key: cord-0884506-bl2jhud4
authors: Mayfosh, Alyce J.; Nguyen, Tien K.; Hulett, Mark D.
title: The Heparanase Regulatory Network in Health and Disease
date: 2021-10-14
journal: Int J Mol Sci
DOI: 10.3390/ijms222011096
sha: dbb2fe0e4bfeafd0e2ca4447b28f6b0dce6af980
doc_id: 884506
cord_uid: bl2jhud4

The extracellular matrix (ECM) is a structural framework that has many important physiological functions which include maintaining tissue structure and integrity, serving as a barrier to invading pathogens, and acting as a reservoir for bioactive molecules. This cellular scaffold is made up of various types of macromolecules including heparan sulfate proteoglycans (HSPGs). HSPGs comprise a protein core linked to the complex glycosaminoglycan heparan sulfate (HS), the remodeling of which is important for many physiological processes such as wound healing as well as pathological processes including cancer metastasis. Turnover of HS is tightly regulated by a single enzyme capable of cleaving HS side chains: heparanase. Heparanase upregulation has been identified in many inflammatory diseases including atherosclerosis, fibrosis, and cancer, where it has been shown to play multiple roles in processes such as epithelial-mesenchymal transition, angiogenesis, and cancer metastasis. Heparanase expression and activity are tightly regulated. Understanding the regulation of heparanase and its downstream targets is attractive for the development of treatments for these diseases. This review provides a comprehensive overview of the regulators of heparanase as well as the enzyme’s downstream gene and protein targets, and implications for the development of new therapeutic strategies.

The extracellular matrix (ECM) is a complex three-dimensional structural network comprised of proteins and polysaccharides that surround cells and tissues in multicellular organisms. This extracellular architecture is responsible for offering structural support and integrity to tissues and provides protection from invading cells and pathogens. It also has roles in many cellular processes, including cell survival, growth, migration, and differentiation [1] . Key components of the ECM include proteoglycans and fibrous proteins such as collagen, elastin, fibronectin, and laminin. Of particular interest to this review are the heparan sulfate proteoglycans (HSPGs).

The HSPGs are comprised of a protein core with covalently linked side chains of the variably sulfated glycosaminoglycan heparan sulfate (HS). HSPGs are found within the ECM (agrin, perlecan, and type XVIII collagen), bound to the cell membrane (syndecans and glypicans), or within secretory vesicles (serglycin) [2, 3] . They can also be found in the nucleus [4] .

There are many proteins that bind HS (Table 1) . Indeed, over 400 human proteins have been shown to bind HS or the structurally related heparin [5] (where heparin-binding likely predicts HS-binding abilities). Many of these binding proteins have been confirmed by proteomic, surface plasmon resonance, and column chromatographic methods. These proteins include growth factors, e.g., fibroblast growth factor (FGF); cytokines, e.g., monocyte chemoattractant protein-1 (MCP-1); and other ECM components, e.g., collagen. HS-binding molecules either interact through a specific HS-binding sequence motif, e.g., FGF [6] or in a nonspecific charge-dependent manner, e.g., fibronectin [7, 8] . By binding HS, these proteins are sequestered within the matrix. Many also require HS for activity; for example, the formation of many chemokine gradients requires HS to facilitate chemokine oligomerization [9] .

The abundance of HS on the cell surface and its importance in several pathways led to the discovery that HS acts as a co-receptor for several signaling receptors. These include the FGF receptor (FGFR) where cell surface HS is required for activation of the receptor [10] and vascular endothelial growth factor receptor (VEGFR) where HS can activate VEGFR in trans-from neighboring cells [11] . HS expressed on the surface of endothelial cells also acts as an adhesion receptor for migrating lymphocytes [12] . Given the diverse roles of HS in normal physiology and disease, its regulation and turnover are important to understand. In mammals, the turnover of HS and therefore ECM homeostasis is regulated by one enzyme: heparanase. Table 1 . Mammalian heparan sulfate-binding proteins.

Amyloid peptide β (1-42) Surface plasmon resonance [13] Amyloid precursor protein Fluorescence lifetime imaging microscopy [14] Annexin V Affinity chromatography [15] Basic fibroblast growth factor (bFGF) (FGF-2)

Iodinated-bFGF and specific activity following heparanase addition; Affinity chromatography; Iodinated-bFGF and specific activity;

Cross-linking of iodinated-bFGF following heparitinase treatment [16] [17] [18] [19] Collagen I Affinity chromatography; Surface plasmon resonance [13, 20] Collagen V Solid phase binding assay; Surface plasmon resonance [21, 22] Collagenase IV Antibody-linked detection assay; Surface plasmon resonance [13, 23] Collagen VI Surface plasmon resonance [13] chemokine (C-X-C motif) ligand (CXCL1) (KC) Surface plasmon resonance [24] CXCL2 (MIP-2) Surface plasmon resonance [24] CXCL6 (GCP-2) Surface plasmon resonance [24] CXCL10 (IP-10) Alkaline phosphatase-conjucated IP-10; Surface plasmon resonance [24, 25] CXCL11 (I-TAC) Surface plasmon resonance [24] CXCL13 Surface plasmon resonance [26] Endostatin Alkaline phosphatase-endostatin binding assay; Filter-binding assay; Surface plasmon resonance [13, 27, 28] FGFR4 Affinity chromatography [29] Fibronectin Affinity chromatography; Antibody-linked detection assay [7, 8, 23] HGF Affinity chromatography [30] Histidine-rich glycoprotein Flow cytometry after heparanase treatment [31] 

High mobility group protein B1 Biotinylation and streptadivin-HRP detection [32] Integrin α5β1 Surface plasmon resonance [13] Interferon-β (IFN-β) Filter binding assay [33] Interleukin-8 (IL-8) Affinity co-electrophoresis [34] Laminin-1 Antibody-linked detection assay; Surface plasmon resonance [13, 23] L-selectin

Heparinase treatment of 35SO4-labeled L-selectin ligands and SDS-PAGE; Affinity chromatography [35, 36] Monocyte chemoattractant protein-1 (MCP-1)

Competitive binding to 3H-heparin by nitrocellulose membrane filtration and liquid scintillation [37] Macrophage migration inhibitory factor (MIF)

Flow cytometry of fluorescently labeled MIF on A549 cells after heparinase treatment [38] Macrophage inflammatory protein-1α (MIP-1α)

Affinity chromatography after heparinase treatment [39] NKp46 ELISA [40] Platelet-derived growth factor (PDGF) Surface plasmon resonance; Affinity chromatography [41, 42] Platelet Factor 4 Affinity co-electrophoresis [34] P-selectin Affinity chromatography [36] Receptor for advanced glycation end products (RAGE)

Biotinylation and streptadivin-HRP detection [32, 43] Regulated on activation normal T cell expressed and secreted (RANTES) (CCL5) (oligomerized, filamentous)

Surface plasmon resonance [24, 44] Receptor protein-tyrosine phosphatase-σ (RPTP-σ)

Blot overlay assay probing agrin and collagen with cPTP-σ-conditioned medium following heparinase digestion [45] Stromal cell-derived factor-1 (SDF-1) Flow cytometry of endothelial cells after heparinase treatment for bound SDF-1 [46] Transglutaminase-2 Surface plasmon resonance [13] Thrombospondin-1 Surface plasmon resonance [13] Vascular endothelial growth factor (VEGF)

Metabolic labeling of pHEBO cells overexpressing VEGF189 followed by heparinase treatment, immunoprecipitation, and SDS PAGE [47] CXCL, C-X-C motif ligand; IP-10, interferon-γ induced protein-10; MCP-1, monocyte chemoattractant protein-1; MIF, Macrophage migration inhibitory factor; MIP-1α, macrophage inflammatory protein-1α; PDGF, platelet-derived growth factor; RAGE, receptor for advanced glycation end products; RANTES, regulated on activation normal T cell expressed and secreted; RPTP-σ, receptor protein-tyrosine phosphatase-σ; SDF-1, stromal cell-derived factor-1.

Heparanase is a member of the glucuronidase family and recognizes HS polysaccharide chains at sites of high sulfation. It catalyzes the hydrolysis of the β-linkage joining glucuronic acid and N-acetylglucosamine residues in HS chains, generating polysaccharide fragments of 10-20 units long [48] . Heparanase has several roles in physiological functions including wound healing [49] and leukocyte trafficking [50] [51] [52] [53] . It also plays many roles in a number of different disease settings such as cancer and inflammatory diseases, where hep- [72] [73] [74] [75] [76] p53

Human and mouse Direct binding to the heparanase promoter reduced heparanase mRNA expression [77] Snail Mouse Overexpression of Snail in B16F1 cells increased heparanase mRNA expression [78] specificity protein 1 (SP1) and SP3 Human Direct binding to the heparanase promoter increased heparanase promoter activity [70] MicroRNA miR-1258 Human miRNA-1258 suppressed heparanase expression in breast cancer cells [79] miR-1252-5p

Overexpression of miR-1252-5p in multiple myeloma cells reduced heparanase mRNA and protein expression and activity [80] Cytokines

Treatment of endothelial cells with IFN-γ increased heparanase mRNA expression and activity [81] IL-1β Human and mouse Treatment of endothelial cells with IL-1β increased heparanase mRNA expression [73, 82] IL-2 Mouse Treatment of purified NK cells with IL-2 induced expression of both pro-heparanase and the catalytically active heparanase protein, more so when also cultured with IL-15 [50] IL-10 Human IL-10 treatment of SUM149 breast cancer cells modestly increased heparanase mRNA expression [83] Helicobacter pylori H. pylori infection of gastric cancer cells induced an upregulation of heparanase protein, which was dependent on MAPK signaling [113] Pseudomonas aeruginosa Mouse P. aeruginosa intracorneal infection in mice induced an upregulation of heparanase mRNA and enzymatically active protein in the cornea. This was from both infiltrating immune cells as well as from the corneal epithelium [114] Streptococcus pneumoniae Mouse Intranasal S. pneumoniae infection in mice increased heparanase protein expression [115] Bovine herpes virus Human Heparanase mRNA was upregulated upon epithelial cell infection in vitro [75] SARS-CoV-2 Human COVID-19 patients displayed elevated heparanase activity and soluble HS levels in the plasma; Increase shed syndecan-1 was observed [116, 117] Cytomegalovirus Human Heparanase mRNA was upregulated upon fibroblast cell infection in vitro [75] Dengue virus Human Dengue virus protein NS1 upregulated heparanase protein in endothelial cells, and upregulation was found to be macrophage inhibitory factor-dependent [118, 119] HSV-1 Human

