The invention relates to novel regulators of plasminogen activation and their use for regulating cell migration, plasminolysis, angiogenesis, fibrinolysis, for treating cancer and thrombo-embolic diseases such as heart stroke. Furthermore, the present invention relates to novel pharmaceutical compositions form regulating cell migration, plasminolysis, angiogenesis and for treating cancer. In particular, the present invention relates to a method of regulating the activation of plasminogen comprising contacting a solution of pro-urokinase (uPA) or tissue plasminogen activator (tPA) and plasminogen with melanotransferrin (p97) for a time sufficient to effect regulation thereof.