SEARCH

SEARCH BY CITATION

Keywords:

  • extracellular signal-regulated kinase;
  • heparan sulfate;
  • heparanase;
  • heparin mimics;
  • hepatocyte growth factor;
  • syndecan-1;
  • vascular endothelial growth factor

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Heparanase is an endoglucuronidase that cleaves heparan sulfate chains of proteoglycans. In many malignancies, high heparanase expression and activity correlate with an aggressive tumour phenotype. A major consequence of heparanase action in cancer is a robust up-regulation of growth factor expression and increased shedding of syndecan-1 (a transmembrane heparan sulfate proteoglycan). Substantial evidence indicates that heparanase and syndecan-1 work together to drive growth factor signalling and regulate cell behaviours that enhance tumour growth, dissemination, angiogenesis and osteolysis. Preclinical and clinical studies have demonstrated that therapies targeting the heparanase/syndecan-1 axis hold promise for blocking the aggressive behaviour of cancer.


Abbreviations
ERK

extracellular signal-regulated kinase

FGF2

fibroblast growth factor 2

GAG

glycosaminoglycan

HAT

histone acetyl transferase

HGF

hepatocyte growth factor

HSPG

heparan sulfate proteoglycan

IRS-1

insulin receptor substrate-1

MMP-9

matrix metalloproteinase-9

PKC

protein kinase C

VEGF

vascular endothelial growth factor

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Heparanase is a multifunctional molecule whose expression is closely associated with enhanced aggressive behaviour of many types of tumours [1-4]. Heparanase drives tumour progression by up-regulating the expression and bioavailability of several key growth factors that flood the tumour microenvironment. Additionally, heparanase up-regulates the expression of the heparan sulfate-bearing proteoglycan syndecan-1 and also promotes its shedding from the cell surface. Shed syndecan-1 binds to the tumour-derived growth factors, concentrates them within the tumour microenvironment and potentiates their signalling activity. This coordinated action of heparanase and syndecan-1 provides a powerful mechanism for enhancing tumour growth, angiogenesis, invasion and metastasis. In this review, we discuss the mechanisms regulating formation of the heparanase/syndecan-1 axis, its impact on tumour behavior, and the novel therapeutic strategies being employed to attack this axis with the goal of diminishing the growth and spread of tumours.

Effect of the heparanase/syndecan-1 axis on growth factor signalling

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

There is increasing evidence that heparanase, by regulating the structure and function of heparan sulfate proteoglycans (HSPG), can regulate growth factor signalling and cell behaviour [5-9]. The heparanase/syndecan-1 axis has been shown to augment signalling cascades in both tumour and host cells (i.e. endothelial cells, fibroblasts, immune cells) within the tumour microenvironment. Two of the best studied examples of growth factors that are strongly regulated by the heparanase/syndecan-1 axis are hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF).

HGF, also known as scatter factor, is a potent signalling molecule that signals exclusively via its interaction with c-met, a tyrosine kinase receptor. HGF is a mitogen that mediates mesenchymal–epithelial interactions [10] and regulates several critical biological processes [11, 12]. In cancers, aberrant HGF signalling has been reported to drive angiogenesis [13], cell migration and survival [14]. Among cancers, some of the highest levels of HGF are seen in multiple myeloma [15, 16]. HGF controls several aspects of myeloma disease, including, cell proliferation, apoptosis [17], adhesion to matrix [18], and osteolytic bone disease [19]. Moreover, an elevated level of HGF in the serum of myeloma patients is associated with a poor prognosis [20].

Interestingly, both heparanase and syndecan-1 regulate HGF function. Heparanase dramatically enhances the expression of HGF by myeloma cells [21], and myeloma cell surface syndecan-1 binds strongly to HGF, facilitating HGF-enhanced myeloma tumour cell growth [22]. The heparan sulfate chains of cell surface syndecan-1 bind to HGF, sequester it at the cell surface, and thereby elevate its availability for interacting with the c-met receptor [23]. In addition, shed syndecan-1 also binds to HGF and complexes of the two molecules are detected in the serum of myeloma patients [24]. There is evidence to suggest that shed syndecan-1/HGF complexes also stimulate c-met signalling in osteoblasts [24]. This elevates receptor activator of nuclear factor kappa-B ligand secretion and subsequent osteoclast activation, providing at least one mechanism for the link between HGF and osteolysis in myeloma patients [21]. HGF is also a potent angiogenic factor and its binding to syndecan-1 may augment this activity within the myeloma bone marrow [13].

Heparanase has also been shown to stimulate VEGF secretion by both carcinoma and myeloma cells [25, 26]. Secreted VEGF forms a complex with shed syndecan-1 that positively modulates VEGF receptor signalling via activation of the extracellular signal-regulated kinase (ERK) signalling pathway, leading to enhanced endothelial invasion and angiogenesis [26]. Treatment of the VEGF–syndecan-1 complex with heparinase III, a bacterial enzyme that degrades heparan sulfate chains, or immunodepletion of the complex blocks the enhanced phosphorylation of ERK. This suggests that shed syndecan-1 is a key mediator of heparanase-enhanced signalling and invasion of endothelial cells. In addition to presenting VEGF to endothelial cells, shed syndecan-1 can also activate αvβ3 integrin, a key regulator of endothelial activation and angiogenesis [26-28]. It is intriguing to speculate that syndecan-1, which engages the αvβ3 integrin on endothelial cells and is essential for its activation, also plays a secondary role in providing VEGF to enhance this activation mechanism. VEGF bound to syndecan-1, rather than to other HSPGs in the matrix, would be most effective at integrin activation because it would be directly supplied by syndecan-1 to vascular endothelial growth factor receptor 2 complexed with the integrin at the cell surface. Central to this process of VEGF signalling and integrin activation is the up-regulation of syndecan-1 shedding by heparanase.

Biology and mechanisms of syndecan-1 shedding

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

The core protein sequence for syndecan-1 is comprised of three major domains: (a) an extracellular domain bearing the glycosaminoglycan (GAGs) chains that are predominantly heparan sulfate; (b) a short transmembrane domain; and (c) a highly conserved cytoplasmic domain [29] (Fig. 1). Proteolytic cleavage of the extracellular domain in a region near the plasma membrane of the cell releases a soluble form of the proteoglycan containing intact heparan sulfate chains [30]. Because the heparan sulfate chains within the ectodomain often contain bound ligands (e.g. growth factors) that promote signalling, it forms an autocrine signalling complex that, upon shedding, is transformed into a powerful paracrine regulator of cellular function [31]. The shed form of syndecan-1 can either remain soluble or bind and accumulate within the extracellular matrix [32]. Cells constitutively shed low levels of syndecan-1, although various stimuli (e.g. chemokines, growth factors, bacterial virulence factors and insulin) trigger signalling pathways that elevate the expression and/or activity of proteases to accelerate shedding [31, 33].

image

Figure 1. Schematic model of syndecan-1 structure. Syndecan-1 core protein consists of three major domains: a long extracellular domain that bears the heparan sulfate (HS) and chondroitin sulfate (CS) chains at distinct sites; a short transmembrane domain; and a cytoplasmic domain that is highly conserved among different syndecans.

Download figure to PowerPoint

Syndecan-1 shedding is regulated by several known mechanisms. Phosphorylation of tyrosine residues present in the cytoplasmic domain [34] and the interaction of Rab5 with the cytoplasmic domain [35] have been shown to control cleavage of the ectodomain. In addition, it was recently demonstrated that the GAG chains of syndecan-1 are active modulators of its shedding in epithelial cells and in different tumour cell lines [36]. A reduction in the GAG content of syndecans renders their core protein highly susceptible to cleavage by metalloproteases. Reducing the amount of heparan sulfate either by addition of recombinant human heparanase or by addition of bacterial heparinase III elevates syndecan-1 shedding dramatically [37]. There are several potential means by which heparan sulfate chains of syndecan-1 may regulate its shedding. These include: (a) physically blocking sheddases from accessing the cleavage sites; (b) stabilizing the core protein in a conformation that is less susceptible to proteolysis; and/or (c) helping to maintain the syndecan–Rab5 complex.

