In addition, the methylation degree of HDAC4, CUGBP2, PTPRN2 and RUNX2 in cluster 1, cluster 2 and cluster 3 was significantly higher than that of cluster 4 and cluster 5, which are involved in regulating the proliferation and invasion of NSCLC (16, 17) (Figures 3D, E). Here, CELF2 is linked to non-small cell lung carcinoma.