Although the levels of CHRNA1, CHRNA5, CHRNA6, CHRNA7, CHRNA9, CHRNB1, CHRNB3, and CHRNB4 in ESCC were all significantly higher than that of the normal esophageal tissues (Fig. 2a), results from GSEA indicate that only CHRNA5 and CHRNA7 were associated with CIC properties in ESCC patients (Fig. 2b–i). This evidence concerns the gene CHRNA9 and esophageal squamous cell carcinoma.