1. Ministry of Education Key Laboratory of Diagnostic Medicine and School of Clinical Diagnostic Medicine, and the Affiliated Hospitals of Chongqing Medical University, Chongqing 400016, China; ; 2. Molecular Oncology Laboratory, Department of Orthopaedic Surgery, The University of Chicago Medical Center, 5841 South Maryland Avenue, MC 3079, Chicago, IL 60637, USA; ; 3. Department of Laboratory Medicine of the Affiliated Hospital, Bingzhou Medical University, Yantai, Shandong, China;
Int J Med Sci. 2013 Nov 25;10(13):1888-98. doi: 10.7150/ijms.6019. eCollection 2013.
Aberrant activation of β-catenin signaling plays an important role in human tumorigenesis. However, molecular mechanisms behind the β-catenin signaling deregulation are mostly unknown because genetic alterations in this pathway only account for a small fraction of tumors. Here, we investigator if other major pathways can regulate β-catenin signaling activity. By employing a panel of chemical activators and/or inhibitors of several cellular signaling pathways, we assess these modulators' effects on luciferase reporter driven by β-catenin/TCF4-responsive elements. We find that lithium-stimulated β-catenin activity is synergistically enhanced by protein kinase C activator PMA. However, β-catenin-regulated transcriptional (CRT) activity is significantly inhibited by casein kinase II inhibitor DRB, MEK inhibitor PD98059, G-proteins and their receptor uncoupling agent suramin, protein tyrosine kinase inhibitor genistein, and PI-3 kinase inhibitor wortmannin, suggesting that these cellular pathways may participate in regulating β-catenin signaling. Interestingly, the Ca⁺⁺/calmodulin kinase II inhibitor HDBA is shown to activate β-catenin activity at low doses. Furthermore, Wnt3A-stimulated and constitutively activated CRT activities, as well as the intracellular accumulation of β-catenin protein in human colon cancer cells, are effectively suppressed by PD98059, genistein, and wortmannin. We further demonstrate that EGF can activate TCF4/β-catenin activity and induce the tyrosine phosphorylation of β-catenin protein. Thus, our results should provide important insights into the molecular mechanisms underlying Wnt/β-catenin activation. This knowledge should facilitate our efforts to develop efficacious and novel therapeutics by targeting these pathways.
β-连环蛋白信号的异常激活在人类肿瘤发生中起着重要作用。然而，由于该途径中的遗传改变仅占肿瘤的一小部分，因此β-连环蛋白信号失调的分子机制在很大程度上尚不清楚。在这里，我们研究其他主要途径是否可以调节β-连环蛋白信号活性。通过使用一系列化学激活剂和/或几种细胞信号通路的抑制剂，我们评估了这些调节剂对β-连环蛋白/TCF4 反应元件驱动的荧光素酶报告基因的影响。我们发现，蛋白激酶 C 激活剂 PMA 协同增强锂刺激的β-连环蛋白活性。然而，酪蛋白激酶 II 抑制剂 DRB、MEK 抑制剂 PD98059、G 蛋白及其受体解偶联剂苏拉明、蛋白酪氨酸激酶抑制剂金雀异黄素和 PI-3 激酶抑制剂wortmannin 显著抑制β-连环蛋白调节的转录（CRT）活性，表明这些细胞通路可能参与调节β-连环蛋白信号。有趣的是，低剂量的 Ca²⁺/钙调蛋白激酶 II 抑制剂 HDBA 显示出激活β-连环蛋白活性的作用。此外，Wnt3A 刺激和组成性激活的 CRT 活性以及人结肠癌细胞中β-连环蛋白蛋白的细胞内积累被 PD98059、金雀异黄素和wortmannin 有效抑制。我们进一步证明 EGF 可以激活 TCF4/β-连环蛋白活性并诱导β-连环蛋白蛋白的酪氨酸磷酸化。因此，我们的结果应该为 Wnt/β-连环蛋白激活的分子机制提供重要的见解。这些知识应该有助于我们通过靶向这些途径来开发有效和新颖的治疗方法。
