High expression of Y-box-binding protein 1 correlates with poor prognosis and early recurrence in patients with small invasive lung adenocarcinoma

BACKGROUND Prognosis of small (≤2 cm) invasive lung adenocarcinoma remains poor, and identification of high-risk individuals from the patients after complete surgical resection of lung adenocarcinoma has become an urgent problem. YBX1 has been reported to be able to predict prognosis in many cancers (except lung adenocarcinoma) that are independent of TNM (tumor, nodes, metastases) staging, especially small invasive lung adenocarcinoma. Therefore, we examined the significance of YBX1 expression on prognosis and recurrence in patients with small invasive lung adenocarcinoma. MATERIAL AND METHODS A total of 75 patients with small invasive lung adenocarcinoma after complete resection were enrolled from January 2008 to December 2010. Immunohistochemical staining was used to detect the expression of YBX1, and receiver operating characteristic curve analysis was performed to precisely assess the overall expression of YBX1. Meanwhile, primary lesions were identified based on the International Association for the Study of Lung Cancer, the American Thoracic Society, and the European Respiratory Society's classification of lung adenocarcinoma. The effect of different clinicopathological factors on patients' survival was examined. Furthermore, Western blot analysis was used to show the expression of YBX1 in vitro. RESULTS Sensitivity and specificity of YBX1 for detecting small invasive lung adenocarcinoma from normal surrounding tissue were 66.7% and 74.7% (area under the receiver operating characteristic curve =0.731; P<0.001), respectively. High YBX1 expression was detected in 31 (41.3%) patients, and in A549, H322, Hcc827, and H1299 lung adenocarcinoma cells but not in HLF cells. In addition to sex, age, tumor size, TNM staging, pleural invasion, and lymph node metastasis, the expression of YBX1 was associated with the International Association for the Study of Lung Cancer, the American Thoracic Society, and the European Respiratory Society pathological grade risk (P=0.026) and differentiation (P=0.009). The patients with low YBX1 expression lived longer than those with high expression (5-year overall survival: 52.3% vs 79.0%; P=0.039) and showed fewer recurrences (P=0.024). In multivariate analyses, high YBX1 expression (odds ratio =2.737; 95% confidence interval: 1.058-7.082; P=0.038) was shown as an independent risk factor of overall survival but not of disease-free survival (odds ratio =1.696; 95% confidence interval: 0.616-4.673; P=0.307). CONCLUSION YBX1 is an important predictor for the prognosis in patients with small invasive lung adenocarcinoma after complete resection.