Cell lysis activities of NK cells. A, Comparison of the groups at different times and different ratios against K562 cells (n = 4). B, Specific cell lysis analysis of IL-15 and IL-15/Hsp70-activated NK cells against K562 cells at different times and effector ratios (n = 4). C, Cytotoxicity assay of IL-15 and IL-15/Hsp70-activated NK cells at 3:1 ratio 48 hours after co-culture against SKOV3 cells (n = 7). The control cancer cells viability was about 90%. Data is demonstrated as mean ± SD, P > 0.05 which indicates no statistical significance.