Proteomics-based Identification of Proapoptotic Caspase Adapter Protein 
as A Novel Serum Marker of Non-small Cell Lung Cancer

Abstract

Background and objective Early diagnosis and treatment of lung cancer contribute to a patient’s prolonged survival. Proteomics and tissue culture were used to screen potential serum markers of lung cancer. Methods The differential proteomic technique and matrix-assisted laser desorption/ionization-time of flight mass spectrometry were used to identify overexpressed proteins from cultured tumor tissues in a conditioned medium. Paired lung tissues in a conditioned medium were used as the control group. Overexpressed proapoptotic caspase adaptor protein (PACAP) was identified using Western blot and enzyme-linked immunosorbent assay (ELISA). Results The expression of nineteen protein spots exhibited a twofold increase compared with that in the control group. Fourteen of which were identified, including the distinctly overexpressed PACAP. Western blot analysis revealed a high level of PACAP in the lung adenocarcinoma in both tissue culture media and patients’ serum. Overexpressed PACAP was also detected in the serum of non-small cell lung cancer patients via ELISA compared with that in the serum of small cell lung cancer patients, benign lung tumor patients, and healthy individuals (P<0.05). Conclusion PACAP is a potential serum marker of non-small cell lung cancer.

Keywords

• Lung neoplasms
• Serum marker
• Proapoptotic caspase adaptor protein