Proteomic Analyses Of HBV Transgenic Mice

Hepatocellular carcinoma (HCC) is one of the most prevalent malignancies in the world. Many reports show that the development of HCC involves lots of environmental factors such as intake of aflatoxin B1, bibulosity, smoking, but the most important inducement of HCC is considered to be the infection of hepatitis B virus (HBV). The mechanisms of how HBV can cause HCC are not clear up to now. The HBV virus doesn't infect any other animals except human and chimpanzee, nor the cultured cell lines. Proper animal models should be powerful tools in the research of HCC induced by HBV.In order to better understand the consequence of the integration of HBV genes, we introduced the HBx gene into the p21 locus of the mouse genome by homologous recombination. The HBx gene knockin transgenic mice expressed the foreign gene in liver and kidney. The hepatocytes of HBx gene knockin mice began to apoptosis at the age of 6 months. Hepatic steatosis appeared in the liver of transgenic mice at the age of 12 months. All of these phenotypes became more serious when mice aged. The transgenic mice began to develop HCC at the age of 18 months. Nuclear pleomorphism, disorganized endoplasmic reticulum was found in the tumor cells. Decreased glycogen and increased fat droplet were also present in the tumor cells.To find out the mechanisms underlying the HBx induced HCC, and to compare the different function of HBsAg and HBx gene in the development of HCC, proteomic analyses were carried out to find the proteins changed during the hepatocarcinogenesis in the HBx and HBsAg transgenic mice. We collected liver samples from wild type, p21HBsAg/+ p21HBsAg/HBsAg, p21HBx/+, and p21HBx/HBx mice at the ages of 6, 12 and 18 months. Each sample run 2-dimensional electrophoresis 2 to 3 times. The gels with best reduplicate were chosen to be digitized by PDQuest7.0. The differently expressed proteins were identified by MALDI-TOF/MS, and the data of peptide mass fingerprint were online searched by MASCOT. 147 differentially expressed proteins were found. 87 of them were identified by MALDI-TOF/MS.The functions of differentially expressed protein were analyzed. The expression of some proteins taking part in the process of glycolysis and metabolism of lipid were changed. The shortage of glycogen storage and deposit of fat maybe associated with the enhancement of glycolysis and the over-mobilization of fat. The over-production of ROS and the inducement of oxidative stress maybe contribute to the development of HCC in both HBx and HBsAg transgenic mice. Our data also showed that the proteomic changes were different during the tumorigensis between the HBsAg and HBx transgenic mice. For example, spermidine synthase and laminin receptor were only up-regulated in the livers and tumors from the HBsAg gene knockin transgenic mice. Most importantly, an unnamed protein with unknownfunction was found related to the HBx induced HCC. A modified version of this protein was only found in the livers and tumors of the HBx gene knockin transgenic mice. The protein translocated into nucleus when co-transfected with HBx in SMMC-7721, a hepatoma cell line. All these data suggested that the mechanisms of HCC development induced by HBsAg and HBx were different.