Kremenevskaja N, von Wasielewski R, Rao A S, Schöfl C, Andersson T, Brabant G
Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg Str. 1, D-30625 Hannover, Germany.
Oncogene. 2005 Mar 24;24(13):2144-54. doi: 10.1038/sj.onc.1208370.
Stabilization of beta-catenin by inhibition of its phosphorylation is characteristic of an activation of the canonical Wnt/beta-catenin signaling pathway and is associated with various human carcinomas. It contrasts to an as yet incompletely characterized action of an alternative noncanonical Wnt signaling pathway on neoplastic transformation. The aim of the present study was to test the effects of a member of the noncanonical Wnt signaling pathway, Wnt-5a, in primary thyroid carcinomas and in thyroid carcinoma cell lines. Compared to normal tissue Wnt-5a mRNA expression was clearly increased in thyroid carcinomas. Immunohistochemically, a bell-shaped response was observed with low to undetectable levels in normal tissue and in anaplastic tumors whereas differentiated thyroid carcinomas showed strong positive immunostaining for Wnt-5a. Transfection of Wnt-5a in a thyroid tumor cell line FTC-133 was able to reduce proliferation, migration, invasiveness and clonogenicity in these cells. These effects of Wnt-5a are associated with membranous beta-catenin translocation and c-myc oncogene suppression and are mediated through an increase in intracellular Ca(2+) release, which via CaMKII pathways promotes beta-catenin phosphorylation. Specific inhibition of beta-catenin phosphorylation by W-7, a calmodulin inhibitor, or by KN-93, a CaMKII inhibitor, supports these findings whereas PKC inhibitors were without effect. This interaction occurs downstream of GSK-3 beta as no Wnt-5a effect was seen on the Ser(9) phosphorylation of GSK-3 beta. Our data are compatible with the hypothesis that Wnt-5a serves as an antagonist to the canonical Wnt-signaling pathway with tumor suppressor activity in differentiated thyroid carcinomas.
通过抑制β-连环蛋白磷酸化来实现其稳定是经典Wnt/β-连环蛋白信号通路激活的特征，且与多种人类癌症相关。这与非经典Wnt信号通路在肿瘤转化中尚未完全明确的作用形成对比。本研究的目的是测试非经典Wnt信号通路成员Wnt-5a在原发性甲状腺癌及甲状腺癌细胞系中的作用。与正常组织相比，Wnt-5a mRNA在甲状腺癌中的表达明显增加。免疫组织化学显示，正常组织和间变性肿瘤中Wnt-5a水平低至无法检测，呈钟形反应，而分化型甲状腺癌对Wnt-5a呈强阳性免疫染色。在甲状腺肿瘤细胞系FTC-133中转染Wnt-5a能够降低这些细胞的增殖、迁移、侵袭能力及克隆形成能力。Wnt-5a的这些作用与膜性β-连环蛋白易位及c-myc癌基因抑制有关，并通过细胞内Ca(2+)释放增加介导，后者通过CaMKII途径促进β-连环蛋白磷酸化。钙调蛋白抑制剂W-7或CaMKII抑制剂KN-93对β-连环蛋白磷酸化的特异性抑制支持了这些发现，而PKC抑制剂则无作用。这种相互作用发生在GSK-3β的下游，因为未观察到Wnt-5a对GSK-3β的Ser(9)磷酸化有影响。我们的数据与以下假设相符：在分化型甲状腺癌中，Wnt-5a作为经典Wnt信号通路的拮抗剂具有肿瘤抑制活性。
