[The concentration of tissue--type plasminogen activator (t-PA) in extracts of breast cancer tissue]

Degradation of the extracellular matrix metalloproteinases, which are activated mainly by the plasmin (the key enzyme of the fibrinolysis system), is the basis of the invasion of breast cancer cells. The tissue plasminogen activator (t-PA), a specific serine protease, is one of the plasmin activators. Shifting the balance between factors stimulating and inhibiting angiogenesis within the tumour microenvironment it influences negatively the progression of breast cancer. The aim of the study was to estimate the concentration of t-PA levels in breast cancer tissue extracts in comparison with normal breast tissues as well as to analyze the t-PA level changes in relation to "classical" prognostic factors.

A total number of 30 breast cancer patients aged from 39-79 (mean 58) years entered the study. According to the TNM system the pathological stage of the disease was assessed and the estrogen (ER) and progesterone (PgR) receptor status was determined for each patient. Additionally, in ten patients aged from 29-44 (mean 33) years the level of the t-PA in benign breast tissue lesions was determined. The studied tissues were obtained during surgery. Macroscopically normal tissues, which were located 2 cm from the tumor, served as a controls group. Levels of the t-PA were determined using the enzyme-linked immunosorbent assay (ELISA).

The study showed no statistically significant difference between the levels of the t-PA in tumors and in normal tissues. In terms of prognostic factors t-PA level was significantly higher in cancer tissues obtained from patients with no lymph node metastases as well as in tumors containing progesterone receptors. The PgR levels were significantly higher in benign breast lesions in comparison with both, normal tissues and tumors.

The study showed a significant relationship between the high level of t-PA and a favorable prognosis estimated on the basis of "classical" prognostic factors.