Carcinogenesis Advance Access originally published online on March 10, 2006
Carcinogenesis 2006 27(8):1586-1592; doi:10.1093/carcin/bgi359
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Published by Oxford University Press 2006
Sulindac regulates the aryl hydrocarbon receptor-mediated expression of Phase 1 metabolic enzymes in vivo and in vitro
Cellular Defense and Carcinogenesis Section, Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute at Frederick, National Institutes of Health Frederick, MD, USA
1 Basic Research Program, SAIC - Frederick, Inc., NCI - Frederick, Frederick, MD, USA
*To whom correspondence should be addressed. Tel: +1 301 846 5369; Fax: +1 301 846 6395; E-mail: hcp{at}mail.utexas.edu
Sulindac, a widely used non-steroidal anti-inflammatory drug (NSAID), has been shown to inhibit chemically induced carcinogenesis in animal models. In the present study, we have investigated the molecular mechanism by which sulindac affects the activity and expression of the enzymes that mediate the initial detoxification steps of many environmental carcinogens, the cytochromes P450 1A1, 1A2 and 1B1. Sulindac treatment of SpragueDawley rats resulted in a dose-dependent increase in hepatic cytochrome P450 (CYP) enzyme activity and in the expression of hepatic CYPs 1A1 and 1B1 mRNA. In the HepG2 human liver cancer cell line, sulindac caused a sustained, dose-dependent increase in CYP enzyme activity. Sulindac treatment resulted in a profound, dose-dependent increase in CYP 1A1 mRNA and a modest increase in 1A2 mRNA. The increase in CYP 1A1 mRNA induced by sulindac was, like enzyme activity, sustained for several days after the initial treatment. Sulindac induced the transcription of the CYP1A1 gene, as measured by the level of heterogeneous nuclear 1A1 RNA and by actinomycin D chase experiment. Since the transcription of CYP1A1 is under the control of the aryl hydrocarbon receptor (AhR), we examined the ability of sulindac to activate the receptor. Sulindac bound to the AhR, as measured by ligand-binding assay, and induced the binding of the AhR with the xenobiotic-responsive element present in the promoter region of the CYP1A1 gene. These results are the first demonstration that NSAIDs modulate carcinogen metabolic enzymes and provide a novel mechanism to explain the established chemopreventive activity of sulindac.
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