Regulation of FGF-1 mitogenic activity by heparan sulfate oligosaccharides is dependent on specific structural features: differential requirements for the modulation of FGF-1 and FGF-2

Glycosaminoglycans exhibit distinct interactions and signaling with BMP2 according to their nature and localization

The role of glycosaminoglycans (GAGs) in modulating bone morphogenetic protein (BMP) signaling represents a recent and underexplored area. Conflicting reports suggest a dual effect: some indicate a positive influence, while others demonstrate a negative impact. This duality suggests that the localization of GAGs (either at the cell surface or within the extracellular matrix) or the specific type of GAG may dictate their signaling role. The precise sulfation patterns of heparan sulfate (HS) responsible for BMP2 binding remain elusive. BMP2 exhibits a preference for binding to HS over other GAGs. Using well-characterized biomaterials mimicking the extracellular matrix, our research reveals that HS promotes BMP2 signaling in the extracellular space, contrary to chondroitin sulfate (CS), which enhances BMP2 bioactivity at the cell surface. Further observations indicate that a central IdoA (2S)-GlcNS (6S) tri-sulfated motif within HS hexasaccharides enhances binding. Nevertheless, BMP2 exhibits a degree of adaptability to various HS sulfation types and sequences. Molecular dynamic simulations attribute this adaptability to the BMP2 N-terminal end flexibility. Our findings illustrate the complex interplay between GAGs and BMP signaling, highlighting the importance of localization and specific sulfation patterns. This understanding has implications for the development of biomaterials with tailored properties for therapeutic applications targeting BMP signaling pathways.

Galectin-3-binding protein inhibits extracellular heparan 6-O-endosulfatase Sulf-2

Human extracellular 6-O-endosulfatases Sulf-1 and Sulf-2 are the only enzymes that post-synthetically alter the 6-O sulfation of heparan sulfate proteoglycans (HSPG), which regulates interactions of HSPG with many proteins. Oncogenicity of Sulf-2 in different cancers has been documented and we have shown that Sulf-2 is associated with poor survival outcomes in head and neck squamous cell carcinoma (HNSCC). In spite of its importance, limited information is available on direct protein-protein interactions of the Sulf-2 protein in the tumor microenvironment. In this study, we used monoclonal antibody (mAb) affinity purification and mass spectrometry to identify galectin-3-binding protein (LG3BP) as a highly specific binding partner of Sulf-2 in the conditioned media of HNSCC cell lines. We validated their direct interaction in vitro using recombinant proteins and have shown that the chondroitin sulfate (CS) covalently bound to the Sulf-2 influences the binding to LG3BP. We confirmed importance of the CS chain for the interaction by generating a mutant Sulf-2 protein that lacks the CS. Importantly, we have shown that the LG3BP inhibits Sulf-2 activity in vitro in a concentration dependent manner. As a consequence, the addition of LG3BP to a spheroid cell culture inhibited invasion of the HNSCC cells into Matrigel. Thus, Sulf-2 interaction with LG3BP may regulate physiological activity of the Sulf-2 enzyme as well as its activity in the tumor microenvironment.

Heparan sulfate regulates amphiregulin signaling towards reparative lung mesenchymal cells during influenza A infection

Amphiregulin (Areg), a growth factor produced by regulatory T (Treg) cells to facilitate tissue repair/regeneration, contains a heparan sulfate (HS) binding domain. How HS, a highly sulfated glycan subtype that alters growth factor signaling, influences Areg repair/regeneration functions is unclear. Here we report that inhibition of HS in various cell lines and primary lung mesenchymal cells (LMC) qualitatively alters downstream signaling and highlights the existence of HS-dependent vs. -independent Areg transcriptional signatures. Utilizing a panel of cell lines with targeted deletions in HS synthesis-related genes, we found that the presence of the glypican family of heparan sulfate proteoglycans is critical for Areg signaling and confirmed this dependency in primary LMC by siRNA-mediated knockdown. Furthermore, in the context of influenza A (IAV) infection in vivo , we found that an Areg-responsive subset of reparative LMC upregulate glypican-4 and HS. Conditional deletion of HS primarily within this LMC subset resulted in reduced blood oxygen saturation following infection with IAV, with no changes in viral load. Finally, we found that co-culture of HS-knockout LMC with IAV-induced Treg cells results in reduced LMC responses. Collectively, this study reveals the essentiality of HS on a specific lung mesenchymal population as a mediator of Treg cell-derived Areg reparative signaling during IAV infection.

Sweet but Challenging: Tackling the Complexity of GAGs with Engineered Tailor-Made Biomaterials

Glycosaminoglycans (GAGs) play a crucial role in tissue homeostasis by regulating the activity and diffusion of bioactive molecules. Incorporating GAGs into biomaterials has emerged as a widely adopted strategy in medical applications, owing to their biocompatibility and ability to control the release of bioactive molecules. Nevertheless, immobilized GAGs on biomaterials can elicit distinct cellular responses compared to their soluble forms, underscoring the need to understand the interactions between GAG and bioactive molecules within engineered functional biomaterials. By controlling critical parameters such as GAG type, density, and sulfation, it becomes possible to precisely delineate GAG functions within a biomaterial context and to better mimic specific tissue properties, enabling tailored design of GAG-based biomaterials for specific medical applications. However, this requires access to pure and well-characterized GAG compounds, which remains challenging. This review focuses on different strategies for producing well-defined GAGs and explores high-throughput approaches employed to investigate GAG-growth factor interactions and to quantify cellular responses on GAG-based biomaterials. These automated methods hold considerable promise for improving the understanding of the diverse functions of GAGs. In perspective, the scientific community is encouraged to adopt a rational approach in designing GAG-based biomaterials, taking into account the in vivo properties of the targeted tissue for medical applications.

Galectin-3-binding protein inhibits extracellular heparan 6-O-endosulfatse Sulf-2

Human extracellular 6-O-endosulfatases Sulf-1 and Sulf-2 are the only enzymes that post-synthetically alter the 6-O sulfation of heparan sulfate proteoglycans (HSPG), which regulates interactions of HSPG with many proteins. Oncogenicity of Sulf-2 in different cancers has been documented and we have shown that Sulf-2 is associated with poor survival outcomes in head and neck squamous cell carcinoma (HNSCC). In spite of its importance, limited information is available on direct protein-protein interactions of the Sulf-2 protein in the tumor microenvironment. In this study, we used monoclonal antibody (mAb) affinity purification and mass spectrometry to identify galectin-3-binding protein (LG3BP) as a highly specific binding partner of Sulf-2 in the secretome of HNSCC cell lines. We validated their direct interaction in vitro using recombinant proteins and have shown that the chondroitin sulfate (CS) covalently bound to the Sulf-2 influences the binding to LG3BP. We confirmed importance of the CS chain for the interaction by generating a mutant Sulf-2 protein that lacks the CS. Importantly, we have shown that the LG3BP inhibits Sulf-2 activity in vitro in a concentration dependent manner. As a consequence, the addition of LG3BP to a spheroid cell culture inhibited invasion of the HNSCC cells into Matrigel. Thus, Sulf-2 interaction with LG3BP has functional relevance, and may regulate physiological activity of the Sulf-2 enzyme as well as its activity in the tumor microenvironment.