Shed syndecan-1 in cancer

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Shed syndecans have been detected in a number of tumour types and represent a novel therapeutic target [38, 39]. High levels of shed syndecan-1 have been reported in lung cancer [40], Hodgkin's lymphoma [41] and multiple myeloma [42]. Levels of serum syndecan-1 are a prognostic marker in lung cancer [40]. In myeloma, a high level of syndecan-1 in the serum is an independent predictor of poor prognosis for patients [43] and a reliable prognostic factor at different phases of the disease [44]. In cancers such as multiple myeloma, the tumour cells constitutively shed high levels of syndecan-1 and are probably the major source of soluble syndecan-1 in this disease [45]. However, in breast cancer, shed syndecan-1 is derived largely from the stromal fibroblasts present in the tumour [46, 47]. Shed syndecan-1 elevates the in vitro proliferation of T47D breast carcinoma cells [48]. By contrast, over-expression of a soluble form of syndecan-1 promoted an invasive phenotype but concomitantly inhibited the proliferation of MCF-7 breast cancer cells [49]. Synthetic peptides that mimic regions of soluble syndecan-1 have also been shown to enhance the invasion of tumour cell lines [50]. The earliest evidence that shed syndecan-1 can promote tumour growth in vivo came from studies using ARH-77 human lymphoblastoid cells [51]. When these cells were engineered to express soluble syndecan-1 and injected into human bone implanted in immunodeficient mice (SCID-hu model), they grew more aggressively and disseminated faster than their control-transfected counterparts. The soluble syndecan-1 from the ARH-77 cells accumulated extensively within the interstitial matrix of the human bone marrow. This closely resembles the pattern of syndecan-1 staining seen in myeloma patients where shed syndecan-1 becomes trapped in the bone marrow matrix and within the regions of marrow fibrosis [32]. Interestingly, the soluble form of syndecan-1 did not affect ARH-77 cell proliferation in vitro, suggesting that the major effect of shed syndecan-1 in vivo is in regulating cross-talk between the tumour and host cells that promotes growth and dissemination of the tumour cells.

Heparanase regulates syndecan-1 shedding and function

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Up-regulation of heparanase expression or addition of exogenous recombinant heparanase to myeloma cells stimulates syndecan-1 expression and shedding [37, 52]. Mechanistically, this enhanced shedding of syndecan-1 is partly a result of heparanase-mediated activation of ERK signalling, which leads to the increased expression of matrix metalloproteinase-9 (MMP-9), a sheddase of syndecan-1 [6]. ERK activation by heparanase in myeloma cells is highly dependent on the heparan sulfate-degrading activity of heparanase [6], although, in other cell types, ERK signalling can be activated by latent heparanase that is devoid of enzymatic activity [53]. In myeloma cells, the primary mediator of heparanase induced ERK activation is the insulin receptor signalling pathway [5]. In this pathway, heparanase plays a dual role by up-regulating the phosphorylation of insulin receptors and by enhancing protein kinase C (PKC) activity. PKC in turn up-regulates the expression of insulin receptor substrate-1 (IRS-1), the principal intracellular substrate of insulin receptor tyrosine kinase activity. IRS-1 is the most upstream molecule in the signal transduction cascade mediated by insulin, IL-4 and insulin-like growth factor-1. IRS-1 docks with the insulin receptor and undergoes phosphorylation and phospho-IRS-1 engages multiple downstream signalling molecules, resulting in ERK phosphorylation. These findings provide the first evidence for cooperation between heparanase expression and ERK activation in regulating the expression of a protease that leads to the shedding of syndecan-1. It is interesting that, in multiple myeloma, the activation of ERK requires the enzyme activity of heparanase. This suggests that stimulation of signalling occurs as a result of the clipping of heparan sulfate chains by heparanase. However, how the trimming of syndecan-1 by heparanase can activate the insulin receptor remains unclear. We speculate that heparanase remodelling of syndecan-1 heparan sulfate triggers clustering of the proteoglycan at the cell surface, forming a molecular complex that enhances phosphorylation of the insulin receptor and stimulates PKC activity. Interestingly, heparanase facilitates the clustering of syndecan-1 and syndecan-4 on the surface of human glioma cells and thereby initiates the signalling cascades that involve Rac1, Src and the PKC pathway, resulting in enhanced cell adhesion and spreading [54]. Clustering of syndecan-1 and 4 is mediated by the heparin binding domains present in heparanase and this clustering does not require the heparan sulfate-degrading activity of the enzyme.

There are multiple ways in which heparanase may regulate the function of syndecan-1 and other heparan sulfate proteoglycans. Heparanase degradation of heparan sulfate chains can initiate signalling cascades either by exposing cryptic sites on the heparan sulfate chains or on the core protein of HSPGs. This facilitates a close interaction of the binding partners with HSPGs. In melanoma cells, heparanase stimulates FGF2 signalling by degrading the cell surface heparan sulfate chains [55]. Modification of heparan sulfate chains by heparanase enhances the binding of FGF2 to cell surfaces and leads to stimulation of ERK and focal adhesion kinase phosphorylation [55]. High-affinity FGF2 binding and signalling require heparan sulfate chains of a minimum size and with some preference for specific structural features of the heparan sulfate. Depending upon the extent of heparan sulfate degradation by heparanase, sequences on the heparan sulfate chains, which bind to either FGF2 or fibroblast growth factor receptor, could be removed or cryptic sites could be revealed [56, 57]. Heparanase therefore can modify cellular heparan sulfate to support FGF2-stimulated signalling, potentially through modifying heparan sulfate structures to alter interactions with either FGF2 or fibroblast growth factor receptor, or both. Moreover, interplay between heparanase and syndecan-1 is required for renal tubular cells to undergo FGF2-induced epithelial mesenchymal transition [58].

The cleavage of heparan sulfate chains by heparanase does not merely stimulate syndecan-1 shedding but may ‘de-protect’ the syndecan from recognition by other proteins [36]. As discussed above, an example of this is enhanced MMP-mediated release of syndecan-1 from the cell surface when heparan sulfate chains have been trimmed by heparanase [6]. Another example is the binding of lacritin, a prosecretory epithelial mitogen found in the tear ducts that binds directly to the syndecan-1 core protein, although only after heparan sulfate chains have been trimmed by heparanase [9]. This is highly specific for syndecan-1, and other syndecan family members such as syndecan-2 or syndecan-4 cannot bind lacritin. The novel step in this is that the binding necessitates prior partial or complete removal of heparan sulfate chains of syndecan-1 by endogenous heparanase. Modification of the N-terminal domain of syndecan-1 therefore facilitates its interaction with the C-terminal mitogenic domain of lacritin [9]. Thus, heparanase modification of syndecan-1 transforms a widely expressed HSPG into a highly selective surface binding protein. Furthermore, cleavage of heparan sulfate chains can alter membrane localization of the proteoglycan, consequently altering the availability of heparan sulfate to interact with signalling molecules. This has been demonstrated with syndecan-1 and glypican, whose localization in the plasma membrane is affected by removing heparan sulfate chains [59, 60].

