KLRK1 and neoplasm: In addition to PD-L1 upregulation, suppression of NK group 2D (NKG2D)-activating ligands (including ULBP1, ULBP2, ULBP3, MHC class I chain-related molecules A and B, MICA and MICB) may represent another way of tumor escape from NKCC [188].