Urokinase-type plasminogen activator (u-PA) is known to be secreted by
malignant cells during proliferation and migration, and is associated
with tumour cell invasion and metastasis. This study was undertaken t
o evaluate whether u-PA is significantly increased in carcinomatous pl
eural fluids compared to those due to other aetiologies, and to identi
fy the cells in the pleural space that are involved in its accumulatio
n, Using an enzyme-linked immunosorbent assay, we quantified u-PA in t
he pleural fluid specimens of 40 patients with carcinomatous pleuritis
, 18 with tuberculosis, 18 with parapneumonic pleuritis and 11 with co
ngestive heart failure (CHF), The level of u-PA was elevated in carcin
omatous pleural fluid compared with the level in transudative pleural
fluid from patients with CHF (p<0,0001), The levels of u-PA were not s
tatistically different between patients with cancer and tuberculosis,
or between patients with cancer and pneumonia The levels of u-PA in pa
tients who did not respond to chemical pleurodesis were significantly
higher than those who had complete response (p=0,0001), In immunocytoc
hemical and immunoblotting studies, cancer cells in pleural fluids as
well as mesothelial cells contained u-PA, u-PA was detected in the cul
ture supernatants of viable pleural cells in the majority of patients
with carcinomatous pleuritis, Our results suggest that local release o
f urokinase-type plasminogen activator by viable cells, including canc
er cells and mesothelial cells, may affect the levels of urokinase-typ
e plasminogen activator in pleural fluids.