KLRK1 and neoplasm: 1. Downregulate PD-L1 expression 2. Reduce PD-L1 expression via inhibiting NF-κB 3. Block the immune escape by upregulating the expression of NKG2D ligands on tumor cells and NKG2D on NK cells 4. Enhance the susceptibility to NK cell-mediated lysis by induction of ULBP1 by inhibition of PKC pathwy