Mechanism of hepatitis B virus X inducing hepatocellular carcinoma in mice through COX-2 and its downstream factors

Abstract

Objective To investigate the dynamic changes and the roles of COX-2 and its downstream factors in the carcinogenic process using a mouse model stably expressing hepatitis B virus X (HBx). Methods The expression of HBx in HBx-EGFP-14-19 cells was detected by Western blotting and RT-qPCR. A mouse model with stable expression of HBx was then established by injecting HBx-EGFP-14-19 cells into KM mice via hepatic portal vein. The mice were subsequently sacrificed at 30, 90, 180 and 360 d, respectively, and the liver tissues were collected. Western blotting, RT-qPCR and immunohistochemical assay were used to detect the expression of HBx in the liver; HE staining was adopted to observe the pathological characteristics of liver tissues. In addition, Western blotting and RT-qPCR were also employed to determine the expression changes of COX-2 and its downstream factors, cell cycle- and apoptosis-related factors in the liver tissues, at both mRNA and protein levels. Results The animal model with long-term stable expression of HBx was successfully constructed and eventually developed into liver cancer. The mRNA and protein levels of COX-2 and its downstream factor VEGF were continuously up-regulated even in 90 d after HBx was transferred into mice and the increment was continued until tumorigenesis (P < 0.05). The protein and mRNA levels of liver pro-apoptotic factors Bad and Bax were decreased (P < 0.05), while those of the anti-apoptotic factor Bcl-2 were increased (P < 0.05), and the levels of cell cycle factors Cyclin D1 and CDK4 were increased (P < 0.05). However, the effects of HBx on the above genes were reversed after administration of COX-2 inhibitor celecoxib. Conclusion HBx can cause liver cancer, which may be related to the up-regulation of COX-2 and its downstream factors

Keywords

• hepatitis b virus x
• liver cancer
• cox-2
• apoptosis
• animal model