Heparanase mRNA and protein were upregulated upon HSV-1 infection through NF-κB activation [75, 120] HSV-2 Human Heparanase mRNA was upregulated upon epithelial cell infection in vitro [75] Porcine reproductive and respiratory syndrome virus Pig

Piglets infected with PRSSV in vivo increased heparanase mRNA expression in alveolar macrophages Cells infected in vitro with PRSSV increased heparanase mRNA and protein expression [121, 122] Pseudorabies virus Human Heparanase mRNA was upregulated upon epithelial cell infection in vitro [75] Therapeutics Bortezomib Human Treatment of myeloma cells increased heparanase mRNA and protein expression [76] Carfilzomib Human Treatment of myeloma cells increased heparanase mRNA expression [76] Human epidermal keratinocytes exposed to UVB radiation exhibited increased heparanase enzymatic activity and detectable levels of the 50 kDa active subunit; Rats with experimental liver cirrhosis showed an increase in heparanase precursor protein in liver and serum after treatment with partial liver radiation [125, 126] Tamoxifen Human Treatment of MCF-7 cells with high concentration of tamoxifen inhibited estrogen-induced heparanase expression; Tamoxifen treatment of MCF-7 cells and T47D cells increased heparanase mRNA expression [100, 102] Miscellaneous Cerulein Mouse

Injection of cerulein into mice increased heparanase mRNA expression and enzymatic activity in pancreatic tissue extracts [127] AGE, Advanced glycation end product; DMTU, dimethylthiourea; eNOS, endothelial nitric oxide synthase; ERK, extracellular signalregulated kinase; ETS, E26 transformation-specific or E-twenty-six; GABP, GA-binding protein; HGF, hepatocyte growth factor; HMVEC, human microvascular endothelial cell; HSV, herpes simplex virus; hTERT, telomerase reverse transcriptase; LDL, low-density lipoprotein; LPS, lipopolysaccharide; MEK, mitogen-activated protein kinase; MCP, monocyte chemoattractant protein; PBMC, peripheral blood mononuclear cell; PI3K, phosphoinositide 3-kinases; SP, specificity protein; TLR4, Toll-like receptor 4; WT, wild type.

Wild-type p53 is a master regulator of normal cell cycle and apoptotic processes [128] . During cellular homeostasis, heparanase gene expression is suppressed by wild-type p53 via direct binding to the heparanase promoter [77] . Thus, the mutation of p53 that can occur during oncogenesis results in aberrant heparanase expression. As well as a lack of repression, heparanase expression can be actively upregulated. Through cloning and sequencing of the heparanase promoter, the transcription factors GA-binding protein (GABP), specificity protein 1 (Sp1), and Sp3 were found to directly upregulate heparanase gene expression [70] . Early growth response 1 (EGR1) was later shown to also positively regulate heparanase gene expression through direct activation of the heparanase promoter [61, 62, 66, 67] . Finally, NF-κB, a potent transcription factor downstream of many signaling pathways, can also increase heparanase expression in tumor cells [72, [74] [75] [76] ].

Micro RNAs (miRNAs) are emerging as important regulators of tumorigenesis given they regulate hundreds of mRNAs and are widely dysregulated in cancer [129] . In metastatic breast cancer cells, the miRNA miR-1258 was found to suppress heparanase expression and subsequently control tumor invasion and metastasis [79] . Patient tissues of invasive ductal carcinomas also exhibited lower levels of miR-1258 and higher heparanase expression relative to matched normal mammary gland tissue [79] . Another miRNA, miR-1252-5p, was also recently identified to regulate heparanase expression in multiple myeloma [80] . Since miRNAs show potential as directed therapeutics, miR-1258 may be a prospective candidate for treatment of heparanase-mediated metastatic cancer.

Heparanase plays several key roles during inflammation, including immune cell migration and cell signaling [130] . Thus, it is not surprising that several inflammatory cytokines have been shown to upregulate heparanase expression. These include interferonγ (IFN-γ), interleukin (IL)-1β, IL-2, IL-15, IL-17, MCP-1 and tumor necrosis factor-α (TNFα) [50, 81, 82, 85, 87, 88, 104, 131] . It remains unclear how several of these cytokines upregulate heparanase expression, though it is likely that the heparanase gene is a downstream target of these cytokine signaling pathways. However, for cytokines in which the mechanism has been explored, it appears that the mechanisms may differ in different settings. One study found that heparanase upregulation in TNF-α treated endothelial cells was independent of NF-κB, PI-3K, MAP kinase, and c-Jun kinase, but was dependent on caspase 8 [82] . In contrast, another study found that canonical NF-κB signaling was required for TNF-α induced heparanase upregulation in endothelial cells [73] . Another study to show TNF-α induction of heparanase (during colitis-associated tumorigenesis) proposed that since TNFα also induced upregulation of EGR1 [132, 133] that TNF-α induced heparanase expression via activation of EGR1, although this is yet to be confirmed.

There are still gaps in our understanding of how these cytokines upregulate heparanase. Defining the mechanisms of cytokine-mediated heparanase upregulation and their contribution in different physiological and disease settings is required to fully understand the relationship between cytokine signaling and heparanase function. Despite our gaps in understanding of how cytokines upregulate heparanase, there are clearly multiple mechanisms at play during inflammatory responses. This multifaceted upregulation of heparanase likely ensures its robust expression and thus contributes to both normal immune responses and inflammatory disease pathologies.

Growth factors can also regulate heparanase expression. Of these, VEGF was shown to act differentially depending on the setting: reducing heparanase expression in endothelial cells [82] and increasing heparanase expression in melanoma cells [92] . Hepatocyte growth factor (HGF) has also been shown to upregulate heparanase expression at the transcriptional level in lung and gastric cancer cells [89, 90] . In contrast to TNF-α described above, HGF upregulated heparanase in gastric cancer cells through the PI3 kinase/Akt/NF-κB pathway [90] . A number of other growth factors-basic fibroblast growth factor (bFGF), FGF23, and platelet-derived growth factor-have also been shown to increase heparanase expression in cancer cells [89, 91] . Thus, growth factors are another group of proteins that are central to regulating heparanase expression during physiological and pathological processes.

Other signaling molecules can also regulate heparanase expression, including hormones, metabolites, and reactive oxygen species (ROS). Estrogen signaling has been shown to influence heparanase expression. Estrogen in breast cancer cells increases heparanase expression [100, 102, 103] , and treatment of cholangiocarcinoma cells (bile duct cancer) with the estrogenic inducer 17β-estradiol upregulated heparanase mRNA [101] . Interestingly, estrogen stimulation of breast cancer cells at low concentrations induced higher expression levels of heparanase than high concentrations of estrogen [100] . During pregnancy, estrogen levels increase, which suggests pregnancy may protect against heparanase upregulation induced by low estrogen. Indeed, a clinical study found that the number of pregnancies correlates with a reduction in estrogen receptor-positive breast cancer risk [134] . Thus, it is possible that the induction of heparanase expression by low levels of estrogen in healthy breast tissue may contribute to the initiation of breast cancer.

The metabolites glucose and vitamin D also modulate heparanase expression [104] [105] [106] 111] . Treatment of either podocytes in vitro or a rat model of proteinuria with vitamin D (1,25-D 3 ) reduced heparanase mRNA expression [111] . Upon vitamin D binding, the vitamin D receptor directly bound to the heparanase promoter and blocked heparanase expression [111] . Furthermore, vitamin D deficient mice exhibited increased heparanase expression and activity [111] . This finding suggests that vitamin D may be a suitable treatment for proteinuria by targeting heparanase expression.

The induction of ROS has also been shown to regulate heparanase expression and secretion [106, 109, 110] . This suggests heparanase is regulated alongside other stress response genes. The mechanism of ROS-mediated heparanase upregulation has not been elucidated, however since ROS activates PI3K/AKT, MAPK signaling pathways, and NF-κB [135] which can upregulate heparanase, these pathways provide possible mechanisms of ROS-mediated heparanase upregulation.

An important role for heparanase during viral infection is emerging and has been recently reviewed [136, 137] . Multiple viruses including Herpes Simplex Virus-1 (HSV-1), cytomegalovirus, and Dengue virus have been shown to hijack heparanase expression to facilitate infection (Table 2) . By hijacking host pro-survival pathways and enabling viral egress, viruses exploit heparanase to their advantage. Other viruses, namely foot and mouth disease virus [138] , respiratory syncytial virus [139] , human papillomavirus [140] , and hepatitis B virus [141] , have been reported to require HS, the substrate of heparanase, for pathogenesis. This suggests they may also modulate heparanase expression to facilitate pathogenesis, but this is yet to be determined. Given the modulation of expression during infection, targeting heparanase during viral infection poses both diagnostic and therapeutic potential. The heparanase inhibitors heparin and the HS mimetic PI-88 were shown to inhibit poxvirus infection in vitro [142] , but whether this was mediated via inhibiting heparanase activity was not directly tested. Further understanding of the modulation and role of heparanase during these infections is required to verify heparanase as a viable target. Bacterial infection has also been shown to modulate heparanase expression. Fusobacterium nucleatum, which induces periodontal disease and can lead to oral carcinoma, was shown to increase heparanase expression upon infection in vitro [112] . Streptococcus pneumoniae infection in mice also increased heparanase protein levels [115] . Heparanase expression was also upregulated in mouse corneas following Pseudomonas aeruginosa (P. aeruginosa) infection [114] , where the source of heparanase was from both infiltrating immune cells and the corneal epithelium. The gut pathogen Helicobacter pylori (H. pylori) also induced heparanase expression in gastric cancer cells and this was found to be dependent on MAPK signaling [113] . Furthermore, in a clinical cohort of gastric cancer patients with H. pylori infection, heparanase expression correlated with poor overall survival and relapse-free survival [113] . A negative correlation between heparanase expression and cancer survival has been shown many times previously [143] [144] [145] . In the context of chronic bacterial and viral infections that can contribute to tumorigenesis, heparanase expression during this inflammatory pre-tumorigenic phase is likely a driver of tumorigenesis. There are other bacterial pathogens such as P. aeruginosa and Staphylococcus aureus which also interact with and induce shedding of HSPGs to promote bacterial pathogenesis and are reviewed by Garcia and colleagues [146, 147] . Given this, heparanase may also play a role in the pathogenesis of these bacterial infections. There may be many more bacterial species and viral strains which utilize heparanase for pathogenesis or induce a pro-inflammatory host response that drives heparanase expression, although this remains to be explored.

