Heparanase uptake is mediated by cell membrane heparan sulfate proteoglycans

Chemical toolbox to interrogate Heparanase-1 activity

The development of a robust chemical toolbox to interrogate the activity of heparanase-1 (HPSE-1), an endo-β-d-glucuronidase and the only known enzyme that cleaves heparan sulfate (HS), has become critically important. The primary function of HPSE-1, cleaving HS side chains from heparan sulfate proteoglycans (HSPGs), regulates the integrity of the extracellular matrix (ECM) and the bioavailability of active, heparan sulfate-binding partners such as enzymes, growth factors, chemokines, and cytokines. HPSE-1 enzymatic activity is strictly regulated and has been found to play fundamental roles in pathophysiological processes. HPSE-1 is significantly overexpressed under various conditions including cancer, metastasis, angiogenesis, and inflammation, making HPSE-1 a promising therapeutic and diagnostic target. Chemical tools that can detect and image HPSE-1 activity in vitro and/or in vivo can help drive the discovery of novel and efficacious anti-HPSE-1 drugs, investigate the basic biology of HPSE-1, and help serve as a diagnostic tool in clinical applications. Here, we will give an overview of the common chemical tools to detect HPSE-1 activity and highlight the novel heparanase probes recently developed in our lab.

Impact of heparanase-2 (Hpa2) on cancer and inflammation: Advances and paradigms

HPSE2, the gene-encoding heparanase 2 (Hpa2), is mutated in urofacial syndrome (UFS), a rare autosomal recessive congenital disease attributed to peripheral neuropathy. Hpa2 lacks intrinsic heparan sulfate (HS)-degrading activity, the hallmark of heparanase (Hpa1), yet it exhibits a high affinity toward HS, thereby inhibiting Hpa1 enzymatic activity. Hpa2 regulates selected genes that promote normal differentiation, tissue homeostasis, and endoplasmic reticulum (ER) stress, resulting in antitumor, antiangiogenic, and anti-inflammatory effects. Importantly, stress conditions induce the expression of Hpa2, thus establishing a feedback loop, where Hpa2 enhances ER stress which, in turn, induces Hpa2 expression. In most cases, cancer patients who retain high levels of Hpa2 survive longer than patients bearing Hpa2-low tumors. Experimentally, overexpression of Hpa2 attenuates the growth of tumor xenografts, whereas Hpa2 gene silencing results in aggressive tumors. Studies applying conditional Hpa2 knockout (cHpa2-KO) mice revealed an essential involvement of Hpa2 contributed by the host in protecting against cancer and inflammation. This was best reflected by the distorted morphology of the Hpa2-null pancreas, including massive infiltration of immune cells, acinar to adipocyte trans-differentiation, and acinar to ductal metaplasia. Moreover, orthotopic inoculation of pancreatic ductal adenocarcinoma (PDAC) cells into the pancreas of Hpa2-null vs. wild-type mice yielded tumors that were by far more aggressive. Likewise, intravenous inoculation of cancer cells into cHpa2-KO mice resulted in a dramatically increased lung colonization reflecting the involvement of Hpa2 in restricting the formation of a premetastatic niche. Elucidating Hpa2 structure-activity-relationships is expected to support the development of Hpa2-based therapies against cancer and inflammation.

A Conditionally Activated Cytosol-Penetrating Antibody for TME-Dependent Intracellular Cargo Delivery

Currently, therapeutic and diagnostic applications of antibodies are primarily limited to cell surface-exposed and extracellular proteins. However, research has been conducted on cell-penetrating peptides (CPP), as well as cytosol-penetrating antibodies, to overcome these limitations. In this context, a heparin sulfate proteoglycan (HSPG)-binding antibody was serendipitously discovered, which eventually localizes to the cytosol of target cells. Functional characterization revealed that the tested antibody has beneficial cytosol-penetrating capabilities and can deliver cargo proteins (up to 70 kDa) to the cytosol. To achieve tumor-specific cell targeting and cargo delivery through conditional activation of the cell-penetrating antibody in the tumor microenvironment, a single-chain Fc fragment (scFv) and a VL domain were isolated as masking units. Several in vitro assays demonstrated that fusing the masking protein with a cleavable linker to the cell penetration antibody results in the inactivation of antibody cell binding and internalization. Removal of the mask via MMP-9 protease cleavage, a protease that is frequently overexpressed in the tumor microenvironment (TME), led to complete regeneration of binding and cytosol-penetrating capabilities. Masked and conditionally activated cytosol-penetrating antibodies have the potential to serve as a modular platform for delivering protein cargoes addressing intracellular targets in tumor cells.

A Fluorogenic Green Merocyanine-Based Probe to Detect Heparanase-1 Activity

Heparanase-1 (HPSE-1), an endo-β-D-glucuronidase, is an extracellular matrix (ECM) remodeling enzyme that degrades heparan sulfate (HS) chains of heparan sulfate proteoglycans (HSPGs). HPSE-1 functions to remodel the ECM and thereby disseminate cells, liberate HS-bound bioactive molecules, and release biologically active HS fragments. Being the only known enzyme for the cleavage of HS, HPSE-1 regulates a number of fundamental cellular processes including cell migration, cytokine regulation, angiogenesis, and wound healing. Overexpression of HPSE-1 has been discovered in most cancers, inflammatory diseases, viral infections, among others. As an emerging therapeutic target, the biological role of HPSE-1 remains to be explored but is hampered by a lack of research tools. To expand the chemical tool-kit of fluorogenic probes to interrogate HPSE-1 activity, we design and synthesized a fluorogenic green disaccharide-based HPSE-1 probe using our design strategy of tuning the electronic effect of the aryl aglycon. The novel probe exhibits a highly sensitive 278-fold fluorescence turn-on response in the presence of recombinant human HPSE-1, while emitting green light at 560 nm, enabling the fluorescence imaging of HPSE-1 activity in cells.

A New Synthesized Dicarboxylated Oxy-Heparin Efficiently Attenuates Tumor Growth and Metastasis

Heparanase (Hpa1) is expressed by tumor cells and cells of the tumor microenvironment and functions to remodel the extracellular matrix (ECM) and regulate the bioavailability of ECM-bound factors that support tumor growth. Heparanase expression is upregulated in human carcinomas, sarcomas, and hematological malignancies, correlating with increased tumor metastasis, vascular density, and shorter postoperative survival of cancer patients, and encouraging the development of heparanase inhibitors as anti-cancer drugs. Among these are heparin/HS mimetics, the only heparanase-inhibiting compounds that are being evaluated in clinical trials. We have synthesized dicarboxylated oxy-heparins (DCoxHs) containing three carboxylate groups per split residue (DC-Hep). The resulting lead compound (termed XII) was upscaled, characterized, and examined for its effectiveness in tumor models. Potent anti-tumorigenic effects were obtained in models of pancreatic carcinoma, breast cancer, mesothelioma, and myeloma, yielding tumor growth inhibition (TGI) values ranging from 21 to 70% and extending the survival time of the mice. Of particular significance was the inhibition of spontaneous metastasis in an orthotopic model of breast carcinoma following resection of the primary tumor. It appears that apart from inhibition of heparanase enzymatic activity, compound XII reduces the levels of heparanase protein and inhibits its cellular uptake and activation. Heparanase-dependent and -independent effects of XII are being investigated. Collectively, our pre-clinical studies with compound XII strongly justify its examination in cancer patients.

The role of heparan sulfate in enhancing the chemotherapeutic response in triple-negative breast cancer

Background

Among women worldwide, breast cancer has the highest incidence and is the leading cause of cancer-related death. Patients with the triple-negative breast cancer (TNBC) subtype have an inferior prognosis in comparison to other breast cancers because current therapies do not facilitate long-lasting responses. Thus, there is a demand for more innovative therapies that induce durable responses.In our previous research, we discovered that augmenting the concentration of extracellular ATP (eATP) greatly enhances the chemotherapeutic response of TNBC cell lines by activating purinergic receptors (P2RXs), leading to cell death through the induction of non-selective membrane permeability. However, eATP levels are limited by several classes of extracellular ATPases. One endogenous molecule of interest that can inhibit multiple classes of extracellular ATPases is heparan sulfate. Polysulfated polysaccharide heparan sulfate itself is degraded by heparanase, an enzyme that is known to be highly expressed in various cancers, including breast cancer. Heparan sulfate has previously been shown to regulate several cancer-related processes such as fibroblast growth factor signaling, neoangiogenesis by sequestering vascular endothelial growth factors in the extracellular matrix, hedgehog signaling and cell adhesion. In this project, we identified an additional mechanism for a tumor suppressor role of heparan sulfate: inhibition of extracellular ATPases, leading to augmented levels of eATP.Several heparanase inhibitors have been previously identified, including OGT 2115, suramin, PI-88, and PG 545. We hypothesized that heparanase inhibitors would augment eATP concentrations in TNBC by increasing heparan sulfate in the tumor microenvironment, resulting in enhanced cell death in response to chemotherapy.

