title: Altered O6-alkylguanine-DNA alkyltransferase activity in cell strains originating from mouse skin tumors induced by UV irradiation.
abstract: O6-Alkylguanine-DNA alkyltransferase (AGT) activity was assayed in the extracts of 47 cell strains originating from mouse skin tumors induced by UV irradiation. They were also examined for the sensitivity to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride by colony formation. The AGT activity (fmol/mg protein) of the tumor cell strains varied widely and the mean +/- SE was 72.5 +/- 9.37, while the AGT activity of the nontumor cell strains was 134 +/- 17. Among 47 strains, 6 strains showed extremely low or no AGT activity, about 5 fmol/mg protein or less, and were hypersensitive to 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride. Long-term culture of the tumor cells did not change the AGT activity except in some strains which might have had coexisting normal cells in the population in early passages. All strains showed similar UV sensitivity regardless of AGT activity. This is the first report which demonstrates that about 13% of newly induced tumor cell strains are deficient in AGT activity similar to Mer-/Mex- phenotype that was found in approximately 20% of the established human tumor cell strains.
authors.affiliation: Department of Dermatology, Faculty of Medicine, Kyoto University, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Nishigori
authors.forename: S
authors.initials: S
authors.lastname: Moriwaki
authors.forename: T
authors.initials: T
authors.lastname: Yagi
authors.forename: H
authors.initials: H
authors.lastname: Takebe
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D004354:Drug Screening Assays, Antitumor; D029968:Escherichia coli Proteins; D051379:Mice; D008812:Mice, Hairless; D009363:Neoplasm Proteins / Q000378:metabolism*; D009381:Neoplasms, Radiation-Induced / Q000188:drug therapy / Q000201:enzymology*; D015376:Nimustine / Q000494:pharmacology; D019853:O(6)-Methylguanine-DNA Methyltransferase; D012878:Skin Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000209:etiology; D013047:Specific Pathogen-Free Organisms; D013997:Time Factors; D014157:Transcription Factors; D014407:Tumor Cells, Cultured / Q000201:enzymology
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D009363:Neoplasm Proteins; D014157:Transcription Factors; D015376:Nimustine; C045675:Ada protein, E coli; D019853:O(6)-Methylguanine-DNA Methyltransferase