Prostate cancer modifies the balance between osteoclasts (bone resorption) and osteoblasts (bone formation) to enhance tumor growth and promote skeletal-related events (SRE), i.e. severe pain and fractures. The majority of advanced prostate cancer patients have tumors metastasize to bone and half reach mortality within 30-35 months. Despite considerable progress, current therapeutics only prolong overall survival by reducing the tumor growth rate and/or delay time to SRE by a few additional months. There remains a critical lack of therapies that can reduce tumor burden while simultaneously restoring the bone. The central growth- promoting pathways for tumor-bone crosstalk involve interleukin (IL-6 and IL-11) and transforming growth factor ? (TGF?) signaling, both of which correlate with advanced disease and poor prognosis. Our laboratory recently developed a gene delivery strategy to express cytokine gene products that can in turn disrupt the IL-6/11 and TGF? signals at distant tumor metastases. We use a nanoplex composed of nuclear-localizing polymer and plasmid DNA and delivery is enhanced by ultrasound (sonodelivery). Using sonodelivery, we have shown that interleukin-27 (IL-27), a natural antagonist of IL-6/11, reduces tumor burden and improves bone homeostasis. We have shown that IL-27 is a multifunctional cytokine that drives antitumor activity through immune-activation and anti-angiogenic mechanisms. Moreover, our lab has identified that IL-27 is a pro-osteogenic factor. Our most recent data indicates that despite its high promise, IL-27 monotherapy still can be improved by the addition of a second therapeutic that can attenuate TGF? signaling. We have observed that the osteogenic protein-1 (OP-1), a natural TGF? antagonist, significantly augments IL-27 efficacy. Our hypothesis is that optimizing delivery and targeting of multifunctional cytokines IL-27 and OP-1 to the tumor/bone microenvironment will disrupt key malignant crosstalk while inducing immune-activation to reduce tumor burden, restore bone, and increase survival. (Aim 1) To achieve therapeutically effective levels of cytokines in serum, we will optimize gene delivery and cytokine secretion from skeletal muscle. (Aim 2) To enhance therapeutic efficacy of cytokines and reduce potential toxicity, we will promote cytokine retention at tumor-bone metastases by ligand-mediated targeting. (Aim 3) To examine the efficacy of IL-27+OP-1 (27OP1) sonodelivery and determine therapeutic applications, we will examine 27OP1 in the context of current chemotherapies. This project leverages the strengths of the team in sonodelivery and biomaterials (Figueiredo, Emrick), tumor/bone microenvironment (Keller and Rowley) and ligand-mediated targeting (Pasqualini). We anticipate this project will provide the foundation for a simple, effective sonodelivery-based intervention that reduces tumor burden while restoring bone and can synergize with current immunomodulatory chemotherapies. This approach is expected to improve bone-metastatic prostate cancer patient morbidity and quality of life and would be applicable to other diseases involving bone/tumor pathology.