Methods

We treated TNBC cell lines MDA-MB 231, Hs 578t, and MDA-MB 468 and non-tumorigenic immortal mammary epithelial MCF-10A cells with increasing concentrations of the chemotherapeutic agent paclitaxel in the presence of heparan sulfate and/or the heparanase inhibitor OGT 2115 while analyzing eATP release and cell viability. Moreover, to verify that the effects of OGT 2115 are mediated through eATP, we applied specific antagonists to the purinergic receptors P2RX4 and P2RX7. In addition, the protein expression of heparanase was compared in the cell lines by Western blot analysis. We also evaluated the consequences of this therapeutic strategy on the breast cancer-initiating cell population in the treated cells using flow cytometry and tumorsphere formation efficiency assays.

Results

Heparanase was found to be highly expressed in immortal mammary epithelial cells in comparison to TNBC cell lines. The heparanase inhibitor OGT 2115 augmented chemotherapy-induced TNBC cell death and eATP release.

Conclusion

These results demonstrate that inhibiting the degradation of heparan sulfate in the tumor microenvironment augments the susceptibility of TNBC cell lines to chemotherapy by increasing extracellular ATP concentrations. This strategy could potentially be applied to induce more enhanced and enduring responses in TNBC patients.

Heparanase 2 (Hpa2)- a new player essential for pancreatic acinar cell differentiation

Heparanase 2 (Hpa2, HPSE2) is a close homolog of heparanase. Hpa2, however, lacks intrinsic heparan sulfate (HS)-degrading activity, the hallmark of heparanase enzymatic activity. Mutations of HPSE2 were identified in patients diagnosed with urofacial syndrome (UFS), a rare genetic disorder that exhibits abnormal facial expression and bladder voiding dysfunction, leading to renal damage and eventually renal failure. In order to reveal the role of HPSE2 in tissue homeostasis, we established a conditional Hpa2-KO mouse. Interestingly, the lack of Hpa2 was associated with a marked decrease in the expression of key pancreatic transcription factors such as PTF1, GATA6, and Mist1. This was associated with a two-fold decrease in pancreas weight, increased pancreatic inflammation, and profound morphological alterations of the pancreas. These include massive accumulation of fat cells, possibly a result of acinar-to-adipocyte transdifferentiation (AAT), as well as acinar-to-ductal metaplasia (ADM), both considered to be pro-tumorigenic. Furthermore, exposing Hpa2-KO but not wild-type mice to a carcinogen (AOM) and pancreatic inflammation (cerulein) resulted in the formation of pancreatic intraepithelial neoplasia (PanIN), lesions that are considered to be precursors of invasive ductal adenocarcinoma of the pancreas (PDAC). These results strongly support the notion that Hpa2 functions as a tumor suppressor. Moreover, Hpa2 is shown here for the first time to play a critical role in the exocrine aspect of the pancreas.

Role of a Novel Heparanase Inhibitor on the Balance between Apoptosis and Autophagy in U87 Human Glioblastoma Cells

BACKGROUND

Heparanase (HPSE) is an endo-β-glucuronidase that cleaves heparan sulfate side chains, leading to the disassembly of the extracellular matrix, facilitating cell invasion and metastasis dissemination. In this research, we investigated the role of a new HPSE inhibitor, RDS 3337, in the regulation of the autophagic process and the balance between apoptosis and autophagy in U87 glioblastoma cells.

METHODS

After treatment with RDS 3337, cell lysates were analyzed for autophagy and apoptosis-related proteins by Western blot.

RESULTS

We observed, firstly, that LC3II expression increased in U87 cells incubated with RDS 3337, together with a significant increase of p62/SQSTM1 levels, indicating that RDS 3337 could act through the inhibition of autophagic-lysosomal flux of LC3-II, thereby leading to accumulation of lipidated LC3-II form. Conversely, the suppression of autophagic flux could activate apoptosis mechanisms, as revealed by the activation of caspase 3, the increased level of cleaved Parp1, and DNA fragmentation.

CONCLUSIONS

These findings support the notion that HPSE promotes autophagy, providing evidence that RDS 3337 blocks autophagic flux. It indicates a role for HPSE inhibitors in the balance between apoptosis and autophagy in U87 human glioblastoma cells, suggesting a potential role for this new class of compounds in the control of tumor growth progression.

Heparanase-A single protein with multiple enzymatic and nonenzymatic functions

Heparanase (Hpa1) is expressed by tumor cells and cells of the tumor microenvironment and functions extracellularly to remodel the extracellular matrix (ECM) and regulate the bioavailability of ECM-bound factors, augmenting, among other effects, gene transcription, autophagy, exosome formation, and heparan sulfate (HS) turnover. Much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis, and chemoresistance. The enzyme appears to fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, autophagy, HS turnover, and gene transcription. It activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and nonenzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive tumor growth, dissemination, and drug resistance as well as inflammatory responses. The emerging premise is that heparanase expressed by tumor cells, immune cells, endothelial cells, and other cells of the tumor microenvironment is a key regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a valid target for therapy. So far, however, antiheparanase-based therapy has not been implemented in the clinic. Unlike heparanase, heparanase-2 (Hpa2), a close homolog of heparanase (Hpa1), does not undergo proteolytic processing and hence lacks intrinsic HS-degrading activity, the hallmark of heparanase. Hpa2 retains the capacity to bind heparin/HS and exhibits an even higher affinity towards HS than heparanase, thus competing for HS binding and inhibiting heparanase enzymatic activity. It appears that Hpa2 functions as a natural inhibitor of Hpa1 regulates the expression of selected genes that maintain tissue hemostasis and normal function, and plays a protective role against cancer and inflammation, together emphasizing the significance of maintaining a proper balance between Hpa1 and Hpa2.

Role of heparanase in ARDS through autophagy and exosome pathway (review)

Acute respiratory distress syndrome (ARDS) is the most common respiratory disease in ICU. Although there are many treatment and support methods, the mortality rate is still high. The main pathological feature of ARDS is the damage of pulmonary microvascular endothelium and alveolar epithelium caused by inflammatory reaction, which may lead to coagulation system disorder and pulmonary fibrosis. Heparanase (HPA) plays an significant role in inflammation, coagulation, fibrosis. It is reported that HPA degrades a large amount of HS in ARDS, leading to the damage of endothelial glycocalyx and inflammatory factors are released in large quantities. HPA can aggrandize the release of exosomes through syndecan-syntenin-Alix pathway, leading to a series of pathological reactions; at the same time, HPA can cause abnormal expression of autophagy. Therefore, we speculate that HPA promotes the occurrence and development of ARDS through exosomes and autophagy, which leads to a large amount of release of inflammatory factors, coagulation disorder and pulmonary fibrosis. This article mainly describes the mechanism of HPA on ARDS.

Extracellular vesicles released during hypoxia transport heparanase and enhance macrophage migration, endothelial tube formation and cancer cell stemness

Heparanase is upregulated during the progression of most cancers and via its enzyme activity promotes extracellular matrix degradation, angiogenesis and cell migration. Heparanase expression is often associated with enhanced tumor aggressiveness and chemoresistance. We previously demonstrated that increased heparanase expression in tumor cells enhances secretion and alters the composition of tumor-released exosomes. In the present study, we discovered that extracellular vesicles (EVs) secreted by human multiple myeloma cells growing in hypoxic conditions exhibited elevated levels of heparanase cargo compared to EVs from cells growing in normoxic conditions. When macrophages (RAW 264.7 monocyte/macrophage-like cells) were exposed to EVs released by tumor cells growing in either hypoxic or normoxic conditions, macrophage migration and invasion was elevated by EVs from hypoxic conditions. The elevated invasion of macrophages was blocked by a monoclonal antibody that inhibits heparanase enzyme activity. Moreover, the heparanase-bearing EVs from hypoxic cells greatly enhanced endothelial cell tube formation consistent with the known role of heparanase in promoting angiogenesis. EVs from hypoxic tumor cells when compared with EVs from normoxic cells also enhanced cancer stemness properties of both CAG and RPMI 8226 human myeloma cells. Together these data indicate that under hypoxic conditions, tumor cells secrete EVs having an elevated level of heparanase as cargo. These EVs can act on both tumor and non-tumor cells, enhancing tumor progression and tumor cell stemness that likely supports chemoresistance and relapse of tumor.

