However, by analyzing the methylation status of CHRNA7 gene in two independent ESCC microarray datasets (GSE20123 and GSE52826), we found that DNA methylation of CHRNA7 promoter in ESCC cells was significantly (P < 0.001 and P < 0.01, respectively) lower than that in the normal tissues (Supplementary Fig. 4b). Here, CHRNA7 is linked to esophageal squamous cell carcinoma.