Membrane proteomic analysis comparing squamous cell lung cancer tissue and tumour-adjacent normal tissue.

Lung cancer is the leading cause of cancer-related deaths worldwide. Squamous cell carcinoma is one of the predominant histological subtypes of lung cancer. Detecting lung cancer at an early stage is essential for successful therapy and increasing survival. There are still no satisfactory biomarkers for the early detection of lung cancer. In this study, tumour tissue paired with tumour-adjacent normal bronchial epithelial tissue was obtained from patients with squamous cell lung carcinoma without metastasis. The proteins extracted from the cell membrane were separated by two-dimensional polyacrylamide gel electrophoresis (2-DE) and were analysed with the Image Master two-dimensional platinum software. Twenty-five significantly different protein spots were selected and identified with matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). A total of 19 proteins were successfully identified. Twelve proteins were up-regulated, and seven proteins were down-regulated in the cancerous tissue compared with the tumour-adjacent normal tissue. One up-regulated protein and one down-regulated protein in squamous cell lung carcinoma were verified by Western blot analysis and RT-PCR; the results were consistent with the 2-DE analysis. In conclusion, membrane proteomics identified a number of candidate biomarker proteins that were differentially expressed between squamous cell lung cancer tissue and adjacent normal tissue. These biomarker candidates have the potential to elucidate the underlying pathogenesis of squamous cell lung cancer.