TCF4/β-Catenin Complex Activates Smo and Gli1 to Promote Migration and Proliferation of Hepatocellular Carcinoma Cells

Hepatocelluar carcinoma severely affects patients because of high incidence of cancer-mediated deaths. Wnt and hedgehog signalling pathways have been known to be associated with hepatocelluar carcinoma cell proliferation and migration; however, molecular connections between the two pathways are largely unknown. In this investigation the expression levels of key Wnt signalling genes (Wnt3, TCF7, and FZD8) and hedgehog signalling genes (Smo, Gli1, Gli2, and Gli3) were identified to be higher in hepatocelluar carcinoma cell lines (HepG2 and SMMC-7721) than in normal liver cell line (LO2). Western blot results indicated that beta-catenin, Smo, and Gli1 levels were all higher in hepatocelluar carcinoma cells than in normal liver cells. In addition, overexpression of beta-catenin activated Smo and Gli1 as well as accelerated HepG2 cell migration and proliferation. Further, immunoprecipitation assay showed that beta-catenin/TCF4 complex directly bound to Smo and Gli1 promoters. Suppression of beta-catenin or Gli1 inhibited HepG2 cell migration and proliferation, and Gli1 silencing inhibited beta-catenin overexpression effects on cell migration and proliferation, and silencing of beta-catenin inhibited Wnt3a-meidated induction of hedgehog signalling gene expressions, suggesting that beta-catenin acts at the upstream of Smo and Gli1. Taken together, these results provided information for direct connection between Wnt and hedgehog signalling via beta-catenin/TCF4 complex that broaden the regulatory mechanism for Wnt and hedgehog signalling pathways.