A 6-O-endosulfatase activity assay based on synthetic heparan sulfate oligomers

Sulf-2 is an extracellular heparan 6-O-endosulfatase involved in the postsynthetic editing of heparan sulfate (HS), which regulates many important biological processes. The activity of the Sulf-2 and its substrate specificity remain insufficiently characterized in spite of more than two decades of studies of this enzyme. This is due, in part, to the difficulties in the production and isolation of this highly modified protein and due to the lack of well-characterized synthetic substrates for the probing of its catalytic activity. We introduce synthetic HS oligosaccharides to fill this gap, and we use our recombinant Sulf-2 protein to show that a paranitrophenol (pNP)-labeled synthetic oligosaccharide allows a reliable quantification of its enzymatic activity. The substrate and products of the desulfation reaction are separated by ion exchange high-pressure liquid chromatography and quantified by UV absorbance. This simple assay allows the detection of the Sulf-2 activity at high sensitivity (nanograms of the enzyme) and specificity. The method also allowed us to measure the heparan 6-O-endosulfatase activity in biological samples as complex as the secretome of cancer cell lines. Our in vitro measurements show that the N-glycosylation of the Sulf-2 enzyme affects the activity of the enzyme and that phosphate ions substantially decrease the Sulf-2 enzymatic activity. This assay offers an efficient, sensitive, and specific measurement of the heparan 6-O-endosulfatase activity that could open avenues to in vivo activity measurements and improve our understanding of the enzymatic editing of the sulfation of heparan.

The Alterations and Roles of Glycosaminoglycans in Human Diseases

Glycosaminoglycans (GAGs) are a heterogeneous family of linear polysaccharides which are composed of a repeating disaccharide unit. They are also linked to core proteins to form proteoglycans (PGs). GAGs/PGs are major components of the cell surface and the extracellular matrix (ECM), and they display critical roles in development, normal function, and damage response in the body. Some properties (such as expression quantity, molecular weight, and sulfation pattern) of GAGs may be altered under pathological conditions. Due to the close connection between these properties and the function of GAGs/PGs, the alterations are often associated with enormous changes in the physiological/pathological status of cells and organs. Therefore, these GAGs/PGs may serve as marker molecules of disease. This review aimed to investigate the structural alterations and roles of GAGs/PGs in a range of diseases, such as atherosclerosis, cancer, diabetes, neurodegenerative disease, and virus infection. It is hoped to provide a reference for disease diagnosis, monitoring, prognosis, and drug development.

Innate Immunity in Mucopolysaccharide Diseases

Mucopolysaccharidoses are rare paediatric lysosomal storage disorders, characterised by accumulation of glycosaminoglycans within lysosomes. This is caused by deficiencies in lysosomal enzymes involved in degradation of these molecules. Dependent on disease, progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline, which is still a challenge for current therapies. The worsening of neuropathology, observed in patients following recovery from flu-like infections, suggests that inflammation is highly implicated in disease progression. This review provides an overview of the pathological features associated with the mucopolysaccharidoses and summarises current knowledge regarding the inflammatory responses observed in the central nervous system and periphery. We propose a model whereby progressive accumulation of glycosaminoglycans elicits an innate immune response, initiated by the Toll-like receptor 4 pathway, but also precipitated by secondary storage components. Its activation induces cells of the immune system to release pro-inflammatory cytokines, such as TNF-α and IL-1, which induce progression through chronic neuroinflammation. While TNF-α is mostly associated with bone and joint disease in mucopolysaccharidoses, increasing evidence implicates IL-1 as a main effector of innate immunity in the central nervous system. The (NOD)-like receptor protein 3 inflammasome is therefore implicated in chronic neuroinflammation and should be investigated further to identify novel anti-inflammatory treatments.

Sulfatase 2 (SULF2) Monoclonal Antibody 5D5 Suppresses Human Cholangiocarcinoma Xenograft Growth Through Regulation of a SULF2-Platelet-Derived Growth Factor Receptor Beta-Yes-Associated Protein Signaling Axis

BACKGROUND AND AIMS

Existing therapeutic approaches to treat cholangiocarcinoma (CCA) have limited effectiveness, prompting further study to develop therapies for CCA. We report a mechanistic role for the heparan sulfate editing enzyme sulfatase 2 (SULF2) in CCA pathogenesis.

APPROACH AND RESULTS

In silico analysis revealed elevated SULF2 expression in human CCA samples, occurring partly through gain of SULF2 copy number. We examined the effects of knockdown or overexpression of SULF2 on tumor growth, chemoresistance, and signaling pathway activity in human CCA cell lines in vitro. Up-regulation of SULF2 in CCA leads to increased platelet-derived growth factor receptor beta (PDGFRβ)-Yes-associated protein (YAP) signaling activity, promoting tumor growth and chemotherapy resistance. To explore the utility of targeting SULF2 in the tumor microenvironment for CCA treatment, we tested an anti-SULF2 mouse monoclonal antibody, 5D5, in a mouse CCA xenograft model. Targeting SULF2 by monoclonal antibody 5D5 inhibited PDGFRβ-YAP signaling and tumor growth in the mouse xenograft model.

CONCLUSIONS

These results suggest that SULF2 monoclonal antibody 5D5 or related agents may be potentially promising therapeutic agents in CCA.

Blockage of undesirable endocytosis of recombinant human growth/differentiation factor-5 in Chinese hamster ovary cell cultures requires heparin analogs with specific chain lengths

Cell surface heparan sulfate proteoglycan (HSPG)-mediated endocytosis lowers the yield of recombinant human bone morphogenetic proteins (rhBMPs), such as rhBMP-2 and rhBMP-4, from Chinese hamster ovary (CHO) cell cultures. Exogenous recombinant human growth/differentiation factor-5 (rhGDF-5), a member of the BMP family, bound to cell surface HSPGs and was actively internalized into CHO cells. Knockdown of heparan sulfate (HS) synthesis enzymes in CHO cells revealed that the chain length and N-sulfation of HS affected the binding of rhGDF-5 to HSPGs and subsequent rhGDF-5 internalization. To increase product yield by minimizing rhGDF-5 internalization in recombinant CHO (rCHO) cell cultures, heparin, and dextran sulfate (DS) of various polysaccharide chain lengths, which are structural analogs of HS, were examined for blockage of rhGDF-5 internalization. Heparin fragments of four monosaccharides (MW of 1.2 kDa) and DS (MW of 15 kDa) did not inhibit rhGDF-5 internalization whereas unfractionated heparin and DS of 200 kDa could significantly inhibit it. Compared to the control cultures, supplementation with unfractionated heparin or DS of 200 kDa at 1 g L^-1 resulted in more than a 10-fold increase in the maximum rhGDF-5 concentration. Taken together, the supplementation of structural HS analogs improved rhGDF-5 production in rCHO cell cultures by inhibiting rhGDF-5 internalization. GRAPHICAL ABSTRACT AND LAY SUMMARY: Cell surface heparan sulfate proteoglycan (HSPG)-mediated endocytosis lowers the yield of rhGDF-5 from CHO cell cultures. In this study, the authors found that the length and N-sulfation of HS chain determine the binding of rhGDF-5 to HSPGs and subsequent rhGDF-5 internalization. Based on this finding, the authors successfully used heparin analogs with specific chain lengths to enhance the rhGDF-5 yield by blocking rhGDF-5 internalization.

Sulfated syndecan 1 is critical to preventing cellular senescence by modulating fibroblast growth factor receptor endocytosis

Cellular senescence can be triggered by various intrinsic and extrinsic stimuli. We previously reported that silencing of 3'-phosphoadenosine 5'-phosphosulfate synthetase 2 (PAPSS2) induces cellular senescence through augmented fibroblast growth factor receptor 1 (FGFR1) signaling. However, the exact molecular mechanism connecting heparan sulfation and cellular senescence remains unclear. Here, we investigated the potential involvement of heparan sulfate proteoglycans (HSPGs) in augmented FGFR1 signaling and cellular senescence. Depletion of several types of HSPGs revealed that cells depleted of syndecan 1 (SDC1) exhibited typical senescence phenotypes, and those depleted of PAPSS2-, SDC1-, or heparan sulfate 2-O sulfotransferase 1 (HS2ST1) showed decreased FGFR1 internalization along with hyperresponsiveness to and prolonged activation of fibroblast growth factor 2 (FGF2)-stimulated FGFR1- v-akt murine thymoma viral oncogene homolog (AKT) signaling. Clathrin- and caveolin-mediated FGFR1 endocytosis contributed to cellular senescence through the FGFR1-AKT-p53-p21 signaling pathway. Dynasore treatment triggered senescence phenotypes, augmented FGFR1-AKT-p53-p21 signaling, and decreased SDC1 expression. Finally, the replicatively and prematurely senescent cells were characterized by decreases of SDC1 expression and FGFR1 internalization, and an increase in FGFR1-AKT-p53-p21 signaling. Together, our results demonstrate that properly sulfated SDC1 plays a critical role in preventing cellular senescence through the regulation of FGFR1 endocytosis.

