs. While there were suggestions as early as the 1970s that an inducible isoform of COX exists, it was only in the early 1990s that COX 2 was identified, cloned and sequenced. Not surprisingly, this new isoform was expressed at sites of inflammation and reported to contribute to the inflammatory response. Recently, however, evidence is emerging to suggest that COX 2 also has anti-inflammatory properties. In this review, the two faces of COX 2 are examined, with emphasis on its role in regulating inflammatory resolution, including possible mechanisms of action
1039962
Mechanisms of peroxisome proliferator activated receptor γ regulation by non-steroidal anti-inflammatory drugs
Non-steroidal anti-inflammatory drugs (NSAIDs) display anti-inflammatory, antipyretic and analgesic properties by inhibiting cyclooxygenases and blocking prostaglandin production. Previous studies, however, suggested that some NSAIDs also modulate peroxisome proliferator activated receptors (PPARs), raising the possibility that such off target effects contribute to the spectrum of clinically relevant NSAID actions. In this study, we set out to understand how peroxisome proliferator activated receptor-γ (PPARγ/PPARG) interacts with NSAIDs using X-ray crystallography and to relate ligand binding modes to effects on receptor activity. We find that several NSAIDs (sulindac sulfide, diclofenac, indomethacin and ibuprofen) bind PPARγ and modulate PPARγ activity at pharmacologically relevant concentrations. Diclofenac acts as a partial agonist and binds to the PPARγ ligand binding pocket (LBP) in typical partial agonist mode, near the β-sheets and helix 3. By contrast, two copies of indomethacin and sulindac sulfide bind the LBP and, in aggregate, these ligands engage in LBP contacts that resemble agonists. Accordingly, both compounds, and ibuprofen, act as strong partial agonists. Assessment of NSAID activities in PPARγ-dependent 3T3-L1 cells reveals that NSAIDs display adipogenic activities and exclusively regulate PPARγ-dependent target genes in a manner that is consistent with their observed binding modes. Further, PPARγ knockdown eliminates indomethacin activities at selected endogenous genes, confirming receptor-dependence of observed effects. We propose that it is important to consider how individual NSAIDs interact with PPARγ to understand their activities, and that it will be interesting to determine whether high dose NSAID therapies result in PPAR activation.
13908566
Systematic review: interactions between aspirin, and other nonsteroidal anti-inflammatory drugs, and polymorphisms in relation to colorectal cancer
Nonsteroidal anti‐inflammatory drugs (NSAIDs) include aspirin (acetylsalicylic acid, ASA). Long‐term use of NSAIDs has been associated with lowered risk of colorectal cancer (CRC), but the use is hampered by adverse effects. Also, the anti‐carcinogenic effects of NSAIDs are incompletely understood. Understanding biological effects of NSAIDs may help developing new preventive medical strategies.
7531081
Anti-inflammatory properties of curcumin, a major constituent of Curcuma longa: a review of preclinical and clinical research.
Curcuma longa (turmeric) has a long history of use in Ayurvedic medicine as a treatment for inflammatory conditions. Turmeric constituents include the three curcuminoids: curcumin (diferuloylmethane; the primary constituent and the one responsible for its vibrant yellow color), demethoxycurcumin, and bisdemethoxycurcumin, as well as volatile oils (tumerone, atlantone, and zingiberone), sugars, proteins, and resins. While numerous pharmacological activities, including antioxidant and antimicrobial properties, have been attributed to curcumin, this article focuses on curcumin's anti-inflammatory properties and its use for inflammatory conditions. Curcumin's effect on cancer (from an anti-inflammatory perspective) will also be discussed; however, an exhaustive review of its many anticancer mechanisms is outside the scope of this article. Research has shown curcumin to be a highly pleiotropic molecule capable of interacting with numerous molecular targets involved in inflammation. Based on early cell culture and animal research, clinical trials indicate curcumin may have potential as a therapeutic agent in diseases such as inflammatory bowel disease, pancreatitis, arthritis, and chronic anterior uveitis, as well as certain types of cancer. Because of curcumin's rapid plasma clearance and conjugation, its therapeutic usefulness has been somewhat limited, leading researchers to investigate the benefits of complexing curcumin with other substances to increase systemic bioavailability. Numerous in-progress clinical trials should provide an even deeper understanding of the mechanisms and therapeutic potential of curcumin.
34093108
Investigating the therapeutic role and molecular biology of curcumin as a treatment for glioblastoma
Objectives: Despite the aggressive standard of care for patients with glioblastoma multiforme, survival rates typically do not exceed 2 years. Therefore, current research is focusing on discovering new therapeutics or rediscovering older medications that may increase the overall survival of patients with glioblastoma. Curcumin, a component of the Indian natural spice, turmeric, also known for its antioxidant and anti-inflammatory properties, has been found to be an effective inhibitor of proliferation and inducer of apoptosis in many cancers. The goal of this study was to investigate the expanded utility of curcumin as an antiglioma agent. Methods: Using the PubMed MeSH database, we conducted a systematic review of the literature to include pertinent studies on the growth inhibitory effects of curcumin on glioblastoma cell lines based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Results: A total of 19 in vitro and five in vivo studies were analyzed. All of the studies indicated that curcumin decreased glioblastoma cell viability through various pathways (i.e. decrease in prosurvival proteins such as nuclear factor κB, activator protein 1, and phosphoinositide 3 kinase, and upregulation of apoptotic pathways like p21, p53, and executor caspase 3). Curcumin treatment also increased animal survival compared with control groups. Conclusions: Curcumin inhibits proliferation and induces apoptosis in certain subpopulations of glioblastoma tumors, and its ability to target multiple signaling pathways involved in cell death makes it an attractive therapeutic agent. As such, it should be considered as a potent anticancer treatment. Further experiments are warranted to elucidate the use of a bioavailable form of curcumin in clinical trials.
38046255
The targets of curcumin.
Curcumin (diferuloylmethane), an orange-yellow component of turmeric or curry powder, is a polyphenol natural product isolated from the rhizome of the plant Curcuma longa. For centuries, curcumin has been used in some medicinal preparation or used as a food-coloring agent. In recent years, extensive in vitro and in vivo studies suggested curcumin has anticancer, antiviral, antiarthritic, anti-amyloid, antioxidant, and anti-inflammatory properties. The underlying mechanisms of these effects are diverse and appear to involve the regulation of various molecular targets, including transcription factors (such as nuclear factor-kB), growth factors (such as vascular endothelial cell growth factor), inflammatory cytokines (such as tumor necrosis factor, interleukin 1 and interleukin 6), protein kinases (such as mammalian target of rapamycin, mitogen-activated protein kinases, and Akt) and other enzymes (such as cyclooxygenase 2 and 5 lipoxygenase). Thus, due to its efficacy and regulation of multiple targets, as well as its safety for human use, curcumin has received considerable interest as a potential therapeutic agent for the prevention and/or treatment of various malignant diseases, arthritis, allergies, Alzheimer's disease, and other inflammatory illnesses. This review summarizes various in vitro and in vivo pharmacological aspects of curcumin as well as the underlying action mechanisms. The recently identified molecular targets and signaling pathways modulated by curcumin are also discussed here.
22212970
Curcumin for the Treatment of Glioblastoma.
