Abstract 2918: Docosahexaenoic acid-induced oxidative stress increases cellular apoptosis through a c-MYC-dependent mechanism in breast cancer.

Abstract

Abstract MYC is a potent oncogene that transcriptionally regulates 15 percent of the genome and is found to be deregulated in approximately 70 percent of cancers (c-MYC), including breast cancer. Activation of c-MYC induces association between its required partners, MYC-associated factor X (MAX) or MAX dimerization protein (MAD), regulating pro-survival and pro-apoptotic pathways, respectively. c-MYC has proved to be a difficult molecular target of inhibition. Only recently have there been strategies providing a way to inhibit c-MYC-dependent tumors and its downstream targets. However, dietary factors like, long-chain fatty acids (LCFA), have been shown to change activity and expression levels of c-MYC in cell culture and animal models. LCFAs have also been reported to induce apoptosis through c-MYC. The present study evaluated whether changes in c-MYC expression or activity were responsible for induction of oxidative stress and apoptosis in response to docosahexaenoic acid (DHA, C22:6) supplementation in breast cancer. c-MYC mRNA and protein levels were determined in vitro in the breast cancer BT-474, MDA-MB-231, and the non-transformed MCF-10A cell lines. qPCR results showed increases in c-MYC mRNA expression upon PUFA treatment in both BT-474 and MDA-MB-231 cancer lines, but not in the MCF-10A non-transformed line. Protein analysis revealed no changes in total c-MYC expression, however total phosphorylation at Thr58 and Ser62 are significantly upregulated in a dose-response manner upon DHA supplementation in the BT-474 cell line. Remarkably, transcriptional activity of c-MYC is highly upregulated as well, suggesting that c-MYC activity increases in response to DHA treatment. Using dihydrodichlorofluorescein diacetate (H2-DCF-DA) assay, which measures intracellular reactive oxygen species (ROS) and oxidative stress, we found increases in response to DHA treatment in all cell lines. Finally, the increase in oxidative stress also resulted in an increase in apoptosis, which we suggest is through c-MYC activation. Further analysis of the c-MYC isoform status, association between MYC-MAX and MYC-MAD complexes, as well as inducers and inhibitors of c-MYC are currently underway to define specific targets where DHA is applying some of its anti-cancer effects. Ultimately, with a goal that this research will reveal dietary targets of DHA that could be used to enhance efficacy to current therapies. Citation Format: Michael Mouradian, Haviva Kobany, Christopher R. Douglas, Nam D. Hoang, Keith D. Kikawa, Ronald S. Pardini. Docosahexaenoic acid-induced oxidative stress increases cellular apoptosis through a c-MYC-dependent mechanism in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2918. doi:10.1158/1538-7445.AM2013-2918