Abstract 5707: Effects of non-toxic agents and their combinations on genotoxicity-related endpoints, and mutagenesis induced by dimethylbenzanthracene-dihydrodiol in cultured rat mammary cells

As the annual breast cancer incidence in the US is about 200,000, prevention would be of enormous value. There are many leads from studies in isolated cell systems and experimental animals, but when individual putative protective agents have been tested in humans, results have been equivocal or negative. Levels generally present in foods, beverages or supplements may exert only weak protective effects, and combinations of potential chemopreventives may be necessary for effective cancer prevention. Here we investigated combinations of non-toxic nutraceutical agents dosed at or near physiological levels, for their abilities to modulate xenobiotic metabolism, and mutagenesis induced by the proximate rat mammary carcinogen, 7,12-dimethylbenzanthracene-dihydrodiol (DMBAD), in rat mammary epithelial cells. The agents and their 1x concentrations, were: resveratrol (Res), 2.4 μM; sulforaphane (Sul), 0.015 μM; antioxidant mix (α-, γ-tocopherol, 30 μM, Vitamin C, 68 μM (VCE); α-lipoic acid (LA), 2 μM; epigallocatechin gallate, (EGCG) 0.7 μM; and N-acetylcysteine (NAC), 12 μM). All of the single agents were non-toxic at the 1x doses and had no statistically significant effect on cell proliferation. All combinations of the binary agents were non-toxic and several modestly inhibited cell proliferation: EGCG-NAC, 27% inhibition, EGCG-Res, 21% inhibition, EGCG-VCE, 26% inhibition. For protection against oxidative stress, inhibition of the oxidation of dihydrodichlorofluorescinediacetate (DHDCF) was monitored, and NAC and NAC+Res or EGCG produced small (10-20%) inhibition. The effects of the inhibitors on selected phase I and II gene expression were also examined. EGCG, Sul, VCE and Res alone induced NQO1, (often used as a marker of phase II, detoxification activity) expression and did not induce CYP1A1 or 1B1. In mutagenesis experiments most of the individual agents did not result in statistically significant inhibition of mutagenesis, but some led to minor inhibition (ca. 20%). We also tested several binary combinations of agents, and some of these led to significant inhibition of mutagenesis. The combinations, NAC + Sul, NAC + Res, and NAC + LA inhibited mutagenesis by 25 - 50% at or near physiologic levels. In conclusion, several non-toxic agents favorably affected expression of genes involved in polycyclic aromatic hydrocarbon-induced carcinogenesis, and several combinations of these agents inhibited cell proliferation, and mutagenesis in cultured rat mammary cells by DMBAD. Supported by the Susan Komen Foundation grant # KG080836. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5707.