Human papillomaviruses (HPV) are important etiologic agents for the development of cervical cancer, a major cause of cancer death in women worldwide. However, additional genetic and environmental factors are critical for pathogenesis of this disease. Our studies focus on two major areas: 1) how do HPV oncoproteins E6 and E7 perturb keratinocyte gene expression and 2) identification of additional genetic and environmental factors that enhance HPV-associated carcinogenesis. We have found that the proinflammatory cytokine, tumor necrosis factor (TNF), inhibits growth of normal cervical keratinocytes but stimulates proliferation of HPV-immortalized and cervical carcinoma-derived cell lines. TNF promotes cell cycle progression by increasing expression of HPV-16 E6/E7 RNAs and enhancing activity of cylin dependent kinases. TNF stimulates these changes by increasing transcription and stabilization of RNA for amphiregulin, an epidermal growth factor receptor (EGF-R) ligand. These studies suggest a pathway through which inflammation stimulates growth of HPV-infected keratinocytes. High risk papillomaviruses stimulate growth of keratinocytes and contribute to cervical carcinogenesis. We have found that keratinocytes secrete biologically active TGF-B2 but release only latent, inactive TGF-B1. Expression of HPV-16 E6 or E7 oncoproteins reproducibly reduces secretion of TGF-B2 by 70 to 80%. This reduction is important because similar levels of recombinant TGF-B2 inhibit growth of infected cells by 25 to 60%. These results define a unique mechanism by which HPV-16 E6 and E7 proteins contribute to aberrant growth and gene expression. The EGF-R is over expressed in HPV-associated dysplasias and carcinomas, implying that signaling through this receptor is important in the pathogenesis of HPV-associated malignancy. We have used mice with a targeted disruption of the EGF-R to directly test this hypothesis. HPV-immortal cells that expressed the EGF-R form papillomas when grafted with normal fibroblasts to dorsal skin of nude mice, and some papillomas progress to carcinomas, In contrast, cells from EGF-R null mice form no papillomas or carcinomas. Transfection of HPV- immortalized cells with an activated ras gene, which signals downstream of the EGF-R, induces carcinomas regardless of EGF-R status . EGF-R null cells grow more slowly in vitro and in vivo. These results provide direct evidence that the EGF-R is critical for HPV-associated tumorigenesis and suggest that inhibitors of EGF-R function will be useful for treatment of HPV-associated disease. - cervical cancer, Papillomaviruses, Virus-Cell Interactions, Rb, p, , keratinocyte, TNF, TGF beta, erbB Receptor Family, Ras, - Human Tissues, Fluids, Cells, etc.
NIH ExPorter
NIH ExPorter