Heparanase Blockade as a Novel Dual-Targeting Therapy for COVID-19.

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused over 5 million deaths worldwide. Pneumonia and systemic inflammation contribute to its high mortality. Many viruses use heparan sulfate proteoglycans as coreceptors for viral entry, and heparanase (HPSE) is a known regulator of both viral entry and inflammatory cytokines. We evaluated the heparanase inhibitor Roneparstat, a modified heparin with minimum anticoagulant activity, in pathophysiology and therapy for COVID-19. We found that Roneparstat significantly decreased the infectivity of SARS-CoV-2, SARS-CoV-1, and retroviruses (human T-lymphotropic virus 1 [HTLV-1] and HIV-1) in vitro. Single-cell RNA sequencing (scRNA-seq) analysis of cells from the bronchoalveolar lavage fluid of COVID-19 patients revealed a marked increase in HPSE gene expression in CD68+ macrophages compared to healthy controls. Elevated levels of HPSE expression in macrophages correlated with the severity of COVID-19 and the expression of inflammatory cytokine genes, including IL6, TNF, IL1B, and CCL2. In line with this finding, we found a marked induction of HPSE and numerous inflammatory cytokines in human macrophages challenged with SARS-CoV-2 S1 protein. Treatment with Roneparstat significantly attenuated SARS-CoV-2 S1 protein-mediated inflammatory cytokine release from human macrophages, through disruption of NF-κB signaling. HPSE knockdown in a macrophage cell line also showed diminished inflammatory cytokine production during S1 protein challenge. Taken together, this study provides a proof of concept that heparanase is a target for SARS-CoV-2-mediated pathogenesis and that Roneparstat may serve as a dual-targeted therapy to reduce viral infection and inflammation in COVID-19. IMPORTANCE The complex pathogenesis of COVID-19 consists of two major pathological phases: an initial infection phase elicited by SARS-CoV-2 entry and replication and an inflammation phase that could lead to tissue damage, which can evolve into acute respiratory failure or even death. While the development and deployment of vaccines are ongoing, effective therapy for COVID-19 is still urgently needed. In this study, we explored HPSE blockade with Roneparstat, a phase I clinically tested HPSE inhibitor, in the context of COVID-19 pathogenesis. Treatment with Roneparstat showed wide-spectrum anti-infection activities against SARS-CoV-2, HTLV-1, and HIV-1 in vitro. In addition, HPSE blockade with Roneparstat significantly attenuated SARS-CoV-2 S1 protein-induced inflammatory cytokine release from human macrophages through disruption of NF-κB signaling. Together, this study provides a proof of principle for the use of Roneparstat as a dual-targeting therapy for COVID-19 to decrease viral infection and dampen the proinflammatory immune response mediated by macrophages.

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.

Proteoglycan Chemical Diversity Drives Multifunctional Cell Regulation and Therapeutics.

The extracellular matrix (ECM) constitutes a highly dynamic three-dimensional structural network comprised of macromolecules, such as proteoglycans/glycosaminoglycans (PGs/GAGs), collagens, laminins, fibronectin, elastin, other glycoproteins and proteinases. In recent years, the field of PGs has expanded rapidly. Due to their high structural complexity and heterogeneity, PGs mediate several homeostatic and pathological processes. PGs consist of a protein core and one or more covalently attached GAG chains, which provide the protein cores with the ability to interact with several proteins. The GAG building blocks of PGs significantly influence the chemical and functional properties of PGs. The primary goal of this comprehensive review is to summarize major achievements and paradigm-shifting discoveries made on the PG/GAG chemistry-biology axis, focusing on structural variability, structure-function relationships, metabolic, molecular, and epigenetic mechanisms underlying their synthesis. Recent insights related to exosome biogenesis, degradation, and cell signaling, their status as diagnostic tools and potential pharmacological targets in diseases as well as current applications in nanotechnology and biotechnology are addressed. Moreover, issues related to docking studies, molecular modeling, GAG/PG interaction networks, and their integration are discussed.

Heparanase: A Dynamic Promoter of Myeloma Progression.

It has been speculated for many years that heparanase plays an important role in the progression of cancer due largely to the finding that its expression is weak or absent in normal tissues but generally as tumors become more aggressive heparanase expression increases. However, it is only in the last decade or so that we have begun to understand the molecular mechanism behind the sinister role that heparanase plays in cancer. In this review, we describe the many functions of heparanase in promoting the growth, angiogenesis and metastasis of multiple myeloma, a devastating cancer that localizes predominantly within the bone marrow and spreads throughout the skeletal system devouring bone and ultimately leading to death of almost all patients diagnosed with this disease. We also explore recent discoveries related to how heparanase primes exosome biogenesis and how heparanase enhances myeloma tumor chemoresistance. Discovery of these multiple tumor-promoting pathways that are driven by heparanase identified the enzyme as an ideal target for therapy, an approach recently tested in a Phase I trial in myeloma patients.

