ATPS-60COMPREHENSIVE IDENTIFICATION OF GLIOBLASTOMA MULTIFORME THERAPEUTIC TARGETS AND GROWTH SUPPRESSOR GENES USING GENE EDITING

Glioblastoma multiforme (GBM) is the most aggressive and common form of brain cancer in adults and is currently incurable. To identify new therapeutic targets for GBM, we performed genome-wide CRISPR-Cas9 knockout (KO) screens in patient-derived GBM stem-like cells (GSCs) and human neural stem cells (NSCs), non-neoplastic tissue of origin controls. These screens revealed thousands of gene candidates acting to promote or limit expansion of GSCs and NSCs. In vitro and in vivo validation studies revealed several novel therapeutic targets, including the wee1-like kinase, PKMYT1/Myt1. Mechanistic studies revealed that PKMYT1 acts redundantly with WEE1 to facilitate mitosis in NSCs, but that this redundancy is lost in most GBM isolates and in NSCs harboring activated alleles of EGFR and AKT1. In addition to lethal genes, KOs promoting in vitro expansion of NSCs were also examined. For this category, we validated multiple genes, including: ARID1A, ARID1B, CREBBP, EP300, NF2, PDCD10, PTPN14, TAOK1, TGFBR2, and TP53, whose inhibition shortens NSC cell cycle transit times, causing dramatic growth advantages, and, in the case of CREBBP KO, dramatic deregulation of cell cycle gene expression and precocious S-phase entry. Taken together, these results demonstrate the use of CRISPR-Cas9 gene editing to identify novel cancer therapeutic targets and growth suppressor genes in human GBM isolates and NSCs. The results also inform precision medicine approaches for GBM, since most, if not all, candidate therapeutic targets could not be predicted from mutation, CNV, or gene expression analysis of the patient isolates alone.