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Biomedical subjects

I Vlodavsky

Publications and source records attributed to I Vlodavsky.

At least 19 recordsLinked to original sources
PubMed2006

Increased expression of heparanase in overt diabetic nephropathy.

In overt diabetic nephropathy (DNP), an increase in the permeability of the glomerular basement membrane (GBM) has been associated with a loss of negatively charged heparan sulfates (HS) in the GBM. Heparanase (HPSE), an endo-beta(1-4)-D-glucuronidase, can cleave HS and could be a potential candidate for the degradation of glomerular HS, leading to the development of proteinuria. We analyzed whether changes in HS expression are associated with HPSE expression in overt DNP. Immunofluorescence staining was performed to analyze HS, HPSE, and agrin core protein expression in kidney biopsies from patients with overt DNP and from rats and mice with streptozotocin (STZ)-induced diabetes. We also investigated the effect of transgenic HPSE overexpression in mice on glomerular HS and agrin expression. We demonstrate that the loss of GBM HS (-50%) and tubular HS (-60%) is associated with a four-fold increased HPSE expression in overt DNP. In addition, glomerular HPSE expression is upregulated in rats (messenger RNA (mRNA) 2.5-fold, protein three-fold) and mice (mRNA seven-fold, protein 1.5-fold) with STZ-induced diabetes. Furthermore, transgenic HPSE overexpression results in disappearance of HS, whereas expression of the core protein agrin remains unaltered. Our observations suggest that HPSE is involved in the pathogenesis of proteinuria in overt DNP by degradation of HS.

Aged↗
PubMed2006

Heparanase induces tissue factor expression in vascular endothelial and cancer cells.

BACKGROUND: Over-expression of tissue factor (TF) and activation of the coagulation system are common in cancer patients. Heparanase is an endo-beta-D-glucuronidase that cleaves heparan sulfate chains on cell surfaces and in the extracellular matrix, activity that closely correlates with cell invasion, angiogenesis and tumor metastasis. The study was undertaken to investigate the involvement of heparanase in TF expression. METHODS: Tumor-derived cell lines were transfected with heparanase cDNA and TF expression was examined. The effect of exogenous addition of active and inactive heparanase on TF expression and activity was studied in tumor cell lines and primary human umbilical vein endothelial cells. TF expression was also explored in heparanase over-expressing transgenic (Tg) mice. Blast cells were collected from acute leukemia patients and TF and heparanase expression levels were analyzed. RESULTS: Over-expression of heparanase in tumor-derived cell lines resulted in a 2-fold increase in TF expression levels, and a similar trend was observed in heparanase Tg mice in vivo. Likewise, exogenous addition of heparanase to endothelial or tumor-derived cells resulted in enhanced TF expression and activity. Interestingly, TF expression was also induced in response to enzymatically inactive heparanase, suggesting that this effect was independent of heparanase enzymatic activity. The regulatory effect of heparanase on TF expression involved activation of the p38 signaling pathway. A positive correlation between TF expression levels and heparanase activity was found in blasts collected from 22 acute leukemia patients. CONCLUSIONS: Our results indicate that in addition to its well-known function as an enzyme paving a way for invading cells, heparanase also participates in the regulation of TF gene expression and its related coagulation pathways.

Blood Coagulation↗
PubMed2006

Halofuginone inhibits NF-kappaB and p38 MAPK in activated T cells.

Halofuginone, a low molecular weight plant alkaloid, inhibits collagen alpha1 (I) gene expression in several animal models and in patients with fibrotic disease, including scleroderma and graft-versus-host disease. In addition, halofuginone has been shown to inhibit angiogenesis and tumor progression. It was demonstrated recently that halofuginone inhibits transforming growth factor-beta (TGF-beta), an important immunomodulator. The present study was undertaken to explore the effects of halofuginone on activated T cells. Peripheral blood T cells were activated by anti-CD3 monoclonal antibodies in the absence and presence of halofuginone and assessed for nuclear factor (NF)-kappaB activity, production of tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma), T cell apoptosis, chemotaxis, and phosphorylation of p38 mitogen-activated protein kinase (MAPK). A delayed-type hypersensitivity (DTH) model was applied to investigate the effect of halofuginone on T cells in vivo. Preincubation of activated peripheral blood T cells with 10-40 ng/ml halofuginone resulted in a significant dose-dependent decrease in NF-kappaB activity (80% inhibition following incubation with 40 ng halofuginone, P = 0.002). In addition, 40 ng/ml halofuginone inhibited secretion of TNF-alpha, IFN-gamma, interleukin (IL)-4, IL-13, and TGF-beta (P < 0.005). Similarly, halofuginone inhibited the phosphorylation of p38 MAPK and apoptosis in activated T cells (P = 0.0001 and 0.005, respectively). In contrast, T cell chemotaxis was not affected. Halofuginone inhibited DTH response in mice, indicating suppression of T cell-mediated inflammation in vivo. Halofuginone inhibits activated peripheral blood T cell functions and proinflammatory cytokine production through inhibition of NF-kappaB activation and p38 MAPK phosphorylation. It also inhibited DTH response in vivo, making it an attractive immunomodulator and anti-inflammatory agent.

Apoptosis↗
PubMed2006

Tumor suppressor p53 regulates heparanase gene expression.

Mammalian heparanase degrades heparan sulfate, the most prominent polysaccharide of the extracellular matrix. Causal involvement of heparanase in tumor progression is well documented. Little is known, however, about mechanisms that regulate heparanase gene expression. Mutational inactivation of tumor suppressor p53 is the most frequent genetic alteration in human tumors. p53 is a transcription factor that regulates a wide variety of cellular promoters. In this study, we demonstrate that wild-type (wt) p53 binds to heparanase promoter and inhibits its activity, whereas mutant p53 variants failed to exert an inhibitory effect. Moreover, p53-H175R mutant even activated heparanase promoter activity. Elimination or inhibition of p53 in several cell types resulted in a significant increase in heparanase gene expression and enzymatic activity. Trichostatin A abolished the inhibitory effect of wt p53, suggesting the involvement of histone deacetylation in negative regulation of the heparanase promoter. Altogether, our results indicate that the heparanase gene is regulated by p53 under normal conditions, while mutational inactivation of p53 during cancer development leads to induction of heparanase expression, providing a possible explanation for the frequent increase of heparanase levels observed in the course of tumorigenesis.

Animals↗
PubMed2006

Heparanase expression in nasopharyngeal carcinoma inversely correlates with patient survival.

AIMS: To determine the expression and prognostic significance of heparanase in nasopharyngeal carcinoma (NPC). METHODS: Immunohistochemistry was performed on formalin-fixed paraffin-embedded sections of 46 patients with NPC. Clinical and immunohistochemical data were correlated with gender, age, histological type, Epstein-Barr virus (EBV) status, stage and survival. RESULTS: Heparanase immunoreactivity was found in 35% (16/46) of specimens. The cumulative survival of patients diagnosed as heparanase negative (n = 30) at 10 years was 70%. In contrast, the cumulative survival of patients diagnosed as heparanase positive (n = 16) at 10 years was 25%, differences that are highly statistically significant (P = 0.03). No significant correlations were found between heparanase immunoreactivity and gender, age, EBV status, tumour histology or tumour stage. CONCLUSION: Heparanase expression is inversely correlated with survival of NPC patients, clearly indicating that heparanase is a reliable prognostic factor for this malignancy, and further supports the notion that heparanase is a valid target for the development of anti-cancer drugs.

Adolescent↗
PubMed2006

Heparanase neutralizes the anticoagulation properties of heparin and low-molecular-weight heparin.

