Antiproliferative activity to vascular smooth muscle cells and receptor binding of heparin-mimicking polyaromatic anionic compounds.

Abstract

Proliferation of bovine aortic smooth muscle cells (SMCs) induced by thrombin, basic fibroblast growth factor, or serum is inhibited by anionic, nonsulfated aromatic compounds that mimic many of the effects of heparin. Among these compounds are aurintricarboxylic acid (ATA) and a newly synthesized polymer of 4-hydroxyphenoxy acetic acid (compound RG-13577). Iodinated-or 14 C-labeled compound RG-13577 binds to cultured SMCs in a highly specific and saturable manner. Scatchard analysis of the binding data revealed the presence of an estimated lxlO 7 binding sites per cell with an apparent dissociation constant of 3xlO~6 mol/L. Binding of radiolabeled RG-13577 was efficiently competed for by related aromatic anionic compounds and by apolipoprotein E, but not by heparin, heparan sulfate, suramin, or various purified growth factors and extracellular matrix proteins.

Modulation of fibroblast growth factor-2 receptor binding, dimerization, signaling, and angiogenic activity by a synthetic heparin-mimicking polyanionic compound.

“…To our knowledge, this effect of suramin and RG-13577 is among the few demonstrations of enhanced tyrosine phosphorylation by nonpeptide chemical compounds. Both suramin (8)(9)(10)41) and RG-13577 (18,19) were reported to inhibit the growth-promoting activity of FGF-2 and to reverse FGF-2-mediated cell transformation. Suramin, however, is a sulfated molecule effective at much higher concentrations as compared with RG-13577 (9,49).…”

“…Apart from its ability to inhibit FGF-2-stimulated tyrosine phosphorylation, the antiproliferative effect of RG-13577 may also be attributed to tyrosine phosphorylation of a protein (i.e., p200) that serves as a cell surface receptor that may activate an inhibitory signal transduction pathway. In fact, RG-13577 binds to vascular smooth muscle cells in a saturable manner (K d ϭ ‫ف‬ 3 ϫ 10 Ϫ6 M), although its putative cell surface receptor has not been identified (19). RG-13577 receptormediated inhibitory pathway may be held responsible for FGF independent inhibition of cell proliferation induced by growthpromoting factors (i.e., thrombin, PDGF) (19), whose signaling is not enhanced by heparin/HS.…”

“…In fact, RG-13577 binds to vascular smooth muscle cells in a saturable manner (K d ϭ ‫ف‬ 3 ϫ 10 Ϫ6 M), although its putative cell surface receptor has not been identified (19). RG-13577 receptormediated inhibitory pathway may be held responsible for FGF independent inhibition of cell proliferation induced by growthpromoting factors (i.e., thrombin, PDGF) (19), whose signaling is not enhanced by heparin/HS. These results indicate that the mode of action of RG-13577 is more complex than a simple abrogation of certain steps in the FGF-2 signaling cascade.…”

“…The potent antiproliferative effect of RG-13577 on vascular smooth muscle cells (19) and endothelial cells is of potential clinical application in processes such as restenosis, accelerated atherosclerosis, and angiogenesis. In support is the observation that RG-13577 markedly inhibited the outgrowth of microvessels from aortic rings embedded in a collagen gel.…”

“…Using this approach, a series of polyanionic polymers was identified with repeating phenol-based monomers, including poly-4-hydroxyphenoxy acetic acid, hereby termed compound RG-13577, that mimics various effects of heparin. Some of these nontoxic, nonsulfated linear polyanionic compounds were found to revert the transformed phenotype of FGF-2-transfected cells (18) and inhibit the proliferation of vascular smooth muscle cells induced by thrombin, FGF-2, and serum (19).…”