Undersulfated, low-molecular-weight glycol-split heparin as an antiangiogenic VEGF antagonist

Synthesis and Biological Profiling of Seven Heparin and Heparan Sulphate Analogue Trisaccharides

Researchers are paying increasing attention to the strongly negatively charged heteropolysaccharides in cells, in the extracellular matrix or in the cell wall. Examples of such molecules are glycosaminoglycans (e.g., heparin, heparan sulphate). It is well known from the literature that heparin and its derivatives have anti-inflammatory, angiogenic, metastatic and growth factor inhibitory activity. Herein, we present the efficient synthesis of six non-glycosaminoglycan (Glc-GlcA-Glc-sequenced) and one heparin-related (GlcN-GlcA-Glc-sequenced) trisaccharides with various functional group patterns. The anti-inflammatory, antioxidant and cell growth-inhibitory/cytotoxic effects of the synthesized compounds were tested. Among the investigated molecules, we have found some derivatives with a promising anti-inflammatory and antioxidant effect.

Synthesis and Cell Growth Inhibitory Activity of Six Non-glycosaminoglycan-Type Heparin-Analogue Trisaccharides

The design and synthesis of heparin mimetics with high anticancer activity but no anticoagulant activity is an important task in medicinal chemistry. Herein, we present the efficient synthesis of five Glc-GlcA-Glc-sequenced and one Glc-IdoA-Glc-sequenced non-glycosaminoglycan, heparin-related trisaccharides with various sulfation/sulfonylation and methylation patterns. The cell growth inhibitory effects of the compounds were tested against four cancerous human cell lines and two non-cancerous cell lines. Two d-glucuronate-containing tetra-O-sulfated, partially methylated trisaccharides displayed remarkable and selective inhibitory effects on the growth of ovary carcinoma (A2780) and melanoma (WM35) cells. Methyl substituents on the glucuronide unit proved to be detrimental, whereas acetyl substituents were beneficial to the cytostatic activity of the sulfated derivatives.

Repurposing Heparin as Antimalarial: Evaluation of Multiple Modifications Toward In Vivo Application

Heparin is a promising antimalarial drug due to its activity in inhibiting Plasmodium invasion of red blood cells and to the lack of resistance evolution by the parasite against it, but its potent anticoagulant activity is preventing the advance of heparin along the clinical pipeline. We have determined, in in vitro Plasmodium falciparum cultures, the antimalarial activity of heparin-derived structures of different origins and sizes, to obtain formulations having a good balance of in vitro safety (neither cytotoxic nor hemolytic), low anticoagulant activity (≤23 IU/mL according to activated partial thromboplastin time assays), and not too low antimalarial activity (IC50 at least around 100 µg/mL). This led to the selection of five chemically modified heparins according to the parameters explored, i.e., chain length, sulfation degree and position, and glycol-split, and whose in vivo toxicity indicated their safety for mice up to an intravenous dose of 320 mg/kg. The in vivo antimalarial activity of the selected formulations was poor as a consequence of their short blood half-life. The covalent crosslinking of heparin onto the surface of polyethylene glycol-containing liposomes did not affect its antimalarial activity in vitro and provided higher initial plasma concentrations, although it did not increase mean circulation time. Finding a suitable nanocarrier to impart long blood residence times to the modified heparins described here will be the next step toward new heparin-based antimalarial strategies.

Modulation of angiogenesis by topical application of leptin and high and low molecular heparin using the Japanese quail chorioallantoic membrane model

Pathological angiogenesis characterized by uncontrollable vessel growth is an accompanying feature of many diseases. The avian embryo chorioallantoic membrane (CAM) is an excellent model for angiogenesis research. In our study we used a less common Japanese quail CAM model for the testing of angiogenic potential of leptin, high-molecular (heparin sodium) andlow-molecular (nadroparin calcium) heparins. Heparins play a significant role in vascular endothelial cell function, and they are able to modulate the activities of angiogenic growth factors. On embryonic day 7 leptin (5 μg per CAM), heparin sodium (75 IU per CAM) and nadroparin calcium (47.5 IU per CAM) in 500 μl PBS were applied on the CAM surface. After 24 h the fractal dimension (Df) of the vasculature was evaluated. Samples from each group were histologically analyzed and VEGF-A and Quek1 expression were detected by qPCR. Df was significantly increased in the leptin group. A moderate stimulatory effect of heparin sodium and an inhibitory effect of nadroparin calcium were observed. Both leptin and heparin sodium caused a noticeable increase in the CAM thickness compared to the control and nadroparin calcium groups. We observed an increased number of blood vessels and accumulation of fibroblasts. There was no significant impact on gene expression of VEGF-A and Quek1 24 h after treatment, however, trends similar to the changes in Df and CAM thickness were present. The resulting effect of nadroparin administration on Quek1 levels was exactly the opposite to that of leptin (p < 0.05).

The Challenge of Modulating Heparan Sulfate Turnover by Multitarget Heparin Derivatives

This review comes as a part of the special issue "Emerging frontiers in GAGs and mimetics". Our interest is in the manipulation of heparan sulfate (HS) turnover by employing HS mimetics/heparin derivatives that exert pleiotropic effects and are interesting for interfering at multiple levels with pathways in which HS is implicated. Due to the important role of heparanase in HS post-biosynthetic modification and catabolism, we focus on the possibility to target heparanase, at both extracellular and intracellular levels, a strategy that can be applied to many conditions, from inflammation to cancer and neurodegeneration.

Non-Anticoagulant Heparins as Heparanase Inhibitors

The chapter will review early and more recent seminal contributions to the discovery and characterization of heparanase and non-anticoagulant heparins inhibiting its peculiar enzymatic activity. Indeed, heparanase displays a unique versatility in degrading heparan sulfate chains of several proteoglycans expressed in all mammalian cells. This endo-β-D-glucuronidase is overexpressed in cancer, inflammation, diabetes, atherosclerosis, nephropathies and other pathologies. Starting from known low- or non-anticoagulant heparins, the search for heparanase inhibitors evolved focusing on structure-activity relationship studies and taking advantage of new chemical-physical analytical methods which have allowed characterization and sequencing of polysaccharide chains. New methods to screen heparanase inhibitors and to evaluate their mechanism of action and in vivo activity in experimental models prompted their development. New non-anticoagulant heparin derivatives endowed with anti-heparanase activity are reported. Some leads are under clinical evaluation in the oncology field (e.g., acute myeloid leukemia, multiple myeloma, pancreatic carcinoma) and in other pathological conditions (e.g., sickle cell disease, malaria, labor arrest).

