GSK-3β suppresses HCC cell dissociation <i>in vitro</i> by upregulating epithelial junction proteins and inhibiting Wnt/β-catenin signaling pathway

Abstract

Glycogen synthase kinase-3 (GSK-3) is required in the expression of epithelial junction proteins. It was found downregulated in hepatocellular carcinoma (HCC) tissues. The purpose of this study was to investigate the role of GSK-3 in modulating the metastatic behaviors of human HCC cell lines in vitro. In this study, the expression level of GSK-3 was measured in 4 human HCC cell lines, and the small interfering RNA (siRNA) vectors against or plasmids encoding GSK-3 were used to evaluate the responses of target cells to the knockdown or overexpression of this kinase, respectively. Our results showed that GSK-3 expression was significantly lower in human HCC cell lines with high metastatic potential than that in HCC cell lines without metastatic characteristics or in a normal human liver cell line. The knockdown of GSK-3 by siRNA led to a decreased expression of the epithelial junction molecules (ZO-1, E-cadherin) and an increase in the expression of a mesenchymal cell marker (-SMA) and a gene transcription factor (-catenin), resulting in enhanced tumor cell dissemination. In contrast, gain-of-function studies revealed that ectopic expression of GSK-3 reduced invasive and migratory abilities of HCC cells accompanied by decreased HCC cell proliferation and induced apoptosis. More importantly, downregulation of GSK-3 led to an increase in the expression and accumulation of -catenin in the nuclei, promoting gene transcription. In conclusion, GSK-3 might play a vital role in suppressing HCC dissociation by preventing the disassembly of cancer cell epithelial junctional complex via the GSK-3/-catenin pathway.