MLH1 and cancer: Some previous studies have shown that hypermethylation of MLH1 and MGMT in tumor tissue are mutually exclusive, indicating that the two genes affect different hypermethylation-associated pathways during cancer development.5 Whereas MLH1 methylation is associated with a colorectal cancer molecular subtype that includes CIMP+, MSI, and mutations in BRAF (but not in KRAS), the MGMT methylation seems to cross-section the major molecular subtypes.