DDDR-42. LEVERAGING GENOME-WIDE CRISPR/CAS9 KNOCKOUT DRUG SCREENS TO IDENTIFY SENSITIZERS FOR PROTEOSOME INHIBITORS IN GLIOBLASTOMA

Abstract Glioblastoma (GBM) is the most common primary brain tumor with a poor prognosis despite aggressive treatment. Patient outcomes remain abysmal with 95% of patients relapsing and a median overall survival of 15 months. This necessitates the rapid search for personalized therapeutics and agents to enhance current treatments. One pathway that demonstrates dysregulated functioning is the ubiquitin-proteasome pathway (UPP). Literature has shown that UPP dependent proteolysis remains constitutively upregulated in cancer cells leading to the rapid degradation of proteins that regulate oncogenic pathways. Despite robust preclinical evaluations for the usage of proteasome inhibitors against GBM, most proteasome inhibitors failed in clinical trials, indicating resistance. We conducted an unbiased genome wide CRISPR-Cas9 screen in HAP1 cells treated with the proteasome inhibitor, Bortezomib (BTZ), to identify genes leading to a BTZ-resistant phenotype. We identified several genes that when perturbed, sensitized cells to BTZ including N-glycanase-1 (NGLY-1), Nuclear factor Erythroid 2-Like-1 (NFE2L1), and DNA damage inducible 1 homolog 2 (DDI2). Herein, we sought to evaluate the effects of perturbing these identified genes in our patient derived GBM cell lines by utilizing CRISPR/Cas9 knockout technology in vitro and in vivo. The generation of NGLY-1, DDI2, and NFE2L1 KO cell lines demonstrated functional sensitivity to the proteasome inhibitor Marizomib (MZB) as observed through a significant reduction of the IC50 in the KO cell lines compared to an adeno-associated virus integration site 1 (AAVS1) control. Functional evaluation also demonstrated reduced proliferation capacity and sphere formation in our KO GBM lines. Ongoing in vivo work will aim to evaluate the mitigation of this resistant pathway in our NSG mouse models orthotopically transplanted with our patient derived KO cell lines. In an ongoing collaborative effort, we aim to functionally assess a novel small molecule NGLY-1 inhibitor for preclinical sensitivity to MZB in our in vitro and in vivo models.