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.

Fibronectin on the Surface of Extracellular Vesicles Mediates Fibroblast Invasion.

Extracellular vesicles (EVs) are endosome and plasma membrane-derived nano-sized vesicles that participate in intercellular signaling. Although EV cargo may signal via multiple mechanisms, how signaling components on the surface of EVs mediate cellular signaling is less well understood. In this study, we show that fibroblast-derived EVs carry fibronectin on the vesicular surface, as evidenced by mass spectrometry-based proteomics (Sequential Window Acquisition of all Theoretical Mass Spectra) and flow-cytometric analyses. Fibroblasts undergoing replicative senescence or transforming growth factor ß1-induced senescence and fibroblasts isolated from human subjects with an age-related lung disorder, idiopathic pulmonary fibrosis, secreted higher numbers of EVs than their respective controls. Fibroblast-derived EVs induced an invasive phenotype in recipient fibroblasts. This invasive fibroblast phenotype was dependent on EV surface localization of fibronectin, interaction with the fibronectin receptor α5ß1 integrin, and activation of invasion-associated signaling pathways involving focal adhesion kinase and Src family kinases. EVs in the cellular supernatant, unbound to the extracellular matrix, were capable of mediating invasion signaling on recipient fibroblasts, supporting a direct interaction of EV surface fibronectin with the plasma membrane of recipient cells. Together, these studies uncover a novel mechanism of EV signaling of fibroblast invasion that may be relevant in the pathogenesis of fibrotic diseases and cancer.

Fibronectin on the Surface of Myeloma Cell-derived Exosomes Mediates Exosome-Cell Interactions.

Exosomes regulate cell behavior by binding to and delivering their cargo to target cells; however, the mechanisms mediating exosome-cell interactions are poorly understood. Heparan sulfates on target cell surfaces can act as receptors for exosome uptake, but the ligand for heparan sulfate on exosomes has not been identified. Using exosomes isolated from myeloma cell lines and from myeloma patients, we identify exosomal fibronectin as a key heparan sulfate-binding ligand and mediator of exosome-cell interactions. We discovered that heparan sulfate plays a dual role in exosome-cell interaction; heparan sulfate on exosomes captures fibronectin, and on target cells it acts as a receptor for fibronectin. Removal of heparan sulfate from the exosome surface releases fibronectin and dramatically inhibits exosome-target cell interaction. Antibody specific for the Hep-II heparin-binding domain of fibronectin blocks exosome interaction with tumor cells or with marrow stromal cells. Regarding exosome function, fibronectin-mediated binding of exosomes to myeloma cells activated p38 and pERK signaling and expression of downstream target genes DKK1 and MMP-9, two molecules that promote myeloma progression. Antibody against fibronectin inhibited the ability of myeloma-derived exosomes to stimulate endothelial cell invasion. Heparin or heparin mimetics including Roneparstat, a modified heparin in phase I trials in myeloma patients, significantly inhibited exosome-cell interactions. These studies provide the first evidence that fibronectin binding to heparan sulfate mediates exosome-cell interactions, revealing a fundamental mechanism important for exosome-mediated cross-talk within tumor microenvironments. Moreover, these results imply that therapeutic disruption of fibronectin-heparan sulfate interactions will negatively impact myeloma tumor growth and progression.

Heparanase: From basic research to therapeutic applications in cancer and inflammation.

