[The clinical prospects for the study of the plasminogen activation system in breast cancer]

Urokinase-type plasminogen activator (UPA) which is a serine protease may play a key role in the processes of tumor invasion and metastasis since it converts plasminogen to plasmin and initiates a cascade of proteolytic events that lead to the degradation of extracellular matrix. Experiments have demonstrated that some other components, except UPA itself, can be very important in this process, including UPA receptor (UPAR) and UPA inhibitors PAI-1 and PAI-2. All these proteins are present either in the tumor cells or in the tumor-infiltrating macrophages and stromal elements, and by acting in concert, they provide a feed-back-regulated mechanism of plasmin activation and amplification. Clinical retrospective studies using predominantly ELISA techniques have shown that the high levels of UPA, PAI-1 and UPAR in the tumor tissue are associated with poor prognosis both for overall and for disease-free survival of breast cancer patients, and the elevated level of PAI-2 may be indicative of better survival. UPA and PAI-1 are now regarded as rather potent independent predictors in breast cancer. Further clinical prospects of investigations and application of the components of the plasminogen activation system are discussed.