Abstract A20: Genome-wide RNAi screens in human brain tumor isolates reveal a novel viability requirement for PHF5A

Abstract

Abstract To identify key regulators of human brain tumor maintenance and initiation, we performed multiple genome-wide RNAi screens in patient-derived glioblastoma multiforme (GBM) stem cells (GSCs). These screens identified the PHD-finger domain protein PHF5A as differentially required for GSC expansion gene, as compared to untransformed neural stem cells (NSCs) and fibroblasts. Given PHF5A's known involvement in facilitating interactions between the U2 snRNP complex and ATP-dependent helicases, we examined cancer-specific roles in RNA splicing. We find that in GSCs, but not untransformed controls, PHF5A facilitates recognition of exons with unusual C-rich 3' splice sites in thousands of essential genes. PHF5A knockdown in GSCs, but not untransformed NSCs, astrocytes, or fibroblasts, inhibited splicing of these genes, leading to cell cycle arrest and loss of viability. Notably, pharmacologic inhibition of U2 snRNP activity phenocopied PHF5A knockdown both in GSCs and in multiple genetically transformed cell types, suggesting that a cancer-specific requirement for PHF5A activity may be generalizable to a wide range of cancers. Furthermore, PHF5A inhibition compromises GSC tumor formation in vivo and dramatically inhibits the growth of established GBM patient-derived xenograft tumors. Together, this work demonstrates an additional mechanism for maintaining splicing fidelity in cancer cells and also suggests that PHF5A activity may provide new in-roads for novel anti-GBM therapeutic strategies. Citation Format: Christopher G. Hubert, Robert K. Bradley, Yu Ding, Toledo M. Chad, Kyobi Skutt-Kakaria, Emily J. Girard, Jerry Davison, Jason Berndt, Philip Corrin, Ryan Basom, Jeffery J. Delrow, Thomas Webb, Steven M. Pollard, Jeongwu Lee, James M. Olson, Patrick J. Paddison. Genome-wide RNAi screens in human brain tumor isolates reveal a novel viability requirement for PHF5A. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Synthetic Lethal Approaches to Cancer Vulnerabilities; May 17-20, 2013; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(5 Suppl):Abstract nr A20.