Abstract 2814: Inhibition of PhIP/DSS-induced colon carcinogenesis by different forms of tocopherols in CYP1A-humanized mice

Abstract

Abstract Tocopherols (T), which exist as α-, β-, γ-, and δ-T are important dietary antioxidants. Our previous studies have demonstrated that a mixture of tocopherols (γ-TmT), δ-T, and γ-T effectively inhibited colon carcinogenesis in AOM/DSS-treated mice or AOM-treated rats. However, the effects of different forms of tocopherols on carcinogenesis in animal models and in humans remain controversial. In the present study, we investigated the inhibitory effects of α-T, γ-T, and δ-T on colon carcinogenesis induced by a dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), and promoted by dextran sodium sulfate (DSS) in CYP1A-humanized (hCYP1A) mice. At 5-6 weeks age, male hCYP1A mice were fed the AIN93M diet or diet supplemented with 0.2% α-T, γ-T, or δ-T for 1 week before PhIP treatment (2x 100mg/kg b.w., 3 days apart), which was followed by DSS (1.5% in drinking water for 4 days) treatment. The mice were sacrificed 10 weeks after the first dose of PhIP. Significant inhibition of colon tumor incidences was caused by dietary δ-T and γ-T, but not by α-T. In addition, oxidative and nitrosative stress markers (i.e., 8-oxo-dG and nitrotyrosine) as well as pro-inflammatory stress markers (i.e., PGE2, LTB4, NFκB and p-STAT3) were significantly reduced by δ-T. Dietary treatment with δ-T and γ-T significantly increased the δ-T and γ-T levels, respectively, in the blood and tissues, but their levels were still lower than the levels of α-T. However, the levels of their side-chain degradation metabolites (δ-T and γ-T forms of carboxyethyl hydroxychroman and carboxymethylbutyl hydroxychroman) were much higher than their parent tocopherols in blood and tissues. Altogether, we demonstrated the inhibitory effects of δ-T and γ-T in a dietary carcinogen-induced colon carcinogenesis model. The inhibition is possibly due to the antioxidative, reactive nitrogen species-trapping, and anti-inflammatory activities δ-T and γ-T. (Supported by NIH grants F31CA168333, RO1CA120915 and RO1AT007036 as well as shared facilities funded by CA72720 and ES05022) Citation Format: Chung S. Yang, Jayson X. Chen, Anna B. Liu, Hong Wang, Marlon Lee, Siyuan Yu, Chunfang Zhao, Ying-Yi Kuo, Eric Chi, Nanjoo Suh. Inhibition of PhIP/DSS-induced colon carcinogenesis by different forms of tocopherols in CYP1A-humanized mice. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2814. doi:10.1158/1538-7445.AM2015-2814