NCR3 and cancer: Cellular heparin or heparin sulfate proteoglycans, which are expressed at high levels on cancer cells, are ligands for all NCRs [25], while natural killer cell cytotoxicity receptor 3 ligand 1 (B7-H6) and BCL2-associated athanogene 6 (BAT3) are specific ligands for NKp30 [26,27].