Lapham Abigail, Adams Jemimah E, Paterson Alex, Lee Melanie, Brimmell Matthew, Packham Graham
Cancer Research UK Clinical Centre, Cancer Sciences Division, University of Southampton School of Medicine, Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK.
Gene. 2009 Mar 1;432(1-2):112-7. doi: 10.1016/j.gene.2008.12.002. Epub 2008 Dec 16.
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.
抗凋亡BCL-2家族蛋白BCL-W在结直肠癌（CRC）中常过度表达，在CRC中它与晚期以及p53的表达相关。在本研究中，我们分析了Bcl-w启动子，以确定CRC细胞中BCL-W表达的潜在调节因子。Bcl-w启动子在源自CRC以及其他癌症类型的细胞系中具有高活性。尽管在CRC中p53和BCL-W的表达相关，但野生型或突变型p53的过表达并未显著改变Bcl-w启动子活性，并且在HCT116细胞中内源性p53的缺失也未改变Bcl-w RNA的表达。启动子缺失分析导致鉴定出一个潜在的TCF/LEF因子结合位点，TCF/LEF因子是β-连环蛋白的必需结合伴侣，β-连环蛋白是WNT信号通路的下游靶点。在完整的HCT116细胞中，TCF4和β-连环蛋白与Bcl-w启动子相互作用，并且该位点的突变显著降低了启动子活性。β-连环蛋白的过表达或显性负性TCF4分别增加或降低了Bcl-w启动子的活性。在大多数CRC中β-连环蛋白被激活，这些结果表明BCL-W可能作为不适当的WNT/β-连环蛋白信号传导的下游效应物发挥作用。
