CHEK2 and glioblastoma: Through CRISPRn screens targeting DNA damage response (DDR)-related genes, they found that knockout of MMR genes, including MLH1, MSH6, PMS1, PMS2, and MSH2, leads to TMZ resistance in both WT and RAD18−/− GBM cells, consistent with other studies [44,57], whereas knockout of genes in other DDR pathways, including POLD3, CHEK2, and PRKDC, preferentially sensitizes RAD18−/− GBM cells to TMZ treatment [60].