PVR and melanoma: In our model, this effect of melanoma-derived CAFs seems to be specific to these two NKG2D ligands because ULPBs expression is not affected, even if we cannot exclude that the secretion of active MMPs or other factors by CAFs might also influence the expression of other activating receptor ligands (i.e. CD112, CD155, B7-H6, HLA-E) which respectively bind to DNAM-1, NKp30 and NKG2C.