BACKGROUND: Heparanase is a mammalian endo-D-glucuronidase that cleaves heparan sulfate (HS) in the extracellular matrix and cell surface. It is preferentially expressed by cells of the immune system and tumor cells. Heparanase overexpression in experimental tumor models results in increased angiogenesis and metastasis. Heparin and low-molecular weight heparin (LMWH) inhibit HS degradation by heparanase. OBJECTIVE: To investigate whether heparanase cleaves heparin and LMWH, and elucidate its effect on blood coagulation. METHODS: Heparin and LMWH were incubated with recombinant heparanase and subjected to measurements of molecular size (size exclusion chromatography) and anticoagulant activity (plasma APTT-activated thromboplastin time, and anti-Xa activity). APTT was also measured in plasma samples of transgenic mice overexpressing heparanase, in comparison with control mice. RESULTS: Incubation of heparin and LMWH with heparanase resulted in degradation of these substrates, as revealed by a significant decrease in their molecular weight. This was correlated with a marked suppression of the anticoagulant activity of heparin and LMWH, as indicated by a decreased effect on APTT and anti-Xa activity, respectively, when human plasma was added. Transgenic mice overexpressing heparanase exhibited a significantly shorter APTT than control mice. CONCLUSION: Heparanase is capable of degrading heparin and LMWH, so that its overexpression by tumor cells may contribute to heparin resistance, commonly occurring in cancer patients. In view of the complexity of the currently available heparanase activity assays, we propose an indirect approach to quantify heparanase activity by measuring the decrease in plasma APTT or anti-Xa activity exerted by the enzyme under the defined conditions.

Animals↗
PubMed2004

Suppression of hepatocellular carcinoma growth in mice by the alkaloid coccidiostat halofuginone.

Halofuginone, a widely used alkaloid coccidiostat, is a potent inhibitor of collagen alpha 1 (I) and matrix metalloproteinase 2 gene expression. Halofuginone also suppresses extracellular matrix deposition and fibroblast proliferation. It was recently shown to be effective in suppression of bladder carcinoma and glioma. This study sought to evaluate the effect of treatment with halofuginone on growth of hepatocellular carcinoma (HCC) in mice. Athymic Balb/c mice were injected subcutaneously with 10(7) human hepatoma cells (Hep3B), followed by treatment with halofuginone administered in the diet (750 microg/kg) starting on day 3, before tumour innoculation. The control group was received a normal diet. Mice were followed for survival, tumour volume and serum alpha-fetoprotein (alpha FP). The mechanism of the anti-tumour effect of halofuginone was determined in vitro by assessing tumour cell growth, and by measuring the serum concentrations of interferon-gamma (IFN gamma) and interleukin 2 (IL2). Halofuginone treatment induced almost complete tumour suppression in treated mice. Mortality rates were 10% and 50%, in halofuginone-treated and control mice, respectively (P<0.001). No visible tumour was observed in treated mice, as compared with a 364 mm3 tumour in control mice. Serum alpha FP were 0.1 and 212 ng/ml in treated and control mice, respectively (P<0.005). Halofuginone significantly inhibited HCC proliferation in vitro. Maximal inhibition of 64% of tumour cell growth was observed at a concentration of 10(-8) M. The anti-tumour effect was mediated via a significant increase in IFN gamma and IL2 (90 vs. 35, and 210 vs. 34 pg/ml in treated and control groups, respectively, P<0.005). Treatment with halofuginone effectively suppressed the progression of HCC in mice. This effect may be associated with a direct anti-tumour effect, and/or enhancement of a systemic immune response.

Animals↗
PubMed2001

Heparanase expression in primary and metastatic pancreatic cancer.

The human endoglycosidase heparanase (hpa) degrades heparan-sulfate proteoglycans, which constitute prominent components of basement membranes and extracellular matrix. Due to the critical function of hpa in cancer cell invasion and metastasis, we have analyzed the expression of hpa in human primary and metastatic pancreatic cancer as well as in the normal pancreas and in chronic pancreatic inflammation. By real-time quantitative PCR, there was a 7.9- and 30.2-fold increase of hpa mRNA in chronic pancreatitis and pancreatic cancer tissue samples, respectively, in comparison with normal pancreatic tissues. There was a significant correlation between enhanced hpa mRNA expression and shorter postoperative patient survival. hpa mRNA and protein localized in the cancer cells of primary and metastatic pancreatic cancer, with a preferentially higher expression at the primary tumor site. Cultured pancreatic cancer cells transfected with a full-length hpa construct displayed enhanced invasiveness in an invasion chamber assay. These results suggest that hpa overexpression in human pancreatic cancers facilitates cancer cell invasion, thereby enhancing the metastatic potential of the tumors.

