Human hepatocellular carcinoma Huh7 cells were obtained from the ATCC (Frederick, MD). Huh7 cells were cultured in DMEM supplemented with 10% inactivated fetal bovine serum and 1% penicillin-streptomycin (Gibco, USA). Human hepatocellular carcinoma Bel7402, Bel7404 and HepG2 cells were provided by the Cell Bank of Institute for Biological Sciences, China Academy of Sciences (Shanghai, China). Human hepatocellular carcinoma SMMC7721 cell was obtained from Cancer Institute of CAMS (Beijing, China). These four cell lines were cultured in RPMI 1640 medium (Hyclone, UT) supplemented with 10% inactivated fetal bovine serum and 1% penicillin-streptomycin. All cells were incubated at 37ºC with 5% CO₂.