The scatter diagram and paired T-test were utilized to compare the expression of p27 protein in DTCs tissues and adjacent non-cancerous tissues, and the results indicated that the expression level of p27 protein was lower in ESAC (P = 0.0078; Figure 3A), ESCC (P = 0.0002; Figure 3B), GC (P < 0.0001; Figure 3C) and CRC (P < 0.0001; Figure 3D) tissues than in paired non-tumorous tissues. This evidence concerns the gene CDKN1B and esophageal squamous cell carcinoma.