Degradation Of Extracellular Matrices Research Articles

Inhibition of tumor cell invasion and matrix degradation by aminopeptidase inhibitors.

We investigated the effects of several types of aminopeptidase inhibitors on tumor cell-associated aminopeptidase activity and invasion. The aminopeptidase expressed by the human metastatic HT1080 fibrosarcoma cells was effectively suppressed by actinonin A, bestatin, leuhistin and matlystatin A, which are capable of inhibiting the purified aminopeptidase N, but not by arphamenine B specific for aminopeptidase B. The aminopeptidase N inhibitors inhibited HT1080 cells from degrading the subendothelial matrix and from invading into Matrigel in parallel with their aminopeptidase inhibitory activities. Matlystatin A, with multiple inhibitory activity against both aminopeptidase N and matrix metalloproteinases (MMP), was the most effective inhibitor of invasion. However, leuhistin and bestatin, without MMP inhibitory activity, also exhibited significant inhibition of invasion. The results suggest that aminopeptidase N plays a crucial role in the degradation and invasion of extracellular matrices by fibrosarcoma cells and that aminopeptidase inhibitors may be useful for preventing the spread of malignant tumors.

The signals and molecular pathways involved in human menstruation, a unique process of tissue destruction and remodelling.

Human endometrium is a specialized tissue that undergoes sequential phases of proliferation and secretory changes in order to support the implantation and growth of an embryo. If implantation does not occur, this tissue rapidly undergoes dissolution during the menstrual period. Tissue shedding during menstruation is associated with significant apoptosis, disordered expression of adhesion molecules, loss of filamentous (F) actin from cell borders and fragmentation of endometrial glands. On the other hand, compromise of integrity of vessels and dissolution of the extracellular matrix leads to bleeding and tissue dissolution. The processes of bleeding and tissue shedding during menstruation are precisely controlled by a number of systemic and local factors. The systemic signal that leads to menstruation is the withdrawal of the steroid hormones. The available evidence suggests but does not yet prove that tumour necrosis factor (TNF)-alpha may serve as the local signal contributing to the processes of menstrual shedding and bleeding. Secretion of metalloproteinases and their subsequent activation induced by plasmin facilitates degradation of extracellular matrices and bleeding. The menstrual process ceases by secretion of steroid hormones directly or through regulation of production or activation of signals that lead to tissue shedding and bleeding.

Preface: Tumor invasion and brain cancer

It is widely appreciated that the pathophysiology of advanced brain cancer is intimately related to the extent of tumor invasiveness. A pre-requisite for comprehensively understanding neuro-oncology is therefore the elucidation of the biochemical and molecular properties of tumor cells that contribute to their invasiveness. An understanding of tumor invasion for central nervous system tumors is crucial since malignant brain tumors are very highly invasive and extensively destroy adjacent neural brain tissue. Moreover, they are angiogenesis-dependent and lead to the death of patients by expanding within the limited space of the cranium. As more specific insights are gained towards a full understanding of the complex processes of tumor invasiveness of brain tumor cells, it should be possible to design strategies for the early diagnosis and treatment of invasive, advanced brain tumors. There is therefore an urgent need to better understand the cellular properties of brain tumor cells responsible for invasiveness. The investigation of the properties of tumor invasiveness has been and continues to be the intense focus of many basic research and clinical laboratories with interests in tumor progression including the establishment and outgrowth of tumor metastases [reviewed in 1-25]. Studies of tumor invasiveness have centered on: tumor cell attachment to microvascular endothelial cells and to subendothelial extracellular matrices, i.e. basement membranes; localized degradation of extracellular matrices mediated by tumor cell-associated proteolytic enzymes, and tumor cell migration into and through regions of the extracellular matrix degraded by proteolysis, which can be influenced by chemotactic factors. The continued invasion of the extracellular matrix may take place by cyclic repetition of these sequential, biochemical steps that characterize tumor invasion through extracellular matrices [reviewed in 1-25]. It is noteworthy that molecular events accompanying tumor invasion, including degradation of extracellular matrix basement membrane by tumor-associated proteases, share features associated with neovascularization. Since unusually high levels of tumor angiogenesis factors are also elaborated by tumor cells as brain cancer progression ensues, it is also important to consider that an intimate relationship may exist between tumor invasion and tumor angiogenesis in invasive brain cancer. This special issue of the Journal of Neuro-Oncol

Walker 256 Tumor Cell Degradation of Extracellular Matrices Involves a Latent Gelatinase Activated by Reactive Oxygen Species

The invasion of blood vessel walls is a critical step in cancer metastasis, in which endothelial cells and their vascular basement membranes act as barriers to tumor cell passage. Here we report that Walker 256 carcinosarcoma (W256) cells degrade subendothelial matrices by a process involving both the generation of hydrogen peroxide and the secretion of a matrix metalloproteinase. As an assay of basement membrane degradation, [ 3H]proline-labeled subendothelial matrices were exposed to W256 cells in the presence or absence of the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP). The release of [ 3H]proline, in the presence of 5 × 10 6 W256 cells, was increased from 49 ± 2.5 to 64 ± 2.2% by the addition of 10 −6 M fMLP. In the presence of fMLP-activated W256 cells, [ 3H]proline release was completely inhibited by the addition of 2000 units/ml catalase or by the metalloproteinase inhibitors 1,10-phenanthroline and EDTA at concentrations ≥ 10 μg/ml. α 1-Antitrypsin or α 2-macroglobulin were without effect. Cell-free supernatants obtained from activated W256 cells were also able to promote basement membrane degradation. Electrophoresis of the cell-free supernatants from fMLP or PMA-activated W256 cells in gelatin-containing sodium dodecyl sulfate-polyacrylamide gels revealed a major band of gelatinolytic activity at 94 kDa. The 94-kDa band represented the activity of a latent gelatinase since incubation with 1 mM 4-aminophenylmercuric acetate (APMA; a known activator of latent metalloproteinases) resulted in the loss of gelatinolytic activity at 94 kDa and the appearance of five new bands of lower molecular weight ( M r 86, 79, 74, 70, and 66 kDa). Two of these lower molecular weight bands ( M r 86 and 66 kDa) were also detected in the absence of APMA, following 10-fold concentration of the cell-free supernatants. When the cell-free supernatants of phorbol myristate acetate-activated W256 cells (concentrated 10-fold) were incubated with increasing concentrations of hydrogen peroxide (35 to 70 mM), the band at 66 kDa demonstrated enhanced gelatinolytic activity. We suggest that W256 cells can secrete a latent metalloproteinase of molecular weight 94 kDa which, when activated by hydrogen peroxide, can degrade subendothelial matrices.

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

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.