Role of promoter methylation in regulation of the mammalian heparanase gene

Heparanase-A single protein with multiple enzymatic and nonenzymatic functions

Heparanase (Hpa1) is expressed by tumor cells and cells of the tumor microenvironment and functions extracellularly to remodel the extracellular matrix (ECM) and regulate the bioavailability of ECM-bound factors, augmenting, among other effects, gene transcription, autophagy, exosome formation, and heparan sulfate (HS) turnover. Much of the impact of heparanase on tumor progression is related to its function in mediating tumor-host crosstalk, priming the tumor microenvironment to better support tumor growth, metastasis, and chemoresistance. The enzyme appears to fulfill some normal functions associated, for example, with vesicular traffic, lysosomal-based secretion, autophagy, HS turnover, and gene transcription. It activates cells of the innate immune system, promotes the formation of exosomes and autophagosomes, and stimulates signal transduction pathways via enzymatic and nonenzymatic activities. These effects dynamically impact multiple regulatory pathways that together drive tumor growth, dissemination, and drug resistance as well as inflammatory responses. The emerging premise is that heparanase expressed by tumor cells, immune cells, endothelial cells, and other cells of the tumor microenvironment is a key regulator of the aggressive phenotype of cancer, an important contributor to the poor outcome of cancer patients and a valid target for therapy. So far, however, antiheparanase-based therapy has not been implemented in the clinic. Unlike heparanase, heparanase-2 (Hpa2), a close homolog of heparanase (Hpa1), does not undergo proteolytic processing and hence lacks intrinsic HS-degrading activity, the hallmark of heparanase. Hpa2 retains the capacity to bind heparin/HS and exhibits an even higher affinity towards HS than heparanase, thus competing for HS binding and inhibiting heparanase enzymatic activity. It appears that Hpa2 functions as a natural inhibitor of Hpa1 regulates the expression of selected genes that maintain tissue hemostasis and normal function, and plays a protective role against cancer and inflammation, together emphasizing the significance of maintaining a proper balance between Hpa1 and Hpa2.

The Structure and Function of the Glycocalyx and Its Connection With Blood-Brain Barrier

The vascular endothelial glycocalyx is a dense, bush-like structure that is synthesized and secreted by endothelial cells and evenly distributed on the surface of vascular endothelial cells. The blood-brain barrier (BBB) is mainly composed of pericytes endothelial cells, glycocalyx, basement membranes, and astrocytes. The glycocalyx in the BBB plays an indispensable role in many important physiological functions, including vascular permeability, inflammation, blood coagulation, and the synthesis of nitric oxide. Damage to the fragile glycocalyx can lead to increased permeability of the BBB, tissue edema, glial cell activation, up-regulation of inflammatory chemokines expression, and ultimately brain tissue damage, leading to increased mortality. This article reviews the important role that glycocalyx plays in the physiological function of the BBB. The review may provide some basis for the research direction of neurological diseases and a theoretical basis for the diagnosis and treatment of neurological diseases.

The Heparanase Regulatory Network in Health and Disease

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

The HPSE Gene Insulator-A Novel Regulatory Element That Affects Heparanase Expression, Stem Cell Mobilization, and the Risk of Acute Graft versus Host Disease

The HPSE gene encodes heparanase (HPSE), a key player in cancer, inflammation, and autoimmunity. We have previously identified a strong HPSE gene enhancer involved in self-regulation of heparanase by negative feedback exerted in a functional rs4693608 single-nucleotide polymorphism (SNP) dependent manner. In the present study, we analyzed the HPSE gene insulator region, located in intron 9 and containing rs4426765, rs28649799, and rs4364254 SNPs. Our results indicate that this region exhibits HPSE regulatory activity. SNP substitutions lead to modulation of a unique DNA-protein complex that affects insulator activity. Analysis of interactions between enhancer and insulator SNPs revealed that rs4693608 has a major effect on HPSE expression and the risk of post-transplantation acute graft versus host disease (GVHD). The C alleles of insulator SNPs rs4364254 and rs4426765 modify the activity of the HPSE enhancer, resulting in altered HPSE expression and increased risk of acute GVHD. Moreover, rs4426765 correlated with HPSE expression in activated mononuclear cells, as well as with CD3 levels and lymphocyte counts following G-CSF mobilization. rs4363084 and rs28649799 were found to be associated with CD34⁺ levels. Our study provides new insight into the mechanism of HPSE gene regulation and its impact on normal and pathological processes in the hematopoietic system.

What Are the Potential Roles of Nuclear Perlecan and Other Heparan Sulphate Proteoglycans in the Normal and Malignant Phenotype

The recent discovery of nuclear and perinuclear perlecan in annulus fibrosus and nucleus pulposus cells and its known matrix stabilizing properties in tissues introduces the possibility that perlecan may also have intracellular stabilizing or regulatory roles through interactions with nuclear envelope or cytoskeletal proteins or roles in nucleosomal-chromatin organization that may regulate transcriptional factors and modulate gene expression. The nucleus is a mechano-sensor organelle, and sophisticated dynamic mechanoresponsive cytoskeletal and nuclear envelope components support and protect the nucleus, allowing it to perceive and respond to mechano-stimulation. This review speculates on the potential roles of perlecan in the nucleus based on what is already known about nuclear heparan sulphate proteoglycans. Perlecan is frequently found in the nuclei of tumour cells; however, its specific role in these diseased tissues is largely unknown. The aim of this review is to highlight probable roles for this intriguing interactive regulatory proteoglycan in the nucleus of normal and malignant cell types.

A guide to the composition and functions of the extracellular matrix

Extracellular matrix (ECM) is a dynamic 3-dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell-bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well-organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies.

Endothelial glycocalyx as an important factor in composition of blood-brain barrier

The blood‐brain barrier is a dynamic and complex neurovascular unit that protects neurons from somatic circulatory factors as well as regulates the internal environmental stability of the central nervous system. Endothelial glycocalyx is a critical component of an extended neurovascular unit that influences the structure of the blood‐brain barrier and plays various physiological functions, including an important role in maintaining normal neuronal homeostasis. Specifically, glycocalyx acts in physical and charge barriers, mechanical transduction, regulation of vascular permeability, modulation of inflammatory response, and anticoagulation. Since intact glycocalyx is necessary to maintain the stability and integrity of the internal environment of the blood‐brain barrier, damage to glycocalyx can lead to the dysfunction of the blood‐brain barrier. This review discusses the role of glycocalyx in the context of the substantial literature regarding the blood‐brain barrier research, in order to provide a theoretical basis for the diagnosis and treatment of neurological diseases as well as point to new breakthroughs and innovations in glycocalyx‐dependent blood‐brain barrier function.

