heparitin-sulfate and Mouth-Neoplasms

In previous studies, we have demonstrated that human heparanase (endo-beta-D-glucuronidase) is localized primarily in a perinuclear pattern within lysosomes and late endosomes, and occasionally may be surface associated and secreted. The presence of two potential nuclear localization sequences in human heparanase, led us to investigate heparanase translocation into the nucleus and subsequent degradation of nuclear heparan sulfate. Applying cell fractionation, Western blot analysis, determination of heparanase activity and confocal microscopy, we identified heparanase within the nuclei of human glioma and breast carcinoma cells and estimated its amount to be about 7% of the cytosolic enzyme. Our results indicate that nuclear heparanase colocalizes with nuclear heparan sulfate and is enzymaticaly active. Moreover, following uptake of latent 65 kDa heparanase by cells that do not express the enzyme, an active 50 kDa heparanase was detected in the cell nucleus, capable of degrading both nuclear and extracellular matrix-derived heparan sulfate. Immunohistochemical examination of human squamous cell carcinoma specimens revealed a prominent granular staining of heparanase within the nuclei of the epithelial tumor cells vs no nuclear staining in the adjacent stromal cells. Taken together, it appears that heparanase is translocated into the cell nucleus where it may degrade the nuclear heparan sulfate and thereby affect nuclear functions that are thought to be regulated by heparan sulfate. Nuclear localization of heparanase suggests that the enzyme may fulfill nontraditional functions (ie, regulation of gene expression and signal transduction) apart of its well-documented involvement in cancer metastasis, angiogenesis and inflammation.

Topics: Active Transport, Cell Nucleus; Amino Acid Sequence; Animals; Carcinoma, Squamous Cell; Cell Line, Tumor; Cell Nucleus; Glucuronidase; Heparin; Heparitin Sulfate; Humans; Molecular Sequence Data; Mouth Neoplasms; Nuclear Localization Signals; Rats; Recombinant Proteins; Substrate Specificity; Transfection

Acidic glycoconjugates represent the major non-fibrous macromolecular components that form the extracellular and cell-associated matrices of all animal tissues. The constituent molecules are principally structural glycoproteins and proteoglycans. While their protein component is determined by gene pools, it is the polyanionic (acidic) nature of the polysaccharides, determined by their degrees of carboxylation and sulphation, which confers both functional and diagnostic status on these molecules. Sulphated glycoconjugates in the basal laminae have been reported to play a role in tumour invasion and metastasis. In this study, we used cationic colloidal gold together with transmission electron microscopic methods to compare the expression of acidic glyconconjugates in the basal lamina of both normal rat tongue mucosa and experimentally induced oral carcinomas. Results indicated that heparan sulphate rich glycoconjugates were predominant and were mostly confined to the lamina lucida of the basal lamina in normal oral mucosa. Conversely, observation of basal laminae associated with induced carcinomas showed less intense and more widely dispersed gold labelling for heparan sulphate. The observed differences in gold labelling may reflect modified metabolism of sulphated glycoconjugates or result from the action of degradative enzymes in the induced tumours.

Topics: 4-Nitroquinoline-1-oxide; Animals; Basement Membrane; Carcinogens; Female; Glycoconjugates; Gold; Heparan Sulfate Proteoglycans; Heparitin Sulfate; Hydrogen-Ion Concentration; Mouth Mucosa; Mouth Neoplasms; Neuraminidase; Polylysine; Proteoglycans; Rats; Rats, Wistar