Tang Xiaowei, Wang Yun, Fan Zhining, Ji Guozhong, Wang Min, Lin Jie, Huang Shu, Meltzer Stephen J
Medical Center for Digestive Diseases, The Second Affiliated Hospital, Nanjing Medical University, Nanjing, China.
Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, China.
Lab Invest. 2016 Feb;96(2):197-205. doi: 10.1038/labinvest.2015.86. Epub 2015 Aug 3.
Klotho, an anti-aging gene, has recently been shown to contribute to human hepatic tumorigenesis. In addition, it is known that Wnt signaling is antagonized by the protein klotho. Because augmented Wnt signaling has an important role in tumorigenesis of human hepatocellular carcinoma (HCC), we studied the relationship of klotho expression and activity to the Wnt pathway in this malignancy. Immunohistochemical analysis performed on tissue arrays revealed that klotho expression levels were significantly lower in HCC than in adjacent noncancerous tissues, while klotho staining was inversely correlated with clinical stage and histologic grade. Patients with klotho-expressing tumors had longer survival periods than did those with klotho-negative tumors. Overexpression of klotho as well as treatment with soluble klotho protein reduced hepatoma cell growth in vitro and in vivo, whereas klotho silencing enhanced cellular proliferation. Moreover, forced expression of klotho inhibited Wnt/β-catenin signaling, as confirmed by reduced expression of β-catenin, inhibition of translocation of β-catenin from the cytoplasm to the nucleus, and reduced expression of c-myc and cyclin D1, two known target genes of the Wnt/β-catenin pathway. In contrast, activation of the Wnt/β-catenin pathway was enhanced when klotho was silenced by inhibitory RNAs. Furthermore, serum levels of soluble klotho in patients with malignant tumors were studied, and results suggested a significant increase in these levels in HCC patients. These data suggest that klotho acts as a tumor suppressor and an inhibitor of the Wnt/β-catenin pathway in HCC, and moreover, that soluble klotho is a potential serum biomarker for HCC.
klotho基因作为一种抗衰老基因，最近被证明与人类肝癌发生有关。此外，已知蛋白质klotho可拮抗Wnt信号传导。由于增强的Wnt信号传导在人类肝细胞癌（HCC）的发生中起重要作用，我们研究了klotho表达和活性与这种恶性肿瘤中Wnt通路的关系。对组织芯片进行的免疫组织化学分析显示，HCC中klotho表达水平明显低于相邻的非癌组织，而klotho染色与临床分期和组织学分级呈负相关。表达klotho的肿瘤患者比klotho阴性肿瘤患者生存期更长。klotho的过表达以及用可溶性klotho蛋白处理可在体外和体内降低肝癌细胞的生长，而klotho沉默则增强细胞增殖。此外，klotho的强制表达抑制了Wnt/β-连环蛋白信号传导，这通过β-连环蛋白表达降低、β-连环蛋白从细胞质向细胞核的转位受到抑制以及c-myc和细胞周期蛋白D1（Wnt/β-连环蛋白通路的两个已知靶基因）表达降低得到证实。相反，当通过抑制性RNA使klotho沉默时，Wnt/β-连环蛋白通路的激活增强。此外，还研究了恶性肿瘤患者血清中可溶性klotho的水平，结果表明HCC患者的这些水平显著升高。这些数据表明，klotho在HCC中作为肿瘤抑制因子和Wnt/β-连环蛋白通路的抑制剂发挥作用，而且可溶性klotho是HCC的潜在血清生物标志物。