Heparanase: Cloning, Function and Regulation

In 2019, we mark the 20th anniversary of the cloning of the human heparanase gene. Heparanase remains the only known enzyme to cleave heparan sulfate, which is an abundant component of the extracellular matrix. Thus, elucidating the mechanisms underlying heparanase expression and activity is critical to understanding its role in healthy and pathological settings. This chapter provides a historical account of the race to clone the human heparanase gene, describes the intracellular and extracellular function of the enzyme, and explores the various mechanisms regulating heparanase expression and activity at the gene, transcript, and protein level.

Chemoradiotherapy Increases Intratumor Heterogeneity of HPSE Expression in the Relapsed Glioblastoma Tumors

Adjuvant chemoradiotherapy is a standard treatment option for glioblastoma multiforme (GBM). Despite intensive care, recurrent tumors developed during the first year are fatal for the patients. Possibly contributing to this effect, among other causes, is that therapy induces changes of polysaccharide heparan sulfate (HS) chains in the cancer cells and/or tumor microenvironment. The aim of this study was to perform a comparative analysis of heparanase (HPSE) expression and HS content in different normal and GBM brain tissues. Immunohistochemical analysis revealed a significant decrease of HPSE protein content in the tumor (12-15-fold) and paratumorous (2.5-3-fold) GBM tissues compared with normal brain tissue, both in cellular and extracellular compartments. The relapsed GBM tumors demonstrated significantly higher intertumor and/or intratumor heterogeneity of HPSE and HS content and distribution compared with the matched primary ones (from the same patient) (n = 8), although overall expression levels did not show significant differences, suggesting local deterioration of HPSE expression with reference to the control system or by the treatment. Double immunofluorescence staining of various glioblastoma cell lines (U87, U343, LN18, LN71, T406) demonstrated a complex pattern of HPSE expression and HS content with a tendency towards a negative association of these parameters. Taken together, the results demonstrate the increase of intratumor heterogeneity of HPSE protein in relapsed GBM tumors and suggest misbalance of HPSE expression regulation by the adjuvant anti-GBM chemoradiotherapy.

Involvement of Heparanase in Gastric Cancer Progression and Immunotherapy

Heparanase is upregulated in various tumors, and its expression is closely associated with tumor growth, angiogenesis and metastasis, which accomplishes this mainly through degrading heparan sulfate and releasing heparin-binding growth factors thereby influencing multiple signaling pathways. In addition to its enzymatic degrading activity, heparanase can act via its non-enzymatic mechanisms that directly regulate various signaling. This review mainly focuses on the expression levels and role of heparanase in gastric cancer, and multiple genes and mechanisms regulating heparanase expression in gastric cancer. Furthermore, the development of heparanase-targeted immunotherapy and its potential application for treating gastric cancer are discussed.

Forty Years of Basic and Translational Heparanase Research

This review summarizes key developments in the heparanase field obtained 20 years prior to cloning of the HPSE gene and nearly 20 years after its cloning. Of the numerous publications and review articles focusing on heparanase, we have selected those that best reflect the progression in the field as well as those we regard important accomplishments with preference to studies performed by scientists and groups that contributed to this book. Apart from a general 'introduction' and 'concluding remarks', the abstracts of these studies are presented essentially as published along the years. We apologize for not being objective and not being able to include some of the most relevant abstracts and references, due to space limitation. Heparanase research can be divided into two eras. The first, initiated around 1975, dealt with identifying the enzyme, establishing the relevant assay systems and investigating its biological activities and significance in cancer and other pathologies. Studies performed during the first area are briefly introduced in a layman style followed by the relevant abstracts presented chronologically, essentially as appears in PubMed. The second era started in 1999 when the heparanase gene was independently cloned by 4 research groups [1-4]. As expected, cloning of the heparanase gene boosted heparanase research by virtue of the readily available recombinant enzyme, molecular probes, and anti-heparanase antibodies. Studies performed during the second area are briefly introduced followed by selected abstracts of key findings, arranged according to specific topics.

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

Heparanase is an endoglycosidase involved in remodeling the extracellular matrix and thereby in regulating multiple cellular processes and biological activities. It cleaves heparan sulfate (HS) side chains of HS proteoglycans into smaller fragments and hence regulates tissue morphogenesis, differentiation, and homeostasis. Heparanase is overexpressed in various carcinomas, sarcomas, and hematological malignancies, and its upregulation correlates with increased tumor size, tumor angiogenesis, enhanced metastasis, and poor prognosis. In contrast, knockdown or inhibition of heparanase markedly attenuates tumor progression, further underscoring the potential of anti-heparanase therapy. Heparanase inhibitors were employed to interfere with tumor progression in preclinical studies, and selected heparin mimetics are being examined in clinical trials. However, despite tremendous efforts, the discovery of heparanase inhibitors with high clinical benefit and minimal adverse effects remains a therapeutic challenge. This review discusses the key roles of heparanase in cancer progression focusing on the status of natural, chemically modified, and synthetic heparanase inhibitors in various types of malignancies.

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

Heparanase has been implicated in many pathological conditions, especially inflammation and cancer, attributed to its degradation of heparan sulfate, a crucial component maintaining the integrity of the extracellular matrix. By silencing the heparanase gene (HPSE) in MDA-MB-435s melanoma cells, we investigated the impact of this protein on gene transcription. Transcriptome sequencing yielded a list of 279 differentially expressed genes, of which 140 were up-regulated and 239 down-regulated. The 140 up-regulated genes were classified into a substantial set of gene ontology defined functions, for example, positive regulation of cell death, apoptotic process, response to cytokine, while 239 down-regulated genes classify only into the two categories: nucleosome and nucleosome assembly. Our focus was drawn to an array of 28 pro-apoptotic genes regulated by heparanase: real-time PCR experiments further validated up-regulation of EGR1, TXNIP, AXL, CYR61, LIMS2 and TNFRSF12A by at least 1.5-fold, among which EGR1, CYR61, and TNFRSF12A were confirmed on protein level. We demonstrated significantly increased apoptotic cells by TUNEL staining upon HPSE silencing, mediated by activation of caspase 3/PARP1 pathway. The pro-apoptotic gene expression and observation of apoptosis were extended to another melanoma cell line, MV3 cells, thus consolidating the anti-apoptosis effect of heparanase in melanoma cells.