Therapies such as chemotherapeutics, immune activators, and radiation have all been shown to modulate heparanase expression. The observation that heparanase can confer chemotherapeutic resistance in cancer cells (reviewed in [148] ) led to the discovery that the chemotherapies bortezomib, carfilzomib, and doxorubicin can induce the upregulation of heparanase in vitro [76] . This upregulation of heparanase correlated with an increase in chemotherapeutic resistance through activation of the NF-κB pathway. This suggests that heparanase may be a potential target in overcoming chemoresistance. Indeed, later studies found that targeting heparanase can re-sensitize resistant tumor cells to chemotherapy and inhibit tumor cell growth in vitro and in vivo [149, 150] , presenting a promising approach to enhance chemotherapy response. One study identified in a colorectal cancer model that heparanase involvement in chemoresistance is 2-fold: (i) heparanase induces syndecan-1 shedding directly and (ii) heparanase induces upregulation of matrix metalloprotease-9 (MMP-9), which induces the binding of heparin-binding epithelial growth factor-like factor (HB-EGF) to epidermal growth factor (EGF) receptor (EGFR) and downstream MEK ERK signaling, leading to 5-Fluorouracil resistance [151] . These findings explain why tumor cells upregulate heparanase upon chemotherapy treatment and validate the use of heparanase as a chemotherapy-sensitizing target.

Given the role of heparanase in leukocyte functions, it is not surprising that compounds that modulate immune activation also modulate heparanase expression. PMA and ionomycin, potent inducers of leukocyte activation, can stimulate heparanase expression in lymphocytes [61] , neutrophils, and platelets [50, 124] . The viral RNA mimetic poly(I:C) can also upregulate heparanase in natural killer cells [50] . By upregulating heparanase during immune cell activation, these compounds enable heparanase-facilitated leukocyte functions such as cytokine production [152, 153] and migration [50, 51, 153] . These findings add to the growing body of literature on the importance of heparanase in immune cell function, however, more work is needed to fully define its importance in immunity.

Radiation has also been shown to increase heparanase expression. UVB irradiation of human skin samples and cultured keratinocytes induced heparanase expression and activity [125] and rats with liver cirrhosis that received partial liver irradiation showed an upregulation of the heparanase proenzyme in liver and serum [126] . These findings suggest heparanase may be a useful biomarker when monitoring response to radiation. Furthermore, as with chemoresistance, and the recently identified survival signature associated with heparanase [154] , heparanase upregulation may be another example of heparanase-mediated therapeutic resistance. The upregulation of heparanase upon treatment with these therapeutics may mean that combining with heparanase inhibitors could have synergistic benefits for anti-cancer treatments.

Heparanase is synthesized as an inactive proenzyme containing an 8 kDa and a 50 kDa subunit sequence joined by a linker sequence. This proenzyme then undergoes proteolytic processing by cathepsin L to remove the linker sequence and allow the heterodimerization of the two subunits to become an active enzyme [155, 156] . Cathepsin L expression and consequent heparanase activation have been linked to viral infection [118, 122] and pancreatitis [127] . Interestingly, in a model of acute pancreatitis, cathepsin L has also been shown to be regulated by heparanase, representing a self-sustaining loop which generates continuous heparanase activity [127] . In addition to cathepsin L, other proteases such as cysteine proteases, cathepsin B, D, S, and other aspartic proteases may also contribute to the activation of heparanase [155] . The existence of this proenzyme containing the linker sequence represents an efficient mechanism for rapid heparanase activation upon certain stimuli.

Heparanase enzymatic activity is also regulated by naturally occurring heparanase inhibitors. Although eosinophils produce heparanase, heparanase enzymatic activity in both resting and activated eosinophils is not detected. This is because eosinophils also express major basic protein which completely inhibits heparanase activity [157] . Two other eosinophil proteins, peroxidase and eosinophil cationic protein, also partially inhibit heparanase activity [157] . HS-interacting protein is also recognized as a natural endogenous heparanase inhibitor [158, 159] . HS-interacting protein binds HS on the cell surface and ECM, thus blocking heparanase access. Heparanase-2, the inactive homolog to the active enzyme, can also bind HS, in fact, with higher affinity than the enzymatically active heparanase to indirectly inhibit activity. Heparanase-2 has also been shown to directly interact with heparanase, and thus inhibit heparanase activity directly [160] . Heparin is another well-described natural inhibitor of heparanase activity. Solely expressed by mast cells, this highly sulfated form of HS inhibits heparanase activity by binding directly to the enzyme's active site [161] [162] [163] . Finally, heparanase enzymatic activity is affected by pH; enzymatic activity is limited to an acidic microenvironment, e.g., at sites of inflammation or in the core of solid tumors. The optimal pH for heparanase activity is 5.5 and no enzymatic activity is detected at a pH below 3.5 or above 7.0 [164] [165] [166] .

In addition to its many well-recognized functions, heparanase can also regulate gene expression via multiple direct and indirect mechanisms (Figure 2) . Heparanase can enter the nucleus to modify nuclear HS and even exert direct effects on gene transcription. Indeed, heparanase has been shown to enter the nucleus of myeloma cells and cleave nuclear HS on syndecan-1 [167] . Nuclear HS inhibits histone acetyltransferases (HATs), thereby inhibiting gene transcription [168] . By entering the nucleus and degrading nuclear syndecan-1, heparanase mediates HAT activation and transcription of genes associated with an aggressive tumor phenotype [168] . Conversely, nuclear heparanase has also been shown to bind non-specifically to DNA and compete for binding with NF-κB, thus preventing transcription of many NF-κB target genes and acting as a tumor suppressor [169] . Heparanase has also been identified in the nucleus of human glioma and breast cancer cell lines and in patient samples of squamous cell carcinoma [170] and adenocarcinoma [171] .

Chromatin immunoprecipitation experiments revealed that heparanase is recruited to promoters and 5 coding regions of microRNA genes miR-9 and miR-183 (previously implicated in cancer and epithelial-mesenchymal transition (EMT)) and other genes linked to development and differentiation pathways [172] . These studies suggest that in neoplastic cells, nuclear heparanase acts to drive tumor aggressiveness and heparanase localization in the nucleus can correlate with poor patient prognosis [171, 173, 174] .

Furthermore, in human Jurkat T cells, heparanase controls nuclear histone H3 methylation patterns to regulate expression of the immune response genes CD69, IL-2, and IFNγ [172] . Heparanase also contains two potential nuclear localization sequences, and enzymatically active heparanase has been found in the chromatin compartment of the nucleus, where it co-localizes with RNA polymerase II in T cells [172] . This nuclear heparanase positively controls the transcription of several genes in T cells important for immune function. 

The expression of heparanase is tightly regulated by many factors as described above. In contrast, heparanase itself is also involved in the regulation of different genes that contribute to a variety of physiological processes as well as disease settings. It has been reported that the expression of growth factors such as VEGF, HGF, bFGF, FGF-2, and transforming growth factor-β/β1 which play essential roles in EMT, bone formation, angiogenesis, tumor angiogenesis, and renal diseases, are regulated by heparanase. This effect of heparanase is observed in both in vivo and in vitro studies and is through either its enzymatic or non-enzymatic activities [76, 168, [175] [176] [177] [178] [179] [180] [181] .

Heparanase can also alter the expression of EMT gene markers such as Slug, Snail, vimentin, α-SMA, Fibronectin, Collagen-1, Cathepsin-L, Endothelin-1, and E-cadherin as well as stem cell markers (CXCR4, OCT3/4, and NANOG) which further contribute to the pathological processes such as acute kidney disease and gastric adenocarcinoma [179, 181, 182] . In addition, considerable evidence supports a role for heparanase in regulating genes encoding pro-inflammatory cytokines, chemokines, and other proteins involving macrophage activation, function, and polarization, namely IL-1b, IL-6, IL-10, IL-12p53, TNF-α, MIP-2, toll-like receptor-2 (TLR-2), TLR-4, iNOS, c-Fos, CXCL-12, lysozyme 1, VEGF-A, and caspase-1. The expression of these molecules as well as the activation of macrophages play important roles in diseases such as colitis-associated tumorigenesis [131] , ulcerative colitis [131] , and acute kidney injury [182] .

It is well-documented that heparanase overexpression occurs in most malignancies and is involved in tumor progression and prognosis. Here, heparanase contributes to the regulation of tumor-related processes, such as angiogenesis, inflammation, and tumor cell invasion and metastasis, reviewed in detail recently [64] . Heparanase has the ability to modify the expression of genes involved in these tumor-related processes including IL-17A [84] , MCP-1 [183] , MMPs [76, 79, 168, 169, 184] , TNF-α [153, 169] , VEGF [76, 168, 175, 177] , and VEGF-C [185] . It is worth noting that heparanase also plays an important role in regulating the expression of many different inflammation-related genes such as IL-1β, IL-5, IL-6, IL-8, IL-10, IL-13, and vascular cell adhesion molecule 1 (VCAM-1) [51, 120, 152, 183, 186] . Moreover, the silencing or overexpression of heparanase also impacts the expression of other ECM-degrading enzyme MMPs such as MMP-2, MMP-9, MMP-14, and MMP-25, which affect migration of immune cells to inflammatory sites. Heparanase-induced upregulation or downregulation of these genes seems to vary depending on the disease [51, 76, 79, 168, 169, 184] . The involvement of heparanase in the regulation of genes contributing to different physiological and pathological processes is listed in Table 3 . Table 3 . Genes and proteins that are regulated by heparanase.

The expression of aromatase was decreased in heparanase-knockout obese mice. Heparanase was required for the activation of fatty acid-stimulated macrophages to induce aromatase in adipose stromal cells Obesity-associated breast cancer progression [103] Bcl-XL (Bcl2l1)

Increased expression of Bcl-XL in heparanase overexpressing transgenic mice with dextran sulfate sodium (DSS)-induced colitis was regulated by NF-κB

Ulcerative colitis [131] 

Caspase-1

Silence of heparanase and heparanase inhibitor (SST0001) blocked caspase 1 expression in human kidney cells Acute kidney injury/M1 macrophage polarization [182] Cathepsin L Induction of acute kidney injury in heparanase-transgenic mice enhanced the expression of cathepsin L mRNA.

