Expression of heparanase by platelets and circulating cells of the immune system: possible involvement in diapedesis and extravasation.

Interaction of T and B lymphocytes, platelets, granulocytes, macrophages and mast cells with the subendothelial extracellular matrix (ECM) is associated with degradation of heparan sulfate (HS) by a specific endoglycosidase (heparanase) activity. The enzyme is released from intracellular compartments (i.e., lysosomes, specific granules) in response to various activation signals (i.e., thrombin, calcium ionophore, immune complexes, antigens, mitogens), suggesting its regulated involvement in inflammation and cellular immunity. In contrast, various tumor cells appear to express and secrete heparanase in a constitutive manner, in correlation with their metastatic potential. Heparanase enzymes produced by different cell types may exhibit different molecular properties and substrate cleavage specificities. The platelet enzyme appears also in a latent form. It can be activated by tumor cells and thereby facilitate their extravasation in the process of metastasis. Degradation of ECM-HS by all cell types was facilitated by a proteolytic activity residing in the ECM and/or expressed by the invading cells. This proteolytic activity produced a more accessible substrate for the heparanase enzymes. Heparanase-inhibiting, nonanticoagulant species of heparin markedly reduced the incidence of lung metastasis in experimental animals. These species of heparin also significantly impaired the traffic of T lymphocytes and suppressed cellular immune reactivity and experimental autoimmune diseases. Heparanase activity expressed by intact cells (i.e., platelets, mast cells, neutrophils, lymphoma cells) was found to release active HS-bound basic fibroblast growth factor from ECM and basement membranes. Heparanase may thus elicit an indirect neovascular response in processes such as wound repair, inflammation and tumor development. The significant anticancerous effect of heparanase-inhibiting molecules may therefore be attributed to their potential inhibition of both tumor invasion and angiogenesis. Both normal leukocytic cells and metastatic tumor cells can enter the bloodstream, travel to distant sites and extravasate to the parenchyma at these sites. We suggest that heparanase is utilized for this purpose by both types of cells. Other functions (i.e., enzyme activities, adhesive interactions, chemotactic and proliferative responses) of metastatic tumor cells seem to mimic the equivalent functions of leukocytes as they migrate across blood vessels to gain access to sites of inflammation.     

Heparanase induces vascular endothelial growth factor expression: correlation with p38 phosphorylation levels and Src activation

Heparanase is an endo-beta-D-glucuronidase involved in cleavage of heparan sulfate moieties and hence participates in extracellular matrix (ECM) degradation and remodeling. Traditionally, heparanase activity was correlated with the metastatic potential of a variety of tumor-derived cell types. Cloning of the heparanase gene indicated that heparanase expression is up-regulated in a variety of primary human tumors. In some cases, heparanase up-regulation correlated with increased tumor vascularity, an angiogenic feature that could be recapitulated in a number of in vitro and in vivo models. The mechanism by which heparanase enhances angiogenic responses is not entirely clear but is thought to be mediated primarily by release of ECM-resident angiogenic growth factors such as basic fibroblast growth factor and vascular endothelial growth factor (VEGF). Here, we examined the possibility that heparanase directly participates in VEGF gene regulation. We provide evidence that heparanase overexpression in human embryonic kidney 293, MDA-MB-435 human breast carcinoma, and rat C6 glioma cells resulted in a 3- to 6-fold increase in VEGF protein and mRNA levels, which correlated with elevation of p38 phosphorylation. Moreover, heparanase down-regulation in B16 mouse melanoma cells by a specific siRNA vector was accompanied by a decrease in VEGF and p38 phosphorylation levels, suggesting that VEGF gene expression is regulated by endogenous heparanase. Interestingly, a specific p38 inhibitor did not attenuate VEGF up-regulation by heparanase whereas Src inhibitors completely abrogated this effect. These results indicate, for the first time, that heparanase is actively involved in the regulation of VEGF gene expression, mediated by activation of Src family members.     