Flow-Induced Secretion of Endothelial Heparanase Regulates Cardiac Lipoprotein Lipase and Changes Following Diabetes

Background Lipoprotein lipase (LPL)-derived fatty acid is a major source of energy for cardiac contraction. Synthesized in cardiomyocytes, LPL requires translocation to the vascular lumen for hydrolysis of lipoprotein triglyceride, an action mediated by endothelial cell (EC) release of heparanase. We determined whether flow-mediated biophysical forces can cause ECs to secrete heparanase and thus regulate cardiac metabolism. Methods and Results Isolated hearts were retrogradely perfused. Confluent rat aortic ECs were exposed to laminar flow using an orbital shaker. Cathepsin L activity was determined using gelatin-zymography. Diabetes was induced in rats with streptozotocin. Despite the abundance of enzymatically active heparanase in the heart, it was the enzymatically inactive, latent heparanase that was exceptionally responsive to flow-induced release. EC exposed to orbital rotation exhibited a similar pattern of heparanase secretion, an effect that was reproduced by activation of the mechanosensor, Piezo1. The laminar flow-mediated release of heparanase from EC required activation of both the purinergic receptor and protein kinase D, a kinase that assists in vesicular transport of proteins. Heparanase influenced cardiac metabolism by increasing cardiomyocyte LPL displacement along with subsequent replenishment. The flow-induced heparanase secretion was augmented following diabetes and could explain the increased heparin-releasable pool of LPL at the coronary lumen in these diabetic hearts. Conclusions ECs sense fluid shear-stress and communicate this information to subjacent cardiomyocytes with the help of heparanase. This flow-induced mechanosensing and its dynamic control of cardiac metabolism to generate ATP, using LPL-derived fatty acid, is exquisitely adapted to respond to disease conditions, like diabetes.

Importance of Heparan Sulfate Proteoglycans in Pancreatic Islets and β-Cells

β-cells in the islets of Langerhans of the pancreas secrete insulin in response to the glucose concentration in the blood. When these pancreatic β-cells are damaged, diabetes develops through glucose intolerance caused by insufficient insulin secretion. High molecular weight polysaccharides, such as heparin and heparan sulfate (HS) proteoglycans, and HS-degrading enzymes, such as heparinase, participate in the protection, maintenance, and enhancement of the functions of pancreatic islets and β-cells, and the demand for studies on glycobiology within the field of diabetes research has increased. This review introduces the roles of complex glycoconjugates containing high molecular weight polysaccharides and their degrading enzymes in pancreatic islets and β-cells, including those obtained in studies conducted by us earlier. In addition, from the perspective of glycobiology, this study proposes the possibility of application to diabetes medicine.

Glycosyltransferases EXTL2 and EXTL3 cellular balance dictates Heparan Sulfate biosynthesis and shapes gastric cancer cell motility and invasion

Heparan Sulfate Proteoglycans (HSPGs) are abundant glycoconjugates in cells' glycocalyx and Extracellular Matrix (ECM). By acting as scaffolds for protein-protein interactions, HSPGs modulate extracellular ligand gradients, cell signaling networks, and cell-ECM crosstalk. Aberrant expression of HSPGs and enzymes involved in HSPG biosynthesis and processing has been reported in tumors, with impact in cancer cell behavior and tumor microenvironment properties. However, the roles of specific glycosyltransferases in the deregulated biosynthesis of HSPGs are not fully understood. In this study, we established glycoengineered gastric cancer cell models lacking either Exostosin Like glycosyltransferase 2 (EXTL2) or EXTL3, and revealed their regulatory roles in both Heparan Sulfate (HS) and Chondroitin Sulfate (CS) biosynthesis and structural features. We showed that EXTL3 is key for initiating the synthesis of HS chains in detriment of CS biosynthesis, intervening in the fine-tuned balance of the HS/CS ratio in cells, while EXTL2 functions as a negative regulator of HS biosynthesis, with impact over the glycoproteome of gastric cancer cells. We demonstrated that knock-out of EXTL2 enhanced HS levels along with concomitant upregulation of Syndecan-4, which is a major cell-surface carrier of HS. This aberrant HS expression profile promoted a more aggressive phenotype, characterized by higher cellular motility and invasion, and impaired activation of Ephrin type-A 4 cell surface receptor tyrosine kinase. Our findings uncover the biosynthetic roles of EXTL2 and EXTL3 in the regulation of cancer cell GAGosylation and proteoglycans expression, and unravel the functional consequences of aberrant HS/CS balance in cellular malignant features.

Mechanism-based heparanase inhibitors reduce cancer metastasis in vivo

Cancer growth is accompanied by changes to the extracellular environment of tumors, which aids the proliferation and spread of cancer cells. Cancer-associated extracellular matrix changes include excessive degradation of heparan sulfate carbohydrates, promoting metastatic spread by multiple mechanisms. Heparanase is the main human enzyme responsible for extracellular heparan sulfate breakdown and strongly drives metastasis when overexpressed. Few effective heparanase inhibitors are known, and the most effective molecules to date possess nondrug-like structures with multiple off-target effects. We have carried out structure-guided development of heparanase inhibitors, which covalently bind to the enzyme active site to cause irreversible inhibition. These inhibitors are heparanase specific and reduce metastasis in animal models with comparable efficacy to current “best-in-class” compounds.

Heparan sulfate proteoglycans (HSPGs) mediate essential interactions throughout the extracellular matrix (ECM), providing signals that regulate cellular growth and development. Altered HSPG composition during tumorigenesis strongly aids cancer progression. Heparanase (HPSE) is the principal enzyme responsible for extracellular heparan sulfate catabolism and is markedly up-regulated in aggressive cancers. HPSE overactivity degrades HSPGs within the ECM, facilitating metastatic dissemination and releasing mitogens that drive cellular proliferation. Reducing extracellular HPSE activity reduces cancer growth, but few effective inhibitors are known, and none are clinically approved. Inspired by the natural glycosidase inhibitor cyclophellitol, we developed nanomolar mechanism-based, irreversible HPSE inhibitors that are effective within physiological environments. Application of cyclophellitol-derived HPSE inhibitors reduces cancer aggression in cellulo and significantly ameliorates murine metastasis. Mechanism-based irreversible HPSE inhibition is an unexplored anticancer strategy. We demonstrate the feasibility of such compounds to control pathological HPSE-driven malignancies.

A Marine λ-Oligocarrageenan Inhibits Migratory and Invasive Ability of MDA-MB-231 Human Breast Cancer Cells through Actions on Heparanase Metabolism and MMP-14/MMP-2 Axis

Sugar-based molecules such as heparins or natural heparan sulfate polysaccharides have been developed and widely studied for controlling heparanase (HPSE) enzymatic activity, a key player in extracellular matrix remodelling during cancer pathogenesis. However, non-enzymatic functions of HPSE have also been described in tumour mechanisms. Given their versatile properties, we hypothesized that sugar-based inhibitors may interfere with enzymatic but also non-enzymatic HPSE activities. In this work, we assessed the effects of an original marine λ-carrageenan derived oligosaccharide (λ-CO) we previously described, along with those of its native counterpart and heparins, on cell viability, proliferation, migration, and invasion of MDA-MB-231 breast cancer cells but also of sh-MDA-MB-231 cells, in which the expression of HPSE was selectively downregulated. We observed no cytotoxic and no anti-proliferative effects of our compounds but surprisingly λ-CO was the most efficient to reduce cell migration and invasion compared with heparins, and in a HPSE-dependent manner. We provided evidence that λ-CO tightly controlled a HPSE/MMP-14/MMP-2 axis, leading to reduced MMP-2 activity. Altogether, this study highlights λ-CO as a potent HPSE “modulator” capable of reducing not only the enzymatic activity of HPSE but also the functions controlled by the HPSE levels.

