Two novel functions of hyaluronidase-2 (Hyal2) are formation of the glycocalyx and control of CD44-ERM interactions

The association between blood-based HYAL2 methylation and early-stage lung cancer: a case-control study

BACKGROUND

Blood-based DNA methylation biomarkers have great potential for the early detection of lung cancer (LC). Here, we investigated the association between HYAL2 methylation in peripheral blood and LC.

METHODS

Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry was performed to measure the methylation levels of 4 CpG sites in HYAL2 gene in two independent case-control studies (168 LC cases and 167 controls in Study I, 677 LC cases and 833 controls in Study II). Logistic regression adjusted for covariates was conducted for odds ratios (ORs) and 95% confidence intervals (CIs). Non-parametric tests were applied for the comparisons of stratified groups.

RESULTS

Hypomethylation of all 4 CpG sites in HYAL2 was associated with early-stage LC in the two studies (ORs range from 1.91 to 3.07 in Study I, ORs range from 1.39 to 1.86 in Study II, p < 0.05 for all). The associations were still significant for the very early-stage LC patients (stage I). Subgroup analysis indicated that the associations could be enhanced by male gender and older age. Moreover, decreased HYAL2 methylation was correlated with increased tumor size, tumor length and stage.

CONCLUSIONS

Our results suggested blood-based HYAL2 hypomethylation as a potential biomarker for LC early detection.

Genetic Deficiencies of Hyaluronan Degradation

Hyaluronan (HA) is a large polysaccharide that is broadly distributed and highly abundant in the soft connective tissues and embryos of vertebrates. The constitutive turnover of HA is very high, estimated at 5 g per day in an average (70 kg) adult human, but HA turnover must also be tightly regulated in some processes. Six genes encoding homologues to bee venom hyaluronidase (HYAL1, HYAL2, HYAL3, HYAL4, HYAL6P/HYALP1, SPAM1/PH20), as well as genes encoding two unrelated G8-domain-containing proteins demonstrated to be involved in HA degradation (CEMIP/KIAA1199, CEMIP2/TMEM2), have been identified in humans. Of these, only deficiencies in HYAL1, HYAL2, HYAL3 and CEMIP have been identified as the cause or putative cause of human genetic disorders. The phenotypes of these disorders have been vital in determining the biological roles of these enzymes but there is much that is still not understood. Deficiencies in these HA-degrading proteins have been created in mice and/or other model organisms where phenotypes could be analyzed and probed to expand our understanding of HA degradation and function. This review will describe what has been found in human and animal models of hyaluronidase deficiency and discuss how this has advanced our understanding of HA's role in health and disease.

Hyaluronan Receptors as Mediators and Modulators of the Tumor Microenvironment

The tumor microenvironment (TME) is a dynamic and complex matter shaped by heterogenous cancer and cancer-associated cells present at the tumor site. Hyaluronan (HA) is a major TME component that plays pro-tumorigenic and carcinogenic functions. These functions are mediated by different hyaladherins expressed by cancer and tumor-associated cells triggering downstream signaling pathways that determine cell fate and contribute to TME progression toward a carcinogenic state. Here, the interaction of HA is reviewed with several cell-surface hyaladherins-CD44, RHAMM, TLR2 and 4, LYVE-1, HARE, and layilin. The signaling pathways activated by these interactions and the respective response of different cell populations within the TME, and the modulation of the TME, are discussed. Potential cancer therapies via targeting these interactions are also briefly discussed.

Key Role of Hyaluronan Metabolism for the Development of Brain Metastases in Triple-Negative Breast Cancer

Breast cancer (BC) is the second-most common cause of brain metastases (BM) and BCBM patients have a reduced quality of life and a poor prognosis. Hyaluronan (HA), and in particular the hyaluronidase Hyal-1, has been already linked to the development of BCBM, and therefore presents an interesting opportunity to develop new effective therapeutic options. HA metabolism was further discovered by the CRISPR/Cas9-mediated knockout of HYAL1 and the shRNA-mediated down-regulation of HA-receptor CD44 in the brain-seeking triple-negative breast cancer (TNBC) cell line MDA-MB-231-BR. Therefore, the impact of Hyal-1 on adhesion, disruption, and invasion through the brain endothelium, both in vitro and in vivo, was studied. Our analysis points out a key role of Hyal-1 and low-molecular-weight HA (LMW-HA) in the formation of a pericellular HA-coat in BC cells, which in turn promotes tumor cell adhesion, disruption, and migration through the brain endothelium in vitro as well as the extent of BM in vivo. CD44 knockdown in MDA-MB-231-BR significantly reduced the pericellular HA-coat on these cells, and, consequently, tumor cell adhesion and invasion through the brain endothelium. Thus, the interaction between Hyal-1-generated LMW-HA fragments and the HA-receptor CD44 might represent a potential target for future therapeutic options in BC patients with a high risk of cerebral metastases formation.

Methods for isolating and analyzing physiological hyaluronan: a review

The carbohydrate hyaluronan (or hyaluronic acid, HA) is found in all human tissues and biofluids where it has wide-ranging functions in health and disease that are dictated by both its abundance and size. Consequently, hyaluronan evaluation in physiological samples has significant translational potential. Although the analytical tools and techniques for probing other biomolecules such as proteins and nucleic acids have become standard approaches in biochemistry, those available for investigating hyaluronan are less well established. In this review, we survey methods related to the assessment of native hyaluronan in biological specimens, including protocols for separating it from biological matrices and technologies for determining its concentration and molecular weight.

Matters of size: Roles of hyaluronan in CNS aging and disease

Involvement of extracellular matrix (ECM) components in aging and age-related neurodegeneration is not well understood. The role of hyaluronan (HA), a major extracellular matrix glycosaminoglycan, in malignancy and inflammation is gaining new understanding. In particular, the differential biological effects of high molecular weight (HMW-HA) and low molecular weight hyaluronan (LMW-HA), and the mechanism behind such differences are being uncovered. Tightly regulated in the brain, HA can have diverse effects on cellular development, growth and degeneration. In this review, we summarize the homeostasis and signaling of HA in healthy tissue, discuss its distribution and ontogeny in the central nervous system (CNS), summarize evidence for its involvement in age-related neurodegeneration and Alzheimer Disease (AD), and assess the potential of HA as a therapeutic target in the CNS.

Neutrophil-derived heparin binding protein triggers vascular leakage and synergizes with myeloperoxidase at the early stage of severe burns (With video)

Background

Burn shock caused by vascular leakage is one of the main causes of high mortality in severe burn injury. However, the pathophysiological mechanism of vascular leakage is still unclear. The purpose of this study was to explore the molecular mechanism of vascular leakage in the early stage of severe burn and provide a new target for the treatment of severe burns.

Methods

Neutrophils were isolated from human peripheral blood by magnetic beads sorting. ELISA was used to detect neutrophil-derived granule proteins and glycocalyx injury products in plasma. The vascular leakage and neutrophil movement were assessed by in vivo laser confocal imaging in mice, and high-quality video were provided.. Adhesion-related molecules were investigated by qRT-PCR. The damage to glycocalyx of mice vascular endothelial cells was observed by transmission electron microscope and scanning electron microscope. Proteomic analysis, flow cytometry and immunofluorescence were used to further study the relationship between human peripheral blood neutrophil-derived hypochlorite (HOCl) and CD44 of human vascular endothelial cells.

Results

In this study, we found that rapidly increasing activated neutrophils secrete heparin binding protein (HBP) and myeloperoxidase (MPO) after severe burn injury. Increased HBP triggers vascular leakage with synergy of MPO, results in systemic edema and burn shock. Furthermore, we found that the MPO catalytic product HOCl but not MPO triggers CD44 extracellular domain shedding from vascular endothelial cells to damage the glycocalyx. Damage to the glycocalyx results in firm adhesion of neutrophils and increases vascular leakage. However, MPO inhibitors partially protect the glycocalyx of vascular endothelial cells. The combination of HBP and MPO inhibitors markedly reduces vascular leakage and systemic edema in the early stage of severe burns.