Lack of miR-378 attenuates muscular dystrophy in mdx mice

The severity of Duchenne muscular dystrophy (DMD), an incurable disease caused by the lack of dystrophin, might be modulated by different factors, including miRNAs. Among them, miR-378 is considered of high importance for muscle biology, but intriguingly, its role in DMD and its murine model (mdx mice) has not been thoroughly addressed so far. Here, we demonstrate that dystrophic mice additionally globally lacking miR-378 (double-KO [dKO] animals) exhibited better physical performance and improved absolute muscle force compared with mdx mice. Accordingly, markers of muscle damage in serum were significantly decreased in dKO mice, accompanied by diminished inflammation, fibrosis, and reduced abundance of regenerating fibers within muscles. The lack of miR-378 also normalized the aggravated fusion of dystrophin-deficient muscle satellite cells (mSCs). RNA sequencing of gastrocnemius muscle transcriptome revealed fibroblast growth factor 1 (Fgf1) as one of the most significantly downregulated genes in mice devoid of miR-378, indicating FGF1 as one of the mediators of changes driven by the lack of miR-378. In conclusion, we suggest that targeting miR-378 has the potential to ameliorate DMD pathology.

Minimum structural requirements for BMP-2-binding of heparin oligosaccharides

Bone morphogenetic proteins (BMPs) are essential during tissue repair and remodeling after injury. Glycosaminoglycan (GAG) sugars are known to enhance BMP activity in vitro and in vivo; here the interactions of BMP-2 with various glycosaminoglycan classes were compared and shown to be selective for heparin over other comparable saccharides. The minimal chain lengths and specific sulfate moieties required for heparin-derived oligosaccharide binding to BMP-2, and the ability of such oligosaccharides to promote BMP-2-induced osteogenic differentiation in vitro were then determined. BMP-2 could bind to heparin hexasaccharides (dp6) and octasaccharides (dp8), but decasaccharides (dp10) were the minimum chain length required for both efficient binding of BMP-2 and consequent heparin-dependent cell responses. N-sulfation is the most important, and 6-O-sulfation moderately important for BMP-2 binding and activity, whereas 2-O-sulfation was much less critical. Bone formation assays in vivo further confirmed that dp10, N-sulfated heparin oligosaccharides were the minimal requirement for effective enhancement of BMP-2-induced bone formation. Such information is necessary for the rational design of the next generations of heparan-based devices for bone tissue repair.

Regenerative effects of peptide nanofibers in an experimental model of Parkinson's disease

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic nigrostriatal neurons and reduction in striatal dopamine levels. Although there are few treatment options for PD such as Levodopa, they are used just to relieve and modify the symptoms. There are no therapies available for PD to slow down the degeneration process in the brain and recover the lost function. In this study, we used extracellular matrix (ECM) mimetic peptide amphiphile (PA) nanofibers as a potential therapeutic approach in a PD rat model. We demonstrated the effect of heparan sulfate mimetic and laminin mimetic PA nanofibers on reducing striatal injury and enhancing functional recovery after unilateral striatal injection of 6-hydroxydopamine (6-OHDA). The bioactive self-assembled PA nanofibers significantly reduced forelimb asymmetry, contralateral forelimb akinesia and d-amphetamine-induced rotational behavior in cylinder, stepping and rotation tests, respectively, in 6-OHDA-lesioned rats after 6 weeks. The behavioral improvement with PA nanofiber administration was associated with enhanced striatal dopamine and tyrosine hydroxylase content as well as reduced cleaved-Caspase-3 levels. Histological assessment also showed that PA nanofiber injection to the striatum resulted in better tissue integrity compared to control groups. In addition, PA nanofibers reduced the progressive cell loss in SH-SY5Y cells caused by 6-OHDA treatment. These data showed that the bioactive peptide nanofibers improve neurochemical and behavioral consequences of Parkinsonism in rats and provide a promising new strategy for treatment of PD.

STATEMENT OF SIGNIFICANCE

Biomimetic nanomaterials bearing natural bioactive signals which are derived from extracellular matrix components like laminin and heparan sulfates provide promising therapeutic strategies for regeneration of the nervous system. However, no research has been reported exploring the use of biomimetic materials against degeneration in Parkinson's disease. In this work, we investigated potential therapeutic effects of heparan sulfate and laminin mimetic PA nanofibers on reduction of striatal injury in experimental Parkinson's disease model. PA nanofibers enhanced functional recovery associated with enhanced striatal dopamine and tyrosine hydroxylase content as well as reduced cleaved-Caspase-3 levels. Overall, this study shows the improvement in consequences of Parkinsonism in rats and provides a new platform for treatment of Parkinson's disease.

The "in and out" of glucosamine 6-O-sulfation: the 6th sense of heparan sulfate

The biological properties of Heparan sulfate (HS) polysaccharides essentially rely on their ability to bind and modulate a multitude of protein ligands. These interactions involve internal oligosaccharide sequences defined by their sulfation patterns. Amongst these, the 6-O-sulfation of HS contributes significantly to the polysaccharide structural diversity and is critically involved in the binding of many proteins. HS 6-O-sulfation is catalyzed by 6-O-sulfotransferases (6OSTs) during biosynthesis, and it is further modified by the post-synthetic action of 6-O-endosulfatases (Sulfs), two enzyme families that remain poorly characterized. The aim of the present review is to summarize the contribution of 6-O-sulfates in HS structure/function relationships and to discuss the present knowledge on the complex mechanisms regulating HS 6-O-sulfation.

Altering the Proteoglycan State of Transforming Growth Factor β Type III Receptor (TβRIII)/Betaglycan Modulates Canonical Wnt/β-Catenin Signaling

Hyperactive Wnt/β-catenin signaling is linked to cancer progression and developmental abnormalities, making identification of mechanisms controlling Wnt/β-catenin signaling vital. Transforming growth factor β type III receptor (TβRIII/betaglycan) is a transmembrane proteoglycan co-receptor that exists with or without heparan and/or chondroitin sulfate glycosaminoglycan (GAG) modifications in cells and has established roles in development and cancer. Our studies here demonstrate that TβRIII, independent of its TGFβ co-receptor function, regulates canonical Wnt3a signaling by controlling Wnt3a availability through its sulfated GAG chains. Our findings revealed, for the first time, opposing functions for the different GAG modifications on TβRIII suggesting that Wnt interactions with the TβRIII heparan sulfate chains result in inhibition of Wnt signaling, likely via Wnt sequestration, whereas the chondroitin sulfate GAG chains on TβRIII promote Wnt3a signaling. These studies identify a novel, dual role for TβRIII/betaglycan and define a key requirement for the balance between chondroitin sulfate and heparan sulfate chains in dictating ligand responses with implications for both development and cancer.

Sulfatase-2: a prognostic biomarker and candidate therapeutic target in patients with pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is the fifth most common cause of cancer death in the UK. Its poor prognosis is attributed to late detection and limited therapeutic options. Expression of SULF2, an endosulfatase that modulates heparan sulfate proteoglycan 6-O-sulfation and is reportedly tumourigenic in different types of cancer, was investigated.