Targeting malaria parasite invasion of red blood cells as an antimalarial strategy

Plasmodium spp. parasites that cause malaria disease remain a significant global-health burden. With the spread of parasites resistant to artemisinin combination therapies in Southeast Asia, there is a growing need to develop new antimalarials with novel targets. Invasion of the red blood cell by Plasmodium merozoites is essential for parasite survival and proliferation, thus representing an attractive target for therapeutic development. Red blood cell invasion requires a co-ordinated series of protein/protein interactions, protease cleavage events, intracellular signals, organelle release and engagement of an actin-myosin motor, which provide many potential targets for drug development. As these steps occur in the bloodstream, they are directly susceptible and exposed to drugs. A number of invasion inhibitors against a diverse range of parasite proteins involved in these different processes of invasion have been identified, with several showing potential to be optimised for improved drug-like properties. In this review, we discuss red blood cell invasion as a drug target and highlight a number of approaches for developing antimalarials with invasion inhibitory activity to use in future combination therapies.

Heparan Sulfate Mimetics in Cancer Therapy: The Challenge to Define Structural Determinants and the Relevance of Targets for Optimal Activity

Beyond anticoagulation, the therapeutic potential of heparin derivatives and heparan sulfate (HS) mimetics (functionally defined HS mimetics) in oncology is related to their ability to bind and modulate the function of a vast array of HS-binding proteins with pivotal roles in cancer growth and progression. The definition of structural/functional determinants and the introduction of chemical modifications enabled heparin derivatives to be identified with greatly reduced or absent anticoagulant activity, but conserved/enhanced anticancer activity. These studies paved the way for the disclosure of structural requirements for the inhibitory effects of HS mimetics on heparanase, selectins, and growth factor receptor signaling, as well as for the limitation of side effects. Actually, HS mimetics affect the tumor biological behavior via a multi-target mechanism of action based on their effects on tumor cells and various components of the tumor microenvironment. Emerging evidence indicates that immunomodulation can participate in the antitumor activity of these agents. Significant ability to enhance the antitumor effects of combination treatments with standard therapies was shown in several tumor models. While the first HS mimetics are undergoing early clinical evaluation, an improved understanding of the molecular contexts favoring the antitumor action in certain malignancies or subgroups is needed to fully exploit their potential.

Heparin impairs angiogenic signaling and compensatory lung growth after left pneumonectomy

Children with hypoplastic lung diseases, such as congenital diaphragmatic hernia, can require life support via extracorporeal membrane oxygenation and systemic anticoagulation, usually in the form of heparin. The role of heparin in angiogenesis and organ growth is inconclusive, with conflicting data reported in the literature. This study aimed to investigate the effects of heparin on lung growth in a model of compensatory lung growth (CLG). Compared to the absence of heparin, treatment with heparin decreased the vascular endothelial growth factor (VEGF)-mediated activation of VEGFR2 and mitogenic effect on human lung microvascular endothelial cells in vitro. Compared to non-heparinized controls, heparinized mice demonstrated impaired pulmonary mechanics, decreased respiratory volumes and flows, and reduced activity levels after left pneumonectomy. They also had lower lung volume, pulmonary septal surface area and alveolar density on morphometric analyses. Lungs of heparinized mice displayed decreased phosphorylation of VEGFR2 compared to the control group, with consequential downstream reduction in markers of cellular proliferation and survival. The use of bivalirudin, an alternative anticoagulant that does not interact with VEGF, preserved lung growth and pulmonary mechanics. These results demonstrated that heparin impairs CLG by reducing VEGFR2 activation. These findings raise concern for the clinical use of heparin in the setting of organ growth or regeneration.

Identification of Heparin Modifications and Polysaccharide Inhibitors of Plasmodium falciparum Merozoite Invasion That Have Potential for Novel Drug Development

Despite recent successful control efforts, malaria remains a leading global health burden. Alarmingly, resistance to current antimalarials is increasing and the development of new drug families is needed to maintain malaria control. Current antimalarials target the intraerythrocytic developmental stage of the Plasmodium falciparum life cycle. However, the invasive extracellular parasite form, the merozoite, is also an attractive target for drug development. We have previously demonstrated that heparin-like molecules, including those with low molecular weights and low anticoagulant activities, are potent and specific inhibitors of merozoite invasion and blood-stage replication. Here we tested a large panel of heparin-like molecules and sulfated polysaccharides together with various modified chemical forms for their inhibitory activity against P. falciparum merozoite invasion. We identified chemical modifications that improve inhibitory activity and identified several additional sulfated polysaccharides with strong inhibitory activity. These studies have important implications for the further development of heparin-like molecules as antimalarial drugs and for understanding merozoite invasion.

N-tert-butyloxycarbonyl-Phe-Leu-Phe-Leu-Phe (BOC2) inhibits the angiogenic activity of heparin-binding growth factors

The peptides N-tert-butyloxycarbonyl-Phe-Leu-Phe-Leu-Phe (BOC2) and BOC-Met-Leu-Phe (BOC1) are widely used antagonists of formyl peptide receptors (FPRs), BOC2 acting as an FPR1/FPR2 antagonist whereas BOC1 inhibits FPR1 only. Extensive investigations have been performed by using these FPR antagonists as a tool to assess the role of FPRs in physiological and pathological conditions. Based on previous observations from our laboratory, we assessed the possibility that BOC2 may exert also a direct inhibitory effect on the angiogenic activity of vascular endothelial growth factor-A (VEGF-A). Our data demonstrate that BOC2, but not BOC1, inhibits the angiogenic activity of heparin-binding VEGF-A₁₆₅ with no effect on the activity of the non-heparin-binding VEGF-A₁₂₁ isoform. Endothelial cell-based bioassays, surface plasmon resonance analysis, and computer modeling indicate that BOC2 may interact with the heparin-binding domain of VEGF-A₁₆₅, thus competing for heparin interaction and preventing the binding of VEGF-A₁₆₅ to tyrosine kinase receptor VEGFR2, its phosphorylation and downstream signaling. In addition, BOC2 inhibits the interaction of a variety of heparin-binding angiogenic growth factors with heparin, including fibroblast growth factor 2 (FGF2) whose angiogenic activity is blocked by the compound. Accordingly, BOC2 suppresses the angiogenic potential of human tumor cell lines that co-express VEGF-A and FGF2. Thus, BOC2 appears to act as a novel multi-heparin-binding growth factor antagonist. These findings caution about the interpretation of FPR-focusing experimental data obtained with this compound and set the basis for the design of novel BOC2-derived, FPR independent multi-target angiogenesis inhibitors.