Pre-treatment with heparanase inhibitor PG545 reduced the expression of cathepsin L Epithelial-mesenchymal transition (EMT)/Acute kidney injury [179] CD44 siRNA knockdown of heparanase in SUM149 breast cancer cells reduced mRNA expression of CD44

Breast cancer [83] c-Fos (AP-1)

The expression of c-Fos was decreased in heparanase-knockout macrophages and adding exogenous heparanase enhanced c-Fos expression. Heparanase regulated the gene expression of c-Fos through Erk, p38, and JNK signaling pathway

Tumor/Induction of cytokine expression [153] Collagen-I HIF-2α Knockdown of heparanase in HUVEC cells reduced HIF-2α expression Tumor angiogenesis [190] IL-1β HS fragments generated by heparanase activated TLR4, MyD88, and NF-κB to upregulate IL-1β mRNA Inflammation [120, 152] The expression of IL-1β in macrophages isolated from heparanase-knockout mice was significantly reduced compared to macrophages isolated from wild type mice. Heparanase regulated IL-1β expression through Erk, p38, and JNK signaling pathway

Tumor/Regulation of cytokine expression in macrophage [153] Increased expression of IL-1β in heparanase overexpressing transgenic mice with colitis-associated carcinoma Colitis-associated tumor/Induction of NK-κB activation/Macrophage activation [131] Heparanase upregulated the expression of IL-1β in PMA-activated U937 macrophages. Treatment cells with heparanase inhibitor SST0001 reduced IL-1β expression Acute kidney injury/M1 macrophage polarization [182] IL-5

House dust mite (HDM)-induced allergic inflammation in heparanase deficient mice reduced mRNA expression of IL-5 in lung cells Allergic inflammation/Recruitment of eosinophils and mucus-secreting airway epithelial cells [51] The expression of IL-6 in macrophages isolated from heparanase deficient mice was significantly reduced compared to macrophages isolated from wild type mice. Heparanase regulated IL-6 expression through Erk, p38, and JNK signaling pathways

Tumor/Regulation of cytokine expression in macrophage [153] IL-6 mRNA expression was increased in heparanase transgenic mice with DSS-inducedcolitis. LPS-treated mouse peritoneal macrophages increased mRNA expression of IL-6 in the presence of recombinant enzymatically active heparanase

Ulcerative colitis/Induction of NK-κB activation/Macrophage recruitment and activation [131] Induction of acute kidney injury in heparanase-transgenic mice enhanced the expression of mRNA IL-6. Pre-treatment with heparanase inhibitior PG545 reduced the expression of IL-6

EMT/Acute kidney injury [179] Heparanase upregulated the expression of IL-6 in PMA-activated U937 macrophage cells. Treatment of cells with heparanase inhibitor SST0001 reduced IL-6 expression Acute kidney injury/M1 macrophage polarization [182] Heparanase induced the expression of IL-6 by fatty acid-stimulated macrophages in a dose-dependent manner

Obesity-associated breast cancer [103] IL-6 expression was increased in heparanase-knockout macrophages treated with exogenous heparanase and chemotherapy

Tumor Growth/Induction of pro-inflammatory cytokine expression by chemotherapy-treated macrophage [123] IL-8 HS fragments generated by heparanase activated TLR4, MyD88, and NF-κB to upregulate IL-8

Inflammation [152, 183] IL-10 IL-10 mRNA expression was reduced in chemotherapy-treated macrophages isolated from heparanase knockout mice Tumor Growth/Induction of pro-inflammatory cytokine expression by chemotherapy-treated macrophage [123] HS fragments generated by heparanase activated TLR4, MyD88, and NF-κB to upregulate IL-10

Inflammation [152] The expression of IL-10 in macrophages isolated from heparanase deficient mice was significantly reduced compared to macrophages isolated from wild type mice. Heparanase regulated IL-10 expression through Erk, p38, and JNK signaling pathway

Tumor/Regulation of cytokine expression in macrophage [153] Inhibition of heparanase with SST0001 reduced IL-10 mRNA expression in macrophages Acute kidney injury/M1 macrophage polarization [182] IL-13

(HDM-induced allergic inflammation in heparanase deficient mice reduced mRNA expression of IL-13 in lung cells Allergic inflammation/Recruitment of eosinophils and mucus-secreting airway epithelial cells [51] IL-12p53 LPS-treated mouse peritoneal macrophages increased mRNA expression of IL-12p53 in the presence of recombinant enzymatically active heparanase Ulcerative colitis/Macrophage activation [131] [191] matrix metalloprotease-2 (MMP-2)

The mRNA expression of MMP-2 was decreased in the kidney of heparanase deficient mice

Allergen-induced inflammation/DC migration [51] Human melanoma cells deficient in heparanase exhibited increased MMP-2 expression

Melanoma progression [169] Inhibiting heparanase with either PG545 or PI-88 in patient-derived explants of normal mammary tissue increased MMP-2 mRNA expression Tissue density and breast cancer [192] siRNA knockdown of heparanase in SUM149 breast cancer cells reduced MMP-2 mRNA expression Breast cancer [83] MMP-9

Addition of recombinant or chemotherapy-generated soluble heparanase elevated the expression of MMP-9 in myeloma cells. Chemotherapeutic induction of MMP-9 required heparanase through Erk phosphorylation

Tumor progression [76, 79, 184] The gene expression level of MMP-9 in heparanase-silenced human kidney 2 (HK2) cells was lower than wild type cells Renal fibrosis [193] Heparanase upregulated the expression of MMP-9 by its HS-degrading activity and stimulating HAT activity Myeloma tumor/Upregulation of HAT activity [168] Human melanoma cells deficient in heparanase exhibited increased MMP-9 expression

Melanoma progression [169] 

The mRNA expression of MMP-14 was decreased in the liver of heparanase deficient mice

Allergen-induced inflammation/DC migration [51] Inhibiting heparanase with either PG545 or PI-88 in patient-derived explants of normal mammary tissue increased MMP-14 mRNA expression

Tissue density and breast cancer [192] MMP-25

The mRNA expression of MMP25 was increased in the spleen but decreased in mouse bone marrow-derived DCs and Langerhans cells from heparanase deficient mice EMT/Gastric ring cell adenocarcinoma [181] α-SMA

EMT/Gastric ring cell adenocarcinoma [181] Heparanase-overexpressing micedisplayed remarkable upregulation of α-SMA during acute kidney injury. Pre-treatment with heparanase inhibitor PG545 abolished the increased expression of α-SMA in hpse-tg mice EMT/Acute kidney injury [179] Heparanase-silenced cells showed reduced α-SMA expression EMT/Acute kidney injury [182, 189] Snail Heparanase-silenced cells showed reduced Snail expression EMT/Acute kidney injury [182] 

Syndecan-1

Inhibiting heparanase with either PG545 or PI-88 in patient-derived explants of normal mammary tissue reduced syndecan-1 mRNA expression Tissue density and breast cancer [192] In transwell co-cultures of heparanase-silenced HCC cells and HUVECs, HUVECs displayed lower syndecan-1 mRNA and protein expression after co-culture compared to controls. In transwell co-cultures of heparanase-overexpressing HCC cells and HUVECs, HUVECs displayed higher syndecan-1 mRNA and protein expression after co-culture compared to controls Necroptosis [191] Tissue factor (TF) mRNA expression levels of TF were elevated in heparanase transfected breast carcinoma cells and transgenic mice over-expressing heparanase. Exogenous addition of heparanase also induced TF expression in human promyelocytic leukemia cells. Heparanase induced TF expression via inducing p38 signaling non-enzymatically Blood coagulation [195] Human melanoma cells deficient in heparanase exhibited increased TF expression Melanoma progression [169] Transforming growth factor (TGF)-β/TGFβ1

Gene expression levels of TGF-β was decreased in the heparanase-silenced tubular cells EMT/Renal fibrosis [178, 189] Induction of acute kidney injury in heparanase-transgenic mice enhanced the expression of TGF-β mRNA. Pre-treatment with heparanase inhibitior PG545 abolished the elevation in TGF-β EMT/Acute kidney injury [179] Heparanase inhibitor suramin down-regulated TGFβ-1 expression in KATO-III gastric cancer cells EMT/Gastric ring cell adenocarcinoma [181] TLR-2

The expression of TLR-2 in macrophages isolated from heparanase deficient mice and in macrophages isolated from mice treated with heparanase-neutralizing antibodies was significantly reduced. Heparanase regulated TLR2 expression through Erk, p38, and JNK signaling pathway Tumor/Macrophage activation and function in tumorigenesis [153] TLR-4

The expression of TLR-4 on macrophages was upregulated in the presence of heparanase but was reduced when cells were treated with heparanase inhibitor SST0001

Acute kidney injury/Regulation of macrophage polarization [182] TNF-α TNF-α expression was reduced in macrophages isolated from heparanase-knockout mice and in macrophages isolated from mice treated with heparanase-neutralizing antibodies. Heparanase regulated TNF-α expression through Erk, p38, and JNK signaling pathway Tumor/Macrophage activation and function in tumorigenesis [153] Heparanase overexpressing transgenic mice expressed more TNF-α during DSS-induced colitis through NF-κB signaling. LPS-treated mouse peritoneal macrophages increased mRNA expression of TNF-α in the presence of recombinant enzymatically active heparanase Ulcerative colitis/Induction of NK-κB activation/Macrophage recruitment and activation [131] Induction of acute kidney injury in heparanase-transgenic mice enhanced the expression of TNF-α mRNA. Pre-treatment with heparanase inhibitior PG545 reduced the expression of TNF-α EMT/Acute kidney injury [179] Human melanoma cells deficient in heparanase exhibited increased TNF-α expression Melanoma progression [169] Heparanase upregulated the expression of TNF-α in PMA-activated U937 macrophage cells. Treatment of cells with heparanase inhibitor SST0001 reduced TNF-α expression Acute kidney injury/M1 macrophage polarization [182] HS fragments generated by heparanase activated TLR4, MyD88, and NF-κB to upregulate TNF-α Inflammation [152] TNF-α mRNA expression was reduced in chemotherapy-treated macrophages isolated from heparanase knockout mice In transwell co-cultures of heparanase-silenced HCC cells and HUVECs, HUVECs displayed lower TNF-α mRNA and protein expression compared to controls Tumor Growth/Induction of pro-inflammatory cytokine expression by chemotherapy-treated macrophage [123] In transwell co-cultures of heparanase-overexpressing HCC cells and HUVECs, HUVECs displayed higher TNF-α mRNA and protein expression after co-culture compared to controls Necroptosis [191] 

