We are studying the effects of papillomavirus oncogenes on cell proliferation and survival to gain new insights into cancer cell growth control. In the preceding funding period, we exploited the ability of the bovine papillomavirus E2 protein to repress expression of HPV E6 and E7 proteins in cervical cancer cells. We showed that HPV oncogene repression rapidly induced a growth-arrested state indistinguishable from replicative senescence, tn the current proposal, we will use this system to continue our dissection of growth control in cervical carcinoma cells, with particular emphasis on studying mechanisms responsible for cellular senescence, an important tumor suppressor mechanism and model of cellular aging. Our overall goals are to explore the relationship between induced senescence in HeLa cervical cancer cells and replicative senescence in primary cells, to identify genes that mediate or inhibit senescence in these settings, and to determine their mechanism of action. We have used DNA oligonucleotide microarrays to identify genes specifically induced or repressed during senescence induced by HPV18 repression in HeLa cells. We will assess the expression of these genes during replicative senescence of normal cells and non-senescent growth arrest. The genes identified in aim 1 as being specifically regulated during induced and replicative senescence, as well as other candidate cellular genes, will be tested for their ability to modulate senescence, and we will characterize their activity in cells. We will use genetic selection strategies to isolate cDNAs that prevent induced senescence following HPV E7 repression in HeLa cervical cancer cells. Finally, we will conduct biochemical and physiological experiments to determine the mechanism of action of genes that modulate senescence. These studies will provide important new information regarding the molecular basis of the processes that restrain uncontrolled cell growth and may suggest new approaches to therapy.
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