DDDR-08. ARF4-MEDIATED RETROGRADE TRAFFICKING AS A MECHANISM OF CHEMORESISTANCE IN GLIOBLASTOMA

Abstract Glioblastoma (GBM) remains a deadly disease with an extremely poor prognosis, owing largely to its high rate of resistance conventional temozolomide (TMZ) chemotherapy. To identify the unknown drivers this chemoresistance, we performed genome-wide CRISPR knockout sensitivity screen. Results showed significant enrichment ~200 novel genes, including ARF4, previously unstudied gene involved in retrograde trafficking—a well-regulated process by which cargo is transported internally from endosomes ultimately nucleus. Initial investigation that ARF4-knockdowns resulted significantly heightened susceptibility TMZ multiple GBM patient-derived xenograft lines and extended survival compared controls (p< 0.01) vivo both primary recurrent lines. Live-cell imaging further revealed inhibited trafficking, while ARF4-overexpressions untenable increase trafficking (p < 0.001) vitro. Enhanced was also observed TMZ-treated cells 0.001), suggesting ARF4 may drive dysregulation promote chemoresistance.We then unbiased proteomics screen control ARF4-knockdown without therapy proteins were being uniquely nucleus during as result ARF4-mediated trafficking. greatest EGFR signaling, validated nuclear expression ARF4-overexpression conditions decrease phenomenon conditions.We show DNA-PK, DNA repair protein transcriptionally activated EGFR, similarly downregulated elevated conditions. Treatment DNA-PK-inhibitor, KU57788, line, indicating potential clinical benefit targeting pathway. Overall, present understanding how acts localization chemoresistance-promoting proteins.