129P - Procathepsin D as a novel diagnostic marker for malignant pleural effusion of lung cancer

Abstract

Background: Approximately 20% of pleural effusions are due to malignancy, and 50% of these are due to primary lung cancer. However, the etiology of the effusions is often obscure and various diagnostic procedures may be required in order to find their cause. Cathepsin D (CD) as a lysosomal aspartic protease is one of the most important intracellular enzymes considered to be substantially involved in tumor invasion. Procathespin D (pCD) is overexpressed and secreted by cells of various tumor types. The aim of this study is to evaluate the serum and pleural fluid levels of CD and pCD as a differential diagnostic tool in patients with pleural effusion caused by malignant or benign process. Methods: Patients and pleural fluid collection: The present study included 85 patients (40 patients with lung cancer, 30 patients with tuberculosis, 10 patients with parapneumonic effusion, 5 patients with transudate effusion) who underwent thoracentesis and pleural biopsy. Clinical and pathology data, including tumor type were acquired for all patients. Analysis of CD and pCD: Amounts of CD in the pleural fluid and serum were determined with a cathepsin D ELISA kit and pCD with a sandwich ELISA method. Results: Concentration of pleural CD was not significantly different in patients with malignant pleural effusion compared with non malignant effusion (mean 13.34 vs. 16.72 ng/ml; p > 0.05), and also the concentration of serum CD was not significantly different (mean 41.34 vs. 36.52 ng/ml; p > 0.05). Plasma pCD of malignant pleural effusion and non malignant effusion were 42.03 ng/ml and 38.59 ng/ml, respectively (p > 0.05) but pleural pCD of malignant pleural effusion and non malignant effusion were 84.24 ng/ml and 33.82 ng/ml, respectively with significance (p < 0.05). Conclusions: In this small cohort, the pleural pCD of lung cancer patients showed elevated levels compared with that of non malignant effusion. The pleural fluid levels of pCD could be a diagnostic marker of malignant effusion with lung cancer and further prospective studies might shed more light on the value of CD and pCD in the diagnostics of pleural effusion. Legal entity responsible for the study: Chang Youl Lee Funding: Hallym University Medical Center Disclosure: All authors have declared no conflicts of interest.