Adult↗
PubMed2001

Expression pattern and secretion of human and chicken heparanase are determined by their signal peptide sequence.

Cleavage of heparan sulfate (HS) proteoglycans affects the integrity and function of tissues and thereby fundamental phenomena, involving cell migration and response to changes in the extracellular microenvironment. The role of HS-degrading enzymes, commonly referred to as heparanases, in normal development has not been identified. The present study focuses on cloning, expression, and properties of a chicken heparanase and its distribution in the developing chicken embryo. We have identified a chicken EST, homologous to the recently cloned human heparanase, to clone and express a functional chicken heparanase, 60% homologous to the human enzyme. The full-length chicken heparanase cDNA encodes a 60-kDa proenzyme that is processed at the N terminus into a 45-kDa highly active enzyme. The most prominent difference between the chicken and human enzymes resides in the predicted signal peptide sequence, apparently accounting for the chicken heparanase being readily secreted and localized in close proximity to the cell surface. In contrast, the human enzyme is mostly intracellular, localized in perinuclear granules. Cells transfected with a chimeric construct composed of the chicken signal peptide preceding the human heparanase exhibited cell surface localization and secretion of heparanase, similar to cells transfected with the full-length chicken enzyme. We examined the distribution pattern of the heparanase enzyme in the developing chicken embryo. Both the chicken heparanase mRNA and protein were expressed, as early as 12 h post fertilization, in cells migrating from the epiblast and forming the hypoblast layer. Later on (72 h), the enzyme is preferentially expressed in cells of the developing vascular and nervous systems. Cloning and characterization of heparanase, the first and single functional vertebrate HS-degrading enzyme, may lead to identification of other glycosaminoglycan degrading enzymes, toward elucidation of their significance in normal and pathological processes.

Amino Acid Sequence↗
PubMed2001

Effects of the heparin-mimicking compound RG-13577 on lipoprotein lipase and on lipase mediated binding of LDL to cells.

Lipoprotein lipase (LPL) has high affinity for heparin and heparin-like compounds. In vivo the enzyme is attached to heparan sulfate proteoglycans on the endothelium of capillaries and larger blood vessels. The enzyme is released from these sites after intravenous injection of heparin. One has here investigated the effects of RG-13577 on LPL, both after intravenous injection to rats and under cell culture conditions. RG-13577 is a heparin-mimicking compound known to prevent angiogenesis by interference with binding of growth factors to cells. It has therefore been considered for use in cancer therapy as well as for prevention of atherosclerosis and restenosis. It was found that intravenously injected RG-13577 released both LPL and hepatic lipase (HL) to the blood. Binding of LPL in extrahepatic tissues was prevented and clearance of radiolabeled LPL from the circulation was delayed. Furthermore, RG-13577 released LPL from extracellular matrix (ECM) produced by endothelial cells and from THP-1 monocyte-derived macrophages. Lipase-mediated binding and uptake of human LDL in these cells was also prevented by RG-13577. Thus, in the test systems RG-13577 had the same effects as heparin, but on a molar basis RG-13577 was in all cases less effective.

Animals↗
PubMed2001

Molecular properties and involvement of heparanase in cancer progression and normal development.

