Docosahexaenoic acid (DHA) and polyphenols synergistically induce apoptosis in breast cancer cells by activating protein phosphatases

Abstract

We have investigated the ability of omega-3 fatty acids combined with dietary polyphenols to induce apoptosis in breast cancer cells. The objective of the present study was to investigate the protein tyrosine-mediated and protein serine/threonine kinase-mediated pathways to assess the anticancer effects of these molecules. MDA-MB-231 cells were treated with various concentrations of polyphenols (Curcumin, Resveratrol, Myricetin, Quercetin, Green Tea Polyphenols and Grape Skin Extracts) in the absence or presence of of DHA (25 μM). Effects on cell viability were measured using WST-1 and LDH assays. Induction of apoptosis was analyzed using a vibrant apoptotic assay kit. Phosphorylation of cellular proteins was analyzed using phosphoserine- and phosphotyrosine-specific antibodies. Results of these studies demonstrate that polyphenols act synergistically with DHA to induce apoptosis in breast cancer cells. All of the polyphenols and omega-3 fatty acids tested inhibited tyrosine and serine/threonine phosphorylation of several proteins in breast cancer cells in a dose-dependent manner. However, these agents stimulated serine phosphorylation of a protein at 38 kDa, which was identified using Western analysis as p38 kinase, a member of MAP-kinase super-family. Our data indicate that dietary polyphenols and omega-3 fatty acids may inhibit breast cancer growth by activating cellular protein phosphatases, which induces downstream phosphorylation of Thr 180/Tyr 182 residues on p38 kinase, a regulatory protein involved in cell apoptosis.