Old and new applications of non-anticoagulant heparin

The aim of this chapter is to provide an overview of non-anticoagulant effects of heparins and their potential use in new therapeutic applications. Heparin and heparin derivatives have been tested in inflammatory, pulmonary and reproductive diseases, in cardiovascular, nephro- and neuro-tissue protection and repair, but also as agents against angiogenesis, atheroschlerosis, metastasis, protozoa and viruses. Targeting and inhibition of specific mediators involved in the inflammatory process, promoting some of the above mentioned pathologies, are reported along with recent studies of heparin conjugates and oral delivery systems. Some reports from the institute of the authors, such as those devoted to glycol-split heparins are also included. Among the members and derivatives of this class, several are undergoing clinical trials as antimetastatic and antimalarial agents and for the treatment of labour pain and severe hereditary anaemia. Other heparins, whose therapeutic targets are non-anticoagulant such as nephropathies, retinopathies and cystic fibrosis are also under investigation.

Blocking inhibition of prothrombinase by tissue factor pathway inhibitor alpha: a procoagulant property of heparins

Unfractionated heparin (UFH) has procoagulant activity in antithrombin/heparin cofactor II (HCII)-depleted plasma. UFH prevents tissue factor pathway inhibitor alpha (TFPIα) from inhibiting the procoagulant enzyme complex, prothrombinase, providing a possible mechanism for its procoagulant activity. The procoagulant potential of UFH and various low molecular weight heparins (LMWHs) were characterized for TFPIα dependence, using thrombin generation assays performed with antithrombin/HCII-depleted plasma. UFH, the LMWHs enoxaparin and dalteparin, and the low anticoagulant LMWH 2-O, 3-O desulphated heparin (ODSH) all promoted thrombin generation, but fondaparinux did not, and this activity was blocked by a TFPIα antibody. UFH, enoxaparin, and dalteparin were anticoagulant in reactions containing 1-2% normal plasma. In prothrombinase activity assays, UFH, enoxaparin, dalteparin and ODSH blocked prothrombinase inhibition by TFPIα, while again fondaparinux did not. In both the plasma and purified assays, LMWHs displayed greater procoagulant potential than UFH, even when normalized to saccharide concentration. These biochemical data reveal that UFH and LMWHs, but not fondaparinux, block prothrombinase inhibition by TFPIα, thereby producing their paradoxical procoagulant activity observed in the absence of antithrombin/HCII. The findings may help to understand the complex pathophysiology and treatment of patients that are simultaneously bleeding and clotting, such as those with disseminated intravascular coagulation.

Safety studies on intravenous infusion of a potent angiogenesis inhibitor: taurocholate-conjugated low molecular weight heparin derivative LHT7 in preclinical models

CONTEXT

As a class of angiogenesis inhibitors, heparin conjugates have shown significant effectiveness in several studies.

OBJECTIVES

The purpose of our current study is to evaluate the effectiveness and safety of infusing the conjugate of low molecular weight heparin and taurocholate (LHT7), which has been developed as a potent angiogenesis inhibitor.

METHODS

To evaluate its safety, the method of intravenous infusion was compared with its i.v. bolus administration. Intravenous infusion was administered at a rate of 400 μl/min/kg of body weight for 30 min. Pharmacokinetic (PK) analysis, organ accumulation, and plasma concentration profiles of LHT7 were measured. The anticancer effect of LHT7 was evaluated in murine and human xenograft models, and preclinical studies were performed in SD rats and beagle dogs.

RESULTS

The results of the PK studies showed reduced organ accumulation in mice and the AUC(0-96 h) (area under the curve) was increased up to 1485 ± 125 h × μg/ml. The efficacy, at dose 1 mg/kg/2 d was higher for i.v. infusion than for i.v. bolus administration in both murine and human cancer models. The preclinical studies showed the safety dose of LHT7 is less than 20 mg/kg in SD rats and in the next safety analysis in beagle dogs showed that there were no organ-specific adverse effects in higher doses, such as, 12 mg/kg. LHT7 showed sustained effects with minimized adverse events when administered through i.v. infusion.

CONCLUSIONS

LHT7 (i.v. infusion) could be safely used for further clinical development as a multi-targeting anti-angiogenic agent.

The interaction of heparan sulfate proteoglycans with endothelial transglutaminase-2 limits VEGF165-induced angiogenesis

Sprouting angiogenesis is stimulated by vascular endothelial growth factor (VEGF165) that is localized in the extracellular matrix (ECM) and binds to heparan sulfate (HS)-bearing proteins known as heparan sulfate proteoglycans (HSPGs). VEGF165 presentation by HSPGs enhances VEGF receptor-2 (VEGFR2) signaling. We investigated the effect of TG2, which binds to HSPGs, on the interaction between VEGF165 and HS and angiogenesis. Mice with tg2 deficiency showed transiently enhanced retina vessel formation and increased vascularization of VEGF165-containing Matrigel implants. In addition, endothelial cells in which TG2 was knocked down exhibited enhanced VEGF165-induced sprouting and migration, which was associated with increased phosphorylation of VEGFR2 at Tyr(951) and its targets Src and Akt. TG2 knockdown did not affect the phosphorylation of VEGFR2 at Tyr(1175) or cell proliferation in response to VEGF165 and sprouting or signaling in response to VEGF121. Decreased phosphorylation of VEGFR2 at Tyr(951) was due to ECM-localized TG2, which reduced the binding of VEGF165 to endothelial ECM in a manner that required its ability to bind to HS but not its catalytic activity. Surface plasmon resonance assays demonstrated that TG2 impeded the interaction between VEGF165 and HS. These results show that TG2 controls the formation of VEGF165-HSPG complexes and suggest that this regulation could be pharmacologically targeted to modulate developmental and therapeutic angiogenesis.

