Expression of glycoprotein 90K in human malignant pleural mesothelioma: correlation with patient survival

The expression of the tumour-associated glycoprotein 90K in patients with malignant pleural mesothelioma (MM) has not been described. This study used enzyme-linked immunoassay (ELISA) to measure 90K in pleural effusions (PEs) and sera from patients with MM (n=28), lung cancer (LC) (n=14) and benign pleural disease (BPD) (n=15). Immunohistochemistry was used to investigate 90K expression in MM and LC tissue sections. The expression of 90K was further evaluated in vitro by ELISA and western blot analysis of conditioned media and cellular extracts of MM, LC and normal human mesothelial (NHM) cell cultures. Finally, the relationships between 90K expression in MM and patient age and survival were studied. The mean 90K level was significantly higher (p<0.05) in PEs of MM patients (11.0+/-6.6 microg/ml) than in LC (6.1+/-3.2 microg/ml) or BPD (6.2+/-5.0 microg/ml) patients. Immunohistochemistry showed a positive reaction for 90K in MM biopsy sections and positive staining limited to inflammatory infiltrates in LC sections. The level of 90K was significantly higher in cell culture media of MM than of LC or NHM (p<0.001). Bands representing proteins with molecular weight of approximately 90 kDa were detected by western blot in MM cellular extracts. An inverse correlation between PE 90K levels and MM patient age (r=-0.45; p=0.017) and a positive correlation between serum 90K levels and MM patient survival (r=0.62; p=0.006) were detected by linear regression analysis. Kaplan-Meier univariate analysis showed increased survival probability for MM patients with serum 90K level >7.3 microg/ml (log rank, p<0.05). This is the first report in MM of the expression of 90K and of its potential diagnostic and prognostic application.