Abstract
Abstract Humans are constantly exposed to environmental carcinogenic polycyclic aromatic hydrocarbons (PAHs) through cigarette smoke, diesel exhausts, charcoal-broiled meats, etc. Cytochrome P4501A (CYP1A) enzymes play important roles in the activation of PAHs such as 3-methylcholanthrene (MC) to carcinogenic DNA-binding metabolites. We reported earlier that MC causes persistent induction of hepatic and pulmonary CYP1A1 in mice for several weeks after MC ithdrawal, and that the phenomenon of sustained hepatic CYP1A1 induction is lost in Cyp1a2-null mice. In this study, we tested the hypothesis that MC elicits induction of persistent CYP1A1 nduction in hepa-1 cells, and that CYP1A2 contributes mechanistically to this henomenon. Hepa-1 cells were treated ith the MC (2.5 µM), or dimethylsulfoxide (DMSO) as control, and at selected ime points, CYP1A1 promoter activity, CYP1A1 enzyme activities, contents, and CYP1A1 mRNA levels were studied. We fund that MC markedly and persistently induced CYP1A1 promoter activity, transcription, apoprotein expression, and the CYP1A1 associated ethoxyresorufin O-deethylase (EROD) activities for up to 5 days. Transfection of CYP1A2 siRNA resulted in knockdown of CYP1A2 mRNA by 70%, but a statistically significant increase of basal CYP1A1 mRNA by 35-40%. The induction of CYP1A1 promoter ctivity, CYP1A1 mRNA, CYP1A1 protein, and EROD activity by MC were not affected by CYP1A2 siRNA at the 24 h time point, but was significantly ttenuated by Cyp1a2 siRNA on day 5. These results suggest that CYP1A2, possibly via a metabolite, contributes to the sustained induction of CYP1A1 by MC in hepa-I cells. Further investigations into the mechanisms of persistent induction of CYP1A1 by MC could lead to novel preventative/therapeutic strategies against PAH-mediated carcinogenesis in humans. (Supported in part by 2R01 ES009132.) Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4427. doi:1538-7445.AM2012-4427
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