Heparanase, the sole heparan sulfate degrading endoglycosidase, regulates multiple biological activities that enhance tumor growth, angiogenesis and metastasis. Heparanase expression is enhanced in almost all cancers examined including various carcinomas, sarcomas and hematological malignancies. Numerous clinical association studies have consistently demonstrated that upregulation of heparanase expression correlates with increased tumor size, tumor angiogenesis, enhanced metastasis and poor prognosis. In contrast, knockdown of heparanase or treatments of tumor-bearing mice with heparanase-inhibiting compounds, markedly attenuate tumor progression further underscoring the potential of anti-heparanase therapy for multiple types of cancer. Heparanase neutralizing monoclonal antibodies block myeloma and lymphoma tumor growth and dissemination; this is attributable to a combined effect on the tumor cells and/or cells of the tumor microenvironment. In fact, 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 repertoire of the physio-pathological activities of heparanase is expanding. Specifically, heparanase regulates gene expression, activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and non-enzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive inflammatory responses, tumor survival, growth, dissemination and drug resistance; but in the same time, may fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, stress response, and heparan sulfate turnover. Heparanase is upregulated in response to chemotherapy in cancer patients and the surviving cells acquire chemoresistance, attributed, at least in part, to autophagy. Consequently, heparanase inhibitors used in tandem with chemotherapeutic drugs overcome initial chemoresistance, providing a strong rationale for applying anti-heparanase therapy in combination with conventional anti-cancer drugs. Heparin-like compounds that inhibit heparanase activity are being evaluated in clinical trials for various types of cancer. Heparanase neutralizing monoclonal antibodies are being evaluated in pre-clinical studies, and heparanase-inhibiting small molecules are being developed based on the recently resolved crystal structure of the heparanase protein. Collectively, the emerging premise is that heparanase expressed by tumor cells, innate immune cells, activated endothelial cells as well as other cells of the tumor microenvironment is a master regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a prime target for therapy.

Shed syndecan-1 translocates to the nucleus of cells delivering growth factors and inhibiting histone acetylation: a novel mechanism of tumor-host cross-talk.

The heparan sulfate proteoglycan syndecan-1 is proteolytically shed from the surface of multiple myeloma cells and is abundant in the bone marrow microenvironment where it promotes tumor growth, angiogenesis, and metastasis. In this study, we demonstrate for the first time that shed syndecan-1 present in the medium conditioned by tumor cells is taken up by bone marrow-derived stromal cells and transported to the nucleus. Translocation of shed syndecan-1 (sSDC1) to the nucleus was blocked by addition of exogenous heparin or heparan sulfate, pretreatment of conditioned medium with heparinase III, or growth of cells in sodium chlorate, indicating that sulfated heparan sulfate chains are required for nuclear translocation. Interestingly, cargo bound to sSDC1 heparan sulfate chains (i.e. hepatocyte growth factor) was transported to the nucleus along with sSDC1, and removal of heparan sulfate-bound cargo from sSDC1 abolished its translocation to the nucleus. Once in the nucleus, sSDC1 binds to the histone acetyltransferase enzyme p300, and histone acetyltransferase activity and histone acetylation are diminished. These findings reveal a novel function for shed syndecan-1 in mediating tumor-host cross-talk by shuttling growth factors to the nucleus and by altering histone acetylation in host cells. In addition, this work has broad implications beyond myeloma because shed syndecan-1 is present in high levels in many tumor types as well as in other disease states.

Insights into the key roles of proteoglycans in breast cancer biology and translational medicine.

Proteoglycans control numerous normal and pathological processes, among which are morphogenesis, tissue repair, inflammation, vascularization and cancer metastasis. During tumor development and growth, proteoglycan expression is markedly modified in the tumor microenvironment. Altered expression of proteoglycans on tumor and stromal cell membranes affects cancer cell signaling, growth and survival, cell adhesion, migration and angiogenesis. Despite the high complexity and heterogeneity of breast cancer, the rapid evolution in our knowledge that proteoglycans are among the key players in the breast tumor microenvironment suggests their potential as pharmacological targets in this type of cancer. It has been recently suggested that pharmacological treatment may target proteoglycan metabolism, their utilization as targets for immunotherapy or their direct use as therapeutic agents. The diversity inherent in the proteoglycans that will be presented herein provides the potential for multiple layers of regulation of breast tumor behavior. This review summarizes recent developments concerning the biology of selected proteoglycans in breast cancer, and presents potential targeted therapeutic approaches based on their novel key roles in breast cancer.

Family history of hematologic malignancies and risk of multiple myeloma: differences by race and clinical features.

