Prognostic impact of S100A9 overexpression in non-small cell lung cancer.

S100 proteins have been implicated in the progression and metastasis of several cancers. Among the S100 family, S100A9 is reportedly expressed in non-small cell lung cancer (NSCLC), though the clinical significance and prognostic value of S100A9 expression in NSCLC remains unclear. The aim of the present study was to examine the relationship between S100A9 expression and prognosis in NSCLC patients. S100A9 expression was evaluated by immunohistochemical staining. Seventy patients with NSCLC who had undergone lung resection were enrolled in the study. Overexpression of S100A9 was observed in 38 (54.3%) patients. Kaplan-Meier analysis showed that, following surgery, patients overexpressing S100A9 had a significantly lower 5-year overall survival rate than patients with weak or no expression of S100A9 (P=0.005). This finding was also observed in pathological stage IA patients (P=0.03). Multivariate Cox regression analysis revealed overexpression of S100A9 to be an independent factor predictive of poor disease outcome (hazard ratio, 0.3; 95% confidence interval, 0.1-0.8; P=0.02). Our results suggest that overexpression of S100A9 is associated with a poor prognosis among NSCLC patients and could serve as a marker identifying patients who are at high risk, even at an early pathological stage.