title: 3T3 NIH murine fibroblasts and B78 murine melanoma cells expressing the Escherichia coli N3-methyladenine-DNA glycosylase I do not become resistant to alkylating agents.
abstract: The role of alkylation of the N3 position of adenine in the cytotoxicity of alkylating agents in mammalian cells is still undefined. By co-transfecting NIH3T3 murine fibroblast and murine B78 H1 melanoma cells with pSG5tag and pSV2neo, we obtained clones expressing the mRNA of the bacterial tag gene coding for N3-methyladenine-DNA glycosylase I (Gly I), which specifically repairs N3-methyladenine. The levels of Gly I were 400 times higher in NIH3T3 pSG5tag (clone 3.9.4) and 12-33 times higher in B78 H1 tag clones (2A4, 2A6, 2C3 and 2D1) than in the respective control cells. The sensitivity to alkylating agents was evaluated in tag-expressing cells in comparison with pSG5, pSV2neo co-transfected control cells. As regards the cytotoxic activity of methylating agents (N-methylnitrosourea, N-methyl-N'-nitro-N-nitrosoguanidine, dimethylsulfate and temozolomide) and other alkylators with different structure and different interactions with DNA such as CC-1065 and FCE-24517 (minor groove binders known to bind to N3 of adenine), 4-[bis(2-chloroethyl)amino]-L-phenylalanine and cis-diamminedichloroplatinum II, cytotoxicity was the same for tag-expressing and non-expressing cells. These results suggest that the increased expression of N3-methyladenine-DNA glycosylase is not necessarily a crucial mechanism for the resistance of cells to alkylating agents.
authors.affiliation: Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Imperatori
authors.forename: G
authors.initials: G
authors.lastname: Damia
authors.forename: P
authors.initials: P
authors.lastname: Taverna
authors.forename: E
authors.initials: E
authors.lastname: Garattini
authors.forename: L
authors.initials: L
authors.lastname: Citti
authors.forename: L
authors.initials: L
authors.lastname: Boldrini
authors.forename: M
authors.initials: M
authors.lastname: D'Incalci
mesh_terms: D016475:3T3 Cells / Q000187:drug effects / Q000201:enzymology*; D000225:Adenine / Q000031:analogs & derivatives*; D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D004351:Drug Resistance / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D005798:Genes, Bacterial; D008545:Melanoma / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D051379:Mice; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000477:Alkylating Agents; D012333:RNA, Messenger; D009699:N-Glycosyl Hydrolases; D000225:Adenine