AbstractUsing a multistep human urothelial model, we previously showed that green tea extract (GTE) selectively modulates actin remodeling in transformed cells (MC‐T11), which resulted in increased cell adhesion and reduced cell motility (Lu et al., Clin Cancer Res 2005;11:1675–83). This study further analyzed which actin binding proteins (ABPs) might be involved in this process. Proteomic profiles of GTE treated and untreated MC‐T11 cells using two‐dimensional gel electrophoresis coupled with liquid chromatography tandem mass spectrometry (LC/MS/MS) and matrix‐assisted laser desorption and ionization time‐of‐flight (MALDI‐TOF) identified 20 GTE‐induced proteins. Among them, 3 were ABPs (tropomodulin, cofilin and annexin‐I), and only annexin‐I showed a dose‐ and time‐dependent expression. The increased annexin‐I correlated with actin remodeling, and was the result of transcription level up‐regulation, as determined by RT‐PCR, pull‐down immunoblot and siRNA analyses. 5‐Azacytidine, a DNA methylation inhibitor, exhibited no effect on annexin‐I expression when used alone, but had an additive effect for GTE‐induced annexin‐I expression. Immunohistochemistry of bladder cancer tissue array showed a decrease of annexin‐I expression in carcinoma in situ and low grade papillary carcinoma (n = 32, 0% positive) compared to nontumor urothelium (n = 18, 89% positive) (p < 0.001 by Fisher exact test), but increased in some (6 of 15, 40%) high‐grade tumors. Together, GTE induced annexin‐I expression plays a role in regulating actin remodeling and decreased annexin‐I expression is a common event in early stage of bladder cancer development. © 2006 Wiley‐Liss, Inc.