Therapeutic Potential of Anti-Angiogenic Multitarget N,O-Sulfated E. Coli K5 Polysaccharide in Diabetic Retinopathy

Vascular endothelial growth factor (VEGF) blockers have been developed for the treatment of proliferative diabetic retinopathy (PDR), the leading cause of visual impairments in the working-age population in the Western world. However, limitations to anti-VEGF therapies may exist because of the local production of other proangiogenic factors that may cause resistance to anti-VEGF interventions. Thus, novel therapeutic approaches targeting additional pathways are required. Here, we identified a sulfated derivative of the Escherichia coli polysaccharide K5 [K5-N,OS(H)] as a multitarget molecule highly effective in inhibiting VEGF-driven angiogenic responses in different in vitro, ex vivo, and in vivo assays, including a murine model of oxygen-induced retinopathy. Furthermore, K5-N,OS(H) binds a variety of heparin-binding angiogenic factors upregulated in PDR vitreous humor besides VEGF, thus inhibiting their biological activity. Finally, K5-N,OS(H) hampers the angiogenic activity exerted in vitro and in vivo by human vitreous fluid samples collected from patients with PDR. Together, the data provide compelling experimental evidence that K5-N,OS(H) represents an antiangiogenic multitarget molecule with potential implications for the therapy of pathologic neovessel formation in the retina of patients with PDR.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Angiogenic growth factors interactome and drug discovery: The contribution of surface plasmon resonance

Angiogenesis is implicated in several pathological conditions, including cancer, and in regenerative processes, including the formation of collateral blood vessels after stroke. Physiological angiogenesis is the outcome of a fine balance between the action of angiogenic growth factors (AGFs) and anti-angiogenic molecules, while pathological angiogenesis occurs when this balance is pushed toward AGFs. AGFs interact with multiple endothelial cell (EC) surface receptors inducing cell proliferation, migration and proteases upregulation. On the contrary, free or extracellular matrix-associated molecules inhibit angiogenesis by sequestering AGFs (thus hampering EC stimulation) or by interacting with specific EC receptors inducing apoptosis or decreasing responsiveness to AGFs. Thus, angiogenesis results from an intricate network of interactions among pro- and anti-angiogenic molecules, EC receptors and various modulators. All these interactions represent targets for the development of pro- or anti-angiogenic therapies. These aims call for suitable technologies to study the countless interactions occurring during neovascularization. Surface plasmon resonance (SPR) is a label-free optical technique to study biomolecular interactions in real time. It has become the golden standard technology for interaction analysis in biomedical research, including angiogenesis. From a survey of the literature it emerges that SPR has already contributed substantially to the better understanding of the neovascularization process, laying the basis for the decoding of the angiogenesis "interactome" and the identification of "hub molecules" that may represent preferential targets for an efficacious modulation of angiogenesis. Here, the still unexploited full potential of SPR is enlightened, pointing to improvements in its use for a deeper understanding of the mechanisms of neovascularization and the identification of novel anti-angiogenic drugs.

An apoptosis-homing peptide-conjugated low molecular weight heparin-taurocholate conjugate with antitumor properties

Various angiogenesis inhibitors and apoptosis-targeting agents have been therapeutically applied in preclinical cancer models, some of which have been tested in clinical trials. In a previous study, we demonstrated that LHT7, a low molecular weight heparin (LMWH)-taurocholate conjugate, has strong antiangiogenic and tumor-suppressive activity and diminished anticoagulant properties. In this study, we developed LHT7-ApoPep-1, an apoptosis-homing peptide-conjugated variant of LHT7. LHT7-ApoPep-1 exhibited antiangiogenic activity in endothelial cell tube-formation assays and apoptotic cell-targeting ability in tumor cell binding assays; it also showed little toxicity toward healthy cells. Administration of LHT7-ApoPep-1 in mouse xenograft models of breast carcinoma delayed tumor growth compared to LHT7-only, and histological evaluations revealed decreased vessel formation and increased apoptotic area in tumor tissues. Moreover, an examination of LHT7-ApoPep-1-Cy7.5 localization within the body using in vivo live imaging showed accumulation at the tumor site of tumor-bearing mice, with a more prolonged circulation time and enhanced intensity compared to LHT7-Cy7.5. Inspection of the tumor microenvironment revealed that Cy5.5-labeled LHT7-ApoPep-1 was located on and near CD31-positive vessels in tumor tissue. We conclude that LHT7-ApoPep-1 has antiangiogenic and apoptosis-targeting properties and exerts antitumor effects by suppressing tumor vessel growth and homing to apoptotic cells within the tumor.

Profiling glycol-split heparins by high-performance liquid chromatography/mass spectrometry analysis of their heparinase-generated oligosaccharides

Glycol-split (gs) heparins, obtained by periodate oxidation/borohydride reduction of heparin currently used as an anticoagulant and antithrombotic drug, are arousing increasing interest in anticancer and anti-inflammation therapies. These new medical uses are favored by the loss of anticoagulant activity associated with glycol-splitting-induced inactivation of the antithrombin III (AT) binding site. The structure of gs heparins has not been studied yet in detail. In this work, ion pair reversed-phase high-performance liquid chromatography (IPRP-HPLC) coupled with electrospray ionization mass spectrometry (ESI-MS) widely used for unmodified heparin has been adapted to the analysis of oligosaccharides generated by digestion with heparinases of gs heparins usually prepared from porcine mucosal heparin. The method was also found to be very effective in analyzing gs derivatives obtained from heparins of different animal and tissue origins. Besides the major 2-O-sulfated disaccharides, heparinase digests of gs heparins contain mainly tetra- and hexasaccharides incorporating one or two gs residues, with distribution patterns typical for individual gs heparins. A heptasulfated, mono-N-acetylated hexasaccharide with two gs residues was shown to be a marker of the gs-modified AT binding site within heparin chains.

Potentiation of anti-angiogenic activity of heparin by blocking the ATIII-interacting pentasaccharide unit and increasing net anionic charge

Heparin, a potent anticoagulant used for the prevention of venous thromboembolism, has been recognized as a tumor angiogenesis inhibitor. Its limitation in clinical application for cancer therapy, however, arises from its strong anticoagulant activity, which causes associated adverse effects. In this study, we show the structural correlation of LHT7, a previously developed heparin-based angiogenesis inhibitor, with its influence on VEGF blockade and its decreased anticoagulant activity. LHT7 was characterized as having average seven molecules of sodium taurocholates conjugated to one molecule of low-molecular-weight heparin (LMWH). This study showed that the conjugation of sodium taurocholates selectively blocked interaction with antithrombin III (ATIII) while enhancing the binding with VEGF. This resulted in LHT7 to have negligible anticoagulant activity but potent anti-angiogenic activity. Following up on this finding, we showed that the bidirectional effect of sodium taurocholate conjugation was due to its unique structure, that is, the sterane core hindering the ATIII-binding pentasaccharide unit of LMWH with its bulky and rigid structural characteristics while the terminal sulfate group interacts with VEGF to produce stronger binding. In addition, we showed that LHT7 was localized in the tumor, especially on the endothelial cells. One explanation for this might be that LHT7 was delivered to the tumor via platelets.

