KLRK1 and gastric cancer: To promote NK cell activation, Chen et al. designed a bifunctional protein, NKG2D-IL-15, which binds to MICA and other NKG2D ligands on the surface of gastric cancer cells through the extracellular domain of NKG2D and then binds to IL-15 receptor on the surface of NK cells through IL-15, bringing NK cells and gastric cancer cells closer together and promoting the cytotoxicity of NK cells, thereby enhancing the anti-tumor immunity of patients [63].