Rat HSC-T6 cell line was a gift from Dr. Ke AiWu (Liver Cancer Institute, Zhongshan Hospital, Fudan University, China). Cells were maintained in Dulbecco's modified Eagle's medium (Hyclone, USA) containing 10% fetal bovine serum (Hyclone, USA), penicillin (100 IU/ml), and streptomycin (100 IU/ml) (Amresco, USA). Cells were cultured at 37°C in a humidified atmosphere of 5% CO2.