the present invention is based of the discovery of two modified forms of human platelet factor - 4 , herein named mpf - 4 and cpf - 4 , which were isolated from serum free culture medium of lipopolysaccharide - stimulated peripheral blood leukocytes . amino acid sequence determination revealed that mpf - 4 shares homology with platelet factor - 4 beginning at n - terminal residue 17 . cpf - 4 consists of mpf - 4 disulfide bonded to the 16 n - terminal residues of platelet factor - 4 . both mpf - 4 and cpf - 4 are potent inhibitors of endothelial cell proliferation , approximately 10 - 100 fold more potent than native or recombinant platelet factor - 4 , making them useful in the treatment of angiogenic diseases .