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Deregulation of Wnt/β-catenin pathway is a hallmark of major gastrointestinal cancers including hepatocellular carcinoma (HCC). The oncogenic role of β-catenin is well defined but reasons for its accumulation in HCC remain unclear. Dickkopf 4 (DKK4) acts as a negative regulator of Wnt/β-catenin pathway but its functional role in liver carcinogenesis has not been studied. We investigated the role of DKK4 in β-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 β-catenin responsive luciferase activity, and decreased both β-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=8), reduction in tumour sizes was observed (P=0.027). Furthermore, immunohistochemical studies showed that decreased expression of DKK4 was associated with β-catenin accumulation in HCC tissues. Additionally, inhibition of the proteasome using specific inhibitor in DKK4-expressing 97L stable cells masked the effect of β-catenin. Our findings suggest a potential tumour suppressive role of DKK4 as well as that of an important regulator of HCC.

Loss of E-cadherin is associated with acquisition of metastatic capacity. Numerous studies suggest that histone deacetylation and/or hypermethylation of CpG islands in E-cadherin gene (CDH1) are major mechanisms responsible for E-cadherin silencing in different tumors and cancer cell lines. The hepatitis B virus (HBV)-encoded X antigen, HBx, contributes importantly to the development of hepatocellular carcinoma using multiple mechanisms. Experiments were designed to test if in addition to CDH1 hypermethylation HBx promotes epigenetic modulation of E-cadherin transcriptional activity through histone deacetylation and miR-373. The relationships between HBx, E-cadherin, mSin3A, Snail-1 and miR-373 were evaluated in HBx expressing (HepG2X) and control (HepG2CAT) cells by western blotting, immunoprecipitation (IP), chromatin IP as well as by immunohistochemical staining of liver and tumor tissue sections from HBV-infected patients. In HepG2X cells, decreased levels of E-cadherin and elevated levels of mSin3A and Snail-1 were detected. Reciprocal IP with anti-HBx and anti-mSin3A demonstrated mutual binding. Furthermore, HBx-mSin3A colocalization was detected by immunofluorescent staining. HBx downregulated E-cadherin expression by the recruitment of the mSin3A/histone deacetylase complex to the Snail-binding sites in human CDH1. Histone deacetylation inhibition by Trichostatin-A treatment restored E-cadherin expression. Mir-373, a positive regulator of E-cadherin expression, was downregulated by HBx in HepG2X cells and tissue sections from HBV-infected patients. Thus, histone deacetylation of CDH1 and downregulation of miR-373, together with the previously demonstrated hypermethylation of CDH1 by HBx, may be important for the understanding of HBV-related carcinogenesis.

Graft-versus-host disease (GVHD) is the commonest complication after donor lymphocyte infusion (DLI). In 19 patients undergoing DLI for relapses of hematologic malignancies post hematopoietic stem cell transplantation (HSCT), 11 developed GVHD, of whom nine had isolated liver involvement, and two had liver and skin involvement. The clinical diagnosis of liver GVHD was hepatitic in six patients (55%) and classical in five patients (45%). Patients with GVHD post-DLI showed a different clinical pattern when compared to a cohort of 106 cases of GVHD post-HSCT, in having significantly more isolated liver involvement (9/11 vs 17/106, P<0.001), and less skin (2/11 vs 80/106, P<0.001) and gut (0/11 vs 28/106, P<0.001) involvement. However, liver GVHD post-DLI and post-HSCT had comparable patient characteristics, underlying diseases, clinical subtypes (classical and hepatitic) and response to treatment.