Glioblastoma multiforme is a highly aggressive primary cancer of the brain associated with a poor prognosis. Modest increases in survival can sometimes be achieved with the use of temozolomide and radiation therapy after surgery, but second-line therapy after recurrence has a limited efficacy. Curcumin has demonstrated promising results against this form of cancer in experimental models. The reported activity of curcumin against cancer stem cells, a major cause of glioblastoma resistance to therapy, and its ability to augment the apoptotic effects of ceramides, suggest it would have a synergistic effect with cytotoxic chemotherapy agents currently used in second-line therapy, such as lomustine.
4833922
Prospective of curcumin, a pleiotropic signalling molecule from Curcuma longa in the treatment of Glioblastoma.
GBM (Glioblastoma) is the most malignant human brain tumor with median survival of one year. The treatment involves surgery, radiotherapy and adjuvant chemotherapy mostly with the alkylation agents such as temozolomide (TMZ). Dietary polyphenol curcumin, isolated from the rhizome of the Curcuma longa (turmeric), has emerged as remarkable anti-cancer agent in the treatment of various peripheral cancers such as blood, lymphomas, multiple myeloma, melanoma as well as skin, lung, prostate, breast, ovarian, bladder, liver, gastrointestinal tract, pancreatic and colorectal epithelial cancers with a pleiotropic mode of action and also showed promise in alleviation of GBM. In this review, the mechanism of anticancer effect of curcumin in GBM has been discussed extensively. The clinical safety and pharmacokinetics of curcumin has been scrutinized to combat the challenges for the treatment of GBM.
37610640
Biological Properties of Curcumin-Cellular and Molecular Mechanisms of Action
Curcuminoids, a group of phenolic compounds isolated from the roots of Curcuma longa (Zingiberaceae), exhibit a variety of beneficial effects on health and on events that help in preventing certain diseases. A vast majority of these studies were carried out with curcumin (diferuloyl methane), which is a major curcuminoid. The most detailed studies using curcumin include anti-inflammatory, antioxidant, anticarcinogenic, antiviral, and antiinfectious activities. In addition, the wound healing and detoxifying properties of curcumin have also received considerable attention. As a result of extensive research on the therapeutic properties of curcumin, some understanding on the cellular, molecular, and biochemical mechanism of action of curcumin is emerging. These findings are summarized in this review.
20549194
Antioxidant and anti-inflammatory properties of curcumin.
Curcumin, a yellow pigment from Curcuma longa, is a major component of turmeric and is commonly used as a spice and food-coloring agent. It is also used as a cosmetic and in some medical preparations. The desirable preventive or putative therapeutic properties of curcumin have also been considered to be associated with its antioxidant and anti-inflammatory properties. Because free-radical-mediated peroxidation of membrane lipids and oxidative damage of DNA and proteins are believed to be associated with a variety of chronic pathological complications such as cancer, atherosclerosis, and neurodegenerative diseases, curcumin is thought to play a vital role against these pathological conditions. The anti-inflammatory effect of curcumin is most likely mediated through its ability to inhibit cyclooxygenase-2 (COX-2), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS). COX-2, LOX, and iNOS are important enzymes that mediate inflammatory processes. Improper upregulation of COX-2 and/or iNOS has been associated with the pathophysiology of certain types of human cancer as well as inflammatory disorders. Because inflammation is closely linked to tumor promotion, curcumin with its potent anti-inflammatory property is anticipated to exert chemopreventive effects on carcinogenesis. Hence, the past few decades have witnessed intense research devoted to the antioxidant and anti-inflammatory properties of curcumin. In this review, we describe both antioxidant and anti-inflammatory properties of curcumin, the mode of action of curcumin, and its therapeutic usage against different pathological conditions.
15787606
Dietary Curcumin Attenuates Glioma Growth in a Syngeneic Mouse Model by Inhibition of the JAK1,2/STAT3 Signaling Pathway
Purpose: Glioblastomas are the most common and most deadly primary brain tumors. Here, we evaluated the chemotherapeutic effect of the natural polyphenol curcumin on glioma cells in vitro and in vivo using an immunocompetent orthotopic mouse model. Experimental Design: Curcumin's effects on proliferation, cell cycle, migration, invasion, JAK/STAT3 signaling, STAT3 target gene expression, and STAT3C rescue experiments were determined in murine glioma cell lines in vitro. Therapeutic effects of curcumin in vivo were evaluated in tumor-bearing mice fed a Western-type diet fortified with curcumin (0.05%, w/w) and in control animals. Tumor growth patterns and survival were evaluated by immunohistochemistry, morphometric analyses, and Kaplan–Meier plots. Results: In vitro, curcumin inhibited JAK1,2/STAT3 tyrosine-phosphorylation in a dose-dependent fashion in murine glioma cell lines. Real-time RT-PCR revealed that curcumin downregulated transcription of the STAT3 target genes c-Myc, MMP-9, Snail, and Twist, and of the proliferation marker Ki67. Curcumin dose-dependently suppressed cell proliferation by inducing a G2/M phase arrest. In wound healing and Matrigel invasion assays, curcumin treatment resulted in a dose-dependent attenuation of the glioma cells' migratory and invasive behavior, which could be rescued by constitutively active STAT3C. In vivo, curcumin intake reduced the growth and midline crossing of intracranially implanted tumors and proliferation of tumor cells ensuing in significant long-term survival compared with control diet. Conclusion: This preclinical study shows that curcumin is capable of suppressing malignant glioma growth in vitro and in vivo. Our data suggest that the pharmacologically safe agent curcumin holds promise for clinical application in glioma therapy. Clin Cancer Res; 16(23); 5781–95. ©2010 AACR.
25608220
Activation of PPAR{gamma} by curcumin inhibits Moser cell growth and mediates suppression of gene expression of cyclin D1 and EGFR.
Colorectal cancer is a leading cause of cancer-related morbidity and mortality in the United States. Curcumin, the yellow pigment in turmeric, possesses inhibitory effects on growth of a variety of tumor cells by reducing cell proliferation and inducing apoptosis. Effects of the peroxisome proliferator-activated receptor-gamma (PPARgamma) on stimulating cell differentiation and on inducing cell cycle arrest have attracted attention from the perspective of treatment and prevention of cancer. The aim of this study was to elucidate the mechanisms by which curcumin inhibits colon cancer cell growth. In the present report, we observed that curcumin, in a dose-dependent manner, inhibited the growth of Moser cells, a human colon cancer-derived cell line, and stimulated the trans-activating activity of PPARgamma. Further studies demonstrated that activation of PPARgamma was required for curcumin to inhibit Moser cell growth. Activation of PPARgamma mediated curcumin suppression of the expression of cyclin D1, a critical protein in the cell cycle, in Moser cells. In addition, curcumin blocked EGF signaling by inhibiting EGF receptor (EGFR) tyrosine phosphorylation and suppressing the gene expression of EGFR mediated by activation of PPARgamma. In addition to curcumin reduction of the level of phosphorylated PPARgamma, inhibition of cyclin D1 expression played a major and significant role in curcumin stimulation of PPARgamma activity in Moser cells. Taken together, our results demonstrated for the first time that curcumin activation of PPARgamma inhibited Moser cell growth and mediated the suppression of the gene expression of cyclin D1 and EGFR. These results provided a novel insight into the roles and mechanisms of curcumin in inhibition of colon cancer cell growth and potential therapeutic strategies for treatment of colon cancer.
24538297
Curcumin suppresses cell proliferation through inhibition of the Wnt/β-catenin signaling pathway in medulloblastoma.
