PCNA and neoplasm: Several tumor-associated ligands for NCRs have been observed, including galectin-3 and B7-H6 (a newly identified ligand in the B7 family) for NKp30 (91), mixed-lineage leukemia protein-5 (MLL5), proliferating cell nuclear antigen (PCNA), nidogen-1 (NID1), platelet-derived growth factor (PDGF) for NKp44 (92), and vimentin for NKp46.