Sulfotransferase and Heparanase: Remodeling Engines in Promoting Virus Infection and Disease Development

An extraordinary binding site generated in heparan sulfate (HS) structures, during its biosynthesis, provides a unique opportunity to interact with multiple protein ligands including viral proteins, and therefore adds tremendous value to this master molecule. An example of such a moiety is the sulfation at the C3 position of glucosamine residues in HS chain via 3-O sulfotransferase (3-OST) enzymes, which generates a unique virus-cell fusion receptor during herpes simplex virus (HSV) entry and spread. Emerging evidence now suggests that the unique patterns in HS sulfation assist multiple viruses in invading host cells at various steps of their life cycles. In addition, sulfated-HS structures are known to assist in invading host defense mechanisms and initiating multiple inflammatory processes; a critical event in the disease development. All these processes are detrimental for the host and therefore raise the question of how HS-sulfation is regulated. Epigenetic modulations have been shown to be implicated in these reactions during HSV infection as well as in HS modifying enzyme sulfotransferases, and therefore pose a critical component in answering it. Interestingly, heparanase (HPSE) activity is shown to be upregulated during virus infection and multiple other diseases assisting in virus replication to promote cell and tissue damage. These phenomena suggest that sulfotransferases and HPSE serve as key players in extracellular matrix remodeling and possibly generating unique signatures in a given disease. Therefore, identifying the epigenetic regulation of OST genes, and HPSE resulting in altered yet specific sulfation patterns in HS chain during virus infection, will be a significant a step toward developing potential diagnostic markers and designing novel therapies.

The heparanase inhibitor PG545 is a potent anti-lymphoma drug: Mode of action

It is now well recognized that heparanase, an endo-β-D-glucuronidase capable of cleaving heparan sulfate (HS) side chains at a limited number of sites, promotes tumorigenesis by diverse mechanisms. Compelling evidence strongly implies that heparanase is a viable target for cancer therapy, thus encouraging the development of heparanase inhibitors as anti-cancer therapeutics. Here, we examined the efficacy and mode of action of PG545, an HS-mimetic heparanase inhibitor, in human lymphoma. We found that PG545 exhibits a strong anti-lymphoma effect, eliciting lymphoma cell apoptosis. Notably, this anti-lymphoma effect involves ER stress response that was accompanied by increased autophagy. The persistent ER stress evoked by PG545 is held responsible for cell apoptosis because apoptotic cell death was attenuated by an inhibitor of PERK, a molecular effector of ER stress. Importantly, PG545 had no such apoptotic effect on naïve splenocytes, further encouraging the development of this compound as anti-lymphoma drug. Surprisingly, we found that PG545 also elicits apoptosis in lymphoma cells that are devoid of heparanase activity (i.e., Raji), indicating that the drug also exerts heparanase-independent function(s) that together underlie the high potency of PG545 in preclinical cancer models.

Methyl donor S-adenosylmethionine (SAM) supplementation attenuates breast cancer growth, invasion, and metastasis in vivo; therapeutic and chemopreventive applications

DNA hypomethylation coordinately targets various signaling pathways involved in tumor growth and metastasis. At present, there are no approved therapeutic modalities that target hypomethylation. In this regard, we examined the therapeutic plausibility of using universal methyl group donor S-adenosylmethionine (SAM) to block breast cancer development, growth, and metastasis through a series of studies in vitro using two different human breast cancer cell lines (MDA-MB-231 and Hs578T) and in vivo using an MDA-MB-231 xenograft model of breast cancer. We found that SAM treatment caused a significant dose-dependent decrease in cell proliferation, invasion, migration, anchorage-independent growth and increased apoptosis in vitro. These results were recapitulated in vivo where oral administration of SAM reduced tumor volume and metastasis in green fluorescent protein (GFP)-tagged MDA-MB-231 xenograft model. Gene expression analyses validated the ability of SAM to decrease the expression of several key genes implicated in cancer progression and metastasis in both cell lines and breast tumor xenografts. SAM was found to be bioavailable in the serum of experimental animals as determined by enzyme-linked immunosorbent assay and no notable adverse side effects were seen including any change in animal behavior. The results of this study provide compelling evidence to evaluate the therapeutic potential of methylating agents like SAM in patients with breast cancer to reduce cancer-associated morbidity and mortality.

S-adenosyl-methionine (SAM) alters the transcriptome and methylome and specifically blocks growth and invasiveness of liver cancer cells

S-adenosyl methionine (SAM) is a ubiquitous methyl donor that was reported to have chemo- protective activity against liver cancer, however the molecular footprint of SAM is unknown. We show here that SAM selectively inhibits growth, transformation and invasiveness of hepatocellular carcinoma cell lines but not normal primary liver cells. Analysis of the transcriptome of SAM treated and untreated liver cancer cell lines HepG2 and SKhep1 and primary liver cells reveals pathways involved in cancer and metastasis that are upregulated in cancer cells and are downregulated by SAM. Analysis of the methylome using bisulfite mapping of captured promoters and enhancers reveals that SAM hyper-methylates and downregulates genes in pathways of growth and metastasis that are upregulated in liver cancer cells. Depletion of two SAM downregulated genes STMN1 and TAF15 reduces cellular transformation and invasiveness, providing evidence that SAM targets are genes important for cancer growth and invasiveness. Taken together these data provide a molecular rationale for SAM as an anticancer agent.

Heparanase: roles in cell survival, extracellular matrix remodelling and the development of kidney disease

Heparanase has regulatory roles in various processes, including cell communication, gene transcription and autophagy. In addition, it is the only known mammalian endoglycosidase that is capable of degrading heparan sulfate (HS). HS chains are important constituents and organizers of the extracellular matrix (ECM), and have a key role in maintaining the integrity and function of the glomerular filtration barrier. In addition, HS chains regulate the activity of numerous bioactive molecules, such as cytokines and growth factors, at the cell surface and in the ECM. Given the functional diversity of HS, its degradation by heparanase profoundly affects important pathophysiological processes, including tumour development, neovascularization and inflammation, as well as progression of kidney disease. Heparanase-mediated degradation and subsequent remodelling of HS in the ECM of the glomerulus is a key mechanism in the development of glomerular disease, as exemplified by the complete resistance of heparanase-deficient animals to diabetes and immune-mediated kidney disease. This Review summarizes the role of heparanase in the development of kidney disease, and its potential as a therapeutic target.

