NCR2 and neoplasm: NKp44 also binds soluble ligands, including (i) platelet-derived growth factor (PDGF)-DD, which activates NK cells and NK cell-mediated release of proinflammatory cytokines and chemokines [112] and (ii) nidogen-1, a glycoprotein involved in the adhesion of cells with the extracellular matrix, which, once released by tumor cells, may prevent the NK cell-mediated attack, representing an immunosuppressive mechanism [113].