Clinical relevance of the urokinase plasminogen activator system in breast cancer

Until recently clinical features and the hormone‐receptor status were the only factors used to select systemic (adjuvant) treatment for breast cancer patients. Other biological factors are needed as well to predict the probability of relapse and response with more certainty. The uPA‐system is such a prognostic and predictive factor in breast cancer. In this review, the results of research groups that have related relapse‐free survival to the quantitative levels of uPA‐system proteins and/or activities are discussed. Only studies that described the results from assays on cytosols or triton extracts of breast tumours were included. The levels of uPA‐system proteins help to predict the probability of relapse and response, and knowledge of the expression levels of the various components of the uPA‐system may lead to new treatment modalities targeted on specific properties of the uPA‐system.