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

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

Heparanase-neutralizing antibodies attenuate lymphoma tumor growth and metastasis

Heparanase is an endoglycosidase that cleaves heparan sulfate side chains of proteoglycans, resulting in disassembly of the extracellular matrix underlying endothelial and epithelial cells and associating with enhanced cell invasion and metastasis. Heparanase expression is induced in carcinomas and sarcomas, often associating with enhanced tumor metastasis and poor prognosis. In contrast, the function of heparanase in hematological malignancies (except myeloma) was not investigated in depth. Here, we provide evidence that heparanase is expressed by human follicular and diffused non-Hodgkin's B-lymphomas, and that heparanase inhibitors restrain the growth of tumor xenografts produced by lymphoma cell lines. Furthermore, we describe, for the first time to our knowledge, the development and characterization of heparanase-neutralizing monoclonal antibodies that inhibit cell invasion and tumor metastasis, the hallmark of heparanase activity. Using luciferase-labeled Raji lymphoma cells, we show that the heparanase-neutralizing monoclonal antibodies profoundly inhibit tumor load in the mouse bones, associating with reduced cell proliferation and angiogenesis. Notably, we found that Raji cells lack intrinsic heparanase activity, but tumor xenografts produced by this cell line exhibit typical heparanase activity, likely contributed by host cells composing the tumor microenvironment. Thus, the neutralizing monoclonal antibodies attenuate lymphoma growth by targeting heparanase in the tumor microenvironment.

DNA-hypomethylating agent, 5'-azacytidine, induces cyclooxygenase-2 expression via the PI3-kinase/Akt and extracellular signal-regulated kinase-1/2 pathways in human HT1080 fibrosarcoma cells

The cytosine analogue 5'-azacytidine (5'-aza) induces DNA hypomethylation by inhibiting DNA methyltransferase. In clinical trials, 5'-aza is widely used in epigenetic anticancer treatments. Accumulated evidence shows that cyclooxygenase-2 (COX-2) is overexpressed in various cancers, indicating that it may play a critical role in carcinogenesis. However, few studies have been performed to explore the molecular mechanism underlying the increased COX-2 expression. Therefore, we tested the hypothesis that 5'-aza regulates COX-2 expression and prostaglandin E2 (PGE2) production. The human fibrosarcoma cell line HT1080, was treated with various concentrations of 5'-aza for different time periods. Protein expressions of COX-2, DNA (cytosine-5)-methyltransferase 1 (DNMT1), pAkt, Akt, extracellular signal-regulated kinase (ERK), and phosphorylated ERK (pERK) were determined using western blot analysis, and COX-2 mRNA expression was determined using RT-PCR. PGE2 production was evaluated using the PGE2 assay kit. The localization and expression of COX-2 were determined using immunofluorescence staining. Treatment with 5'-aza induces protein and mRNA expression of COX-2. We also observed that 5'-aza-induced COX-2 expression and PGE2 production were inhibited by S-adenosylmethionine (SAM), a methyl donor. Treatment with 5'-aza phosphorylates PI3-kinase/Akt and ERK-1/2; inhibition of these pathways by LY294002, an inhibitor of PI3-kinase/Akt, or PD98059, an inhibitor of ERK-1/2, respectively, prevents 5'-aza-induced COX-2 expression and PGE2 production. Overall, these observations indicate that the hypomethylating agent 5'-aza modulates COX-2 expression via the PI3-kinase/Akt and ERK-1/2 pathways in human HT1080 fibrosarcoma cells.

DNA demethylation and invasive cancer: implications for therapeutics

One of the hallmarks of cancer is aberrant DNA methylation, which is associated with abnormal gene expression. Both hypermethylation and silencing of tumour suppressor genes as well as hypomethylation and activation of prometastatic genes are characteristic of cancer cells. As DNA methylation is reversible, DNA methylation inhibitors were tested as anticancer drugs with the idea that such agents would demethylate and reactivate tumour suppressor genes. Two cytosine analogues, 5-azacytidine (Vidaza) and 5-aza-2'-deoxycytidine, were approved by the Food and Drug Administration as antitumour agents in 2004 and 2006 respectively. However, these agents might cause activation of a panel of prometastatic genes in addition to activating tumour suppressor genes, which might lead to increased metastasis. This poses the challenge of how to target tumour suppressor genes and block cancer growth with DNA-demethylating drugs while avoiding the activation of prometastatic genes and precluding the morbidity of cancer metastasis. This paper reviews current progress in using DNA methylation inhibitors in cancer therapy and the potential promise and challenges ahead.

The increasing roles of epigenetics in breast cancer: Implications for pathogenicity, biomarkers, prevention and treatment

Nowadays, the mechanisms governing the occurrence of cancer are thought to be the consequence not only of genetic defects but also of epigenetic modifications. Therefore, epigenetic has become a very attractive and increasingly investigated field of research in order to find new ways of prevention and treatment of neoplasia, and this is particularly the case for breast cancer (BC). Thus, this review will first develop the main known epigenetic modifications that can occur in cancer and then expose the future role that control of epigenetic modifications might play in prevention, prognostication, follow-up and treatment of BC. Indeed, epigenetic biomarkers found in peripheral blood might become new tools to detect BC, to define its prognostic and to predict its outcome, whereas epi-drugs might have an increasing potential of development in the next future. However, if DNA methyltransferase inhibitors and histone desacetylase inhibitors have shown encouraging results in BC, their action remains nonspecific. Thus, additional clinical studies are needed to evaluate more precisely the effects of these molecules, even if they have provided encouraging results in cotreatment and combined therapies. This review will also deal with the potential of RNA interference (RNAi) as epi-drugs. Finally, we will focus on the potential prevention of BC through epigenetic based on diet and we will particularly develop the possible place of isothiocyanates from cruciferous vegetables or of Genistein from soybean in a dietary program that might potentially reduce the risk of BC in large populations.

