PCNA and neoplasm: Mixed-lineage leukemia protein-5 (MLL5), termed 21spe-MLL5, Cell surface-associated heparan sulfate (HS) proteoglycans (HSPGs) and Proliferating Cell Nuclear Antigen (PCNA) are expressed on the surface of tumor cells, while Platelet-Derived Growth Factor (PDGF)-DD and Nidogen-1 (NID1) glycoprotein are secreted by tumor cells as soluble molecules to interact with NKp44.