The mRNA expression levels of EN2 were examined in three ESCC cell lines, namely Eca109, Kyse150 and TE-1, as well as the SHEE cell line, which is an immortalized epithelial cell line derived from the fetal esophageal epithelium induced by HPV 18 E6E7 AAV (Shen et al., 2003). The gene discussed is EN2; the disease is esophageal squamous cell carcinoma.