Synergistic effects of combined DNA methyltransferase inhibition and MBD2 depletion on breast cancer cells; MBD2 depletion blocks 5-aza-2'-deoxycytidine-triggered invasiveness

5-Aza-2'-deoxycytidine (5-azaCdR) not only inhibits growth of non-invasive breast cancer cells but also increases their invasiveness through induction of pro-metastatic genes. Methylated DNA binding protein 2 (MBD2) is involved in silencing methylated tumor suppressor genes as well as activation of pro-metastatic genes. In this study, we show that a combination of MBD2 depletion and DNA methyltransferases (DNMT) inhibition in breast cancer cells results in a combined effect in vitro and in vivo, enhancing tumor growth arrest on one hand, while inhibiting invasiveness triggered by 5-azaCdR on the other hand. The combined treatment of MBD2 depletion and 5-azaCdR suppresses and augments distinct gene networks that are induced by DNMT inhibition alone. These data point to a potential new approach in targeting the DNA methylation machinery by combination of MBD2 and DNMT inhibitors.

Molecular epigenetics in the management of ovarian cancer: are we investigating a rational clinical promise?

Epigenetics is essentially a phenotypical change in gene expression without any alteration of the DNA sequence; the emergence of epigenetics in cancer research and mainstream oncology is fueling new hope. However, it is not yet known whether this knowledge will translate to improved clinical management of ovarian cancer. In this malignancy, women are still undergoing chemotherapy similar to what was approved in 1978, which to this day represents one of the biggest breakthroughs for treating ovarian cancer. Although liquid tumors are benefiting from epigenetically related therapies, solid tumors like ovarian cancer are not (yet?). Herein, we will review the science of molecular epigenetics, especially DNA methylation, histone modifications and microRNA, but also include transcription factors since they, too, are important in ovarian cancer. Pre-clinical and clinical research on the role of epigenetic modifications is also summarized. Unfortunately, ovarian cancer remains an idiopathic disease, for the most part, and there are many areas of patient management, which could benefit from improved technology. This review will also highlight the evidence suggesting that epigenetics may have pre-clinical utility in pharmacology and clinical applications for prognosis and diagnosis. Finally, drugs currently in clinical trials (i.e., histone deacetylase inhibitors) are discussed along with the promise for epigenetics in the exploitation of chemoresistance. Whether epigenetics will ultimately be the answer to better management in ovarian cancer is currently unknown; but we hope so in the future.

DNA methylation of heparanase promoter influences its expression and associated with the progression of human breast cancer

Heparanase promotes tumor invasion and metastasis in several malignancies including breast cancer. However, the roles and regulation mechanisms of heparanase during breast cancer progression are still not fully understood. The aim of this study is to determine the differential regulation of heparanase gene expression in specific stages of breast cancer by DNA methylation. We detected levels of heparanase expression and DNA methylation patterns of its promoter in breast cancer cell lines (MCF-7 and MDA-MB-435) and clinical tissues, respectively. It has been observed that heparanase is highly expressed in the invasive MDA-MB-435 cells with low methylation modification in the heparanase promoter. In contrast, lower expression of heparanase in MCF-7 cells is accompanied by higher methylation in the promoter. Treatment of MCF-7 cells with 5-aza-2'-deoxycytidine (5-aza-dC), a potent demethylating agent, results in induction of heparanase expression and higher invasion potential in vitro and leads to an advantage of tumor formation in vivo. In 54 tissue samples, cancer samples at late stages (stage IV) showed the highest heparanase expression accomplished by little DNA methylation. On the contrary, methylation prevalence is highest in normal tissue and inversely correlated with heparanase expression. A significant correlation between DNA methylation and clinical stage was demonstrated (p = 0.012). Collectively, these results demonstrate that DNA methylation play the regulation role in heparanase gene in different stages of breast cancer and present a direct effect on tumor progression.

Fumonisin B1 induces global DNA hypomethylation in HepG2 cells - An alternative mechanism of action

Fumonisin B1 (FB1), a common mycotoxin contaminant of maize, is known to inhibit sphingolipid biosynthesis and has been implicated in cancer promoting activity in animals and humans. FB1 disrupts DNA methylation and chromatin modifications in human hepatoma (HepG2) cells. We investigated the effect of FB1 on enzymes, DNA methyltransferases and demethylases, involved in chromatin maintenance and gross changes in structural integrity of DNA in HepG2 cells. We measured: (i) the expression of 84 key genes encoding enzymes known to modify genomic DNA and histones (superarray and qPCR); (ii) protein expression of DNA methyltransferases (DNMT1, DNMT3A and DNMT3B) and the major demethylase (MBD2) (western blotting); (iii) degree of DNA methylation by FACS using anti-5-MeCyt and (iv) DNA migration (single cell gel electrophoresis). FB1 significantly decreased the methyltransferase activities of DNMT1, DNMT3A and DNMT3B, and significantly up regulated the demethylases (MBD2 expression and activity, and KDM5B and KDM5C expression). FACS data showed FB1 significantly increased DNA hypomethylation and resulted in gross changes in structural DNA as evidenced by the Comet assay. We conclude that FB1 induces global DNA hypomethylation and histone demethylation that causes chromatin instability and may lead to liver tumourigenesis.

Heparanase in inflammation and inflammation-associated cancer

Recent years have seen a growing body of evidence that enzymatic remodeling of heparan sulfate proteoglycans profoundly affects a variety of physiological and pathological processes, including inflammation, neovascularization, and tumor development. Heparanase is the sole mammalian endoglycosidase that cleaves heparan sulfate. Extensively studied in cancer progression and aggressiveness, heparanase was recently implicated in several inflammatory disorders as well. Although the precise mode of heparanase action in inflammatory reactions is still not completely understood, the fact that heparanase activity is mechanistically important both in malignancy and in inflammation argues that this enzyme is a candidate molecule linking inflammation and tumorigenesis in inflammation-associated cancers. Elucidation of the specific effects of heparanase in cancer development, particularly when inflammation is a causal factor, will accelerate the development of novel therapeutic/chemopreventive interventions and help to better define target patient populations in which heparanase-targeting therapies could be particularly beneficial.

Versatile role of heparanase in inflammation

Heparanase is the only known mammalian endoglycosidase capable of degrading heparan sulfate glycosaminoglycan, both in extracellular space and within the cells. It is tightly implicated in cancer progression and over the past few decades significant progress has been made in elucidating the multiple functions of heparanase in malignant tumor development, neovascularization and aggressive behavior. Notably, current data show that in addition to its well characterized role in cancer, heparanase activity may represent an important determinant in the pathogenesis of several inflammatory disorders, such as inflammatory lung injury, rheumatoid arthritis and chronic colitis. Nevertheless, the precise mode of heparanase action in inflammatory reactions remains largely unclear and recent observations suggest that heparanase can either facilitate or limit inflammatory responses, when tissue/cell-specific contextual cues may dictate an outcome of heparanase action in inflammation. In this review the involvement of heparanase in modulation of inflammatory reactions is discussed through a few illustrative examples, including neuroinflammation, sepsis-associated lung injury and inflammatory bowel disease. We also discuss possible action of the enzyme in coupling inflammation and tumorigenesis in the setting of inflammation-triggered cancer.

