The Bcl-w promoter is activated by beta-catenin/TCF4 in human colorectal carcinoma cells.
ABSTRACT The antiapoptotic BCL-2 family protein BCL-W is often overexpressed in colorectal carcinoma (CRC) where it correlates with advanced stage and expression of p53. In this work we have analysed the Bcl-w promoter to identify potential regulators of BCL-W expression in CRC cells. The Bcl-w promoter was highly active in cell lines derived from CRC as well as other cancer types. Although expression of p53 and BCL-W correlate in CRC, overexpression of wild type or mutant p53 did not significantly alter Bcl-w promoter activity, and deletion of endogenous p53 did not alter the expression of Bcl-w RNA in HCT116 cells. Promoter deletion analysis lead to the identification of a potential binding site for TCF/LEF factors, obligate binding partners for beta-catenin, a downstream target of the WNT signalling pathway. TCF4 and beta-catenin interacted with the Bcl-w promoter in intact HCT116 cells and mutation of this site significantly decreased promoter activity. The activity of the Bcl-w promoter was increased or decreased, respectively, by overexpression of beta-catenin or dominant negative TCF4. beta-catenin is activated in the majority of CRC and these results suggest that BCL-W may function as a downstream effector of inappropriate WNT/beta-catenin signalling.
Article: β-Catenin signaling increases during melanoma progression and promotes tumor cell survival and chemoresistance.[show abstract] [hide abstract]
ABSTRACT: Beta-catenin plays an important role in embryogenesis and carcinogenesis by controlling either cadherin-mediated cell adhesion or transcriptional activation of target gene expression. In many types of cancers nuclear translocation of beta-catenin has been observed. Our data indicate that during melanoma progression an increased dependency on the transcriptional function of beta-catenin takes place. Blockade of beta-catenin in metastatic melanoma cell lines efficiently induces apoptosis, inhibits proliferation, migration and invasion in monolayer and 3-dimensional skin reconstructs and decreases chemoresistance. In addition, subcutaneous melanoma growth in SCID mice was almost completely inhibited by an inducible beta-catenin knockdown. In contrast, the survival of benign melanocytes and primary melanoma cell lines was less affected by beta-catenin depletion. However, enhanced expression of beta-catenin in primary melanoma cell lines increased invasive capacity in vitro and tumor growth in the SCID mouse model. These data suggest that beta-catenin is an essential survival factor for metastatic melanoma cells, whereas it is dispensable for the survival of benign melanocytes and primary, non-invasive melanoma cells. Furthermore, beta-catenin increases tumorigenicity of primary melanoma cell lines. The differential requirements for beta-catenin signaling in aggressive melanoma versus benign melanocytic cells make beta-catenin a possible new target in melanoma therapy.PLoS ONE 01/2011; 6(8):e23429. · 4.09 Impact Factor