Recently, the survival rate of medulloblastoma patients has greatly improved; yet, patients undergoing current treatment regimes suffer from serious therapy-related side-effects. The aim of the present study was to investigate the anticancer effects of curcumin on medulloblastoma cells by testing its capacity to suppress proliferation and regulate the Wnt/β-catenin pathway. In the present study, cell proliferation was determined by MTT assay. Cell cycle was observed by flow cytometry. The changes in the Wnt/β-catenin pathway were analyzed by immunofluorescence, western blot analysis and RT-PCR. Curcumin treatment resulted in a dose- and time-dependent inhibition of proliferation in the medulloblastoma cell line. Curcumin treatment arrested the cell-cycle at the G2/M phase. Furthermore, curcumin treatment led to activation of GSK-3β, reduced expression of β-catenin and its downstream target cyclin D1. The attenuation of the Wnt/β‑catenin pathway was due to the loss of nuclear β-catenin. In conclusion, curcumin can inhibit cell growth by suppressing the Wnt/β-catenin signaling pathway, and it has the potential to be developed as a therapeutic agent for medulloblastoma.
45848514
Roles of the Akt/mTOR/p70S6K and ERK1/2 Signaling Pathways in Curcumin-Induced Autophagy
Curcumin has a potent anticancer effect and is a promising new therapeutic strategy. We previously demonstrated that curcumin induced non-apoptotic autophagic cell death in malignant glioma cells in vitro and in vivo. This compound inhibited the Akt/mammalian target of rapamycin/p70 ribosomal protein S6 kinase pathway and activated the extracellular signal-regulated kinases 1/2 thereby inducing autophagy. Interestingly, activation of the first pathway inhibited curcumin-induced autophagy and cytotoxicity, whereas inhibition of the latter pathway inhibited curcumin-induced autophagy and induced apoptosis, thus augmenting the cytotoxicity of curcumin. These results imply that these two autophagic pathways have opposite effects on curcumin’s cytotoxicity. However, inhibition of nuclear factor κB, which is the main target of curcumin for its anticancer effect, was not observed in malignant glioma cells. These results suggest that autophagy but not nuclear factor κB plays a central role in curcumin anticancer therapy and warrant further investigation toward application in patients with malignant gliomas. Here, we discuss the therapeutic role of two autophagic pathways influenced by curcumin. Addendum to: Evidence That Curcumin Suppresses the Growth of Malignant Gliomas in Vitro and in Vivo through Induction of Autophagy: Role of Akt and Extracellular Signal-Regulated Kinase Signaling Pathways H. Aoki, Y. Takada, S. Kondo, R. Sawaya, B. B. Aggarwal and Y. Kondo Mol Pharmacol 2007; 72:29-39
8849967
Developments in antipsychotic therapy with regard to hypotheses for schizophrenia
The typical antipsychotic drugs like chlorpromazine and haloperidol were discovered by serendipity in the 1950s. A number of so-called “me too” drugs with similar chemical structures and modes of action were marketed in the subsequent years. The first atypical antipsychotic, clozapine, was an exception because it lacked some of the pharmacological properties of the typical antipsychotics related to the extrapyrimidal motor system. This unique feature of clozapine significantly broadened understanding of the mode of action of antipsychotics, and created new hypotheses for schizophrenia. Hypothesis-orientated development of new drugs was only recently initiated. Abnormalities of the immune system in schizophrenia are being increasingly discussed: shifts in the levels of T helper cells subsets 1 and 2 (Th1 and Th2) have been observed, and studies with risperidone and the cyclooxengenase (COX2) inhibitor celecoxib as an add-on therapy have provided very promising results. The glutamate N-methyl-D-aspartate (NMDA) receptors have also been investigated in relation to neuropathological abnormalities in prefrontal areas of the brain of patients with schizophrenia. This may lead to new technologies like artificial networks related to the glutamate NMDA receptor system. New molecular biological techniques used in pharmacogenomics and proteomics offer new and exciting directions for future drug developments.
34971773
Cytotoxic effects of antipsychotic drugs implicate cholesterol homeostasis as a novel chemotherapeutic target
The reported reduction in cancer risk in those suffering from schizophrenia may be because antipsychotic medications have antineoplastic effects. In this study, 6 antipsychotic agents with a range of structural and pharmacological properties (reserpine, chlorpromazine, haloperidol, pimozide, risperidone and olanzapine), were screened for their effect on the viability of cell lines derived from lymphoblastoma, neuroblastoma, non‐small cell lung cancer and breast adenocarcinoma. We aimed to determine if antipsychotic drugs in general possess cancer‐specific cytotoxic potential, and whether it can be attributed to a common mode of action. With the exception of risperidone, all drugs tested displayed selective inhibition of the viability of cancer cell lines compared with normal cells. Using Affymetrix expression microarrays and quantitative real‐time polymerase chain reaction, we found that for the antipsychotic drugs, olanzapine and pimozide, cytotoxicity appeared to be mediated via effects on cholesterol homeostasis. The role of cholesterol metabolism in the selective cytotoxicity of these drugs was supported by demonstration of their increased lethality when coadministered with a cholesterol synthesis inhibitor, mevastatin. Also, pimozide and olanzapine showed accelerating cytotoxic effects from 12 to 48 hr in time course studies, mirroring the time‐dependent onset of cytotoxicity induced by the amphiphile, U18666A. On the basis of these results, we concluded that the Class II cationic amphiphilic properties of antipsychotic drugs contribute to their cytotoxic effects by acting on cholesterol homeostasis and altering the biophysical properties of cellular membranes, and that drugs affecting membrane‐related cholesterol pathways warrant further investigation as potential augmentors of standard cancer chemotherapy.
19658185
Olanzapine inhibits the proliferation and induces the differentiation of glioma stem-like cells through modulating the Wnt signaling pathway in vitro.
OBJECTIVE
Olanzapine, a D2/5-HT2 antagonist, is often used as an atypical antipsychotic drug in clinical. Previous research has found its new pharmacological influence on enhancing the differentiation of neural stem cells (NSCs) to oligodendrocyte-like cells (ODLCs). Glioblastomas are associated with poor prognoses owing to the glioma stem-like cells (GSLCs), which have a great many of similarities with adult NSCs. Hence, in this article, we aim to study the effects and associated mechanisms of olanzapine on GSLCs derived from human U87MG glioblastoma cell lines.


MATERIALS AND METHODS
The methyl thiazolyl tetrazolium (MTT) colorimetric assay was conducted to investigate the effects of olanzapine on cell viability of GSLCs. Flow cytometric analysis was applied to study the cell cycle dynamics of GSLCs and Cell Counting Kit-8 (CCK-8) was used to further investigate the proliferation of GSLCs after treated with olanzapine or dimethyl sulfoxide (DMSO) for 48 h. Cell differentiation assay was carried out to study the differentiation of GSLCs and then Image-Pro Plus image analysis was used to measure the protrusion length of the differentiated cells. Furthermore, the confocal [Ca2+]c measurement was conducted to observe the influence of olanzapine on the opening function of Ca2+ channel. After the application of olanzapine for 48 h, RT-PCR was conducted to measure mRNA levels of calcium-sensing receptor (CaSR) and stromal interaction molecule 1 (STIM1), and Western blotting analysis was carried out to examine the expression of myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), CaSR protein, STIM1 protein and β-catenin protein.


