CA9 and esophageal squamous cell carcinoma: We also identified CAIX as a possible target of alcohol exposure in ESCC, as we measured increases in the percentages of CAIX(+) epithelial cells expressing CAIX protein in the esophagi of mice in the V.C./EtOH, 4-NQO/Untr., and 4-NQO/EtOH groups compared to the V.C./Untr.