Effect of non-anticoagulant N-desulfated heparin on basic fibroblast growth factor expression, angiogenesis, and metastasis of gastric carcinoma in vitro and in vivo

Objective. The present study was performed to investigate the effect of N-desulfated heparin on basic fibroblast growth factor (bFGF) expression, tumor angiogenesis and metastasis of gastric carcinoma. Methods. Human gastric cancer SGC-7901 tissues were orthotopically implanted into the stomach of NOD SCID mice. Twenty mice were randomly divided into two groups which received either intravenous injection of 0.9% NaCl solution (normal saline group) or 10 mg/kg N-desulfated heparin (N-desulfated heparin group) twice weekly for three weeks. In vitro, human gastric carcinoma SGC-7901 cells were treated with N-desulfated heparin in different concentration (0.1 mg/mL, 1 mg/mL, N-desulfated heparin group), and treated with medium (control group). Results. In vivo, the tumor metastasis rates were 9/10 in normal saline group and 2/10 in N-desulfated heparin group (P < 0.05). The intratumoral microvessel density was higher in normal saline group than in N-desulfated heparin group (P < 0.05). bFGF expression in gastric tissue was inhibited by N-desulfated heparin (P < 0.05). There was no bleeding in N-desulfated heparin group. In vitro, N-desulfated heparin inhibited significantly bFGF protein and mRNA expression of gastric carcinoma cells (P < 0.05). Conclusions. N-desulfated heparin can inhibit the metastasis of gastric cancer through inhibiting tumor bFGF expression and tumor angiogenesis with no obvious anticoagulant activity.

Inhibitory effects of glycosaminoglycans on basal and stimulated transforming growth factor-β1 expression in mesangial cells: biochemical and structural considerations

A number of glycosaminoglycan (GAG) species related to heparin, dermatan sulfate (DeS) and chondroitin sulfate were tested for their ability to interfere with the physiological expression and/or pathological overexpression of the TGF-β1 gene. The influence of the molecular weight, molecular weight distribution, degree of sulfation and location of the sulfate groups was examined in an attempt to unveil fine relationships between structure and activity. The nature of the polysaccharide plays a major part, heparins proving able to inhibit both basal and stimulated TGF-β1 gene expression, DeSs being essentially inactive and chondroitin sulfates only inhibiting stimulated TGF-β1 gene expression. Within this frame, the particular physical and chemical properties of some GAGs appear to further modulate TGF-β1 gene response. Judging from our investigation, chondroitin sulfates seem the most promising for potential pharmacological applications in disorders characterized by fibrogenic TGF-β1 overexpression.

High antiangiogenic and low anticoagulant efficacy of orally active low molecular weight heparin derivatives

Heparin, an anticoagulant that is widely used clinically, is also known to bind to several kinds of proteins through electrostatic interactions because of its polyanionic character. These interactions are mediated by the physicochemical properties of heparin such as sequence composition, sulfation patterns, charge distribution, overall charge density, and molecular size. Although this electrostatic character mediates its binding to many proteins related with tumor progression, thereby providing its antiangiogenic property, the administration of heparin for treating cancer is limited in clinical applications due to several drawbacks, such as its low oral absorption, unsatisfactory therapeutic effects, and strong anticoagulant activity which induces hemorrhaging. Here, we evaluated novel, orally active, low molecular weight heparin (LMWH) derivatives (LHD) conjugated with deoxycholic acid (DOCA) that show reduced anticoagulant activity and enhanced antiangiogenic activity. The chemical conjugate of LMWH and DOCA was synthesized by conjugating the amine group of N-deoxycholylethylamine (EtDOCA) with the carboxylic groups of heparin at various DOCA conjugation ratios. The LMWH-DOCA conjugate series (LHD1, LHD1.5, LHD2, and LHD4) were further formulated with poloxamer 407 as a solubilizer for oral administration. An in vitro endothelial tubular formation and in vivo Matrigel plug assay were performed to verify the antiangiogenic potential of LHD. Finally, we evaluated tumor growth inhibition of oral LHD administration in a SCC7 model as well as in A549 human cancer cell lines in a mouse xenograft model. Increasing DOCA conjugation ratios showed decreased anticoagulant activity, eventually to zero. LHD could block angiogenesis in the tubular formation assay and the Matrigel plug assay. In particular, oral administration of LHD4, which has 4 molecules of DOCA per mole of LMWH, inhibited tumor growth in SCC7 mice model as well as A549 mice xenograft model. LHD4 was orally absorbable, showed minimal anticoagulant activity and inhibits tumor growth via antiangiogenesis. These findings demonstrate the therapeutic potential of LHD4 as a new oral anti-cancer drug.

Heparin-derived heparan sulfate mimics to modulate heparan sulfate-protein interaction in inflammation and cancer

The heparan sulfate (HS) chains of heparan sulfate proteoglycans (HSPG) are "ubiquitous" components of the cell surface and the extracellular matrix (EC) and play important roles in the physiopathology of developmental and homeostatic processes. Most biological properties of HS are mediated by interactions with "heparin-binding proteins" and can be modulated by exogenous heparin species (unmodified heparin, low molecular weight heparins, shorter heparin oligosaccharides and various non-anticoagulant derivatives of different sizes). Heparin species can promote or inhibit HS activities to different extents depending, among other factors, on how closely their structure mimics the biologically active HS sequences. Heparin shares structural similarities with HS, but is richer in "fully sulfated" sequences (S domains) that are usually the strongest binders to heparin/HS-binding proteins. On the other hand, HS is usually richer in less sulfated, N-acetylated sequences (NA domains). Some of the functions of HS chains, such as that of activating proteins by favoring their dimerization, often require short S sequences separated by rather long NA sequences. The biological activities of these species cannot be simulated by heparin, unless this polysaccharide is appropriately chemically/enzymatically modified or biotechnologically engineered. This mini review covers some information and concepts concerning the interactions of HS chains with heparin-binding proteins and some of the approaches for modulating HS interactions relevant to inflammation and cancer. This is approached through a few illustrative examples, including the interaction of HS and heparin-derived species with the chemokine IL-8, the growth factors FGF1 and FGF2, and the modulation of the activity of the enzyme heparanase by these species. Progresses in sequencing HS chains and reproducing them either by chemical synthesis or semi-synthesis, and in the elucidation of the 3D structure of oligosaccharide-protein complexes, are paving the way for rational approaches to the development of HS-inspired drugs in the field of inflammation and cancer, as well in other therapeutic fields.

