MGMT and malignant glioma: Another key molecular feature associated with the clinical course of diffuse gliomas is O6-methylguanine-DNA methyltransferase (MGMT), which encodes a DNA repair protein that removes methyl groups from guanine residues caused by the administration of temozolomide (TMZ), the most common chemotherapeutic agent used in the treatment of malignant gliomas [79, 90, 156].