KLRK1 and neoplasm: We observed that addition of anti-NKG2D antibody significantly but partially restored CIK treatment-induced remarkable reduction in colony formation ability (Fig. 5D) and tumor sphere formation ability (Fig. 5E) of CIK-treated GFP+ putative CSCs of CNE2 and SUNE1 cells, indicating that NKG2D blockade partially blocked the direct tumor-killing activity of CIK cells against putative CSCs of NPC.