Midkine (MK), also known as MDK and NEGF2, is a non-glycosylated, highly-basic heparin-binding growth factor and member of the NEGF family. Midkine is functionally-related to pleiotrophin and appears to act through a variety of receptors, dependent on the biological activities elicited in target cells. PTP-zeta, LRP, ALK and syndecans are considered to be its primary receptors (1). Midkine is composed of two disulfide-linked domains where the C-terminally located domain contains two heparin binding sites and is usually responsible for midkine activity, though part of the MK activity is enhanced by dimerization. It is a developmentally important retinoic acid-responsive gene product strongly induced during mid-gestation, hence the name midkine. Restricted mainly to certain tissues in the normal adult, MK is strongly induced during oncogenesis, inflammation and tissue repair (2). It is also capable of exerting activities such as cell proliferation, cell migration, angiogenesis and fibrinolysis. In addition to normal development, MK is also involved in the pathogenesis of inflammatory diseases and human carcinomas such as esophageal, stomach, colon, pancreatic, thyroid, lung, urinary, hepatocellular, neuroblastoma, glioblastoma and Wilm´s tumor (3). High MK levels are associated with poor prognosis in some types of cancer. The increased expression in many carcinomas indicates that MK can be applied to the diagnosis of malignancy. MK is also expressed during the reparative stage of bone fractures and suppresses infection of certain viruses, including HIV in target cells (4). MK application could be a promising therapeutic strategy for the treatment of ischemic heart failure (5).

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