Hepatitis B viral X protein alters the biological features and expressions of DNA repair enzymes in LO2 cells

Objectives This study aimed at examining the effects of hepatitis B viral X protein (HBx) on the biological features and the expression of DNA repair enzymes in non-tumour human hepatic LO2 cells in vitro. Methods The HBx gene was transfected into LO2 cells to establish stably HBx-expressing LO2/HBx cells. The morphological features, cell growth, cell cycle, apoptosis and colony formation of LO2/HBx cells, vector-transfected LO2/pcDNA3.1 cells and unmanipulated LO2 cells were studied. The expressions of DNA repair enzymes and DNA oxidative stress-related 8-hydroxydeoxyguanosine (8-OHdG) were determined by a real-time quantitative polymerase chain reaction assay and high-performance liquid chromatography coupled with electrochemical detection respectively. Results In comparison with controls, significant morphological changes, faster growth, higher frequency of cells at the S phase, but lower at G0/G1 and M/G2 phases, a lower frequency of natural cell apoptosis and a higher percentage of colony formation were observed in the LO2/HBx cells. Furthermore, significantly higher levels of intracellular 8-OHdG and lower levels of human DNA glycosylase alpha (hMYH alpha) mRNA transcripts, but no significant change in human 8-oxoguanine DNA glycosylase 1 (hOGG1), were detected in the LO2/HBx cells. Conclusions Our data indicated that HBx promoted growth and malignant transformation of non-tumour hepatic LO2 cells in vitro, which was associated with the downregulation of hMYH alpha expression and accumulation of mutagenic DNA adduct 8-OHdG.