title: High incidence of nitrosamine-induced tumorigenesis in mice lacking DNA repair methyltransferase.
abstract: The enzyme O6-methylguanine-DNA methyltransferase repairs alkylation-induced DNA damage, O6-methylguanine and O4-methylthymine, the former being formed more frequently. Previously, by means of gene targeting, we generated mice in which alleles for methyltransferase were disrupted. We now use these mouse lines, which are totally deficient in methyltransferase activity, to examine protective effects of the enzyme against tumor formation. In gene-targeted female mice given an i.p. injection of 5 mg/kg of dimethylnitrosamine, a larger number of liver and lung tumors occurred, as compared with normal female mice treated in the same manner. In male mice given a lower dose of carcinogen, the difference between normal and gene-targeted mice was statistically insignificant although more tumors did form in the gene-targeted mice. Methyltransferase apparently afforded protection from nitrosamine-induced tumorigenesis.
authors.affiliation: Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Iwakuma
authors.forename: K
authors.initials: K
authors.lastname: Sakumi
authors.forename: Y
authors.initials: Y
authors.lastname: Nakatsuru
authors.forename: H
authors.initials: H
authors.lastname: Kawate
authors.forename: H
authors.initials: H
authors.lastname: Igarashi
authors.forename: A
authors.initials: A
authors.lastname: Shiraishi
authors.forename: T
authors.initials: T
authors.lastname: Tsuzuki
authors.forename: T
authors.initials: T
authors.lastname: Ishikawa
authors.forename: M
authors.initials: M
authors.lastname: Sekiguchi
mesh_terms: D000818:Animals; D004128:Dimethylnitrosamine; D005260:Female; D008113:Liver Neoplasms / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D008175:Lung Neoplasms / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D008780:Methyltransferases / Q000172:deficiency / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D019853:O(6)-Methylguanine-DNA Methyltransferase; D012737:Sex Factors
chemical_list: D008780:Methyltransferases; D019853:O(6)-Methylguanine-DNA Methyltransferase; D004128:Dimethylnitrosamine