Elevated Plasma Levels of Urokinase Plasminogen Activator Receptor in Non-Small Cell Lung Cancer Patients

The urokinase plasminogen activator (uPA) is involved in extracellular matrix degradation during cancer invasion. Binding of uPA to a specific cell surface receptor (uPAR) is a key step in this process. We have previously reported that high levels of uPAR in squamous cell lung cancer tissue extracts are associated with poor prognosis (Pedersen et al., Cancer Res 1994, 54, 4671–4675). Recently we found that uPAR is present in blood plasma from healthy donors as determined by enzyme-linked immunosorbent assay (ELISA) and chemical cross-linking. We now report that uPAR in plasma from 17 patients with non-small cell lung cancer (NSCLC) was significantly higher than in 30 healthy controls (P = 0.0004), while no significant increase was found in plasma from 14 patients with small cell lung cancer (SCLC). The increased levels of uPAR in the plasma from NSCLC patients is likely to be due to release of uPAR from the tumour tissue, and may, therefore, be related to prognosis.