Proteomic Analysis of Human Small Cell Lung Cancer Tissues: Up-Regulation of Coactosin-Like Protein-1

Small cell lung cancer (SCLC) is the leading cause of cancer death, with a high propensity for aggressiveness and metastasis even in an early stage. Thus, identification of biomarkers as early diagnostics and treatment is needed. In this study, we investigated differentially regulated proteins between human SCLC tissues and normal bronchial epithelium by proteomic analysis using two-dimensional electrophoresis (2-DE) and MALDI-TOF mass spectrometry. Seven proteins and protein isoforms, including, γ-actin, tubulin α-1B, laminin B1, coactosin-like protein-1 (COTL-1), ubiquitin carboxyl-terminal esterase L1, ubiquitin-conjugating enzyme E2-25K, and carbonic anhydrase 1, were up-regulated more than 2 fold in SCLC tissues. In particular, up-regulated COTL-1 expression was validated by Western blot analysis, immunohistochemistry, and reverse transcription quantitative polymerase chain reaction (RT-qPCR). Moreover, most SCLC tissues (93%; 28/30) were COTL-1-positive in immunohistochemistry, whereas only 16% (10/64) of nonsmall cell lung cancer (NSLC) tissues were. Taken together, this SCLC proteomic data may help in establishing a human SCLC proteome database. COTL-1 may be a biomarker or a therapeutic target in SCLC patients.