Evidence that sulphated polysaccharides inhibit tumour metastasis by blocking tumour‐cell‐derived heparanases

Abstract

Recent studies in this laboratory demonstrated that several sulphated polysaccharides can inhibit metastasis of the rat mammary adenocarcinoma 13762 MAT, probably by preventing the passage of tumour cells through the walls of blood vessels. In order to directly test this possibility, 13762 MAT cells were cultured with (35S)O4(=)-labelled subendothelial extracellular matrices (ECM) and ECM degradation was monitored in either the presence or absence of different sulphated polysaccharides. Degradation products were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis and subsequent autoradiography. The 5 sulphated polysaccharides that had previously been shown to possess anti-metastatic activity were potent inhibitors of the degradation of subendothelial ECM by 13762 MAT cells. In contrast, of the 4 polysaccharides tested that failed to inhibit metastasis, 3 had no effect on ECM breakdown and one (carrageenan-kappa) was substantially less effective at inhibiting ECM degradation than the anti-metastatic preparations. It was also shown that 13762 MAT cells produce a heparan sulphate-specific glycosidase (heparanase) that degrades the heparan sulphate side-chains of the ECM, the action of this enzyme rather than that of other ECM-solubilizing enzymes being inhibited by the antimetastatic sulphated polysaccharides. Additional experiments indicated that the anti-coagulant activity of the polysaccharides probably plays a minor role in their anti-metastatic effects since heparin, almost completely depleted (98-99.5%) of heparin molecules with anti-coagulant activity by passage over an anti-thrombin III column, retained its ability to inhibit 13762 MAT heparanases and was almost as effective as unfractionated heparin at inhibiting tumour-cell metastasis. Collectively, these data suggest that sulphated polysaccharides inhibit the metastasis of 13762 MAT cells by inhibiting tumour-cell-derived heparanases involved in the penetration of the vascular endothelium and its underlying basement membrane by tumour cells.

Modulation of the Heparanase-inhibiting Activity of Heparin through Selective Desulfation, Graded N-Acetylation, and Glycol Splitting

“…This activity is attributed, in part, to its high affinity interaction with the enzyme and limited degradation, serving as an alternative substrate. Early reports (20,21,30,31) showed that heparin and some chemically modified species of heparin as well as other sulfated polysaccharides (22,32) that inhibit tumor cell heparanase also inhibit experimental metastasis in animal models, while other related compounds that lack heparanase-inhibiting activity fail to exert an antimetastatic effect (20 -22, 30 -32). Regardless of the mode of action, heparin and low molecular weight heparin (LMWH) were reported to exert a beneficial effect in cancer patients (33), stimulating research on the potential use of modified, nonanticoagulant species of heparin and HS in cancer therapy.…”

Cell surface expression and secretion of heparanase markedly promote tumor angiogenesis and metastasis

“…Mammalian endoglycosidase (heparanase), capable of partially depolymerizing heparan sulfate (HS) chains, has been identified in highly invasive normal and malignant cells, including cytotrophoblasts, activated cells of the immune system, lymphoma, melanoma, and carcinoma cells (5)(6)(7)(8)(9). In fact, expression of heparanase has long been correlated with the metastatic potential of tumor cells and treatment with heparanase inhibitors markedly reduced the incidence of experimental metastasis and autoimmunity (6)(7)(8)(9)(10)(11)(12)(13). The significance of heparanase in tumor progression is emphasized further in recent studies performed since the cloning and expression of a single gene encoding heparanase (14)(15)(16)(17)(18).…”

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

“…Heparanase is an HSspecific endo-␤-D-glucuronidase and a critical molecular determinant of tumor metastasis because its activity directly correlates with metastasis of tumor cells, being involved in their invasiveness. [1][2][3][7][8][9][10] We and others have postulated 2 roles of heparanase in melanoma metastasis: One is that heparanase is relevant to the extravasation of melanoma cells into secondary organs by degrading subendothelial ECM HSPG degradation, whereas the second pertains to heparanase's ability to release angiogenic factors, stored within ECM HSPG, at the metastatic site and leading edge of neovascularization. The mobilization of these factors and their angiogenic stimulation is a critical event in angiogenesis.…”

“…14 -16 A number of studies have demonstrated that heparanase activity and experimental metastasis are inhibited by nonanticoagulant and low-molecular-weight species of heparin. 2,6,37 It also has been demonstrated that a variety of sulfated polysaccharides other than heparin can inhibit heparanase and tumor growth. 38 -40 Finally, and relevant to the purpose of our study, reports have documented heparanase inhibition by suramin.…”

“…[1][2][3] Cleavage of HS results in disassembly of subendothelial ECM and hence may play a decisive role in extravasation of blood-borne cells. Among the cellular enzymes involved in BM/ECM degradation is an endo-␤-D-glucuronidase called heparanase that cleaves HS at specific intrachain sites.…”