Knockdown of HBV surface antigen gene expression by a lentiviral microRNA-based system inhibits HBV replication and HCC growth.

Current options for the treatment of hepatitis B virus (HBV) infections, a common liver cancer risk factor, are limited. While RNA interference (RNAi) technologies have been shown to inhibit HBV replication, the consequent effects on hepatocellular carcinoma (HCC) cell growth are not fully understood. The aim of this study was to evaluate the effect of RNAi-mediated decrease in the HBV surface antigen (HBsAg) gene on HBV replication and HCC growth. A lentiviral microRNA-based system expressing siRNAs targeting the HBsAg gene (LVshHBS) was developed and transfected into HepG2.2.15 cells (HBV stably expressing line). We found that LVshHBS significantly inhibited the HBsAg mRNA and protein levels in the HepG2.2.15 cells, while HBsAg secretion into the culture supernatant decreased by 70%. BALB/c (nu/nu) mice were injected with HepG2.2.15 cells transduced with LVshHBS or control vectors to investigate the effect of inhibiting the HBsAg on the development of tumour growth in a human HCC nude mice model. Compared with the control, the tumour growth in nude mice was significantly decreased after injection with LVshHBS. Microarray analysis of tumour-related genes in LVshHBS-transduced HepG2.2.15 cells showed that the expressions of genes involved in cell cycle, differentiation and oncogenesis such as ACP2, BHLHB2, CLK3, CTSC, FOS, NR1D1, PIM1 and SEPT6 genes were downregulated, while that of the E2F3 gene was upregulated. In conclusion, lentiviral microRNA-based RNAi against the HBsAg gene not only inhibits HBV replication but also inhibits the growth of HCC. Downregulation of growth-related genes is implicated in this mechanism of inhibition.