48,85 Glycol-split residues act as carboxylated, flexible joints along the sulfated polysaccharide chains, thereby strengthening their binding to heparanase (Figure 4). This facilitates the best fit between the glycol-split molecule and the two basic heparin/HS-binding sites of heparanase. Heparin that is 100% N-acetylated and 25% glycol-split (which we #see more keyword# have named heparanase inhibitor-2 (HI-2)) (Figure 4) was found to be an
especially strong and specific inhibitor of heparanase, yielding 100% inhibition of its enzymatic activity at 10 nanomolar concentrations in vitro. Since glycol splitting also involves inactivation of the active site for antithrombin, compound HI-2 exhibits a very low or no anticoagulant activity. We have demonstrated the effectiveness Inhibitors,research,lifescience,medical of glycol-split heparinoids, including compound HI-2 (=100NA,R.OH), in suppressing the biological activity of heparanase, applying in-vivo models of inflammation,60 melanoma lung colonization (Figure 4),86 and myeloma tumor growth.58,83 Figure 4 A chemically modified, non-anticoagulant Inhibitors,research,lifescience,medical heparin is a potent inhibitor of heparanase enzymatic activity and melanoma lung colonization. Structure (top) and favored 3D conformation (bottom) of heparanase inhibitor 2 (HI-2) = heparin that is glycol-split … Random, high-throughput screening of chemical libraries and microbial
metabolites Inhibitors,research,lifescience,medical and rational design of compounds that block the heparanase active site or ligand-binding domain are among the approaches applied to develop effective heparanase inhibitors.77,78 Natural endogenous heparanase inhibitors may also be identified. Further defining the heparanase substrate specificity, catalytic and non-catalytic activities, as well as the enzyme crystal structure is needed for pursuing a more “rational” Inhibitors,research,lifescience,medical approach to develop effective and highly specific heparanase inhibiting
molecules. MOVING ANTIHEPARANASE THERAPY CLOSER TO REALITY Multiple myeloma is the second most prevalent hematologic malignancy. This B lymphoid malignancy is characterized by tumor cell infiltration of the bone-marrow, resulting in severe bone pain and osteolytic bone disease. Although progress in the treatment of myeloma patients has been made over the last decade, the overall survival of patients is still poor. In myeloma patients, heparanase enzymatic activity before was elevated in the bone-marrow plasma of 86% of patients examined,87 and gene array analysis showed elevated heparanase expression in 92% of myeloma patients.57 Heparanase up-regulation in myeloma patients was associated with elevated microvessel density and syndecan-1 expression.87 While heparanase is proangiogenic in myeloma, which is a common feature shared with solid tumors, heparanase regulation of syndecan-1 shedding has emerged as highly relevant to multiple myeloma progression.