ARF4-mediated Retrograde Trafficking Drives Chemoresistance in Glioblastoma

ABSTRACT Glioblastoma (GBM) is the most common type of adult malignant brain tumor, with a median survival of only 21 months. This is partly due to the high rate of resistance to conventional therapy, including temozolomide (TMZ), leading to recurrence rates close to 100%. It still remains unknown what drives the development of this resistance. To identify the unknown genes driving the development of this resistance, we performed a genome-wide CRISPR knockout screen comparing a DMSO-treated population with a TMZ-treated population over 14 days. We identified 4 previously unstudied genes – ARF4 , PLAA, SPTLC1 , and PIGK – that showed significant elevations in expression in recurrent tumors in patient datasets, along with significant survival benefits corresponding to low gene expression. Further investigation of ARF4 , known to be involved in retrograde trafficking, allowed us to identify a mechanism of resistance that is mediated by increased retrograde transport of EGFR into the nucleus. Ultimately, our CRISPR-Cas9 screen has identified a promising therapeutic target, ARF4 , which may drive GBM’s high resistance to chemotherapy.