MGMT and glioblastoma: TMZ is a first‐line chemotherapeutic agent for GBM treatment that causes cancer cell death mainly by generating O6‐methylguanine lesions and then inducing DSBs.[6c] As a DNA methyltransferase, O6‐methylguanine‐DNA methyltransferase (MGMT) directly removes the methyl group from the O6‐methylguanine lesions generated by TMZ and restores the normal guanine structure so that it cannot be converted into a DSB, thereby conferring resistance to TMZ.[13] Therefore, the response of GBM cells to TMZ strongly depends on the status of MGMT.