Breast cancer prognosis is poor when total plasminogen activator activity is low

Plasminogen activator (PA) is a serine protease which exists in two forms: tissue-type (t-PA) and urokinase-type (u-PA). The total PA activity was measured in tumour extracts of 235 breast cancer patients who were followed for a median of 8.5 years after surgery. Patients were initially divided into three groups with low (< 60 units mg-1 protein), intermediate (60-300 unit mg-1 protein), or high (> 300 unit mg-1 protein) total PA activity in tumour extracts. The PA activity was not significantly associated with the recognised prognostic factors of age, menstrual status, tumour size, lymph node involvement, histologic type, grade of anaplasia, and/or vessel involvement. A significant association was found between total PA activity and the oestrogen receptor (ER) or progesterone receptor (PgR) status. Among receptor-positive tumours, a significantly greater proportion of patients had high PA activity in their tumour extracts. Breast cancer patients with low total PA activity had a significantly shorter disease-free and overall survival rate when compared to those with intermediate or high PA activity. In univariate and multivariate analyses, total PA activity (< 60 unit mg-1 vs > or = 60 unit mg-1 protein) was found to be a significant prognostic factor for disease-free and overall survival of about the same import as lymph node involvement. Furthermore, the combination of total PA activity and nodal status could be even more precise in predicting survival times and probabilities in individual patients. This retrospective study demonstrates the total PA activity is a valuable prognostic factor in determining prognosis in human breast cancer.