Published online Oct 7, 2016. doi: 10.3748/wjg.v22.i37.8361
Peer-review started: May 23, 2016
First decision: June 20, 2016
Revised: July 4, 2016
Accepted: August 1, 2016
Article in press: August 1, 2016
Published online: October 7, 2016
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.
The expression of autophagy-related genes in HBV-associated hepatocellular carcinoma and non-HBV-HCC cell lines and human liver tissues was examined by quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR) and western blotting. The silencing of target genes was used to examine the function of various genes in apoptosis and cell cycle progression.
The expression of autophagy related genes ATG5, ATG12, ATG9A and ATG4B expression was analyzed in HepG2.2.15 cells and compared with HepG2 and THLE cells. We found that ATG5 and ATG12 mRNA expression was significantly increased in HepG2.2.15 cells compared to HepG2 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 HepG2.2.15 cells (P < 0.005) but did not change in ATG12-silenced HepG2 cells under starvation with Earle’s balanced salt solution. However, the combination blockade of Notch signaling and ATG12 decreased the apoptotic rate of HepG2.2.15 cells from 55.6% to 50.4% (P < 0.05).
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 HepG2.2.15 apoptosis.
Core tip: ATG5-ATG12 protein expression was increased in hepatitis B virus (HBV)-transfected HepG2.2.15 cells when they were compared with HepG2 cells and was increased in tumor liver tissues compared to adjacent non-tumor tissues from hepatocellular carcinoma (HCC) patients with HBV infection. We showed that silencing of ATG12 increased cell apoptosis of HepG2.2.15 cells but not HepG2 cells under starvation conditions. These results suggest that ATG5-ATG12 proteins are important for the survival of HBV-associated HCC during states of limited tumor nutrients. The inhibition of ATG12 might be a good target for HBV-associated HCC treatment.