Heparan sulfate proteoglycans (HSPGs) play a key role in the self-assembly, insolubility and barrier properties of basement membranes and extracellular matrices. Hence, cleavage of heparan sulfate (HS) affects the integrity and functional state of tissues and thereby fundamental normal and pathological phenomena involving cell migration and response to changes in the extracellular microenvironment. Here, we describe the molecular properties, expression and function of a human heparanase, degrading HS at specific intrachain sites. The enzyme is synthesized as a latent approximately 65 kDa protein that is processed at the N-terminus into a highly active approximately 50 kDa form. The heparanase mRNA and protein are preferentially expressed in metastatic cell lines and human tumor tissues. Overexpression of the heparanase cDNA in low-metastatic tumor cells conferred a high metastatic potential in experimental animals, resulting in an increased rate of mortality. The heparanase enzyme also releases ECM-resident angiogenic factors in vitro and its overexpression induces an angiogenic response in vivo. Heparanase may thus facilitate both tumor cell invasion and neovascularization, both critical steps in cancer progression. The enzyme is also involved in cell migration associated with inflammation and autoimmunity. The unexpected identification of a single predominant functional heparanase suggests that the enzyme is a promising target for drug development. In fact, treatment with heparanase inhibitors markedly reduces tumor growth, metastasis and autoimmune disorders in animal models. Studies are underway to elucidate the involvement of heparanase in normal processes such as implantation, embryonic development, morphogenesis, tissue repair, inflammation and HSPG turnover. Heparanase is the first functional mammalian HS-degrading enzyme that has been cloned, expressed and characterized. This may lead to identification and cloning of other glycosaminoglycan degrading enzymes, toward a better understanding of their involvement and significance in normal and pathological processes.

Animals↗
PubMed2001

Molecular properties and involvement of heparanase in cancer progression and mammary gland morphogenesis.

Tumor spread involves degradation of various components of the extracellular matrix and blood vessel wall. Among these is heparan sulfate proteoglycan, which plays a key role in the self-assembly, insolubility and barrier properties of basement membranes and extracellular matrices. Expression of an endoglycosidase (heparanase) which degrades heparan sulfate correlates with the metastatic potential of tumor cells, and treatment with heparanase inhibitors markedly reduces the incidence of metastasis in experimental animals. Heparin-binding angiogenic proteins are stored as a complex with heparan sulfate in the microenvironment of tumors. These proteins are released and can induce new capillary growth when heparan sulfate is degraded by heparanase. Here, we describe the molecular properties, expression and involvement in tumor progression of a human heparanase. The enzyme is synthesized as a latent approximately 65 kDa protein that is processed at the N-terminus into a highly active approximately 50 kDa form. The heparanase mRNA and protein are preferentially expressed in metastatic human cell lines and in tumor biopsy specimens, including breast carcinoma. Overexpression of the heparanase cDNA in low-metastatic tumor cells conferred a high metastatic potential in experimental animals, resulting in an increased rate of mortality. The heparanase enzyme also released ECM-resident bFGF in vitro, and its overexpression elicited an angiogenic response in vivo. Heparanase may thus facilitate both tumor cell invasion and neovascularization, two critical steps in tumor progression. Mammary glands of transgenic mice overexpressing the heparanase enzyme exhibit precocious branching of ducts and alveolar development, suggesting that the enzyme promotes normal morphogenesis and possibly pre-malignant changes in the mammary gland.

Breast↗
PubMed2001

Expression of heparanase, Mdm2, and erbB2 in ovarian cancer.

Ovarian cancer is the most lethal of gynecological malignancies. Yet early diagnosis and prognosis are far from being satisfactory. Degradation of heparan sulfate proteoglycans by heparanase appears to play an important role in the invasiveness of tumor cells through the basement membrane and into the extracellular matrix. Recent cloning of the heparanase gene and generation of monoclonal antibodies against the enzyme permit to examine tumor cell expression of the enzyme. The aim of the present study was to assess heparanase activity and localization in various subtypes of epithelial ovarian cancer in correlation with oncogene expression. Histologically confirmed malignant ovarian tissue from ten women and tissue from 2 benign ovarian tumors and 4 normal ovaries were assessed for heparanase presence, activity and localization, incidence of apoptosis and expression of the oncogenes erbB2 and Mdm2. Heparanase immunohistostaining and activity were present in mucinous carcinomas and were more intense than in endometrioid and in serous carcinomas. The lowest activity was observed in benign ovarian tumors and normal ovaries. In ovarian carcinomas the enzyme was intensely concentrated in the cytoplasm of the cancerous cells. In contrast, in normal ovaries and benign tumors the enzyme was predominantly localized in endothelial cells lining blood capillaries. The rate of apoptosis was considerably higher in mucinous and endometrioid carcinomas, and was lower in serous and primary peritoneal carcinomas. Extremely high concentration of heparanase was often demonstrated in apoptotic cells. Endometrioid and serous carcinomas showed high expression of Mdm2 and erbB2 while mucinous carcinomas showed low expression. In benign ovarian tumors and normal ovaries the expression of both oncoproteins was extremely low. In conclusion ovarian carcinomas demonstrate higher levels of heparanase than benign tumors and normal ovaries suggesting that the enzyme may play an important role in metastatic spread of the cancerous cells. Apoptosis may be a significant part of the mechanism of the enzyme release into the extracellular space. Although heparanase activity seems to play an essential role in tumor progression, expression of oncogenes, such as erbB2 and Mdm2 seems to play the dominant role in the development of ovarian cancer.

