Abstract 1882: Resveratrol and grape seed extract synergistically elevate human colon cancer cell apoptosis and suppress cell proliferation via upregulation of p53 and suppression of Wnt/b-catenin signaling pathways

Abstract

Abstract The health benefits of a diet rich in fruits and vegetables is partly due to the presence of a complex mixture of phytochemicals. The synergistic effect of phytochemicals may be responsible for chemopreventive/protective properties of fruits and vegetables. Resveratrol (RSV), a dietary stilbenoid and grape seed extract (GSE), rich in proanthocyanidins, are marketed as popular dietary supplements and have shown to suppress carcinogenesis in vivo. However, we and others have shown that both RSV (> 100 μM) and GSE (at or > 50 μg/ml) exert anti-cancer properties against human colon cancer cells only at very high doses. We hypothesized that RSV and GSE work together synergistically, at low doses (RSV < 50 μM and GSE < 50 μg/ml), against colon cancer cell proliferation and elevate apoptosis via suppression of Wnt/β-catenin pathway and activation of p53. To test this hypothesis, we used HCT-116 p53 +/+ and p53 -/- colon cancer cells to determine the anti-proliferative (WST-1 assay) and pro-apoptotic properties (cell death detection ELISA kit) of RSV and GSE, alone and in combination, and measured levels of critical proteins in p53 and Wnt pathway using immunoblotting. RSV (100-125 µM) and GSE (at or > 50 µM) suppressed (p < 0.05) proliferation in both p53 +/+ and -/- cell lines. RSV and GSE combination (RSV- 25 μM and GSE − 50 µg/ml - combination index value ∼ 0.7) synergistically suppressed (p < 0.05) colon cancer cell proliferation. RSV and GSE in combination also elevated (p < 0.05) apoptosis irrespective of p53 status in colon cancer cell lines, however the effect was more pronounced (p < 0.001) in p53 +/+ cells. RSV and GSE in combination suppressed (p < 0.05) nuclear translocation of β-catenin, a downstream effector of Wnt pathway, that plays a critical role in colon cancer cell proliferation in both p53 +/+ and -/- cell lines. Apoptosis strongly correlated (p < 0.001 in both cell lines) with pp53 levels and Bax/Bcl-2 ratio that play a crucial role in mitochondrial apoptotic pathway. For the first time, we report that addition of resveratrol to grape seed extract synergistically elevates apoptosis and suppresses human colon cancer cell proliferation via upregulation of p53 and suppression of Wnt/β-catenin pathways. This explains why no magic bullet approach can provide health benefits similar to the synergistic combination of numerous phytochemicals in fruits and vegetables. Focal adhesion kinase (Fak) mediated integrin signaling pathway lies upstream of the well studied p53, PI3K/Akt, Wnt/β-catenin and Ras signaling pathways, and might provide insight into how RSV and GSE combination governs colon cancer cell apoptosis and proliferation. We will examine this possibility in future studies using appropriate in vitro and in vivo models. 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 1882.