Comparative proteome analysis of human lung squamous carcinoma tissue

Abstract

Objective: To establish the two-dimensional electrophoresis profiles with high resolution and reproducibility from human lung squamous carcinoma tissue and paired normal tumor-adjacent bronchial epithelial tissue, and to identify differential expression tumor-associated proteins by using proteome analysis. Methods: Comparative proteome analysis with 20 human lung squamous carcinoma tissues and the paired normal bronchial epithelial tissues adjacent to tumors was carried out. The total proteins of human lung squamous carcinoma tissue and paired normal tumor-adjacent bronchial epithelial tissue were separated by means of immobilized pH gradient-based two-dimensional gel electrophoresis (2-DE) and silver staining. The differential expression proteins were analyzed and then identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Results: (1) Well-resolved, reproducible 2-DE patterns of human lung squamous carcinoma and adjacent normal bronchial epithelial tissues were obtained. For tumor tissue, average spots of 3 gels were 1567±46, and 1436±54 spots were matched with an average matching rate of 91.6%. For control, average spots of 3 gels were 1349±58, and 1228±35 spots were matched with an average matching rate of 91.03%. The average position deviation of matched spots was 0.924±0.128 mm in IEF direction, and 1.022±0.205 mm in SDS-PAGE direction; (2) A total of 1178±56 spots were matched between the electrophoretic maps of 20 human lung squamous carcinoma tissues and paired normal tumor-adjacent bronchial epithelial tissues. Seventy-six differentially expressed proteins were screened; (3) Sixty-eight differential proteins were identified by PMF, some proteins were the products of oncogenes, and others involved in the regulation of cell cycle and signal transduction; (4) In order to validate the reliability of the identified results, the expression of 3 proteins mdm2, c-jun and EGFR, which was correlated with lung squamous carcinoma, was detected by immunohistochemical staining and Western blot analysis. The results revealed that mdm2, c-jun and EGFR were up-regulated in lung squamous carcinomas, whereas they were down-regulated in adjacent normal bronchial epithelial tissues, normal lung tissues and inflammatory pseudotumor, which was consistent with our proteome analysis results. Conclusion: The well-resolved, reproducible 2-DE patterns of human lung squamous carcinoma and adjacent normal bronchial epithelial tissues were established and 68 differential proteins were characterized by applying comparative proteome analysis successfully. These results will provide scientific foundation for screening the molecular biomarker used to diagnose and treat lung squamous carcinoma, as well as to improve the patient’s prognosis and provide new clue for the research of lung squamous carcinogenic mechanism.