a monoclonal antibody which binds a human endothelial type plasminogen activator inhibitor (PAI-1) produced by dexamethasone-treated human HT-1080 fibrosarcoma cells may be used, inter alia, for determining PAI-1 protein abundance in tumor tissue or a sample of a body fluid. Measurements of this parameter may be useful in predicting the presence or metastasis of a tumor, or of predicting the progression of a known malignant tumor.