Epigenetic silencing of sFRP1 activates the canonical Wnt pathway and contributes to increased cell growth and proliferation in hepatocellular carcinoma

• Published in: Tumor biology Vol. 33; no. 2; pp. 325 - 336
• Main Authors: Kaur, Pushpinder, Mani, Samson, Cros, Marie-Pierre, Scoazec, Jean-Yves, Chemin, Isabelle, Hainaut, Pierre, Herceg, Zdenko
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-04-2012; Springer Nature B.V
• Subjects: Adult; Aged; Antagonists; Apoptosis; Biomarkers, Tumor; Biomedical and Life Sciences; Biomedicine; c-Myc protein; Cancer Research; Carcinoma, Hepatocellular - genetics; catenin; Cell Cycle Proteins - blood; Cell Cycle Proteins - genetics; Cell death; Cell Enlargement; Cell Proliferation; cyclin D1; Developmental stages; DNA Methylation; Embryo cells; Embryogenesis; Epigenesis, Genetic; Epigenetics; Female; Frizzled-related protein; Frizzled-related protein 1; Gene Silencing; Hepatitis; Hepatocellular carcinoma; Hepatocytes; Humans; Intercellular Signaling Peptides and Proteins - blood; Intercellular Signaling Peptides and Proteins - genetics; Liver cancer; Liver Neoplasms - genetics; Male; Malignancy; Membrane Proteins - blood; Membrane Proteins - genetics; Middle Aged; Research Article; Signal Transduction; Stem cells; Therapeutic applications; Tumor cell lines; Tumors; Wnt protein; Wnt Proteins - metabolism; DNA methylation; Wnt signalling antagonists; Hepatocellular carcinoma; Early biomarker; Epigenetic silencing; Canonical Wnt pathway
• ISSN: 1010-4283; 1423-0380
• DOI: 10.1007/s13277-012-0331-5

The Wnt pathway is a key regulator of embryonic development and stem cells, and its aberrant activation is associated with human malignancies, most notably hepatocellular carcinoma (HCC). Epigenetic deregulation of the genes encoding the secreted frizzled-related proteins (sFRPs), the Wnt signalling antagonists, has been linked with aberrant hyperactivation of the Wnt signalling in HCC cells; however, the precise underlying mechanism remains elusive. We investigated the methylation profiles of Wnt antagonists in liver samples of different stages of HCC development and liver cancer cell lines and studied the functional impact of aberrant epigenetic silencing of
sFRPs
on the canonical Wnt pathway and cell viability. We found that the
sFRP1
gene encoding the subunit is a frequent target of aberrant DNA hypermethylation and silencing in HCC tumours, whereas other extracellular Wnt antagonists,
WIF1
and
Dkk3
, exhibited no methylation in tumour cells, consistent with the notion that aberrant methylation events in cancer cells are non-randomly distributed among the genes and that there is a strong preference for hypermethylation of specific genes in HCC. In addition, by comparing
sFRP1
methylation status in HCC tumours with normal, cirrhotic and chronic hepatitis liver tissues, we identified
sFRP1
gene as a potential early marker of HCC. The restoration of
sFRP1
expression in cancer cells by ectopic expression inhibited Wnt activity accompanied with destabilization of β-catenin and downregulation of c-Myc and cyclin D1, the known downstream targets of
Wnt
pathway. Importantly, restoring
sFRP1
levels in cancer cells inhibited cell growth and induced apoptotic cell death. This study supports the critical role for
sFRP1
silencing in hepatocellular carcinoma and reinforces the importance of the Wnt antagonists in preventing oncogenic stabilization of β-catenin and chronic activation of the canonical Wnt pathway, suggesting that
sFRP1
may be an attractive target for early cancer detection and therapeutic intervention.