Proteomics-based identification of secreted protein dihydrodiol dehydrogenase as a novel serum markers of non-small cell lung cancer

Summary Identification of secreted proteins of lung cancer could provide new candidates of serum biomarkers for cancer diagnosis and prognosis evaluation. In this study, non-small cell lung cancer (NSCLC) cell line A549 was cultured. Proteins in the conditioned medium of A549 were recovered and the proteome analysis was subsequently performed. Secreted proteins of A549 were identified using mass spectrometry and database search. Fourteen human proteins were identified, including peptidyl–prolyl cis – trans isomerase A, manganese superoxide dismutase, peroxiredoxin 1, phosphatidylethanolamine-binding protein, glutathione S -transferase P, PGP9.5, alpha enolase, phosphoglycerate mutase 1, galectin-1 and dihydrodiol dehydrogenase (DDH). DDH was selected for further analysis using RT-PCR, immunoblotting, immunohistochemical staining and ELISA in NSCLC patients. Compared with normal lung tissues, higher DDH mRNA and protein expression level were found in 15 NSCLC cancer tissues ( p n  = 64) than nonmalignant lung tumor ( n  = 20) and healthy controls ( n  = 20) ( p