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Background: Mammalian cells express a single functional heparanase, an endoglycosidase that cleaves heparan sulfate and thereby promotes tumor metastasis, angiogenesis, and inflammation. Malignant mesothelioma is highly aggressive and has a poor prognosis because of the lack of markers for early diagnosis and resistance to conventional therapies. The purpose of this study was to elucidate the mode of action and biological significance of heparanase in mesothelioma and test the efficacy of heparanase inhibitors in the treatment of this malignancy.Methods: The involvement of heparanase in mesothelioma was investigated by applying mouse models of mesothelioma and testing the effect of heparanase gene silencing (n = 18 mice per experiment; two different models) and heparanase inhibitors (ie, PG545, defibrotide; n = 18 per experiment; six different models). Synchronous pleural effusion and plasma samples from patients with mesothelioma (n = 35), other malignancies (12 non-small cell lung cancer, two small cell lung carcinoma, four breast cancer, three gastrointestinal cancers, two lymphomas), and benign effusions (five patients) were collected and analyzed for heparanase content (enzyme-linked immunosorbent assay). Eighty-one mesothelioma biopsies were analyzed by H-Score for the prognostic impact of heparanase using immunohistochemistry. All statistical tests were two-sided.Results: Mesothelioma tumor growth, measured by bioluminescence or tumor weight at termination, was markedly attenuated by heparanase gene silencing (P = .02) and by heparanase inhibitors (PG545 and defibrotide; P < .001 and P = .01, respectively). A marked increase in survival of the mesothelioma-bearing mice (P < .001) was recorded. Heparanase inhibitors were more potent in vivo than conventional chemotherapy. Clinically, heparanase levels in patients' pleural effusions could distinguish between malignant and benign effusions, and a heparanase H-score above 90 was associated with reduced patient survival (hazard ratio = 1.89, 95% confidence interval = 1.09 to 3.27, P = .03).Conclusions: Our results imply that heparanase is clinically relevant in mesothelioma development. Given these preclinical and clinical data, heparanase appears to be an important mediator of mesothelioma, and heparanase inhibitors are worthy of investigation as a new therapeutic modality in mesothelioma clinical trials. [ABSTRACT FROM AUTHOR]

Aims: The secretion of enzymatically active heparanase (HepA) has been implicated as an essential metabolic adaptation in the heart following diabetes. However, the regulation and function of the enzymatically inactive heparanase (HepL) remain poorly understood. We hypothesized that in response to high glucose (HG) and secretion of HepL from the endothelial cell (EC), HepL uptake and function can protect the cardiomyocyte by modifying its cell death signature. Methods and results: HG promoted both HepL and HepA secretion from microvascular (rat heart micro vessel endothelial cells, RHMEC) and macrovascular (rat aortic endothelial cells, RAOEC) EC. However, only RAOEC were capable of HepL reuptake. This occurred through a low-density lipoprotein receptor-related protein 1 (LRP1) dependent mechanism, as LRP1 inhibition using small interfering RNA (siRNA), receptor-associated protein, or an LRP1 neutralizing antibody significantly reduced uptake. In cardiomyocytes, which have a negligible amount of heparanase gene expression, LRP1 also participated in the uptake of HepL. Exogenous addition of HepL to rat cardiomyocytes produced a dramatically altered expression of apoptosis-related genes, and protection against HG and H2O2 induced cell death. Cardiomyocytes from acutely diabetic rats demonstrated a robust increase in LRP1 expression and levels of heparanase, a pro-survival gene signature, and limited evidence of cell death, observations that were not apparent following chronic and progressive diabetes. Conclusion: Our results highlight EC-to-cardiomyocyte transfer of heparanase to modulate the cardiomyocyte cell death signature. This mechanism was observed in the acutely diabetic heart, and its interruption following chronic diabetes may contribute towards the development of diabetic cardiomyopathy. [ABSTRACT FROM AUTHOR]

Inflammation and cancer are related pathologies acting synergistically to promote tumor progression. In both, hematogenous metastasis and inflammation, P-selectin participates in interactions involving tumor cells, platelets, leukocytes and endothelium. Heparin has been shown to inhibit P-selectin and as a consequence it blunts metastasis and inflammation. Some heparin analogs obtained from marine invertebrates are P-selectin inhibitors and do not induce bleeding effects. The present work focuses on the P-selectin blocking activity of a unique heparan sulfate (HS) from the bivalve mollusk Nodipecten nodosus. Initially, we showed that the mollusk HS inhibited LS180 colon carcinoma cell adhesion to immobilized P-selectin in a dose-dependent manner. In addition, we demonstrated that this glycan attenuates leukocyte rolling on activated endothelium and inflammatory cell recruitment in thioglycollate-induced peritonitis in mice. Biochemical analysis indicated that the invertebrate glycan also inhibits heparanase, a key player in cell invasion and metastasis. Experimental metastasis of Lewis lung carcinoma cells was drastically attenuated by the mollusk HS through a mechanism involving inhibition of platelet-tumor-cell complex formation in blood vessels. These data suggest that the mollusk HS is a potential alternative to heparin for inhibiting P-selectin-mediated events such as metastasis and inflammatory cell recruitment. [ABSTRACT FROM AUTHOR]

Background: Heparanase is an endoglycosidase that degrades heparan sulfate, the main polysaccharide constituent of the extracellular matrix and basement membrane. Expression of the heparanase gene is associated with the invasive, angiogenic, and metastatic potential of diverse malignant tumors and cell lines. We used gene-silencing strategies to evaluate the role of heparanase in malignancy and to explore the therapeutic potential of its specific targeting. Methods: We designed plasmid vectors to express hammerhead ribozymes or small interfering RNAs (siRNAs) directed against the human or mouse heparanase mRNAs. Human breast carcinoma (MDA-MB-435) and mouse lymphoma (Eb) and melanoma (B16-BL6) tumor cell lines, which have naturally high levels of endogenous heparanase or have been genetically engineered to overexpress heparanase, were transfected with anti-heparanase ribozyme or siRNA. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and measurements of enzymatic activity were used to confirm the efficient silencing of heparanase gene expression. Cells transfected with the anti-heparanase ribozyme and siRNA vectors were tested for invasiveness in vitro and metastatic dissemination in animal models of experimental and spontaneous metastasis. Results: Compared with cells transfected with control constructs, cells transfected with the anti-heparanase ribozyme or siRNA vectors had profoundly reduced invasion and adhesion in vitro, regardless of cell type, and expressed less heparanase. In vivo, tumors produced by cells transfected with the anti- heparanase ribozyme and siRNA vectors were less vascularized and less metastatic than tumors produced by cells transfected with the control vectors. Mice injected with cells transfected with the anti-heparanase ribozyme and siRNA vectors lived longer than mice injected with control cells. Conclusions: The association of reduced levels of heparanase and altered tumorigenic properties in cells with anti-heparanase ribozyme- or siRNA-mediated gene-silencing vectors suggests that heparanase is important in cancer progression. Heparanase gene silencing has potential use as a target for anticancer drug development. [ABSTRACT FROM AUTHOR]