Methods for activating endothelial growth factors VEGF-C or VEGF-D with plasmin, and methods of treatment comprising administering a phamarceutical compositions comprising plasmin. Also disclosed are methods for screening for inhibitors of activation of the growth factors by plasmin, and method of treatment by blocking activation of VEGF-C/D activation by plasmin. Further disclosed are methods for screening for other proteases that activate VEGF-C/D, and for inhibitors of such activation. The invention further includes inhibitors of plasmin activity and methods of treating patients in need thereof with said inhibitors.