Differentiating human leukemia cells express heparanase that degrades heparan sulfate in subendothelial extracellular matrix

Human promyelocytic (HL-60) and monoblast-like (U-937) leukemia cell lines were tested for expression of an endoglycosidase (heparanase) capable of degrading heparan sulfate (HS) side chains in the subendothelial extracellular matrix (ECM). Heparanase activity has been previously shown to be expressed by activated lymphocytes and macrophages and by highly metastatic tumor cells, in correlation with their ability to invade blood vessels and extracellular matrices. Incubation of HL-60 and U-937 cells with sulfate-labeled ECM in the presence of 12-O-tetradecanoyl-phorbol-13-acetate (TPA) resulted in heparanase-mediated release of heparan sulfate degradation products. This degradation was inhibited by heparin, stimulated by plasminogen and not expressed by cells treated with retinoic acid or dimethylsulfoxide and undergoing neutrophilic differentiation. Heparanase activity was not detected in media conditioned by HL-60 and U-937 cells but was found in their cell lysates, regardless of whether or not the cells were exposed to TPA. These findings imply that TPA-induced differentiation of human myeloid leukemic cells to macrophage-like cells, but not to neutrophilic granulocytes, is associated with expression on the cell surface of a preformed heparanase activity. The enzyme may serve as a marker for human cell differentiation into macrophages, allowing the differentiating cells to traverse the vascular compartment and reach their target sites.     

Heparanase affects adhesive and tumorigenic potential of human glioma cells

Heparanase is an endo-beta-glucuronidase responsible for the cleavage of heparan sulfate, participating in extracellular matrix degradation and remodeling. Traditionally, heparanase activity was well correlated with the metastatic potential of a large number of tumor-derived cell types. More recently, heparanase up-regulation was detected in essentially all human tumors examined, correlating, in some cases, with poor postoperative survival and increased tumor vascularity. The role of heparanase in primary tumor progression is, however, poorly understood. Here, we overexpressed the human heparanase gene in a human glioma cell line, U87. We found that heparanase overexpression induces cell invasion, as might be expected. Surprisingly, elevated heparanase expression levels correlated with decreased proliferation rates and increased cell spreading and formation of a tight monolayer rather than large cell aggregates. This phenotypic appearance was accompanied by beta1-integrin activation, FAK and Akt phosphorylation, and Rac activation. In a xenograft tumor model, relatively moderate heparanase expression levels significantly enhanced tumor development and tumor vascularity, whereas high heparanase expression levels inhibited tumor growth. These results indicate that heparanase activates signal transduction pathways and, depending on its expression levels, may modulate tumor progression.     

Increased chemotactic migration and growth in heparanase-overexpressing human U251n glioma cells

Heparanase is an endoglycosidase that degrades heparan sulfate, the main polysaccharide constituent of the extracellular matrix (ECM) and basement membrane. Expression of the heparanase gene is associated with the invasion and metastatic potential of a variety of tumor-derived cell types. However, the roles of heparanase in the regulation of gene expression and the subsequent cell function changes other than invasion are not clear. In the current study, we overexpressed the human heparanase gene in a human U251n glioma cell line. We found that heparanase-overexpression significantly increased cell invasion, proliferation, anchorage-independent colony formation and chemotactic migration towards fetal bovine serum (FBS)-supplied medium and stromal cell-derived factor-1 (SDF-1). These phenotypic appearances were accompanied by enhanced protein kinase B (AKT) phosphorylation. Focal adhesion kinase (FAK) and extracellular signal-regulated kinase 1 (ERK1) signaling were not altered by heparanase-overexpression. These results indicate that heparanase has pleiotropic effects on tumor cells.     

乙酰肝素酶的外源性表达对大肠癌HT29细胞侵袭性的影响

背景与目的:乙酰肝素酶(heparanase,Hpa)基因表达与恶性肿瘤及肿瘤细胞的侵袭、转移和血管生成能力密切相关。本研究旨在通过增强肿瘤细胞中外源性Hpa基因的表达,探讨该基因对大肠癌细胞HT29转移侵袭能力的影响。方法:Hpa全长基因真核表达载体转染HT29细胞,MTT法检测转化细胞增殖能力,Boyden小室体外侵袭实验比较转染前后细胞侵袭能力的变化,通过转化细胞裸鼠异种接种成瘤和实体瘤回盲部原位种植转移模型建立,观察Hpa基因外源性表达对HT29细胞侵袭性的影响。结果:转染Hpa基因细胞HT29-Hpa较未转染细胞HT29和转染空载细胞HT29-KZ生长速度明显加快;Boyden小室体外侵袭实验显示,HT29-Hpa细胞穿膜数(45.5±0.5)较HT29细胞(29.3±0.1)和HT29-KZ细胞(30.1±0.2)增多,差异具有显著性(P<0.01)。转染细胞裸鼠皮下瘤生长速度明显加快,同期内HT29-Hpa细胞形成的皮下瘤(12mm×9mm×10mm)较HT29细胞皮下瘤(6mm×8mm×6mm)大,HT29-Hpa细胞皮下瘤回盲部原位种植致肝转移率(71.43%)较HT29细胞肝转移率(14.29%)增高,两者间有显著性差异(P<0.01)。结论:Hpa基因外源性的表达能促进肿瘤细胞的生长、侵袭和转移。     

