The finding that NK cells from cancer patients express PD-1 IC coupled with the observation that the use of anti-PD-1 or anti-PD-L1 monoclonal antibodies improve the anti-tumor activity of NK cells (36, 38, 39) (Figure 1) is clinically relevant for patients with tumors displaying a T-cell-resistant (HLA class Ineg) phenotype. This evidence concerns the gene CD274 and neoplasm.