Tissue-type plasminogen activator as marker of functional steroid receptors in human breast cancer

The relationship between tissue-type plasminogen activator (t-PA) antigen content and receptor status was investigated in 200 human breast cancer cytosols to evaluate the efficacy of t-PA as a marker of functional steroid receptors. t-PA level was measured by an enzyme-linked immunoassay (ELISA) and estrogen (ER) and progesterone (PgR) receptors were assayed by the DCC method. A highly significant correlation was found between t-PA levels and receptor status. The mean +/- SE enzyme content was 13.5 +/- 2.9 in ER+ tumors and 1.8 +/- 0.3 ng/mg protein in ER- tumors; the enzyme content in PgR+ tumors was 14.2 +/- 3.3 and 3.4 +/- 1.4 ng/mg protein in PgR- tumors. When tumors were divided into four subgroups according to receptor content (ER+PgR+, ER+PgR-, ER-PgR+, and ER-PgR-), t-PA concentration was able to differentiate these groups. Also, t-PA level was compared to several clinical variables; it was not correlated with menopausal status or lymph node involvement. However, t-PA content varied according to tumor size. Our data shows that t-PA content in tumor cytosols is statistically related to receptor status and that determination of t-PA levels in breast cancer might furnish additional information as to the functional state of the receptors which may be necessary for planning hormone therapy.