[Effects of up-regulation of cathepsin S by HBx gene on HepG2 cell]

Objective: To explore the expression of cathepsin S (Cat S) and Hepatitis B virus X protein (HBx) in HBeAg(-) and HBeAg(+ ) hepatocellular carcinoma (HCC), and discuss the effects of Cat S and HBx interaction on HepG2 cell. Methods: Seventy HCC tissue specimens were collected from the surgical resection which were confirmed by pathology in the Fifth Affiliated Hospital of Guangxi Medical University. The tissue samples were separated into two groups: HBeAg(-) group and HBeAg(+ ) group according to the serology of HBeAg. The expression of Cat S and HBx in the para-carcinoma tissue and the HCC tissue was determined by immunohistochemical staining. The recombinant plasmid of pcDNA3.1-HBx and empty plasmid were constructed and transfected transiently into HepG2 cell. Cells were harvested, and Western blot assay was performed to detectthe protein expression of Cat S and HBx. The cell proliferation was measured by methyl thiazolyl tetrazolium (MTT) assay, wound healing assay and transwell migration assay. Results: Immunohistochemical staining showed that Cat S expression was up-regulated in HBeAg(+ ) HCC cancer tissues, compared with HBeAg(-)HCC cancer tissues (52.67%±0.33% vs 41.23%±0.52%, P<0.05). HBx expression was up-regulated in HBeAg(+ ) HCC cancer tissues (92.89%), but not in HBeAg(-)HCC cancer tissues. Compared with HepG2 control group, cells in HepG2-HBx group had significantly higher protein level of Cat S and HBx, more obvious proliferation and migration (21.98%±1.69% vs 58.23%±1.47%) and invasion (24.12%±1.15%vs 64.25%±1.42%) (all P<0.05). Conclusions: The expression of HBx and Cat S had a linear positive correlation in liver tissues, and increased expression of HBx can promote the cell proliferation of HepG2-HBx cell line.