PDGFRA and neoplasm: However, PDGF-C might act also on non-endothelial cells, including tumor cells and perivascular cells, because (i) autocrine growth stimulation of tumor cells by PDGF-C was not observed under cell culture conditions but might occur in the tumors; (ii) PDGFR-α can be phosphorylated and thereby activated on various additional tyrosine residues [61] that are not detected via staining with the PDGFR-α (Tyr754)-specific antibody used in our study; and (iii) PDGF-C was proposed to bind also to receptors other than PDGFR-α [62].