MGMT (O-6-methylguanine-DNA methyltransferase) is a DNA repair enzyme that removes alkyl adducts from the O6 position of guanine, protecting cells from mutagenic DNA damage induced by alkylating agents 1. The enzyme catalyzes a stoichiometric transfer of methyl groups to a cysteine residue, resulting in irreversible enzyme inactivation [UniProt]. MGMT expression is regulated at multiple levels: promoter/enhancer haplotypes alter transcription factor binding to modulate gene expression 2, while transcriptional co-activators like DDX5 interact with SP1, β-catenin, and RelA to enhance MGMT promoter activity 3. Gene body methylation additionally influences MGMT expression independently of promoter methylation status 4. MGMT has significant clinical relevance in cancer therapy: promoter hypermethylation correlates with improved chemosensitivity to alkylating agents like temozolomide (TMZ) in glioblastomas and pancreatic neuroendocrine tumors 56. Conversely, high MGMT expression confers chemoresistance to TMZ and correlates with poor progression-free survival 6. MGMT promoter methylation frequencies vary by cancer type (30-56% across gastrointestinal, lung, and brain tumors) 78, making MGMT methylation status a prognostic and predictive biomarker for treatment response and clinical outcomes.