Nuclear function of heparanase and syndecan-1

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

In addition to their extracellular localization, both heparanase and syndecan-1 have been shown to be present within the nucleus of cells. Heparanase in the nucleus of cells is enzymatically active [61]. Nuclear heparanase is associated with increased cell differentiation [62]. Furthermore, heparanase localization within the nucleus also dictates its function. In brain metastatic breast cancer, heparanase localizes to the nucleolus after stimulation by epidermal growth factor [63]. In the nucleolus, heparanase enhances DNA topoisomerase I activity, which subsequently increases cellular proliferation. Moreover, heparanase preferentially associates with euchromatin, a lightly packed form of chromatin where gene transcription typically occurs, in T lymphocytes [64]. The data suggest that heparanase in the nucleus of the T lymphocytes can modulate histone H3 methylation through its interaction with a transcriptional complex [64]. The cellular localization of heparanase can also serve as a predictor of prognosis in some cancers. This has been demonstrated in head and neck cancers, as well as gastric and oesophageal cancers, where nuclear localization of heparanase predicted a favourable outcome for patients, although its cytoplasmic localization correlated with a poor outcome [65-67].

Several studies have demonstrated localization of heparan sulfate or heparan sulfate proteoglycans in the nucleus [68-71]. Here, the heparan sulfate chains of proteoglycans can regulate expression of different genes, possibly by regulating the level of histone acetylation. One study demonstrated that free GAG chains can decrease histone acetylation by 50% [72]. The uptake of these GAGs by tumour cells is a selective process, and their inhibition of histone acetylation is dependent upon heparan sulfate chain length and sulfation pattern [72, 73]. This indicates that there is some degree of specificity rather than just random inhibition by heparan sulfate. Syndecan-1 has been shown to be present in the nucleus of both mesothelioma and myeloma tumour cells [70, 74]. In mesothelioma, nuclear translocation of syndecan-1 was linked to specific points of the cell cycle, indicating that syndecan-1 may have a specific function during cell division through interactions with microtubule structures [70]. Because the heparan sulfate chains present on the core protein of syndecan-1 bind a myriad of growth factors and regulatory proteins, it is likely that syndecan-1 transports cargo to the nucleus. Studies have indicated that fibroblast growth factor-2 (FGF-2) binds to heparan sulfate proteoglycans and translocates to the nucleus [71, 75]. Additionally, syndecan-1 co-localizes with FGF-2 and heparanase in the nucleus of mesothelioma cells [76]. Furthermore, cell surface heparan sulfate chains have been implicated in the cellular uptake and nuclear translocation of several molecules, including heparanase [61].

The heparanase/syndecan-1 axis functions very uniquely within the nucleus. Active heparanase enzyme decreases the level of nuclear syndecan-1 and thereby removes the block exerted by syndecan-1 on histone acetyl transferase enzyme (HAT) [74, 77]. This was first demonstrated in myeloma, where the elevation of heparanase expression in myeloma tumour cells is coupled with the loss of syndecan-1 in the nucleus, resulting in an increase in HAT activity. This increase in HAT activity upon heparanase expression correlates with increased expression of several genes known to promote an aggressive tumour phenotype [77]. The precise mechanism behind how heparanase regulates nuclear levels of syndecan-1 remains unknown. One possibility is that heparanase modifies syndecan-1 in a manner that results in a loss of the ability of syndecan-1 to translocate to the nucleus. The mechanism of action of heparanase/syndecan-1 axis on tumour cells and the microenvironment is summarized in Fig. 2.

image

Figure 2. Model of the heparanase/syndecan-1 axis in cancer. The model shows the series of molecular events triggered by heparanase in tumour cells that establish the heparanase/syndecan-1 axis. When heparanase is elevated in tumours, several events occur. (1) Levels of active ERK (P-ERK) are elevated in the cells. (2) P-ERK up-regulates the cellular expression of VEGF and MMP-9. HGF is also elevated in these cells but via signalling pathways that are independent of P-ERK. (3) With the increase in heparanase expression, syndecan-1 levels in the nucleus are diminished, leading to an increase in the levels of acetylated histone H3. This facilitates the transcription of MMP-9 and VEGF. (4) As a result of heparanase activity, the HS chains of syndecan-1 (SDC-1) on the cell surface are trimmed, leading to enhanced cleavage of the core protein by MMP-9, which is now present in abundance. (5) The heparan sulfate chains of the shed syndecan-1 bind and complex with growth factors, including HGF and VEGF, whose expression is also stimulated by the expression of heparanase. (6) Shed syndecan-1 bearing the growth factors binds to extracellular matrix proteins (e.g. fibronectin, collagens) and sequesters these growth factors in the tumour microenvironment, as well as at distal sites. (7) Shed syndecan-1 binding potentiates the signalling of the bound growth factors. This results in a strong, sustained downstream signalling in the host cells (e.g. stromal cells, endothelial cells), priming the microenvironment to support aggressive tumour growth.

Download figure to PowerPoint

An emerging role for heparanase and syndecan-1 in exosome biogenesis and function

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

In addition to the mechanisms described above, heparanase and syndecan-1 appear to play important roles in regulating exosomes, lipid bilayer-bound extracellular vesicles 30–100 nm in diameter. Exosome secretion is up-regulated as tumours become increasingly aggressive, and the cargo contained within exosomes, including proteins, mRNA and miRNA, can provide an important mechanism for intercellular communication between tumour and host cells [78, 79]. For example, exosomes derived from tumour cells have been shown to promote immune evasion [80], angiogenesis [81] and metastasis [82, 83]. Interestingly, a number of different heparan sulfate proteoglycans have been found in exosomes derived from various tissues (Table 1). Delivery to recipient cells of these exosomes bearing heparan sulfate proteoglycans along with their binding partners (e.g. FGFs, VEGF, and HGF) may represent an important means of heparan sulfate-assisted signalling. In addition, syndecan-1 plays a key role in regulating the formation of exosomes through the interaction of the syndecan-1 cytoplasmic domain with both syntenin and ALIX to form a complex that supports the budding of intraluminal vesicles within endosomal membranes [84]. This study also revealed that heparan sulfate was essential for robust exosome biogenesis. Heparanase has been found in exosomes isolated from the ascites of ovarian cancer patients [85], and recent work in our laboratory has shown that heparanase significantly up-regulates exosome biogenesis and alters the protein composition and function of exosomes secreted by myeloma tumour cells [[115]]. Although the mechanism by which heparanase enhances exosome biogenesis is unknown, it is reasonable to speculate that remodelling of the heparan sulfate chains of syndecan-1 by heparanase enhances the formation of the syndecan-1–syntenin–ALIX complex, which in turn drives exosome biogenesis. Given the potential importance of exosomes in regulating the progression of cancer and other diseases, it will be important to further explore how heparanase and syndecan-1 participate in regulating the formation and function of exosomes.

Table 1. Heparan sulfate proteoglycans found in exosomes, as compiled based on information available at http://exocarta.org (an exosome content database)
MoleculeCell/tissue/biological fluid of origin
HeparanaseOvarian cancer ascites [85]
Syndecan-1Bladder cancer cells [107], colorectal cancer cells [108], urine [109]
Syndecan-4Hepatocytes [110], colorectal cancer cells [108], saliva [111]
Glypican-1Saliva [111]
Glypican-4Reticulocytes [112], saliva [111]
Glypican-5Mast cells [113]
PerlecanEmbryonic fibroblasts [114], bladder cancer cells [107], colorectal cancer cells [108], colon cancer cell lines [110], saliva [111], urine [109]

Therapeutic strategies to target the heparanase/syndecan-1 axis

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Because of the importance of the syndecan-1/heparanase axis in driving cancer, therapeutic agents that disrupt this axis could potentially be useful in the clinic. As a result of its multiple functions in driving the aggressive behaviour of many tumour types, heparanase has received substantial attention as a therapeutic target, whereas syndecan-1 is a more difficult molecule to exploit therapeutically.

