Pleiotrophin(PTN) also known asheparin-binding brain mitogen(HBBM) orheparin-binding growth factor 8(HBGF-8) orneurite growth-promoting factor 1(NEGF1) orheparin affinity regulatory peptide(HARP) orheparin binding growth associated molecule(HB-GAM) is aproteinthat in humans is encoded by thePTNgene.Pleiotrophin is an 18-kDagrowth factorthat has a high affinity forheparin. It is structurally related tomidkineandretinoic acid induced heparin-binding protein. Secreted growth factor that induces neurite outgrowth and which is mitogenic for fibroblasts, epithelial, and endothelial cells. Binds anaplastic lymphoma kinase (ALK) which induces MAPK pathway activation, an important step in the anti-apoptotic signaling of PTN and regulation of cell proliferation.