RESULTS
Our results demonstrated that olanzapine inhibited the proliferation of GSLCs by arresting cell cycle in G0/G1 phase and facilitated the differentiation of such cells to ODLCs. After treated with olanzapine for 48 h, cells were very sensitive to 100 mM K+ stimulation, with increased spontaneous calcium wave. We also found olanzapine increased the protein expression of MBP and GFAP. In addition, the mRNA transcription and protein expression of CaSR and STIM1 were enhanced after treated with olanzapine for 48h, while the protein expression of β-catenin was suppressed.


CONCLUSIONS
Our results suggest that olanzapine modulates the Wnt signaling pathway through activating the Ca2+ pathway and restraining the β-catenin pathway, leading to the differentiation of GSLCs to ODLCs. It provides exciting prospects that olanzapine might be a new novel chemotherapeutic modality targeting GSLCs for the treatment of glioblastomas.
3893654
Promoting oligodendroglial-oriented differentiation of glioma stem cell: a repurposing of quetiapine for the treatment of malignant glioma
As a major contributor of chemotherapy resistance and malignant recurrence, glioma stem cells (GSCs) have been proposed as a target for the treatment of gliomas. To evaluate the therapeutic potential of quetiapine (QUE), an atypical antipsychotic, for the treatment of malignant glioma, we established mouse models with GSCs-initiated orthotopic xenograft gliomas and subcutaneous xenograft tumors, using GSCs purified from glioblastoma cell line GL261. We investigated antitumor effects of QUE on xenograft gliomas and its underlying mechanisms on GSCs. Our data demonstrated that (i) QUE monotherapy can effectively suppress GSCs-initiated tumor growth; (ii) QUE has synergistic effects with temozolomide (TMZ) on glioma suppression, and importantly, QUE can effectively suppress TMZ-resistant (or -escaped) tumors generated from GSCs; (iii) mechanistically, the anti-glioma effect of QUE was due to its actions of promoting the differentiation of GSCs into oligodendrocyte (OL)-like cells and its inhibitory effect on the Wnt/β-catenin signaling pathway. Together, our findings suggest an effective approach for anti-gliomagenic treatment via targeting OL-oriented differentiation of GSCs. This also opens a door for repurposing QUE, an FDA approved drug, for the treatment of malignant glioma.
24876214
Adipokines in inflammation and metabolic disease
The worldwide epidemic of obesity has brought considerable attention to research aimed at understanding the biology of adipocytes (fat cells) and the events occurring in adipose tissue (fat) and in the bodies of obese individuals. Accumulating evidence indicates that obesity causes chronic low-grade inflammation and that this contributes to systemic metabolic dysfunction that is associated with obesity-linked disorders. Adipose tissue functions as a key endocrine organ by releasing multiple bioactive substances, known as adipose-derived secreted factors or adipokines, that have pro-inflammatory or anti-inflammatory activities. Dysregulated production or secretion of these adipokines owing to adipose tissue dysfunction can contribute to the pathogenesis of obesity-linked complications. In this Review, we focus on the role of adipokines in inflammatory responses and discuss their potential as regulators of metabolic function.
4755176
Adiponectin: Regulation of its production and its role in human diseases
Adiponectin is a white and brown adipose tissue hormone, also known as gelatin-binding protein-28 (GBP28), AdipoQ, adipocyte complement-related protein (ACRP30), or apM1. Adiponectin circulates in the bloodstream in trimeric, hexameric, and high-molecular-mass species, while different forms of adiponectin have been found to play distinct roles in the balance of energy homoeostasis. Adiponectin is an insulin sensitizing hormone that exerts its action through its receptors AdipoR1, AdipoR2, and T-cadherin. AdipoR1 is expressed abundantly in muscle, whereas AdipoR2 is predominantly expressed in the liver. Adiponectin is inversely proportional to obesity, diabetes, and other insulin-resistant states. In this review we present the current findings regarding the regulation of its production and several new findings pertaining to its biological effects. Adiponectin enhances AMPK and the PPARα pathway in the liver and skeletal muscle. Adiponectin increases fatty acids oxidation, which lowers circulating free fatty acids and prevents insulin resistance. Adiponectin has been reported to exert an antiatherosclerotic effect. It inhibits macrophage activation and foam cell accumulation, while it also augments endothelial nitrous oxide production and protects the vasculature by reducing platelet aggregation and vasodilation. Apart from causing metabolic dysfunction, adiponectin deficiency may also contribute to coronary heart disease, steatohepatitis, insulin resistance, nonalcoholic fatty liver disease, and a wide array of cancers. In this study, we present ample evidence that adiponectin mediates multiple molecular pathways. We therefore support the concept that it shows distinct potential for being of therapeutic value in the treatment of obesity related diseases, ranging from metabolic syndrome to malignancies.
23902904
Adiponectin in inflammatory and immune-mediated diseases.
Circulating levels of adiponectin (APN) are reduced in obesity and associated comorbidities, with inflammation playing an important role in downregulating APN production. In contrast to obesity and metabolic disease, elevated systemic and local levels of APN are present in patients with inflammatory and immune-mediated diseases, including autoimmune and pulmonary conditions, heart and kidney failure, viral hepatitis, organ transplantation and perhaps critical illness. A positive association between inflammation and APN is usually reported in inflammatory/immune pathologies, in contrast with the negative correlation typical of metabolic disease. This review discusses the role of APN in modulation of inflammation and immunity and the potential mechanisms leading to increased levels of APN in inflammatory/immune diseases, including modification of adipose tissue physiology; relative contribution of different tissues and adipose depots; hormonal, pharmacological, nutritional and life style factors; the potential contribution of the microbiota as well as the role of altered APN clearance and release from T-cadherin-associated tissue reservoirs. Potential reasons for some of the apparently contradictory findings on the role of APN as a modulator of immunity and inflammation are also discussed, including a comparison of types of recombinant APN used for in vitro studies and strain-dependent differences in the phenotype of APN KO mice.
46449088
Leptin promotes metastasis by inducing an epithelial-mesenchymal transition in A549 lung cancer cells.
Leptin, an adipocyte-derived cytokine associated with obesity, has been reported to participate in carcinogenesis. Epithelial-mesenchymal transition (EMT) is also considered as a key event in tumor metastasis. The aim of this study is to investigate the mechanism of leptin in the promotion of EMT leading to metastasis in A549 lung cancer cells. We investigated the effect of leptin on migration of A549 cells using wound healing and transwell assays. The incidence of EMT in A549 cells was examined by real-time PCR and immunofluorescence staining. The expression of TGF-β in A549 cells was detected by real-time PCR, and blocking of TGF-β in A549 cells was achieved by siRNA techniques. Additional work was performed using 100 patient samples, which included samples from 50 patients diagnosed with lung cancer and an additional 50 patients diagnosed with lung cancer with metastatic bone lesions. Leptin expression was measured using immunohistochemistry techniques. We demonstrated that leptin can effectively enhance the metastasis of human lung cancer A549 cell line using both wound healing and transwell assays. We also found the incidence of EMT in A549 cells after leptin exposure. Furthermore, we detected the expression of TGF-β in A549 cells, which had been reported to play an important role in inducing EMT. We showed that leptin can significantly upregulate TGF-β at both the mRNA and protein levels in A549 cells. Using siRNA to block the expression of TGF-β in A549 cells, we confirmed the role of TGF-β in the promotion of metastasis and induction of EMT. Furthermore, we found that in patient samples leptin was present at higher levels in samples associated with diagnosis of lung cancer bone metastases tissue than lung cancer tissue. Our results indicated that leptin promoted the metastasis of A549 human lung cancer cell lines by inducing EMT in a TGF-β-dependent manner.
