MGMT and glioblastoma: TMZ can induce methylation of O6-MG on DNA, and MGMT can transfer O6-MG admixture caused by TMZ to its cysteine residue to avoid DNA crosslinking and breaking, so as to repair DNA of tumor cells, thus resulting in drug resistance of GBM to alkylating agent, and irreversible inactivation of its own, namely “suicide” repair mechanism [28].