[Hepatitis B virus and deletion of its COOH-terminal forty amino acids: proliferative impact on hepatoma cell line SMMC-7721].

Objective: To explore the biological impact of 40 amino acid deletion at the C-terminal of hepatitis B virus X on the proliferation of hepatoma cells.

Methods: Cells of SMMC-7721 hepatoma cell line were transfected with HBx and its derivative HBx3'-40, harboring the 40 amino acid deletion at the distal C-terminal region. Cell growth curve, colony formation in soft agar plate and tumorigenesis assay in nude mice were used to observe the alterations induced by the transfection of HBx and HBx3'-40. The expression level of PCNA in tumor cells was also investigated.

Results: The growth rates of the cells transfected with HBx and HBx3'-40 were markedly increased as compared with that of the control group. The colony formation rates were enhanced in the cells transfected with HBx(48.7 +/- 8.1) and HBx3'-40 (82.8+/-6.0), comparing with the control (26.9 +/- 3.5) %. In the tumorigenic assay, the size and weight of tumors were significantly increased in the cells transfected with HBx (0.412 +/- 0.212, 0.395 +/- 0.159) % and HBx3'-40 (1.476 +/- 0.232, 0.987 +/- 0.279) %, as compared with the control group (0.051 +/- 0.024, 0.033 +/-0.004) %. The expression level of PCNA in tumors was increased in both HBx (59.00 +/- 2.58) % and HBx3'-40 (69.25 +/- 3.77) % transfected cells, comparing with the control (37.67 +/- 2.52) %. Overall, the cells transfected with HBx3'-40 demonstrated the highest proliferative capacity.

Conclusion: The deletion of 40 amino acids in the C-terminal of HBx is correlated with an enhanced proliferation of hepatoma cells and may play an important role in the malignant transformation of the liver.