The anti-aging gene KLOTHO is a novel target for epigenetic silencing in human cervical carcinoma

Abstract

BackgroundKlotho was originally characterized as an anti-aging gene that predisposed Klotho-deficient mice to a premature aging-like syndrome. Recently, KLOTHO was reported to function as a secreted Wnt antagonist and as a tumor suppressor. Epigenetic gene silencing of secreted Wnt antagonists is considered a common event in a wide range of human malignancies. Abnormal activation of the canonical Wnt pathway due to epigenetic deregulation of Wnt antagonists is thought to play a crucial role in cervical tumorigenesis. In this study, we examined epigenetic silencing of KLOTHO in human cervical carcinoma.ResultsLoss of KLOTHO mRNA was observed in several cervical cancer cell lines and in invasive carcinoma samples, but not during the early, preinvasive phase of primary cervical tumorigenesis. KLOTHO mRNA was restored after treatment with either the DNA demethylating agent 2'-deoxy-5-azacytidine or histone deacetylase inhibitor trichostatin A. Methylation-specific PCR and bisulfite genomic sequencing analysis of the promoter region of KLOTHO revealed CpG hypermethylation in non-KLOTHO-expressing cervical cancer cell lines and in 41% (9/22) of invasive carcinoma cases. Histone deacetylation was also found to be the major epigenetic silencing mechanism for KLOTHO in the SiHa cell line. Ectopic expression of the secreted form of KLOTHO restored anti-Wnt signaling and anti-clonogenic activity in the CaSki cell line including decreased active β-catenin levels, suppression of T-cell factor/β-catenin target genes, such as c-MYC and CCND1, and inhibition of colony growth.ConclusionsEpigenetic silencing of KLOTHO may occur during the late phase of cervical tumorigenesis, and consequent functional loss of KLOTHO as the secreted Wnt antagonist may contribute to aberrant activation of the canonical Wnt pathway in cervical carcinoma.

MicroRNA-339 and microRNA-556 regulate Klotho expression in vitro

“…This possibility is strengthened by recent work indicating that promoter methylation may, in part, explain why expression of KL is restricted to a limited number of organs (Azuma et al 2012). Beyond normal processes, regulation of KL through methylation of its promoter is reported in multiple cancers (Camilli et al 2010;Chen et al 2010;Lee et al 2010;Wolf et al 2008).…”

“…KL has also been implicated as a tumor-suppressor protein in numerous cancers (Camilli 2010;Chang et al 2012;Chen 2010;Lee 2010;Wang 2011;Wolf 2008) where decreased expression promotes tumorigenesis.…”

Klotho inhibits human follicular thyroid cancer cell growth and promotes apoptosis through regulation of the expression of stanniocalcin-1

“…Mice deficient in Klotho expression exhibit increased renal gene expression of STC1 and STC2 compared with wild-type mice (19). Moreover, the level of Klotho was found to be downregulated in breast, lung, colon, pancreatic, gastric and cervical cancer (36)(37)(38). Although evidence suggests that Klotho acts as a tumor suppressor in numerous cancers (39), little is known concerning its potential effect on thyroid cancer.…”

Klotho expression is correlated to molecules associated with epithelial‑mesenchymal transition in lung squamous cell carcinoma

“…Klotho can inhibit the activation of the Wnt signaling pathway (22). Lee reported that Klotho functioned as a Wnt antagonist in a cervical cancer cell line and that the expression of Klotho in SiHa cells resulted in a decrease in N-cadherin (23). In addition, the IGF-1 signaling pathway has been shown to have a strong influence on the EMT process (14).…”