PROJECT SUMMARY/ABSTRACT The RAS oncogene is mutated in ~19% of all human cancers. However, targeted therapies specific to tumors with RAS mutations are lacking. To identify novel druggable targets to cancers with mutations in Ras we performed arrayed, kinome focused siRNA phenotypic screening utilizing a set of syngeneic Ras mutant squamous cell carcinoma (SCC) cell lines. Out of 571 kinases tested, Pip4k2c and Pip5k1b were top scoring, ranked 18th and 21st respectively and further, Pip4k2c both showed greater dependency in Ras mutant vs. Ras wild type SCC cells. Pip4k2c and Pik5k1b both generate phosphatidyl inositol 4,5-bisphosphate (PIP2) the substrate for Pik3ca (PI3K) and precursor to phosphatidyl inositol 3,4,5-triphosphate (PIP3), a key mediator of oncogenic Ras signaling. While most drug development attention has focused on PI3K, lack of clinical activity associated with PI3K inhibitors has generated renewed interest in targeting other phosphoinositol kinases. Here we propose to credential Pip4k2c and Pip5k1b as a novel dependencies in both mouse and human Ras mutant SCC cells, will establish the basic outline of its prosurvival function, and will identify key cellular and genetic modifiers of this dependency.

PROJECT NARRATIVE Through a series of unbiased screens, we have identified several genes, including Pip4k2c and Pip5k1b, that are required for survival of cancer cells that carry a mutation Ras, a gene that this commonly mutated in human cancer. Here we propose to characterize the mechanistic basis for the dependency on Pip4k2c and Pip5k1b in Ras mutant cancer cells as first step to credential these genes as candidate drug targets.