Tissue-type plasminogen activator in breast cancer: relationship with estradiol and progesterone receptors.

Plasminogen activator (PA) is an estradiol-inducible enzyme and therefore a potential marker for a functional estradiol receptor (ER) in human breast carcinomas. In this investigation tissue-type PA (t-PA) correlated significantly with both ER and progesterone receptors (PR) in human breast carcinomas. In contrast, neither total PA activity nor urokinase-like PA showed any significant correlation with either ER or PR. Other proteases such as a trypsin-like protease, a chymotrypsin-like protease, and cathepsin B also showed no correlation with ER and PR. It was concluded that the t-PA form of PA may be a marker for a functional ER in breast carcinoma and thus be of value in predicting hormone-dependent breast cancers.