A high-quality secretome of A549 cells aided the discovery of C4b-binding protein as a novel serum biomarker for non-small cell lung cancer

J Proteomics. 2011 Apr 1;74(4):528-38. doi: 10.1016/j.jprot.2011.01.011. Epub 2011 Jan 22.


Cancer secretomes are a promising source for biomarker discovery. The analysis of cancer secretomes still faces some difficulties mainly related to the intracellular contamination, which hinders the qualification and follow-up validations. This study aimed to establish a high-quality secretome of A549 cells by using the cellular proteome as a reference and to test the merits of this refined secretome for biomarker discovery for non-small cell lung cancer (NSCLC). Using one-dimensional gel electrophoresis followed by liquid-chromatography tandem mass spectrometry, we comprehensively investigated the secretome and the concurrent cellular proteome of A549 cells. A high-quality secretome consisting of 382 proteins was refined from 889 initial secretory proteins. More than 85.3% of proteins were annotated as secreted and 76.8% as extracellular or membrane-bound. The discriminative power of the lung-cancer associated secretome was confirmed by gene expression and serum proteomic data. The elevated level of C4b-binding Protein (C4BP) in NSCLC blood was verified by enzyme-linked immunosorbent assays (ELISA, p = 6.07e-6). Moreover, the serum C4BP level in 89 patients showed a strong association with the clinical staging of NSCLC. Our reference-experiment-driven strategy is simple and widely applicable, and may facilitate the identification of novel promising biomarkers of lung cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Biomarkers, Tumor / analysis
  • Biomarkers, Tumor / blood
  • Biomarkers, Tumor / metabolism
  • Carcinoma, Non-Small-Cell Lung / blood*
  • Carcinoma, Non-Small-Cell Lung / diagnosis
  • Carcinoma, Non-Small-Cell Lung / metabolism*
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Line, Tumor
  • Cluster Analysis
  • Complement C4b-Binding Protein / isolation & purification
  • Complement C4b-Binding Protein / metabolism
  • Complement C4b-Binding Protein / physiology*
  • Female
  • Humans
  • Lung Neoplasms / blood*
  • Lung Neoplasms / diagnosis
  • Lung Neoplasms / metabolism*
  • Lung Neoplasms / pathology
  • Male
  • Middle Aged
  • Models, Biological
  • Neoplasm Staging
  • Proteome / analysis
  • Proteome / metabolism*
  • Quality Control
  • Validation Studies as Topic


  • Biomarkers, Tumor
  • Complement C4b-Binding Protein
  • Proteome