Green tea polyphenol epigallocatechin-3-gallate inhibits thrombin-induced hepatocellular carcinoma cell invasion and p42/p44-MAPKinase activation

Thrombin has been recently demonstrated to promote hepatocellular carcinoma (HCC) cell migration by activation of the proteinase-activated receptor (PAR) sub-types PAR, and PAR(4) suggesting a role of these proteinase-receptor systems in HCC progression. In this study, we investigated the effect of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenolic compound of green tea on thrombin-PAR(1)/PAR(4)-mediated hepatocellular carcinoma cell invasion and p42/p44 MAPKinase activation. In this study we used the permanent liver carcinoma cell line HEP-3B and two primary cultures established from surgically resected HCCs. We found that stimulation of HCC cells with thrombin, the PAR(1)-selective activating peptide, TFLLRN-NH2, and the PAR(4)-selective activating peptide, AYPGKF-NH2, increased cell invasion across a Matrigel-coated membrane barrier and stimulated activation of p42/p44 MAPKinase phosphorylation. Both the effects on p42/p44 MAPKinases, and on cell invasiveness induced by thrombin and the PAR(1/4) subtype-selective agonist peptides were effectively blocked by EGCG. The results clearly identify EGCG as a potent inhibitor of the thrombin-PAR(1)/PAR(4)-p42/p44 MAPKinase invasive signaling axis in hepatocellular carcinoma cells as a previously unrecognized mode of action for EGCG in cancer cells. Moreover, the results suggest that (-)-epigal-locatechin-3-gallate might have therapeutic potential for hepatocellular carcinoma.