Survival rate of HT2 cells. Media obtained from rAAV2-hIL15-infected or rAAV2-hrGFP-infected HT1080 cells were added to HT2 cells culture. Media containing 1 μg/ml purified hIL15 were added to HT2 cells as a positive control. After 3 days, survival rate of HT2 cells was determined using MTS assay. Data were obtained from three independent triplicate experiments and were presented as mean ± S.D.