MGMT and glioblastoma: The O6-methylguanine-DNA-methyltransferase (MGMT) can resolve some of the TMZ-induced alterations and thus mediate survival, but is frequently found not to be expressed in approximately half of all glioblastoma cells, i.e., about 45% of patients considered to benefit from TMZ (Karachi et al., 2018; Miyauchi and Tsirka, 2018; Arora and Somasundaram, 2019).