Detection of soluble urokinase receptor by immunoradiometric assay and its application in tumor patients

Circulating suPAR in two cohorts of primary FSGS

Overexpression of soluble urokinase receptor (suPAR) causes pathology in animal models similar to primary FSGS, and one recent study demonstrated elevated levels of serum suPAR in patients with the disease. Here, we analyzed circulating suPAR levels in two cohorts of children and adults with biopsy-proven primary FSGS: 70 patients from the North America-based FSGS clinical trial (CT) and 94 patients from PodoNet, the Europe-based consortium studying steroid-resistant nephrotic syndrome. Circulating suPAR levels were elevated in 84.3% and 55.3% of patients with FSGS patients in the CT and PodoNet cohorts, respectively, compared with 6% of controls (P<0.0001); inflammation did not account for this difference. Multiple regression analysis suggested that lower suPAR levels associated with higher estimated GFR, male sex, and treatment with mycophenolate mofetil. In the CT cohort, there was a positive association between the relative reduction of suPAR after 26 weeks of treatment and reduction of proteinuria, with higher odds for complete remission (P=0.04). In the PodoNet cohort, patients with an NPHS2 mutation had higher suPAR levels than those without a mutation. In conclusion, suPAR levels are elevated in geographically and ethnically diverse patients with FSGS and do not reflect a nonspecific proinflammatory milieu. The associations between a change in circulating suPAR with different therapeutic regimens and with remission support the role of suPAR in the pathogenesis of FSGS.

Expression of kallikrein 7 diminishes pancreatic cancer cell adhesion to vitronectin and enhances urokinase-type plasminogen activator receptor shedding

OBJECTIVES

To examine the effects of kallikrein 7 (KLK7) expression in pancreatic cancer cells on cell adhesion to extracellular matrix proteins.

METHODS

Kallikrein 7 was overexpressed in the pancreatic cancer cell line BxPC-3, and in vitro cell adhesion assays were performed to determine alterations in cell adhesion to collagen I, fibronectin, and vitronectin compared with vector-transfected cells. Changes in cell surface expression of alphavbeta3 integrin were examined by flow cytometry, and the release of soluble urokinase-type plasminogen activator receptor (uPAR) was monitored by Western blot analysis.

RESULTS

The expression of KLK7 in BxPC-3 cells led to reduced adhesion to vitronectin but not collagen I or fibronectin. Loss of cell adhesion to vitronectin was not caused by changes in the level of alphavbeta3 integrin cell surface expression; however, a significant increase in the amount of uPAR shed was observed in KLK7-expressing cells compared with vector-transfected control cells.

CONCLUSIONS

The aberrant expression of KLK7 in pancreatic cancer cells leads to a reduction in cell adhesion to vitronectin that may result from the cleavage of uPAR from the cell surface. Kallikrein 7 expression, therefore, may play an important role in the dissemination of tumor cells through the production of soluble uPAR in pancreatic cancer and perhaps other human malignancies.

Detection of urokinase plasminogen activator receptor and c-erbB-2 in sera of patients with breast and ovarian carcinoma

The role of urokinase plasminogen activator receptor (uPAR) and c-erbB-2 in breast and ovarian cancer was investigated. Eighty patients of breast and ovarian cancer and benign lesions, as well as twenty normal controls were evaluated for the expression of c-erbB-2 by Western blotting and uPAR levels by ELISA. The c-erbB-2 and uPAR showed a significant increase in both types of cancer investigated compared to normal control and benign lesions. The frequency of c-erbB-2 was significantly higher in breast cancer lesions (p < 0.01). Levels of CA15.3 in breast cancer and CA125 in ovarian cancer were significantly higher in cases expressing c-erbB-2 (p < 0.01) than in negative c-erbB-2 cases. The uPAR showed a significant positive correlation with advanced stages of breast cancer (r = 0.7971) and ovarian cancer (r = 0.83662), while significant correlations were found for CA15.3 in breast cancer (r = 0.64967) and CA125 in ovarian cancer (r = 0.83996). Taken together, our data suggest that the c-erbB-2 and uPAR in the sera of ovarian and breast cancer act as valuable markers for the evaluation of the patients preoperatively.

