CTCF and neoplasm: Although the methylation levels in tumors were higher in CpG sites within CGI‐3 than in those within CGI‐4, the average β‐value in non‐tumor tissues was extremely and specifically low at cg15126544 and showed the largest difference of average β‐value between tumor and non‐tumor tissues at this site (Figure 1B and Table S7), which is localized within the CCCTC‐binding factor (CTCF)‐binding site of GAD1. Similar results were observed in the Level 3 Infinium Human Methylation 450K data of 29 LADC tumors and paired non‐tumor tissues from TCGA dataset (Figure S1).