Inhibition of heparanase activity and heparanase-induced angiogenesis by suramin analogues

Heparanase, a heparan sulfate-specific endo-beta-D-glucuronidase, plays an important role in tumor cell metastasis through the degradation of extracellular matrix heparan sulfate proteoglycans (ECM HSPG). Heparanase activity correlates with the metastatic propensity of tumor cells. Suramin, a polysulfonated naphthylurea, is an inhibitor of heparanase with suramin analogues shown to possess antiangiogenic and antiproliferative properties. We investigated the effects of selected suramin analogues (NF 127, NF 145 and NF 171) on heparanase activity and heparanase-driven angiogenesis. Studies of the ability of cellular extracts and purified heparanase from human, highly invasive and brain-metastatic melanoma (70W) cells revealed that heparanase expressed by these cells was effectively inhibited by suramin analogues in a dose-dependent manner. These analogues possessed more potent heparanase inhibitory activities than suramin: The concentrations required for 50% heparanase inhibition (IC(50)) were 20-30 microM, or at least 2 times lower than that for suramin. One hundred percent inhibition was observed at concentrations of 100 microM and higher. Of relevance, these compounds significantly decreased (i) the invasive capacity of human 70W cells by chemoinvasion assays performed with filters coated with purified HSPG or Matrigel trade mark, and (ii) blood vessel formation by in vivo angiogenic assays, thus linking their antiangiogenic properties with impedance of heparanase-induced angiogenesis. Specifically, inhibition of invasion by NF 127, NF 145 and NF 171 was found at 10 microM concentrations of compounds with a significant decrease of invasive values at concentrations as low as 1.5 microM. In addition, NF 127, NF 145 and NF 171 promoted nearly complete inhibition of heparanase-induced angiogenesis at values ranging from 236 microM (for NF 145) to 362 microM (for NF 127). These results further emphasize the importance of heparanase in invasive and angiogenic mechanisms and the potential clinical application of heparanase inhibitors such as suramin analogues in cancers and angiogenesis-dependent diseases.     

Heparanase induces VEGF C and facilitates tumor lymphangiogenesis

Heparanase is an endoglycosidase that specifically cleaves heparan sulfate side chains, a class of glycosaminoglycans abundantly present in the extracellular matrix and on the cell surface. Heparanase activity is strongly implicated in tumor angiogenesis and metastasis attributed to remodeling of the subepithelial and subendothelial basement membranes. We hypothesized that similar to its proangiogenic capacity, heparanase is also engaged in lymphangiogenesis and utilized the D2-40 monoclonal antibody to study lymphangiogenesis in tumor specimens obtained from 65 head and neck carcinoma patients. Lymphatic density was analyzed for association with clinical parameters and heparanase staining. We provide evidence that lymphatic vessel density (LVD) correlates with head and neck lymph node metastasis (N-stage, p = 0.007) and inversely correlates with tumor cell differentiation (p = 0.007). Notably, heparanase staining correlated with LVD (p = 0.04) and, moreover, with VEGF C levels (p = 0.01). We further demonstrate that heparanase overexpression by epidermoid, breast, melanoma and prostate carcinoma cells induces a 3- to 5-fold elevation in VEGF C expression in vitro and facilitates tumor xenograft lymphangiogenesis in vivo, whereas heparanase gene silencing was associated with decreased VEGF C levels. These findings suggest that heparanase plays a unique dual role in tumor metastasis, facilitating tumor cell invasiveness and inducing VEGF C expression, thereby increasing the density of lymphatic vessels that mobilize metastatic cells.     