3879405
Adiponectin in relation to malignancies: a review of existing basic research and clinical evidence.
Adiponectin, an adipocyte-secreted hormone that plays an important role in diabetes and cardiovascular disease, may also be of importance in the development and progression of several malignancies. Circulating adiponectin concentrations, which are determined mainly by genetic factors, nutrition, and adiposity, are lower in patients with breast, endometrial, prostate, and colon cancer. It has thus been proposed that adiponectin may be a biological link between obesity (especially central obesity) and increased cancer risk. Adiponectin may influence cancer risk through its well-recognized effects on insulin resistance, but it is also plausible that adiponectin acts on tumor cells directly. Several cancer cell types express adiponectin receptors that may mediate the effects of adiponectin on cellular proliferation. Herein, we review recent evidence supporting a role of serum adiponectin concentrations as a novel risk factor and possible diagnostic marker for obesity-related malignancies, including cancers of the breast, endometrium, colon, and prostate. Further studies are needed to fully elucidate the potential role of adiponectin in cancer diagnostics and therapeutics.
23427199
Adiponectin inhibits Wnt co-receptor, Lrp6, phosphorylation and β-catenin signaling.
Adiponectin is a pleiotropic adipokine implicated in obesity, metabolic syndrome and cardiovascular disease. Recent studies have identified adiponectin as a negative regulator of tissue fibrosis. Wnt/β-catenin signaling has also been implicated in metabolic syndrome and can promote tissue fibrosis, but the extent to which adiponectin cross-regulates Wnt/β-catenin signaling is unknown. Using primary human dermal fibroblasts and recombinant purified proteins, we show that adiponectin can limit β-catenin accumulation and downstream gene activation by inhibiting Lrp6 phosphorylation, a key activation step in canonical Wnt signaling. Inhibition of Wnt3a-mediated Lrp6 phospho-activation is relatively rapid (e.g., by 30 min), and is not dependent on established adiponectin G-protein coupled receptors, AdipoR1 and R2, suggesting a more direct relationship to Lrp6 signaling. In contrast, the ability of adiponectin to limit Wnt-induced and baseline collagen production in fibroblasts requires AdipoR1/R2. These results suggest the possibility that the pleiotropic effects of adiponectin may be mediated through distinct cell surface receptor complexes. Accordingly, we propose that the anti-fibrotic activity of adiponectin may be mediated through AdipoR1/R2 receptors, while the ability of adiponectin to inhibit Lrp6 phospho-activation may be relevant to other recently established roles for Lrp6 signaling in glucose metabolism and metabolic syndrome.
22959182
Adiponectin as Novel Regulator of Cell Proliferation in Human Glioblastoma
Adiponectin (Acrp30) is an adipocyte‐secreted hormone with pleiotropic metabolic effects, whose reduced levels were related to development and progression of several malignancies. We looked at the presence of Acrp30 receptors in human glioblastomas (GBM), hypothesizing a role for Acrp30 also in this untreatable cancer. Here we demonstrate that human GBM express Acrp30 receptors (AdipoR1 and AdipoR2), which are often co‐expressed in GBM samples (70% of the analyzed tumors). To investigate the effects of Acrp30 on GBM growth, we used human GBM cell lines U87‐MG and U251, expressing both AdipoR1 and AdipoR2 receptors. In these cells, Acrp30 treatment inhibits DNA synthesis and cell proliferation rate, inducing arrest in G1 phase of the cell cycle. These effects were correlated to a sustained activation of ERK1/2 and Akt kinases, upon Acrp30 treatment. Our results suggest that Acrp30 may represent a novel endogenous negative regulator of GBM cell proliferation, to be evaluated for the possible development of novel pharmacological approaches. J. Cell. Physiol. 229: 1444–1454, 2014. © 2014 Wiley Periodicals, Inc.
21333144
Peroxisome proliferator activated receptors at the crossroad of obesity, diabetes, and pancreatic cancer.
Pancreatic ductal adenocarcinoma (PDAC) is the fourth cause of cancer death with an overall survival of 5% at five years. The development of PDAC is characteristically associated to the accumulation of distinctive genetic mutations and is preceded by the exposure to several risk factors. Epidemiology has demonstrated that PDAC risk factors may be non-modifiable risks (sex, age, presence of genetic mutations, ethnicity) and modifiable and co-morbidity factors related to the specific habits and lifestyle. Recently it has become evident that obesity and diabetes are two important modifiable risk factors for PDAC. Obesity and diabetes are complex systemic and intertwined diseases and, over the years, experimental evidence indicate that insulin-resistance, alteration of adipokines, especially leptin and adiponectin, oxidative stress and inflammation may play a role in PDAC. Peroxisome proliferator activated receptor-γ (PPARγ) is a nuclear receptor transcription factor that is implicated in the regulation of metabolism, differentiation and inflammation. PPARγ is a key regulator of adipocytes differentiation, regulates insulin and adipokines production and secretion, may modulate inflammation, and it is implicated in PDAC. PPARγ agonists are used in the treatment of diabetes and oxidative stress-associated diseases and have been evaluated for the treatment of PDAC. PPARγ is at the cross-road of diabetes, obesity, and PDAC and it is an interesting target to pharmacologically prevent PDAC in obese and diabetic patients.
6824218
Molecular Pathways: Adiponectin and Leptin Signaling in Cancer
The increasing percentage of obese individuals in the population and its independent association of increased risk for the development of cancer have heightened the necessity to understand the molecular mechanisms that underlie this connection. The deregulation of adipokines in the setting of obesity and their impact on cancer progression and metastasis is one such area of research. Adipokines are bioactive proteins that mediate metabolism, inflammation, angiogenesis, and proliferation. Altered levels of adipokines or their cognate receptors in cancers can ultimately lead to an imbalance in downstream molecular pathways. Discovery of adipokine receptors in various cancers has highlighted the potential for novel therapeutic targets. Leptin and adiponectin represent two adipokines that elicit generally opposing molecular effects. Epidemiologic studies have highlighted associations between increased serum leptin levels and increased tumor growth, whereas adiponectin exhibits an inverse correlation with cancer development. This review addresses the current level of understanding of molecular pathways activated by adiponectin and leptin to identify the areas of intervention and facilitate advancement in the field. Clin Cancer Res; 19(8); 1926–32. ©2013 AACR.
25494657
Improved therapeutic effect on malignant glioma with adenoviral suicide gene therapy combined with temozolomide
Malignant gliomas (MGs) are cancers with poor prognosis and limited therapeutic options. Herpes Simplex virus-1 thymidine kinase expressed from adenoviruses with prodrug ganciclovir (TK/GCV) is the best-characterized suicide gene therapy, whereas temozolomide (TMZ) is the first-line chemotherapy for MG. However, the potential of their combination has not been studied thoroughly. The aim of this study was to evaluate the therapeutic response of this combination and to study whether addition of valproic acid (VPA) could benefit the treatment outcome. Efficacies of different treatments were first studied in vitro in BT4C rat MG cells. Therapeutic assessment in vivo was done in an immunocompetent rat MG model for treatment efficacy and toxicity. In vitro, VPA was able to significantly enhance cytotoxicity and increase adenovirus-mediated transduction efficiency up to sevenfold. In vivo, rats receiving TK/GCV+TMZ had notably smaller tumors and enhanced survival (P<0.001) in comparison with control rats. However, VPA was not able to further enhance the treatment response in vivo. Leukocytopenia and thrombocytopenia were the major side effects. We conclude that careful optimization of the treatment schedules and doses of individual therapies are necessary to achieve an optimal therapeutic effect with TK/GCV+TMZ combination. No further in vivo benefit with VPA was observed.
