Alterations of β-catenin and Tcf-4 instead of GSK-3β contribute to activation of Wnt pathway in hepatocellular carcinoma

Objective The goal of this study is to investigate the inappropriate activation of Wnt pathway in the hepatocarcinogenesis. Methods We analyzed the alterations of three key components of Wnt pathway, beta-catenin, glycogen synthase kinase 3beta (GSK-3beta) and T cell factor 4 (Tcf-4), in 34 samples of hepatocellular carcinoma (HCC) and paracancerous normal liver by immunohistochemistry, polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), direct sequencing, semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Results We found 61.8% (21/34) of all the HCCs examined showed an abnormal beta-catenin protein accumulation in the cytoplasm or nuclei. RT-PCR-SSCP and direct sequencing showed that beta-catenin exon 3 mutations existed in 44.1% (15/34) of the HCCs. No mutations of GSK-3beta or Tcf-4 were detected in HCCs. Moreover, mRNA of beta-catenin and Tcf-4 but not GSK-3beta was found to be over expressed in HCCs. On analyzing the relationship between alterations of beta-catenin or Tcf-4 and C-myc or Cyclin D1 expression, we found that the mutations of beta-catenin as well as over expression of beta-catenin or Tcf-4 gene were independently correlated with C-myc gene over expression in HCCs. Conclusions Our present findings strongly suggest mutations of beta-catenin as well as over expression of beta-catenin and Tcf-4 gene activate the Wnt pathway in HCC independently with the target gene most likely to be C-myc.