Clinical significance of urokinase-type plasminogen activator receptor (uPAR) expression in cancer

The involvement of the urokinase-type plasminogen activator (uPA) system in particular has been extensively studied in the pathogenesis of cancer. The molecular role of the uPA receptor (uPAR) is well characterized with its participation in cell migration and extracellular matrix (ECM) degradation. Over-expression of uPAR in cancer has been demonstrated in many studies and is considered an attractive target for anticancer agents. We and others have down-regulated uPAR expression in an attempt to inhibit cancer metastasis based on its molecular role. Uniquely, uPAR which is a glycosyl phosphatidylinositol anchored protein is not only bound to the cell surface but also has a soluble form, suPAR. There is now accumulated clinical and experimental evidence supporting the significant role of uPAR and its soluble counterpart in a number of solid cancers. The expression of uPAR can be associated with tumor cells or stromal cells or both. Differences observed in the expression of uPAR using immunohistochemistry (IHC) are likely explained by the use of different antibodies and techniques rather than true cellular differences and are reviewed here. This review summarizes the clinical relevance of uPAR and its soluble form in the prognosis and diagnosis of different cancers.

The plasma level of soluble urokinase receptor is elevated in patients with Streptococcus pneumoniae bacteraemia and predicts mortality

This multicentre prospective study was conducted to investigate whether the level of the soluble form of urokinase-type plasminogen activator receptor (suPAR) is elevated during pneumococcal bacteraemia and is of predictive value in the early stage of the disease. Plasma levels of suPAR were increased significantly (median 5.5; range 2.4-21.0 ng/mL) in 141 patients with pneumococcal bacteraemia, compared to 31 healthy controls (median 2.6, range 1.5-4.0 ng/mL, p 0.001). Furthermore, suPAR levels were elevated significantly in patients who died from the infection (n = 24) compared to survivors (n = 117; p < 0.001). No correlation was found between suPAR levels and C-reactive protein. In univariate logistic regression analysis, hypotension, renal failure, cerebral symptoms and high serum concentrations of protein YKL-40 and suPAR were associated significantly with mortality (p < 0.05). In multivariate analysis, only suPAR remained a significant predictor of death (mortality rate of 13 for suPAR levels of > 10 ng/mL; 95% CI: 1.1-158). The increase in suPAR levels may reflect increased expression by vascular or inflammatory cells in the setting of pneumococcal sepsis. This plasma protein may be used to identify patients who are severely ill with pneumococcal bacteraemia.

Diagnostic significance of measurement of the receptor for urokinase-type plasminogen activator on granulocytes and in plasma from patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder characterized by the deficiency of all proteins anchored to the membrane by the glycosyl-phosphatidylinositol (GPI) anchor. The receptor for urokinase-type plasminogen activator (uPAR) also is attached to the cell membrane by a GPI anchor, and that soluble uPAR (suPAR) is present in plasma. In the present study, we measured uPAR, CD55, and CD59 on granulocytes by means of flow cytometry and suPAR in plasma by means of immunoradiometric assay. The subjects were 20 patients with PNH, 59 other patients with anemia, and 21 healthy individuals. In patients with PNH, both the mean fluorescence intensity and the positive percentage of fluorescence-activated granulocytes of uPAR, CD55, and CD59 were remarkably decreased, whereas in patients with other forms of anemia, except 2 patients with aplastic anemia, the results were not altered in comparison with those for the healthy individuals. The level of uPAR was reduced to the same extent as were those of CD55 and CD59 on the PNH-affected granulocytes. Some peak shape abnormalities (double peaks, peak tailing, or both) in the histogram of fluorescence intensity were also found in patients with PNH. The suPAR concentration of PNH plasma was 4.04+/-2.47 ng/mL, which was higher than that of the healthy individuals, 1.73+/-0.96 ng/mL (P < .01). The positive percentage of fluorescence-activated granulocytes was inversely associated with the plasma suPAR level in patients with PNH (r = -0.79, P < .01). Our data suggest that measurement of uPAR on granulocytes by means of flow cytometry and of suPAR in plasma by means of immunoradiometric assay are specific techniques for the diagnosis of PNH.