In a proliferating tumor, locally secreted polypeptide growth factors, which have autocrine and paracrine functions, induce vascularization essential for tumor growth and metastasis. These growth factors may serve as targets for tumor therapy. We have shown that the heparinoid pentosan polysulfate (PPS) can block growth of subcutaneous human tumor xenografts in nude mice and angiogenesis induced by the heparin-binding, Kaposi's sarcoma-derived fibroblast growth factor (K-FGF).