Lipoprotein Lipase and Its Delivery of Fatty Acids to the Heart

Ninety percent of plasma fatty acids (FAs) are contained within lipoprotein-triglyceride, and lipoprotein lipase (LPL) is robustly expressed in the heart. Hence, LPL-mediated lipolysis of lipoproteins is suggested to be a key source of FAs for cardiac use. Lipoprotein clearance by LPL occurs at the apical surface of the endothelial cell lining of the coronary lumen. In the heart, the majority of LPL is produced in cardiomyocytes and subsequently is translocated to the apical luminal surface. Here, vascular LPL hydrolyzes lipoprotein-triglyceride to provide the heart with FAs for ATP generation. This article presents an overview of cardiac LPL, explains how the enzyme works, describes key molecules that regulate its activity and outlines how changes in LPL are brought about by physiological and pathological states such as fasting and diabetes, respectively.

Heparanase expression and activity are increased in platelets during clinical sepsis

BACKGROUND

Heparanase (HPSE) is the only known mammalian enzyme that can degrade heparan sulfate. Heparan sulfate proteoglycans are essential components of the glycocalyx, and maintain physiological barriers between the blood and endothelial cells. HPSE increases during sepsis, which contributes to injurious glyocalyx degradation, loss of endothelial barrier function, and mortality.

OBJECTIVES

As platelets are one of the most abundant cellular sources of HPSE, we sought to determine whether HPSE expression and activity increases in human platelets during clinical sepsis. We also examined associations between platelet HPSE expression and clinical outcomes.

PATIENTS/METHODS

Expression and activity of HPSE was determined in platelets isolated from septic patients (n = 59) and, for comparison, sex-matched healthy donors (n = 46) using complementary transcriptomic, proteomic, and functional enzymatic assays. Septic patients were followed for the primary outcome of mortality, and clinical data were captured prospectively for septic patients.

RESULTS

The mRNA expression of HPSE was significantly increased in platelets isolated from septic patients. Ribosomal footprint profiling, followed by [S35] methionine labeling assays, demonstrated that HPSE mRNA translation and HPSE protein synthesis were significantly upregulated in platelets during sepsis. While both the pro- and active forms of HPSE protein increased in platelets during sepsis, only the active form of HPSE protein significantly correlated with sepsis-associated mortality. Consistent with transcriptomic and proteomic upregulation, HPSE enzymatic activity was also increased in platelets during sepsis.

CONCLUSIONS

During clinical sepsis HPSE, translation, and enzymatic activity are increased in platelets. Increased expression of the active form of HPSE protein is associated with sepsis-associated mortality.

Antiviral strategies should focus on stimulating the biosynthesis of heparan sulfates, not their inhibition

Antiviral strategies for viruses that utilize proteoglycan core proteins (syndecans and glypicans) as receptors should focus on heparan sulfate (HS) biosynthesis rather than on inhibition of these sugar chains. Here, we show that heparin and certain xylosides, which exhibit in vitro viral entry inhibitory properties against HSV-1, HSV-2, HPV-16, HPV-31, HVB, HVC, HIV-1, HTLV-1, SARS-CoV-2, HCMV, DENV-1, and DENV-2, stimulated HS biosynthesis at the cell surface 2- to 3-fold for heparin and up to 10-fold for such xylosides. This is consistent with the hypothesis from a previous study that for core protein attachment, viruses are glycosylated at HS attachment sites (i.e., serine residues intended to receive the D-xylose molecule for initiating HS chains). Heparanase overexpression, endocytic entry, and syndecan shedding enhancement, all of which are observed during viral infection, lead to glycocalyx deregulation and appear to be direct consequences of this hypothesis. In addition to the appearance of type 2 diabetes and the degradation of HS observed during viral infection, we linked this hypothesis to that proposed in a previous publication.

Heparan Sulfate Proteoglycans in Diabetes

Diabetes is a complex disorder responsible for the mortality and morbidity of millions of individuals worldwide. Although many approaches have been used to understand and treat diabetes, the role of proteoglycans, in particular heparan sulfate proteoglycans (HSPGs), has only recently received attention. The HSPGs are heterogeneous, highly negatively charged, and are found in all cells primarily attached to the plasma membrane or present in the extracellular matrix (ECM). HSPGs are involved in development, cell migration, signal transduction, hemostasis, inflammation, and antiviral activity, and regulate cytokines, chemokines, growth factors, and enzymes. Hyperglycemia, accompanying diabetes, increases reactive oxygen species and upregulates the enzyme heparanase that degrades HSPGs or affects the synthesis of the HSPGs altering their structure. The modified HSPGs in the endothelium and ECM in the blood vessel wall contribute to the nephropathy, cardiovascular disease, and retinopathy seen in diabetes. Besides the blood vessel, other cells and tissues in the heart, kidney, and eye are affected by diabetes. Although not well understood, the adipose tissue, intestine, and brain also reveal HSPG changes associated with diabetes. Further, HSPGs are significantly involved in protecting the β cells of the pancreas from autoimmune destruction and could be a focus of prevention of type I diabetes. In some circumstances, HSPGs may contribute to the pathology of the disease. Understanding the role of HSPGs and how they are modified by diabetes may lead to new treatments as well as preventative measures to reduce the morbidity and mortality associated with this complex condition.

Biology of the Heparanase-Heparan Sulfate Axis and Its Role in Disease Pathogenesis

Cell surface proteoglycans are important constituents of the glycocalyx and participate in cell-cell and cell-extracellular matrix (ECM) interactions, enzyme activation and inhibition, and multiple signaling routes, thereby regulating cell proliferation, survival, adhesion, migration, and differentiation. Heparanase, the sole mammalian heparan sulfate degrading endoglycosidase, acts as an "activator" of HS proteoglycans, thus regulating tissue hemostasis. Heparanase is a multifaceted enzyme that together with heparan sulfate, primarily syndecan-1, drives signal transduction, immune cell activation, exosome formation, autophagy, and gene transcription via enzymatic and nonenzymatic activities. An important feature is the ability of heparanase to stimulate syndecan-1 shedding, thereby impacting cell behavior both locally and distally from its cell of origin. Heparanase releases a myriad of HS-bound growth factors, cytokines, and chemokines that are sequestered by heparan sulfate in the glycocalyx and ECM. Collectively, the heparan sulfate-heparanase axis plays pivotal roles in creating a permissive environment for cell proliferation, differentiation, and function, often resulting in the pathogenesis of diseases such as cancer, inflammation, endotheliitis, kidney dysfunction, tissue fibrosis, and viral infection.

Ischemic stroke disrupts the endothelial glycocalyx through activation of proHPSE via acrolein exposure

Infiltration of peripheral immune cells after blood-brain barrier dysfunction causes severe inflammation after a stroke. Although the endothelial glycocalyx, a network of membrane-bound glycoproteins and proteoglycans that covers the lumen of endothelial cells, functions as a barrier to circulating cells, the relationship between stroke severity and glycocalyx dysfunction remains unclear. In this study, glycosaminoglycans, a component of the endothelial glycocalyx, were studied in the context of ischemic stroke using a photochemically induced thrombosis mouse model. Decreased levels of heparan sulfate and chondroitin sulfate and increased activity of hyaluronidase 1 and heparanase (HPSE) were observed in ischemic brain tissues. HPSE expression in cerebral vessels increased after stroke onset and infarct volume greatly decreased after co-administration of N-acetylcysteine + glycosaminoglycan oligosaccharides as compared with N-acetylcysteine administration alone. These results suggest that the endothelial glycocalyx was injured after the onset of stroke. Interestingly, scission activity of proHPSE produced by immortalized endothelial cells and HEK293 cells transfected with hHPSE1 cDNA were activated by acrolein (ACR) exposure. We identified the ACR-modified amino acid residues of proHPSE using nano LC-MS/MS, suggesting that ACR modification of Lys139 (6-kDa linker), Lys107, and Lys161, located in the immediate vicinity of the 6-kDa linker, at least in part is attributed to the activation of proHPSE. Because proHPSE, but not HPSE, localizes outside cells by binding with heparan sulfate proteoglycans, ACR-modified proHPSE represents a promising target to protect the endothelial glycocalyx.