Conclusions

Taken together, these data reveal that neutrophil-derived HBP and MPO play an important synergies role in triggering vascular leakage at the early stage of severe burns. Targeted intervention in these two biomolecules may introduce new strategies for helping to reduce large amount of fluid loss and subsequent burn shock.

Myofibroblasts: Function, Formation, and Scope of Molecular Therapies for Skin Fibrosis

Myofibroblasts are contractile, α-smooth muscle actin-positive cells with multiple roles in pathophysiological processes. Myofibroblasts mediate wound contractions, but their persistent presence in tissues is central to driving fibrosis, making them attractive cell targets for the development of therapeutic treatments. However, due to shared cellular markers with several other phenotypes, the specific targeting of myofibroblasts has long presented a scientific and clinical challenge. In recent years, myofibroblasts have drawn much attention among scientific research communities from multiple disciplines and specialisations. As further research uncovers the characterisations of myofibroblast formation, function, and regulation, the realisation of novel interventional routes for myofibroblasts within pathologies has emerged. The research community is approaching the means to finally target these cells, to prevent fibrosis, accelerate scarless wound healing, and attenuate associated disease-processes in clinical settings. This comprehensive review article describes the myofibroblast cell phenotype, their origins, and their diverse physiological and pathological functionality. Special attention has been given to mechanisms and molecular pathways governing myofibroblast differentiation, and updates in molecular interventions.

Hyal2 Expression in Tumor-Associated Myeloid Cells Mediates Cancer-Related Inflammation in Bladder Cancer

The increased presence of myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) in tumor tissue has been extensively reported. However, their role in the regulation of hyaluronan (HA) metabolism in the tumor microenvironment has not been established. Here we describe a novel function of tumor-associated myeloid cells related to the enhanced breakdown of extracellular HA in human bladder cancer tissue, leading to the accumulation of small HA fragments with molecular weight (MW) <20 kDa. Increased fragmentation of extracellular HA and accumulation of low molecular weight HA (LMW-HA) in tumor tissue was associated with elevated production of multiple inflammatory cytokines, chemokines, and angiogenic factors. The fragmentation of HA by myeloid cells was mediated by the membrane-bound enzyme hyaluronidase 2 (Hyal2). Increased numbers of Hyal2⁺CD11b⁺ myeloid cells were detected in the tumor tissue as well as in the peripheral blood of patients with bladder cancer. Coexpression of CD33 suggested that these cells belong to monocytic myeloid-derived suppressor cells. The HA-degrading function of Hyal2-expressing MDSCs could be enhanced by exposure to tumor-conditioned medium, and IL1β was identified as one of the factors involved in the stimulation of Hyal2 activity. CD44-mediated signaling played an important role in the regulation of HA-degrading activity of Hyal2-expressing myeloid cells, as the engagement of CD44 receptor with specific mAb triggered translocation of Hyal2 enzyme to the cellular surface and stimulated secretion of IL1β. Taken together, this work identifies Hyal2-expressing tumor-associated myeloid cells as key players in the accumulation of LMW-HA in the tumor microenvironment and cancer-related inflammation and angiogenesis. SIGNIFICANCE: This study identifies Hyal2-expressing tumor-associated myeloid cells of monocyte-macrophage lineage as contributors to hyaluronan degradation in bladder cancer tissue, leading to accumulation of inflammatory and proangiogenic low molecular weight hyaluronan fragments.

Hyaluronidase-2 Regulates RhoA Signaling, Myofibroblast Contractility, and Other Key Profibrotic Myofibroblast Functions

Hyaluronidase (HYAL)-2 is a weak, acid-active, hyaluronan-degrading enzyme broadly expressed in somatic tissues. Aberrant HYAL2 expression is implicated in diverse pathology. However, a significant proportion of HYAL2 is enzymatically inactive; thus the mechanisms through which HYAL2 dysregulation influences pathobiology are unclear. Recently, nonenzymatic HYAL2 functions have been described, and nuclear HYAL2 has been shown to influence mRNA splicing to prevent myofibroblast differentiation. Myofibroblasts drive fibrosis, thereby promoting progressive tissue damage and leading to multimorbidity. This study identifies a novel HYAL2 cytoplasmic function in myofibroblasts that is unrelated to its enzymatic activity. In fibroblasts and myofibroblasts, HYAL2 interacts with the GTPase-signaling small molecule ras homolog family member A (RhoA). Transforming growth factor beta 1–driven fibroblast-to-myofibroblast differentiation promotes HYAL2 cytoplasmic relocalization to bind to the actin cytoskeleton. Cytoskeletal-bound HYAL2 functions as a key regulator of downstream RhoA signaling and influences profibrotic myofibroblast functions, including myosin light-chain kinase–mediated myofibroblast contractility, myofibroblast migration, myofibroblast collagen/fibronectin deposition, as well as connective tissue growth factor and matrix metalloproteinase-2 expression. These data demonstrate that, in certain biological contexts, the nonenzymatic effects of HYAL2 are crucial in orchestrating RhoA signaling and downstream pathways that are important for full profibrotic myofibroblast functionality. In conjunction with previous data demonstrating the influence of HYAL2 on RNA splicing, these findings begin to explain the broad biological effects of HYAL2.

Role of Moesin Phosphorylation in Retinal Pericyte Migration and Detachment Induced by Advanced Glycation Endproducts

Proliferative diabetic retinopathy (PDR) involves persistent, uncontrolled formation of premature blood vessels with reduced number of pericytes. Our previous work showed that advanced glycation endproducts (AGEs) induced angiogenesis in human umbilical vein endothelial cells, mouse retina, and aortic ring, which was associated with moesin phosphorylation. Here we investigated whether moesin phosphorylation may contribute to pericyte detachment and the development of PDR. Primary retinal microvascular pericytes (RMPs) were isolated, purified from weanling rats, and identified by cellular markers α-SMA, PDGFR-β, NG2, and desmin using immunofluorescence microscopy. Effects of AGE-BSA on proliferation and migration of RMPs were examined using CCK-8, wound healing, and transwell assays. Effects on moesin phosphorylation were examined using western blotting. The RMP response to AGE-BSA was also examined when cells expressed the non-phosphorylatable Thr558Ala mutant or phospho-mimicking Thr558Asp mutant of moesin or were treated with ROCK inhibitor Y27632. Colocalization and interaction between CD44, phospho-moesin, and F-actin were observed. Experiments with cultured primary RMPs showed that AGE-BSA inhibited the proliferation, enhanced the migration, and increased moesin phosphorylation in a dose- and time-dependent manner. AGE-BSA also triggered the rearrangement of F-actin and promoted the interaction of CD44 with phospho-moesin in RMPs. These effects were abrogated in cells expressing the non-phosphorylatable moesin mutant and the application of ROCK inhibitor Y27632 attenuated AGE-induced alteration in cultured RMPs by abolishing the phosphorylation of moesin. However, those AGE-induced pathological process occurred in RMPs expressed the phospho-mimicking moesin without AGE-BSA treatment. It is concluded that AGEs could activate ROCK to mediate moesin phosphorylation at Thr558, and resulting phospho-moesin interacts with CD44 to form CD44 cluster, which might stimulate the migration of RMPs and subsequent RMP detachment in microvessel. This pathway may provide new drug targets against immature neovessel formation in PDR.