In transwell co-cultures of heparanase-silenced HCC cells and HUVECs, HUVECs displayed lower TNFR mRNA and protein expression compared to controls Necroptosis [191] TNFR-associated death domain protein (TRADD)

In transwell co-cultures of heparanase-silenced HCC cells and HUVECs, HUVECs displayed lower TRADD mRNA and protein expression after co-culture compared to controls Necroptosis [191] Vascular cell adhesion molecule 1 (VCAM-1)

Heparanase regulated HAT activity, leading to upregulation of VCAM-1 Inflammation [186] VEGF Heparanase overexpression or exogenous addition led to the enhanced expression of VEGF. Heparanase regulated the expression of VEGF by mediating the activation of SRC family members

Promoting angiogenesis in tumor [175] Heparanase upregulated the expression of VEGF through its HS-degrading activity and stimulating the HAT activity

Tumor phenotype/Upregulation of HAT activity [168] Heparanase regulated the expression of VEGF via activating HIF1 pathway Cervical cancer [177] Addition of recombinant or chemotherapy-generated soluble heparanase elevated the expression of VEGF in myeloma Tumor progression [76] Heparanase overexpression in melanoma cell lines increased the expression of VEGF mRNA. Downregulation of heparanase via anti-heparanase siRNA transfection resulted in a significant reduction of VEGF mRNA expression in melanoma cell lines Melanoma progression [92] VEGF-A Reduced VEGF-A expression was observed in macrophages isolated from heparanase-knockout mice and in macrophages isolated from mice treated with heparanase-neutralizing antibodies Tumor/Macrophage activation and function in tumorigenesis [153] Heparanase regulated HAT activity, leading to upregulation of VEGF-A Atherosclerosis/Glucose Metabolism [186] VEGF-C Overexpression of heparanase increased VEGF-C mRNA expression

Pancreatic cancer/Facilitating cell invasion [185] Vimentin KATO-III gastric cancer cells exhibited reduced Vimentin expression after treating with heparanase inhibitor suramin EMT/Gastric ring cell adenocarcinoma [181] Heparanase-overexpressing mice displayed remarkable upregulation of vimentin during acute kidney injury. Pre-treatment with heparanase inhibition abolished the increased expression of vimentin in heparanase-overexpressing mice.

EMT/Acute kidney injury [179] Heparanase-silenced cells reduced vimentin expression EMT/Acute kidney injury [189] WDR5 Upon paclitaxel treatment, WDR5 expression was induced in wild type but not heparanase-knockout macrophages, but could be rescued with exogenous heparanase Heparanase was required for the expression of WDR5 in macrophages

Tumor Growth/Induction of pro-inflammatory cytokine expression by chemotherapy-treated macrophage [123] Proteins bFGF bFGF protein expression was decreased in heparanase knockdown cell and increased in heparanase overexpressing cells via activating HIF1 pathway Cervical cancer [177] BLC BLC expression was reduced in macrophages isolated from heparanase-knockout mice Tumor/Macrophage activation and function in tumorigenesis [153] Caspase-1

Heparanase-silenced and heparanase inhibitor SST0001-treated cells reduced caspase-1 expression Acute kidney injury/M1 macrophage polarization Table 3 . Cont.

Cox-2 Heparanase upregulated the mRNA expression of Cox-2 in cancer cells Tumor/Promoting angiogenesis [187] CXCL1 (KC) Administration of heparanase increased CXCL1 level in mouse serum

Thoracoabdominal aortic aneurysm/Systemic Inflammation [196] CXCL1 expression was reduced in macrophages isolated from heparanase-knockout mice Tumor/Macrophage activation and function in tumorigenesis [153] Heparanase-stimulated colon cancer cells released CXCL1 Colon cancer [183] FGF21 Heparanase-overexpressing mice had higher FGF21 expression in the blood plasma compared to wild type mice Diabetes/Glucose homeostasis [197] Fibrinogen High dose heparanase-derived peptides induced a decrease in the level of fibrinogen Coagulopathy and wound healing/Activation of the coagulation system [198] Fibronectin Protein expression of fibronectin was increased in heparanase-overexpressing mice with acute kidney injury but decreased when pre-treating the mice with heparanase inhibitor PG545

EMT/Acute kidney injury [179] FXa Heparanase-derived peptides enhanced the level of FXa probable through interacting with TF Coagulopathy and wound healing/Activation of the coagulation system [198] Hepatocyte growth factor (HGF) [197] IL-1 Addition or overexpression of heparanase upregulated the expression of IL-1

Atherosclerosis/Macrophage activation [199] IL-1β

Administration of heparanase increased IL-1β level in mouse serum

Thoracoabdominal aortic aneurysm/Systemic Inflammation [196] Heparanase upregulated the expression of IL-1β in macrophages. Treatment of cells with heparanase inhibitor SST0001 reduced IL-1β expression Acute kidney injury/M1 macrophage polarization [182] Heparanase via its enzymatic activity upregulated IL-1β through TLR4 signaling Inflammation [152] IL-4

Allergic inflammation/Recruitment of eosinophils and mucus-secreting airway epithelial cells [51] Administration of heparanase upregulated the expression of IL-4 in mouse immune cells Autoimmune encephalitis/inhibition of inflammation [200] IL-5 IL-5 expression was reduced in lung cells isolated from heparanase deficient mice with HDM-induced allergic inflammation

Allergic inflammation/Recruitment of eosinophils and mucus-secreting airway epithelial cells [51] IL-6

Administration of heparanase increased IL-6 level in mouse serum

Thoracoabdominal aortic aneurysm/Systemic Inflammation [196] Heparanase via its enzymatic activity upregulated IL-6 through TLR4 signaling Inflammation [152] Administration of heparanase upregulated the expression of IL-6 in mouse immune cells Autoimmune encephalitis/Inhibition of inflammation [200] Addition of heparanase enhanced the expression of IL-6 in fatty acid-stimulated macrophages

Obesity-associated breast cancer [103] 

Heparanase enhanced IL-8 expression Colon cancer [183] Heparanase upregulated IL-8 expression via its enzymatic activity Inflammation [152] IL-10

Administration of heparanase increased IL-10 level in mouse serum

Thoracoabdominal aortic aneurysm/Systemic Inflammation [196] Heparanase upregulated IL-10 expression via its enzymatic activity Inflammation [152] Administration of heparanase upregulated the expression of IL-10 in mouse immune cells

Autoimmune encephalitis/Inhibition of inflammation [200] IL-12

Administration of heparanase downregulated the expression of IL-12 in mouse immune cells

Autoimmune encephalitis/Inhibition of inflammation [200] IL-17A

Silencing of heparanase resulted in a significant decrease in protein expression of IL-17A in human cervical cancer cell lines HeLa and SiHa

Promoting tumor angiogenesis, cell proliferation, and invasion in cervical cancer [84] iNOS Heparanase upregulated the expression of iNOS in macrophages. Treatment of cells with the heparanase inhibitor SST0001 reduced iNOS expression Acute kidney injury/M1 macrophage polarization [182] MCP-1

Addition or overexpression of heparanase upregulated the expression of MCP-1

Atherosclerosis/Macrophage activation Thoracoabdominal aortic aneurysm/Systemic [199] Administration of heparanase increased MCP-1 level in mouse serum Inflammation [196] Heparanase-stimulated colon cancer cells released MCP-1 Colon cancer [183] Heparanase upregulated MCP-1 via TLR4 signaling Inflammation [152] Obese heparanase knockout mice showed less MCP-1 expression compared to obese wild type mice Obesity-associated breast cancer progression [103] MIP-2 (CXCL2) MIP-2 expression was reduced in macrophages isolated from heparanase-knockout mice Tumor/Macrophage activation and function in tumorigenesis [153] MMP-9 Addition or overexpression of heparanase upregulated the expression of MMP-9

Atherosclerosis/Macrophage activation [199] NF-κB (p65)

Knockdown of heparanase led to increased expression of nuclear NF-κB in melanoma cell lines

Melanoma progression [169] P21 Heparanase downregulated p21 in colon carcinoma cells through its enzymatic activity and involved TLRs and NF-κB signaling Colon carcinoma/Modification of cell cycle [194] α-SMA Protein expression of α-SMA was increased in heparanase-overexpressing mice with acute kidney injury but decreased when pre-treating the mice with heparanase inhibitor PG545

EMT/Acute kidney injury [179] TLR2 Heparanase knockout cells expressed less TLR2 protein

Tumor/Macrophage activation and function in tumorigenesis [153] TNF-α TNF-α expression was reduced in macrophages isolated from heparanase-knockout mice Tumor/Macrophage activation and function in tumorigenesis [153] Increased expression of TNF-α in heparanase overexpressing transgenic mice with DSS-induced colitis Ulcerative colitis/Induction of NK-κB activation [131] Addition or overexpression of heparanase increased the expression of TNF-α Atherosclerosis/Macrophage activation [199] Heparanase upregulated TNF-α via TLR4 signaling. Heparanase deficiency reduced the expression of TNF-α in macrophages Inflammation Obesity-associated breast cancer progression [103, 152] Vimentin Protein expression of vimentin was increased in heparanase-overexpressing mice with acute kidney injury but decreased when pre-treating the mice with heparanase inhibitor PG545

EMT/Acute kidney injury [179] EGR, early growth response; HCC, hepatocellular carcinoma; HIF, hypoxia inducible factor.

