title: Site-specific oxidation at GG and GGG sequences in double-stranded DNA by benzoyl peroxide as a tumor promoter.
abstract: Benzoyl peroxide (BzPO), a free-radical generator, has tumor-promoting activity. As a method for approaching the mechanism of tumor promoter function, the ability of oxidative DNA damage by BzPO was investigated by using (32)P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and c-Ha-ras-1 protooncogene. BzPO induced piperidine-labile sites at the 5'-site guanine of GG and GGG sequences of double-stranded DNA in the presence of Cu(I), whereas the damage occurred at single guanine residues of single-stranded DNA. Both methional and dimethyl sulfoxide (DMSO) inhibited DNA damage induced by BzPO and Cu(I), but typical hydroxyl radical ((*)OH) scavengers, superoxide dismutase (SOD) and catalase, did not inhibit it. On the other hand, H(2)O(2) induced piperidine-labile sites at cytosine and thymine residues of double-stranded DNA in the presence of Cu(I). Phenylhydrazine, which is known to produce phenyl radicals, induced Cu(I)-dependent damage at thymine residues but not at guanine residues. These results suggest that the BzPO-derived reactive species causing DNA damage is different from (*)OH and phenyl radicals generated from benzoyloxyl radicals. BzPO/Cu(I) induced 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation in double-stranded DNA more effectively than that in single-stranded DNA. Furthermore, we observed that BzPO increased the amount of 8-oxodG in human cultured cells. Consequently, it is concluded that benzoyloxyl radicals generated by the reaction of BzPO with Cu(I) may oxidize the 5'-guanine of GG and GGG sequences in double-stranded DNA to lead to 8-oxodG formation and piperidine-labile guanine lesions, and the damage seems to be relevant to the tumor-promoting activity of BzPO.
authors.affiliation: Department of Hygiene, Mie University School of Medicine, Japan. kawanisi@doc.medic.mie-u.ac.jp
authors.forename: S
authors.initials: S
authors.lastname: Kawanishi
authors.forename: S
authors.initials: S
authors.lastname: Oikawa
authors.forename: M
authors.initials: M
authors.lastname: Murata
authors.forename: H
authors.initials: H
authors.lastname: Tsukitome
authors.forename: I
authors.initials: I
authors.lastname: Saito
mesh_terms: D020121:5' Untranslated Regions / Q000378:metabolism; D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D001483:Base Sequence / Q000187:drug effects; D001585:Benzoyl Peroxide / Q000494:pharmacology*; D002273:Carcinogens / Q000494:pharmacology*; D002417:Cattle; D002999:Clone Cells / Q000187:drug effects / Q000378:metabolism; D003300:Copper / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage / Q000187:drug effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D006147:Guanine / Q000378:metabolism*; D018922:HL-60 Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D010761:Phosphorus Radioisotopes / Q000378:metabolism; D013950:Thymus Gland / Q000378:metabolism
chemical_list: D020121:5' Untranslated Regions; D002273:Carcinogens; D016166:Free Radical Scavengers; D010618:Phenanthrolines; D010761:Phosphorus Radioisotopes; D006147:Guanine; D003300:Copper; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; C002478:bathocuproine; D006861:Hydrogen Peroxide; C028419:cuprous chloride; D003849:Deoxyguanosine; C029892:cupric chloride; D001585:Benzoyl Peroxide