Several approaches hold potential for the inhibition of heparanase, including the use of modified heparins, small molecule inhibitors and function-blocking monoclonal antibodies. Heparin is an inhibitor of heparanase enzyme activity, however it cannot be used at high concentrations as an anti-tumour drug because of its anti-coagulant activity. Thus, modified heparins or heparin mimics have been developed and have taken on many forms, with predictably wide-ranging results [86]. A comprehensive overview of heparin mimics as drugs has been provided previously [87]. Here, we focus on several heparin mimics that were developed with an eye on their ability to inhibit heparanase enzyme activity. These have been tested in preclinical models and have moved or are moving toward human trials in patients with cancer.

PI-88 is a phosphosulfomannoligosaccharide obtained by hydrolysis of yeast mannan that yields a heterogeneous mixture of highly sulfated di- to hexasaccharides [88]. This compound has anti-heparanase and anti-angiogenic activity, presumably as a result of its binding to heparanase and to binding factors such as VEGF. PI-88 does have some anti-coagulant activity and, in human subjects, can cause thrombocytopenia, thrombosis, injection site haemorrhage and other bleeding problems [89]. However, it is reasonably well-tolerated and is efficacious against some cancers, most notably hepatocellular carcinoma [89]. The clinical development of PI-88 was initiated by Progen Pharmaceuticals Ltd (Darra, Queensland, Australia) and was recently licensed to Medigen Biotechnology Corporation (Taipei City Taiwan), which is now conducting a prospective randomized, double-blinded, multicentre, phase III trial in subjects with hepatitis virus-related hepatocellular carcinoma after surgical resection. A second generation of anti-heparanase compounds developed by Progen Pharmaceuticals Ltd, including PG545, showed promise in preclinical studies using murine models of breast, prostate, liver, lung, colon, head and neck cancers, and melanoma [90]. PG545 is a fully sulfated, synthetic tetrasaccharide that is homogenous in composition [91]. Recent studies demonstrated that PG545 inhibited both heparanase activity and expression and also blocked tumour growth and metastasis in animal models [92]. Unfortunately, phase I trials in humans had to be halted as a result of an unexpected reaction at the site of injection and so the future prospects for this drug remain unknown.

SST0001 (formerly designated as G4000) is a modified heparin that is 100% N-acetylated and 25% glycol split [86, 93] and has a mean molecular mass of 20 kDa. N-acetylation renders it non-anticoagulant and glycol splitting appears to enhance its affinity for heparanase, where it affectively blocks heparanase enzyme activity [93]. In preclinical models, SST0001 has been shown to have efficacy against Ewing's sarcoma, myeloma and pancreatic cancer [94-97]. Pharmacodynamic studies indicate that SST0001 effectively inhibits heparanase activity in vivo and can regulate levels of growth factors (e.g. HGF and VEGF) and inhibit angiogenesis [96]. Moreover, SST0001 works well in combination with dexamethasone against myeloma tumours growing in mice [96]. Importantly, SST0001 is not toxic to cells growing in vitro. This suggests that its anti-tumour effects in vivo are a result of disruption of the tumour-promoting effects that heparanase has within the tumour microenvironment. Sigma-tau Research Switzerland SA (Mendrisio, Switzerland) recently initiated a phase I clinical trial of SST0001 in patients with advanced multiple myeloma. Another glycol-split heparin compound similar to SST0001 is M402. M402 is smaller than SST0001, having a mean molecular mass of 6 kDa [98]. In addition, it differs from SST0001 in that it was not N-acetylated and thus may have broader activity in binding growth factors than does SST0001. Nonetheless, given that M402, SST0001, PG545 and PI-88 are all highly sulfated, it is likely that they all have biological activity beyond inhibition of heparanase enzyme activity. M402 showed efficacy in a melanoma model of experimental metastasis and in spontaneous metastasis using the 4T1 murine mammary carcinoma model [98]. A phase 1/2 proof-of-concept clinical trial of M402 in combination with gemcitabine in patients with advanced metastatic pancreatic cancer began in July 2012.

Now that multiple heparin mimics have reached clinical trials in humans, it will be interesting to see which, if any, of the strategies have resulted in a clinically relevant drug. For those that show safety and tolerability in phase I studies, the challenge will be to determine when during the progression of cancer is the best time to begin their administration, and how to use them in combination with other treatments. If these heparin mimics do disrupt the tumour microenvironment in human cancers, they may be effective in combination with drugs that target tumour cells. This strategy would effectively target both the host environment and the malignant cell itself. Interestingly, heparanase appears to play an active role in inflammatory conditions and kidney dysfunction and thus inhibitors of heparanase may be of therapeutic use in diseases such as colitis, sepsis [99], autoimmune diabetes [100] and diabetic nephropathy [101].

Although proteoglycans are more difficult to target therapeutically than heparanase, several approaches have shown promise. One possibility is to interfere with normal assembly of GAG chains on the core proteins of proteoglycans using hydrophobic aglycones. These aglycones, depending on their structure, can drive the formation of antiproliferative glycosaminoglycans or inhibit GAG synthesis or proteoglycan synthesis [73, 102, 103]. This can result in the inhibition of tumour growth and angiogenesis [73, 102]. Another approach is to generate fragments of heparan sulfate that have anti-tumour activity. This is accomplished by using bacterial enzymes to degrade heparan sulfate in vitro followed by the administration of these fragments to animals bearing tumour. This approach has been successful in blocking tumour growth in murine models of melanoma and myeloma [57, 95]. Both of these studies used a pool of degraded heparan sulfate but did not identify the specific structures within that pool that have anti-tumour activity. The precise identification of these anti-tumour structures within heparan sulfate could provide clues regarding how to better prepare heparin mimics that will effectively inhibit tumour growth and progression.

Recent studies have revealed that syndecan-1 docks with integrins and the insulin-like growth factor-1 receptor to form a ternary complex that activates integrin signalling [104, 105]. This docking occurs through a specific region of the syndecan-1 core protein extracellular domain including amino acids 92–119. Synstatin, a synthetic peptide composed of amino acids 92–119 of the syndecan-1 core protein, inhibits angiogenesis and blocks growth of carcinomas in vivo [104]. This growth inhibition in vivo is probably partly a result of the inhibition of αvβ3 integrin signalling required for endothelial cell migration and angiogenesis. It will be interesting to determine whether targeting both arms of the syndecan-1/heparanase axis using synstatin in combination with heparin mimics will have additive or synergistic effects in murine models of cancer. Recent advances in RNAi technology also offer an opportunity to perturb the expression of key molecules or the signalling pathway in the heparanase/syndecan-1 axis. Finally, recent studies have shown the potential for expressing specific micro RNAs, such as miRNA-1258, which blocks heparanase expression and diminishes the metastasis of breast cancer cells [106].

Summary

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

Although it is well known that heparanase and syndecan-1 individually can regulate the behaviour of tumours, it has recently become clear that these two molecules work in concert to drive tumour progression. Heparanase not only enhances syndecan-1 expression, but also dramatically influences syndecan-1 location by increasing its shedding from the cell surface, altering its position on the plasma membrane and diminishing its abundance in the nucleus. In addition, heparanase up-regulates the expression of growth factors such as HGF and VEGF, which then bind to syndecan-1 heparan sulfate, forming a complex that protects the growth factor from degradation, retains the growth factor within the tumour microenvironment, and also potentiates interaction of the growth factor with its high affinity signalling receptor. Heparanase and syndecan-1 both, and perhaps by working together, drive exosome biogenesis and regulate exosome function. In addition, both heparanase and syndecan-1 are retained as cargo within exosomes where they again may act together to influence the behaviour of cells within the tumour microenvironment and distally within niches that may nurse the growth of metastasizing cells. As a result of decades of previous work on heparanase and proteoglycans, the field has moved closer to the exciting possibility of translating basic findings into new cancer therapies. Several drug candidates that have been designed to block heparanase or syndecan-1 function are now in various stages of preclinical and clinical investigation, with the potential to significantly blunt tumour progression.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References

