Urokinase-type plasminogen activator and its inhibitor in thyroid neoplasms: a cytosol study

Higher levels of urokinase-type plasminogen activator (uPA) and its inhibitor (PAI-1) are linked to the poor prognosis in a variety of malignances. uPA and PAI-1 were expressed in most thyroid carcinomas, as had been measured immunohistochemically. However, no relationship between their expression and clinicopathological parameters were found. Aim of the present study was to investigate the expression and clinical relevance of uPA and PAI-1 in thyroid cancer.

uPA and PAI-1 in paired cytosol samples of thyroid tumor and normal tissue were determined in 23 patients using enzyme-linked immunosorbent assay and correlated to the known prognostic features.

Both uPA and PAI-1 concentrations were significantly higher in malignant thyroid tumors (uPA=1.342 +/- 2.944 and PAI-1=17.615 +/- 31.933 ng/mg protein) than in normal tissue (uPA=0.002 +/- 0.009, P=0.011 and PAI-1=2.333 +/- 0.338 ng/mg protein, P=0.001) with positive correlation of the two proteins in the tumors. There were no differences in proteins' levels between benign tumors and normal tissue. Both proteins' concentrations were significantly different among various histological grades (uPA P=0.024 and PAI-1 P=0.017), showing higher values in higher tumor grades (grade I uPA=0.116 +/- 0.247 and PAI-1=4.802 +/- 4.151 ng/mg protein; grade III uPA=8.45 +/- 2.192 and PAI-1=94.65 +/- 59.468 ng/mg protein). The uPA and PAI-1 levels showed significant differences among different histological types of thyroid cancer (uPA P=0.049 and PAI-1=0.017). The lowest values were in adenomas (uPA=0.013 +/- 0.025 and PAI-1=2.785 +/- 1.069 ng/mg protein) and the highest in anaplastic carcinomas (uPA=8.45 +/- 2.192 and PAI-1=94.65 +/- 59.468 ng/mg protein). uPA and PAI-1 were significantly higher in anaplastic vs. well-differentiated cancers (uPA P=0.014 and PAI-1 P=0.026), if extrathyroidal invasion (uPA P=0.019 and PAI-1 P=0.009) or distant metastases (uPA P=0.006 and PAI-1 P=0.003) had been present, and in tumors whose size exceeded 1 cm in diameter (uPA P=0.009 and PAI-1 P=0.035). Only PAI-1, but not uPA was significantly higher in multicentric vs. solitary tumors (P=0.012) and lymph node positive compared to lymph node negative patients (P=0.042). The differences of uPA and PAI-1 did not reach the significant level when patients with well-differentiated tumors below and above 40 years of age had been compared. Survival analysis revealed the significant impact of both uPA and PAI-1 on the Progression-Free Survival (PFS) (38.84 vs. 3.67 months for patients with low and high uPA, respectively, P<0.001; 38.2 vs. 12 months for patients with low and high PAI-1, respectively, P=0.016).

The correlation of high uPA and PAI-1 with the known prognostic factors of poorer outcome and with lower PFS rate in patients with thyroid cancers proved that these proteins could be an additional prognostic parameter.