A recent study has also used transcriptomics to show that heparanase negatively regulates a number of genes involved in defense responses to viruses [201] . Following infection with HSV-1, differences in the transcriptomic landscape of wild-type and heparanase knock-out cells were observed. Heparanase knock-out cells were enriched in genes related to an antiviral and innate immune response (such as Interferon regulatory factors), while infected wild-type cells were enriched for genes involved in gene expression and processing, and hence viral replication. This suggests heparanase dampens the host's antiviral defense response while simultaneously enhancing the virulence of HSV-1. As described above, heparanase is upregulated during infection with several types of viruses. Thus, heparanase upregulation and downstream gene regulation are likely a mechanism of viral pathogenicity. Genes involved in response to viral infection were not the only genes found to be modulated by heparanase in this study. Heparanase was also found to positively regulate genes involved in blood vessel development, cell-cell adhesion, inflammatory response, ECM reorganization, and leukocyte chemotaxis, and negatively regulate genes in pathways related to an antiviral defense response, regulation of viral genome replication, antigen processing and presentation, regulation of nuclease activity, and activation of an immune response [201] . Similarly, transcriptomic analysis has also been performed on heparanase-silenced melanoma cells [154] . This study found heparanase to negatively regulate genes relating to many pathways, including signaling, communication, response to cytokines, protein phosphorylation, cell adhesion, inflammatory response, and apoptotic processes. These two studies highlight the broad regulatory role heparanase plays in several cellular pathways.

As mentioned above, heparanase can directly and indirectly alter the expression of numerous genes. Since gene expression does not always correlate with protein expression, validating that expression changes occur at the protein level is important, and for heparanase-regulated genes, this is often the case. In addition to regulating EMT-related genes at the transcriptional level as mentioned above, heparanase also contributes to the expression of these genes at the protein level. This was demonstrated by the increased expression of α-SMA, fibronectin, and vimentin in transgenic mice over-expressing heparanase at both the mRNA and protein level [179] . There are many other examples of specific protein expression shown to be regulated by heparanase at the transcriptional level. Depletion of heparanase or employing heparanase inhibitors in either mouse models or cell lines resulted in the reduced expression of growth factors, cytokines, and other proteins such as bFGF, VEGF, HGF [76, 176, 177] , CXCL2, TLR2 [153] , and IL-17A [84] . These proteins play a key role in the progression of different tumor types. In the presence of heparanase, pro-inflammatory cytokines IL-6, IL-10, MCP-1, and TNF-α are elevated at the mRNA and protein level in both human and mouse immune cells in vivo. These cytokines are implicated in autoimmune diseases such as atherosclerosis and autoimmune encephalitis [199, 200] . Heparanase, by modifying the levels of these cytokines, is therefore also involved in mediating these diseases. We have summarised the list of proteins and the processes and diseases involved that are influenced by heparanase in Table 3 .

Other reports have also shown that the levels of specific proteins are altered as a result of heparanase expression, e.g., IL-4 [51, 200] , CXCL1 [183] , and fibrinogen [198] , however, mRNA expression levels have not been determined for these proteins. Whilst it is still unknown how heparanase regulates the expression of these proteins, based on the other examples listed above, it can be predicted that heparanase modulates expression of these proteins by altering the expression and secretion of signaling molecules (e.g., cytokines) that ultimately alter gene expression and consequently protein levels.

Protein phosphorylation is an important biological process whereby many receptors and enzymes are activated or deactivated by phosphorylation or dephosphorylation, respectively. Several studies have demonstrated that heparanase can indirectly regulate protein phosphorylation ( Figure 2 ). Akt, a member of AGC kinases, is associated with cellular signaling pathways related to cell proliferation, cell growth, cell survival, and metabolism [202] . Heparanase has been suggested to induce Akt phosphorylation in endothelial cells, macrophages, fibroblasts, and various tumor-derived cells [76, 199, [203] [204] [205] . It seems that Akt phosphorylation requires enzymatic activity of heparanase since blocking heparanase activity reduced levels of Akt phosphorylation [76, 79] . Heparanase is also involved in the phosphorylation of ERK, another kinase involved in numerous cellular functions such as proliferation, survival, apoptosis, motility, transcription, metabolism, and differentiation [206] . Again, heparanase has been shown to enhance ERK phosphorylation levels in macrophages and myeloma cell lines through its enzymatic activity [76, 153] . Increased ERK phosphorylation is also observed in neural stem and progenitor cells overexpressing heparanase during cell differentiation [207] . Heparanase is also implicated in mediating EGFR phosphorylation, where EGFR signaling is a key regulator of cell growth, cell migration, proliferation, and cell survival [208, 209] . It is reported that overexpression of heparanase also stimulates the phosphorylation of EGFR in different tumor cell lines [205, 209] and inhibiting heparanase expression results in the reduction of EGFR phosphorylation [79] .

In addition to Akt, ERK, and EGFR, heparanase is suggested to mediate the phosphorylation of Signal Transducer and Activator Of Transcription (STAT) proteins including STAT3 and STAT5b. In a tumor setting, heparanase enhances the phosphorylation of STAT3 and STAT5b. Notably, increased cytoplasmic pSTAT3 is associated with larger tumor size and reduced patient survival in a cohort of patients with head and neck squamous cell carcinoma [205] . The increased STAT3 phosphorylation is eliminated in pancreatic cells isolated from mice treated with a heparanase inhibitor, which further strengthens the involvement of heparanase in STAT3 phosphorylation. Additionally, heparanase regulates the levels of phosphorylated Focal-adhesion kinase (FAK), SRC, and paxillin, adhesion molecules required for tumor cell cluster formation, the process that facilitates cancer metastasis [197] . In a mouse model of acute pancreatitis, heparanase overexpression resulted in elevated levels of IκB phosphorylation and correlated with increased TNF-α expression. A similar observation was noted for IL-6 and STAT3 phosphorylation which indicates the association of heparanase with the activation of key signaling pathways related to acute pancreatitis [127] . Furthermore, heparanase can also stimulate the phosphorylation of p65 NF-κB [131] , p38, and JNK, which lead to the activation of NF-κB and the induction of cytokine expression in macrophages [210] . Proteins of which their phosphorylation state is regulated by heparanase are listed in Table 4 . High expression of heparanase in myeloma cell lines led to increased AKT phosphorylation. This was blocked by treating cells with heparanase inhibitor SST0001

Tumor progression [76] Epidermal growth factor receptor (EGFR)

Inhibition of heparanase reduced EGFR phosphorylation Breast Cancer Brain Metastasis [79] Heparanase enhanced the phosphorylation level of EGFR in carcinoma cells

Tumor progression [205] Heparanase released HS via shedding syndecan-1 which induced EGFR phosphorylation

Colorectal cancer [151] ERK The level of phosphorylated ERK was increased in heparanase overexpressing neural stem and progenitor cells during differentiation Promoting Embryonic stem cell differentiation into Oligodendrocytes [207] Addition of exogenous heparanase induced ERK phosphorylation in macrophages

Inducing cytokine expression in macrophage [153] High expression of heparanase in myeloma cell lines led to increased ERK phosphorylation. The increased phosphorylation of ERK was blocked in cells treated with heparanase inhibitor SST0001

Tumor progression [76] Focal-adhesion kinase (FAK)

The phosphorylation of FAK was elevated in heparanase-overexpressing breast cancer cell lines. Likewise, the phosphorylation of FAK was decreased in heparanase-knockout cell lines. Heparanase promoted cell cluster formation by regulating FAK-Src-paxillin pathway Promotion of cell cluster formation/Tumor metastasis [197] IκBα/IκB

Heparanase enhanced phosphorylation of IκBα in heparanase overexpressing mice suffering colitis-associated tumors Ulcerative colitis/Induction of NK-κB activation [131] IκB phosphorylation was decreased in pancreas tissues of heparanase-overexpressing mice treated with heparanase inhibitor PG545

Acute pancreatitis [127] JNK Addition of exogenous heparanase induced JNK phosphorylation in macrophages

Inducing cytokine expression in macrophage [153] JNK phosphorylation was decreased in macrophages isolated from heparanase knockout mice

Tumor Growth/Induction of pro-inflammatory cytokine expression by chemotherapy-treated macrophage [123] MEK Heparanase induced MEK phosphorylation via releasing HS of syndecan-1

Colorectal cancer [151] Inducing cytokine expression in macrophage [153] Heparanase-overexpressing cells induced p38 phosphorylation Promoting tumor angiogenesis [175] p65 NF-κB Increased nuclear p65 phosphorylation was detected in heparanase overexpressing mice treated with DSS to induce colitis-associated tumors

Ulcerative colitis/Induction of NK-κB activation [131] Paxillin

The phosphorylation of paxillin was elevated in heparanase-overexpressing breast cancer cell lines. In contrast, the phosphorylation of paxillin was decreased in heparanase-knockout cell lines. Heparanase promoted cell cluster formation by regulating FAK-Src-paxillin pathway Promotion of cell cluster formation/Tumor metastasis [197] SRC The phosphorylation of SRC was increased in heparanase-overexpressing breast cancer cell lines. In contrast, the level of SRC phosphorylation was decreased in heparanase-knockout cell lines. Heparanase promoted cell cluster formation by regulating FAK-Src-paxillin pathway Promotion of cell cluster formation/Tumor metastasis [197] Inactive heparanase stimulated SRC phosphorylation Tumor angiogenesis [175] Heparanase enhanced the phosphorylation level of SRC in carcinoma cells

Tumor progression [205] Signal Transducer and Activator of Transcription (STAT)

Heparanase increased nuclear STAT phosphorylation Tumor progression [205] STAT3 Higher number of cells positive for nuclear-localized pSTAT3 were observed in heparanase-overexpressing transgenic mice

Modulator of tumor-promoting chronic inflammation [131] Heparanase enhanced STAT3 phosphorylation Tumor progression [205] Reduced STAT3 phosphorylation was observed in obese heparanase knockout mice Obesity-associated breast cancer progression [103] STAT5b

Heparanase enhanced STAT5b phosphorylation Tumor progression [205] VCAM-1, vascular cell adhesion molecule 1; SERPINE1, plasminogen activator inhibitor type 1; VEGFA, vascular endothelial growth factor A; FXa, activated factor X; TF, tissue factor; TGF, transforming growth factor; PDK2, pyruvate dehydrogenase kinase 2; HIF1, hypoxia inducible factor.

Heparanase is widely considered a key player in several diseases including cancer, heart disease, and viral infection. Thus, the clinical inhibition of heparanase provides a potential method to treat these diseases. Understanding its intricate role in these diseases is key to designing effective treatments. This review highlighted the many molecular regulators of heparanase in different disease contexts. The array of different molecules, pathways and settings that regulate heparanase expression illustrate the diversity of heparanase expression and functions during disease. We also discuss how heparanase itself can regulate the expression of many downstream genes as well as the phosphorylation of proteins, and thus regulate the activity of several pathways, making heparanase a master regulator of several cellular processes in physiology and disease. Furthering our understanding of how heparanase itself is regulated, as well as the greater heparanase regulatory network, will help to develop treatments for heparanase-mediated diseases. 

