K562 tumor cells express ligands for receptors promoting natural cytotoxicity (Nectin-2/PVR for DNAM-1; MICA/B/UBLP1 for NKG2D), but do not express the 2B4 ligand CD48 or classical HLA-A, B, C, and non-classical HLA-E (Hanson et al., 2007). This evidence concerns the gene PVR and neoplasm.