Nuclear Heparanase Regulates Chromatin Remodeling, Gene Expression and PTEN Tumor Suppressor Function

Heparanase (HPSE) is an endoglycosidase that cleaves heparan sulfate and has been shown in various cancers to promote metastasis, angiogenesis, osteolysis, and chemoresistance. Although heparanase is thought to act predominantly extracellularly or within the cytoplasm, it is also present in the nucleus, where it may function in regulating gene transcription. Using myeloma cell lines, we report here that heparanase enhances chromatin accessibility and confirm a previous report that it also upregulates the acetylation of histones. Employing the Multiple Myeloma Research Foundation CoMMpass database, we demonstrate that patients expressing high levels of heparanase display elevated expression of proteins involved in chromatin remodeling and several oncogenic factors compared to patients expressing low levels of heparanase. These signatures were consistent with the known function of heparanase in driving tumor progression. Chromatin opening and downstream target genes were abrogated by inhibition of heparanase. Enhanced levels of heparanase in myeloma cells led to a dramatic increase in phosphorylation of PTEN, an event known to stabilize PTEN, leading to its inactivity and loss of tumor suppressor function. Collectively, this study demonstrates that heparanase promotes chromatin opening and transcriptional activity, some of which likely is through its impact on diminishing PTEN tumor suppressor activity.

Hydrofluoric acid and nitric acid cotreatment for biofunctionalization of polyetheretherketone in M2 macrophage polarization and osteogenesis

Due to its excellent mechanical and low-friction properties, polyetheretherketone (PEEK) has been widely investigated for use in orthopedic applications over the past decade. However, the bioinertness and poor osteogenic properties of PEEK have hampered its clinical application. In this study, the surface of PEEK was modified by co-treatment with hydrofluoric acid and nitric acid (AFN). The microstructures of the modified PEEK surfaces were investigated using scanning electron microscopy. The water contact angles of the surfaces were also measured. To evaluate their cytocompatibility, PEEK samples were used as substrates to culture rat bone mesenchymal stem cells, and cell adhesion, viability, and expression of specific marker genes were measured. Treatment of PEEK with AFN (PEEK-AFN) was found to enable better osteoblast adhesion, spreading, and proliferation; the activity of alkaline phosphatase (an early osteogenic differentiation marker) was also found to be enhanced post-treatment. Furthermore, PEEK-AFN was able to modulate macrophage polarization and down regulated the expression of proinflammatory factors via inhibiting the NF-κB pathway. Thus, treatment of PEEK with AFN could promote M2 polarization of the macrophages and stimulate the differentiation of osteoblasts. These results provide valuable information that could facilitate the use of PEEK-based composites as bone implant materials.

Heparanase: Historical Aspects and Future Perspectives

Heparanase is an endo-β-glucuronidase that cleaves at a limited number of internal sites the glycosaminoglycan heparan sulfate (HS). Heparanase enzymatic activity was first reported in 1975 and by 1983 evidence was beginning to emerge that the enzyme was a facilitator of tumor metastasis by cleaving HS chains present in blood vessel basement membranes and, thereby, aiding the passage of tumor cells through blood vessel walls. Due to a range of technical difficulties, it took another 16 years before heparanase was cloned and characterized in 1999 and a further 14 years before the crystal structure of the enzyme was solved. Despite these substantial deficiencies, there was steady progress in our understanding of heparanase long before the enzyme was fully characterized. For example, it was found as early as 1984 that activated T cells upregulate heparanase expression, like metastatic tumor cells, and the enzyme aids the entry of T cells and other leukocytes into inflammatory sites. Furthermore, it was discovered in 1989 that heparanase releases pre-existing growth factors and cytokines associated with HS in the extracellular matrix (ECM), the liberated growth factors/cytokines enhancing angiogenesis and wound healing. There were also the first hints that heparanase may have functions other than enzymatic activity, in 1995 it being reported that under certain conditions the enzyme could act as a cell adhesion molecule. Also, in the same year PI-88 (Muparfostat), the first heparanase inhibitor to reach and successfully complete a Phase III clinical trial was patented.Nevertheless, the cloning of heparanase (also known as heparanase-1) in 1999 gave the field an enormous boost and some surprises. The biggest surprise was that there is only one heparanase encoding gene in the mammalian genome, despite earlier research, based on substrate specificity, suggesting that there are at least three different heparanases. This surprising conclusion has remained unchanged for the last 20 years. It also became evident that heparanase is a family 79 glycoside hydrolase that is initially produced as a pro-enzyme that needs to be processed by proteases to form an enzymatically active heterodimer. A related molecule, heparanase-2, was also discovered that is enzymatically inactive but, remarkably, recently has been shown to inhibit heparanase-1 activity as well as acting as a tumor suppressor that counteracts many of the pro-tumor properties of heparanase-1.The early claim that heparanase plays a key role in tumor metastasis, angiogenesis and inflammation has been confirmed by many studies over the last 20 years. In fact, heparanase expression is enhanced in all major cancer types, namely carcinomas, sarcomas, and hematological malignancies, and correlates with increased metastasis and poor prognosis. Also, there is mounting evidence that heparanase plays a central role in the induction of inflammation-associated cancers. The enzymatic activity of heparanase has also emerged in unexpected situations, such as in the spread of HS-binding viruses and in Type-1 diabetes where the destruction of intracellular HS in pancreatic insulin-producing beta cells precipitates diabetes. But the most extraordinary recent discoveries have been with the realization that heparanase can exert a range of biological activities that are independent of its enzymatic function, most notably activation of several signaling pathways and being a transcription factor that controls methylation of histone tails. Collectively, these data indicate that heparanase is a truly multifunctional protein that has the additional property of cleaving HS chains and releasing from ECM and cell surfaces hundreds of HS-binding proteins with a plethora of functional consequences. Clearly, there are many unique features of this intriguing molecule that still remain to be explored and are highlighted in this Chapter.

Heparanase: Cloning, Function and Regulation

In 2019, we mark the 20th anniversary of the cloning of the human heparanase gene. Heparanase remains the only known enzyme to cleave heparan sulfate, which is an abundant component of the extracellular matrix. Thus, elucidating the mechanisms underlying heparanase expression and activity is critical to understanding its role in healthy and pathological settings. This chapter provides a historical account of the race to clone the human heparanase gene, describes the intracellular and extracellular function of the enzyme, and explores the various mechanisms regulating heparanase expression and activity at the gene, transcript, and protein level.

The Good and Bad Sides of Heparanase-1 and Heparanase-2

In this chapter, we will emphasize the importance of heparan sulfate proteoglycans (HSPG) in controlling various physiological and pathological molecular mechanisms and discuss how the heparanase enzyme can modulate the effects triggered by HSPG. Additionally, we will also navigate about the existing knowledge of the possible role of heparanase-2 in biological events. Heparan sulfate is widely distributed and evolutionarily conserved, evidencing its vital importance in cell development and functions such as cell proliferation, migration, adhesion, differentiation, and angiogenesis. During remodeling of the extracellular matrix, the breakdown of heparan sulfate by heparanase results in the release of molecules containing anchored glycosaminoglycan chains of great interest in heparanase-mediated cell signaling pathways in various physiological states, tumor development, inflammation, and other diseases. Taken together, it appears that heparanase plays a key role in the maintenance of the pathology of cancer and inflammatory diseases and is a potential target for anti-cancer therapies. Therefore, heparanase inhibitors are currently being examined in clinical trials as novel cancer therapeutics. Heparanase-2 has no enzymatic activity, displays higher affinity for heparan sulfate and the coding region alignment shows 40% identity with the heparanase gene. Heparanase-2 plays an important role in embryogenic development however its mode of action and biological function remain to be elucidated. Heparanase-2 functions as an inhibitor of the heparanase-1 enzyme and also inhibits neovascularization mediated by VEGF. The HPSE2 gene is repressed by the Polycomb complex, together suggesting a role as a tumor suppressor.

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.

Involvement of Heparanase in Endothelial Cell-Cardiomyocyte Crosstalk

Traditionally, the management of diabetes has focused mainly on controlling high blood glucose levels. Unfortunately, despite valiant efforts to normalize this blood glucose, poor medication management predisposes these patients to heart failure. Following diabetes, how the heart utilizes different sources of fuel for energy is key to the development of heart failure. The diabetic heart switches from using both glucose and fats, to predominately using fats as an energy resource for maintaining its activities. This transformation to using fats as an exclusive source of energy is helpful in the initial stages of the disease and is tightly controlled. However, over the progression of diabetes, there is a loss of this controlled supply and use of fats, which ultimately has terrible consequences since the uncontrolled use of fats produces toxic by-products which weaken heart function and cause heart disease. Heparanase is a key player that directs how much fats are provided to the heart and does so in association with several partners like LPL and VEGFs. Together, they regulate the amount of fats supplied, and their subsequent breakdown to provide energy. Following diabetes, there is a disruption in this network resulting in fat oversupply and cell death. Understanding how the heparanase-LPL-VEGFs "ensemble" cooperates, and its dysfunction in the diabetic heart would be useful in restoring metabolic equilibrium and limiting diabetes-related cardiac damage.