Normal colon tissue and colon carcinoma show no difference in heparanase promoter methylation

INTRODUCTION

Heparanase, the sole heparan sulfate degrading enzyme, has a role in cellular invasion. Accordingly, a large number of studies have demonstrated an association between heparanase expression and tumor stage and patients' prognosis. In colon carcinoma, heparanase shows increased expression in tumor compared to normal tissue and its expression correlates with the presence of metastasis. One of the regulatory mechanisms of heparanase expression is de-methylation on its promoter. In the present study we evaluated the role of heparanase promoter methylation in colon carcinoma.

MATERIAL AND METHODS

Analysis of heparanase promoter methylation was done on 32 samples of colon carcinoma as well as 30 samples of normal colonic mucosa. DNA was extracted from FFPE tissue and subjected to bisulfite conversion. The relative fraction of methylated and unmethylated DNA was evaluated using quantitative real-time PCR.

RESULTS

The fraction of methylated DNA was 1 ± 3.4% in the colon carcinoma group, and 2.5 ± 3.3% in the normal colon group (P=0.11). Only one case in the normal group and one case in the tumor group showed more than 10% methylation in the heparanase promoter.

CONCLUSION

We did not find any significant difference in heparanase promoter methylation between colon carcinoma and normal colonic mucosa, suggesting that heparanase overexpression in colon carcinoma is mediated by other mechanisms.

Heparanase enzyme in chronic inflammatory bowel disease and colon cancer

Heparanase is the sole mammalian endoglycosidase that cleaves heparan sulfate, the key polysaccharide of the extracellular matrix and basement membranes. Enzymatic cleavage of heparan sulfate profoundly affects a variety of physiological and pathological processes, including morphogenesis, neovascularization, inflammation, and tumorigenesis. Critical involvement of heparanase in colorectal tumor progression and metastatic spread is widely documented; however, until recently a role for heparanase in the initiation of colon carcinoma remained underappreciated. Interestingly, the emerging data that link heparanase to chronic inflammatory bowel conditions, also suggest contribution of the enzyme to colonic tumor initiation, at least in the setting of colitis-associated cancer. Highly coordinated interplay between intestinal heparanase and immune cells (i.e., macrophages) preserves chronic inflammatory conditions and creates a tumor-promoting microenvironment. Here we review the action of heparanase in colon tumorigenesis and discuss recent findings, pointing to a role for heparanase in sustaining immune cell-epithelial crosstalk that underlies intestinal inflammation and the associated cancer.

De novo DNA methyltransferases: oncogenes, tumor suppressors, or both?

Aberrant promoter DNA hypermethylation of tumor suppressor genes is a hallmark of cancer. This alteration is largely dependent on the action of de novo DNA methyltransferases (DNMTs) early during tumor progression, which supports the oncogenic role for these enzymes. However, recent research has identified several inactivating mutations of de novo DNMTs in various types of tumor. In addition, it has been shown that loss of de novo DNA methylation activity at advanced tumor stages leads to the promoter DNA demethylation-dependent expression of specific oncogenes. These new data support the notion that de novo DNMTs also have an important role in the maintenance of DNA methylation and suggest that, in addition to acting as oncogenes, they also behave as tumor suppressors. This potential dual role might have clinical implications, as DNMTs are currently considered bona fide targets in cancer therapy.

DNA methylation signatures for breast cancer classification and prognosis

Changes in gene expression that reset a cell program from a normal to a diseased state involve multiple genetic circuitries, creating a characteristic signature of gene expression that defines the cell's unique identity. Such signatures have been demonstrated to classify subtypes of breast cancers. Because DNA methylation is critical in programming gene expression, a change in methylation from a normal to diseased state should be similarly reflected in a signature of DNA methylation that involves multiple gene pathways. Whole-genome approaches have recently been used with different levels of success to delineate breast-cancer-specific DNA methylation signatures, and to test whether they can classify breast cancer and whether they could be associated with specific clinical outcomes. Recent work suggests that DNA methylation signatures will extend our ability to classify breast cancer and predict outcome beyond what is currently possible. DNA methylation is a robust biomarker, vastly more stable than RNA or proteins, and is therefore a promising target for the development of new approaches for diagnosis and prognosis of breast cancer and other diseases. Here, I review the scientific basis for using DNA methylation signatures in breast cancer classification and prognosis. I discuss the role of DNA methylation in normal gene regulation, the aberrations in DNA methylation in cancer, and candidate-gene and whole-genome approaches to classify breast cancer subtypes using DNA methylation markers.

Prostaglandin E2 promotes intestinal tumor growth via DNA methylation

Although aberrant DNA methylation is considered to be one of the key ways by which tumor-suppressor and DNA-repair genes are silenced during tumor initiation and progression, the mechanisms underlying DNA methylation alterations in cancer remain unclear. Here we show that prostaglandin E(2) (PGE(2)) silences certain tumor-suppressor and DNA-repair genes through DNA methylation to promote tumor growth. These findings uncover a previously unrecognized role for PGE(2) in the promotion of tumor progression.

Neonatal exposure to high doses of 17β-estradiol results in inhibition of heparanase-1 expression in the adult prostate

Heparanase-1 (HPSE-1) is an endoglycosidase that cleaves heparan sulfate. The physiological functions of HPSE-1 include embryo development, hair growth, wound healing, tumor growth, angiogenesis, metastasis, and inflammation. HPSE-1 expression was found to increase temporarily in the rat ventral prostate (VP) after castration. The promoter region of the Hpse-1 gene has estrogen-responsive elements, suggesting that the gene is regulated by estrogens. In this study, we investigated the expression of HPSE-1 in the VP of 90-day-old rats after neonatal exposure to a high dose of 17β-estradiol. HPSE-1 was not found by immunohistochemistry in the epithelium of estrogenized animals. To determine whether inhibition of Hpse-1 expression in the epithelium was due to pre- or post-transcriptional regulation, epithelial cells were isolated by centrifugation in Percoll gradient and the presence of Hpse-1 mRNA was investigated by RT-PCR. Hpse-1 mRNA was not detected in the estrogenized animals. Considering that Hpse-1 transcription could be inhibited by DNA methylation, we used the methylation-sensitive restriction enzyme HpaII and PCR to show that a single CCGG site at position +185 was more frequently methylated in the epithelium of estrogenized than in control animals. Immunohistochemistry for 5-methylcytidine revealed that the epithelial cell nuclei in estrogenized animals were heavily methylated. These results suggest that Hpse-1 expression was blocked in the epithelial cells of the VP, by estrogen imprinting by a pre-transcriptional mechanism involving DNA methylation.

