title: DNA damage, repair, and mutation induction by (+)-Syn and (-)-anti-dibenzo[a,l]pyrene-11,12-diol-13,14-epoxides in mouse cells.
abstract: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental carcinogens. PAHs are classified into bay and fjord region compounds according to structural differences in the molecule region where enzymatic epoxidation occurs. Dibenzo[a,l]pyrene (DB[a,l]P), one of the fjord region compounds, has been demonstrated to be the most carcinogenic PAH known to date. DB[a,l]P is activated to fjord region (+)-syn and (-)-anti-11,12-dihydroxy-13,14-epoxy-11,12,13,14-tetrahydrodibenzo[a,l]pyrene (DB[a,l]PDE) metabolites. In this study, we analyzed mutagenesis induced by (+)-syn- and (-)-anti-DB[a,l]PDE at the cII transgene in Big-Blue mouse cells. The mutant frequency of untreated cells (background level) was 6.53 x 10(-5). This level increased 3.7-fold for 20 nmol/L, 5.3-fold for 50 nmol/L, and 7.9-fold for 100 nmol/L (+)-syn-DB[a,l]PDE, respectively. In the case of (-)-anti-DB[a,l]PDE it increased 4.5-fold for 20 nmol/L, 6.7-fold for 50 nmol/L, and 10.6-fold for 100 nmol/L, respectively, indicating that (-)-anti-DB[a,l]PDE is slightly more mutagenic than (+)-syn-DB[a,l]PDE. The mutational spectra of (+)-syn- and (-)-anti-DB[a,l]PDE were quite similar except for several hotspots, specific for either (+)-syn-DB[a,l]PDE or (-)-anti-DB[a,l]PDE. The most frequently induced mutations were A to T transversions, which were 43.9% for (+)-syn- and 38.8% for (-)-anti-DB[a,l]PDE. In addition, G to T transversions were induced significantly, at frequencies of 18.5% by (+)-syn- and 18.1% by (-)-anti-DB[a,l]PDE. Using UvrABC cleavage and ligation-mediated PCR or the terminal transferase-dependent PCR method, we have determined DB[a,l]PDE-DNA adduct formation sites and repair rates in carcinogen-exposed cells. The mutation hotspots coincided with sites of strong adduct formation, but not all of the adduct hotspots were mutational hotspots. Slow adduct removal occurred for both (+)-syn- and (-)-anti-DB[a,l]PDE adducts over a time period of up to 72 hours. The data suggest that, although the (-)-anti-isomer is slightly more mutagenic, DNA adducts of both DB[a,l]PDE stereoisomers may have similar biological properties. We discuss the implications of these findings for human cancer mutagenesis.
authors.affiliation: Beckman Research Institute of the City of Hope, Duarte, California, USA.
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Yoon
authors.forename: Ahmad
authors.initials: A
authors.lastname: Besaratinia
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Feng
authors.forename: Moon-Shong
authors.initials: MS
authors.lastname: Tang
authors.forename: Shantu
authors.initials: S
authors.lastname: Amin
authors.forename: Andreas
authors.initials: A
authors.lastname: Luch
authors.forename: Gerd P
authors.initials: GP
authors.lastname: Pfeifer
mesh_terms: D000818:Animals; D001483:Base Sequence; D001580:Benzopyrenes / Q000378:metabolism / Q000633:toxicity*; D002874:Chromosome Mapping; D018736:DNA Adducts / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair; D004622:Embryo, Mammalian; D004852:Epoxy Compounds / Q000378:metabolism / Q000633:toxicity*; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009153:Mutagens / Q000378:metabolism / Q000633:toxicity*; D016133:Polymerase Chain Reaction / Q000379:methods; D013237:Stereoisomerism; D014157:Transcription Factors / Q000235:genetics; D019076:Transgenes / Q000187:drug effects / Q000235:genetics; D014764:Viral Proteins
chemical_list: D001580:Benzopyrenes; D018736:DNA Adducts; D004852:Epoxy Compounds; D009153:Mutagens; D014157:Transcription Factors; D014764:Viral Proteins; C039000:cII protein, bacteriophage lambda; C121930:dibenzo(a,l)pyrene diol epoxide