title: Mutation analysis of K-ras and beta-catenin genes related to O6-methylguanin-DNA methyltransferase and mismatch repair protein status in human gallbladder carcinoma.
abstract: O6-methylguanin-DNA methyltransferase (MGMT) is a DNA repair enzyme that transfers methyl groups from O6-methylguanine to itself. Alkylation of DNA at the O6 position of guanine is the first step by alkylating agents in inducing DNA mutations in an organism. When MGMT and the mismatch repair (MMR) system are impaired, O6-methylguanine mispairs with thymine during DNA replication, resulting in a G:C right curved arrow A:T transitional mutation in DNA. We obtained cancer lesions by manual micro-dissection (MMD) from 26 paraffin-embedded formalin-fixed gallbladder carcinoma and Laser Capture Micro-dissection (LCM) method from 10 fresh frozen specimens. Mutation analysis was performed on the micro-dissected samples for K-ras and beta-catenin genes. At codon 12 of the K-ras gene, the MMD and LCM methods detected mutations in 3 (11.5%) and 1 (10%) case, respectively. In exon 3 of beta-catenin gene, only 1 (3.8%) case revealed a mutation in MMD cancer foci. Two cases without MGMT or MMR expression revealed a G right curved arrow A transition mutation in the K-ras gene. The findings suggested that negative MGMT and MMR status contributed to a G:C right curved arrow A:T transitional mutation in the K-ras gene. However, K-ras and beta-catenin mutations were actually rare in GB carcinoma. Other gene mutations frequently occurring in gallbladder carcinoma might be affected by this negative MGMT and MMR status.
authors.affiliation: Department of Surgery, Saga Medical School, Saga 849-8501, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Kohya
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kitajima
authors.forename: Kenji
authors.initials: K
authors.lastname: Kitahara
authors.forename: Kohji
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D020137:Base Pair Mismatch / Q000235:genetics*; D003062:Codon; D003598:Cytoskeletal Proteins / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D005706:Gallbladder Neoplasms / Q000235:genetics* / Q000473:pathology; D011905:Genes, ras; D006801:Humans; D051718:MutS Homolog 2 Protein; D000074081:MutS Homolog 3 Protein; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000235:genetics*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics*; D051176:beta Catenin
chemical_list: C495270:CTNNB1 protein, human; D003062:Codon; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; C078444:MSH3 protein, human; D000074081:MutS Homolog 3 Protein; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D051176:beta Catenin; D019853:O(6)-Methylguanine-DNA Methyltransferase; C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein