Abstract 2961: Expression of ZEB1, an E-cadherin repressor correlates with poor patient survival in colon cancer and mediates claudin-1 dependent repression of E-cadherin

Abstract

Abstract Claudin family of transmembrane proteins are expressed in tissue specific manner and are regulated differentially in different cancer types. In colon cancer, we have reported dysregulated claudin-1 expression and cellular distribution which correlates with cancer progression especially metastases. However, the mechanism/s underlying claudin-1 dependent regulation of colon cancer remains largely unexplored. Initially, manipulation of claudin-1 in colon cancer cells resulted in reciprocal changes in E-cadherin expression, at transcriptional level. In the current studies, using a tightly regulated microarray analyses, we show that ZEB-1, an E-cadherin repressor changes upon manipulation of claudin-1 expression. However, the claudin-1 dependent changes in ZEB-1 expression were parallel to claudin-1 expression and reciprocal to E-cadherin expression. We have further confirmed this finding at the RNA and protein levels using semi-quantitative RT-PCR and immunoblot analyses. A causal role of ZEB-1 in the claudin-1 mediated E-cadherin regulation was determined by overexpressing full-length ZEB1 cDNA construct in SW620siRNA cells (where claudin-1 expression is stably inhibited and E-cadherin is expressed). ZEB-1 over-expression decreased E-cadherin expression in these cells. In parallel, we inhibited ZEB1 expression in SW480Claudin-1 cells (stably overexpressing claudin-1). Effective inhibition of ZEB1 expression (80-90%) resulted in increased E-cadherin expression even in presence of overexpressed claudin-1 and thus supported a causal role for changes in ZEB1/E-cadherin axis in Claudin-1 dependent changes. We further determined the expression of Claudin-1, E-cadherin and ZEB1 in matched colon cancer samples, using immunoblot analyses, and observed a parallel correlation between the expressions of Claudin-1 and ZEB1 and inverse correlation with E-cadherin expression. We further confirmed our findings using two large clinicogenomic databases representing patients from the Moffitt Cancer Center in Tampa, Florida and the Vanderbilt Medical Center in Nashville, TN (MCC and VMC). Claudin-1 and ZEB1 mRNA expression was noted to be higher in colorectal cancer versus adenomas, normal colon and carcinoma in situ in the VMC training and MCC test sets. Most strikingly, patients with higher than median ZEB1 expression showed significantly worse overall and disease-specific survival in 195 patients with colorectal cancer from MCC dataset compared to those who express lower than median levels of ZEB1. Further analysis is being conducted to determine if the levels of E-cadherin and ZEB1 are inversely proportional on a patient-patient basis. Taken together, our data supports that in colon cancer claudin-1, a tight junction protein, regulates E-cadherin expression through direct/indirect modulation of ZEB-1 expression. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2961.