B16 melanoma cells and Yac-1 lymphoma cells were obtained from institute of cell biology, Chinese academy sciences (Shanghai, China). Cells were cultured in RPMI 1640 medium supplemented with penicillin/streptomycin (100 IU/mL and 100 μg/mL, respectively) and 10% heat-inactivated FBS in an atmosphere of 5% CO2 and 90% relative humidity at 37 °C.