Remodelling the extracellular matrix in development and disease

Heparan sulfate proteoglycans

Functions of Cell Surface Heparan Sulfate Proteoglycans

Heparan sulfate in the nucleus and its control of cellular functions

A systems biology approach for the investigation of the heparin/heparan sulfate interactome

Fibroblast growth factors share binding sites in heparan sulphate

Binding of fibronectin and its proteolytic fragments to glycosaminoglycans. Exposure of cryptic glycosaminoglycan-binding domains upon limited proteolysis

Binding of heparin fractions and other polysulfated polysaccharides to plasma fibronectin: Effects of molecular size and degree of sulfation of polysaccharides

The dependence of chemokine-glycosaminoglycan interactions on chemokine oligomerization

The involvement of heparan sulfate (HS) in FGF1/HS/FGFR1 signaling complex

Heparan Sulfate in trans Potentiates VEGFR-Mediated Angiogenesis

Heparan sulphate as a regulator of leukocyte recruitment in inflammation

The first draft of the endostatin interaction network

Neuroprotective secreted amyloid precursor protein acts by disrupting amyloid precursor protein dimers

Glycosaminoglycan Binding Properties of Annexin IV, V, and VI

High and low affinity binding sites for basic fibroblast growth factor on cultured cells: Absence of a role for low affinity binding in the stimulation of plasminogen activator production by bovine capillary endothelial cells

Basic Fibroblast Growth Factor Binds to Subendothelial Extracellular Matrix and Is Released by Heparitinase and Heparin-like Molecules

Requirement of heparan sulfate for bFGF-mediated fibroblast growth and myoblast differentiation

Binding of two growth factor families to separate domains of the proteoglycan betaglycan

Correlation between cell substrate attachment in vitro and cell surface heparan sulfate affinity for fibronectin and collagen

Binding of heparan sulfate to type V collagen. A mechanism of cell-substrate adhesion

Structural requirements for heparin/heparan sulfate binding to type V collagen

Basement-membrane heparan sulfate proteoglycan binds to laminin by its heparan sulfate chains and to nidogen by sites in the protein core

Interference with Glycosaminoglycan-Chemokine Interactions with a Probe to Alter Leukocyte Recruitment and Inflammation In Vivo

The IP-10 chemokine binds to a specific cell surface heparan sulfate site shared with platelet factor 4 and inhibits endothelial cell proliferation

Solution structure of CXCL13 and heparan sulfate binding show that GAG binding site and cellular signalling rely on distinct domains

Cell surface glypicans are low-affinity endostatin receptors

Binding of endostatin to endothelial heparan sulphate shows a differential requirement for specific sulphates

Binding of Heparin/Heparan Sulfate to Fibroblast Growth Factor Receptor 4

Interaction of hepatocyte growth factor with heparan sulfate. Elucidation of the major heparan sulfate structural determinants

Histidine-rich glycoprotein binds to cell-surface heparan sulfate via its N-terminal domain following Zn2+ chelation

Heparan sulfate is essential for high mobility group protein 1 (HMGB1) signaling by the receptor for advanced glycation end products (RAGE)

Reducing Macrophage Proteoglycan Sulfation Increases Atherosclerosis and Obesity through Enhanced Type I Interferon Signaling

Differential binding of chemokines to glycosaminoglycan subpopulations

Calcium-dependent heparin-like ligands for L-selectin in nonlymphoid endothelial cells

Differential interactions of heparin and heparan sulfate glycosaminoglycans with the selectins: Implications for the use of unfractionated and low molecular weight heparins as therapeutic agents

Lysine 58 and histidine 66 at the C-terminal α-helix of monocyte chemoattractant protein-1 are essential for glycosaminoglycan binding

Cell surface syndecancontributes to binding and function of macrophage migration inhibitory factor (MIF) on epithelial tumor cells

Characterization of the binding site on heparan sulfate for macrophage inflammatory protein 1α

Characterization of the heparin/heparan sulfate binding site of the natural cytotoxicity receptor NKp46

Defective N-sulfation of heparan sulfate proteoglycans limits PDGF-BB binding and pericyte recruitment in vascular development

Alternative splicing determines the binding of platelet-derived growth factor (PDGF-AA) to glycosaminoglycans

Stable RAGE-Heparan Sulfate Complexes Are Essential for Signal Transduction

Oligomerized, filamentous surface presentation of RANTES/CCL5 on vascular endothelial cells

Heparan Sulfate Proteoglycans Are Ligands for Receptor Protein Tyrosine Phosphatase

Proteoglycans on bone marrow endothelial cells bind and present SDF-1 towards hematopoietic progenitor cells

Dual regulation of vascular endothelial growth factor bioavailability by genetic and proteolytic mechanisms

1H NMR spectroscopic studies establish that heparanase is a retaining glycosidase

Heparanase accelerates wound angiogenesis and wound healing in mouse and rat models

NK cell heparanase controls tumor invasion and immune surveillance

Mice deficient in heparanase exhibit impaired dendritic cell migration and reduced airway inflammation

Inhibition of T lymphocyte heparanase by heparin prevents T cell migration and T cell-mediated immunity

Cell Surface Localization of Heparanase on Macrophages Regulates Degradation of Extracellular Matrix Heparan Sulfate

Role of promoter methylation in regulation of the mammalian heparanase gene

DNA Methylation of Heparanase Promoter Influences Its Expression and Associated with the Progression of Human Breast Cancer

Inverse correlation between HPSE gene single nucleotide polymorphisms and heparanase expression: Possibility of multiple levels of heparanase regulation

Association of heparanase gene (HPSE) single nucleotide polymorphisms with hematological malignancies

Cloning of mammalian heparanase, an important enzyme in tumor invasion and metastasis

Roles in cell survival, extracellular matrix remodelling and the development of kidney disease

Tissue-based map of the human proteome

Regulation of mouse Heparanase gene expression in T lymphocytes and tumor cells

Expression of the heparan sulfate-degrading enzyme heparanase is induced in infiltrating CD4 + T cells in experimental autoimmune encephalomyelitis and regulated at the level of transcription by early growth response gene

Modification of heparanase gene expression in response to conditioning and LPS treatment: Strong correlation to rs4693608 SNP

Heparanase and the hallmarks of cancer

Human telomerase reverse transcriptase (hTERT) promotes gastric cancer invasion through cooperating with c-Myc to upregulate heparanase expression

Regulation of Inducible Heparanase Gene Transcription in Activated T Cells by Early Growth Response 1

Early growth response gene 1 (EGR1) regulates heparanase gene transcription in tumor cells

Heparanase is essential for the development of diabetic nephropathy in mice

Trans-activation of heparanase promoter by ETS transcription factors

Cloning and characterization of the human heparanase-1 (HPR1) gene promoter. Role of GA-binding protein and Sp1 in regulating HPR1 basal promoter activity

Induction of Heparanase-1 Expression by Mutant B-Raf Kinase: Role of GA Binding Protein in Heparanase-1 Promoter Activation

Tumor metastasis and the reciprocal regulation of prometastatic and antimetastatic factors by nuclear factor κB

Heparan sulfate domains on cultured activated glomerular endothelial cells mediate leukocyte trafficking

Hypoxia activates heparanase expression in an NF-kappaB dependent manner

Heparanase is a host enzyme required for herpes simplex virus-1 release from cells

Chemotherapy induces expression and release of heparanase leading to changes associated with an aggressive tumor phenotype

Tumor suppressor p53 regulates heparanase gene expression

Vivo Melanoma Metastasis by Altering Matrix-Effectors and Invadopodia Markers. Cells 2021

MicroRNA-1258 suppresses breast cancer brain metastasis by targeting heparanase

MicroRNA-1252-5p associated with extracellular vesicles enhances bortezomib sensitivity in multiple myeloma cells by targeting heparanase

Role of endothelial heparanase in delayed-type hypersensitivity

Inflammatory Cytokines and Fatty Acids Regulate Endothelial Cell Heparanase Expression

Induction of heparanase via IL-10 correlates with a high infiltration of CD163+ M2-type tumor-associated macrophages in inflammatory breast carcinomas

Interleukin-17A and heparanase promote angiogenesis and cell proliferation and invasion in cervical cancer

Systemic Monocyte Chemotactic Protein-1 Inhibition Modifies Renal Macrophages and Restores Glomerular Endothelial Glycocalyx and Barrier Function in Diabetic Nephropathy

Cytotoxic T lymphocyte epitopes from human heparanase can elicit a potent anti-tumor immune response in mice

The pulmonary endothelial glycocalyx regulates neutrophil adhesion and lung injury during experimental sepsis

Heparanase and macrophage interplay in the onset of liver fibrosis

Erythromycin and clarithromycin modulation of growth factor-induced expression of heparanase mRNA on human lung cancer cells in vitro

Hepatocyte growth factor (HGF) upregulates heparanase expression via the PI3K/Akt/NF-κB signaling pathway for gastric cancer metastasis

FGF23 is elevated in multiple myeloma and increases heparanase expression by tumor cells

Mutual enhancement between heparanase and vascular endothelial growth factor: A novel mechanism for melanoma progression

Heparanase of murine effector lymphocytes and neutrophils is not required for their diapedesis into sites of inflammation

Heparanase modulation by Wingless/INT (Wnt)

Advanced glycation end-products induce heparanase expression in endothelial cells by the receptor for advanced glycation end products and through activation of the FOXO4 transcription factor

Activated T lymphocytes produce a matrix-degrading heparan sulphate endoglycosidase

Soluble antigen induces T lymphocytes to secrete an endoglycosidase that degrades the heparan sulfate moiety of subendothelial extracellular matrix

Expression of heparanase by platelets and circulating cells of the immune system: Possible involvement in diapedesis and extravasation

Endothelial Nitric Oxide Synthase Prevents Heparanase Induction and the Development of Proteinuria

Regulation of Heparanase Gene Expression by Estrogen in Breast Cancer

Increased ETV4 expression correlates with estrogen-enhanced proliferation and invasiveness of cholangiocarcinoma cells

Tamoxifen induces heparanase expression in estrogen receptor-Positive breast cancer

Heparanase accelerates obesity-associated breast cancer progression

Glucose-induced endothelial heparanase secretion requires cortical and stress actin reorganization

