Fujita M, Furukawa Y, Nagasawa Y, Ogawa M, Nakamura Y
Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Japan.
Cancer Res. 2000 Dec 1;60(23):6683-7.
Accumulation of intracellular beta-catenin, as a result of inactivation of the adenomatous polyposis coli (APC) gene or by mutation of the beta-catenin gene (CTNNB1) itself, is involved in a wide range of human cancers. By means of fluorescent differential display using a murine fibroblast cell line (L-MT), which expresses an activated form of beta-catenin that accumulates in the cells, we found that expression of murine monocyte chemotactic protein-3 (mMCP-3) was suppressed by activated beta-catenin. Inversely, expression of MCP-3 in human colon cancer cells was induced by depletion of beta-catenin after adenovirus-mediated transfer of wild-type APC genes into the cells. A reporter-gene assay indicated that the accumulation of beta-catenin in the nucleus suppressed activity of the MCP-3 promoter through a putative T-cell factor/lymphocyte enhancer factor (Tcf/LEF)-binding site, ATCAAAG; but when the promoter sequence contained a two-base substitution in the binding site, it failed to suppress reporter-gene (luciferase) activity. An electrophoretic mobility-shift assay using the putative Tcf/LEF-binding sequence revealed interaction of the candidate sequence with the beta-catenin complex. Furthermore, induction of MCP-3 cDNA into HT-29 colon cancer cells increased expression of two markers of differentiation: alkaline phosphatase and carcinoembryonic antigen. Our results implied that activation of beta-catenin through the Tcf/LEF signaling pathway may participate in colonic carcinogenesis by inhibiting MCP-3-induced differentiation of colorectal epithelial cells.
由于腺瘤性息肉病 coli（APC）基因失活或β-连环蛋白基因（CTNNB1）自身突变导致的细胞内β-连环蛋白积累，与多种人类癌症有关。通过使用表达在细胞中积累的活化形式β-连环蛋白的小鼠成纤维细胞系（L-MT）进行荧光差异显示，我们发现活化的β-连环蛋白抑制了小鼠单核细胞趋化蛋白-3（mMCP-3）的表达。相反，在腺病毒介导的野生型 APC 基因转入人结肠癌细胞后，β-连环蛋白的缺失诱导了 MCP-3 的表达。报告基因分析表明，β-连环蛋白在细胞核中的积累通过一个假定的 T 细胞因子/淋巴细胞增强因子（Tcf/LEF）结合位点 ATCAAAG 抑制了 MCP-3 启动子的活性；但是当启动子序列在结合位点包含两个碱基替换时，它未能抑制报告基因（荧光素酶）的活性。使用假定的 Tcf/LEF 结合序列进行的电泳迁移率变动分析揭示了候选序列与β-连环蛋白复合物的相互作用。此外，将 MCP-3 cDNA 导入 HT-29 结肠癌细胞增加了两种分化标志物的表达：碱性磷酸酶和癌胚抗原。我们的结果表明，通过 Tcf/LEF 信号通路激活β-连环蛋白可能通过抑制 MCP-3 诱导的结肠直肠上皮细胞分化参与结肠癌发生。
