The pleural effusion proteome has been found containing information that directly reflects pathophysiological status and represents a potential diagnostic value for pulmonary diseases. However, the variability in protein composition between malignant and benign effusions is not well understood. Herein, we investigated the changes of proteins in pleural effusions from lung adenocarcinoma and benign inflammatory disease (pneumonia and tuberculosis) patients by two-dimensional difference gel electrophoresis (2D-DIGE). Twenty-eight protein spots displayed significantly different expression levels were positively identified by MALDI-TOF-MS representing 16 unique proteins. Five identified protein candidates were further validated and analyzed in effusions, sera or tissues. Among them, hemopexin, fibrinogen gamma and transthyretin (TTR) were up-regulated in cancer samples. The effusion concentration of serum amyloid P component (SAP) was significantly lower in lung cancer patients than in benign inflammatory patients, but no differences were found in sera samples. Moreover, a Jumonji C (JmjC)-domain-containing protein, JMJD5, was observed to be down-regulated in malignant effusions, lung cancer tissues and cancer cells. These results shed light on the altered pleural effusion proteins as a useful and important complement to plasma or other routine clinical tests for pulmonary disease diagnosis.
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