The U3 and Env Proteins of Jaagsiekte Sheep Retrovirus and Enzootic Nasal Tumor Virus Both Contribute to Tissue Tropism

Jaagsiekte sheep retrovirus (JSRV) and enzootic nasal tumor virus (ENTV) are small-ruminant betaretroviruses that share high nucleotide and amino acid identity, utilize the same cellular receptor, hyaluronoglucosaminidase 2 (Hyal2) for entry, and transform tissues with their envelope (Env) glycoprotein; yet, they target discrete regions of the respiratory tract—the lung and nose, respectively. This distinct tissue selectivity makes them ideal tools with which to study the pathogenesis of betaretroviruses. To uncover the genetic determinants of tropism, we constructed JSRV–ENTV chimeric viruses and produced lentivectors pseudotyped with the Env proteins from JSRV (Jenv) and ENTV (Eenv). Through the transduction and infection of lung and nasal turbinate tissue slices, we observed that Hyal2 expression levels strongly influence ENTV entry, but that the long terminal repeat (LTR) promoters of these viruses are likely responsible for tissue-specificity. Furthermore, we show evidence of ENTV Env expression in chondrocytes within ENTV-infected nasal turbinate tissue, where Hyal2 is highly expressed. Our work suggests that the unique tissue tropism of JSRV and ENTV stems from the combined effort of the envelope glycoprotein-receptor interactions and the LTR and provides new insight into the pathogenesis of ENTV.

High levels of serum hyaluronan is an early predictor of dengue warning signs and perturbs vascular integrity

BACKGROUND

A main pathological feature of severe dengue virus infection is endothelial hyper-permeability. The dengue virus nonstructural protein 1 (NS1) has been implicated in the vascular leakage that characterizes severe dengue virus infection, however, the molecular mechanisms involved are not known.

METHODS

A cohort of 250 dengue patients has been followed from the onset of symptoms to the recovery phase. Serum hyaluronan levels and several other clinical parameters were recorded. The effect of NS1 treatment of cultured fibroblasts and endothelial cells on the expressions of hyaluronan synthetic and catabolic enzymes and the hyaluronan receptor CD44, were determined, as have the effects on the formation of hyaluronan-rich matrices and endothelial permeability.

FINDINGS

Elevated serum hyaluronan levels (≥70 ng/ml) during early infection was found to be an independent predictor for occurrence of warning signs, and thus severe dengue fever. High circulating levels of the viral protein NS1, indicative of disease severity, correlated with high concentrations of serum hyaluronan. NS1 exposure decreased the expression of CD44 in differentiating endothelial cells impairing the integrity of vessel-like structures, and promoted the synthesis of hyaluronan in dermal fibroblasts and endothelial cells in synergy with dengue-induced pro-inflammatory mediators. Deposited hyaluronan-rich matrices around cells cultured in vitro recruited CD44-expressing macrophage-like cells, suggesting a mechanism for enhancement of inflammation. In cultured endothelial cells, perturbed hyaluronan-CD44 interactions enhanced endothelial permeability through modulation of VE-cadherin and cytoskeleton re-organization, and exacerbated the NS1-induced disruption of endothelial integrity.

INTERPRETATION

Pharmacological targeting of hyaluronan biosynthesis and/or its CD44-mediated signaling may limit the life-threatening vascular leakiness during moderate-to-severe dengue virus infection. FUND: This work was supported in part by grants from the Swedish Cancer Society (2018/337; 2016/445), the Swedish Research Council (2015-02757), the Ludwig Institute for Cancer Research, Uppsala University, the Ministry of Science and Technology, Taiwan (106-2314-B-037-088- and 106-2915-I-037-501-), Kaohsiung Medical University Hospital (KMUH103-3 T05) and Academy of Finland. The funders played no role in the design, interpretation or writing of the manuscript.

Platelet hyaluronidase-2 regulates the early stages of inflammatory disease in colitis

Platelets are specialized cells essential for hemostasis that also function as crucial effectors capable of mediating inflammatory and immune responses. These sentinels continually survey their environment and discriminate between homeostatic and danger signals such as modified components of the extracellular matrix. The glycosaminoglycan hyaluronan (HA) is a major extracellular matrix component that coats the vascular lumen and, under normal conditions, restricts access of inflammatory cells. In response to tissue damage, the endothelial HA matrix enhances leukocyte recruitment and regulates the early stages of the inflammatory response. We have shown that platelets can degrade HA from the surface of activated endothelial cells via the enzyme hyaluronidase-2 (HYAL2) and that HYAL2 is deficient in platelets isolated from patients with inflammatory bowel disease (IBD). Platelets are known to be involved in the pathogenesis of several chronic disease states, including IBD, but they have been largely overlooked in the context of intestinal inflammation. We therefore wanted to define the mechanism by which platelet HYAL2 regulates the inflammatory response during colitis. In this study, we provide evidence that HA catabolism is disrupted in human intestinal microvascular endothelial cells isolated from patients with IBD. Furthermore, mice deficient in HYAL2 are more susceptible to an acute model of colitis, and this increased susceptibility is abrogated by transfusion of HYAL2-competent platelets. Finally, we show that platelets, via HYAL2-dependent degradation of endothelial HA, regulate the early stages of inflammation in colitis by limiting leukocyte extravasation.

Targeting Hyaluronan Interactions for Glioblastoma Stem Cell Therapy

Even with rigorous treatments, glioblastoma multiforme (GBM) has an abysmal median survival rate, greatly due to the drug-resistant glioblastoma stem cell (GSC) population. GSCs are known to remodel their microenvironment, but the precise role of extracellular matrix components hyaluronic acid (HA) and hyaluronidases (HAases) on the GSC population is still largely unknown. Our objective was to determine how HAase can sensitize GSCs to chemotherapy drugs by disrupting the HA-CD44 signaling. GBM cell line U87-MG and patient-derived D456 cells were grown in GSC-enriching media and treated with HA or HAase. Expressions of GSC markers, HA-related genes, and drug resistance genes were measured via flow cytometry, confocal microscopy, and qRT-PCR. Proliferation after combined HAase and temozolomide (TMZ) treatment was measured via WST-8. HA supplementation promoted the expression of GSC markers and CD44 in GBM cells cultured in serum-free media. Conversely, HAase addition inhibited GSC gene expression while promoting CD44 expression. Finally, HAase sensitized GBM cells to TMZ. We propose a combined treatment of HAase and chemotherapy drugs by disrupting the stemness-promoting HA to target GSCs. This combination therapy shows promise even when temozolomide treatment alone causes resistance.

Hyaluronidase2 (Hyal2) modulates low shear stress-induced glycocalyx impairment via the LKB1/AMPK/NADPH oxidase-dependent pathway

The endothelium glycocalyx layer (ECL), presents on the apical surface of endothelial cells, creates a barrier between circulating blood and the vessel wall. Low shear stress (LSS) may accelerate the degradation of the glycocalyx via hyaluronidase2 (Hyal2) and then alter the cell polarity. Yet the liver kinase B1 (LKB1) signaling pathway plays an important role in regulating cell polarity. However, the relationship between LKB1 and glycocalyx during LSS is not clear. In the current study, we demonstrate that LSS attenuates LKB1 and AMP-activated protein kinase activation as well as activated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (p47^phox ) and Hyal2 in the human umbilical vein endothelial cell (HUVEC). Pretreatment with 5-Aminoimidazole-4-carboxamide1-β-D-ribofuranoside (AICAR), or diphenyleneiodonium (DPI chloride) and transfection with LKB1 overexpression vector and p47^phox small interfering RNA downregulated LSS-induced Hyal2 activation. By coimmunoprecipitation, we discovered the existence of p47^phox /Hyal2 complex. LSS induced the dissociation of p47^phox /Hyal2 complex, which was inhibited by LKB1 overexpression and AICAR. Furthermore, knockdown of Hyal2 performed a positive feedback on LKB1 activity. In addition, we also show that LSS enhanced LKB1 translocation from the cytosol to the nucleus. Taken together, these data indicate that Hyal2 regulates LSS-induced injury of the glycocalyx via LKB1/AMPK/NADPH oxidase signaling cascades.

