MODULATION OF FIBROBLAST GROWTH FACTOR-II RECEPTOR-BINDING, DIMERIZATION, SIGNALING, AND ANGIOGENIC ACTIVITY BY A SYNTHETIC HEPARIN-MIMICKING POLYANIONIC COMPOUND

Heparan sulfate (HS) proteoglycans play a key role in cell proliferati on induced by basic fibroblast growth factor (FGF-2) and other heparin -binding growth factors. To modulate the involvement of HS, we have us ed a synthetic, nonsulfated polyanionic aromatic compound (RG-13577) t hat mimics functional features of heparin/HS. FGF-2-stimulated prolife ration of vascular endothelial cells was markedly inhibited in the pre sence of 5-10 mu g/ml compound RG-13577 (poly-4-hydroxyphenoxy acetic acid; Mr similar to 5 kD). Direct interaction between RG-13577 and FGF -2 was demonstrated by the ability of the former to compete with hepar in on binding to FGF-2, RG-13577 inhibited FGF-2 binding to soluble- a nd cell surface-FGF receptor 1 (FGFR1). Unlike heparin, RG-13577 alone failed to mediate dimerization of FGF-2, Moreover, it abrogated hepar in-mediated dimerization of FGF-2 and FGFR1, as well as FGF-2 mitogeni c activity in HS-deficient F32 lymphoid cells, The antiproliferative e ffect of compound RG-13577 was associated with abrogation of FGF-2-ind uced tyrosine phosphorylation of FGFR1 and of cytoplasmic proteins inv olved in FGF-2 signal transduction, such as p90 and mitogen-activated protein kinase, A more effective inhibition of tyrosine phosphorylatio n was obtained after removal of the cell surface HS by heparinase, In contrast, tyrosine phosphorylation of an similar to 200-kD protein was stimulated by RG-13577, but not by heparin or FGF-2, RG-13577 prevent ed microvessel outgrowth from rat aortic rings embedded in a collagen gel. Development of nontoxic polyanionic compounds may provide an effe ctive strategy to inhibit FGF-2-induced cell proliferation associated with angiogenesis, arteriosclerosis, and restenosis.