[Recent progress of midkine research on cancer]

Midkine is a heparin-binding growth factor, implicated in various biological phenomena such as neuronal survival and differentiation, tissue remodeling and carcinogenesis. Together with pleiotrophin, midkine constitutes a family that is distinct from other heparin-binding growth factors. In this review, I will briefly describe biochemical and biological characteristics of midkine and then focus on its biological significance in cancer. The most intriguing feature of midkine in cancer is its augmented expression in advanced tumors at very high frequency in non-tissue specific manner. In addition, its high expression is also detected in precancerous lesions. Midkine exerts carcinogenesis-related activities, including transforming, anti-apoptotic, angiogenic and fibrinolytic ones. These data provide a possibility of clinical application of midkine. Serum midkine level can be a useful tumor marker. Gene therapy using its promoter region and therapeutic strategy choosing midkine as a molecular target are worth challenging.