乙酰肝素酶在乳腺癌侵袭转移中的作用及调控机制*

乙酰肝素酶（Heparanase ,HPSE）是目前发现的哺乳动物细胞中唯一能降解细胞外基质和基底膜中硫酸肝素蛋白多糖侧链—硫酸乙酰肝素的内源性糖苷酶,是目前抗肿瘤转移的理想靶点。HPSE在乳腺癌中常有高表达,并与肿瘤大小和淋巴结转移等密切相关。体外研究表明,乳腺癌细胞中HPSE启动子活性增高,转染HPSE的乳腺癌细胞在体内成瘤后,其肿瘤体积、重量、微血管密度以及癌细胞存活时间均明显高于阴性对照组。应用反义核酸技术或RNA干扰技术封闭或沉默HPSE基因表达后,乳腺癌细胞黏附和侵袭能力显著降低,表明HPSE在乳腺癌侵袭转移中发挥极其重要的作用。HPSE在乳腺癌侵袭转移中受多种机制调控,主要有:雌激素与其受体结合后作用于HPSE基因特定区域,从而提高HPSE转录活性,增强其基因和蛋白的表达;HPSE可使破骨细胞刺激因子产生增加,从而导致骨质溶解破坏,为乳腺癌骨转移奠定基础;HPSE诱导循环淋巴细胞产生刺激因子,从而促进乳腺癌的侵袭转移。此外,HPSE基因还受p53基因、ETS 基因、EGR 1 基因、PI-88因子、COX-2 等的调控。本文就HPSE在乳腺癌中的表达状况、在侵袭转移中的作用及调控机制进行综述。      

Brain metastases in melanoma: roles of neurotrophins

Brain metastasis, which occurs in 20% to 40% of all cancer patients, is an important cause of neoplastic morbidity and mortality. Successful invasion into the brain by tumor cells must include attachment to microvessel endothelial cells, penetration through the blood-brain barrier, and, of relevance, a response to brain survival and growth factors. Neurotrophins (NTs) are important in brain-invasive steps. Human melanoma cell lines express low-affinity NT receptor p75NTR in relation to their brain-metastatic propensity with their invasive properties being regulated by NGF, or nerve growth factor, the prototypic NT. They also express functional TrkC, the putative receptor for the invasion-promoting NT-3. In brain-metastatic melanoma cells, NTs promote invasion by enhancing the production of extracellular matrix (ECM)-degradative enzymes such as heparanase, an enzyme capable of locally destroying both ECM and the basement membrane of the blood-brain barrier. Heparanase is an endo-beta-d-glucuronidase that cleaves heparan sulfate (HS) chains of ECM HS proteoglycans, and it is a unique metastatic determinant because it is the dominant mammalian HS degradative enzyme. Brain-metastatic melanoma cells also produce autocrine/paracrine factors that influence their growth, invasion, and survival in the brain. Synthesis of these factors may serve to regulate NT production by brain cells adjacent to the neoplastic invasion front, such as astrocytes. Increased NT levels have been observed in tumor-adjacent tissues at the invasion front of human brain melanoma. Additionally, astrocytes may contribute to the brain-metastatic specificity of melanoma cells by producing NT-regulated heparanase. Trophic, autocrine, and paracrine growth factors may therefore determine whether metastatic cells can successfully invade, colonize, and grow in the CNS.     

Maintenance on extracellular matrix and expression of heparanase activity by human ovarian carcinoma cells from biopsy specimens

A routine procedure has been developed for the isolation and maintenance in culture of human ovarian carcinoma cells derived from biopsy specimens. Cell attachment, plating efficiency and initial outgrowth were greatly improved by seeding the cells on a basement-membrane-like extracellular matrix (ECM) deposited by cultured corneal endothelial cells. These effects were most significant in serum-free conditions which markedly reduced the rate of cell attachment and growth on regular tissue culture plastic. In 60-80% of the cases and regardless of the patient's age, cells cultured on ECM in the absence of serum divided actively and formed a tightly packed epithelial cell monolayer. Fibroblast overgrowth and cell detachment often occurred on ECM in the presence of serum. Incubation of the human ovarian carcinoma cells with sulfate-labelled ECM, resulted in the release of heparan sulfate degradation fragments, 4- to 7-fold smaller than intact heparan sulfate side chains. This degradation was brought about by endoglycosidase (heparanase) activity expressed to a higher extent by cells that were first maintained in primary cultures as compared with cell aggregates taken directly from the biopsy specimen. In most cases, cells derived from metastatic tumors expressed a higher heparanase activity than cells from the primary ovarian tumor. This result corroborates previous studies, performed with cell lines, on the possible involvement of heparanase in tumor cell invasion and metastasis.     