Adenocarcinoma, Mucinous↗
PubMed2001

A synthetic heparin-mimicking polyanionic compound binds to the LDL receptor-related protein and inhibits vascular smooth muscle cell proliferation.

A synthetic heparin-mimicking polyaromatic anionic compound RG-13577 (polymer of 4-hydroxyphenoxy acetic acid and formaldehyde ammonium salt, Mr approximately 5800) exhibits specific binding to vascular smooth muscle cells (SMCs) and inhibits their proliferative response to growth promoting factors. Receptor binding of (14)C-RG-13577 was efficiently competed by apolipoprotein E3 (apoE), lactoferrin, and the LRP (LDL receptor-related protein) receptor associated 39 kDa protein (RAP). Unlike cell surface binding of apoE, binding of RG-13577 to SMCs was not affected by heparin, heparan sulfate degrading enzymes, or low density lipoprotein (LDL). Moreover, wild-type and heparan sulfate-deficient Chinese hamster ovary (CHO) cells, as well as normal- and LDL receptor negative- human skin fibroblasts bind RG-13577, but not apoE, to a similar extent. On the other hand, homozygous mouse embryonic fibroblasts deficient in the LDL receptor-related protein (LRP) expressed a markedly reduced binding of RG-13577 as compared to normal mouse embryonic fibroblasts. These results indicate that RG-13577 and related compounds bind to the LRP receptor on the surface of vascular SMCs. Addition of lactoferrin to cultured SMCs protected the cells against the antiproliferative effect of compound RG-13577, suggesting that this inhibition is mediated by RG-13577 binding to LRP receptors on the SMC surface. Altogether, we have identified a series of synthetic polyaromatic anionic molecules that exhibit specific binding to LRP and thereby exert an antiproliferative effect on vascular SMCs. These compounds are applied to suppress SMC proliferation associated with restenosis and accelerated atherosclerosis.

Animals↗
PubMed2001

Properties and function of heparanase in cancer metastasis and angiogenesis.

Cleavage of heparan sulfate proteoglycans affects the integrity and functional state of tissues and thereby fundamental normal and pathological phenomena involving cell migration and response to changes in the extracellular microenvironment. Heparanase, degrading heparan sulfate (HS) at specific intrachain sites, is synthesized as a latent approximately 65 kDa protein that is processed at the N-terminus into a highly active approximately 50 kDa form. The heparanase enzyme is preferentially expressed in human tumors and its overexpression in low-metastatic tumor cells confers a highly invasive phenotype in experimental animals. Heparanase also releases angiogenic factors and accessory fragments of HS from the tumor microenvironment and induces an angiogenic response in vivo. These effects were best demonstrated when the enzyme was secreted and/or expressed on the cell surface. Heparanase may thus facilitate tumor cell invasion, vascularization and survival, all critical events in cancer progression. These observations, the anti-cancerous effect of heparanase-inhibiting molecules, and the unexpected identification of a single predominant functional heparanase suggest that the enzyme is a promising target for drug development.

Glucuronidase↗