Suppressing effects of green tea extract and Epigallocatechin-3-gallate (EGCG) on TGF-β- induced Epithelial-to-mesenchymal transition via ROS/Smad signaling in human cervical cancer cells.

Abstract

Transforming growth factor-β (TGF-β)-induced Epithelial-to-mesenchymal transition (EMT) process is a fundamental target for preventing cervical cancer cells' progression and invasion. Green tea and its principal active substance, Epigallocatechin-3-gallate (EGCG), demonstrate anti-tumor activities in various tumor cells. The cell viability of two cervical cancer cell lines, Hela and SiHa, in the experimental groups was examined employing the MTT method, and ROS generation was probed applying 2',7'-dichlorofluorescein diacetate-based assay. The Smad signaling and EMT process was evaluated utilizing western blot analysis and quantitative real-time polymerase chain reaction (qRT-PCR). Chromatin immunoprecipitation (ChIP) and Smad binding element (SBE)-luciferase assays were employed to measure Smad-DNA interaction and Smad transcriptional activity, respectively. EGCG (0-100μmol/L) and green tea extract (0-250μg/ml) suppressed the viability of cancer cells in a dose-dependent manner (p<0.01). Our conclusions affirmed that pre-incubation with green tea extract (80μg/ml) and EGCG (60μmol/L) significantly reversed the impacts of TGF-β in Hela and SiHa cells by decreasing Vimentin, ZEB, Slug, Snail, and Twist and increasing E-cadherin expression. The molecular mechanism of green tea extract and EGCG for TGF-β-induced EMT inhibition interfered with ROS generation and Smad signaling. Green tea extract and EGCG could significantly decrease ROS levels, the phosphorylation of Smad2/3, the translocation, DNA binding, and activity of Smads in cervical cancer cell lines treated with TGF-β1 (p<0.01). EGCG and green tea extract suppressed TGF-β-induced EMT in Hela and SiHa cells, and the underlying molecular mechanism may be related to the ROS generation and Smad signaling pathway.