Overexpression of HBxAg in hepatocellular carcinoma and its relationship with Fas/FasL system

AIM: To study the expression and serum level of HBxAg,Fas and FasL in tissues of HCC patients, and to assess the relationship between HBxAg and Fas/FasL system.METHODS: Tissues from 50 patients with HCC were tested for the expression of HBxAg, Fas and FasL by S-P immunohistochemistry. Serum levels of sFas/sFasL and HBsAg/HBeAg were measured by ELISA assay. HBV X gene was detected by PCR in serum and confirmed by automatic sequencing. Fifty cases of liver cirrhosis and 30 normal controls were involved in serum analysis.RESULTS: The expression of HBxAg, Fas and FasL in carcinoma tissues was 96 %, 84 % and 98 %, respectively.Staining of HBxAg, Fas and FasL was observed predominately in cytoplasms, no significant difference was found in intensity between HBxAg, Fas and FasL (P＞0.05). HBxAg, Fas and FasL might express in the same area of carcinoma tissues and this co-expression could be found in most patients with HCC. The mean levels of sFas in serum from HCC, cirrhosis and normal controls were 762.29±391.56 μg@ L-1 835.36±407.33 μg@L-1 and 238.27±135.29 μg@L-1. The mean levels of sFasL in serum from HCC, cirrhosis and normal controls were 156.36±9.61iμg@ L-1, 173.63±18.74 μg@L-1 and 121.96±7.83 μg@ L-1.Statistical analysis showed that both sFas and sFasL in HCC and cirrhosis patients were significantly higher than those in normal controls (P＜0.01). Serum HBV X gene was found in 32 % of HCC patients and ,46 % of cirrhotic patients.There was no significant relationship between serum level of sFas/sFasL and serum X gene detection (P＞0.05). Eight percent of HCC patients with negative HBsAg and HBeAg in serum might have X gene in serum and HBxAg expression in carcinoma tissues.CONCLUSION: Our data suggest that HBxAg and Fas/FasL system plays an important role in the development of human HCC. Expression of HBxAg can leads to expression of Fas/FasL system which and reverse apoptosis of hepatocellular carcinoma induced by FasL.

Cytochrome C oxidase III interacts with hepatitis B virus X protein in vivo by yeast two-hybrid system

AIM: To screen and identify the proteins which interact with hepatitis B virus (HBV) X protein in hepatocytes by yeast two-hybrid system and to explore the effects of X protein in the development of hepatocellular carcinoma (HCC).METHODS: With HBV X gene amplified by polymerase chainreaction (PCR), HBV X bait plasmid, named pAS2-1-X, was constructed by yeast-two hybridization system3 and verified by auto-sequencing assay, pAS2-1-X was transformed into the yeast AH109, and X-BD fusion protein expressed in the yeast cells was detected by Western blotting. The yeast cells cotransformed with pAS2-1-X and normal human liver cDNA library were grown in selective SC/-trp-leu-his-ade medium. The second screen was performed with β-gal activity detection, and false positive clones were eliminated by segregation analysis, true positive clones were amplified,sequenced and analyzed with bioinformatics. Mating experiment was peformed to confirm the binding of putative proteins to X protein in the yeast cells. RESULTS: Bait plasmid pAS2-1-X was successfully constructed and pAS2-1-X correctly expressed BD-X fusion protein in yeast AH109. One hundred and three clones grew in the selective SC/-trp-leu-his-ade medium, and only one clone passed through 13-gal activity detection and segregation analysis. The inserted cDNA fragment showed high homology with Homo sapiens cytochrome C oxidase III (COXIII). Furthermore, mating experiment identified that the binding of COXIII to X protein was specific.CONCLUSION: COXIII protein is a novel protein that can interact with X protein in vivo by yeast two-hybrid system, and may contribute to the development of HCC through the interaction with X protein.