Tissue urokinase-type plasminogen activator receptor levels in breast cancer

Cancer invasion is induced by several proteolytic enzyme systems associated with the destruction of basement membrane and extracellular matrix. Urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) have been reported as prognostic factors in breast cancer patients and plasminogen activation is regulated by various factors such as uPAR and growth factors. Thus, we examined the tissue levels of urokinase-type plasminogen activator receptor (uPAR) in breast cancer patients. Tissue uPAR levels were measured by ELISA assay in 268 breast cancer patients. The median and mean values of tissue uPAR level in breast cancer were 3.5 ng/mg cytosol protein and 4.8+/-3.6 ng/mg cytosol protein, respectively. Tissue uPAR level was the highest in T1 stage, but there was no statistical significance between the T stages (p>0.05), nor in nodal stage, in the value of uPAR according to progression. And the value of uPAR expression was not associated with estrogen and progesterone receptor status, number of involved node and percent of node involvement. In TNM stage, tissue uPAR levels were higher in patients with stage I-II than in patients with stage III-IV (p=0.027). In univariate analysis, nodal factor (p=0.002) and TNM stage (p=0.0004) were significant. But, multivariate analysis showed that TNM stage was the only significant prognostic factor (p=0.0002). These results suggest that uPAR is mainly associated with initial tumor invasion and other factors might be involved in later stages of cancer progression.