Synaptic Remodeling Depends on Signaling between Serotonin Receptors and the Extracellular Matrix

Rewiring of synaptic circuitry pertinent to memory formation has been associated with morphological changes in dendritic spines and with extracellular matrix (ECM) remodeling. Here, we mechanistically link these processes by uncovering a signaling pathway involving the serotonin 5-HT7 receptor (5-HT7R), matrix metalloproteinase 9 (MMP-9), the hyaluronan receptor CD44, and the small GTPase Cdc42. We highlight a physical interaction between 5-HT7R and CD44 (identified as an MMP-9 substrate in neurons) and find that 5-HT7R stimulation increases local MMP-9 activity, triggering dendritic spine remodeling, synaptic pruning, and impairment of long-term potentiation (LTP). The underlying molecular machinery involves 5-HT7R-mediated activation of MMP-9, which leads to CD44 cleavage followed by Cdc42 activation. One important physiological consequence of this interaction includes an increase in neuronal outgrowth and elongation of dendritic spines, which might have a positive effect on complex neuronal processes (e.g., reversal learning and neuronal regeneration).

Regulation of hyaluronan biosynthesis and clinical impact of excessive hyaluronan production

The tightly regulated biosynthesis and catabolism of the glycosaminoglycan hyaluronan, as well as its role in organizing tissues and cell signaling, is crucial for the homeostasis of tissues. Overexpression of hyaluronan plays pivotal roles in inflammation and cancer, and markedly high serum and tissue levels of hyaluronan are noted under such pathological conditions. This review focuses on the complexity of the regulation at transcriptional and posttranslational level of hyaluronan synthetic enzymes, and the outcome of their aberrant expression and accumulation of hyaluronan in clinical conditions, such as systemic B-cell cancers, aggressive breast carcinomas, metabolic diseases and virus infection.

Nuclear hyaluronidase 2 drives alternative splicing of CD44 pre-mRNA to determine profibrotic or antifibrotic cell phenotype

The cell surface protein CD44 is involved in diverse physiological processes, and its aberrant function is linked to various pathologies such as cancer, immune dysregulation, and fibrosis. The diversity of CD44 biological activity is partly conferred by the generation of distinct CD44 isoforms through alternative splicing. We identified an unexpected function for the ubiquitous hyaluronan-degrading enzyme, hyaluronidase 2 (HYAL2), as a regulator of CD44 splicing. Standard CD44 is associated with fibrotic disease, and its production is promoted through serine-arginine-rich (SR) protein-mediated exon exclusion. HYAL2 nuclear translocation was stimulated by bone morphogenetic protein 7, which inhibits the myofibroblast phenotype. Nuclear HYAL2 displaced SR proteins from the spliceosome, thus enabling HYAL2, spliceosome components (U1 and U2 small nuclear ribonucleoproteins), and CD44 pre-mRNA to form a complex. This prevented double-exon splicing and facilitated the inclusion of CD44 exons 11 and 12, which promoted the accumulation of the antifibrotic CD44 isoform CD44v7/8 at the cell surface. These data demonstrate previously undescribed mechanisms regulating CD44 alternative splicing events that are relevant to the regulation of cellular phenotypes in progressive fibrosis.

Hyaluronan and Hyaluronan Fragments

The glycosaminoglycan hyaluronan (HA) is a key component of the microenvironment surrounding cells. In healthy tissues, HA molecules have extremely high molecular mass and consequently large hydrodynamic volumes. Tethered to the cell surface by clustered receptor proteins, HA molecules crowd each other, as well as other macromolecular species. This leads to severe nonideality in physical properties of the biomatrix, because steric exclusion leads to an increase in effective concentration of the macromolecules. The excluded volume depends on both polymer concentration and hydrodynamic volume/molecular mass. The biomechanical properties of the extracellular matrix, tissue hydration, receptor clustering, and receptor-ligand interactions are strongly affected by the presence of HA and by its molecular mass. In inflammation, reactive oxygen and nitrogen species fragment the HA chains. Depending on the rate of chain degradation relative to the rates of new synthesis and removal of damaged chains, short fragments of the HA molecules can be present at significant levels. Not only are the physical properties of the extracellular matrix affected, but the HA fragments decluster their primary receptors and act as endogenous danger signals. Bioanalytical methods to isolate and quantify HA fragments have been developed to determine profiles of HA content and size in healthy and diseased biological fluids and tissues. These methods have potential use in medical diagnostic tests. Therapeutic agents that modulate signaling by HA fragments show promise in wound healing and tissue repair without fibrosis.

A Trickster in Disguise: Hyaluronan's Ambivalent Roles in the Matrix

Hyaluronan (HA) is a simple but diverse glycosaminoglycan. It plays a major role in aging, cellular senescence, cancer, and tissue homeostasis. In which way HA affects the surrounding tissues greatly depends on the molecular weight of HA. Whereas high molecular weight HA is associated with homeostasis and protective effects, HA fragments tend to be linked to the pathologic state. Furthermore, the interaction of HA with its binding partners, the hyaladherins, such as CD44, is essential for sustaining tissue integrity and is likewise related to cancer. The naked mole rat, a rodent species, possesses a special form of very high molecular weight (vHMW) HA, which is associated with the extraordinary cancer resistance and longevity of those animals. This review addresses HA and its diverse facets: from HA synthesis to degradation, from oligomeric HA to vHMW-HA and from its beneficial properties to the involvement in pathologies. We further discuss the functions of HA in the naked mole rat and compare them to human conditions. Though intensively researched, this simple polymer bears some secrets that may hold the key for a better understanding of cellular processes and the development of diseases, such as cancer.

Hyaluronan activates Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed

Malignant cancer cells frequently secrete significant amounts of transforming growth factor beta (TGF-β), hyaluronan (HA) and hyaluronidases to facilitate metastasizing to target organs. In a non-canonical signaling, TGF-β binds membrane hyaluronidase Hyal-2 for recruiting tumor suppressors WWOX and Smad4, and the resulting Hyal-2/WWOX/Smad4 complex is accumulated in the nucleus to enhance SMAD-promoter dependent transcriptional activity. Yeast two-hybrid analysis showed that WWOX acts as a bridge to bind both Hyal-2 and Smad4. When WWOX-expressing cells were stimulated with high molecular weight HA, an increased formation of endogenous Hyal-2/WWOX/Smad4 complex occurred rapidly, followed by relocating to the nuclei in 20-40 min. In WWOX-deficient cells, HA failed to induce Smad2/3/4 relocation to the nucleus. To prove the signaling event, we designed a real time tri-molecular FRET analysis and revealed that HA induces the signaling pathway from ectopic Smad4 to WWOX and finally to p53, as well as from Smad4 to Hyal-2 and then to WWOX. An increased binding of the Smad4/Hyal-2/WWOX complex occurs with time in the nucleus that leads to bubbling cell death. In contrast, HA increases the binding of Smad4/WWOX/p53, which causes membrane blebbing but without cell death. In traumatic brain injury-induced neuronal death, the Hyal-2/WWOX complex was accumulated in the apoptotic nuclei of neurons in the rat brains in 24 hr post injury, as determined by immunoelectron microscopy. Together, HA activates the Hyal-2/WWOX/Smad4 signaling and causes bubbling cell death when the signaling complex is overexpressed.

HYAL2 methylation in peripheral blood as a potential marker for the detection of pancreatic cancer: a case control study

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy which is mostly diagnosed in advanced and inoperable stages though surgery remains the only curable therapeutic approach. Early detection markers are urgently needed to improve diagnosis. Altered hyaluronoglucosaminidase 2 gene (HYAL2) DNA methylation in peripheral blood is known to be associated with malignancy at early stage but has not been evaluated in PDAC patients. This study evaluates the association between blood-based HYAL2 methylation and PDAC by a case-control study with 191 controls and 82 PDAC patients. Decreased methylation of all four investigated HYAL2 methylation sites showed highly significant association with PDAC (odds ratio (ORs) per −10% methylation ranging from 2.03 to 12.74, depending on the specific CpG site, p < 0.0001 for all). HYAL2 methylation sites were also distinguishable between stage I&II PDAC (61 subjects) and controls (ORs per-10% methylation from 3.17 - 23.04, p < 0.0001 for all). Thus, HYAL2 methylation level enabled a very good discrimination of PDAC cases from healthy controls (area under curve (AUC) = 0.92, 95% Confidence interval (C.I.): 0.88 - 0.96), and was also powerful for the detection of PDAC at stage I&II (AUC = 0.93, 95% C.I.: 0.89 - 0.98). Moreover, the blood-based HYAL2 methylation pattern was similar among PDAC patients with differential clinical characteristics, and showed no correlation with the overall survival of PDAC patients. Our study reveals a strong association between decreased HYAL2 methylation in peripheral blood and PDAC, and provides a promising blood-based marker for the detection of PDAC.

