We then treated two human ESCC cell lines KYSE270 and TE1 with different concentrations (0.1, 1, and 10 μM) of nicotine, and found that treatment with nicotine decreased the levels of both cytokeratin 14 (CK14) and CK18 in a dose-dependent manner, drastically at 10 μM (Fig. 1b). The gene discussed is KRT18; the disease is esophageal squamous cell carcinoma.