206424803
Synergistic inhibitory effect of sulforaphane and 5‐fluorouracil in high and low metastasis cell lines of salivary gland adenoid cystic carcinoma
The present study aimed to evaluate the growth‐inhibitory effect of sulforaphane (SFN) and a traditional chemotherapy agent, 5‐fluorouracil (5‐Fu), against the proliferation of salivary gland adenoid cystic carcinoma high metastatic cell line (ACC‐M) and low metastasis cell line (ACC‐2). Furthermore, the expression of nuclear factor kappa B (NF‐κB) which induces resistance to anticancer chemotherapeutic agents was also detected. The combination effect of SFN and 5‐Fu was quantitatively determined using the method of median effect principle and the combination index. The nuclear NF‐κB p65 expression after treatment with the SFN‐5‐Fu combination was also evaluated by western blot analysis. The ACC‐M and ACC‐2 cells exhibited relative resistant to 5‐Fu. Treatment ACCs cells with SFN and 5‐Fu in combination, led to synergistic inhibition on cell growth and a decreased expression in nuclear NF‐κB p65 protein. This synergistic inhibitory effect was more significant in ACC‐M cells, which is associated with the greatly decreased expression of NF‐κB p65 (almost 5‐fold) after the combination treatment. Our results demonstrate synergism between SFN and 5‐Fu at higher doses against the ACC‐M and ACC‐2 cells, which was associated with the decreased expression of nuclear NF‐κB p65 protein. Copyright © 2008 John Wiley & Sons, Ltd.
7026004
Hypoxia-Inducible Factor-1 Inhibition in Combination with Temozolomide Treatment Exhibits Robust Antitumor Efficacy In vivo
Purpose: Inhibiting hypoxia-inducible factor-1 (HIF-1) represents a unique mechanism for cancer therapy. It is conceived that HIF-1 inhibitors may synergize with many classes of cancer therapeutic agents, such as angiogenesis inhibitors and cytotoxic drugs, to achieve a more robust tumor response. However, these hypotheses have not been rigorously tested in tumor models in vivo. The present study was carried out to evaluate the antitumor efficacy of combining HIF-1 inhibition with angiogenesis inhibitors or cytotoxic agents. Experimental Design: Using a D54MG-derived tumor model that allows knockdown of HIF-1α on doxycycline treatment, we examined the tumor responses to chemotherapeutic agents, including the angiogenesis inhibitor ABT-869 and cytotoxic agents 1,3-bis(2-chloroethyl)-1-nitrosourea and temozolomide, in the presence or absence of an intact HIF-1 pathway. Results: Surprisingly, inhibiting HIF-1 in tumors treated with the angiogenesis inhibitor ABT-869 did not produce much added benefit compared with ABT-869 treatment alone, suggesting that the combination of an angiogenesis inhibitor with a HIF-1 inhibitor may not be a robust therapeutic regimen. In contrast, the cytotoxic drug temozolomide, when used in combination with HIF-1α knockdown, exhibited a superadditive and likely synergistic therapeutic effect compared with the monotherapy of either treatment alone in the D54MG glioma model. Conclusions: Our results show that the DNA alkylating agent temozolomide exhibits robust antitumor efficacy when used in combination with HIF-1 inhibition in D54MG-derived tumors, suggesting that the combination of temozolomide with HIF-1 inhibitors might be an effective regimen for cancer therapy. In addition, our results also show that the RNA interference–based inducible knockdown model can be a valuable platform for further evaluation of the combination treatment of other cancer therapeutics with HIF-1 inhibition.
23646947
Combining bevacizumab with temozolomide increases the antitumor efficacy of temozolomide in a human glioblastoma orthotopic xenograft model.
PURPOSE
The aims of the present work were to investigate the in vitro and in vivo antiangiogenic effects of chronic temozolomide treatment on various glioma models and to demonstrate whether bevacizumab (Avastin) increased the therapeutic benefits contributed by temozolomide in glioma.


EXPERIMENTAL DESIGN
The expression levels of various antiangiogenic factors in four glioma cell lines were evaluated after chronic in vitro treatment with temozolomide by Western blot. Proliferation and migration assays were performed on human endothelial cells incubated with supernatants of glioma cells treated with and without temozolomide. Orthotopic glioma models were used to evaluate the antiangiogenic effects of temozolomide in vivo and the therapeutic benefits of different temozolomide treatment schedules used alone or in combination with bevacizumab.


RESULTS
Temozolomide, a proautophagic and proapoptotic drug, decreased the expression levels of HIF-1alpha, ID-1, ID-2, and cMyc in the glioma models investigated, all of which playing major roles in angiogenesis and the switch to hypoxic metabolism. These changes could be, at least partly, responsible for the impairment of angiogenesis observed in vitro and in vivo. Moreover, combining bevacizumab with temozolomide increased the survival of glioma-bearing mice in comparison to each compound administered alone.


CONCLUSIONS
In addition to the numerous mechanisms of action already identified for temozolomide, we report here that it also exerts antitumor effects by impairing angiogenic processes. We further emphasize that bevacizumab, which is an antiangiogenic drug with a different mechanism of action, could be useful in combination with temozolomide to increase the latter's therapeutic benefit in glioma patients.
44439019
Resveratrol Enhances the Antitumor Effects of Temozolomide in Glioblastoma via ROS‐dependent AMPK‐TSC‐mTOR Signaling Pathway
Resveratrol has been regarded as a promising candidate for cancer prevention and treatment. The present study was to investigate the impact of resveratrol on the antitumor effects of temozolomide (TMZ), a standard treatment regiment of glioblastoma (GBM), in vitro and in vivo.
24528738
Inhibition of Bevacizumab-induced Epithelial-Mesenchymal Transition by BATF2 Overexpression Involves the Suppression of Wnt/β-Catenin Signaling in Glioblastoma Cells.
BACKGROUND/AIM
Bevacizumab (BV) has been used for the treatment of recurrent glioblastoma. However, it also induces epithelial-mesenchymal transition (EMT) in glioblastoma cells, which compromises its efficacy. BATF2 (basic leucine zipper ATF-like transcription factor 2), a multi-target transcriptional repressor, has been found to suppress cancer development partly through inhibition of Wnt/β-catenin singling. The roles of BATF2 and Wnt/β-catenin signaling in BV-induced EMT in glioblastoma cells were investigated in this study.


MATERIALS AND METHODS
BV was used to treat U87MG cells, and TOP/FOP FLASH luciferase reporters were employed to determine the activity of Wnt/β-catenin signaling. EMT markers were detected with quantitative reverse transcription-PCR and western blotting. Immunofluorescence (IF) was used to determine the compartmentation of β-catenin. Wound-healing, TransWell and ECIS assays were used to analyze cell adhesion, invasion and migration.


