Dickkopf 4 (DKK4) acts on Wnt/β-catenin pathway by influencing β-catenin in hepatocellular carcinoma

Abstract

Deregulation of Wnt/b-catenin pathway is a hallmark of major gastrointestinal cancers including hepatocellular carcinoma (HCC). The oncogenic role of b-catenin is well defined but reasons for its accumulation in HCC remain unclear. Dickkopf 4 (DKK4) acts as a negative regulator of Wnt/b-catenin pathway but its functional role in liver carcinogenesis has not been studied. We investigated the role of DKK4 in b-catenin regulation in HCC. Reduced expression of DKK4 was found in 47% (38/81) of HCC, as measured by quantitative real time PCR. Ectopic expression of DKK4 in two HCC cell lines, PLC/PRF/5 (PLC) and MHCC97L (97L), attenuated b-catenin responsive luciferase activity, and decreased both b-catenin and cyclin D1 protein levels. To study the effect of DKK4 on cell growth and tumourigenicity, two stable HCC cell lines were established from PLC and 97L cells. Functional assays demonstrated that overexpression of DKK4 hampered cell proliferation, reduced colony formation and retarded cell migration. When DKK4-expressing 97L stable cells were used to induce tumour xenografts in nude mice (n ¼ 8), reduction in tumour sizes was observed (P ¼ 0.027). Furthermore, immunohistochemical studies showed that decreased expression of DKK4 was associated with b-catenin accumulation in HCC tissues. Additionally, inhibition of the proteasome using specific inhibitor in DKK4-expressing 97L stable cells masked the effect of b-catenin. Our findings suggest a potential tumour suppressive role of DKK4 as well as that of an important regulator of HCC.

High expression of the secreted protein dickkopf homolog 4: Roles in invasion and metastasis of renal cell carcinoma and its association with Von Hippel-Lindau gene

“…However, in the study by Fatima et al (25), the expression levels of DKK4 β-catenin and cyclin D1 were decreased in hepatoma carcinoma cells, and β-catenin was accumulated in the cytoplasm. Similar results have been observed in colorectal cancer (32).…”

“…The neoplasm incidence rate was 100%, and the tumor weights of the mice implanted with cells overexpressing DKK4 were significantly higher than those of the control mice implanted with an empty vector. DKK4 is considered to inhibit the development of tumors, as an antagonist of the Wnt pathway and has also been reported to be able to inhibit the proliferation of tumor cells in hepatic carcinomas (25). However, the issue of whether DKK4 acts as a tumor inhibitor or promoter remains to be resolved.…”

Wnt/?-Catenin Signalling during Liver Metabolism, Chronic Liver Disease and Hepatocarcinogenesis

“…Immunohistochemical data linked decreased Dkk4 expression to accumulation of β-catenin in hepatocellular carcinoma tissue. In addition, the authors showed that Dkk4 overexpression in hepatocellular carcinoma cell lines resulted in reduced cell proliferation, colony formation and cell migration, suggesting a tumour-suppressive role for Dkk4 (74). A recent study demonstrated that hepatocellular carcinoma cells proliferate upon stimulation in high glucose conditions as a result of Dkk4 downregulation, allowing Wnt3a-mediated β-catenin signalling and c-Myc upregulation (75), suggesting the Wnt pathway may be a therapeutic target in insulin-resistant conditions, leading to hepatocellular carcinoma.…”

Expression of ankyrin repeat and SOCS box containing 4 (ASB4) confers migration and invasion properties of hepatocellular carcinoma cells

“…A scratch was then created in each assayed well as described (9,19). Extent of cell migration towards the created wound was followed on every 12 h till 36 h.…”

“…Lipofectamine 2000 was used as transfecting agent. After 48 h, cells were harvested and suspended in Reporter Lysis Buffer (Promega) and subjected to dual luciferase reporter assay as before (18,19).…”