Deficient expression of O6-methylguanine-DNA methyltransferase combined with mismatch-repair proteins hMLH1 and hMSH2 is related to poor prognosis in human biliary tract carcinoma

Background O 6-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that transfers methyl groups fromO 6-methylguanine to itself. Alkylation of DNA at theO 6 position of guanine is an important step in the induction of mutations in the organism by alkylating agents. TheO 6-methyl G:T mismatch is recognized by the mismatch-repair (MMR) pathway. The biliary duct is highly exposed to alkylating agents because of its anatomical location.