A mammalian homolog of the zebrafish transmembrane protein 2 (TMEM2) is the long-sought-after cell-surface hyaluronidase

Hyaluronan (HA) is an extremely large polysaccharide (glycosaminoglycan) involved in many cellular functions. HA catabolism is thought to involve the initial cleavage of extracellular high-molecular-weight (HMW) HA into intermediate-size HA by an extracellular or cell-surface hyaluronidase, internalization of intermediate-size HA, and complete degradation into monosaccharides in lysosomes. Despite considerable research, the identity of the hyaluronidase responsible for the initial HA cleavage in the extracellular space remains elusive. HYAL1 and HYAL2 have properties more consistent with lysosomal hyaluronidases, whereas CEMIP/KIAA1199, a recently identified HA-binding molecule that has HA-degrading activity, requires the participation of the clathrin-coated pit pathway of live cells for HA degradation. Here we show that transmembrane protein 2 (TMEM2), a mammalian homolog of a protein playing a role in zebrafish endocardial cushion development, is a cell-surface hyaluronidase. Live immunostaining and surface biotinylation assays confirmed that mouse TMEM2 is expressed on the cell surface in a type II transmembrane topology. TMEM2 degraded HMW-HA into ∼5-kDa fragments but did not cleave chondroitin sulfate or dermatan sulfate, indicating its specificity to HA. The hyaluronidase activity of TMEM2 was Ca²⁺-dependent; the enzyme's pH optimum is around 6-7, and unlike CEMIP/KIAA1199, TMEM2 does not require the participation of live cells for its hyaluronidase activity. Moreover, TMEM2-expressing cells could eliminate HA immobilized on a glass surface in a contact-dependent manner. Together, these data suggest that TMEM2 is the long-sought-after hyaluronidase that cleaves extracellular HMW-HA into intermediate-size fragments before internalization and degradation in the lysosome.

Decreased expression of hyaluronan synthase 1 and 2 associates with poor prognosis in cutaneous melanoma

Background

Hyaluronan is a large extracellular matrix molecule involved in several biological processes such as proliferation, migration and invasion. In many cancers, hyaluronan synthesis is altered, which implicates disease progression and metastatic potential. We have previously shown that synthesis of hyaluronan and expression of its synthases 1–2 (HAS1-2) decrease in cutaneous melanoma, compared to benign melanocytic lesions.

Methods

In the present study, we compared immunohistological staining results of HAS1 and HAS2 with clinical and histopathological parameters to investigate whether HAS1 or HAS2 has prognostic value in cutaneous melanoma. The specimens consisted of 129 tissue samples including superficial (Breslow ≤ 1 mm) and deep (Breslow > 4 mm) melanomas and lymph node metastases. The differences in immunostainings were analysed with non-parametric Mann–Whitney U test. Associations between immunohistological staining results and clinical parameters were determined with the χ² test. Survival between patient groups was compared by the Kaplan-Meier method using log rank test and Cox’s regression model was used for multivariate analyses.

Results

The expression of HAS1 and HAS2 was decreased in deep melanomas and metastases compared to superficial melanomas. Decreased immunostaining of HAS2 in melanoma cells was significantly associated with several known unfavourable histopathologic prognostic markers like increased mitotic count, absence of tumor infiltrating lymphocytes and the nodular subtype. Furthermore, reduced HAS1 and HAS2 immunostaining in the melanoma cells was associated with increased recurrence of melanoma (p = 0.041 and p = 0.006, respectively) and shortened disease- specific survival (p = 0.013 and p = 0.001, respectively).

Conclusions

This study indicates that reduced expression of HAS1 and HAS2 is associated with melanoma progression and suggests that HAS1 and HAS2 have a prognostic significance in cutaneous melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2344-8) contains supplementary material, which is available to authorized users.

Hyaluronidase 2 (HYAL2) is expressed in endothelial cells, as well as some specialized epithelial cells, and is required for normal hyaluronan catabolism

Hyaluronidase 2 (HYAL2) is a membrane-anchored protein that is proposed to initiate the degradation of hyaluronan (HA) in the extracellular matrix. The distribution of HYAL2 in tissues, and of HA in tissues lacking HYAL2, is largely unexplored despite the importance of HA metabolism in several disease processes. Herein, we use immunoblot and histochemical analyses to detect HYAL2 and HA in mouse tissues, as well as agarose gel electrophoresis to examine the size of HA. HYAL2 was detected in all tissues that were examined, including the brain. It was localized to the surface and cytoplasm of endothelial cells, as well as specialized epithelial cells in several tissues, including the skin. Accumulated HA, often of higher molecular mass than that in control tissues, was detected in tissues from Hyal2 (-/-) mice. The accumulating HA was located near to where HYAL2 is normally found, although in some tissues, it was distant from the site of HYAL2 localization. Overall, HYAL2 was highest in tissues that remove HA from the circulation (liver, lymph node and spleen), but the levels of HA accumulation in Hyal2 (-/-) mice were highest in tissues that catabolize locally synthesized HA. Our results support HYAL2's role as an extracellular enzyme that initiates HA breakdown in somatic tissues. However, our findings also suggest that HYAL2 contributes to HA degradation through other routes, perhaps as a soluble or secreted form.

Methylation status at HYAL2 predicts overall and progression-free survival of colon cancer patients under 5-FU chemotherapy

DNA methylation variations in gene promoter regions are well documented tumor-specific alterations in human malignancies including colon cancer, which may influence tumor behavior and clinical outcome. As a subset of colon cancer patients does not benefit from adjuvant chemotherapy, predictive biomarkers are desirable. Here, we describe that DNA methylation levels at CpG loci of hyaluronoglucosaminidase 2 (HYLA2) could be used to identify stage II and III colon cancer patients who are most likely to benefit from 5-flourouracil (5-FU) chemotherapy with respect to overall survival and progression-free survival.

Biology of hyaluronan: Insights from genetic disorders of hyaluronan metabolism

Hyaluronan is a rapidly turned over component of the vertebrate extracellular matrix. Its levels are determined, in part, by the hyaluronan synthases, HAS1, HAS2, and HAS3, and three hyaluronidases, HYAL1, HYAL2 and HYAL3. Hyaluronan binding proteins also regulate hyaluronan levels although their involvement is less well understood. To date, two genetic disorders of hyaluronan metabolism have been reported in humans: HYAL1 deficiency (Mucopolysaccharidosis IX) in four individuals with joint pathology as the predominant phenotypic finding and HAS2 deficiency in a single person having cardiac pathology. However, inherited disorders and induced mutations affecting hyaluronan metabolism have been characterized in other species. Overproduction of hyaluronan by HAS2 results in skin folding and thickening in shar-pei dogs and the naked mole rat, whereas a complete deficiency of HAS2 causes embryonic lethality in mice due to cardiac defects. Deficiencies of murine HAS1 and HAS3 result in a predisposition to seizures. Like humans, mice with HYAL1 deficiency exhibit joint pathology. Mice lacking HYAL2 have variably penetrant developmental defects, including skeletal and cardiac anomalies. Thus, based on mutant animal models, a partial deficiency of HAS2 or HYAL2 might be compatible with survival in humans, while complete deficiencies of HAS1, HAS3, and HYAL3 may yet be recognized.