PURPOSE: Multiple myeloma (MM) is the most common hematologic malignancy affecting Blacks in the USA, with standardized incidence rates that are twofold to threefold higher than Whites. The rationale for the disparity is unclear. METHODS: Using participants enrolled in the Molecular And Genetic Epidemiology study of myeloma (259 MM cases; 461 controls), we examined the risk of MM associated with family history of cancer, differences by race and among cases, defining clinical features. Risk estimates were calculated using odds ratios and corresponding 95% confidence intervals from logistic regression adjusted for confounders. RESULTS: Overall, MM risk in cases with relatives affected with any hematologic malignancy was significantly elevated compared to controls (OR 1.89, 95% CI 1.25-2.86). Myeloma risk associated with a family history of MM was higher than the risk associated with any hematologic malignancy (OR 3.75, 95% CI 1.75-8.05), and the effect was greater for Blacks (OR 20.9, 95% CI 2.59-168) than Whites (OR 2.04, 95% 0.83-5.04), among cases with early onset (≤60 years; OR 4.58, 95% CI 1.21-17.3) and with increasing numbers of affected relatives (p trend = 0.001). Overall, frequencies of end organ damage differed in cases with relatives affected with any hematologic malignancy and significantly more cases exhibited κ light chain restriction (OR 3.23, 95% CI 1.13-9.26). CONCLUSIONS: The excess risk of MM observed in Blacks and the variation in clinical features observed in MM patients according to family history of hematologic malignancy may be attributed to a shared germline and environmental susceptibility.

Heparanase regulates secretion, composition, and function of tumor cell-derived exosomes.

Emerging evidence indicates that exosomes play a key role in tumor-host cross-talk and that exosome secretion, composition, and functional capacity are altered as tumors progress to an aggressive phenotype. However, little is known regarding the mechanisms that regulate these changes. Heparanase is an enzyme whose expression is up-regulated as tumors become more aggressive and is associated with enhanced tumor growth, angiogenesis, and metastasis. We have discovered that in human cancer cells (myeloma, lymphoblastoid, and breast cancer), when expression of heparanase is enhanced or when tumor cells are exposed to exogenous heparanase, exosome secretion is dramatically increased. Heparanase enzyme activity is required for robust enhancement of exosome secretion because enzymatically inactive forms of heparanase, even when present in high amounts, do not dramatically increase exosome secretion. Heparanase also impacts exosome protein cargo as reflected by higher levels of syndecan-1, VEGF, and hepatocyte growth factor in exosomes secreted by heparanase-high expressing cells as compared with heparanase-low expressing cells. In functional assays, exosomes from heparanase-high cells stimulated spreading of tumor cells on fibronectin and invasion of endothelial cells through extracellular matrix better than did exosomes secreted by heparanase-low cells. These studies reveal that heparanase helps drive exosome secretion, alters exosome composition, and facilitates production of exosomes that impact both tumor and host cell behavior, thereby promoting tumor progression.

Heparanase: busy at the cell surface.

Heparanase activity is strongly implicated in structural remodeling of the extracellular matrix, a process which can lead to invasion by tumor cells. In addition, heparanase augments signaling cascades leading to enhanced phosphorylation of selected protein kinases and increased gene transcription associated with aggressive tumor progression. This function is apparently independent of heparan sulfate and enzyme activity, and is mediated by a novel protein domain localized at the heparanase C-terminus. Moreover, the functional repertoire of heparanase is expanded by its regulation of syndecan clustering, shedding, and mitogen binding. Recent reports indicate that modified glycol-split heparin, which inhibits heparanase activity, can profoundly inhibit the progression of tumor xenografts produced by myeloma and carcinoma cells, thus moving anti-heparanase therapy closer to reality.

Nuclear localization of heparanase 2 (Hpa2) attenuates breast carcinoma growth and metastasis.

Unlike the intense research effort devoted to exploring the significance of heparanase in cancer, very little attention was given to Hpa2, a close homolog of heparanase. Here, we explored the role of Hpa2 in breast cancer. Unexpectedly, we found that patients endowed with high levels of Hpa2 exhibited a higher incidence of tumor metastasis and survived less than patients with low levels of Hpa2. Immunohistochemical examination revealed that in normal breast tissue, Hpa2 localizes primarily in the cell nucleus. In striking contrast, in breast carcinoma, Hpa2 expression is not only decreased but also loses its nuclear localization and appears diffuse in the cell cytoplasm. Importantly, breast cancer patients in which nuclear localization of Hpa2 is retained exhibited reduced lymph-node metastasis, suggesting that nuclear localization of Hpa2 plays a protective role in breast cancer progression. To examine this possibility, we engineered a gene construct that directs Hpa2 to the cell nucleus (Hpa2-Nuc). Notably, overexpression of Hpa2 in breast carcinoma cells resulted in bigger tumors, whereas targeting Hpa2 to the cell nucleus attenuated tumor growth and tumor metastasis. RNAseq analysis was performed to reveal differentially expressed genes (DEG) in Hpa2-Nuc tumors vs. control. The analysis revealed, among others, decreased expression of genes associated with the hallmark of Kras, beta-catenin, and TNF-alpha (via NFkB) signaling. Our results imply that nuclear localization of Hpa2 prominently regulates gene transcription, resulting in attenuation of breast tumorigenesis. Thus, nuclear Hpa2 may be used as a predictive parameter in personalized medicine for breast cancer patients.

