The green tea compound, (−)‐epigallocatechin‐3‐gallate downregulates N‐cadherin and suppresses migration of bladder carcinoma cells

Abstract

Green tea has been reported as potential dietary protection against numerous cancers and has been shown to have activity in bladder tumor inhibition in different animal models. The goal of this study was to examine the effects of (−)‐epigallocatechin gallate (EGCG—the major phytochemical in green tea) on growth inhibition and behavior of human bladder carcinoma cells and to identify the altered signaling pathway(s) underlying the response to EGCG exposure. EGCG inhibited the in vitro growth of invasive bladder carcinoma cells with an IC₅₀ range of 70–87 µM. At a concentration of 20 µM, EGCG decreased the migratory potential of bladder carcinoma cells with concomitant activation of p42/44 MAPK and STAT3 and inactivation of Akt. Using biochemical inhibitors of MAPK/ERK, and siRNA to knockdown STAT3 and Akt, inhibition of migration was recorded associated with Akt but not MAPK/ERK or STAT3 signaling in bladder cells. In addition, EGCG downregulated N‐cadherin in a dose‐dependent manner where reduction in N‐cadherin expression paralleled declining migratory potential. Continuous feeding of EGCG to mice prior to and during the establishment of bladder carcinoma xenografts in vivo revealed >50% reduction in mean final tumor volume (P ≤ 0.05) with no detectable toxicity. EGCG inhibited bladder carcinoma cell growth and suppressed the in vitro migration capacity of cells via downregulation of N‐cadherin and inactivation of Akt signaling. Continuous administration of EGCG to mice revealed significant inhibition of tumor growth in vivo indicating a possible preventative role for green tea in bladder cancer. J. Cell. Biochem. 102: 377–388, 2007.