The Chick Embryo Chorioallantoic Membrane as an In Vivo Assay to Study Antiangiogenesis

Antiangiogenesis, e.g., inhibition of blood vessel growth, is being investigated as a way to prevent the growth of tumors and other angiogenesis-dependent diseases. Pharmacological inhibition interferes with the angiogenic cascade or the immature neovasculature with synthetic or semi-synthetic substances, endogenous inhibitors or biological antagonists.The chick embryo chorioallantoic membrane (CAM) is an extraembryonic membrane, which serves as a gas exchange surface and its function is supported by a dense capillary network. Because its extensive vascularization and easy accessibility, CAM has been used to study morphofunctional aspects of the angiogenesis process in vivo and to study the efficacy and mechanism of action of pro- and anti-angiogenic molecules. The fields of application of CAM in the study of antiangiogenesis, including our personal experience, are illustrated in this review article.

Exploiting Surface Plasmon Resonance (SPR) Technology for the Identification of Fibroblast Growth Factor-2 (FGF2) Antagonists Endowed with Antiangiogenic Activity

Angiogenesis, the process of new blood vessel formation, is implicated in various physiological/pathological conditions, including embryonic development, inflammation and tumor growth. Fibroblast growth factor-2 (FGF2) is a heparin-binding angiogenic growth factor involved in various physiopathological processes, including tumor neovascularization. Accordingly, FGF2 is considered a target for antiangiogenic therapies. Thus, numerous natural/synthetic compounds have been tested for their capacity to bind and sequester FGF2 in the extracellular environment preventing its interaction with cellular receptors. We have exploited surface plasmon resonance (SPR) technique in search for antiangiogenic FGF2 binders/antagonists. In this review we will summarize our experience in SPR-based angiogenesis research, with the aim to validate SPR as a first line screening for the identification of antiangiogenic compounds.

Single walled carbon nanotubes as reporters for the optical detection of glucose

This article reviews current efforts to make glucose sensors based on the inherent optical properties of single walled carbon nanotubes. The advantages of single walled carbon nanotubes over traditional organic and nanoparticle fluorophores for in vivo-sensing applications are discussed. Two recent glucose sensors made by our group are described, with the first being an enzyme-based glucose sensor that couples a reaction mediator, which quenches nanotube fluorescence, on the surface of the nanotube with the reaction of the enzyme. The second sensor is based on competitive equilibrium binding between dextran-coated nanotubes and concanavalin A. The biocompatibility of a model sensor is examined using the chicken embryo chorioallantoic membrane as a tissue model. The advantages of measuring glucose concentration directly, like most optical sensors, versus measuring the flux in glucose concentration, like most electrochemical sensors, is discussed.

Non-anticoagulant heparins and inhibition of cancer

Low-molecular-weight heparins (LMWH) appear to prolong survival of patients with cancer. Such a beneficial effect is thought to be associated with interruption of molecular mechanisms involving the heparan sulfate (HS) chains of cell surface and extracellular matrix proteoglycans (HSPGs), growth factors and their receptors, heparanase, and selectins. The beneficial effects of heparin species could also be associated with their ability to release tissue factor pathway inhibitor from endothelium. The utility of heparin and LMWH as anticancer drugs is limited due to their anticoagulant properties. Non-anticoagulant heparins can be obtained either by removing chains containing the antithrombin-binding sequence, or by inactivating critical functional groups or units of this sequence. The non-anticoagulant heparins most extensively studied are regioselectively desulfated heparins and 'glycol-split' heparins. Some modified heparins of both types are potent inhibitors of heparanase. A number of them also attenuate metastasis in experimental models. With cancer cells overexpressing selectins, heparin-mediated inhibition of tumor cells-platelets aggregation and tumor cell interaction with the vascular endothelium appears to be the prevalent mechanism of attenuation of early stages of metastasis. The structural requirements for inhibition of growth factors, heparanase, and selectins by heparin derivatives are somewhat different for the different activities. An N-acetylated, glycol-split heparin provides an example of application of a non-anticoagulant heparin that inhibits cancer in animal models without unwanted side effects. Delivery of this compound to mice bearing established myeloma tumors dramatically blocked tumor growth and progression.

Polyanionic drugs and viral oncogenesis: a novel approach to control infection, tumor-associated inflammation and angiogenesis

Polyanionic macromolecules are extremely abundant both in the extracellular environment and inside the cell, where they are readily accessible to many proteins for interactions that play a variety of biological roles. Among polyanions, heparin, heparan sulfate proteoglycans (HSPGs) and glycosphingolipids (GSLs) are widely distributed in biological fluids, at the cell membrane and inside the cell, where they are implicated in several physiological and/or pathological processes such as infectious diseases, angiogenesis and tumor growth. At a molecular level, these processes are mainly mediated by microbial proteins, cytokines and receptors that exert their functions by binding to HSPGs and/or GSLs, suggesting the possibility to use polyanionic antagonists as efficient drugs for the treatment of infectious diseases and cancer. Polysulfated (PS) or polysulfonated (PSN) compounds are a heterogeneous group of natural, semi-synthetic or synthetic molecules whose prototypes are heparin and suramin. Different structural features confer to PS/PSN compounds the capacity to bind and inhibit the biological activities of those same heparin-binding proteins implicated in infectious diseases and cancer. In this review we will discuss the state of the art and the possible future development of polyanionic drugs in the treatment of infectious diseases and cancer.

Suppression of angiogenesis and tumor growth by orally active deoxycholic acid-heparin conjugate

Heparin, a potent inhibitor of blood coagulation, exhibits antitumoral action in tumor progression such as in angiogenesis and metastasis but is not orally absorbed in the body, making it an attractive candidate as an oral drug for antiangiogenic cancer therapy. We generated LHD or orally active heparin using low molecular weight heparin (LMWH) and deoxycholic acid that is effectively absorbed in the gastrointestinal tract. Using the in vitro endothelial tubular formation and chicken chorioallantoic membrane angiogenesis assay, we found that antiangiogenic activity of this LHD was similar to that of LMWH. From the in vivo Matrigel plugs assay, LHD treated orally could effectively inhibit angiogenesis into the plugs induced by basic fibroblast growth factor, whereas LMWH treated orally could not due to no oral absorption. In addition, when this LHD was orally administered into the tumor bearing mice, it significantly inhibited tumor growth by its antiangiogenic therapeutic mechanism, and when accompanied with doxorubicin, it appeared to have an additive effect. Collectively, LHD having antiangiogenic activity could be orally absorbable and inhibit tumor growth via inhibiting angiogenesis. These findings demonstrate the therapeutic potential of LHD in the clinical trials, which is suggested as a new oral therapeutic remedy for cancer therapy.