Lipid Raft-Mediated Regulation of Hyaluronan-CD44 Interactions in Inflammation and Cancer

Hyaluronan is a major component of the extracellular matrix and plays pivotal roles in inflammation and cancer. Hyaluronan oligomers are frequently found in these pathological conditions, in which they exert their effects via association with the transmembrane receptor CD44. Lipid rafts are cholesterol- and glycosphingolipid-enriched membrane microdomains that may regulate membrane receptors while serving as platforms for transmembrane signaling at the cell surface. This article focuses on the recent discovery that lipid rafts regulate the interaction between CD44 and hyaluronan, which depends largely on hyaluronan's size. Lipid rafts regulate CD44's ability to bind hyaluronan in T cells, control the rolling adhesion of lymphocytes on vascular endothelial cells, and regulate hyaluronan- and CD44-mediated cancer cell migration. The implications of these findings for preventing inflammatory disorders and cancer are also discussed.

S100P and HYAL2 as prognostic markers for patients with triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a group of very aggressive breast tumours, characterised by lack of expression of oestrogen receptor (ER), progesterone receptor (PR) and erb-b2 receptor tyrosine kinase 2 (ERBB2/HER2). Nevertheless, TNBCs show different clinical characteristics and are very diverse regarding prognostic outcome. So far, only a few prognostic markers for TNBC have been reported that could be helpful for therapeutic stratification. Here we have analysed the expression of S100P and HYAL2 using immunohistochemistry (IHC) in a TNBC cohort of 98 patients with a follow-up for recurrence and death. TNBC patients with high expression of both proteins showed significantly shorter progression-free survival (PFS) (mean PFS=35.9months, P=0.001) compared to TNBC patients with high expression levels of only one of the proteins (mean PFS=69.4months) and to TNBC patients with low expression of both proteins (mean PFS=83.3months). Moreover, multivariate Cox-regression model showed the combined expression of S100P and HYAL2 as independent prognostic factor for PFS (P=0.001). The expression of S100P and HYAL2 indicated similar prognostic effect to the overall survival (OS) of TNBC patients. In addition, high expression levels of both S100P and HYAL2 showed significant association with different clinicopathological characteristics, such as more recurrence events (P=0.004), and higher occurrence of metastasis (P=0.002). Our study proposes S100P and HYAL2 as potential prognostic markers for TNBC.

Emerging roles for hyaluronidase in cancer metastasis and therapy

Hyaluronidases are a family of five human enzymes that have been differentially implicated in the progression of many solid tumor types, both clinically and in functional studies. Advances in the past 5 years have clarified many apparent contradictions: (1) by demonstrating that specific hyaluronidases have alternative substrates to hyaluronan (HA) or do not exhibit any enzymatic activity, (2) that high-molecular weight HA polymers elicit signaling effects that are opposite those of the hyaluronidase-digested HA oligomers, and (3) that it is actually the combined overexpression of HA synthesizing enzymes with hyaluronidases that confers tumorigenic potential. This review examines the literature supporting these conclusions and discusses novel mechanisms by which hyaluronidases impact invasive tumor cell processes. In addition, a detailed structural and functional comparison of the hyaluronidases is presented with insights into substrate selectivity and potential for therapeutic targeting. Finally, technological advances in targeting hyaluronidase for tumor imaging and cancer therapy are summarized.

CD44 knock-down in bovine and human chondrocytes results in release of bound HYAL2

CD44 shedding occurs in osteoarthritic chondrocytes. Previous work of others has suggested that the hyaluronidase isoform HYAL2 has the capacity to bind to CD44, a binding that may itself induce CD44 cleavage. Experiments were developed to elucidate whether chondrocyte HYAL2: (1) was exposed on the extracellular plasma membrane of chondrocytes, (2) bound to CD44, (3) underwent shedding together with CD44 and lastly, (4) exhibited hyaluronidase activity within a near-neutral pH range. Enhancing CD44 shedding by IL-1β resulted in a proportional increase in HYAL2 released from human and bovine chondrocytes into the medium. CD44 knockdown by siRNA also resulted in increased accumulation of HYAL2 in the media of chondrocytes. By hyaluronan zymography only activity at pH3.7 was observed and this activity was reduced by pre-treatment of chondrocytes with trypsin. CD44 and HYAL2 were found to co-immunoprecipitate, and to co-localize within intracellular vesicles and at the plasma membrane. Degradation of hyaluronan was visualized by agarose gel electrophoresis. With this approach, hyaluronidase activity could be observed at pH4.8 under assay conditions in which CD44 and HYAL2 binding remained intact; additionally, weak hyaluronidase activity could be observed at pH6.8 under these conditions. This study suggests that CD44 and HYAL2 are bound at the surface of chondrocytes. The release of HYAL2 when CD44 is shed could provide a mechanism for weak hyaluronidase activity to occur within the more distant extracellular matrix of cartilage.

Interleukin-1β-induced Reduction of CD44 Ser-325 Phosphorylation in Human Epidermal Keratinocytes Promotes CD44 Homomeric Complexes, Binding to Ezrin, and Extended, Monocyte-adhesive Hyaluronan Coats

The proinflammatory cytokine interleukin-1β (IL-1β) attracts leukocytes to sites of inflammation. One of the recruitment mechanisms involves the formation of extended, hyaluronan-rich pericellular coats on local fibroblasts, endothelial cells, and epithelial cells. In the present work, we studied how IL-1β turns on the monocyte adhesion of the hyaluronan coat on human keratinocytes. IL-1β did not influence hyaluronan synthesis or increase the amount of pericellular hyaluronan in these cells. Instead, we found that the increase in the hyaluronan-dependent monocyte binding was associated with the CD44 of the keratinocytes. Although IL-1β caused a small increase in the total amount of CD44, a more marked impact was the decrease of CD44 phosphorylation at serine 325. At the same time, IL-1β increased the association of CD44 with ezrin and complex formation of CD44 with itself. Treatment of keratinocyte cultures with KN93, an inhibitor of calmodulin kinase 2, known to phosphorylate Ser-325 in CD44, caused similar effects as IL-1β (i.e. homomerization of CD44 and its association with ezrin) and resulted in increased monocyte binding to keratinocytes in a hyaluronan-dependent way. Overexpression of wild type CD44 standard form, but not a corresponding CD44 mutant mimicking the Ser-325-phosphorylated form, was able to induce monocyte binding to keratinocytes. In conclusion, treatment of human keratinocytes with IL-1β changes the structure of their hyaluronan coat by influencing the amount, post-translational modification, and cytoskeletal association of CD44, thus enhancing monocyte retention on keratinocytes.

Hyaluronan regulates bone morphogenetic protein-7-dependent prevention and reversal of myofibroblast phenotype

Hyaluronan (HA) promotes transforming growth factor (TGF)-β1-driven myofibroblast phenotype. However, HA can also have disease-limiting activity. Bone morphogenetic protein-7 (BMP7) is an antifibrotic cytokine that antagonizes TGF-β1, and isolated studies have demonstrated that HA can both mediate and modulate BMP7 responses. In this study, we investigated whether BMP7 can modulate HA in a manner that leads to prevention/reversal of TGF-β1-driven myofibroblast differentiation in human lung fibroblasts. Results demonstrated that BMP7 prevented and reversed TGF-β1-driven myofibroblast differentiation through a novel mechanism. BMP7 promoted the dissolution and internalization of cell-surface HA into cytoplasmic endosomes. Endosomal HA co-localized with the HA-degrading enzymes, hyaluronidase-1 and hyaluronidase-2 (Hyal2). Moreover, BMP7 showed differential regulation of CD44 standard and variant isoform expression, when compared with TGF-β1. In particular, BMP7 increased membrane expression of CD44v7/8. Inhibiting CD44v7/8 as well as blocking Hyal2 and the Na⁺/H⁺ exchanger-1 at the cell-surface prevented BMP7-driven HA internalization and BMP7-mediated prevention/reversal of myofibroblast phenotype. In summary, a novel mechanism of TGF-β1 antagonism by BMP7 is shown and identifies alteration in HA as critical in mediating BMP7 responses. In addition, we identify Hyal2 and CD44v7/8 as new potential targets for manipulation in prevention and reversal of fibrotic pathology.