This work was supported by NIH grants CA135075, CA138340 and CA138535 to RDS, by Grant No. 2009230 from the United States–Israel Binational Science Foundation (jointly to IV and RDS). The authors apologize for the inability to reference all studies relevant to this review as a result of space limitations.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Effect of the heparanase/syndecan-1 axis on growth factor signalling
  5. Biology and mechanisms of syndecan-1 shedding
  6. Shed syndecan-1 in cancer
  7. Heparanase regulates syndecan-1 shedding and function
  8. Nuclear function of heparanase and syndecan-1
  9. An emerging role for heparanase and syndecan-1 in exosome biogenesis and function
  10. Therapeutic strategies to target the heparanase/syndecan-1 axis
  11. Summary
  12. Acknowledgements
  13. References
  • 1
    Barash U, Cohen-Kaplan V, Dowek I, Sanderson RD, Ilan N & Vlodavsky I (2010) Proteoglycans in health and disease: new concepts for heparanase function in tumor progression and metastasis. FEBS J 277, 38903903.
  • 2
    Arvatz G, Shafat I, Levy-Adam F, Ilan N & Vlodavsky I (2011) The heparanase system and tumor metastasis: is heparanase the seed and soil? Cancer Metastasis Rev 30, 253268.
  • 3
    Vlodavsky I, Elkin M, Abboud-Jarrous G, Levi-Adam F, Fuks L, Shafat I & Ilan N (2008) Heparanase: one molecule with multiple functions in cancer progression. Connect Tissue Res 49, 207210.
  • 4
    Ilan N, Elkin M & Vlodavsky I (2006) Regulation, function and clinical significance of heparanase in cancer metastasis and angiogenesis. Int J Biochem Cell Biol 38, 20182039.
  • 5
    Purushothaman A, Babitz SK & Sanderson RD (2012) Heparanase enhances the insulin receptor signaling pathway to activate ERK in multiple myeloma. J Biol Chem 287, 4128841296.
  • 6
    Purushothaman A, Chen L, Yang Y & Sanderson RD (2008) Heparanase stimulation of protease expression implicates it as a master regulator of the aggressive tumor phenotype in myeloma. J Biol Chem 283, 3262832636.
  • 7
    Ridgway LD, Wetzel MD & Marchetti D (2011) Heparanase modulates Shh and Wnt3a signaling in human medulloblastoma cells. Exp Ther Med 2, 229238.
  • 8
    Ridgway LD, Wetzel MD, Ngo JA, Erdreich-Epstein A & Marchetti D (2012) Heparanase-induced GEF-H1 signaling regulates the cytoskeletal dynamics of brain metastatic breast cancer cells. Mol Cancer Res 10, 689702.
  • 9
    Ma P, Beck SL, Raab RW, McKown RL, Coffman GL, Utani A, Chirico WJ, Rapraeger AC & Laurie GW (2006) Heparanase deglycanation of syndecan-1 is required for binding of the epithelial-restricted prosecretory mitogen lacritin. J Cell Biol 174, 10971106.
  • 10
    Neuss S, Becher E, Woltje M, Tietze L & Jahnen-Dechent W (2004) Functional expression of HGF and HGF receptor/c-met in adult human mesenchymal stem cells suggests a role in cell mobilization, tissue repair, and wound healing. Stem Cells 22, 405414.
  • 11
    Nakamura T, Sakai K & Matsumoto K (2011) Hepatocyte growth factor twenty years on: much more than a growth factor. J Gastroenterol Hepatol 26, 188202.
  • 12
    Birchmeier C, Birchmeier W, Gherardi E & Vande Woude GF (2003) Met, metastasis, motility and more. Nat Rev Mol Cell Biol 4, 915925.
  • 13
    You WK & McDonald DM (2008) The hepatocyte growth factor/c-Met signaling pathway as a therapeutic target to inhibit angiogenesis. BMB Rep 41, 833839.
  • 14
    Lesko E & Majka M (2008) The biological role of HGF-MET axis in tumor growth and development of metastasis. Front Biosci 13, 12711280.
  • 15
    Borset M, Hjorth-Hansen H, Seidel C, Sundan A & Waage A (1996) Hepatocyte growth factor and its receptor c-met in multiple myeloma. Blood 88, 39984004.
  • 16
    Zhan F, Hardin J, Kordsmeier B, Bumm K, Zheng M, Tian E, Sanderson R, Yang Y, Wilson C, Zangari M et al. (2002) Global gene expression profiling of multiple myeloma, monoclonal gammopathy of undetermined significance, and normal bone marrow plasma cells. Blood 99, 17451757.
  • 17
    Derksen PW, de Gorter DJ, Meijer HP, Bende RJ, van Dijk M, Lokhorst HM, Bloem AC, Spaargaren M & Pals ST (2003) The hepatocyte growth factor/Met pathway controls proliferation and apoptosis in multiple myeloma. Leukemia 17, 764774.
  • 18
    Holt RU, Baykov V, Ro TB, Brabrand S, Waage A, Sundan A & Borset M (2005) Human myeloma cells adhere to fibronectin in response to hepatocyte growth factor. Haematologica 90, 479488.
  • 19
    Hjertner O, Torgersen ML, Seidel C, Hjorth-Hansen H, Waage A, Borset M & Sundan A (1999) Hepatocyte growth factor (HGF) induces interleukin-11 secretion from osteoblasts: a possible role for HGF in myeloma-associated osteolytic bone disease. Blood 94, 38833888.
  • 20
    Seidel C, Borset M, Turesson I, Abildgaard N, Sundan A & Waage A (1998) Elevated serum concentrations of hepatocyte growth factor in patients with multiple myeloma. The Nordic Myeloma Study Group. Blood 91, 806812.
  • 21
    Ramani VC, Yang Y, Ren Y, Nan L & Sanderson RD (2011) Heparanase plays a dual role in driving hepatocyte growth factor (HGF) signaling by enhancing HGF expression and activity. J Biol Chem 286, 64906499.
  • 22
    Derksen PW, Keehnen RM, Evers LM, van Oers MH, Spaargaren M & Pals ST (2002) Cell surface proteoglycan syndecan-1 mediates hepatocyte growth factor binding and promotes Met signaling in multiple myeloma. Blood 99, 14051410.
  • 23
    Deakin JA & Lyon M (1999) Differential regulation of hepatocyte growth factor/scatter factor by cell surface proteoglycans and free glycosaminoglycan chains. J Cell Sci 112, 19992009.
  • 24
    Seidel C, Borset M, Hjertner O, Cao D, Abildgaard N, Hjorth-Hansen H, Sanderson RD, Waage A & Sundan A (2000) High levels of soluble syndecan-1 in myeloma-derived bone marrow: modulation of hepatocyte growth factor activity. Blood 96, 31393146.
  • 25
    Cohen-Kaplan V, Naroditsky I, Zetser A, Ilan N, Vlodavsky I & Doweck I (2008) Heparanase induces VEGF C and facilitates tumor lymphangiogenesis. Int J Cancer 123, 25662573.
  • 26
    Purushothaman A, Uyama T, Kobayashi F, Yamada S, Sugahara K, Rapraeger AC & Sanderson RD (2010) Heparanase-enhanced shedding of syndecan-1 by myeloma cells promotes endothelial invasion and angiogenesis. Blood 115, 24492457.
  • 27
    Brooks PC, Clark RA & Cheresh DA (1994) Requirement of vascular integrin alpha v beta 3 for angiogenesis. Science 264, 569571.
  • 28