Expression of heparanase in renal cell carcinomas: implications for tumor invasion and prognosis

PURPOSE: Heparanase activity has been detected in many malignant tumors, showing a correlation with the metastatic potential. The present study was undertaken to investigate the expression of heparanase and its prognostic significance in renal cell carcinomas (RCC). EXPERIMENTAL DESIGN: Nineteen RCCs and 6 nonneoplastic renal tissues were analyzed for heparanase mRNA expression by real-time PCR. Heparanase protein expression was semiquantitatively investigated by immunohistochemistry in 70 RCCs. Involvement of heparanase in the invasiveness of RCC cell lines, 786-O and Caki-2 cells, was examined by down-regulating the gene expression with small interfering RNA (siRNA) using the Matrigel invasion assay. RESULTS: The expression level of heparanase mRNA was significantly higher in clear cell RCCs than in papillary RCCs, chromophobe RCCs, and nonneoplastic renal tissues. Heparanase was predominantly immunolocalized to cell surface and cytoplasm of clear cell RCCs and mean expression levels of heparanase were significantly higher in clear cell RCCs than in papillary and chromophobe RCCs. The protein expression levels were positively correlated with primary tumor stage, distant metastasis, and histologic grade. Targeting of heparanase mRNA expression in 786-O and Caki-2 cells with siRNA down-regulated the mRNA expression and inhibited the Matrigel invasion by these cells, whereas nonsilencing siRNA showed no effect. Multivariate Cox analysis revealed that elevated heparanase expression was a significant and an independent predictor of disease-specific survival (odds ratio, 8.814; P = 0.019). CONCLUSIONS: These data suggest that heparanase plays an important role in invasion and metastasis and silencing of the gene might be a potential therapeutic target in clear cell RCCs.     

反义寡核苷酸沉默乙酰肝素酶对食管鳞癌细胞株TE-13侵袭能力的影响

背景与目的:乙酰肝素酶(heparanase,Hpa)为降解硫酸乙酰肝素多糖的内糖苷酶,在多种恶性肿瘤的侵袭转移中发挥重要作用。本研究旨在探讨Hpa在食管鳞癌细胞株TE-13中的表达和转染Hpa反义寡核苷酸(antisenseoligodeoxynucleotide,ASODN)对TE-13细胞的影响。方法:脂质体法转染人工合成的HpaASODN片段,应用RT-PCR、Westernblot和免疫细胞化学方法检测转染前后Hpa基因和蛋白表达的变化,Matrigel侵袭实验观察转染ASODN后TE-13细胞侵袭行为的改变。结果:在TE-13细胞中,RT-PCR扩增得到大小为585bp的Hpa基因条带,Westernblot检测到50ku大小的Hpa蛋白,免疫细胞化学染色表明Hpa主要定位于胞浆和胞膜。转染不同浓度HpaASODN后,RT-PCR、Westernblot和细胞免疫染色均证实TE-13细胞Hpa基因和蛋白表达下调,且随HpaASODN的浓度增高,基因和蛋白表达量逐渐降低(P<0.05),不同浓度HpaASODN组间有显著性差异(P<0.05)。Matrigel侵袭实验中,转染不同浓度HpaASODN后,侵袭至下室面的TE-13细胞数均下降(P<0.05)。随HpaASODN浓度的增高,侵袭至下室面的TE-13细胞个数逐渐减少(P<0.05),不同浓度HpaASODN组间有显著性差异(P<0.05)。结论:TE-13细胞存在Hpa基因的表达。HpaASODN能显著降低Hpa基因表达量,并且使TE-13细胞侵袭力明显下降。     

Heparanase Levels Are Elevated in the Plasma of Pediatric Cancer Patients and Correlate with Response to Anticancer Treatment