Profiling the Sulfation Specificities of Glycosaminoglycan Interactions with Growth Factors and Chemotactic Proteins Using Microarrays

We report a carbohydrate microarray-based approach for the rapid, facile analysis of glycosaminoglycan-protein interactions. The key structural determinants responsible for protein binding, such as sulfate groups that participate in the interactions, were elucidated. Specificities were also readily compared across protein families or functional classes, and comparisons among glycosaminoglycan subclasses provided a more comprehensive understanding of protein specificity. To validate the approach, we showed that fibroblast growth factor family members have distinct sulfation preferences. We also demonstrated that heparan sulfate and chondroitin sulfate interact in a sulfation-dependent manner with various axon guidance proteins, including slit2, netrin1, ephrinA1, ephrinA5, and semaphorin5B. We anticipate that these microarrays will accelerate the discovery of glycosaminoglycan-binding proteins and provide a deeper understanding of their roles in regulating diverse biological processes.

Effect of non-anticoagulant N-desulfated heparin on expression of vascular endothelial growth factor, angiogenesis and metastasis of orthotopic implantation of human gastric carcinoma

AIM: To investigate the effect of N-desulfated heparin on tumor metastasis and angiogenesis, and expression of vascular endothelial growth factor (VEGF) of orthotopic implantation of human gastric carcinoma in male severe combined immune deficiency (SCID) mice.

METHODS: Human gastric cancer SGC-7901 cells were orthotopically implanted into the stomach of SCID mice. The mice were randomly divided into normal saline group and N-desulfated heparin group. One week after operation, the mice in N-desulfated heparin group received i.v. injections of N-desulfated heparin (Shanghai Institute of Cell Biology, Chinese Academy of Sciences, 10 mg/kg.d) twice weekly for 3 wk. The mice in normal saline group received i.v. injections of normal saline (100 μL) twice weekly for 3 wk. The mice were sacrificed six weeks after implantation. Tumor metastasis was evaluated histologically for metastasis under microscope. Intratumoral microvessel density (MVD) and VEGF expression were evaluated immuohistochemically. VEGF mRNA expression in gastric tissue of SCID mice was detected by real time PCR.

RESULTS: The tumor metastasis rate was 80% in normal saline group and 20% in N-desulfated heparin group (P < 0.05). MVD was 8.0 ± 3.1 in normal saline group and 4.3 ± 1.8 in N-desulfated heparin group (P < 0.05). VEGF positive immunostaining was found in cytoplasm of cancer cells. The rate of VEGF positive expression was higher in normal saline group than in N-desulfated heparin treated group (90% vs 20%, P < 0.05). VEGF mRNA expression was significantly inhibited by N-desulfated heparin and was higher in normal saline group than in N-desulfated heparin group (Ct value 19.51 ± 1.01 vs 22.55 ± 1.36, P < 0.05). N-desulfated heparin significantly inhibited the expression of VEGF mRNA in cancer cells. No bleeding occurred in N-desulfated heparin group.

CONCLUSION: N-desulfated heparin can inhibit metastasis of gastric cancer by suppressing tumor VEGF expression and tumor angiogenesis, but has no obvious anticoagulant activity.

Extracellular angiogenic growth factor interactions: an angiogenesis interactome survey

Angiogenesis plays a key role in various physiological and pathological processes, including inflammation and tumor growth. Numerous angiogenic growth factors (AGFs) have been identified. Usually, the angiogenic process is assumed to represent the outcome of a straightforward interaction of AGFs with specific signalling receptors of the endothelial cell (EC) surface. Actually, the mechanisms by which AGFs induce neovascularization are much more complex. Indeed, angiogenesis is the result of the simultaneous actions of various AGFs and angiogenesis modulators; multiple EC surface receptors with different structure and biological properties are engaged by AGFs to exert a full angiogenic response; AGFs bind a variety of free and immobilized proteins, polysaccharides, and complex lipids of the extracellular milieu that affect AGF integrity, stability, and bioavailability; some of the AGF-binding molecules interact also with AGF receptors. In this review the authors summarize literature data and discuss the current knowledge about the extracellular molecules able to interact with AGFs, thus representing possible key regulators of the angiogenesis process and targets/templates for the development of novel antiangiogenic drugs. This work represents an attempt to highlight common theme in the AGF interactome that occurs at the extracellular level during neovascularization.

Semi-synthetic heparin derivatives: chemical modifications of heparin beyond chain length, sulfate substitution pattern and N-sulfo/N-acetyl groups

The glycosaminoglycan heparin is a polyanionic polysaccharide most recognized for its anticoagulant activity. Heparin binds to cationic regions in hundreds of prokaryotic and eukaryotic proteins, termed heparin-binding proteins. The endogenous ligand for many of these heparin-binding proteins is a structurally similar glycosaminoglycan, heparan sulfate (HS). Chemical and biosynthetic modifications of heparin and HS have been employed to discern specific sequences and charge-substitution patterns required for these polysaccharides to bind specific proteins, with the goal of understanding structural requirements for protein binding well enough to elucidate the function of the saccharide-protein interactions and/or to develop new or improved heparin-based pharmaceuticals. The most common modifications to heparin structure have been alteration of sulfate substitution patterns, carboxyl reduction, replacement N-sulfo groups with N-acetyl groups, and chain fragmentation. However, an accumulation of reports over the past 50 years describe semi-synthetic heparin derivatives obtained by incorporating aliphatic, aryl, and heteroaryl moieties into the heparin structure. A primary goal in many of these reports has been to identify heparin-derived structures as new or improved heparin-based therapeutics. Presented here is a perspective on the introduction of non-anionic structural motifs into heparin structure, with a focus on such modifications as a strategy to generate novel reduced-charge heparin-based bind-and-block antagonists of HS-protein interactions. The chemical methods employed to synthesize such derivatives, as well as other unique heparin conjugates, are reviewed.

Survey of the year 2005 commercial optical biosensor literature

We identified 1113 articles (103 reviews, 1010 primary research articles) published in 2005 that describe experiments performed using commercially available optical biosensors. While this number of publications is impressive, we find that the quality of the biosensor work in these articles is often pretty poor. It is a little disappointing that there appears to be only a small set of researchers who know how to properly perform, analyze, and present biosensor data. To help focus the field, we spotlight work published by 10 research groups that exemplify the quality of data one should expect to see from a biosensor experiment. Also, in an effort to raise awareness of the common problems in the biosensor field, we provide side-by-side examples of good and bad data sets from the 2005 literature.

Effect of N-desulfated heparin on angiogenesis and vascular endothelial growth factor expression in mice with severe combined immunodeficiency

AIM: To investigate the effect of N-desulfated heparin on tumor metastasis, angiogenesis, and expression of vascular endothelial growth factor (VEGF) after ortho-topic implantation of human gastric carcinoma in mice with severe combined immunodeficiency (SCID).