    Mahabeleshwar GH, Feng W, Reddy K, Plow EF & Byzova TV (2007) Mechanisms of integrin-vascular endothelial growth factor receptor cross-activation in angiogenesis. Circ Res 101, 570580.
  • 29
    Bernfield M, Gotte M, Park PW, Reizes O, Fitzgerald ML, Lincecum J & Zako M (1999) Functions of cell surface heparan sulfate proteoglycans. Annu Rev Biochem 68, 729777.
  • 30
    Fitzgerald ML, Wang Z, Park PW, Murphy G & Bernfield M (2000) Shedding of syndecan-1 and -4 ectodomains is regulated by multiple signaling pathways and mediated by a TIMP-3-sensitive metalloproteinase. J Cell Biol 148, 811824.
  • 31
    Manon-Jensen T, Itoh Y & Couchman JR (2010) Proteoglycans in health and disease: the multiple roles of syndecan shedding. FEBS J 277, 38763889.
  • 32
    Bayer-Garner IB, Sanderson RD, Dhodapkar MV, Owens RB & Wilson CS (2001) Syndecan-1 (CD138) immunoreactivity in bone marrow biopsies of multiple myeloma: shed syndecan-1 accumulates in fibrotic regions. Mod Pathol 14, 10521058.
  • 33
    Hayashida K, Bartlett AH, Chen Y & Park PW (2010) Molecular and cellular mechanisms of ectodomain shedding. Anat Rec 293, 925937.
  • 34
    Reiland J, Ott VL, Lebakken CS, Yeaman C, McCarthy J & Rapraeger AC (1996) Pervanadate activation of intracellular kinases leads to tyrosine phosphorylation and shedding of syndecan-1. Biochem J 319, 3947.
  • 35
    Hayashida K, Stahl PD & Park PW (2008) Syndecan-1 ectodomain shedding is regulated by the small GTPase Rab5. J Biol Chem 283, 3543535444.
  • 36
    Ramani VC, Pruett PS, Thompson CA, DeLucas LD & Sanderson RD (2012) Heparan sulfate chains of syndecan-1 regulate ectodomain shedding. J Biol Chem 287, 99529961.
  • 37
    Yang Y, Macleod V, Miao HQ, Theus A, Zhan F, Shaughnessy JD Jr, Sawyer J, Li JP, Zcharia E, Vlodavsky I et al. (2007) Heparanase enhances syndecan-1 shedding: a novel mechanism for stimulation of tumor growth and metastasis. J Biol Chem 282, 1332613333.
  • 38
    Sanderson RD & Couchman JR (2012) Targeting syndecan shedding in cancer. In Extracellular Matrix: Pathobiology and Signaling (Karamanos NK, ed.), pp. 802812. De Gruyter, Berlin, Germany.
  • 39
    Choi S, Lee H, Choi JR & Oh ES (2010) Shedding; towards a new paradigm of syndecan function in cancer. BMB Rep 43, 305310.
  • 40
    Joensuu H, Anttonen A, Eriksson M, Makitaro R, Alfthan H, Kinnula V & Leppa S (2002) Soluble syndecan-1 and serum basic fibroblast growth factor are new prognostic factors in lung cancer. Cancer Res 62, 52105217.
  • 41
    Vassilakopoulos TP, Kyrtsonis MC, Papadogiannis A, Nadali G, Angelopoulou MK, Tzenou T, Dimopoulou MN, Siakantaris MP, Kontopidou FN, Kalpadakis C et al. (2005) Serum levels of soluble syndecan-1 in Hodgkin's lymphoma. Anticancer Res 25, 47434746.
  • 42
    Dhodapkar MV, Kelly T, Theus A, Athota AB, Barlogie B & Sanderson RD (1997) Elevated levels of shed syndecan-1 correlate with tumour mass and decreased matrix metalloproteinase-9 activity in the serum of patients with multiple myeloma. Br J Haematol 99, 368371.
  • 43
    Seidel C, Sundan A, Hjorth M, Turesson I, Dahl IM, Abildgaard N, Waage A & Borset M (2000) Serum syndecan-1: a new independent prognostic marker in multiple myeloma. Blood 95, 388392.
  • 44
    Lovell R, Dunn JA, Begum G, Barth NJ, Plant T, Moss PA, Drayson MT & Pratt G (2005) Soluble syndecan-1 level at diagnosis is an independent prognostic factor in multiple myeloma and the extent of fall from diagnosis to plateau predicts for overall survival. Br J Haematol 130, 542548.
  • 45
    Dhodapkar MV, Abe E, Theus A, Lacy M, Langford JK, Barlogie B & Sanderson RD (1998) Syndecan-1 is a multifunctional regulator of myeloma pathobiology: control of tumor cell survival, growth, and bone cell differentiation. Blood 91, 26792688.
  • 46
    Su G, Blaine SA, Qiao D & Friedl A (2008) Membrane type 1 matrix metalloproteinase-mediated stromal syndecan-1 shedding stimulates breast carcinoma cell proliferation. Cancer Res 68, 95589565.
  • 47
    Stanley MJ, Stanley MW, Sanderson RD & Zera R (1999) Syndecan-1 expression is induced in the stroma of infiltrating breast carcinoma. Am J Clin Pathol 112, 377383.
  • 48
    Su G, Blaine SA, Qiao D & Friedl A (2007) Shedding of syndecan-1 by stromal fibroblasts stimulates human breast cancer cell proliferation via FGF2 activation. J Biol Chem 282, 1490614915.
  • 49
    Nikolova V, Koo CY, Ibrahim SA, Wang Z, Spillmann D, Dreier R, Kelsch R, Fischgrabe J, Smollich M, Rossi LH et al. (2009) Differential roles for membrane-bound and soluble syndecan-1 (CD138) in breast cancer progression. Carcinogenesis 30, 397407.
  • 50
    Aragao AZ, Belloni M, Simabuco FM, Zanetti MR, Yokoo S, Domingues RR, Kawahara R, Pauletti BA, Goncalves A, Agostini M et al. (2012) Novel processed form of syndecan-1 shed from SCC-9 cells plays a role in cell migration. PLoS One 7, e43521.
  • 51
    Yang Y, Yaccoby S, Liu W, Langford JK, Pumphrey CY, Theus A, Epstein J & Sanderson RD (2002) Soluble syndecan-1 promotes growth of myeloma tumors in vivo. Blood 100, 610617.
  • 52
    Mahtouk K, Hose D, Raynaud P, Hundemer M, Jourdan M, Jourdan E, Pantesco V, Baudard M, De Vos J, Larroque M et al. (2007) Heparanase influences expression and shedding of syndecan-1, and its expression by the bone marrow environment is a bad prognostic factor in multiple myeloma. Blood 109, 49144923.
  • 53
    Sotnikov I, Hershkoviz R, Grabovsky V, Ilan N, Cahalon L, Vlodavsky I, Alon R & Lider O (2004) Enzymatically quiescent heparanase augments T cell interactions with VCAM-1 and extracellular matrix components under versatile dynamic contexts. J Immunol 172, 51855193.
  • 54
    Levy-Adam F, Feld S, Suss-Toby E, Vlodavsky I & Ilan N (2008) Heparanase facilitates cell adhesion and spreading by clustering of cell surface heparan sulfate proteoglycans. PLoS One 3, e2319.
  • 55
    Reiland J, Kempf D, Roy M, Denkins Y & Marchetti D (2006) FGF2 binding, signaling, and angiogenesis are modulated by heparanase in metastatic melanoma cells. Neoplasia 8, 596606.
  • 56
    Kato M, Wang H, Kainulainen V, Fitzgerald ML, Ledbetter S, Ornitz DM & Bernfield M (1998) Physiological degradation converts the soluble syndecan-1 ectodomain from an inhibitor to a potent activator of FGF-2. Nat Med 4, 691697.
  • 57
    Liu D, Shriver Z, Venkataraman G, El Shabrawi Y & Sasisekharan R (2002) Tumor cell surface heparan sulfate as cryptic promoters or inhibitors of tumor growth and metastasis. Proc Natl Acad Sci USA 99, 568573.
