Increased ATG5-ATG12 in hepatitis B virus-associated hepatocellular carcinoma and their role in apoptosis

AIM To investigate autophagy-related genes, particularly ATG12, in apoptosis and cell cycle in hepatitis B virus(HBV)-associated hepatocellular carcinoma(HCC) and non-HBV-HCC cell lines.METHODS The expression of autophagy-related genes in HBVassociated hepatocellular carcinoma and non-HBV-HCC cell lines and human liver tissues was examined by quantitative real-time reverse transcriptase-polymerase chain reaction(q RT-PCR) and western blotting. The silencing of target genes was used to examine the function of various genes in apoptosis and cell cycle progression. RESULTS The expression of autophagy related genes ATG5, ATG12, ATG9 A and ATG4 B expression was analyzed in Hep G2.2.15 cells and compared with Hep G2 and THLE cells. We found that ATG5 and ATG12 m RNA expression was significantly increased in Hep G2.2.15 cells compared to HepG 2 cells(P < 0.005). Moreover, ATG5-ATG12 protein levels were increased in tumor liver tissues compared to adjacent non-tumor tissues mainly from HCC patients with HBV infection. We also analyzed the function of ATG12 in cell apoptosis and cell cycle progression. The percentage of apoptotic cells increased by 11.4% in ATG12-silenced Hep G2.2.15 cells(P < 0.005) but did not change in ATG12-silenced HepG 2 cells under starvation with Earle's balanced salt solution. However, the combination blockade of Notch signaling and ATG12 decreased the apoptotic rate of HepG 2.2.15 cells from 55.6% to 50.4%(P < 0.05). CONCLUSION ATG12 is important for HBV-associated apoptosis and a potential drug target for HBV-HCC. Combination inhibition of ATG12/Notch signaling had no additional effect on HepG 2.2.15 apoptosis.

Autophagy related protein 9A increase in hepatitis B virusassociated hepatocellular carcinoma and the role in apoptosis

The majority of hepatocellular carcinoma(HCC)cases are associated with the hepatitis B virus(HBV)infection.Autophagy related protein 9A(ATG9A)is a transmembrane protein required for autophagosome formation.In order to investigate the role of ATG9A in HBV-associated HCC,ATG9A protein expression was determined in tumor liver tissues and compared with adjacent nontumor tissues from HCC patients with or without HBV infection.In HBVassociated HCC tissues,ATG9A protein level was increased in tumor liver tissues,but not in cases of non-HBV HCC.Our findings suggested that ATG9A might be involved in HBV and cancer cell survival.Therefore,we aimed to analyze the function of ATG9A in HBV replication using RNA interference to evaluate the HBV DNA level using real-time PCR.In the present study,there were no significant differences between shATG9A-transfected HepG2.2.15 cells and the mock control.However,we found that silencing ATG9A affected apoptosis in HepG2.2.15 and HepG2 cell lines.Our results indicated that ATG9A might be partly involved in the survival of HCC.Thus,the inhibition of ATG9A together with other targets might be a potential drug target for HCC treatment.