Retinal heparanase expression in streptozotocin-induced diabetic rats

Reactive oxygen species mediate high glucose-induced heparanase-1 production and heparan sulphate proteoglycan degradation in human and rat endothelial cells: A potential role in the pathogenesis of atherosclerosis

Vlodavsky, I. Production of heparanase by normal and neoplastic murine B-lymphocytes

Dialysis-related transcriptomic profiling: The pivotal role of heparanase

Induction of Glomerular Heparanase Expression in Rats with Adriamycin Nephropathy Is Regulated by Reactive Oxygen Species and the Renin-Angiotensin System

Regulation of glomerular heparanase expression by aldosterone, angiotensin II and reactive oxygen species

Vitamin D attenuates proteinuria by inhibition of heparanase expression in the podocyte

Periodontal pathogens Porphyromonas gingivalis and Fusobacterium nucleatum promote tumor progression in an oralspecific chemical carcinogenesis model

Helicobacter pylori promotes invasion and metastasis of gastric cancer by enhancing heparanase expression

Murine ocular heparanase expression before and during infection with Pseudomonas aeruginosa

Vlodavsky, I. Involvement of Heparanase in Empyema: Implication for Novel Therapeutic Approaches

Increased Plasma Heparanase Activity in COVID-19 Patients. Front

Injury to the Endothelial Glycocalyx in Critically Ill Patients with COVID-19

Dengue Virus NS1 Disrupts the Endothelial Glycocalyx, Leading to Hyperpermeability

Macrophage migration inhibitory factor is critical for dengue NS1-induced endothelial glycocalyx degradation and hyperpermeability

Viral Activation of Heparanase Drives Pathogenesis of Herpes Simplex Virus-1. Cell Rep

Molecular characterization, expression profiles of the porcine SDC2 and HSPG2 genes and their association with hematologic parameters

Heparanase Upregulation Contributes to Porcine Reproductive and Respiratory Syndrome Virus Release

Heparanase and chemotherapy synergize to drive macrophage activation and enhance tumor growth

Comparative analysis of the ability of leucocytes, endothelial cells and platelets to degrade the subendothelial basement membrane: Evidence for cytokine dependence and detection of a novel sulfatase

Activation of heparanase by ultraviolet B irradiation leads to functional loss of basement membrane at the dermal-epidermal junction in human skin

Identification of proteins indicating radiation-induced Hepatic Toxicity in cirrhotic rats

The Role of Heparanase in the Pathogenesis of Acute Pancreatitis: A Potential Therapeutic Target

Role of p53 in cell death and human cancers

MicroRNA regulation of tumorigenesis, cancer progression and interpatient heterogeneity: Towards clinical use

The Functions of Heparanase in Human Diseases. Mini Rev

Heparanase powers a chronic inflammatory circuit that promotes colitis-associated tumorigenesis in mice

TNF-α induces the transcription factor Egr-1, pro-inflammatory cytokines and cell proliferation in human skin fibroblasts and synovial lining cells

TNF-α induces early growth response gene-1 expression via ERK1/2 activation in endothelial cells

Hormone-related risk factors for breast cancer in women under age 50 years by estrogen and progesterone receptor status: Results from a case-control and a case-case comparison

ROS signalling in the biology of cancer

Emerging Roles of Heparanase in Viral Pathogenesis

Heparanase, cell signaling, and viral infections

Efficient infection of cells in culture by type O foot-and-mouth disease virus requires binding to cell surface heparan sulfate

Iduronic acid-containing glycosaminoglycans on target cells are required for efficient respiratory syncytial virus infection

Human Papillomavirus Infection Requires Cell Surface Heparan Sulfate

Cytokine Induction by the Hepatitis B Virus Capsid in Macrophages Is Facilitated by Membrane Heparan Sulfate and Involves TLR2

Heparan sulfate as a receptor for poxvirus infections and as a target for antiviral agents

Heparanase expression in nasopharyngeal carcinoma inversely correlates with patient survival

The prognostic significance of heparanase expression in metastatic melanoma

Salivary Heparanase Level Is a Potential Biomarker to Diagnose and Prognose the Malignant Salivary Gland Tumor

The Role of Heparan Sulfate Proteoglycans in Bacterial Infections

Surface proteoglycans as mediators in bacterial pathogens infections

Heparanase-enhanced Shedding of Syndecan-1 and Its Role in Driving Disease Pathogenesis and Progression

Heparanase mediates a novel mechanism in lapatinib-resistant brain metastatic breast cancer

Targeting heparanase overcomes chemoresistance and diminishes relapse in myeloma

Shed Syndecan-1 is involved in chemotherapy resistance via the EGFR pathway in colorectal cancer

Soluble Heparan Sulfate Fragments Generated by Heparanase Trigger the Release of Pro-Inflammatory Cytokines through TLR-4

Heparanase is required for activation and function of macrophages

Transcriptomic analysis reveals cell apoptotic signature modified by heparanase in melanoma cells

Site-directed mutagenesis, proteolytic cleavage, and activation of human proheparanase

Vlodavsky, I. Cathepsin L is responsible for processing and activation of proheparanase through multiple cleavages of a linker segment

Eosinophil major basic protein: First identified natural heparanase-inhibiting protein

Heparanase: A target for drug discovery in cancer and inflammation

Heparanase and a synthetic peptide of heparan sulfate-interacting protein recognize common sites on cell surface and extracellular matrix heparan sulfate

Heparanase 2 Interacts with Heparan Sulfate with High Affinity and Inhibits Heparanase Activity

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

Structure, Biological Functions, and Inhibition by Heparin-Derived Mimetics of Heparan Sulfate

Non-Anticoagulant Heparins as Heparanase Inhibitors

Heparanase in glomerular diseases

A Challenging Cancer Drug Target

Human heparanase. Purification, characterization, cloning, and expression

Heparanase Regulates Levels of Syndecan-1 in the Nucleus

Heparanase-mediated Loss of Nuclear Syndecan-1 Enhances Histone Acetyltransferase (HAT) Activity to Promote Expression of Genes That Drive an Aggressive Tumor Phenotype

Nuclear heparanase-1 activity suppresses melanoma progression via its DNA-binding affinity

Human heparanase nuclear localization and enzymatic activity

Heparanase expression and localization in different types of human lung cancer

The endoglycosidase heparanase enters the nucleus of T lymphocytes and modulates H3 methylation at actively transcribed genes via the interplay with key chromatin modifying enzymes

Heparanase Localization and Expression by Head and Neck Cancer: Correlation with Tumor Progression and Patient Survival

Heparanase is overexpressed in lung cancer and correlates inversely with patient survival

Heparanase induces vascular endothelial growth factor expression: Correlation with p38 phosphorylation levels and Src activation

Heparanase plays a dual role in driving hepatocyte growth factor (HGF) signaling by enhancing HGF expression and activity

Heparanase promotes radiation resistance of cervical cancer by upregulating hypoxia inducible factor 1

Heparanase is a key player in renal fibrosis by regulating TGF-β expression and activity

Involvement of heparanase in the pathogenesis of acute kidney injury: Nephroprotective effect of PG545

Effects of unfractionated heparin and rivaroxaban on the expression of heparanase and fibroblast growth factor 2 in human osteoblasts

The close relationship between heparanase and epithelial mesenchymal transition in gastric signet-ring cell adenocarcinoma

Heparanase regulates the M1 polarization of renal macrophages and their crosstalk with renal epithelial tubular cells after ischemia/reperfusion injury

Heparanase augments inflammatory chemokine production from colorectal carcinoma cell lines

Heparanase stimulation of protease expression implicates it as a master regulator of the aggressive tumor phenotype in myeloma

Heparanase regulates in vitro VEGF-C expression and its clinical significance to pancreatic ductal cell adenocarcinoma

Fatty Acid-Induced Nuclear Translocation of Heparanase Uncouples Glucose Metabolism in Endothelial Cells

Heparanase Is Involved in Angiogenesis in Esophageal Cancer through Induction of Cyclooxygenase-2

Heparanase Modulation of Early Growth Response Gene Expression

Inhibition of heparanase protects against chronic kidney dysfunction following ischemia/reperfusion injury

Heparanase released from mesenchymal stem cells activates integrin beta1/HIF-2alpha/Flk-1 signaling and promotes endothelial cell migration and angiogenesis

Heparanase induces necroptosis of microvascular endothelial cells to promote the metastasis of hepatocellular carcinoma

Heparanase Promotes Syndecan-1 Expression to Mediate Fibrillar Collagen and Mammographic Density in Human Breast Tissue Cultured ex vivo. Front

Heparanase and Syndecan-1 Interplay Orchestrates Fibroblast Growth Factor-2-induced Epithelial-Mesenchymal Transition in Renal Tubular Cells

The Heparanase Inhibitor PG545 Attenuates Colon Cancer Initiation and Growth, Associating with Increased p21 Expression

Heparanase induces tissue factor expression in vascular endothelial and cancer cells

The ß-D-endoglucuronidase heparanase is a danger molecule that drives systemic inflammation and correlates with clinical course after open and endovascular thoracoabdominal aortic aneurysm repair: Lessons learnt from mice and men. Front

CTC clusters induced by heparanase enhance breast cancer metastasis

Involvement of the heparanase procoagulant domain in bleeding and wound healing

Macrophage activation by heparanase is mediated by TLR-2 and TLR-4 and associates with plaque progression

Vlodavsky, I. Heparanase upregulates Th2 cytokines, ameliorating experimental autoimmune encephalitis

Disruption of innate defense responses by endoglycosidase HPSE promotes cell survival

The critical role of Akt in cardiovascular function

Heparanase Induces Endothelial Cell Migration via Protein Kinase B/Akt Activation

Heparanase induces Akt phosphorylation via a lipid raft receptor

Heparanase Induces Signal Transducer and Activator of Transcription (STAT) Protein Phosphorylation

The regulation of extracellular signal-regulated kinase (ERK) in mammalian cells

Heparanase confers a growth advantage to differentiating murine embryonic stem cells, and enhances oligodendrocyte formation

A comprehensive pathway map of epidermal growth factor receptor signaling

Heparanase augments epidermal growth factor receptor phosphorylation: Correlation with head and neck tumor progression

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

Institutional Review Board Statement: Not applicable.

Data Availability Statement: Not applicable.

The authors declare no conflict of interest.