Differential Growth Suppression of Human Melanoma Cells by Tea (Camellia sinensis) Epicatechins (ECG, EGC and EGCG)

Abstract

We previously reported that catechins of green tea have different antiproliferative effects on cell lines derived from gender-dependent cancers; epicatechin 3-gallate (ECG) had the strongest inhibitory effect. In the present study, we examined the effects of epigallocatechin (EGC), epicatechin-gallate (ECG) and EGC 3-gallate (EGCG) on the viability, density, doubling time and cycle number of cell lines derived from melanoma metastasized to lymph nodes (MB-1133 and SE-0154) or distant organs (CH-0356, JK-0346, SA-1171, GE-0208, NS-1176 and LF-0023). These catechins have been documented to have no growth suppressive or apoptotic effects on normal melanocytes (Nihal et al., Int J Cancer 2005;114:513–21). EGCG (50 μM) showed greater inhibitory potency than EGC (50 μM) in SE-0154, NS-1176, GE-0208 and LF-0023 cell lines but the two catechins produced similar inhibitory effects in CH-0356, JK-0346 and SA-1171 cell lines. The IC50 (50% inhibitory concentration) was lower for EGC than EGCG in MB-1133 and CH-0356 cells, higher for EGC than EGCG in GE-0208 cells and comparable (11–12 μM) for both the catechins in LF-0023 cells. When compared with EGC, the cytotoxic effect (% dead cell counts) and the suppression of the growth (change in cell number) of all melanoma cell lines tested were pronounced with EGCG. This investigation validates the hypothesis that anticancer action of the various catechins may vary with the type of malignancy and provides a model for tumor cell heterogeneity based on susceptibility and resistance of tumor cells to different green tea catechins. Therefore, this information is critical for undertaking chemopreventive or chemotherapeutic trials against melanoma and gender-based cancers.