Promoter hypermethylation and gene silencing of the DNA mismatch repair gene hMLH1, the DNA alkyl-repair gene O(6)-methylguanine-DNA methyltransferase (MGMT), the detoxifier glutathione S-transferase P1 (GSTP1) and the familial breast cancer gene BRCA1 were reported to create predispositions to four specific genetic lesions: microsatellite instability, G to A transitions, steroid-related adducts and double-strand breaks in DNA, respectively [480]. The gene discussed is MGMT; the disease is breast cancer.