METHODS

SULF2 expression was determined immunohistochemically in archival surgical resection tissue sections from 93 patients with a confirmed histological diagnosis of PDAC between 2002 and 2008 followed for a median of 9 years. Relationships with clinico-pathological parameters and patient survival were explored.

RESULTS

The majority of PDACs showed positive SULF2 staining in tumour cells and intratumoural or tumour-adjacent stroma. Greater than 25% SULF2-positive tumour cells was present in 60% of cancers and correlated with tumour stage (P=0.002) and perineural invasion (P=0.024). SULF2 intensity was scored moderate or strong in 81% of cancers and positively correlated with vascular invasion (P=0.015). High SULF2 expression, defined as >50% SULF2-positive tumour cells and strong SULF2 staining, was associated with shorter time to radiological progression (P=0.018, HR 1.98, CI 1.13-3.47). Similarly, by multivariate analysis, high SULF2 expression was independently associated with poorer survival (P=0.004, HR 2.10, CI 1.26-3.54), with a median survival of 11 months vs 21 months for lower PDAC SULF2.

CONCLUSIONS

Elevated SULF2 in PDAC was associated with advanced tumour stage, vascular invasion, shorter interval to radiological progression and shorter overall survival. SULF2 may have roles as a prognostic biomarker and as a therapeutic target for patients with PDAC.

Synthetic Site-Selectively Mono-6-O-Sulfated Heparan Sulfate Dodecasaccharide Shows Anti-Angiogenic Properties In Vitro and Sensitizes Tumors to Cisplatin In Vivo

Heparan sulphate (HS), a ubiquitously expressed glycosaminoglycan (GAG), regulates multiple cellular functions by mediating interactions between numerous growth factors and their cell surface cognate receptors. However, the structural specificity of HS in these interactions remains largely undefined. Here, we used completely synthetic, structurally defined, alternating N-sulfated glucosamine (NS) and 2-O-sulfated iduronate (IS) residues to generate dodecasaccharides ([NSIS]₆) that contained no, one or six glucosamine 6-O-sulfates (6S). The aim was to address how 6S contributes to the potential of defined HS dodecasaccharides to inhibit the angiogenic growth factors FGF2 and VEGF₁₆₅, in vitro and in vivo. We show that the addition of a single 6S at the non-reducing end of [NSIS]₆, i.e. [NSIS6S]-[NSIS]₅, significantly augments the inhibition of FGF2-dependent endothelial cell proliferation, migration and sprouting in vitro when compared to the non-6S variant. In contrast, the fully 6-O-sulfated dodecasaccharide, [NSIS6S]₆, is not a potent inhibitor of FGF2. Addition of a single 6S did not significantly improve inhibitory properties of [NSIS]₆ when tested against VEGF₁₆₅-dependent endothelial cell functions.In vivo, [NSIS6S]-[NSIS]₅ blocked FGF2-dependent blood vessel formation without affecting tumor growth. Reduction of non-FGF2-dependent ovarian tumor growth occurred when [NSIS6S]-[NSIS]₅ was combined with cisplatin. The degree of inhibition by [NSIS6S]-[NSIS]₅ in combination with cisplatin in vivo equated with that induced by bevacizumab and sunitinib when administered with cisplatin. Evaluation of post-treatment vasculature revealed that [NSIS6S]-[NSIS]₅ treatment had the greatest impact on tumor blood vessel size and lumen formation. Our data for the first time demonstrate that synthetic, structurally defined oligosaccharides have potential to be developed as active anti-angiogenic agents that sensitize tumors to chemotherapeutic agents.

Biological Effects of Heparan Sulfates and Regioselectively Modified Heparin-Heparan Mimetics

The heparan sulfates (HS) are structurally the most complex but information rich biopolymers known. They are composed of polysaccharides containing regioselectively distributed carboxyl, sulfate ester, acetyl, amino, and N-sulfonyl groups with sequence- and domain-like arrangements. HS are found ubiquitously on cell surfaces and in extracellular matrices where they are covalently anchored via restricted protein cores. They modulate numerous development cell processes and the pathology of living organisms. HS concentration is extremely low on endothelial cell surfaces (1 pmol/cm2), therefore, they are difficult to isolate and evaluate. Furthermore, their sequence variability is extremely high and the sequence analysis is in its infancy. HS acts as a low affinity receptor which plays a central role in the reception and modulation of a wide range of effector proteins such as growth factors, morphogens, chemokines, enzymes, protease inhibitors.

Water soluble fragments of HS and heparin (HE) enzymatically released or synthetic sequences, analogs of heparinoids and heparanoids (HH) mimetics regioselectively modified oligo- and polysaccharides with HE/HS like functional groups, and nonsaccharide containing structures can modulate effector proteins and influence some of the development and pathological processes. Modulation effects are described for anticoagulant antiproliferative properties, for reducing platelet and plasma protein adhesion as well as inhibition or activating growth factors by the influence of HH mimetics. The advantage of defined high molecular weight substrates are discussed and compared to the low molecular weight mimetics. The potential of HH mimetics opens new approaches and strategies for therapeutic treatment.

Heparan sulfate and heparin interactions with proteins

Heparan sulfate (HS) polysaccharides are ubiquitous components of the cell surface and extracellular matrix of all multicellular animals, whereas heparin is present within mast cells and can be viewed as a more sulfated, tissue-specific, HS variant. HS and heparin regulate biological processes through interactions with a large repertoire of proteins. Owing to these interactions and diverse effects observed during in vitro, ex vivo and in vivo experiments, manifold biological/pharmacological activities have been attributed to them. The properties that have been thought to bestow protein binding and biological activity upon HS and heparin vary from high levels of sequence specificity to a dependence on charge. In contrast to these opposing opinions, we will argue that the evidence supports both a level of redundancy and a degree of selectivity in the structure-activity relationship. The relationship between this apparent redundancy, the multi-dentate nature of heparin and HS polysaccharide chains, their involvement in protein networks and the multiple binding sites on proteins, each possessing different properties, will also be considered. Finally, the role of cations in modulating HS/heparin activity will be reviewed and some of the implications for structure-activity relationships and regulation will be discussed.

Fibroblast growth factor receptor 3 isoforms: Novel therapeutic targets for hepatocellular carcinoma?

Fibroblast growth factor receptors (FGFRs) are frequently up-regulated in subsets of hepatocellular carcinoma (HCC). Here, we provide mechanistic insight that FGFR3 splice variants IIIb and IIIc impact considerably on the malignant phenotype of HCC cells. The occurrence of FGFR3 variants was analyzed in human HCC samples. In hepatoma/hepatocarcinoma cell lines, FGFR3 isoforms were overexpressed by lentiviral constructs or down-modulated by small interfering RNA (siRNA; affecting FGFR3-IIIb and -IIIc) or an adenoviral kinase-dead FGFR3-IIIc construct (kdFGFR3). Elevated levels of FGFR3-IIIb and/or -IIIc were found in 53% of HCC cases. FGFR3-IIIb overexpression occurred significantly more often in primary tumors of large (pT2-4) than of small size (pT1). Furthermore, one or both isoforms were enhanced mostly in cases with early tumor infiltration and/or recurrence at the time of surgery or follow-up examinations. In hepatoma/hepatocarcinoma cells, up-regulated FGFR3-IIIb conferred an enhanced capability for proliferation. Both FGFR3-IIIb and FGFR3-IIIc suppressed apoptotic activity, enhanced clonogenic growth, and induced disintegration of the blood/lymph endothelium. The tumorigenicity of cells in severe combined immunodeficiency mice was augmented to a larger degree by variant IIIb than by IIIc. Conversely, siRNA targeting FGFR3 and kdFGFR3 reduced clonogenicity, anchorage-independent growth, and disintegration of the blood/lymph endothelium in vitro. Furthermore, kdFGFR3 strongly attenuated tumor formation in vivo.

