Several studies that investigated the activity and the biological role of NNMT, found high NNMT mRNA and protein levels and high catalytic activity in different cancer cell lines, including LSCC cell lines [34], ESCC cell lines EC9706 and TE1 [13], and PTC cell line BHP 2-7 [39]. The gene discussed is NNMT; the disease is esophageal squamous cell carcinoma.