Heparanase enhances the insulin receptor signaling pathway to activate extracellular signal-regulated kinase in multiple myeloma.

ERK signaling regulates proliferation, survival, drug resistance, and angiogenesis in cancer. Although the mechanisms regulating ERK activation are not fully understood, we previously demonstrated that ERK phosphorylation is elevated by heparanase, an enzyme associated with aggressive behavior of many cancers. In the present study, myeloma cell lines expressing either high or low levels of heparanase were utilized to determine how heparanase stimulates ERK signaling. We discovered that the insulin receptor was abundant on cells expressing either high or low levels of heparanase, but the receptor was highly phosphorylated in heparanase-high cells compared with heparanase-low cells. In addition, protein kinase C activity was elevated in heparanase-high cells, and this enhanced expression of insulin receptor substrate-1 (IRS-1), the principle intracellular substrate for phosphorylation by the insulin receptor. Blocking insulin receptor function with antibody or a small molecule inhibitor or knockdown of IRS-1 expression using shRNA diminished heparanase-mediated ERK activation in the tumor cells. In addition, up-regulation of the insulin signaling pathway by heparanase and the resulting ERK activation were dependent on heparanase retaining its enzyme activity. These results reveal a novel mechanism whereby heparanase enhances activation of the insulin receptor signaling pathway leading to ERK activation and modulation of myeloma behavior.

Heparan sulfate chains of syndecan-1 regulate ectodomain shedding.

Matrix metalloproteinases release intact syndecan-1 ectodomains from the cell surface giving rise to a soluble, shed form of the proteoglycan. Although it is known that shed syndecan-1 controls diverse pathophysiological responses in cancer, wound healing, inflammation, infection, and immunity, the mechanisms regulating shedding remain unclear. We have discovered that the heparan sulfate chains present on syndecan core proteins suppress shedding of the proteoglycan. Syndecan shedding is dramatically enhanced when the heparan sulfate chains are enzymatically degraded or absent from the core protein. Exogenous heparan sulfate or heparin does not inhibit shedding, indicating that heparan sulfate must be attached to the core protein to suppress shedding. Regulation of shedding by heparan sulfate occurs in multiple cell types, for both syndecan-1 and syndecan-4 and in murine and human syndecans. Mechanistically, the loss of heparan sulfate enhances the susceptibility of the core protein to proteolytic cleavage by matrix metalloproteinases. Enhanced shedding of syndecan-1 following loss of heparan sulfate is accompanied by a dramatic increase in core protein synthesis. This suggests that in response to an increase in the rate of shedding, cells attempt to maintain a significant level of syndecan-1 on the cell surface. Together these data indicate that the amount of heparan sulfate present on syndecan core proteins regulates both the rate of syndecan shedding and core protein synthesis. These findings assign new functions to heparan sulfate chains, thereby broadening our understanding of their physiological importance and implying that therapeutic inhibition of heparan sulfate degradation could impact the progression of some diseases.

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.

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.

Effect of HPSE and HPSE2 SNPs on the Risk of Developing Primary Paraskeletal Multiple Myeloma.

Multiple myeloma (MM) is a plasma cell malignancy that is accompanied by hypercalcemia, renal failure, anemia, and lytic bone lesions. Heparanase (HPSE) plays an important role in supporting and promoting myeloma progression, maintenance of plasma cell stemness, and resistance to therapy. Previous studies identified functional single nucleotide polymorphisms (SNPs) located in the HPSE gene. In the present study, 5 functional HPSE SNPs and 11 novel HPSE2 SNPs were examined. A very significant association between two enhancer (rs4693608 and rs4693084), and two insulator (rs4364254 and rs4426765) HPSE SNPs and primary paraskeletal disease (PS) was observed. SNP rs657442, located in intron 9 of the HPSE2 gene, revealed a significant protective association with primary paraskeletal disease and lytic bone lesions. The present study demonstrates a promoting (HPSE gene) and protective (HPSE2 gene) role of gene regulatory elements in the development of paraskeletal disease and bone morbidity. The effect of signal discrepancy between myeloma cells and normal cells of the tumor microenvironment is proposed as a mechanism for the involvement of heparanase in primary PS. We suggest that an increase in heparanase-2 expression can lead to effective suppression of heparanase activity in multiple myeloma accompanied by extramedullary and osteolytic bone disease.