Prognostic significance of MCM7 expression in the bronchial brushings of patients with non-small cell lung cancer (NSCLC)

Purpose To identify potential biomarkers for the prognosis of non-small cell lung cancer (NSCLC) patients by using bronchial brushing specimens. Methods The expression of MCM7, Ki67 and EGFR was evaluated in 494 NSCLC tissues and 174 bronchial brushings using immunohistochemical and immunocytochemical techniques. Associations between protein expression and clinico-pathologic parameters were assessed, and the impact on overall survival (OS) was analyzed. Results High expression of MCM7, Ki67 and EGFR was detected in 33.3%, 23.5% and 12.7% of tissues and in 52.4%, 52.7% and 20.6% of bronchial brushings, respectively. Expression of MCM7 and Ki67 was associated with squamous cell carcinoma (SCC) in both tissues and bronchial brushings (MCM7: P=0.0007, 0.00003; Ki67: P<0.00001, 0.00001). Overexpression of MCM7 in tumor tissues was detected more frequently in poorly differentiated tumors (P=0.0120) and non-bronchioloalveolar carcinomas (non-BACs) (P=0.0238). EGFR overexpression was observed in tissues of larger tumors (P=0.00004) and in bronchial brushings at later stage (P=0.0262). Kaplan–Meier curves indicated that patients with overexpression of MCM7 or Ki67 had a poorer OS compared to those with low expression for all stages (P<0.00001, 0.0233) and early-stages (P<0.00001, 0.0032). In particular, the patients with MCM7 overexpression in bronchial brushings had a poorer prognosis (P=0.0045). Multivariate Cox regression analysis showed that MCM7 was an independent prognostic indicator both in tissue samples and bronchial brushings. Conclusions Our data suggest that MCM7 and Ki67 in tumor tissues may be potential markers of a poor prognosis for NSCLC patients. MCM7 in bronchial brushings also showed an independent prognostic value, which may be useful when biopsies are unavailable.