title: Base excision repair of reactive oxygen species-initiated 7,8-dihydro-8-oxo-2'-deoxyguanosine inhibits the cytotoxicity of platinum anticancer drugs.
abstract: Anticancer therapy with cisplatin and oxaliplatin is limited by toxicity and onset of tumor resistance. Both drugs form platinum-DNA cross-linked adducts, and cisplatin causes oxidative DNA damage including the 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) lesion. To assess oxidative DNA damage as a mechanism of cisplatin and oxaliplatin cytotoxicity, 8-oxodG-directed base excision repair was stably enhanced in human embryonic kidney cells by FLAG-tagged expression of human oxoguanine glycosylase 1 (alpha-OGG1) or its functional homologue, Escherichia coli formamidopyrimidine glycosylase (fpg). Both drugs increased reactive oxygen species and 8-oxodG levels, and cytotoxicity was decreased by antioxidant pretreatment. Ectopic expression of alpha-OGG1 or fpg in cell clones increased nuclear and mitochondrial 8-oxodG repair, and reduced death by reactive oxygen species initiators (H(2)O(2), menadione) and both platinum drugs. Exposure to oxaliplatin caused a more marked and sustained block of cell proliferation than exposure to cisplatin. We conclude that the 8-oxodG lesion is cytotoxic, and base excision repair a likely determinant of risk. The greater antitumor efficacy of oxaliplatin seems unrelated to oxidative DNA damage, suggesting a novel strategy for improving the therapeutic index in cancer therapy.
authors: Faculty of Pharmacy, University of Toronto, Toronto, ON, Canada.
authors: Thomas J
authors: TJ
authors: Preston
authors: Jeffrey T
authors: JT
authors: Henderson
authors: Gordon P
authors: GP
authors: McCallum
authors: Peter G
authors: PG
authors: Wells
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000933:Antifibrinolytic Agents / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D002945:Cisplatin / Q000494:pharmacology*; D004249:DNA Damage / Q000187:drug effects; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair / Q000187:drug effects*; D043382:DNA-Formamidopyrimidine Glycosylase / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D029968:Escherichia coli Proteins / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000201:enzymology; D009944:Organoplatinum Compounds / Q000494:pharmacology*; D000077150:Oxaliplatin; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*; D024483:Vitamin K 3 / Q000494:pharmacology
chemical_list: D000933:Antifibrinolytic Agents; D000970:Antineoplastic Agents; D000975:Antioxidants; D029968:Escherichia coli Proteins; D009944:Organoplatinum Compounds; D016877:Oxidants; D017382:Reactive Oxygen Species; D000077150:Oxaliplatin; D024483:Vitamin K 3; D000080242:8-Hydroxy-2'-Deoxyguanosine; D006861:Hydrogen Peroxide; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli; D003849:Deoxyguanosine; D002945:Cisplatin