NK cells recognize the increased expression of stress-induced molecules on the surface of viral-infected or cancer cells by activating receptors, such as activating receptor killer cell lectin like receptor K1 (KLRK1/NKG2D), DNAX accessory molecule 1 (DNAM-1), and the natural cytotoxicity receptors natural killer P30, 44, and 46 (NKp30, NKp44, and NKp46) [8]. Here, KLRK1 is linked to cancer.