Endocytosis of Resveratrol via Lipid Rafts and Activation of Downstream Signaling Pathways in Cancer Cells

trans-Resveratrol has been proposed to prevent tumor growth and to sensitize cancer cells to anticancer agents. Polyphenol entry into the cells has remained poorly understood. Here, we show that [H-3]-resveratrol enters colon cancer cells (SW480, SW620, HT29) and leukemia U937 cells through a monensin (5-20 mu mol/L) -sensitive process that suggests clathrin-independent endocytosis. Uptake of the molecule can be prevented by methyl-beta-cyclodextrin (2-12 mg/mL), nystatin (12 ng/mL), and filipin (1 mu g/mL), which all disrupt plasma membrane lipid rafts. Accordingly, radiolabeled resveratrol accumulates in sphingomyelin- and cholesterol-enriched cell fractions. Interestingly, extracellular signal-regulated kinases (ERK), c-Jun NH2-terminal kinases (JNK), and Akt also accumulate in lipid rafts on resveratrol exposure (IC50 at 48 h approximate to 30 mmol/L in SW480 and U937 cells). In these rafts also, resveratrol promotes the recruitment, by the integrin alpha(V)beta(3) (revealed by coimmunoprecipitation with an anti-integrin alpha(V)beta(3) antibody), of signaling molecules that include the FAK (focal adhesion kinase), Fyn, Grb2, Ras, and SOS proteins. Resveratrol-induced activation of downstream signaling pathways and caspase-dependent apoptosis is prevented by endocytosis inhibitors, lipid raft-disrupting molecules, and the integrin antagonist peptide arginine-glycine-aspartate (500 nmol/L). Altogether, these data show the role played by lipid rafts in resveratrol endocytosis and activation of downstream pathways leading to cell death. Cancer Prev Res; 4(7); 1095-106. (C)2011 AACR.