The HPA/SDC1 axis promotes invasion and metastasis of pancreatic cancer cells by activating EMT via FGF2 upregulation

Pancreatic cancer is characterized by the absence of early specific clinical symptoms, accompanied with rapid metastasis and invasion. It is one of the most prevalent types of cancer and more importantly, one of the most common types of malignant cancer with the highest mortality rate of all cancer types. The heparanase (HPA)/syndecan-1 (SDC1) axis has been reported to promote tumor growth, invasion, metastasis and angiogenesis in a variety of cancer types; however, studies into the role and mechanism of the HPA/SDC1 axis in pancreatic cancer are limited. The present study aimed to investigate the biological function and clinical significance of the HPA/SDC1 axis in pancreatic cancer. The results demonstrated that HPA is elevated in pancreatic cancer tissues and cell lines, and that its high expression was associated with poor prognosis. HPA was revealed to mediate an increase in fibroblast growth factor 2 (FGF2) expression by upregulating the expression of SDC1. Conversely, silencing HPA mediated the suppression of FGF2 expression. Furthermore, upregulated FGF2 was observed to increase the expression of downstream Palladin proteins by activating the PI3K/Akt signaling pathway and also lead to the activation of epithelial-mesenchymal transition (EMT). Subsequently, EMT was found to promote the migration and invasion of pancreatic cancer cells. In summary, the HPA/SDC1 axis was revealed to serve an important role in the regulation of FGF2, and was found to promote the invasion and metastasis of pancreatic cancer cells. These findings indicated that the HPA/SDC1 axis may be used as an effective therapeutic target for pancreatic cancer.

Heparanase and Type 1 Diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing beta cells in pancreatic islets. The degradation of the glycosaminoglycan heparan sulfate (HS) by the endo-β-D-glycosidase heparanase plays a critical role in multiple stages of the disease process. Heparanase aids (i) migration of inflammatory leukocytes from the vasculature to the islets, (ii) intra-islet invasion by insulitis leukocytes, and (iii) selective destruction of beta cells. These disease stages are marked by the solubilization of HS in the subendothelial basement membrane (BM), HS breakdown in the peri-islet BM, and the degradation of HS inside beta cells, respectively. Significantly, healthy islet beta cells are enriched in highly sulfated HS which is essential for their viability, protection from damage by reactive oxygen species (ROS), beta cell function and differentiation. Consequently, mouse and human beta cells but not glucagon-producing alpha cells (which contain less-sulfated HS) are exquisitely vulnerable to heparanase-mediated damage. In vitro, the death of HS-depleted mouse and human beta cells can be prevented by HS replacement using highly sulfated HS mimetics or analogues. T1D progression in NOD mice and recent-onset T1D in humans correlate with increased expression of heparanase by circulating leukocytes of myeloid origin and heparanase-expressing insulitis leukocytes. Treatment of NOD mice with the heparanase inhibitor and HS replacer, PI-88, significantly reduced T1D incidence by 50%, impaired the development of insulitis and preserved beta cell HS. These outcomes identified heparanase as a novel destructive tool in T1D, distinct from the conventional cytotoxic and apoptosis-inducing mechanisms of autoreactive T cells. In contrast to exogenous catalytically active heparanase, endogenous heparanase may function in HS homeostasis, gene expression and insulin secretion in normal beta cells and immune gene expression in leukocytes. In established diabetes, the interplay between hyperglycemia, local inflammatory cells (e.g. macrophages) and heparanase contributes to secondary micro- and macro-vascular disease. We have identified dual activity heparanase inhibitors/HS replacers as a novel class of therapeutic for preventing T1D progression and potentially for mitigating secondary vascular disease that develops with long-term T1D.

Heparanase Involvement in Exosome Formation

Exosomes are secreted vesicles involved in signaling processes. The biogenesis of a class of these extracellular vesicles depends on syntenin, and on the interaction of this cytosolic protein with syndecans. Heparanase, largely an endosomal enzyme, acts as a regulator of the syndecan-syntenin-exosome biogenesis pathway. The upregulation of syntenin and heparanase in cancers may support the suspected roles of exosomes in tumor biology.

Forty Years of Basic and Translational Heparanase Research

This review summarizes key developments in the heparanase field obtained 20 years prior to cloning of the HPSE gene and nearly 20 years after its cloning. Of the numerous publications and review articles focusing on heparanase, we have selected those that best reflect the progression in the field as well as those we regard important accomplishments with preference to studies performed by scientists and groups that contributed to this book. Apart from a general 'introduction' and 'concluding remarks', the abstracts of these studies are presented essentially as published along the years. We apologize for not being objective and not being able to include some of the most relevant abstracts and references, due to space limitation. Heparanase research can be divided into two eras. The first, initiated around 1975, dealt with identifying the enzyme, establishing the relevant assay systems and investigating its biological activities and significance in cancer and other pathologies. Studies performed during the first area are briefly introduced in a layman style followed by the relevant abstracts presented chronologically, essentially as appears in PubMed. The second era started in 1999 when the heparanase gene was independently cloned by 4 research groups [1-4]. As expected, cloning of the heparanase gene boosted heparanase research by virtue of the readily available recombinant enzyme, molecular probes, and anti-heparanase antibodies. Studies performed during the second area are briefly introduced followed by selected abstracts of key findings, arranged according to specific topics.

An Overview of the Structure, Mechanism and Specificity of Human Heparanase

The retaining endo-β-D-glucuronidase Heparanase (HPSE) is the primary mammalian enzyme responsible for breakdown of the glycosaminoglycan heparan sulfate (HS). HPSE activity is essential for regulation and turnover of HS in the extracellular matrix, and its activity affects diverse processes such as inflammation, angiogenesis and cell migration. Aberrant heparanase activity is strongly linked to cancer metastasis, due to structural breakdown of extracellular HS networks and concomitant release of sequestered HS-binding growth factors. A full appreciation of HPSE activity in health and disease requires a structural understanding of the enzyme, and how it engages with its HS substrates. This chapter summarizes key findings from the recent crystal structures of human HPSE and its proenzyme. We present details regarding the 3-dimensional protein structure of HPSE and the molecular basis for its interaction with HS substrates of varying sulfation states. We also examine HPSE in a wider context against related β-D-glucuronidases from other species, highlighting the structural features that control exo/endo - glycosidase selectivity in this family of enzymes.

Heparanase: A Challenging Cancer Drug Target

Heparanase has been viewed as a promising anti-cancer drug target for almost two decades, but no anti-heparanase therapy has yet reached the clinic. This endoglycosidase is highly expressed in a variety of malignancies, and its high expression is associated with greater tumor size, more metastases, and a poor prognosis. It was first described as an enzyme cleaving heparan sulfate chains of proteoglycans located in extracellular matrices and on cell surfaces, but this is not its only function. It is a multi-functional protein with activities that are enzymatic and non-enzymatic and which take place both outside of the cell and intracellularly. Knowledge of the crystal structure of heparanase has assisted the interpretation of earlier structure-function studies as well as in the design of potential anti-heparanase agents. This review re-examines the various functions of heparanase in light of the structural data. The functions of the heparanase variant, T5, and structure and functions of heparanase-2 are also examined as these heparanase related, but non-enzymatic, proteins are likely to influence the in vivo efficacy of anti-heparanase drugs. The anti-heparanase drugs currently under development predominately focus on inhibiting the enzymatic activity of heparanase, which, in the absence of inhibitors with high clinical efficacy, prompts a discussion of whether this is the best approach. The diversity of outcomes attributed to heparanase and the difficulties of unequivocally determining which of these are due to its enzymatic activity is also discussed and leads us to the conclusion that heparanase is a valid, but challenging drug target for cancer.

