Plasminogen activator as a functional marker for estrogen dependence in human breast cancer cells

To examine whether plasminogen activator reflects the functional state of estrogen receptors in human breast cancer, the enzyme activities were determined in extracts prepared from 160 breast cancer specimens and compared on qualitative and quantitative bases with the levels of steroid receptors, such as cytoplasmic estrogen receptor (ERC), progesterone receptor (PgR) and nuclear estrogen receptor (ERN). With any receptor, plasminogen activator activity was significantly higher in receptor-positive tumors than in receptor-negative tumors. When these breast tumors were categorized into 8 groups in terms of combinations of receptor status, breast cancers which were positive for all these receptors were found to contain the highest plasminogen activator activity. Furthermore, quantitative analyses demonstrated positive correlations of the enzyme activity with either ERC content (correlation coefficient +0.37, P less than 0.001) or PgR content (correlation coefficient +0.45, P less than 0.001). These results strongly suggest that plasminogen activator can be used as an effective functional marker for hormone dependence in human breast cancer.