PROJECT SUMMARY The cytochrome P450s (CYPs) are the major enzymes involved in drug metabolism and bioactivation. It is well known that several CYP enzymes metabolize omega-3 fatty acids to their epoxy metabolites that inhibit angiogenesis, tumor growth, and metastasis. Numerous polycyclic aromatic hydrocarbons (PAH) are human carcinogens. PAH-DNA adducts may lead to DNA damage and mutations in critical genes, eventually leading to cancer. A significant positive linear regression between levels of PAH-DNA adducts and tumor incidence was observed in animal experiments in our laboratory. We also discovered that omega-3 fatty acids eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) inhibited CYP1B1, EZH2, DNMT3a, miR 17, miR19b-1 and significantly decreased pulmonary and hepatic PAH-DNA adducts, and tumor incidence. The central hypothesis of this application is that omega 3-fatty acids and their epoxy metabolites will attenuate pulmonary carcinogenesis by multiple mechanisms entailing attenuation of PAH-DNA adduct formation by modulating CYPs, as well as by suppression of tumorigenesis, probably via modulation of epigenetic genes (e.g., EZH2, DNMT3a, miR-17, miR-19b-1). We propose the following Specific Aims. Aim 1: To test the hypothesis that CYP1A1 and CYP1B1 play mechanistic roles in prevention of PAH carcinogenesis in mice maintained on EPA, DHA, or EPA + DHA diets, compared to those on a CO diet, followed by exposure of these mice to BP for the study of the mechanisms. Aim 2: To test the hypothesis that mice deficient in soluble epoxide hydrolase (sEH) will confer more protection than WT mice to EPA/DHA-mediated prevention of PAH carcinogenesis, as sEH is known to rapidly hydrolyze epoxy metabolites such as 17,18-epoxy eicosatetraenoic acid (EEQ) and 19,20-epoxy docosapentaenoic acids (EDP) in serum and tissues to inactive metabolites. In some experiments, we will treat WT mice with the specific sEH inhibitor, t-TUCB, or a new t-TUCB-like inhibitor (that is likely to go to human clinical trials soon), followed by treatment of mice with EPA/DHA and BP. Aim 3: To test the hypothesis that endogenous omega-3 fatty acids, especially their epoxy metabolites, will play a pivotal role in the prevention of pulmonary carcinogenesis by PAHs in vivo, and that there is a mechanistic link between CYP1, and sEH. Fat-1-transgenic (Fat-1-Tg) mice, which will convert endogenous omega-6 fatty acids (rich in CO) into omega-3 fatty acids and decrease the ratios of omega-6/omega-3, will be used in this study. We will also create Fat-1-Tg/sEH-null mice for exploring the mechanisms by which CYP1 and sEH enzymes contribute to omega-3 fatty acid-mediated prevention of PAH carcinogenesis. If our hypothesis that CYP1 and sEH enzymes play important roles in omega-3 fatty acids, i.e. EPA/DHA-mediated prevention of PAH-induced cancers turns out to be correct, then it will break new grounds in the current understanding of human cancer prevention. If successful, the propos...