The results showed that the level of DNA methylation was negatively related to the decreased CCNE1 and E2F1 transcription in 370 lung squamous cell carcinoma tissues (p < 0.05, Supplementary Figures S3A and S4A) and 456 lung adenocarcinoma tissues (p < 0.05, Supplementary Figures S3B and S4B). Here, CCNE1 is linked to squamous cell lung carcinoma.