Modulation of hepatitis B surface antigen secretion by annexin II expressed in hepatitis B virus-producing hepatoma cells.

The role of annexin II in hepatitis B virus (HBV)-associated hepatocellular carcinoma (HCC) remains to be elucidated. Intracellular hepatitis B surface antigen (HBsAg)-retention contributes to the induction of hepatocarcinogenesis. The present study aimed to investigate the regulation of HBsAg secretion by annexin II expressed in HBV-producing hepatoma cells. The expression of annexin II was analyzed using western blot analysis in SMMC-7721, HepG2, HepG2.2.15, 293T and Chinese hamster ovary (CHO) cells. CHO cells transfected with an annexin II plasmid were used as a positive control. The localization of annexin II and HBsAg was observed in the HepG2 and HepG2.2.15 cells using indirect immunofluorescence. HepG2.2.15 cells were transfected with a human immunodeficiency virus-type 1 viral infectivity factor-hemagglutinin (Vif-HA) plasmid or a control vector and, 24 h post-transfection, MG132 was added to the Vif-complemented HepG2.2.15 cells. Western blot analysis was performed to detect the expression of annexin II and Vif-HA. HepG2 cells were cotransfected with HBV and annexin II expression vectors. Western blot analysis was performed to examine the expression of annexin II and an Abbott chemiluminescence immunoassay was used to assess the levels of HBsAg. The expression of annexin II was lower in the HepG2.2.15 cells compared with the SMMC-7721 and HepG2 cells and the fluorescence signal of annexin II in the HepG2 cells was brighter than in the HepG2.2.15 cells. Annexin II colocalized with HBsAg in the cytosol of the HepG2.2.15 cells. MG132 was not able to increase the stability of annexin II expression in HepG2.2.15 cells. Annexin II reduced the secretion of HBsAg when compared with the control-transfected HepG2 cells. In conclusion, HBV downregulated the expression of annexin II and annexin II decreased the secretion of HBsAg in HBV-producing hepatoma cells in favor of intracellular HBsAg storage.