The downregulation of ligands, such as MHC-I, for inhibitory receptors in conjunction with the abundant expression of ligands recognized by activating receptors, such as killer cell lectin-like receptor K1 (KLRK1) (32) and the natural cytotoxicity receptors (NCRs) (33), predisposes tumor cells to NK cell elimination (34). Here, KLRK1 is linked to neoplasm.