Background: Lung cancer is the leading cause of cancer-related death worldwide. While targeted therapy, such as tyrosine kinase inhibitors (TKIs), has been used against the non small cell lung cancers (NSCLCs) patients with epidermal growth factor receptor (EGFR) mutation, not all the patients received benefit from TKIs. Epigenetic alterations have been recognized as one of the important mechanism of NSCLCs. The aim of this study is to clarify the significance of DNA methylation, especially the clinical impacts of CpG island methylator phenotype (CIMP), in NSCLCs. Methods: Using methylated CpG island amplification-microarray (MCAM), a genome-wide DNA methylation analysis, 41 lung adenocarcinomas (AdCas) were analyzed. DNA methylation of newly identified genes from MCAM analysis was further examined in another cohort of 86 AdCas with bisulfate pyrosequencing method. Results: Unsupervised hierarchical cluster analysis revealed that DNA methylation was extensively accumulated in one subgroup (n=4, 9.8%), which may represent CIMP tumors (651 genes vs. 354 genes, P=0.0004). DNA methylation status of newly identified 7 CIMP markers revealed that 8 (9.3%), 12 (14%), and 66 (76.7%) were classified into CIMP-high, CIMP-low, and CIMP-negative tumors, respectively. CIMP-high tumors showed no EGFR mutations and frequent exposure to smoking. In addition, these tumors had worse prognosis than the other tumors (P=0.035), suggesting that CIMP-high tumors have characteristic clinical features, which may represent an alternative mechanism to the EGFR mutation. Treatments of NSCLC cell lines showed that CIMP positive AdCa cell lines are sensitive to DNA demethylating agent regardless of EGFR status. Conclusions: Our data suggest that CIMP in AdCas appears to be a unique subgroup, which has distinguished clinical traits from the other AdCas. Applying DNA demethylating agent to CIMP-high tumors might be a new strategy for the treatment of NSCLCs without EGFR mutation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 61. doi:10.1158/1538-7445.AM2011-61