The heparanase system and tumor metastasis: is heparanase the seed and soil?

Tumor metastasis, the leading cause of cancer patients' death, is still insufficiently understood. While concepts and mechanisms of tumor metastasis are evolving, it is widely accepted that cancer metastasis is accompanied by orchestrated proteolytic activity executed by array of proteases. While matrix metalloproteinases (MMPs) attracted much attention, other proteases constitute the tumor milieu, of which a large family consists of cysteine proteases named cathepsins. Like MMPs, some cathepsins are often upregulated in cancer and, once secreted or localized to the cell surface, can degrade components of the extracellular matrix. In addition, cathepsin L is held responsible for processing and activation of heparanase, an endo-β-glucuronidase capable of cleaving heparan sulfate side chains of heparan sulfate proteoglycans, activity that is strongly implicated in cell dissemination associated with tumor metastasis, angiogenesis, and inflammation. In this review, we discuss recent progress in heparanase research focusing on heparanase-related molecules namely, cathepsin L and heparanase 2 (Hpa2), a heparanase homolog.

Definition of the landscape of promoter DNA hypomethylation in liver cancer

We use hepatic cellular carcinoma (HCC), one of the most common human cancers, as a model to delineate the landscape of promoter hypomethylation in cancer. Using a combination of methylated DNA immunoprecipitation and hybridization with comprehensive promoter arrays, we have identified approximately 3,700 promoters that are hypomethylated in tumor samples. The hypomethylated promoters appeared in clusters across the genome suggesting that a high-level organization underlies the epigenomic changes in cancer. In normal liver, most hypomethylated promoters showed an intermediate level of methylation and expression, however, high-CpG dense promoters showed the most profound increase in gene expression. The demethylated genes are mainly involved in cell growth, cell adhesion and communication, signal transduction, mobility, and invasion; functions that are essential for cancer progression and metastasis. The DNA methylation inhibitor, 5-aza-2'-deoxycytidine, activated several of the genes that are demethylated and induced in tumors, supporting a causal role for demethylation in activation of these genes. Previous studies suggested that MBD2 was involved in demethylation of specific human breast and prostate cancer genes. Whereas MBD2 depletion in normal liver cells had little or no effect, we found that its depletion in human HCC and adenocarcinoma cells resulted in suppression of cell growth, anchorage-independent growth and invasiveness as well as an increase in promoter methylation and silencing of several of the genes that are hypomethylated in tumors. Taken together, the findings define the potential functional role of hypomethylation in cancer.

The implications of DNA methylation for toxicology: toward toxicomethylomics, the toxicology of DNA methylation

Identifying agents that have long-term deleterious impact on health but exhibit no immediate toxicity is of prime importance. It is well established that long-term toxicity of chemicals could be caused by their ability to generate changes in the DNA sequence through the process of mutagenesis. Several assays including the Ames test and its different modifications were developed to assess the mutagenic potential of chemicals (Ames, B. N., Durston, W. E., Yamasaki, E., and Lee, F. D. (1973a). Carcinogens are mutagens: a simple test system combining liver homogenates for activation and bacteria for detection. Proc. Natl. Acad. Sci. U.S.A. 70, 2281-2285; Ames, B. N., Lee, F. D., and Durston, W. E. (1973b). An improved bacterial test system for the detection and classification of mutagens and carcinogens. Proc. Natl. Acad. Sci. U.S.A. 70, 782-786). These tests have also been employed for assessing the carcinogenic potential of compounds. However, the DNA molecule contains within its chemical structure two layers of information. The DNA sequence that bears the ancestral genetic information and the pattern of distribution of covalently bound methyl groups on cytosines in DNA. DNA methylation patterns are generated by an innate program during gestation but are attuned to the environment in utero and throughout life including physical and social exposures. DNA function and health could be stably altered by exposure to environmental agents without changing the sequence, just by changing the state of DNA methylation. Our current screening tests do not detect agents that have long-range impact on the phenotype without altering the genotype. The realization that long-range damage could be caused without changing the DNA sequence has important implications on the way we assess the safety of chemicals, drugs, and food and broadens the scope of definition of toxic agents.

Effects of specific DNMT gene depletion on cancer cell transformation and breast cancer cell invasion; toward selective DNMT inhibitors

A hallmark of cancer is aberrant DNA methylation, consisting of global hypomethylation and regional hypermethylation of tumor suppressor genes. DNA methyltransferase inhibitors have been recognized as promising candidate anticancer drugs. Drug development has focused on DNA methylation inhibitors with the goal of activating tumor suppressor genes silenced by DNA methylation. 5-azacytidine (5-AC; Vidaza), a global DNA methyltransferase inhibitor, was Food and Drug Administration approved to treat myelodysplastic syndromes and is clinically tested for solid tumors. In this paper, it was demonstrated that 5'-aza-2'-deoxycytidine (5-azaCdR) activated both silenced tumor suppressor genes and pro-metastatic genes by demethylation, raising the concern that it would promote metastasis. 5-AzaCdR treatment increased the invasiveness of non-invasive breast cancer cell lines MCF-7 cells and ZR-75-1 and dramatically induced pro-metastatic genes; Urokinase plasminogen activator (uPA), matrix metalloproteinase 2 (MMP2), metastasis-associated gene (H-MTS1; S100A4) and C-X-C chemokine receptor 4 (CXCR4). The hypothesis that the blocking of cellular transformation activity of DNA methyltransferase inhibitor could be separated from the pro-metastatic activity was tested using short interfering RNA (siRNA) targeted to the different DNA methyltransferase (DNMT) genes. Although depletion of DNMT1 had the strongest effect on colony growth suppression in cellular transformation assays, it did not result in demethylation and activation of uPA, S100A4, MMP2 and CXCR4 in MCF-7 cells. Depletion of DNMT1 did not induce cellular invasion in MCF-7 and ZR-75-1 non-invasive breast cancer cell lines. These data have implications on the design of new DNA methyltransferase inhibitor and on the proper utilization of current inhibitors.

