c-Rel is a transcriptional repressor of EPHB2 in colorectal cancer
c-Rel is a transcriptional repressor of EPHB2 in colorectal cancer
复制标题
DOI：
10.1002/path.2590
复制
发表时间：
2009-09-01
影响因子：
7.3
通讯作者：
Hu, Chuanmin
中科院分区：
文献类型：
--
作者：
Fu, Tao;Li, Peng;Hu, Chuanmin
受体酪氨酸激酶EPHB2最近被确定为TCF4转录靶点，通过与Ephrin-B配体的排斥相互作用控制肠上皮结构。许多报告表明，尽管有组成型Wnt激活，大多数人类结直肠癌仍失去EPHB2的表达。因此，我们研究了导致EPHB2在结直肠癌中下调的机制。在这项研究中，我们证明了DNA高甲基化不是导致EPHB2在结直肠癌中频繁表达缺失的原因。通过对EPHB2基因5'-侧翼区的克隆和功能分析，发现在远端调控区存在一个潜在的负调控元件。体外电泳凝胶迁移率和体内染色质免疫沉淀实验表明，c-Rel直接与假定的元件结合。通过RNA干扰抑制结肠癌细胞c-Rel活性或敲低c-Rel表达足以诱导EPHB2的表达。此外，瞬时转染实验表明，c-Rel过表达抑制内源性EPHB2在结肠癌细胞中的表达。我们首次证明c-Rel作为EPHB2的转录抑制因子，在结直肠癌中EPHB2的下调中发挥积极作用。版权所有(C) 2009大不列颠和爱尔兰病理学会。约翰·威利父子有限公司出版。
The receptor tyrosine kinase EPHB2 has recently been identified as a TCF4 transcriptional target that controls the intestinal epithelial architecture through repulsive interactions with Ephrin-B ligands. Many reports have demonstrated that most human colorectal cancers lose EPHB2 expression despite constitutive Wnt activation. Therefore, we investigated the mechanisms that cause EPHB2 down-regulation in colorectal cancer. In this study, we demonstrate that DNA hypermethylation was not responsible for the frequent loss of EPHB2 expression in colorectal cancer. Cloning and functional characterization of the EPHB2 gene 5'-flanking region revealed a potential negative regulatory element in the distal regulatory region. lit vitro electrophoretic gel mobility shift and in vivo chromatin immunoprecipitation assays demonstrated that c-Rel directly binds to the putative element. Inhibiting c-Rel activity or knocking down c-Rel expression by RNA interference in colon cancer cells was sufficient to induce EPHB2 expression. Furthermore, transient transfection assays demonstrated that c-Rel over-expression repressed endogenous EPHB2 expression in colon cancer cells. We demonstrate for the first time that c-Rel acts as a transcriptional repressor of EPHB2 and plays an active role in EPHB2 down-regulation in colorectal cancers. Copyright (C) 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.