Undersulfated and Glycol-Split Heparins Endowed with Antiangiogenic Activity

Abstract

Tumor neovascularization (angiogenesis) is regarded as a promising target for anticancer drugs. Heparin binds to fibroblast growth factor-2 (FGF2) and promotes the formation of ternary complexes with endothelial cell surface receptors, inducing an angiogenic response. As a novel strategy to generate antiangiogenic substances exploiting binding to FGF2 while preventing FGF receptor (FGFR) activation, sulfation gaps were generated along the heparin chains by controlled alkali-catalyzed removal of sulfate groups of iduronic acid 2-O-sulfate residues, giving rise to the corresponding epoxide derivatives. A new class of heparin derivatives was then obtained by opening the epoxide rings followed by oxidative glycol-splitting of the newly formed (and the preexisting) nonsulfated uronic acid residues. In vitro these heparin derivatives prevent the formation of FGFR/FGF2/heparan sulfate proteoglycan ternary complexes and inhibit FGF2-stimulated endothelial cell proliferation. They exert an antiangiogenic activity in the chick embryo chorioallantoic membrane assay, where the parent heparin is inactive. Low and very low molecular weight derivatives of a prototype compound, as well as its glycine and taurine derivatives obtained by reductive amination of glycol-split residues, retained the angiostatic activity. A significant relationship was found between the extent of glycol-splitting and the FGF2-antagonist/angiostatic activities of these heparin derivatives. Molecular dynamics calculations support the assumption that glycol-split residues act as flexible joints that, while favoring 1:1 binding to FGF2, disrupt the linearity of heparin chains necessary for formation of active complexes with FGFRs.

Modulation of the Heparanase-inhibiting Activity of Heparin through Selective Desulfation, Graded N-Acetylation, and Glycol Splitting

“…When framing heparin sequences that bind FGF-2, glycol-split residues were shown not to impair the binding to FGF-2. However, they prevented activation of FGF-2 and FGF-2-induced angiogenic activity (37,38). The present study shows that glycol splitting enhances the heparanase-inhibiting activity of heparin.…”

“…In the present study, relationships between structure and heparanase-inhibiting activity of heparin were studied using a larger number of heparins and heparin derivatives, including some with various degrees of 6-O-sulfation of GlcN and 2-O-sulfation of IdoA residues as well as "glycol-split" derivatives obtained by controlled periodate oxidation/borohydride reduction of natural (36) or partially 2-O-desulfated heparins (37,38). Glycol splitting of C-2-C-3 bonds of nonsulfated uronic acid residues was suggested to interfere with the biological interactions of heparin by providing flexible joints between protein binding sequences (37)(38)(39). When framing heparin sequences that bind FGF-2, glycol-split residues were shown not to impair the binding to FGF-2.…”

Heparanase 2 Interacts with Heparan Sulfate with High Affinity and Inhibits Heparanase Activity

“…Attempts to inhibit heparanase were initiated in parallel with the emergence clinical relevance of this activity, focusing on heparin and heparin mimetics, which bind heparanase with high affinity but serve as poor substrates (9,32). Two types of endogenous inhibitors of heparanase have so far been reported, namely disaccharide end products of HS cleavage (33) and highly basic proteins such as eosinophil major basic protein (34).…”

Old and new applications of non-anticoagulant heparin

“…[99] Astenose Adjuvant in cardiovascular intervention c [113] ROH Heparanase antiangiogenesis inhibitor b [114] ROH P selectin inhibitor [115] LAC-HP antimetastatic b [116] ROH Integrin-melanoma cell binding inhibitor a [117] ROH Antianemic as hepicdine inhibitor b [118] ROH Antinflammation-human elastase inhibitors a [118] gs-LMWH ORG 31733 HIV-1 and HIV-2 inhibitor a [120] SR 80258 Allergic airway response inhibitor b [121] Vasoflux Anticoagulant independent from AT activity, coadjuvant in myocardial infarction therapy d [108,109] NAC from Tinzaparin Antimetastatic b [122] gs-LMWH antimalarial, parasite adhesion, inhibitor b [44] DF01 -Tafoxiparin Labor pain attenuation d [111] M-402 Nocuparanib Metastasis and multiple pathway inhibitor d [110] DFX 232-Sevuparin Antimalarial, distrupting "Plasmodium falciparium" rosettes d [112]]-Preventive activity of vasoocclusion in sickle severe hereditary anemia d S-NACH Anticancer increasing tumor chemo-responsiveness c [35] gs-ULMWH RO-Fondaparinux Antinflammation b [123] Undersulfated RO ST1514" Antinflammatory -heparanase inhibitor b [124] Antiangiogenic, as FGF-2 and VEGF inhibitors b [125,126] N-acylated gs-heparins …”