DNA methylation array analyses identified breast cancer-associated HYAL2 methylation in peripheral blood

Breast cancer (BC) is the leading cause of cancer-related mortality in women worldwide. Changes in DNA methylation in peripheral blood could be associated with malignancy at early stage. However, the BC-associated DNA methylation signatures in peripheral blood were largely unknown. Here, we performed a genome-wide methylation screening and identified a BC-associated differentially methylated CpG site cg27091787 in the hyaluronoglucosaminidase 2 gene (HYAL2) (discovery round with 72 BC case and 24 controls: p = 2.61 × 10(-9) adjusted for cell-type proportions). The substantially decreased methylation of cg27091787 in BC cases was confirmed in two validation rounds (first validation round with 338 BC case and 507 controls: p < 0.0001; second validation round with 189 BC case and 189 controls: p < 0.0001). In addition to cg27091787, the decreased methylation of a 650-bp CpG island shore of HYAL2 was also associated with increased risk of BC. Moreover, the expression and methylation of HYAL2 were inversely correlated with a p-value of 0.006. To note, the BC-associated decreased HYAL2 methylation was replicated in the T-cell fraction (p = 0.034). The cg27091787 methylation level enabled a powerful discrimination of early-stage BC cases (stages 0 and I) from healthy controls [area under curve (AUC) = 0.89], and was robust for the detection of BC in younger women as well (age < 50, AUC = 0.87). Our study reveals a strong association between decreased HYAL2 methylation in peripheral blood and BC, and provides a promising blood-based marker for the detection of early BC.

Knock-down of CD44 regulates endothelial cell differentiation via NFκB-mediated chemokine production

A striking feature of microvascular endothelial cells is their capacity to fuse and differentiate into tubular structures when grown in three-dimensional (3D) extracellular matrices, in collagen or Matrigel, mimicking the in vivo blood vessel formation. In this study we demonstrate that human telomerase-immortalised foreskin microvascular endothelial (TIME) cells express high levels of the hyaluronan receptor CD44 and the hyaluronidase HYAL2. Knock-down of CD44 or HYAL2 resulted in an inability of TIME cells to form a tubular network, suggesting a key regulatory role of hyaluronan in controlling TIME cell tubulogenesis in 3D matrices. Knock-down of CD44 resulted in an upregulation of mRNA expression of the chemokines CXCL9 and CXCL12, as well as their receptors CXCR3 and CXCR4. This was accompanied by a defect maturation of the tubular structure network and increased phosphorylation of the inhibitor of NFκB kinase (IKK) complex and thus translocation of NFκB into the nucleus and activation of chemokine targed genes. Furthermore, the interaction between CD44 and hyaluronan determines the adhesion of breast cancer cells. In summary, our observations support the notion that the interaction between CD44 and hyaluronan regulates microvascular endothelial cell tubulogenesis by affecting the expression of cytokines and their receptors, as well as breast cancer dissemination.

Intracellular domain fragment of CD44 alters CD44 function in chondrocytes

The hyaluronan receptor CD44 undergoes sequential proteolytic cleavage at the cell surface. The initial cleavage of the CD44 extracellular domain is followed by a second intramembranous cleavage of the residual CD44 fragment, liberating the C-terminal cytoplasmic tail of CD44. In this study conditions that promote CD44 cleavage resulted in a diminished capacity to assemble and retain pericellular matrices even though sufficient non-degraded full-length CD44 remained. Using stable and transient overexpression of the cytoplasmic domain of CD44, we determined that the intracellular domain interfered with anchoring of the full-length CD44 to the cytoskeleton and disrupted the ability of the cells to bind hyaluronan and assemble a pericellular matrix. Co-immunoprecipitation assays were used to determine whether the mechanism of this interference was due to competition with actin adaptor proteins. CD44 of control chondrocytes was found to interact and co-immunoprecipitate with both the 65- and 130-kDa isoforms of ankyrin-3. Moreover, this interaction with ankyrin-3 proteins was diminished in cells overexpressing the CD44 intracellular domain. Mutating the putative ankyrin binding site of the transiently transfected CD44 intracellular domain diminished the inhibitory effects of this protein on matrix retention. Although CD44 in other cells types has been shown to interact with members of the ezrin/radixin/moesin (ERM) family of adaptor proteins, only modest interactions between CD44 and moesin could be demonstrated in chondrocytes. The data suggest that release of the CD44 intracellular domain into the cytoplasm of cells such as chondrocytes exerts a competitive or dominant-negative effect on the function of full-length CD44.

Activation of the kinin B1 receptor attenuates melanoma tumor growth and metastasis

Melanoma is a very aggressive tumor that does not respond well to standard therapeutic approaches, such as radio- and chemotherapies. Furthermore, acquiring the ability to metastasize in melanoma and many other tumor types is directly related to incurable disease. The B1 kinin receptor participates in a variety of cancer-related pathophysiological events, such as inflammation and angiogenesis. Therefore, we investigated whether this G protein-coupled receptor plays a role in tumor progression. We used a murine melanoma cell line that expresses the kinin B1 receptor and does not express the kinin B2 receptor to investigate the precise contribution of activation of the B1 receptor in tumor progression and correlated events using various in vitro and in vivo approaches. Activation of the kinin B1 receptor in the absence of B2 receptor inhibits cell migration in vitro and decreases tumor formation in vivo. Moreover, tumors formed from cells stimulated with B1-specific agonist showed several features of decreased aggressiveness, such as smaller size and infiltration of inflammatory cells within the tumor area, higher levels of pro-inflammatory cytokines implicated in the host anti-tumor immune response, lower number of cells undergoing mitosis, a poorer vascular network, no signs of invasion of surrounding tissues or metastasis and increased animal survival. Our findings reveal that activation of the kinin B1 receptor has a host protective role during murine melanoma tumor progression, suggesting that the B1 receptor could be a new anti-tumor GPCR and provide new opportunities for therapeutic targeting.

Inverse expression of hyaluronidase 2 and hyaluronan synthases 1-3 is associated with reduced hyaluronan content in malignant cutaneous melanoma

Background

Hyaluronan is an extracellular matrix glycosaminoglycan involved in invasion, proliferation and metastasis of various types of carcinomas. In many cancers, aberrant hyaluronan expression implicates disease progression and metastatic potential. Melanoma is an aggressive skin cancer. The role of hyaluronan in melanoma progression including benign nevi and lymph node metastases has not been investigated earlier, nor the details of its synthesis and degradation.

Methods

The melanocytic and dysplastic nevi, in situ melanomas, superficially and deeply invasive melanomas and their lymph node metastases were analysed immunohistochemically for the amount of hyaluronan, its cell surface receptor CD44, hyaluronan synthases 1–3 and hyaluronidases 1–2.

Results

Hyaluronan content of tumoral cells in deeply invasive melanomas and metastatic lesions was clearly reduced compared to superficial melanomas or benign lesions. Furthermore, hyaluronan content in the stromal cells of benign nevi was higher than in the premalignant or malignant tumors. The immunopositivity of hyaluronidase 2 was significantly increased in the premalignant and malignant lesions indicating its specific role in the degradation of hyaluronan during tumor progression. Similarly, the expression of hyaluronan synthases 1–2 and CD44 receptor was decreased in the metastases compared to the primary melanomas.

Conclusions

These findings suggest that the reciprocal relationship between the degrading and synthesizing enzymes account for the alterations in hyaluronan content during the growth of melanoma. These results provide new information about hyaluronan metabolism in benign, premalignant and malignant melanocytic tumors of the skin.

