MGMT and glioblastoma: MGMT (0-6 methylguanine DNA methyltransferase) is a DNA-repair enzyme which repairs the naturally occurring or therapeutically induced mutagenic DNA lesion 06-methylguanine back to guanine and prevents mismatch and errors during DNA replication and transcription. Tumor MGMT methylation is predictive of increased benefit from DNA damaging therapies, such as radiation therapy and temozolomide, as well as generally prognostic for survival. In large, randomized trials, GBM patients with MGMT-methylated tumors had improved prognosis (longer survival) than patients who are unmethylated