RESULTS
BV induced EMT phenotype in U87MG cells, and BATF2 overexpression significantly inhibited BV-induced EMT with suppression of Wnt/β-catenin signaling.


CONCLUSION
Our findings expanded the understanding of the role of BATF2 in tumors, and also suggested a potential of using BATF2 as a therapeutic target to hinder bevacizumab induced EMT in glioblastoma.
8360534
miR-125b inhibitor enhance the chemosensitivity of glioblastoma stem cells to temozolomide by targeting Bak1
Temozolomide (TMZ) is a promising chemotherapeutic agent for treating glioblastomas. However, resistance develops quickly with a high frequency. Glioblastoma stem cells (GSCs) causing resistance to drug therapy were considered to be one of key factors. The mechanisms underlying GSCs resistance to TMZ are not fully understood. MicroRNAs (miRNAs) have emerged to play important roles in tumorigenesis and drug resistance. Previous study showed that miR-125b was necessary for GSCs fission and for making stem cells insensitive to chemotherapy. Thus, exploring the functions and mechanisms of miR-125b action on TMZ-treated GSCs would be valuable. In this study, we found that miR-125b was up-regulated in TMZ-resistant cells, inhibition of which caused a marked increase of TMZ-induced cytotoxicity and apoptosis and a subsequent decrease in the resistance to TMZ in GSCs. Moreover, we demonstrated that the pro-apoptotic Bcl-2 antagonist killer 1 (Bak1) was a direct target of miR-125b. Down-regulation of Bak1 inhibited TMZ-induced apoptosis and led to an increased resistance to TMZ. Restoring Bak1 expression recovered TMZ sensitivity on GSCs. Taken together; our data strongly support an important role for miR-125b on conferring TMZ resistance through targeting Bak1 expression.
3948589
ICAT inhibits glioblastoma cell proliferation by suppressing Wnt/β-catenin activity.
Inhibitor of β-catenin and T-cell factor (ICAT) is a key component of Wnt/β-catenin signaling. ICAT blocks the formation of the β-catenin/TCF complex and has been demonstrated to be involved in embryonic development and carcinogenesis. As an inhibitor of canonical Wnt signaling, ICAT was presumed to be a tumor-suppressor gene. However, the ICAT functions in human glioma remain unknown. In this study, we evaluated the expression of ICAT in 305 human glioma tissues and found that negative ICAT expression correlated with higher grade glioma and poor survival in patients with glioma. Then we transfected glioma cells with ICAT plasmid. Western blotting showed an increased ICAT protein expression level in glioma cells. MTT assay, flow cytometry and cell invasion assay were used to detect cell proliferation, cell cycle distribution, apoptosis and invasion. Our studies confirmed that ICAT inhibits glioma cell proliferation and invasion, and it induces cell apoptosis and cell cycle progression arrest. Besides, ICAT slowed down tumor growth in a glioblastoma xenograft model. Therefore, our study demonstrates that ICAT may serve as a tumor-suppressor in human glioma suggesting a promising direction for targeting therapy in glioma.
522028
STAT3 Inhibition Overcomes Temozolomide Resistance in Glioblastoma by Downregulating MGMT Expression
Glioblastoma multiforme (GBM) is one of the most aggressive human tumors with a poor prognosis. Current standard treatment includes chemotherapy with the DNA-alkylating agent temozolomide concomitant with surgical resection and/or irradiation. However, a number of cases are resistant to temozolomide-induced DNA damage due to elevated expression of the DNA repair enzyme O6-methylguanine-DNA methyltransferase (MGMT). Here, we show that upregulation of both MGMT and STAT3 was accompanied with acquisition of temozolomide resistance in the GBM cell line U87. Inactivation of STAT3 by inhibitor or short hairpin RNA (shRNA) downregulated MGMT expression in GBM cell lines. MGMT upregulation was not observed by the treatment of interleukin (IL)-6 which is a strong activator of STAT3. Contrarily, forced expressed MGMT could be downregulated by STAT3 inhibitor which was partially rescued by the proteasome inhibitor, MG132, suggesting the STAT3-mediated posttranscriptional regulation of the protein levels of MGMT. Immunohistochemical analysis of 44 malignant glioma specimens showed significant positive correlation between expression levels of MGMT and phosphorylated STAT3 (p-STAT3; P < 0.001, r = 0.58). Importantly, the levels of both MGMT and p-STAT3 were increased in the recurrence compared with the primary lesion in paired identical tumors of 12 cases. Finally, we showed that STAT3 inhibitor or STAT3 knockdown potentiated temozolomide efficacy in temozolomide-resistant GBM cell lines. Therefore, STAT3 inhibitor might be one of the candidate reagents for combination therapy with temozolomide for patients with temozolomide-resistant GBM. Mol Cancer Ther; 11(6); 1289–99. ©2012 AACR.
14074940
Preclinical and clinical evaluation of sulforaphane for chemoprevention in the breast.
Consumers of higher levels of Brassica vegetables, particularly those of the genus Brassica (broccoli, Brussels sprouts and cabbage), reduce their susceptibility to cancer at a variety of organ sites. Brassica vegetables contain high concentrations of glucosinolates that can be hydrolyzed by the plant enzyme, myrosinase, or intestinal microflora to isothiocyanates, potent inducers of cytoprotective enzymes and inhibitors of carcinogenesis. Oral administration of either the isothiocyanate, sulforaphane, or its glucosinolate precursor, glucoraphanin, inhibits mammary carcinogenesis in rats treated with 7,12-dimethylbenz[a]anthracene. In this study, we sought to determine whether sulforaphane exerts a direct chemopreventive action on animal and human mammary tissue. The pharmacokinetics and pharmacodynamics of a single 150 mumol oral dose of sulforaphane were evaluated in the rat mammary gland. We detected sulforaphane metabolites at concentrations known to alter gene expression in cell culture. Elevated cytoprotective NAD(P)H:quinone oxidoreductase (NQO1) and heme oxygenase-1 (HO-1) gene transcripts were measured using quantitative real-time polymerase chain reaction. An observed 3-fold increase in NQO1 enzymatic activity, as well as 4-fold elevated immunostaining of HO-1 in rat mammary epithelium, provides strong evidence of a pronounced pharmacodynamic action of sulforaphane. In a subsequent pilot study, eight healthy women undergoing reduction mammoplasty were given a single dose of a broccoli sprout preparation containing 200 mumol of sulforaphane. Following oral dosing, sulforaphane metabolites were readily measurable in human breast tissue enriched for epithelial cells. These findings provide a strong rationale for evaluating the protective effects of a broccoli sprout preparation in clinical trials of women at risk for breast cancer.
10143146
Chemoprevention of prostate cancer by d,l-sulforaphane is augmented by pharmacological inhibition of autophagy.
