Colorectal cancer is the second leading cause of
cancer-related deaths in the U.S. Met, the receptor for
hepatocyte growth factor (HGF), is over-expressed in colon
tumors and is associated with poor prognosis. Recently, the
green tea polyphenol (-)-
epigallocatechin gallate (EGCG) was reported to suppress Met activation in
breast cancer cells. However, the possible confounding effect of
hydrogen peroxide (H(2)O(2)), produced when EGCG is added to cell
culture media, was not assessed. In the present study, the human
colon cancer cell lines HCT116 and HT29 were used to examine the relationships between Met activation, EGCG treatment, and H(2)O(2) generation. At concentrations of 0.5, 1, and 5 microM, EGCG suppressed markedly the activation of Met in the presence of HGF. Concentrations of 10muM EGCG and below generated low amounts of H(2)O(2) (<1.5 microM), whereas higher H(2)O(2) concentrations (>5 microM) were required to directly increase the phosphorylation of Met. Moreover, suppression of Met activation by EGCG occurred in the presence or absence of
catalase, suggesting that such effects were not an 'artifact' of H(2)O(2) generated from EGCG in cell
culture media. We conclude that EGCG might be a beneficial therapeutic agent in the colon, inhibiting Met signaling and helping to attenuate
tumor spread/
metastasis, independent of H(2)O(2)-related mechanisms.