METHODS: The SCID mice metastasis model was established by in situ implantation of human gastric carcinoma tissue, then the mice were randomly divided into two groups: the normal saline group (treated with normal saline) and NNH group [treated with N-desulfat-ed heparin, 10 mg/(kg·d) iv, 2/wk, for 3 wk]. The mice were sacrificed 6 wk after the implantation. The tumor metastasis, intratumoral microvessel density (MVD), and VEGF expression were evaluated respectively..

RESULTS: The tumor metastasis rates were significan-tly different between normal saline and NNH group (80% vs 20%, P < 0.05). No side effect such as hemorrhage was observed in the mice. The MVD was 8.0 ± 3.1 in the normal saline group and 4.3 ± 1.8 in the NNH group, and there was significant difference between those 2 groups (P < 0.05). The positive rate of VEGF expressi-on was significantly higher in the normal saline group than that in the NNH group (90% vs 20%, P < 0.05).

CONCLUSION: N-desulfated heparin can inhibit the metastasis of gastric cancer through inhibiting the ex-pression of tumor VEGF and angiogenesis with no ob-vious side effect such as hemorrhage

Platelet-Mimicry of Cancer Cells: Epiphenomenon with Clinical Significance

Stem cell mimicry of cancer cells has been known for a long time and is considered to be responsible for ectopic gene expressions. The stem cell characteristics of tumor cells are shown to be involved in epithelial-mesenchymal transition and in the phenomenon of vascular mimicry. Certain cancer types acquire a geno-phenotype closely resembling the platelets and express several megakaryocytic genes (adhesion receptors alpha IIb beta 3, thrombin receptor and PECAM/CD 31 and/or platelet-type 12-LOX) able to activate the coagulation cascade or the platelets themselves. Here we define these potentials as platelet mimicry of cancer cells typical of pancreatic, breast, prostate, colorectal and urogenital cancers and melanoma. Data all support that platelet mimicry of certain cancer types is an important factor in their hematogenous dissemination and provides an attractive therapeutic target. Besides the long-available preclinical data, clinical trials have only recently provided evidence that targeting platelet mimicry of cancers is an efficient way to prevent tumor progression. The systematic discovery of the markers of platelet mimicry in various cancer types and their molecular targeting may provide new supportive therapeutic modalities for the management of the progressing disease.

The sweet and sour of cancer: glycans as novel therapeutic targets

A growing body of evidence supports crucial roles for glycans at various pathophysiological steps of tumour progression. Glycans regulate tumour proliferation, invasion, haematogenous metastasis and angiogenesis, and increased understanding of these roles sets the stage for developing pharmaceutical agents that target these molecules. Such novel agents might be used alone or in combination with operative and/or chemoradiation strategies for treating cancer.

Identification and characterization of heparin/heparan sulfate binding domains of the endoglycosidase heparanase

The endo-beta-glucuronidase, heparanase, is an enzyme that cleaves heparan sulfate at specific intra-chain sites, yielding heparan sulfate fragments with appreciable size and biological activities. Heparanase activity has been traditionally correlated with cell invasion associated with cancer metastasis, angiogenesis, and inflammation. In addition, heparanase up-regulation has been documented in a variety of primary human tumors, correlating with increased vascular density and poor postoperative survival, suggesting that heparanase may be considered as a target for anticancer drugs. In an attempt to identify the protein motif that would serve as a target for the development of heparanase inhibitors, we looked for protein domains that mediate the interaction of heparanase with its heparan sulfate substrate. We have identified three potential heparin binding domains and provided evidence that one of these is mapped at the N terminus of the 50-kDa active heparanase subunit. A peptide corresponding to this region (Lys(158)-Asp(171)) physically associates with heparin and heparan sulfate. Moreover, the peptide inhibited heparanase enzymatic activity in a dose-responsive manner, presumably through competition with the heparan sulfate substrate. Furthermore, antibodies directed to this region inhibited heparanase activity, and a deletion construct lacking this domain exhibited no enzymatic activity. NMR titration experiments confirmed residues Lys(158)-Asn(162) as amino acids that firmly bound heparin. Deletion of a second heparin binding domain sequence (Gln(270)-Lys(280)) yielded an inactive enzyme that failed to interact with cell surface heparan sulfate and hence accumulated in the culture medium of transfected HEK 293 cells to exceptionally high levels. The two heparin/heparan sulfate recognition domains are potentially attractive targets for the development of heparanase inhibitors.

Modulation of the heparanase-inhibiting activity of heparin through selective desulfation, graded N-acetylation, and glycol splitting

Heparanase is an endo-beta-glucuronidase that cleaves heparan sulfate (HS) chains of heparan sulfate proteoglycans on cell surfaces and in the extracellular matrix (ECM). Heparanase, overexpressed by most cancer cells, facilitates extravasation of blood-borne tumor cells and causes release of growth factors sequestered by HS chains, thus accelerating tumor growth and metastasis. Inhibition of heparanase with HS mimics is a promising target for a novel strategy in cancer therapy. In this study, in vitro inhibition of recombinant heparanase was determined for heparin derivatives differing in degrees of 2-O- and 6-O-sulfation, N-acetylation, and glycol splitting of nonsulfated uronic acid residues. The contemporaneous presence of sulfate groups at O-2 of IdoA and at O-6 of GlcN was found to be non-essential for effective inhibition of heparanase activity provided that one of the two positions retains a high degree of sulfation. N-Desulfation/ N-acetylation involved a marked decrease in the inhibitory activity for degrees of N-acetylation higher than 50%, suggesting that at least one NSO3 group per disaccharide unit is involved in interaction with the enzyme. On the other hand, glycol splitting of preexisting or of both preexisting and chemically generated nonsulfated uronic acids dramatically increased the heparanase-inhibiting activity irrespective of the degree of N-acetylation. Indeed N-acetylated heparins in their glycol-split forms inhibited heparanase as effectively as the corresponding N-sulfated derivatives. Whereas heparin and N-acetylheparins containing unmodified D-glucuronic acid residues inhibited heparanase by acting, at least in part, as substrates, their glycol-split derivatives were no more susceptible to cleavage by heparanase. Glycol-split N-acetylheparins did not release basic fibroblast growth factor from ECM and failed to stimulate its mitogenic activity. The combination of high inhibition of heparanase and low release/potentiation of ECM-bound growth factor indicates that N-acetylated, glycol-split heparins are potential antiangiogenic and antimetastatic agents that are more effective than their counterparts with unmodified backbones.