There is a preclinical evidence that the oral administration of d,l-sulforaphane (SFN) can decrease the incidence or burden of early-stage prostate cancer [prostatic intraepithelial neoplasia (PIN)] and well-differentiated cancer (WDC) but not late-stage poorly differentiated cancer (PDC). Because SFN treatment induces cytoprotective autophagy in cultured human prostate cancer cells, the present study tested the hypothesis that chemopreventive efficacy of SFN could be augmented by the pharmacologic inhibition of autophagy using chloroquine (CQ). Incidence of PDC characterized by prostate weight of more than 1 g was significantly lower in the SFN + CQ group than in control (P = 0.004), CQ group (P = 0.026), or SFN group (P = 0.002 by Fisher exact test). Average size of the metastatic lymph node was lower by about 42% in the SFN + CQ group than in control (P = 0.043 by Wilcoxon test). On the other hand, the SFN + CQ combination was not superior to SFN alone with respect to inhibition of incidence or burden of microscopic PIN or WDC. SFN treatment caused in vivo autophagy as evidenced by transmission electron microscopy. Mechanistic studies showed that prevention of prostate cancer and metastasis by the SFN + CQ combination was associated with decreased cell proliferation, increased apoptosis, alterations in protein levels of autophagy regulators Atg5 and phospho-mTOR, and suppression of biochemical features of epithelial-mesenchymal transition. Plasma proteomics identified protein expression signature that may serve as biomarker of SFN + CQ exposure/response. This study offers a novel combination regimen for future clinical investigations for prevention of prostate cancer in humans.
21329536
Sulforaphane as a promising molecule for fighting cancer.
Cancer is a complex disease characterized by multiple genetic and molecular alterations involving transformation, deregulation of apoptosis, proliferation, invasion, angiogenesis, and metastasis. To grow, invade, and metastasize, tumors need host components and primary dysfunction in the tumor microenvironment, in addition to cell dysfunction, can be crucial for carcinogenesis. A great variety of phytochemicals have been shown to be potentially capable of inhibiting and modulating several relevant targets simultaneously and is therefore non-specific. Because of the enormous biological diversity of cancer, this pleiotropism might constitute an advantage. Phytochemicals, in particular diet-derived compounds, have therefore been proposed and applied in clinical trials as cancer chemopreventive/chemotherapeutic agents. Sulforaphane (SFN) is an isothiocyanate found in cruciferous vegetables. SFN has proved to be an effective chemoprotective agent in cell culture, in carcinogen-induced and genetic animal cancer models, as well as in xenograft models of cancer. It promoted potent cytostatic and cytotoxic effects orchestrated by the modulation of different molecular targets. Cell vulnerability to SFN-mediated apoptosis was subject to regulation by cell-cycle-dependent mechanisms but was independent of a mutated p53 status. Moreover, combination of SFN with cytotoxic therapy potentiated the cytotoxic effect mediated by chemotherapy in vitro, thus suggesting its potential therapeutic benefit in clinical settings. Overall, SFN appears to be an effective and safe chemopreventive molecule and a promising tool to fight cancer.
24780825
Sulforaphane enhances temozolomide‐induced apoptosis because of down‐regulation of miR‐21 via Wnt/β‐catenin signaling in glioblastoma
Temozolomide (TMZ) has been widely used in the treatment of glioblastoma (GBM), although inherent or acquired resistance restricts the application. This study was aimed to evaluate the efficacy of sulforaphane (SFN) to TMZ‐induced apoptosis in GBM cells and the potential mechanism. Biochemical assays and subcutaneous tumor establishment were used to characterize the function of SFN in TMZ‐induced apoptosis. Our results revealed that β‐catenin and miR‐21 were concordantly expressed in GBM cell lines, and SFN significantly reduced miR‐21 expression through inhibiting the Wnt/β‐catenin/TCF4 pathway. Furthermore, down‐regulation of miR‐21 enhanced the pro‐apoptotic efficacy of TMZ in GBM cells. Finally, we observed that SFN strengthened TMZ‐mediated apoptosis in a miR‐21‐dependent manner. In conclusion, SFN effectively enhances TMZ‐induced apoptosis by inhibiting miR‐21 via Wnt/β‐catenin signaling in GBM cells. These findings support the use of SFN for potential therapeutic approach to overcome TMZ resistance in GBM treatment.
5135376
Sulforaphane induces differential modulation of mitochondrial biogenesis and dynamics in normal cells and tumor cells.
Antioxidant-based chemotherapy has been intensely debated. Herein, we show that sulforaphane (SFN) induced mitochondrial biogenesis followed by mitochondrial fusion in a kidney cell line commonly used in nephroprotective models. At the same concentration and exposure time, SFN induced cell death in prostate cancer cells accompanied by mitochondrial biogenesis and fragmentation. Stabilization of the nuclear factor E2-related factor-2 (Nrf2) could be associated with these effects in the tumor cell line. An increase in the peroxisome proliferator-activated receptor-γ co-activator-1α (PGC1α) level and a decrease in the hypoxia-inducible factor-1α (HIF1α) level would suggest a possible metabolic shift. The knockdown in the nuclear respiratory factor-1 (NRF1) attenuated the SFN-induced effect on prostate cancer cells demonstrating that mitochondrial biogenesis plays an important role in cell death for this kind of tumor cells. This evidence supports SFN as a potential antineoplastic agent that could inhibit tumor development and could protect normal tissues by modulating common processes.
3082779
SARI inhibits angiogenesis and tumour growth of human colon cancer through directly targeting ceruloplasmin
SARI, also called as BATF2, belongs to the BATF family and has been implicated in cancer cell growth inhibition. However, the role and mechanism of SARI in tumour angiogenesis are elusive. Here we demonstrate that SARI deficiency facilitates AOM/DSS-induced colonic tumorigenesis in mice. We show that SARI is a novel inhibitor of colon tumour growth and angiogenesis in mice. Antibody array and HUVEC-related assays indicate that VEGF has an essential role in SARI-controlled inhibition of angiogenesis. Furthermore, Co-IP/PAGE/mass spectrometry indicates that SARI directly targets ceruloplasmin (Cp), and induces protease degradation of Cp, thereby inhibiting the activity of the HIF-1α/VEGF axis. Tissue microarray results indicate that SARI expression inversely correlates with poor clinical outcomes in colon cancer patients. Collectively, our results indicate that SARI is a potential target for therapy by inhibiting angiogenesis through the reduction of VEGF expression and is a prognostic indicator for patients with colon cancer.
205531655
Inhibition of AP-1 by SARI negatively regulates transformation progression mediated by CCN1
Enhanced expression of the CCN family of secretory integrin-binding proteins correlates with many essential components of the cancerous state, including tumor cell adhesion, proliferation, invasion and migration. Consequently, CCN1 expression is elevated in various cancers, including breast cancer, and its expression directly correlates with poor patient prognosis. Using subtraction–hybridization, combined with induction of cancer cell terminal differentiation, we cloned SARI (suppressor of activator protein (AP)-1, regulated by interferon (IFN)), an IFN-β-inducible, potent tumor suppressor gene that exerts cancer-selective growth inhibitory effects. Forced expression of SARI using an adenovirus (Ad.SARI) inhibits AP-1 function and downregulates CCN1 expression in multiple cancer lineages, resulting in a profound inhibition in anchorage-independent cell growth and tumor cell invasion. Overexpression of SARI reduces CCN1-promoter activity through inhibition of AP-1 binding. Accordingly, SARI selectively blocks expression of the transformed state in rat embryo fibroblast cells that stably overexpress c-Jun. These results illustrate that SARI inhibits AP-1 transactivating factor binding to the cis-element of the CCN1 promoter, possibly through its interaction with c-Jun. Overall, SARI can directly inhibit CCN1-induced transformation by inhibiting the transcription of CCN1, as well as indirectly by inhibiting the expression of c-Jun (and hence blocking AP-1 activity). In these contexts, transformed cells ‘addicted’ to AP-1 activity are rendered susceptible to SARI-mediated inhibition of expression of the transformed phenotype.