Epigenetic modifications in KDM lysine demethylases associate with survival of early-stage NSCLC

Abstract

Background: KDM lysine demethylase family members are related to lung cancer clinical outcomes and are potential biomarkers for chemotherapeutics. However, little is known about epigenetic alterations in KDM genes and their roles in lung cancer survival. Methods: Tumor tissue samples of 1230 early-stage non-small cell lung cancer (NSCLC) patients were collected from the five independent cohorts. The 393 methylation sites in KDM genes were extracted from epigenome-wide datasets and analyzed by weighted random forest (Ranger) in discovery phase and validation dataset, respectively. The variable importance scores (VIS) for the sites in top 5% of both discovery and validation sets were carried forward for Cox regression to further evaluate the association with patient’s overall survival. TCGA transcriptomic data were used to evaluate the correlation with the corresponding DNA methylation. Results: DNA methylation at sites cg11637544 in KDM2A and cg26662347 in KDM1A were in the top 5% of VIS in both discovery phase and validation for squamous cell carcinomas (SCC), which were also significantly associated with SCC survival (HRcg11637544 = 1.32, 95%CI, 1.16–1.50, P = 1.1 × 10−4; HRcg26662347 = 1.88, 95%CI, 1.37–2.60, P = 3.7 × 10−3), and correlated with corresponding gene expression (cg11637544 for KDM2A, P = 1.3 × 10−10; cg26662347 for KDM1A P = 1.5 × 10−5). In addition, by using flexible criteria for Ranger analysis followed by survival classification tree analysis, we identified four clusters for adenocarcinomas and five clusters for squamous cell carcinomas which showed a considerable difference of clinical outcomes with statistical significance. Conclusions: These findings highlight the association between somatic DNA methylation in KDM genes and early-stage NSCLC patient survival, which may reveal potential epigenetic therapeutic targets. Electronic supplementary material The online version of this article (10.1186/s13148-018-0474-3) contains supplementary material, which is available to authorized users.