Using Synthetic Lethality to Select Cancer Drug Targets

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DESCRIPTION (provided by applicant): Loss of function tumor suppressor gene (TSG) mutations are common in cancer. Two genes are 'synthetically lethal' if inactivation of either gene alone is compatible with viability but inactivation of both genes leads to death. In theory, the product of a gene that was synthetically lethal to a mutated TSG would be an attractive drug target because its inhibition should kill TSG(-/-) cancer cells but not normal [TSG( +/+)] cells. We have chosen the VHL tumor suppressor gene, which is mutated in the majority of clear cell renal carcinomas, to explore this paradigm further. Importantly, inactivation of the VHL gene product, pVHL, does not grossly affect cell growth in vitro, which might otherwise confound our studies. Moreover, we have multiple matched (isogenic) renal carcinoma cell (RCC) lines that do or do not contain wild-type pVHL as well as VHL(+/+) and VHL (-/-) C. elegans. Cells lacking pVHL overproduce a transcription factor called HIF (hypoxia-inducible factor). Consequently, the transcriptomes of VHL (-/-) RCCs resemble that of hypoxic cells, which are common in solid tumors and known to be relatively chemoresistant. In specific aim 1 we will use chemical biological approaches to look for compounds that selectively kill VHL(-/-) RCCs. Such compounds might then be used as probes to identify their protein targets. In specific aim 2, we will use a genome-wide RNAi approach to identify genes that selectively kill VHL (-/-) C. elegans. These genes would then be interogated in human RCCs Secondary screens will address whether dysregulation of HIF is responsible for differential sensitivity of VHL (-/-) and VHL (+/+) cells in specific aims 1 and 2. These experiments may identify new drug targets for renal carcinoma, in particular, and hypoxia tumor cells, in general. Moreover, they may establish a new paradigm for the selection of anticancer drug targets based on inactivating mutations of TSG.