Abstract
This study investigated the pathways involved in the effect of green tea epigallocatechin gallate (EGCG) on mitogenesis in BeWo, JEG-3, and JAR placental choriocarcinoma cells. EGCG inhibited cell proliferation in dose-dependent and time-dependent manners, as indicated by the number of cells and incorporation of bromodeoxyuridine (BrdU). A catechin-specific effect of green tea was evident; EGCG was more effective than epicatechin, epicatechin gallate, and epigallocatechin in suppressing cell growth. When all three of the mitogen-activated protein kinase (MAPK) subfamilies, i.e., ERK, p38, and JNK, were examined, EGCG significantly increased levels of phospho-ERK1/2 (pERK1/2) and phospho-p38 (pp38) and did not alter the total protein levels of ERK1/2, p38 MAPK, JNK, and phospho-JNK. EGCG-induced increases in the levels of pERK1/2 and pp38 proteins were prevented by pre-treatment with specific inhibitors of ERK1/2 MAPK and p38 MAPK, respectively. These inhibitors also suppressed EGCG-induced decreases in both cell number and BrdU incorporation. Moreover, pre-treatment with an AMP-activated protein kinase (AMPK) inhibitor prevented the actions of EGCG on proliferation and AMPK phosphorylation. These data suggest that EGCG mediates choriocarcinoma cell growth via the AMPK, ERK, and p38 pathways, but not JNK pathway.
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