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Cancer cells require the ability to degrade the extracellular matrix (ECM) in order to turn into invasive and metastatic cancer cells. Many proteases and glycosidases are essential in the process of dissolving the components of the ECM. An endo-β β β β-D-glucuronidase, heparanase, is capable of specifically degrading one of the ECM components, heparan sulfate, and this activity is associated with the metastatic potential of tumor cells. Since heparanase mRNA is overexpressed in many human tumors (e.g., hepatomas, head and neck tumors, and esophageal carcinomas), the mechanisms regulating the activity of heparanase should be clarified; considering the possible role of heparanase in cancer, the development of heparanase inhibitors would appear to be advantageous. This review will focus on recent findings that have contributed to the characterization of heparanase and to the elucidation of the transcriptional regulation of heparanase mRNA expression, as well as the development of heparanase inhibitors. tudies of the biological function of extracellular matrix (ECM) molecules have revealed the central role of heparan sulfate proteoglycans (HSPGs) in many biological events, such as early embryogenesis and angiogenesis.1, 2) Heparan sulfate (HS) chains, consisting of strongly anionic linear polysaccharides, are structurally heterogeneous and bind a diverse repertoire of proteins under physiological conditions. Cell surface HS provides cells with a mechanism to snare a wide variety of extracellular effectors. These cell surface HSPGs modulate the activity of a wide variety of HS-binding proteins, acting as coreceptors with signaling receptors and directly as endocytosis receptors.3) As co-receptors, they potentiate the activity of sparse ligands by enhancing the formation of ligand-receptor complexes. In addition, intracellular signaling and endocytosis are augmented when HSPGs interact with soluble ligands. 1-3)HS/HSPG is known to interact with various molecules, 3) such as growth factors (e.g., fibroblast growth factors), cytokines (e.g., interleukin-2), ECM proteins (e.g., collagens), factors involved in blood coagulation (e.g., heparin cofactor II), and other proteins such as β-amyloid proteins and matrix metalloproteinase-7.1, 2, 4) Since HS chains are very similar among organisms as diverse as insects, mollusks, and mammals, the conservation of HS binding to extracellular proteins suggests that the association of these proteins with HS is conserved and functionally relevant. Because of the important and pleiotropic roles of HSPGs in cell physiology, the cleavage of HSPGs is likely to alter the integrity and functional state of tissues and to provide a mechanism by which cells can respond rapidly to changes in the extracellular environment. HS/HSPG carbohydrate chains are cleaved either by lyases (eliminative cleavage) or hydrolases (hydrolytic cleavage). These cleaving enzymes are therefore in part responsible for the modulation of the biological functions of HS/HSPGs-binding proteins. The enzymatic degradation o...

The endo-␤-D-glucuronidase, heparanase, is capable of specifically degrading heparan sulfate, and this activity is associated with the metastatic potential of tumor cells. The predicted amino acid sequence of heparanase includes six putative N-glycosylation sites; however, the precise biochemical role of glycosylated heparanase remains unknown. In this study, we examined the link between glycosylation and the function of heparanase in human tumor cell lines. Heparanase protein was glycosylated at six Asn residues in human tumor cell lines. Treatment with a glycosylation inhibitor demonstrated that glycosylation was not required for the activity of heparanase. However, glycosylation affected the kinetics of endoplasmic reticulum-to-Golgi transport and of secretion of the enzyme.

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