Midkine, also known as Neurite Growth-promoting Factor 2, is a basic heparin-binding growth factor of low molecular weight, a member of the NEGF family whose founding member is pleiotrophin. This protein exhibits neurite outgrowth-promoting activity and may play a role in nervous system development and/or maintenance. Midkine is pleiotropic, capable of exerting activities such as cell proliferation, cell migration, angiogenesis and fibrinolysis.