  • 58
    Masola V, Gambaro G, Tibaldi E, Brunati AM, Gastaldello A, D'Angelo A, Onisto M & Lupo A (2012) Heparanase and syndecan-1 interplay orchestrates fibroblast growth factor-2-induced epithelial-mesenchymal transition in renal tubular cells. J Biol Chem 287, 14781488.
  • 59
    Yang Y, Borset M, Langford JK & Sanderson RD (2003) Heparan sulfate regulates targeting of syndecan-1 to a functional domain on the cell surface. J Biol Chem 278, 1288812893.
  • 60
    Mertens G, Van der Schueren B, van den Berghe H & David G (1996) Heparan sulfate expression in polarized epithelial cells: the apical sorting of glypican (GPI-anchored proteoglycan) is inversely related to its heparan sulfate content. J Cell Biol 132, 487497.
  • 61
    Schubert SY, Ilan N, Shushy M, Ben-Izhak O, Vlodavsky I & Goldshmidt O (2004) Human heparanase nuclear localization and enzymatic activity. Lab Invest 84, 535544.
  • 62
    Kobayashi M, Naomoto Y, Nobuhisa T, Okawa T, Takaoka M, Shirakawa Y, Yamatsuji T, Matsuoka J, Mizushima T, Matsuura H et al. (2006) Heparanase regulates esophageal keratinocyte differentiation through nuclear translocation and heparan sulfate cleavage. Differentiation 74, 235243.
  • 63
    Zhang L, Sullivan P, Suyama J & Marchetti D (2010) Epidermal growth factor-induced heparanase nucleolar localization augments DNA topoisomerase I activity in brain metastatic breast cancer. Mol Cancer Res 8, 278290.
  • 64
    He YQ, Sutcliffe EL, Bunting KL, Li J, Goodall KJ, Poon IK, Hulett MD, Freeman C, Zafar A, McInnes RL et al. (2012) 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. Transcription 3, 130145.
  • 65
    Doweck I, Kaplan-Cohen V, Naroditsky I, Sabo E, Ilan N & Vlodavsky I (2006) Heparanase localization and expression by head and neck cancer: correlation with tumor progression and patient survival. Neoplasia 8, 10551061.
  • 66
    Ohkawa T, Naomoto Y, Takaoka M, Nobuhisa T, Noma K, Motoki T, Murata T, Uetsuka H, Kobayashi M, Shirakawa Y et al. (2004) Localization of heparanase in esophageal cancer cells: respective roles in prognosis and differentiation. Lab Invest 84, 12891304.
  • 67
    Takaoka M, Naomoto Y, Ohkawa T, Uetsuka H, Shirakawa Y, Uno F, Fujiwara T, Gunduz M, Nagatsuka H, Nakajima M et al. (2003) Heparanase expression correlates with invasion and poor prognosis in gastric cancers. Lab Invest 83, 613622.
  • 68
    Ishihara M, Fedarko NS & Conrad HE (1986) Transport of heparan sulfate into the nuclei of hepatocytes. J Biol Chem 261, 1357513580.
  • 69
    Richardson TP, Trinkaus-Randall V & Nugent MA (2001) Regulation of heparan sulfate proteoglycan nuclear localization by fibronectin. J Cell Sci 114, 16131623.
  • 70
    Brockstedt U, Dobra K, Nurminen M & Hjerpe A (2002) Immunoreactivity to cell surface syndecans in cytoplasm and nucleus: tubulin-dependent rearrangements. Exp Cell Res 274, 235245.
  • 71
    Hsia E, Richardson TP & Nugent MA (2003) Nuclear localization of basic fibroblast growth factor is mediated by heparan sulfate proteoglycans through protein kinase C signaling. J Cell Biochem 88, 12141225.
  • 72
    Buczek-Thomas JA, Hsia E, Rich CB, Foster JA & Nugent MA (2008) Inhibition of histone acetyltransferase by glycosaminoglycans. J Cell Biochem 105, 108120.
  • 73
    Nilsson U, Johnsson R, Fransson LA, Ellervik U & Mani K (2010) Attenuation of tumor growth by formation of antiproliferative glycosaminoglycans correlates with low acetylation of histone H3. Cancer Res 70, 37713779.
  • 74
    Chen L & Sanderson RD (2009) Heparanase regulates levels of syndecan-1 in the nucleus. PLoS One 4, e4947.
  • 75
    Tumova S, Hatch BA, Law DJ & Bame KJ (1999) Basic fibroblast growth factor does not prevent heparan sulphate proteoglycan catabolism in intact cells, but it alters the distribution of the glycosaminoglycan degradation products. Biochem J 337, 471481.
  • 76
    Zong F, Fthenou E, Wolmer N, Hollosi P, Kovalszky I, Szilak L, Mogler C, Nilsonne G, Tzanakakis G & Dobra K (2009) Syndecan-1 and FGF-2, but not FGF receptor-1, share a common transport route and co-localize with heparanase in the nuclei of mesenchymal tumor cells. PLoS One 4, e7346.
  • 77
    Purushothaman A, Hurst DR, Pisano C, Mizumoto S, Sugahara K & Sanderson RD (2011) Heparanase-mediated loss of nuclear syndecan-1 enhances histone acetyltransferase (HAT) activity to promote expression of genes that drive an aggressive tumor phenotype. J Biol Chem 286, 3037730383.
  • 78
    Record M, Subra C, Silvente-Poirot S & Poirot M (2011) Exosomes as intercellular signalosomes and pharmacological effectors. Biochem Pharmacol 81, 11711182.
  • 79
    Ge R, Tan E, Sharghi-Namini S & Asada HH (2012) Exosomes in cancer microenvironment and beyond: have we overlooked these extracellular messengers? Cancer Microenviron 5, 323332.
  • 80
    Bobrie A, Colombo M, Raposo G & Thery C (2011) Exosome secretion: molecular mechanisms and roles in immune responses. Traffic 12, 16591668.
  • 81
    Janowska-Wieczorek A, Wysoczynski M, Kijowski J, Marquez-Curtis L, Machalinski B, Ratajczak J & Ratajczak MZ (2005) Microvesicles derived from activated platelets induce metastasis and angiogenesis in lung cancer. Int J Cancer 113, 752760.
  • 82
    Peinado H, Lavotshkin S & Lyden D (2011) The secreted factors responsible for pre-metastatic niche formation: old sayings and new thoughts. Semin Cancer Biol 21, 139146.
  • 83
    Peinado H, Aleckovic M, Lavotshkin S, Matei I, Costa-Silva B, Moreno-Bueno G, Hergueta-Redondo M, Williams C, Garcia-Santos G, Ghajar C et al. (2012) Melanoma exosomes educate bone marrow progenitor cells toward a pro-metastatic phenotype through MET. Nat Med 18, 883891.
  • 84
    Baietti MF, Zhang Z, Mortier E, Melchior A, Degeest G, Geeraerts A, Ivarsson Y, Depoortere F, Coomans C, Vermeiren E et al. (2012) Syndecan–syntenin–ALIX regulates the biogenesis of exosomes. Nat Cell Biol 14, 677685.
  • 85
    Keller S, Konig AK, Marme F, Runz S, Wolterink S, Koensgen D, Mustea A, Sehouli J & Altevogt P (2009) Systemic presence and tumor-growth promoting effect of ovarian carcinoma released exosomes. Cancer Lett 278, 7381.
  • 86
    Casu B, Vlodavsky I & Sanderson RD (2008) Non-anticoagulant heparins and inhibition of cancer. Pathophysiol Haemost Thromb 36, 195203.
  • 87
    Coombe DR & Kett WC (2012) Heparin mimetics. Handb Exp Pharmacol 207, 361383.
