Metastasis is the ultimate stage of tumor progression and is the major cause of morbidity and mortality in cancer patients. The central theme of this research proposal is to investigate whether this process can be modulated and ultimately suppressed. Matrix metalloproteinases (MMPs) a family of endopeptidases with proteolytic activity for several essential constituents of the extracellular matrix (ECM) are secreted in abundance by metastatic tumor cells enabling them to invade surrounding tissues and to metastasize. We hypothesize that during invasion, the homeostatic balance between these enzymes and their corresponding activators and inhibitors is perturbed toward excess proteolysis and degradation of the ECM. We propose to modify this perturbed balance using a specific and novel metalloproteinase inhibitor designated metalloproteinase inhibitor/tissue inhibitor of metalloproteinase-2 (MI/TIMP-2) recently isolated in our laboratory. Biological and regulatory aspects of this inhibitor will be examined. We will change the enzyme-inhibitor balance in metastatic tumor cells toward excess inhibition using recombinant human MI/TIMP-2 and by transfecting these cells with MI/TIMP-2 cDNA in mammalian expression vectors. Experiments win also be performed with recombinant inhibitors of plasminogen activator (PAls) and PAI's cDNA used in combination with MI/TIMP-2 to examine the effect of the additional inhibition of another proteolytic cascade. The effect of these changes on the proteolytic activity and on the invasive and metastatic potentials of these cells will be analyzed. Experiments on regulatory aspects of MI/TIMP-2 will investigate whether this inhibitor is similarly regulated in normal cells and tumor cells and whether its regulation is independent from TIMP. These studies will determine whether invasion and metastasis are processes that can be controlled if the normal homeostasis between tumor cells and their surrounding tissue is restored. Our knowledge of regulatory mechanisms that control this homeostasis could then be used to prevent or suppress tumor invasion and metastasis.
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