Immunomodulatory Activities of the Heparan Sulfate Mimetic PG545

Glycosaminoglycan microarrays for studying glycosaminoglycan-protein systems

More than 3000 proteins are now known to bind to glycosaminoglycans (GAGs). Yet, GAG-protein systems are rather poorly understood in terms of selectivity of recognition, molecular mechanism of action, and translational promise. High-throughput screening (HTS) technologies are critically needed for studying GAG biology and developing GAG-based therapeutics. Microarrays, developed within the past two decades, have now improved to the point of being the preferred tool in the HTS of biomolecules. GAG microarrays, in which GAG sequences are immobilized on slides, while similar to other microarrays, have their own sets of challenges and considerations. GAG microarrays are rapidly becoming the first choice in studying GAG-protein systems. Here, we review different modalities and applications of GAG microarrays presented to date. We discuss advantages and disadvantages of this technology, explain covalent and non-covalent immobilization strategies using different chemically reactive groups, and present various assay formats for qualitative and quantitative interpretations, including selectivity screening, binding affinity studies, competitive binding studies etc. We also highlight recent advances in implementing this technology, cataloging of data, and project its future promise. Overall, the technology of GAG microarray exhibits enormous potential of evolving into more than a mere screening tool for studying GAG - protein systems.

Potential roles of heparanase in cancer therapy: Current trends and future direction

Heparanase (HPSE; heparanase-1) is an endo-β-glucuronidase capable of degrading the carbohydrate moiety of heparan sulfate proteoglycans, thus modulating and facilitating the remodeling of the extracellular matrix and basement membrane. HPSE activity is strongly associated with major human pathological complications, including but not limited to tumor progress and angiogenesis. Several lines of literature have shown that overexpression of HPSE leads to enhanced tumor growth and metastatic transmission, as well as poor prognosis. Gene silencing of HPSE or treatment of tumor with compounds that block HPSE activity are shown to remarkably attenuate tumor progression. Therefore, targeting HPSE is considered as a potential therapeutical strategy for the treatment of cancer. Intriguingly, recent findings disclose that heparanase-2 (HPSE-2), a close homolog of HPSE but lacking enzymatic activity, can also regulate antitumor mechanisms. Given the pleiotropic roles of HPSE, further investigation is in demand to determine the precise mechanism of regulating action of HPSE in different cancer settings. In this review, we first summarize the current understanding of HPSE, such as its structure, subcellular localization, and tissue distribution. Furthermore, we systematically review the pro- and antitumorigenic roles and mechanisms of HPSE in cancer progress. In addition, we delineate HPSE inhibitors that have entered clinical trials and their therapeutic potential.

Sulfation Code and Conformational Plasticity of l-Iduronic Acid Homo-Oligosaccharides Mimic the Biological Functions of Heparan Sulfate

Recently, the activity of heparan sulfate (HS) has led to the discovery of many drug candidates that have the potential to impact both medical science and human health. However, structural diversity and synthetic challenges impede the progress of HS research. Here, we report a library of novel l-iduronic acid (IdoA)-based HS mimics that are highly tunable in conformation plasticity and sulfation patterns to produce many of the functions of native HS oligosaccharides. The NMR analysis of HS mimics confirmed that 4-O-sulfation enhances the population of the ¹C₄ geometry. Interestingly, the ¹C₄ conformer becomes exclusive upon additional 2-O-sulfation. HS mimic microarray binding studies with different growth factors showed that selectivity and avidity are greatly modulated by the oligosaccharide length, sulfation code, and IdoA conformation. Particularly, we have identified 4-O-sulfated IdoA disaccharide (I-21) as a potential ligand for vascular endothelial growth factor (VEGF₁₆₅), which in a multivalent display modulated endothelial cell proliferation, migration, and angiogenesis. Overall, these results encourage the consideration of HS mimics for therapeutic applications.

Heparan Sulfate Mimetics Differentially Affect Homologous Chemokines and Attenuate Cancer Development

Achieving selective inhibition of chemokine activity by structurally well-defined heparan sulfate (HS) or HS mimetic molecules can provide important insights into their roles in individual physiological and pathological cellular processes. Here, we report a novel tailor-made HS mimetic, which furnishes an exclusive iduronic acid (IdoA) scaffold with different sulfation patterns and oligosaccharide chain lengths as potential ligands to target chemokines. Notably, highly sulfated-IdoA tetrasaccharide (I-45) exhibited strong binding to CCL2 chemokine thereby blocking CCL2/CCR2-mediated in vitro cancer cell invasion and metastasis. Taken together, IdoA-based HS mimetics offer an alternative HS substrate to generate selective and efficient inhibitors for chemokines and pave the way to a wide range of new therapeutic applications in cancer biology and immunology.