Background: The polycomb group genes, Bmi1 and EZH2, function as transcriptional repressors involved in gene silencing. They are involved in the malignant transformation and biological aggressiveness of several human carcinomas. In the present study, we evaluated Bmi1 and EZH2 protein expression in specimens of human non-small cell lung cancers (NSCLCs).

Methods: We conducted an immunohistochemical assessment of 157 surgically resected NSCLCs to evaluate the correlation between Bmi1 and EZH2 expression and various features, including clinical, clinicopathological and biological characteristics.

Results: Normal bronchial epithelia showed abundant expression of Bmi1 and sporadic expression of EZH2. NSCLC patients with high EZH2 expression in tumor cells showed poorer prognosis than those with low EZH2 expression in all pStages (p = 0.001) and in pStage I (p = 0.006). Multivariate analysis showed that high EZH2 expression was a independent unfavorable prognostic factor in pStage I patients (p = 0.048). High EZH2 expression was significantly correlated with non-adenocarcinoma histology (p = 0.001), moderate and poor differentiation (p = 0.001), advanced pT stage (p = 0.02), and high Ki-67 and cyclin E labeling index (p < 0.001). Bmi1 expression, in contrast, was not a significant prognostic factor, and was not correlated with any clinicopathological factors other than early pT stage.

Conclusion: Bmi1 and EZH2 show characteristic and distinctive expression in NSCLCs. High EZH2 expression is correlated with tumor aggressiveness, and may provide a novel prognostic marker for NSCLCs.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4641.