title: The resveratrol analogue, 2,3',4,5'-tetramethoxystilbene, does not inhibit CYP gene expression, enzyme activity and benzo[a]pyrene-DNA adduct formation in MCF-7 cells exposed to benzo[a]pyrene.
abstract: Exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs) induces cytochrome P450 (CYP) 1A1 and 1B1 enzymes, which biotransform PAHs resulting in the formation of DNA adducts. We hypothesised that 2,3',4,5'-tetramethoxystilbene (TMS), an analogue of resveratrol and a potent CYP1B1 inhibitor, may inhibit r7, t8, t9-trihydroxy-c-10-(N(2)deoxyguanosyl)-7,8,9,10-tetrahydro-benzo[a]pyrene (BPdG) adduct formation in cells exposed to benzo[a]pyrene (BP). To address this, MCF-7 cells were cultured for 96 h in the presence of 1 μM BP, 1 μM BP + 1 μM TMS or 1 μM BP + 4 μM TMS. Cells were assayed at 2-12 h intervals for: BPdG adducts by r7, t8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence immunoassay; CYP1A1 and 1B1 gene expression changes by relative real-time polymerase chain reaction; and CYP1A1/1B1 enzyme activity by ethoxyresorufin-O-deethylase (EROD) assay. Whereas maximal BPdG levels were similar for all exposure groups, the times at which the maxima were reached increased by 16 and 24 h with the addition of 1 and 4 μM TMS, respectively. The maximal expression of CYP1A1 and CYP1B1 occurred at 16, 24 and 48 h, but the maximal level for EROD-specific activity was reached at 24, 48 and 60 h, in cells exposed to 1 μM BP, 1 μM BP + 1 μM TMS or 1 μM BP + 4 μM TMS, respectively. The area under the curve from 4 to 96 h of exposure (AUC(4-)(96 h)) for BPdG adduct formation was not increased in the presence of TMS, but for CYP1A1 and CYP1B1 expression fold increase AUC(4-)(96 h) and EROD-specific activity AUC(4-)(96 h), there were significant (P < 0.05) increases in the presence of 4 μM TMS. Therefore, during 96 h of exposure in MCF-7 cells, the combination of BP plus TMS caused a slowing of BP biotransformation, with an increase in CYP1A1 and CYP1B1 expression and EROD activity, and a slowing, but no change in magnitude of BPdG formation.
authors.affiliation: Carcinogen-DNA Interactions Section, Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, National Institutes of Health, 37 Convent Drive, Bethesda, MD 20892-4255, USA.
authors.forename: Tracey
authors.initials: T
authors.lastname: Einem Lindeman
authors.forename: Miriam C
authors.initials: MC
authors.lastname: Poirier
authors.forename: Rao L
authors.initials: RL
authors.lastname: Divi
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D001564:Benzo(a)pyrene / Q000378:metabolism* / Q000494:pharmacology; D001711:Biotransformation; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D018736:DNA Adducts / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D013267:Stilbenes / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: C440850:2,4,3',5'-tetramethoxystilbene; D018736:DNA Adducts; D013267:Stilbenes; C056612:benzo(a)pyrene-DNA adduct; D001564:Benzo(a)pyrene; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1