Hypotheses on the evolution of hyaluronan: a highly ironic acid

Hyaluronan is a high-molecular-weight glycosaminoglycan (GAG) prominent in the extracellular matrix. Emerging relatively late in evolution, it may have evolved to evade immune recognition. Chondroitin is a more ancient GAG and a possible hyaluronan precursor. Epimerization of a 4-hydroxyl in N-acetylgalactosamine in chondroitin to N-acetylglucosamine of hyaluronan is the only structural difference other than chain length between these two polymers. The axial 4-hydroxyl group extends out perpendicular from the equatorial plane of N-acetylgalactosamine in chondroitin. We suspect that this hydroxyl is a prime target for immune recognition. Conversion of a thumbs-up hydroxyl group into a thumbs-down position in the plane of the sugar endows hyaluronan with the ability to avoid immune recognition. Chitin is another potential precursor to hyaluronan. But regardless whether of chondroitin or of chitin origin, an ancient chondroitinase enzyme sequence seems to have been commandeered to catalyze the cleavage of the new hyaluronan substrate. The evolution of six hyaluronidase-like sequences in the human genome from a single chondroitinase as found in Caenorhabditis elegans can now be traced. Confirming our previous predictions, two duplication events occurred, with three hyaluronidase-like sequences occurring in the genome of Ciona intestinalis (sea squirt), the earliest known chordate. This was probably followed by en masse duplication, with six such genes present in the genome of zebra fish onwards. These events occurred, however, much earlier than predicted. It is also apparent on an evolutionary time scale that in several species, this gene family is continuing to evolve.

Hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid on bone metastasis of lung cancer

Hyaluronan is known to have pivotal roles in the growth, migration and invasion of malignant tumors. Bone metastases are critical lesions greatly impairing the quality of patients with malignancies. We investigated whether hyaluronan synthesis inhibitor supplements the inhibitory effects of zoledronic acid, which is a conventional therapeutic agent for bone metastasis. We examined the effects of methylumbelliferone, an inhibitor of hyaluronan synthesis and/or ZA on the tumorigenicity of one murine lung carcinoma and two human (A549, SK-MES-1) lung cancer cell lines in vitro. The interaction between methylumbelliferone and zoledronic acid was analyzed using Calcucyn software. With a murine bone metastasis model of lung cancer in vivo, we investigated the inhibitory effects and interaction of the two drugs on the progression of metastatic bone lesions. Methylumbelliferone or zoledronic acid treatment individually suppressed proliferation, migration and invasion of 3 cell lines, and combination treatment showed synergistic effects. Although methylumbelliferone as a single agent did not enhance apoptotic activity, it showed additive effects on apoptotic activity to those of zoledronic acid. Co-localization of CD44 and ezrin, which might be a pathway of hyaluronan signaling, was abrogated by methylumbelliferone treatment. Combination therapy showed additive inhibitory effects on metastatic bone lesions in vivo, which paralleled the inhibition of hyaluronan accumulation by methylumbelliferone, and inhibition of osteoclastogenesis. Although the detailed mechanisms underlying the synergistic or additive inhibitory effects of these two drugs should be further analyzed, inhibition of hyaluronan synthesis by methylumbelliferone is a promising novel therapeutic candidate for bone metastasis of lung cancer in addition to zoledronic acid.

Identification of amino acid residues required for the substrate specificity of human and mouse chondroitin sulfate hydrolase (conventional hyaluronidase-4)

Human hyaluronidase-4 (hHYAL4), a member of the hyaluronidase family, has no hyaluronidase activity, but is a chondroitin sulfate (CS)-specific endo-β-N-acetylgalactosaminidase. The expression of hHYAL4 is not ubiquitous but restricted to placenta, skeletal muscle, and testis, suggesting that hHYAL4 is not involved in the systemic catabolism of CS, but rather has specific functions in particular organs or tissues. To elucidate the function of hyaluronidase-4 in vivo, mouse hyaluronidase-4 (mHyal4) was characterized. mHyal4 was also demonstrated to be a CS-specific endo-β-N-acetylgalactosaminidase. However, mHyal4 and hHYAL4 differed in the sulfate groups they recognized. Although hHYAL4 strongly preferred GlcUA(2-O-sulfate)-GalNAc(6-O-sulfate)-containing sequences typical in CS-D, where GlcUA represents d-glucuronic acid, mHyal4 depolymerized various CS isoforms to a similar extent, suggesting broad substrate specificity. To identify the amino acid residues responsible for this difference, a series of human/mouse HYAL4 chimeric proteins and HYAL4 point mutants were generated, and their preference for substrates was investigated. A combination of the amino acid residues at 261-265 and glutamine at 305 was demonstrated to be essential for the enzymatic activity as well as substrate specificity of mHyal4.

Increased hyaluronan content and stromal cell CD44 associate with HER2 positivity and poor prognosis in human breast cancer

Previous in vitro studies have suggested interactions between hyaluronan (HA), CD44 and HER2. We have studied the expression of HA and CD44 in a material of 278 breast cancer cases, half of which were HER2-positive. Intense stromal HA staining was associated with HER2 positivity, large tumor size, lymph node positivity, hormone receptor negativity, poor differentiation, a high body mass index, increased relapse rate and shortened overall survival. Among the 139 HER2-positive cases, the relapse rate was associated with the intensity of stromal HA staining as most of the relapses occurred in the cases with intense stromal HA staining. The presence of HA in the carcinoma cells was related to the frequency of relapses as none of the patients without HA in carcinoma cells experienced a relapse, whereas 33.3% of those with a high percentage of HA-positive carcinoma cells suffered a relapse. CD44 positivity in carcinoma cells was related to poor differentiation, postmenopausal status and triple negative breast carcinoma. CD44 positivity in stromal cells was associated with HER2 positivity, large tumor size, hormone receptor negativity, poor differentiation, increased relapse rate and shortened overall survival. The association between HER2 positivity and intense stromal HA staining indicates that HA could be one of the factors involved in the unfavorable outcome of HER2-positive patients. This study also suggests that HA in breast carcinoma cells and CD44 in stromal cells may have clinical significance.

Renal interstitial hyaluronan: functional aspects during normal and pathological conditions

The glycosaminoglycan (GAG) hyaluronan (HA) is recognized as an important structural component of the extracellular matrix, but it also interacts with cells during embryonic development, wound healing, inflammation, and cancer; i.e., important features in normal and pathological conditions. The specific physicochemical properties of HA enable a unique hydration capacity, and in the last decade it was revealed that in the interstitium of the renal medulla, where the HA content is very high, it changes rapidly depending on the body hydration status while the HA content of the cortex remains unchanged at very low amounts. The kidney, which regulates fluid balance, uses HA dynamically for the regulation of whole body fluid homeostasis. Renomedullary HA elevation occurs in response to hydration and during dehydration the opposite occurs. The HA-induced alterations in the physicochemical characteristics of the interstitial space affects fluid flux; i.e., reabsorption. Antidiuretic hormone, nitric oxide, angiotensin II, and prostaglandins are classical hormones/compounds involved in renal fluid handling and are important regulators of HA turnover during variations in hydration status. One major producer of HA in the kidney is the renomedullary interstitial cell, which displays receptors and/or synthesis enzymes for the hormones mentioned above. During several kidney disease states, such as ischemia-reperfusion injury, tubulointerstitial inflammation, renal transplant rejection, diabetes, and kidney stone formation, HA is upregulated, which contributes to an abnormal phenotype. In these situations, cytokines and other growth factors are important stimulators. The immunosuppressant agent cyclosporine A is nephrotoxic and induces HA accumulation, which could be involved in graft rejection and edema formation. The use of hyaluronidase to reduce pathologically overexpressed levels of tissue HA is a potential therapeutic tool since diuretics are less efficient in removing water bound to HA in the interstitium. Although the majority of data describing the role of HA originate from animal and cell studies, the available data from humans demonstrate that an upregulation of HA also occurs in diabetic kidneys, in transplant-rejected kidneys, and during acute tubular necrosis. This review summarizes the current knowledge regarding interstitial HA in the role of regulating kidney function during normal and pathological conditions. It encompasses mechanistic insights into the background of the heterogeneous intrarenal distribution of HA; i.e., late nephrogenesis, its regulation during variations in hydration status, and its involvement during several pathological conditions. Changes in hyaluronan synthases, hyaluronidases, and binding receptor expression are discussed in parallel.