Targeting Heparanase in Cancer: Inhibition by Synthetic, Chemically Modified, and Natural Compounds

Heparanase is an endoglycosidase involved in remodeling the extracellular matrix and thereby in regulating multiple cellular processes and biological activities. It cleaves heparan sulfate (HS) side chains of HS proteoglycans into smaller fragments and hence regulates tissue morphogenesis, differentiation, and homeostasis. Heparanase is overexpressed in various carcinomas, sarcomas, and hematological malignancies, and its upregulation correlates with increased tumor size, tumor angiogenesis, enhanced metastasis, and poor prognosis. In contrast, knockdown or inhibition of heparanase markedly attenuates tumor progression, further underscoring the potential of anti-heparanase therapy. Heparanase inhibitors were employed to interfere with tumor progression in preclinical studies, and selected heparin mimetics are being examined in clinical trials. However, despite tremendous efforts, the discovery of heparanase inhibitors with high clinical benefit and minimal adverse effects remains a therapeutic challenge. This review discusses the key roles of heparanase in cancer progression focusing on the status of natural, chemically modified, and synthetic heparanase inhibitors in various types of malignancies.

Hyperlipidemias and Obesity

The organs require oxygen and other types of nutrients (amino acids, sugars, and lipids) to function, the heart consuming large amounts of fatty acids for oxidation and adenosine triphosphate (ATP) generation.

Helicobacter pylori infection enhances heparanase leading to cell proliferation via mitogen‑activated protein kinase signalling in human gastric cancer cells

Helicobacter pylori (H. pylori) infection is the most important factor in the development of gastric cancer. Heparanase (HPA) is involved in tissue remodelling and cell migration, which leads to inflammation and tumour metastasis. The current study aimed was to explore whether a H. pylori infection leads to an increase in the level of HPA in gastric cancer and to investigate the specific mechanism underlying this association. Reverse transcription‑polymerase chain reaction and western blotting were used to detect HPA mRNA and protein expression, respectively, in MKN‑45 cells infected by H. pylori, MKN‑45 cells treated with the mitogen‑activated protein kinase (MAPK) inhibitor SB203580 and MKN‑45 cells transfected with small interfering RNA against HPA. MAPK and nuclear factor (NF)‑κB expression were determined by western blotting in the different cells group. Cell Counting Kit‑8, Transwell method, and Scratch and Clone tests were conducted to detect proliferation, invasion, migration and clone formation ability of gastric cancer cells. It was demonstrated that HPA mRNA expression was highest at 6 h post‑infection, while the expression of the HPA protein was highest at 24 h post‑infection in H. pylori‑infected gastric cancer cells. Furthermore, it was demonstrated that H. pylori infection significantly enhanced the expression of MAPK and NF‑κB in MKN‑45 cells at the mRNA and protein levels. SB203580 significantly decreased the expression of NF‑κB in MKN‑45 cells infected with H. pylori. Exposure to SB203580 also significantly decreased the expression of HPA. In the present study, the inhibition of HPA significantly lowered H. pylori‑induced cell proliferation, suggesting that H. pylori infection induces the proliferation of gastric cancer cells through the upregulation of HPA. Taken together, the results of the present study demonstrated that HPA serves a critical role in the development of gastric cancer in H. pylori‑infected cells, which may be an important mechanism through which H. pylori infection leads to gastric cancer. In addition, H. pylori infection promotes the proliferation, invasion and metastasis of gastric cancer cells through the upregulation of HPA expression, and this is likely mediated via the MAPK and NF‑κB signalling pathways. These data suggest that HPA can be used as a therapeutic target in gastric cancer, particularly in cases induced by H. pylori infection.

Dual effects of hyperglycemia on endothelial cells and cardiomyocytes to enhance coronary LPL activity

In the diabetic heart, there is excessive dependence on fatty acid (FA) utilization to generate ATP. Lipoprotein lipase (LPL)-mediated hydrolysis of circulating triglycerides is suggested to be the predominant source of FA for cardiac utilization during diabetes. In the heart, the majority of LPL is synthesized in cardiomyocytes and secreted onto cell surface heparan sulfate proteoglycan (HSPG), where an endothelial cell (EC)-releasable β-endoglycosidase, heparanase cleaves the side chains of HSPG to liberate LPL for its onward movement across the EC. EC glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1) captures this released enzyme at its basolateral side and shuttles it across to its luminal side. We tested whether the diabetes-induced increase of transforming growth factor-β (TGF-β) can influence the myocyte and EC to help transfer LPL to the vascular lumen to generate triglyceride-FA. In response to high glucose and EC heparanase secretion, this endoglycosidase is taken up by the cardiomyocyte (Wang Y, Chiu AP, Neumaier K, Wang F, Zhang D, Hussein B, Lal N, Wan A, Liu G, Vlodavsky I, Rodrigues B. Diabetes 63: 2643–2655, 2014) to stimulate matrix metalloproteinase-9 expression and the conversion of latent to active TGF-β. In the cardiomyocyte, TGF-β activation of RhoA enhances actin cytoskeleton rearrangement to promote LPL trafficking and secretion onto cell surface HSPG. In the EC, TGF-β signaling promotes mesodermal homeobox 2 translocation to the nucleus, which increases the expression of GPIHBP1, which facilitates movement of LPL to the vascular lumen. Collectively, our data suggest that in the diabetic heart, TGF-β actions on the cardiomyocyte promotes movement of LPL, whereas its action on the EC facilitates LPL shuttling.

NEW & NOTEWORTHY Endothelial cells, as first responders to hyperglycemia, release heparanase, whose subsequent uptake by cardiomyocytes amplifies matrix metalloproteinase-9 expression and activation of transforming growth factor-β. Transforming growth factor-β increases lipoprotein lipase secretion from cardiomyocytes and promotes mesodermal homeobox 2 to enhance glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1-dependent transfer of lipoprotein lipase across endothelial cells, mechanisms that accelerate fatty acid utilization by the diabetic heart.

JAK-2 V617F mutation increases heparanase procoagulant activity

Patients with polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF) are at increased risk of arterial and venous thrombosis. In patients with ET a positive correlation was observed between JAK-2 V617F mutation, that facilitates erythropoietin receptor signalling, and thrombotic events, although the mechanism involved is not clear. We previously demonstrated that heparanase protein forms a complex and enhances the activity of the blood coagulation initiator tissue factor (TF) which leads to increased factor Xa production and subsequent activation of the coagulation system. The present study was aimed to evaluate heparanase procoagulant activity in myeloproliferative neoplasms. Forty bone marrow biopsies of patients with ET, PV, PMF and chronic myelogenous leukaemia (CML) were immunostained to heparanase, TF and TF pathway inhibitor (TFPI). Erythropoietin receptor positive cell lines U87 human glioma and MCF-7 human breast carcinoma were studied. Heparanase and TFPI staining were more prominent in ET, PV and PMF compared to CML. The strongest staining was in JAK-2 positive ET biopsies. Heparanase level and procoagulant activity were higher in U87 cells transfected to over express JAK-2 V617F mutation compared to control and the effect was reversed using JAK-2 inhibitors (Ruxolitinib, VZ3) and hydroxyurea, although the latter drug did not inhibit JAK-2 phosphorylation. Erythropoietin increased while JAK-2 inhibitors decreased the heparanase level and procoagulant activity in U87 and MCF-7 parental cells. In conclusion, JAK-2 is involved in heparanase up-regulation via the erythropoietin receptor. The present findings may potentially point to a new mechanism of thrombosis in JAK-2 positive ET patients.

Opposing Functions of Heparanase-1 and Heparanase-2 in Cancer Progression

Heparanase, the sole heparan sulfate (HS)-degrading endoglycosidase, regulates multiple biological activities that enhance tumor growth, metastasis, angiogenesis, and inflammation. Heparanase accomplishes this by degrading HS and thereby regulating the bioavailability of heparin-binding proteins; priming the tumor microenvironment; mediating tumor-host crosstalk; and inducing gene transcription, signaling pathways, exosome formation, and autophagy that together promote tumor cell performance and chemoresistance. By contrast, heparanase-2, a close homolog of heparanase, lacks enzymatic activity, inhibits heparanase activity, and regulates selected genes that promote normal differentiation, endoplasmic reticulum stress, tumor fibrosis, and apoptosis, together resulting in tumor suppression. The emerging premise is that heparanase is a master regulator of the aggressive phenotype of cancer, while heparanase-2 functions as a tumor suppressor.

