Abstract 4129: Effects of the metabolism of omega-3 fatty acid EPA by CYP1A1 in breast cancer proliferation and survival

Abstract

Abstract Omega-3 fatty acids are widely known for their importance in heart disease. However, the impact of omega-3 fatty acids in breast cancer is not fully understood. Through these studies we seek to understand the role of the metabolism of the omega-3 fatty acid known as eicosapentaenoic acid (EPA) in breast cancer and determine whether it may affect breast cancer progression. It is known that high levels (60uM) of EPA have anti-proliferative effects in various cancer lines. Consistent with these reports, we found that EPA treatment (60uM) of the estrogen receptor positive line MCF7 and the estrogen receptor negative line MDA-MB-231 decreases cell proliferation. Interestingly, lower dosing of EPA (15uM-40uM) significantly stimulated the proliferation of these lines. It has been shown that cytochrome P450 1A1 (CYP1A1) selectively epoxygenates EPA to 17(18)-epoxyeicosatetraenoic acid (17,18-EpETE). Measurement of cell growth by MTT assay shows that 17,18-EpETE promotes the proliferation of the MCF7 and MDA-MB-231 lines in a dose- (≥ 1uM) and time-dependent (max effect at 48-72hrs) manner. Together, these results led us to hypothesize that CYP1A1 metabolizes EPA into 17,18-EpETE, thereby promoting breast cancer proliferation and survival. To better understand this epoxygenase mechanism, we studied the impact of CYP1A1 and the 17,18-EpETE metabolite of EPA on cell proliferation by MTT assay, cell cycle progression by propidium iodine staining, and apoptosis by Annexin V flow cytometry. We found that CYP1A1 is expressed in MCF7 and MDA-MB-231 lines and siRNA-mediated knock down significantly inhibits the proliferation of these lines. CYP1A1 knock down also blocks the proliferative effect of treatment with 15uM EPA. Our preliminary data also indicate that 17,18-EpETE promotes growth of the MDA-MB-231 line, in part, by decreasing apoptosis and increasing the S- and G2/M cell populations. Consistently, knock down of CYP1A1 in MDA-MB-231 line increases the G0/1 cell population and decreases number of cells in the S and G2/M phases, consistent with a G1 block. The mechanism of action in MCF7 cells is yet to be determined. Better understanding of the mechanism by which EPA metabolism affects breast cancer may impact our understanding of breast cancer prevention and therapeutics. We propose that CYP1A1 may be of significant importance in breast cancer progression through novel mechanisms that depend on biosynthetic pathways promoting EPA epoxygenation. 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 4129.