Prognostic value of Bmi-1 oncoprotein expression in non-small cell lung cancer

Background: In our prior study, Bmi-1 was elevated in non-small cell lung cancer (NSCLC) and took an important role in the early stage of progression. However, the clinical significance of Bmi-1 in NSCLC was uncertain. The aim of this study was to illuminate the relationship between Bmi-1, clinical variables and the prognosis of patients with NSCLC. Methods: Real-time PCR was used to examine the expression of Bmi-1 mRNA in 23 paired NSCLC and the adjacent normal tissues. The expression of Bmi-1 protein in 128 specimens of NSCLC was determined by immunohistochemistry assay. Statistical analyses were performed to evaluate the association between the expression of Bmi-1, clinicopathologic features and prognosis. Results: Up-regulated expression of Bmi-1 mRNA was observed in 91.3% of NSCLC (P < 0.0001). The level of Bmi-1 was positively correlated with T stage (P = 0.019), and the 5-year overall survival of patients with higher Bmi-1 level was lower than that of patients with lower Bmi-1 level without statistical significance (P = 0.189). Histological classification and smoking status were not related to prognosis (P = 0.166, 0.615). For patients with adenocarcinoma, lower level of Bmi-1 was related to good prognosis (P = 0.033), and in multivariate analysis, metastasis, T stage and lymph node involvement were independent prognostic factors (P = 0.001, 0.044, 0.013). Conclusions: Expression of Bmi-1 mRNA was higher in NSCLC than in the adjacent normal tissues. The detection of Bmi-1 protein expression is potentially useful in prognostic evaluation of lung adenocarcinoma.