MGMT and glioblastoma: Thus, a major obstacle to the successful treatment of GBM is inherent and/or acquired chemoresistance to TMZ regulated by an enzyme called O6-methylguanine-DNA methyltransferase (MGMT), which is a highly evolutionarily conserved DNA repair enzyme that removes alkylated guanine residues at the DNA level, thereby antagonizing the effects of alkylating therapeutic agents8,9.