We have studied the role of the RB/p16 tumor suppressor pathway in human cancer focusing primarily on the model of lung cancer. We have established that hypermethylation and gene silencing of p16 occurs in 40% of human non-small cell lung cancers and can be reversed by decitabine therapy. At the Surgery Branch with Dr. Schrump we have begun a clinical trial with decitabine to determine clinical response in lung cancer and to test the ability to hypomethylate specific genetic loci in vivo. We have continued to study alterations within RB gene family members in lung cancer and have characterized several novel mutations in small cell lung cancer. We have also examined novel mutant RB alleles from families with low penetrance of familal retinoblastoma to study the molecular basis for low penetrance of familial retinoblastoma and to define more precisely tumor suppressor activities within the RB product. We have demonstrated that many families with low penetrance carry unstable mutant alleles with temperature-sensitive pocket binding activity which suggest a model for the variable frequency of tumor progression in these patients. We are also analyzing lung tumors that develop in an A/J murine colony that carry RB mutant alleles to determine the effect of RB versus p16 inactivation as the initial genetic hit in this mouse lung cancer model. These mice also develop a high frequency of neuroendocrine tumors and we will study the genetic basis of how RB inactivation facilitates the initiation or progression of these tumors. We had previously isolated a unique member of the Hsp70 chaperone family, called Stch, during a screen for RB binding partners. We have now identified a short peptide within Stch that is conserved in the ATPase domain of Hsp70 members and that binds a family of human ubiquitin-like genes. These findings suggest a broader role for the Hsp70-like ATPase family in regulating cell cycle and cell death events and may offer a direct link between protein chaperone activity and the 26S proteasome. - cell cycle, retinoblastoma, lung cancer, tumor suppressor genes, heat shock proteins, neuroendocrine, - Human Tissues, Fluids, Cells, etc.
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