Overexpression of stathmin 1 is a poor prognostic biomarker in non-small cell lung cancer

Stathmin 1 (STMN1), a major microtubule-depolymerizing protein, is involved in cell cycle progression and cell motility. However, the clinical significance of STMN1 expression in non-small cell lung cancer (NSCLC) has not been determined. The expression pattern of STMN1 mRNA was analyzed by quantitative real-time PCR (qRT-PCR) in 37 cases of NSCLC and in the corresponding non-tumor tissue samples. Furthermore, immunohistochemistry was performed to detect STMN1 protein expression in 113 primary NSCLC tissues. The functional role of STMN1 in lung cancer cell lines was evaluated by small interfering RNA-mediated depletion followed by analyses of cell proliferation and invasion. We found that the STMN1 mRNA and protein levels in NSCLC tissues were significantly higher than those in the corresponding non-tumor tissues (P<0.001). In addition, increased STMN1 expression was correlated with poor tumor differentiation (P<0.001), large tumor size (P=0.022), advanced N stage (P=0.033), and advanced TNM stage (P<0.001). Kaplan-Meier analysis indicates that NSCLC patients with higher STMN1 expression showed significantly worse survival. Moreover, multivariate analysis indicates that higher STMN1 protein expression was an independent prognostic factor of disease-specific survival (HR 2.247, 95%CI 1.320-3.825, P=0.003). Finally, the knockdown of STMN1 in lung cancer cells resulted in a decrease in cellular proliferation and invasion. Our findings suggest that STMN1 may have an important role in NSCLC progression and could serve as a potential prognostic marker for patients with NSCLC.