Proteomic analysis of secreted proteins of non-small cell lung cancer.
OBJECTIVE
Secreted proteins from cancer cells may be potential serologic biomarkers of cancer. It's important to globally identify secreted proteins of cancer cells. This study was to identify secreted proteins of lung cancer cells.


METHODS
Proteins in the conditioned medium of non-small cell lung cancer (NSCLC) cell line A549 was collected and the proteome analysis was subsequently performed. Specific protein spots in A549 cells were identified by peptide mass fingerprints using mass spectrometry and through searching database. The expression of identified secreted proteins was detected by reverse transcription-polymerase chain reaction (RT-PCR) in 15 specimens of NSCLC tissue and paired distant lung tissue. Manganese superoxide dismutase (Mn-SOD) activity in serum and conditioned medium was detected by spectrophotometry.


RESULTS
Fourteen secreted proteins were identified, which included peptidyl-prolyl cis-trans isomerase A (PPIA), Mn-SOD, peroxiredoxin 1 (PDX1), phosphatidylethanolamine binding protein (PEBP), glutathione S-transferase P (GSTP1-1), glucose-dependent insulinotropic protein receptor (GIPR), ubiquitin carboxyl-terminal hydrolase isozyme L1 (PGP9.5), alpha enolase (ENO1), dihydrodiol dehydrogenase (DDH), phosphoglycerate mutase 1 (PGAM1), galectin-1 (GAL1). PPIA, DDH, PGAM1, PDX1, PGP9.5, ENO1, and PEBP were overexpressed in cancer tissues. Higher level of Mn-SOD activity was detected in conditioned medium than in control. Serum Mn-SOD activity was significantly higher in NSCLC patients than in healthy controls (P<0.01).


CONCLUSIONS
Multiple secreted proteins of A549 cells were identified in this study and the overexpression of ENO1 and PEBP in NSCLC was revealed for the first time. Mn-SOD is secreted serologic marker of NSCLC. The results presented here would provide clues to identify new serologic biomarkers of NSCLC.
Huang
Ling-Jin
LJ
Department of Cardiothoracic Surgery, Xiangya Hospital, Central South University, Changsha, Hunan, 410008, P. R. China. drhuanglj@yahoo.com.cn
Chen
Sheng-Xi
SX
Luo
Wan-Jun
WJ
Jiang
Hai-He
HH
Zhang
Peng-Fei
PF
Yi
Hong
H
D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D017077:Culture Media, Conditioned; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D049488:Phosphatidylethanolamine Binding Protein / Q000378:metabolism*; D010751:Phosphopyruvate Hydratase / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D040901:Proteomics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013482:Superoxide Dismutase / Q000097:blood; D025521:Tumor Suppressor Proteins / Q000378:metabolism*
D014408:Biomarkers, Tumor; D017077:Culture Media, Conditioned; D004268:DNA-Binding Proteins; D049488:Phosphatidylethanolamine Binding Protein; D025521:Tumor Suppressor Proteins; D013482:Superoxide Dismutase; C095157:ENO1 protein, human; D010751:Phosphopyruvate Hydratase