CONCLUSIONS

Deregulated FGFR3 variants exhibit specific effects in the malignant progression of HCC cells. Accordingly, blockade of FGFR3-mediated signaling may be a promising therapeutic approach to antagonize growth and malignant behavior of HCC cells.

Heparan sulfation is essential for the prevention of cellular senescence

Cellular senescence is considered as an important tumor-suppressive mechanism. Here, we demonstrated that heparan sulfate (HS) prevents cellular senescence by fine-tuning of the fibroblast growth factor receptor (FGFR) signaling pathway. We found that depletion of 3'-phosphoadenosine 5'-phosphosulfate synthetase 2 (PAPSS2), a synthetic enzyme of the sulfur donor PAPS, led to premature cell senescence in various cancer cells and in a xenograft tumor mouse model. Sodium chlorate, a metabolic inhibitor of HS sulfation also induced a cellular senescence phenotype. p53 and p21 accumulation was essential for PAPSS2-mediated cellular senescence. Such senescence phenotypes were closely correlated with cell surface HS levels in both cancer cells and human diploid fibroblasts. The determination of the activation of receptors such as FGFR1, Met, and insulin growth factor 1 receptor β indicated that the augmented FGFR1/AKT signaling was specifically involved in premature senescence in a HS-dependent manner. Thus, blockade of either FGFR1 or AKT prohibited p53 and p21 accumulation and cell fate switched from cellular senescence to apoptosis. In particular, desulfation at the 2-O position in the HS chain contributed to the premature senescence via the augmented FGFR1 signaling. Taken together, we reveal, for the first time, that the proper status of HS is essential for the prevention of cellular senescence. These observations allowed us to hypothesize that the FGF/FGFR signaling system could initiate novel tumor defenses through regulating premature senescence.

The development of anti-angiogenic heparan sulfate oligosaccharides

Angiogenesis has emerged as a novel target for anti-cancer therapies through randomized clinical trials that tested the benefit of adding vascular endothelial growth factor (VEGF) inhibitors to conventional cytotoxic therapies. However, despite improvements in the progression-free survival, the benefit in overall survival is modest. Tumour angiogenesis is regulated by a number of angiogenic cytokines. Thus innate or acquired resistance to VEGF inhibitors can be caused, at least in part, through expression of other angiogenic cytokines, including fibroblast growth factor 2 (FGF2), interleukin 8 (IL-8) and stromal-cell-derived factor 1α (SDF-1α), which make tumours insensitive to VEGF signalling pathway inhibition. The majority of angiogenic cytokines, including VEGF-A, FGF2, IL-8 and SDF-1α, manifest an obligate dependence on heparan sulfate (HS) for their biological activity. This mandatory requirement of angiogenic cytokines for HS identifies HS as a potential target for novel anti-angiogenic therapy. Targeting multiple angiogenic cytokines with HS mimetics may represent an opportunity to inhibit tumour angiogenesis more efficiently. Our published studies and unpublished work have demonstrated the feasibility of generating synthetic HS fragments of defined structure with biological activity against a number of angiogenic cytokines.

Ovarian cancer cell heparan sulfate 6-O-sulfotransferases regulate an angiogenic program induced by heparin-binding epidermal growth factor (EGF)-like growth factor/EGF receptor signaling

Heparan sulfate (HS) is a component of cell surface and extracellular matrix proteoglycans that regulates numerous signaling pathways by binding and activating multiple growth factors and chemokines. The amount and pattern of HS sulfation are key determinants for the assembly of the trimolecular, HS-growth factor-receptor, signaling complex. Here we demonstrate that HS 6-O-sulfotransferases 1 and 2 (HS6ST-1 and HS6ST-2), which perform sulfation at 6-O position in glucosamine in HS, impact ovarian cancer angiogenesis through the HS-dependent HB-EGF/EGFR axis that subsequently modulates the expression of multiple angiogenic cytokines. Down-regulation of HS6ST-1 or HS6ST-2 in human ovarian cancer cell lines results in 30-50% reduction in glucosamine 6-O-sulfate levels in HS, impairing HB-EGF-dependent EGFR signaling and diminishing FGF2, IL-6, and IL-8 mRNA and protein levels in cancer cells. These cancer cell-related changes reduce endothelial cell signaling and tubule formation in vitro. In vivo, the development of subcutaneous tumor nodules with reduced 6-O-sulfation is significantly delayed at the initial stages of tumor establishment with further reduction in angiogenesis occurring throughout tumor growth. Our results show that in addition to the critical role that 6-O-sulfate moieties play in angiogenic cytokine activation, HS 6-O-sulfation level, determined by the expression of HS6ST isoforms in ovarian cancer cells, is a major regulator of angiogenic program in ovarian cancer cells impacting HB-EGF signaling and subsequent expression of angiogenic cytokines by cancer cells.

Post-Synthetic Regulation of HS Structure: The Yin and Yang of the Sulfs in Cancer

Heparan sulfate (HS) is a complex polysaccharide that takes part in most major cellular processes, through its ability to bind and modulate a very large array of proteins. These interactions involve saccharide domains of specific sulfation pattern (S-domains), the assembly of which is tightly orchestrated by a highly regulated biosynthesis machinery. Another level of structural control does also take place at the cell surface, where degrading enzymes further modify HS post-synthetically. Amongst them are the Sulfs, a family of extracellular sulfatases (two isoforms in human) that catalyze the specific 6-O-desulfation of HS. By targeting HS functional sulfated domains, Sulfs dramatically alter its ligand binding properties, thereby modulating a broad range of signaling pathways. Consequently, Sulfs play major roles during development, as well as in tissue homeostasis and repair. Sulfs have also been associated with many pathologies including cancer, but despite increasing interest, the role of Sulfs in tumor development still remains unclear. Studies have been hindered by a poor understanding of the Sulf enzymatic activities and conflicting data have shown either anti-oncogenic or tumor-promoting effects of these enzymes, depending on the tumor models analyzed. These opposite effects clearly illustrate the fine tuning of HS functions by the Sulfs, and the need to clarify the mechanisms involved. In this review, we will detail the present knowledge on the structural and functional properties of the Sulfs, with a special focus on their implication during tumor progression. Finally, we will discuss attempts and perspectives of using the Sulfs as a biomarker of cancer prognosis and diagnostic and as a target for anti-cancer therapies.

The association of arylendosulfatase 1 (SULF1) gene polymorphism with recurrent miscarriage

PURPOSE

One of the most common problems in reproductive medicine is recurrent miscarriage (RM). There is increasing evidence showing genetic susceptibility of women is an important risk factor in the occurrence of RM. In recent years, there is a growing interest in sulfate and its role in fetal development. A novel mechanism of SULF1 has been demonstrated for modifying the activities of some growth factors and signalling molecules that have major roles during embryogenesis. The aim of present study was to evaluate the association of SULF1 gene polymorphism (rs6990375 G > A) in Iranian patients with RM.

METHODS

We established a case-control study of 200 Iranian women: 100 patients with the history of two or more RM as cases and 100 healthy women with at least two cases of successful pregnancy and no history of miscarriage as controls. The polymorphism was examined by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method.

RESULTS

The genotypic analysis between case and controls showed significant differences (p-value = 0.000). Allelic analysis showed no significant correlation (Χ2 = 3.36, p-value = 0.066). The heterozygous genetic variant was significantly higher among healthy women (OR = 12.67, 95% CI = 6.47-24.79).

CONCLUSIONS

Our data showed that rs6990375 polymorphism of SULF1 gene could be among one of the factors related to RM in Iranian women. Further evaluation of this polymorphism may be important and need further studies.

SULF1 inhibits proliferation and invasion of esophageal squamous cell carcinoma cells by decreasing heparin-binding growth factor signaling

BACKGROUND

Heparin-binding growth factor signaling is involved in the pathogenesis and development of human cancers. It can be regulated by sulfation of cell-surface heparan sulfate proteoglycans (HSPG). SULF1 is a heparin-degrading endosulfatase which can modulate the sulfation of HSPGs.

