CTCF and digestive system neoplasm: An online bioinformatics analysis website, Gene Expression Profiling Interactive Analysis (GEPIA, http://gepia.cancer-pku.cn/) [33], was used to explore the expression of CTCF in The Cancer Genome Atlas (TCGA) database, and the results indicated that CTCF was almost upregulated in all gastrointestinal tumors (Figure 1A).