Association of plasminogen activator activity and steroid receptors in human breast cancer

Plasminogen activating activity (PAA) has been determined in 105 human breast cancer cytosols with a colorimetric assay. PAA has been related to steroid receptors in the same cytosols. A strong positive correlation between PAA and progesterone receptor levels was found (Spearmans coefficient of rank correlation, R - 0.74, P less than 0.001). PAA discriminates between progesterone receptor-positive and -negative tumours, irrespective of oestradiol receptor content. It is suggested that PAA is a marker of functional oestradiol receptor and that fibrinolytic activity may be a causative factor in the low metastatic potential of progesterone receptor-positive tumours.