  • 88
    Cochran S, Li C, Fairweather JK, Kett WC, Coombe DR & Ferro V (2003) Probing the interactions of phosphosulfomannans with angiogenic growth factors by surface plasmon resonance. J Med Chem 46, 46014608.
  • 89
    Liu CJ, Lee PH, Lin DY, Wu CC, Jeng LB, Lin PW, Mok KT, Lee WC, Yeh HZ, Ho MC et al. (2009) Heparanase inhibitor PI-88 as adjuvant therapy for hepatocellular carcinoma after curative resection: a randomized phase II trial for safety and optimal dosage. J Hepatol 50, 958968.
  • 90
    Dredge K, Hammond E, Handley P, Gonda TJ, Smith MT, Vincent C, Brandt R, Ferro V & Bytheway I (2011) PG545, a dual heparanase and angiogenesis inhibitor, induces potent anti-tumour and anti-metastatic efficacy in preclinical models. Br J Cancer 104, 635642.
  • 91
    Ferro V, Liu L, Johnstone KD, Wimmer N, Karoli T, Handley P, Rowley J, Dredge K, Li CP, Hammond E et al. (2012) Discovery of PG545: a highly potent and simultaneous inhibitor of angiogenesis, tumor growth, and metastasis. J Med Chem 55, 38043813.
  • 92
    Hammond E, Brandt R & Dredge K (2012) PG545, a heparan sulfate mimetic, reduces heparanase expression in vivo, blocks spontaneous metastases and enhances overall survival in the 4T1 breast carcinoma model. PLoS One 7, e52175.
  • 93
    Naggi A, Casu B, Perez M, Torri G, Cassinelli G, Penco S, Pisano C, Giannini G, Ishai-Michaeli R & Vlodavsky I (2005) Modulation of the heparanase-inhibiting activity of heparin through selective desulfation, graded N-acetylation, and glycol splitting. J Biol Chem 280, 1210312113.
  • 94
    Shafat I, Ben-Arush MW, Issakov J, Meller I, Naroditsky I, Tortoteto M, Cassinelli G, Lanzi C, Pisano C, Ilan N et al. (2011) Preclinical and clinical significance of heparanase in Ewing's sarcoma. J Cell Mol Med 15, 18571864.
  • 95
    Yang Y, MacLeod V, Dai Y, Khotskaya-Sample Y, Shriver Z, Venkataraman G, Sasisekharan R, Naggi A, Torri G, Casu B et al. (2007) The syndecan-1 heparan sulfate proteoglycan is a viable target for myeloma therapy. Blood 110, 20412048.
  • 96
    Ritchie JP, Ramani VC, Ren Y, Naggi A, Torri G, Casu B, Penco S, Pisano C, Carminati P, Tortoreto M et al. (2011) SST0001, a chemically modified heparin, inhibits myeloma growth and angiogenesis via disruption of the heparanase/syndecan-1 axis. Clin Cancer Res 17, 13821393.
  • 97
    Meirovitz A, Hermano E, Lerner I, Zcharia E, Pisano C, Peretz T & Elkin M (2011) Role of heparanase in radiation-enhanced invasiveness of pancreatic carcinoma. Cancer Res 71, 27722780.
  • 98
    Zhou H, Roy S, Cochran E, Zouaoui R, Chu CL, Duffner J, Zhao G, Smith S, Galcheva-Gargova Z, Karlgren J et al. (2011) M402, a novel heparan sulfate mimetic, targets multiple pathways implicated in tumor progression and metastasis. PLoS One 6, e21106.
  • 99
    Schmidt EP, Yang Y, Janssen WJ, Gandjeva A, Perez MJ, Barthel L, Zemans RL, Bowman JC, Koyanagi DE, Yunt ZX et al. (2012) The pulmonary endothelial glycocalyx regulates neutrophil adhesion and lung injury during experimental sepsis. Nat Med 18, 12171223.
  • 100
    Ziolkowski AF, Popp SK, Freeman C, Parish CR & Simeonovic CJ (2012) Heparan sulfate and heparanase play key roles in mouse beta cell survival and autoimmune diabetes. J Clin Invest 122, 132141.
  • 101
    Gil N, Goldberg R, Neuman T, Garsen M, Zcharia E, Rubinstein AM, van Kuppevelt T, Meirovitz A, Pisano C, Li JP et al. (2012) Heparanase is essential for the development of diabetic nephropathy in mice. Diabetes 61, 208216.
  • 102
    Tsuzuki Y, Nguyen TK, Garud DR, Kuberan B & Koketsu M (2010) 4-deoxy-4-fluoro-xyloside derivatives as inhibitors of glycosaminoglycan biosynthesis. Bioorg Med Chem Lett 20, 72697273.
  • 103
    Fritz TA, Lugemwa FN, Sarkar AK & Esko JD (1994) Biosynthesis of heparan sulfate on ß-D-xylosides depends on aglycone structure. J Biol Chem 269, 300307.
  • 104
    Beauvais DM, Ell BJ, McWhorter AR & Rapraeger AC (2009) Syndecan-1 regulates alphavbeta3 and alphavbeta5 integrin activation during angiogenesis and is blocked by synstatin, a novel peptide inhibitor. J Exp Med 206, 691705.
  • 105
    Beauvais DM & Rapraeger AC (2010) Syndecan-1 couples the insulin-like growth factor-1 receptor to inside-out integrin activation. J Cell Sci 123, 37963807.
  • 106
    Zhang L, Sullivan PS, Goodman JC, Gunaratne PH & Marchetti D (2011) MicroRNA-1258 suppresses breast cancer brain metastasis by targeting heparanase. Cancer Res 71, 645654.
  • 107
    Welton JL, Khanna S, Giles PJ, Brennan P, Brewis IA, Staffurth J, Mason MD & Clayton A (2010) Proteomics analysis of bladder cancer exosomes. Mol Cell Proteomics 9, 13241338.
  • 108
    Choi DS, Lee JM, Park GW, Lim HW, Bang JY, Kim YK, Kwon KH, Kwon HJ, Kim KP & Gho YS (2007) Proteomic analysis of microvesicles derived from human colorectal cancer cells. J Proteome Res 6, 46464655.
  • 109
    Gonzales PA, Pisitkun T, Hoffert JD, Tchapyjnikov D, Star RA, Kleta R, Wang NS & Knepper MA (2009) Large-scale proteomics and phosphoproteomics of urinary exosomes. J Am Soc Nephrol 20, 363379.
  • 110
    Mathivanan S, Lim JW, Tauro BJ, Ji H, Moritz RL & Simpson RJ (2010) Proteomics analysis of A33 immunoaffinity-purified exosomes released from the human colon tumor cell line LIM1215 reveals a tissue-specific protein signature. Mol Cell Proteomics 9, 197208.
  • 111
    Gonzalez-Begne M, Lu B, Han X, Hagen FK, Hand AR, Melvin JE & Yates JR (2009) Proteomic analysis of human parotid gland exosomes by multidimensional protein identification technology (MudPIT). J Proteome Res 8, 13041314.
  • 112
    Carayon K, Chaoui K, Ronzier E, Lazar I, Bertrand-Michel J, Roques V, Balor S, Terce F, Lopez A, Salome L et al. (2011) Proteolipidic composition of exosomes changes during reticulocyte maturation. J Biol Chem 286, 3442634439.
  • 113
    Valadi H, Ekstrom K, Bossios A, Sjostrand M, Lee JJ & Lotvall JO (2007) Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells. Nat Cell Biol 9, 654659.
  • 114
    Ji H, Erfani N, Tauro BJ, Kapp EA, Zhu HJ, Moritz RL, Lim JW & Simpson RJ (2008) Difference gel electrophoresis analysis of Ras-transformed fibroblast cell-derived exosomes. Electrophoresis 29, 26602671.
  • 115
    Thompson CA, Purushothaman A, Ramani VC, Vlodavsky I & Sanderson RD (2013) Heparanase regulates secretion, composition and function of tumor cell-derived exosomes. J Biol Chem, doi:10.1074/jbc.C112.444562.