EZH2 protein expression associates with the early pathogenesis, tumor progression, and prognosis of non-small cell lung carcinoma

Purpose: Enhancer of zeste homolog 2 (EZH2) promotes carcinogenesis by epigenetically silencing tumor suppressor genes. We studied EZH2 expression by immunohistochemistry in a large series of non-small cell lung carcinomas (NSCLC) in association with tumor characteristics and patient outcomes. Experimental Design: EZH2 immunohistochemistry expression was analyzed in 265 normal and premalignant bronchial epithelia, 541 primary NSCLCs [221 squamous cell carcinomas (SCC) and 320 adenocarcinomas] and 36 NSCLCs with paired brain metastases. An independent set of 91 adenocarcinomas was also examined. EZH2 expression was statistically correlated with clinico-pathological information, and EGFR/KRAS mutation status. Results: EZH2 expression was significantly(P< 0.0001) higherin SCCs compared with adenocarcinomas andin brain metastasis relative to matched primary tumors (P=0.0013). EZH2 expression was significantly (P < 0.0001) elevated in bronchial preneoplastic lesions with increasing severity. In adenocarcinomas, higher EZH2 expression significantly correlated with younger age, cigarette smoking, and higher TNM stage (P= 0.02to P < 0.0001). Higher EZH2 expression inadenocarcinoma was associated with worse recurrencefree survival (RFS; P = 0.025; HR = 1.54) and overall survival (OS; P = 0.0002; HR = 1.96). Furthermore, lung adenocarcinomas with low EZH2 levels and high expression ofthe lineage-specific transcription factor, TTF-1, exhibited significantly improved RFS(P=0.009;HR=0.51) and OS (P =0.0011; HR = 0.45), which was confirmed in the independent set of 91 adenocarcinomas. Conclusion: In lung, EZH2 expression is involved in early pathogenesis of SCC and correlates with a more aggressive tumor behavior of adenocarcinoma. When EZH2 and TTF-1 expressions are considered together, they serve as a prognostic marker in patients with surgically resected lung adenocarcinomas. Clin