Measurement of plasminogen activator activity from human fibrosarcoma cells by a new microassay.
Elevated levels of plasminogen activator (PA) activity have been correlated with neoplasia and may have an important role in tumor-cell invasion and metastasis. We have developed a new caseinolytic assay that uses an immunochemical approach to measure the activity of PA elaborated by malignant tumor cells. The highly sensitive assay consists in incubating a source of PA (viable tumor cells, cell extracts, or conditioned medium) with purified plasminogen in microtiter plates precoated with a suitable protein substrate such as casein. Clearance of the immobilized protein substrate by PA-generated plasmin is then measured by a technique based on the enzyme-linked immunosorbent assay. In experiments using urokinase as a source of PA, the assay displayed near linearity over several log units of urokinase activity and could detect as little as 10(-2) Ploug units of PA activity. Besides successfully measuring PA activity produced by the human HT 1080 fibrosarcoma cell line, the assay permitted detection of significant plasminogen-independent proteolytic activity generated by intact tumor cells cultured in direct contact with immobilized protein substrates.
Department of Anatomy, School of Medicine, University of California, San Francisco 94143.
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Rezaee
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Chen
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RH
Kramer
D002364:Caseins / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005354:Fibrosarcoma / Q000201:enzymology*; D006801:Humans; D008832:Microchemistry; D009363:Neoplasm Proteins / Q000032:analysis*; D010958:Plasminogen; D010960:Plasminogen Activators / Q000032:analysis*; D014568:Urokinase-Type Plasminogen Activator / Q000032:analysis
D002364:Caseins; D009363:Neoplasm Proteins; D010958:Plasminogen; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator