The PDGF family is related to VEGF and composed of members PDGF-AA, -AB, -BB (disulfide-linked dimers of polypeptide chains A or B), -C and -D. PDGFs act as serum growth factor for fibroblasts, smooth muscle cells (SMCs), and glia cells, and have crucial roles during development but no known normal physiological function in the adult. PDGF activity has been implicated in a variety of cancers, and numerous studies have demonstrated that PDGF-B/PDGFR-β autocrine signaling promotes self-sufficiency in cellular growth signals. They have also been associated with pulmonary hypertension, retinal vascular disease, and fibrotic diseases.