ToxSci Advance Access originally published online on September 28, 2005
Toxicological Sciences 2006 90(1):61-72; doi:10.1093/toxsci/kfi341
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Toxicogenomic Profiling of the Hepatic Tumor Promoters Indole-3-Carbinol, 17ß-Estradiol and ß-Naphthoflavone in Rainbow Trout
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* Department of Environmental and Molecular Toxicology, Marine and Freshwater Biomedical Sciences Center and Linus Pauling Institute, Center for Gene Research and Biotechnology, Environmental Health Sciences Center, and Department of Statistics, Oregon State University, Corvallis, Oregon 97331
Received August 15, 2005; accepted September 19, 2005
Indole-3-carbinol (I3C), from cruciferous vegetables, has been found to suppress or enhance tumors in several animal models. We previously reported that dietary I3C promotes hepatocarcinogenesis in rainbow trout (Oncorhynchus mykiss) at concentrations that differentially activated estrogen receptor (ER) or aryl hydrocarbon receptor (AhR)-mediated responses based on individual protein biomarkers. In this study, we evaluated the relative importance of these pathways as potential mechanisms for I3C on a global scale. Hepatic gene expression profiles were examined in trout after dietary exposure to 500 and 1500 ppm I3C and 3,3'-diindolylmethane (DIM), a major in vivo component of I3C, and were compared to the transcriptional signatures of two model hepatic tumor promoters: 17ß-estradiol (E2), an ER agonist, and ß-naphthoflavone, an AhR agonist. We demonstrate that I3C and DIM acted similar to E2 at the transcriptional level based on correlation analysis of expression profiles and clustering of gene responses. Of the genes regulated by E2 (fold change 
2.0 or 
0.50), most genes were regulated similarly by DIM (87–92%) and I3C (71%), suggesting a common mechanism of action. Of interest were upregulated genes associated with signaling pathways for cell growth and proliferation, vitellogenesis, and protein folding, stability, and transport. Other genes downregulated by E2, including those involved in acute-phase immune response, were also downregulated by DIM and I3C. Gene regulation was confirmed by qRT-PCR and Western blot. These data indicate I3C promotes hepatocarcinogenesis through estrogenic mechanisms in trout liver and suggest DIM may be an even more potent hepatic tumor promoter in this model.
Key Words: indole-3-carbinol; 3,3'-diindolylmethane; 178-estradiol; gene expression; rainbow trout.
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