Heparanase is an endoglycosidase that specifically cleaves heparan sulfate (HS) side chains of heparan sulfate proteoglycans, the major proteoglycan in the extracellular matrix (ECM) and cell surfaces. Heparanase upregulation was documented in an increasing number of primary human tumors, correlating with reduced postoperative survival rate and enhanced tumor angiogenesis. The purpose of the current study was to determine heparanase levels in blood samples collected from pediatric cancer patients using an ELISA method. Heparanase levels were elevated four-fold in the plasma of cancer patients compared with healthy controls (664 ± 143 vs 163 ± 18 pg/ml, respectively). Evaluating plasma samples following anticancer therapy revealed reduced heparanase levels (664 ± 143 vs 429 ± 82 pg/ml), differences that are statistically highly significant (P = .0048). Of the 55 patients with complete remission (CR) or very good partial remission (VGPR) at restaging, 41 (74.5%) had lower heparanase amounts, whereas 14 patients (25.5%) had similar or higher amounts of plasma heparanase. All nine patients with stable or advancing disease had similar or elevated levels of heparanase on restaging. The results show that heparanase levels are elevated in the plasma of pediatric cancer patients and closely correlate with treatment responsiveness, indicating that heparanase levels can be used to diagnose and monitor patient''s response to anticancer treatment.     

Tumorigenic and adhesive properties of heparanase

Heparanase is an endo-β-glucuronidase that cleaves heparan sulfate side chains presumably at sites of low sulfation, activity that is strongly implicated with cell invasion associated with cancer metastasis, a consequence of structural modification that loosens the extracellular matrix barrier. In addition, heparanase exerts pro-adhesive properties, mediated by clustering of membrane heparan sulfate proteoglycans (i.e., syndecans) and activation of signaling molecules such as Akt, Src, EGFR, and Rac in a heparan sulfate-dependent and -independent manner. Activation of signaling cascades by enzymatically inactive heparanase and by a peptide corresponding to its substrate binding domain not only increases cell adhesion but also facilitates cancer cell growth. This notion is supported by preclinical and clinical settings, encouraging the development of anti-heparanase therapeutics. Here, we summarize recent progress in heparanase research emphasizing the molecular mechanisms that govern its pro-tumorigenic and pro-adhesive properties. Pro-adhesive properties of the heparanase homolog, heparanase 2 (Hpa2), are also discussed. Enzymatic activity-independent function of proteases (i.e., matrix metalloproteinases) is discussed in the context of cell adhesion and tumor progression. Collectively, these examples suggest that enzyme function exceeds beyond the enzymatic aspect, thus significantly expanding the scope of the functional proteome. Cross-talk with matrix metalloproteinases and the role of heparanase in pathological settings other than cancer are also described.     

Urokinase induces receptor mediated brain tumor cell migration and invasion

The plasminogen activation (PA) system plays an important role in tumor invasion by initiating pericellular proteolysis of the extracellular matrix (ECM) and inducing cell migration. Malignant brain tumors overexpress PA members and characteristically invade by migrating on ECM-producing white matter tracts and blood vessel walls. To determine whether urokinase-type plasminogen activator (uPA) and its receptor (uPAR) directly modulate the migration of brain tumor cells, we examined six human brain tumor cell lines, 2 astrocytomas (SW1088, SW1783), 2 medullobastomas (Daoy, D341Med), and 2 glioblastomas (U87MG, U118MG), for their surface uPAR expression, endogenous PA activity, and functional proteolytic activity by an ECM-degradation assay. Migration on Transwell membranes and invasion of Matrigel was then tested by pre-incubating the cells with increasing concentrations of either uPA, the proteolytically inactive amino-terminal fragment (ATF) of uPA, or the uPAR cleaving enzyme, phosphatidylinositol-specific phospholipase C (PI-PLC).All of the cell lines, except D341Med, express surface uPAR protein and uPA activity. High levels of uPAR and uPA activity correlated with cellular degradation of ECM, cell migration, and Matrigel invasion. Cell migration and invasion were enhanced by uPA or ATF in a dose dependent manner, while PI-PLC treatment abolished the uPA effect and inhibited migration and invasion. We conclude that ligation of uPAR by uPA directly induces brain tumor cell migration, independent of uPA-mediated proteolysis; and in concert with ECM degradation, markedly enhances invasion. Conversely, removing membrane bound uPAR from the surface of the cells studied inhibited their ability to migrate and invade even in the presence of proteolytically active uPA.