AIM

The purpose of this study was to elucidate the role of SULF1 in modulating proliferation and invasion of esophageal squamous cell carcinoma (ESCC) by decreasing heparin-binding growth factor signaling.

METHODS

We restored SULF1 expression in the ESCC cell line KYSE150, and examined the effects of SULF1 expression on the proliferation and invasion of KYSE150 cells. In addition, we investigated the expression of SULF1 in human ESCC tissues and analyzed the correlation of SULF1 expression with clinicopathologic characteristics of ESCC.

RESULTS

Our study shows that re-expression of SULF1 in ESCC cell line results in the downregulation of hepatocyte growth factor-mediated activation of MAPK pathways with a resultant decrease in cell invasiveness. Cell proliferation was also inhibited in SULF1-transfected KYSE150 cells. Immunohistochemical assays reveal that SULF1 is expressed in nearly half of the human ESCC tissues but not in normal esophageal epithelial cells. SULF1 expression in human ESCC tissues is negatively correlated with tumor size and tumor invasion.

CONCLUSION

This study identified that SULF1 inhibits proliferation and invasion of ESCC by decreasing heparin-binding growth factor signaling and suggested that SULF1 plays an inhibiting role in the pathogenesis of ESCC.

HSulf sulfatases catalyze processive and oriented 6-O-desulfation of heparan sulfate that differentially regulates fibroblast growth factor activity

Sulfs are extracellular sulfatases that have emerged recently as critical regulators of heparan sulfate (HS) activities through their ability to catalyze specific 6-O-desulfation of the polysaccharide. Consequently, Sulfs have been involved in many physiological and pathological processes, and notably for Sulf-2, in the development of cancers with poor prognosis. Despite growing interest, little is known about the structure and activity of these enzymes and the way they induce dynamic remodeling of HS 6-O-sulfation status. Here, we have combined an array of analytical approaches, including mass spectrometry, NMR, HS oligosaccharide sequencing, and FACS, to dissect HSulf-2 sulfatase activity, either on a purified octasaccharide used as a mimic of HS functional domains, or on intact cell-surface HS chains. In parallel, we have studied the functional consequences of HSulf-2 activity on fibroblast growth factor (FGF)-induced mitogenesis and found that the enzyme could differentially regulate FGF1 and FGF2 activities. Notably, these data supported the existence of precise 6-O-sulfation patterns for FGF activation and provided new insights into the saccharide structures involved. Altogether, our data bring to light an original processive enzymatic mechanism, by which HSulfs catalyze oriented alteration of HS 6-O-desulfation patterns and direct fine and differential regulation of HS functions.

Improving the cardio protective effect of aFGF in ischemic myocardium with ultrasound-mediated cavitation of heparin modified microbubbles: preliminary experiment

Ultrasound (US)-mediated cavitation of microbubbles has evolved into a new tool for organ-specific gene and drug delivery. This paper was to investigate the feasibility of acidic fibroblast growth factor (aFGF) intravenous delivery to the ischemic myocardium of rats by ultrasonic microbubbles modified with heparin. Heparin modified microbubbles (HMB) were prepared by the freeze-dried method. Acute myocardial infarction (AMI) model was established and the cardio protective effect of the aFGF combing with HMB (aFGF-HMB) under US-mediated cavitation technique was investigated. aFGF-HMB combined with US-mediated cavitation technique was examined by ECG. Ejection fraction (EF), fractional shortening (FS) and left ventricular diastolic diameter (LVDd) were measured to monitor the improvement of global myocardial contractile function. Myocardial tissue was stained with hematoxylin and eosine (HE) to evaluate the elaborate general morphology of the ischemic myocardium. From morphologic observation and echocardiography in rat heart, aFGF-HMB had suitable size distribution, physical stability and good acoustic resonance function. From AMI rat experiments, aFGF-HMB under US-mediated cavitation technique exerted aFGF cardio protective effect in ischemic myocardium. From histological evaluation, US-mediated cavitation of aFGF-HMB showed improvement of myocardial ischemia. With the visual imaging and US-triggered drug release advantages, US-mediated cavitation of aFGF-HMB might be developed as a novel technique for targeting delivery of aFGF into ischemic myocardium.

The human sulfatase 2 inhibitor 2,4-disulfonylphenyl-tert-butylnitrone (OKN-007) has an antitumor effect in hepatocellular carcinoma mediated via suppression of TGFB1/SMAD2 and Hedgehog/GLI1 signaling

Human sulfatase 2 (SULF2) functions as an oncoprotein in hepatocellular carcinoma (HCC) development by promoting tumor growth and metastasis via enhancement of fibroblast growth factor-2/extracellular signal-regulated kinase and WNT/β-catenin signaling. Recent results implicate that SULF2 activates the transforming growth factor beta (TGFB) and Hedgehog/GLI1 pathways in HCC. OKN-007 is a novel phenyl-sulfonyl compound that inhibits the enzymatic activity of SULF2. To investigate the antitumor effect of OKN-007 in HCC, we treated Huh7 cells, which express high levels of SULF2, with OKN-007 and found that it significantly promoted tumor cell apoptosis and inhibited cell proliferation, viability, and migration. To understand the action of OKN-007 on SULF2, we used Huh7 cells which normally express SULF2 and Hep3B cells that do not normally express SULF2. Utilizing Huh7 cells transfected with short hairpin RNA targeting SULF2 and transfection of Hep3B cells with a SULF2 plasmid to enhance SULF2 expression, we showed that the antitumor activity of OKN-007 was more pronounced in cells expressing SULF2. Furthermore, in vivo experiments verified that OKN-007 repressed tumor growth significantly. These results identify SULF2 as an important target of the antitumor effect of OKN-007. To determine the molecular mechanism of the antitumor effect of OKN-007, both TGFB1/SMAD and Hedgehog/GLI1 signaling pathway activity were measured by Western blot and SMAD- or GLI-reporter luciferase assays. We found that both signaling pathways were inhibited by OKN-007. Together, these results show that OKN-007 can suppress TGFB1/SMAD and Hedgehog/GLI1 signaling via its inhibition of SULF2 enzymatic activity. We conclude that OKN-007 or more potent derivatives may be promising agents for the treatment of HCC.

HSULF-1 inhibits ERK and AKT signaling and decreases cell viability in vitro in human lung epithelial cells

BACKGROUND

Heparan sulfate proteoglycans (HSPGs) modulate the binding and activation of signaling pathways of specific growth factors, such as fibroblast growth factor-2 (FGF-2). Human endosulfatase 1 (HSULF-1) is an enzyme that selectively removes 6-O sulfate groups from HS side chains and alter their level and pattern of sulfation and thus biological activity. It is known that HSULF-1 is expressed at low levels in some cancer cell lines and its enhanced expression can inhibit cancer cell growth or induce apoptosis, but the mechanism(s) involved has not been identified.

METHODS

HSULF-1 mRNA expression was assessed in five normal cells (primary human lung alveolar type 2 (hAT2) cells, adult lung fibroblasts (16Lu), fetal lung fibroblasts (HFL), human bronchial epithelial cells (HBE), and primary human lung fibroblasts (HLF)) and five lung cancer cell lines (A549, H292, H1975, H661, and H1703) using quantitative real time polymerase chain reaction (qRT-PCR). H292 and hAT2 cells over-expressing HSULF-1 were analyzed for cell viability, apoptosis, and ERK/Akt signaling, by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) assay, and Western Blot, respectively. Apoptosis pathway activation was confirmed by PCR array in hAT2, H292, and A549 cells.

