ARF4-mediated Retrograde Trafficking Drives Chemoresistance in Glioblastoma

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 GBM9s high resistance to chemotherapy.