On the other hand, the expression levels of inhibitory receptors on NK cells were increased: for example, KIR3DL1 in PT-2, GC, and CRC [84]; KIR2DL2/L3 in melanoma [97]; NKG2A in BT, LT, and CRC [86,98,99]; PD-1 in ET, HCC, CRC, GC, biliary tumor, and LT [100,101]; TIM-3 in LT, melanomas, and GC [102,103,104]. This evidence concerns the gene PDCD1 and melanoma.