RESULTS

HSULF-1 was expressed at a significantly lower level in epithelial cancer cell lines compared to normal cells. Infection with recombinant adenovirus for HSULF-1 over-expression resulted in decreased cell viability in H292 cells, but not in normal hAT2 cells. HSULF-1 over-expression induced apoptosis in H292 cells, but not in hAT2 cells. In addition, apoptosis pathways were activated in both H292 and A549 cells, but not in hAT2 cells. HSULF-1 over-expression reduced ERK and Akt signaling activation in H292 cells, which further demonstrated its inhibitory effects on signaling related to proliferation.

CONCLUSIONS

These results indicate that HSULF-1 is expressed at lower levels in H292 lung cancer cells than in normal human alveolar cells and that its over-expression reduced cell viability in H292 cells by inducing apoptotic pathways, at least in part by inhibiting ERK/Akt signaling. We hypothesize that HSULF-1 plays important roles in cancer cells and functions to modify cell signaling, inhibit cancer proliferation, and promote cancer cell death.

Syndecan-4 is associated with beta-cells in the pancreas and the MIN6 beta-cell line

Basement membranes (BM) in the pancreatic islet are important for islet survival and function, but supplementation of isolated islets with these components have had limited success. Currently, little is understood about which BM components and proteoglycans are essential to maintaining islet homeostasis. This study therefore aimed to characterize the BM components and proteoglycans of the islet in the mouse, rat and rabbit species. The BM of the mouse islet was varied in continuity around the islet and was discontinuous in the rat and rabbit islets. The BM consisted of collagen IV, laminin, fibronectin and perlecan in the mouse and was in tight association with the underlying islet endothelium. None of these components were found directly associated with the β-cells in tissue and in the MIN6 β-cell line. In contrast, heparan sulfate (HS) was distributed throughout the islet in all three species in a pattern distinctly different to that of perlecan and was observed mainly on the β-cells and not the α-cells in the mouse and rat. Similarly, syndecan-4 showed a staining pattern almost identical to that of HS and was mostly observed on the β-cells, not α-cells, in the mouse and rat. Both HS and syndecan-4 were also observed in the MIN6 β-cell line. The mouse islet and MIN6 syndecan-4 were both ~37 kDa in size, after deglycosylation with heparitinase. These results indicate that syndecan-4 may play an important role in β-cell function and that the cell-surface HS proteoglycans may be the missing link to maintaining islet longevity after isolation.

Modeling neuronal defects associated with a lysosomal disorder using patient-derived induced pluripotent stem cells

By providing access to affected neurons, human induced pluripotent stem cells (iPSc) offer a unique opportunity to model human neurodegenerative diseases. We generated human iPSc from the skin fibroblasts of children with mucopolysaccharidosis type IIIB. In this fatal lysosomal storage disease, defective α-N-acetylglucosaminidase interrupts the degradation of heparan sulfate (HS) proteoglycans and induces cell disorders predominating in the central nervous system, causing relentless progression toward severe mental retardation. Partially digested proteoglycans, which affect fibroblast growth factor signaling, accumulated in patient cells. They impaired isolation of emerging iPSc unless exogenous supply of the missing enzyme cleared storage and restored cell proliferation. After several passages, patient iPSc starved of an exogenous enzyme continued to proliferate in the presence of fibroblast growth factor despite HS accumulation. Survival and neural differentiation of patient iPSc were comparable with unaffected controls. Whereas cell pathology was modest in floating neurosphere cultures, undifferentiated patient iPSc and their neuronal progeny expressed cell disorders consisting of storage vesicles and severe disorganization of Golgi ribbons associated with modified expression of the Golgi matrix protein GM130. Gene expression profiling in neural stem cells pointed to alterations of extracellular matrix constituents and cell-matrix interactions, whereas genes associated with lysosome or Golgi apparatus functions were downregulated. Taken together, these results suggest defective responses of patient undifferentiated stem cells and neurons to environmental cues, which possibly affect Golgi organization, cell migration and neuritogenesis. This could have potential consequences on post-natal neurological development, once HS proteoglycan accumulation becomes prominent in the affected child brain.

Influencing hematopoietic differentiation of mouse embryonic stem cells using soluble heparin and heparan sulfate saccharides

Heparan sulfate proteoglycans (HSPG) encompass some of the most abundant macromolecules on the surface of almost every cell type. Heparan sulfate (HS) chains provide a key interaction surface for the binding of numerous proteins such as growth factors and morphogens, helping to define the ability of a cell to respond selectively to environmental cues. The specificity of HS-protein interactions are governed predominantly by the order and positioning of sulfate groups, with distinct cell types expressing unique sets of HS epitopes. Embryos deficient in HS-synthesis (Ext1(-/-)) exhibit pre-gastrulation lethality and lack recognizable organized mesoderm and extraembryonic tissues. Here we demonstrate that embryonic stem cells (ESCs) derived from Ext1(-/-) embryos are unable to differentiate into hematopoietic lineages, instead retaining ESC marker expression throughout embryoid body (EB) culture. However hematopoietic differentiation can be restored by the addition of soluble heparin. Consistent with specific size and composition requirements for HS:growth factor signaling, chains measuring at least 12 saccharides were required for partial rescue of hematopoiesis with longer chains (18 saccharides or more) required for complete rescue. Critically N- and 6-O-sulfate groups were essential for rescue. Heparin addition restored the activity of multiple signaling pathways including bone morphogenic protein (BMP) with activation of phospho-SMADs re-established by the addition of heparin. Heparin addition to wild-type cultures also altered the outcome of differentiation, promoting hematopoiesis at low concentrations, yet inhibiting blood formation at high concentrations. Thus altering the levels of HS and HS sulfation within differentiating ESC cultures provides an attractive and accessible mechanism for influencing cell fate.

Polymorphisms in the SULF1 gene are associated with early age of onset and survival of ovarian cancer

BACKGROUND

SULF1 (sulfatase 1) selectively removes the 6-O-sulphate group from heparan sulfate, changing the binding sites for extracellular growth factors. SULF1 expression has been reported to be decreased in various cancers, including ovarian cancer. We hypothesized that single nucleotide polymorphisms (SNPs) of SULF1 would impact clinicopathologic characteristics.

METHODS

We genotyped five common (minor allele frequency>0.05) regulatory SNPs with predicted functionalities (rs2623047 G>A, rs13264163 A>G, rs6990375 G>A, rs3802278 G>A, and rs3087714 C>T) in 168 patients with primary epithelial ovarian cancer, using the polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

We found that rs2623047 G>A was significantly associated with an early age of onset of ovarian cancer in the G allele dose-response manner (P = 0.027; Ptrend = 0.007) and that rs2623047 GG/GA genotypes were associated with longer progression-free survival; rs6990375 G>A was also associated with the early age of onset in the A allele dose-response manner (P = 0.013; Ptrend= 0.009). The significant differences in age of disease onset persisted among carriers of haplotypes of rs2623047 and rs6990375 (P = 0.014; Ptrend = 0.004). In luciferase reporter gene assays, rs2623047 G allele showed a slightly higher promoter activity than the A allele in the SKOV3 tumorigenic cell line.

CONCLUSIONS

These findings suggest that genetic variations in SULF1 may play a role in ovarian cancer onset and prognosis. Further studies with large sample sizes and of the mechanistic relevance of SULF1 SNPs are warranted.

Synthetic heparan sulfate oligosaccharides inhibit endothelial cell functions essential for angiogenesis

Background

Heparan sulfate (HS) is an important regulator of the assembly and activity of various angiogenic signalling complexes. However, the significance of precisely defined HS structures in regulating cytokine-dependent angiogenic cellular functions and signalling through receptors regulating angiogenic responses remains unclear. Understanding such structure-activity relationships is important for the rational design of HS fragments that inhibit HS-dependent angiogenic signalling complexes.

