NKG2D recognizes UL16-binding protein and major histocompatibility complex class I polypeptide-related sequence A/B expressed on the surface of cancer cells (7, 8); proliferating cell nuclear antigen binds to NKp44 (9), while B7-H6 molecule and B cell lymphoma 2-associated athanogene 6 are recognized by NKp30 (10). Here, KLRK1 is linked to cancer.