Chemotherapy induces secretion of exosomes loaded with heparanase that degrades extracellular matrix and impacts tumor and host cell behavior

The heparan sulfate-degrading enzyme heparanase promotes the progression of many cancers by driving tumor cell proliferation, metastasis and angiogenesis. Heparanase accomplishes this via multiple mechanisms including its recently described effect on enhancing biogenesis of tumor exosomes. Because we recently discovered that heparanase expression is upregulated in myeloma cells that survive chemotherapy, we were prompted to investigate the impact of anti-myeloma drugs on exosome biogenesis. When myeloma cells were exposed to the commonly utilized anti-myeloma drugs bortezomib, carfilzomib or melphalan, exosome secretion by the cells was dramatically enhanced. These chemotherapy-induced exosomes (chemoexosomes) have a proteome profile distinct from cells not exposed to drug including a dramatic elevation in the level of heparanase present as exosome cargo. The chemoexosome heparanase was not found inside the chemoexosome, but was present on the exosome surface where it was capable of degrading heparan sulfate embedded within an extracellular matrix. When exposed to myeloma cells, chemoexosomes transferred their heparanase cargo to those cells, enhancing their heparan sulfate degrading activity and leading to activation of ERK signaling and an increase in shedding of the syndecan-1 proteoglycan. Exposure of chemoexosomes to macrophages enhanced their secretion of TNF-α, an important myeloma growth factor. Moreover, chemoexosomes stimulated macrophage migration and this effect was blocked by H1023, a monoclonal antibody that inhibits heparanase enzymatic activity. These data suggest that anti-myeloma therapy ignites a burst of exosomes having a high level of heparanase that remodels extracellular matrix and alters tumor and host cell behaviors that likely contribute to chemoresistance and eventual patient relapse.

SUMMARY

We find that anti-myeloma chemotherapy dramatically stimulates secretion of exosomes and alters exosome composition. Exosomes secreted during therapy contain high levels of heparanase on their surface that can degrade ECM and also can be transferred to both tumor and host cells, altering their behavior in ways that may enhance tumor survival and progression.

Autocrine mechanisms of cancer chemoresistance

An ever-increasing number of studies highlight the role of cancer secretome in the modification of tumour microenvironment and in the acquisition of cancer cell resistance to therapeutic drugs. The knowledge of the mechanisms underlying the relationship between cancer cell-secreted factors and chemoresistance is becoming fundamental for the identification of novel anticancer therapeutic strategies overcoming drug resistance and novel prognostic secreted biomarkers. In this review, we summarize the novel findings concerning the regulation of secreted molecules by cancer cells compromising drug sensitivity. In particular, we highlight data from available literature describing the involvement of cancer cell-secreted molecules determining chemoresistance in an autocrine manner, including: i) growth factors; ii) glycoproteins; iii) inflammatory cytokines; iv) enzymes and chaperones; and v) tumor-derived exosomes.

Heparanase promotes neuroinflammatory response during subarachnoid hemorrhage in rats

BACKGROUND

Heparanase, a mammalian endo-β-D-glucoronidase that specifically degrades heparan sulfate, has been implicated in inflammation and ischemic stroke. However, the role of heparanase in neuroinflammatory response in subarachnoid hemorrhage (SAH) has not yet been investigated. This study was designed to examine the association between heparanase expression and neuroinflammation during subarachnoid hemorrhage.

METHODS

Rats were subjected to SAH by endovascular perforation, and the expression of heparanase was determined by Western blot analysis and immunofluorescence in the ipsilateral brain cortex at 24 h post-SAH. Pial venule leukocyte trafficking was monitored by using intravital microscopy through cranial window.

RESULTS

Our results indicated that, compared to their sham-surgical controls, the rats subjected to SAH showed marked elevation of heparanase expression in the ipsilateral brain cortex. The SAH-induced elevation of heparanase was accompanied by increased leukocyte trafficking in pial venules and significant neurological deficiency. Intracerebroventricular application of a selective heparanase inhibitor, OGT2115, which was initiated at 3 h after SAH, significantly suppressed the leukocyte trafficking and improved the neurological function.

CONCLUSIONS

Our findings indicate that heparanase plays an important role in mediating the neuroinflammatory response after SAH and contributes to SAH-related neurological deficits and early brain injury following SAH.

Heparanase: Potential roles in multiple sclerosis

Heparanase is a heparan sulfate degrading enzyme that cleaves heparan sulfate (HS) chains present on HS proteoglycans (HSPGs), and has been well characterized for its roles in tumor metastasis and inflammation. However, heparanase is emerging as a contributing factor in the genesis and severity of a variety of neurodegenerative diseases and conditions. This is in part due to the wide variety of HSPGs on which the presence or absence of HS moieties dictates protein function. This includes growth factors, chemokines, cytokines, as well as components of the extracellular matrix (ECM) which in turn regulate leukocyte infiltration into the CNS. Roles for heparanase in stroke, Alzheimer's disease, and glioma growth have been described; roles for heparanase in other disease such as multiple sclerosis (MS) are less well established. However, given its known roles in inflammation and leukocyte infiltration, it is likely that heparanase also contributes to MS pathology. In this review, we will briefly summarize what is known about heparanase roles in the CNS, and speculate as to its potential role in regulating disease progression in MS and its animal model EAE (experimental autoimmune encephalitis), which may justify testing of heparanase inhibitors for MS treatment.

Activity-based probes for functional interrogation of retaining β-glucuronidases

Humans express at least two distinct β-glucuronidase enzymes that are involved in disease: exo-acting β-glucuronidase (GUSB), whose deficiency gives rise to mucopolysaccharidosis type VII, and endo-acting heparanase (HPSE), whose overexpression is implicated in inflammation and cancers. The medical importance of these enzymes necessitates reliable methods to assay their activities in tissues. Herein, we present a set of β-glucuronidase-specific activity-based probes (ABPs) that allow rapid and quantitative visualization of GUSB and HPSE in biological samples, providing a powerful tool for dissecting their activities in normal and disease states. Unexpectedly, we find that the supposedly inactive HPSE proenzyme proHPSE is also labeled by our ABPs, leading to surprising insights regarding structural relationships between proHPSE, mature HPSE, and their bacterial homologs. Our results demonstrate the application of β-glucuronidase ABPs in tracking pathologically relevant enzymes and provide a case study of how ABP-driven approaches can lead to discovery of unanticipated structural and biochemical functionality.

Loss of VEGFB and its signaling in the diabetic heart is associated with increased cell death signaling

Vascular endothelial growth factor B (VEGFB) is highly expressed in metabolically active tissues, such as the heart and skeletal muscle, suggesting a function in maintaining oxidative metabolic and contractile function in these tissues. Multiple models of heart failure have indicated a significant drop in VEGFB. However, whether there is a role for decreased VEGFB in diabetic cardiomyopathy is currently unknown. Of the VEGFB located in cardiomyocytes, there is a substantial and readily releasable pool localized on the cell surface. The immediate response to high glucose and the secretion of endothelial heparanase is the release of this surface-bound VEGFB, which triggers signaling pathways and gene expression to influence endothelial cell (autocrine action) and cardiomyocyte (paracrine effects) survival. Under conditions of hyperglycemia, when VEGFB production is impaired, a robust increase in vascular endothelial growth factor receptor (VEGFR)-1 expression ensues as a possible mechanism to enhance or maintain VEGFB signaling. However, even with an increase in VEGFR1 after diabetes, cardiomyocytes are unable to respond to VEGFB. In addition to the loss of VEGFB production and signaling, evaluation of latent heparanase, the protein responsible for VEGFB release, also showed a significant decline in expression in whole hearts from animals with chronic or acute diabetes. Defects in these numerous VEGFB pathways were associated with an increased cell death signature in our models of diabetes. Through this bidirectional interaction between endothelial cells (which secrete heparanase) and cardiomyocytes (which release VEGFB), this growth factor could provide the diabetic heart protection against cell death and may be a critical tool to delay or prevent cardiomyopathy.

NEW & NOTEWORTHY We discovered a bidirectional interaction between endothelial cells (which secrete heparanase) and cardiomyocytes [which release vascular endothelial growth factor B (VEGFB)]. VEGFB promoted cell survival through ERK and cell death gene expression. Loss of VEGFB and its downstream signaling is an early event following hyperglycemia, is sustained with disease progression, and could explain diabetic cardiomyopathy.