Abstract: Objective To investigate the inhibitory immune mechanisms of cytidine-phosphate-guanosine oligodeoxynucleotides（CpG） on liver cancer proliferation via Toll-like receptors-9（TLR9）. Methods The recombinant expression plasmid of hepatitis B virus X （HBx） were transfected into HepG2 cells and the blank plasmid-transfected HepG2 cells was the control group. 24h later,the HBx protein and the β-actin control protein were identified in the HepG2 cells by Western blotting. Then,CpG and Kupffer cells（KC）,CpG-control and KC were added into the transfected HepG2 cell culture system,respectively. 12h later,the supernatant were collected to detect interferon （IFN）-α and IFN-γ by ELISA,and the adherent HepG2 cells were collected to detect luciferase by reporter gene assay system. Results The Western blotting results showed that the HBx plasmid-transfected HepG2 cells expressed the specific HBx protein; and the dual luciferase reporter gene assay showed that the activity of HBx-mediated signaling decreased by 35% when adding KC cells and CpG into the HBx plasmid-transfected HepG2 cell culture system;and CpG activated KC cells to produce IFN-α and IFN-γ , which were increased by 8.7 folds and by 6.5 folds respectively compared with the control group. Conclusion CpG-activated KC cells could inhibit HBx-mediated signaling through the production of IFN-α and IFN-γ. It might provide a theoretical basis for HCC therapy by blocking the HBx-mediated signal pathway.

Key words: HepG2 cells, Hepatitis B virus X protein, Kupffer cells, Toll-like receptors