Methodology/Principal Findings

We synthesized a series of HS oligosaccharides ranging from 7 to 12 saccharide residues that contained a repeating disaccharide unit consisting of iduronate 2-O-sulfate linked to glucosamine with or without N-sulfate. The ability of oligosaccharides to compete with HS for FGF2 and VEGF₁₆₅ binding significantly increased with oligosaccharide length and sulfation. Correspondingly, the inhibitory potential of oligosaccharides against FGF2- and VEGF₁₆₅-induced endothelial cell responses was greater in longer oligosaccharide species that were comprised of disaccharides bearing both 2-O- and N-sulfation (2SNS). FGF2- and VEGF₁₆₅-induced endothelial cell migration were inhibited by longer 2SNS oligosaccharide species with 2SNS dodecasaccharide activity being comparable to that of receptor tyrosine kinase inhibitors targeting FGFR or VEGFR-2. Moreover, the 2SNS dodecasaccharide ablated FGF2- or VEGF₁₆₅-induced phosphorylation of FAK and assembly of F-actin in peripheral lamellipodia-like structures. In contrast, FGF2-induced endothelial cell proliferation was only moderately inhibited by longer 2SNS oligosaccharides. Inhibition of FGF2- and VEGF₁₆₅-dependent endothelial tube formation strongly correlated with oligosaccharide length and sulfation with 10-mer and 12-mer 2SNS oligosaccharides being the most potent species. FGF2- and VEGF₁₆₅-induced activation of MAPK pathway was inhibited by biologically active oligosaccharides correlating with the specific phosphorylation events in FRS2 and VEGFR-2, respectively.

Conclusion/Significance

These results demonstrate structure-function relationships for synthetic HS saccharides that suppress endothelial cell migration, tube formation and signalling induced by key angiogenic cytokines.

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

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

A murine model of Denys-Drash syndrome reveals novel transcriptional targets of WT1 in podocytes

The Wilms tumor-suppressor gene WT1, a key player in renal development, also has a crucial role in maintenance of the glomerulus in the mature kidney. However, molecular pathways orchestrated by WT1 in podocytes, where it is highly expressed, remain unknown. Their defects are thought to modify the cross-talk between podocytes and other glomerular cells and ultimately lead to glomerular sclerosis, as observed in diffuse mesangial sclerosis (DMS) a nephropathy associated with WT1 mutations. To identify podocyte WT1 targets, we generated a novel DMS mouse line, performed gene expression profiling in isolated glomeruli and identified excellent candidates that may modify podocyte differentiation and growth factor signaling in glomeruli. Scel, encoding sciellin, a protein of the cornified envelope in the skin, and Sulf1, encoding a 6-O endosulfatase, are shown to be expressed in wild-type podocytes and to be strongly down-regulated in mutants. Co-expression of Wt1, Scel and Sulf1 was also found in a mesonephric cell line, and siRNA-mediated knockdown of WT1 decreased Scel and Sulf1 mRNAs and proteins. By ChIP we show that Scel and Sulf1 are direct WT1 targets. Cyp26a1, encoding an enzyme involved in the degradation of retinoic acid, is shown to be up-regulated in mutant podocytes. Cyp26a1 may play a role in the development of glomerular lesions but does not seem to be regulated by WT1. These results provide novel clues in our understanding of normal glomerular function and early events involved in glomerulosclerosis.

Laser-layered microfabrication of spatially patterned functionalized tissue-engineering scaffolds

Understanding cell behavior inside complex, three-dimensional (3D) microenvironments with controlled spatiotemporal patterning of physical and biochemical factors would provide significant insights into the basic biology of organ development and tissue functions. One of the fundamental limitations in studying such behavior has been the inability to create patterned microenvironments within 3D scaffold structures. Here a simple, layer-by-layer stereolithography (SL) method that can precisely pattern ligands, extracellular-matrix (ECM) components, and growth factors, as well as controlled release particles inside a single scaffold, has been developed. The process also allows fabrication of predesigned internal architectures and porosities. Photocrosslinkable poly(ethylene glycol) dimethacrylate (PEGDMA) was used as the basic structural component of these microfabricated scaffolds. PEG acrylates, covalently modified with the cell adhesive peptide arginine-glycine-aspartic acid (RGD) or the ECM component heparan sulfate, was incorporated within the scaffolds to facilitate cell attachment and to allow spatial sequestration of heparan-binding growth factors. Fluorescently labeled polymer microparticles and basic fibroblast growth factor (FGF-2) were chosen to illustrate the capability of SL to spatiotemporally pattern scaffolds. The results demonstrate that a precise, predesigned distribution of single or multiple factors within a single 3D structure can be created, and specific internal architectures can be fabricated. Functionalization of these scaffolds with RGD is demonstrated, and heparan sulfate allows efficient cell attachment and spatial localization of growth factors. Such patterned scaffolds might provide effective systems to study cell behavior in complex microenvironments and could eventually lead to engineering of complex, hybrid tissue structures through predesigned, multilineage differentiation of a single stem-cell population.

Sulfatase 2 up-regulates glypican 3, promotes fibroblast growth factor signaling, and decreases survival in hepatocellular carcinoma

It has been shown that the heparin-degrading endosulfatase, sulfatase 1 (SULF1), functions as a liver tumor suppressor, but the role of the related sulfatase, sulfatase 2 (SULF2), in liver carcinogenesis remains to be elucidated. We investigated the effect of SULF2 on liver tumorigenesis. Expression of SULF2 was increased in 79 (57%) of 139 hepatocellular carcinomas (HCCs) and 8 (73%) of 11 HCC cell lines. Forced expression of SULF2 increased HCC cell growth and migration, whereas knockdown of SULF2 using short hairpin RNA targeting SULF2 abrogated HCC cell proliferation and migration in vitro. Because SULF1 and SULF2 desulfate heparan sulfate proteoglycans (HSPGs) and the HSPG glypican 3 (GPC3) is up-regulated in HCC, we investigated the effects of SULF2 on GPC3 expression and the association of SULF2 with GPC3. SULF2-mediated cell growth was associated with increased binding of fibroblast growth factor 2 (FGF2), phosphorylation of extracellular signal-regulated kinase and AKT, and expression of GPC3. Knockdown of GPC3 attenuated FGF2 binding in SULF2-expressing HCC cells. The effects of SULF2 on up-regulation of GPC3 and tumor growth were confirmed in nude mouse xenografts. Moreover, HCC patients with increased SULF2 expression in resected HCC tissues had a worse prognosis and a higher rate of recurrence after surgery.

CONCLUSION

In contrast to the tumor suppressor effect of SULF1, SULF2 has an oncogenic effect in HCC mediated in part through up-regulation of FGF signaling and GPC3 expression.

Sucrose octasulfate regulates fibroblast growth factor-2 binding, transport, and activity: potential for regulation of tumor growth

The antithrombotic activity of heparin has largely been credited with the success found in some cancer treatment by heparin. There are, however, many potent growth factors involved in tumor and blood vessel growth that bind to heparin with high affinity and their regulation by heparin may play a role in heparin's efficacy. We therefore chose to study the activity of a heparin analog, sucrose octasulfate (SOS), which has been similarly shown to interact with heparin-binding growth factors. Using mouse melanoma and lung carcinoma models, we demonstrate in vivo inhibition of tumor growth by SOS. SOS, however, showed little effect in coagulation assays indicating that this activity was not a primary mechanism of action for this molecule. Studies were then performed to assess the effect of SOS on basic fibroblast growth factor (FGF-2) activity, a growth factor which promotes tumor and blood vessel growth and is produced by B16 melanoma cells. SOS potently inhibited FGF-2 binding to endothelial cells and stripped pre-bound FGF-2 from cells. SOS also regulated FGF-2 stimulated proliferation. Further, SOS facilitated FGF-2 diffusion through Descemet's membrane, a heparan sulfate-rich basement membrane from the cornea, suggesting a possible role in FGF-2 clearance. Our results suggest that molecules such as SOS have the potential to remove growth factors from tumor microenvironments and the approach offers an attractive area for further study.