Proprotein convertase inhibitor has been found to block proteolytic processing and activation of VEGF-C and VEGF-D and inhibit angiogenesis and/or lymphangiogenesis. Method and composition are disclosed for inhibiting angiogenesis and/or lymphangiogenesis, and for treating conditions associated with excessive angiogenesis, such as tumors and/or retinopathies, as well as conditions associated with lymphangiogenesis, such as the metastatic spread of malignancies, macular degeneration, inflammatory mediated diseases, rheumatoid arthritis, diabetic retinopathy and psoriasis in a patient. The inventive method and composition utilize proprotein convertase antagonist selected from the group consisting of an anti-proprotein convertase antibody, an antisense nucleic acid molecule against a polynucleotide coding for a proprotein convertase, and an siRNA for inhibiting proprotein convertase expression, as well as proprotein convertase inhibitors.