Preferential up-regulation of heparanase and cyclooxygenase-2 in carcinogenesis of Barrett's oesophagus and intestinal-type gastric carcinoma

AIMS

Metaplastic changes secondary to chronic inflammation at the gastro-oesophageal junction and at the pyloric antrum are recognized as the premalignant conditions of Barrett's oesophageal adenocarcinoma and intestinal-type gastric carcinoma (GC), respectively. Heparanase (HPSE) and cyclooxygenase (COX)-2 have been proved to play critical roles in inflammation as well as in cancer. The aim was to examine the meaning of their expression in inflammation-related carcinogenesis.

METHODS AND RESULTS

First, expression of HPSE and COX-2 in 78 clinical tissues of Barrett's oesophagus was examined by immunohistochemistry and in situ hybridization. Their expression was increased during the metaplasia-dysplasia sequence with increased neovascularization. Successively, their expression in Barrett's dysplasia was compared with that of GC (22 cases of diffuse-type and 10 of intestinal-type). Interestingly, the expression pattern in Barrett's dysplasia was similar to that in intestinal-type GC, which mainly arises from chronic inflammation. Furthermore, cultured cell lines isolated from differentiated GC tissues, which are often found to be of intestinal-type, revealed up-regulated mRNA expression of HPSE and COX-2.

CONCLUSIONS

HPSE and COX-2 are preferentially up-regulated in Barrett's oesophagus and intestinal-type GC. These molecules may play an important role during the development of inflammation-related adenocarcinoma of the upper gastrointestinal tract.

Proteoglycans in health and disease: new concepts for heparanase function in tumor progression and metastasis

Heparanase is an endo-β-D-glucuronidase capable of cleaving heparan sulfate side chains at a limited number of sites, yielding heparan sulfate fragments of still appreciable size. Importantly, heparanase activity correlates with the metastatic potential of tumor-derived cells, attributed to enhanced cell dissemination as a consequence of heparan sulfate cleavage and remodeling of the extracellular matrix and basement membrane underlying epithelial and endothelial cells. Similarly, heparanase activity is implicated in neovascularization, inflammation and autoimmunity, involving the migration of vascular endothelial cells and activated cells of the immune system. The cloning of a single human heparanase cDNA 10 years ago enabled researchers to critically approve the notion that heparan sulfate cleavage by heparanase is required for structural remodeling of the extracellular matrix, thereby facilitating cell invasion. Progress in the field has expanded the scope of heparanase function and its significance in tumor progression and other pathologies. Notably, although heparanase inhibitors attenuated tumor progression and metastasis in several experimental systems, other studies revealed that heparanase also functions in an enzymatic activity-independent manner. Thus, inactive heparanase was noted to facilitate adhesion and migration of primary endothelial cells and to promote phosphorylation of signaling molecules such as Akt and Src, facilitating gene transcription (i.e. vascular endothelial growth factor) and phosphorylation of selected Src substrates (i.e. endothelial growth factor receptor). The concept of enzymatic activity-independent function of heparanase gained substantial support by the recent identification of the heparanase C-terminus domain as the molecular determinant behind its signaling capacity. Identification and characterization of a human heparanase splice variant (T5) devoid of enzymatic activity and endowed with protumorigenic characteristics, elucidation of cross-talk between heparanase and other extracellular matrix-degrading enzymes, and identification of single nucleotide polymorphism associated with heparanase expression and increased risk of graft versus host disease add other layers of complexity to heparanase function in health and disease.

Post-transcriptional regulation of heparanase gene expression by a 3' AU-rich element

Heparanase up-regulation was documented in an increasing number of human carcinomas, associated with poor prognosis. The purpose of the current study was to identify mechanisms responsible for heparanase induction. We provide evidence that heparanase expression is regulated at the post-transcriptional level by sequences at the 3' untranslated region (3' UTR) of the gene. Constructing the 3' UTR immediately following the heparanase cDNA reduces heparanase enzymatic activity and protein levels, resulting in decreased cellular invasion capacity. We further identified a 185-bp sequence within the 3' UTR that mediates heparanase down-regulation, and characterized an adenine (A)/uracil (U)-rich consensus element (ARE) within this region. Deletion of the entire 185-bp region or the ARE eliminated the inhibitory effect of the 3' UTR, resulting in elevated heparanase levels and formation of larger tumor xenografts indistinguishable from those produced by heparanase-overexpressing cells in terms of size, vascularization, and Akt activation. These results suggest that loss of the ARE is an important regulatory mechanism contributing to heparanase induction in human cancer.

Quantitative analysis of heparanase gene expression in normal cervical, cervical intraepithelial neoplastic, and cervical carcinoma tissues

Heparanase is an endoglycosidase that specifically cleaves heparan sulfate side chains of heparan sulfate proteoglycans, the major proteoglycans in the extracellular matrix and cell surfaces. Traditionally, heparanase activity was implicated in cellular invasion associated with angiogenesis, inflammation, and cancer metastasis. More recently, heparanase up-regulation was documented in an increasing number of primary human tumors. Iotan this study, we sought to investigate the expression of heparanase messenger RNA (mRNA) in normal cervical tissue and intraepithelial cervical lesion and its clinicopathologic importance in invasive cervical cancer. Gene expression of heparanase was assessed by quantitative real-time reverse transcriptase polymerase chain reaction in 28 normal cervical, 26 intraepithelial neoplastic, and 48 cervical cancer tissue samples. Heparanase mRNA expression was different between the 3 groups and lower in normal cervical specimens in relationship with intraepithelial cervical lesions and invasive cervical cancer tissue samples (P = 0.048). Gradually increasing expression of heparanase was evident as the cells progressed from low-grade to high-grade squamous intraepithelial lesions (P = 0.002). In invasive cervical cancer cases, there was a direct correlation between heparanase expression and tumor size (P = 0.002). In cases treated with radical hysterectomy and pelvic lymphadenectomy, the heparanase mRNA expression was significantly higher in tumors exhibiting lymph vascular space invasion (P = 0.044) and in cases with big tumor size (P = 0.005). In our study, we did not find any significant correlation between disease-free and overall survival rates and expression of heparanase (P = 0.396 and P = 0.712, respectively). The results of this study suggest that the gene expression of heparanase in cervical cancer enhances growth, invasion, and angiogenesis of the tumor and may have therapeutic applications.