The above results indicated that the cell killing activity of the prepared CD8+ CIK cells might be partially independent on the NKG2D antigen-binding on ovarian cancer cells, particularly OVCAR3 cells which had weak NKG2D binding capacity but 80% were killed by CD8+ CIK cells suggesting the existence of other antigen recognition mechanisms by CD8+ CIK cells. Here, KLRK1 is linked to ovarian cancer.