Proteomic screening of a cell line model of esophageal carcinogenesis identifies cathepsin D and aldo-keto reductase 1C2 and 1B10 dysregulation in Barrett's esophagus and esophageal adenocarcinoma

Esophageal adenocarcinoma (EA) incidence is increasing rapidly and is associated with a poor prognosis. Identifying biomarkers of disease development and progression would be invaluable tools to inform clinical practice. Two-dimensional polyacrylamide gel electrophoresis was used to screen 10 esophageal cell lines representing distinct stages in the development of esophageal cancer. Thirty-three proteins were identified by MALDI-TOF-MS which demonstrated differences in expression across the cell lines. Western blotting and qRT-PCR confirmed increased cathepsin D and aldo-keto reductases 1C2 and 11310 expression in metaplastic and dysplastic cell lines. Expression of these proteins was further assessed in esophageal epithelium from patients with nonerosive (NERD) and erosive gastro-esophageal reflux disease, Barrett's esophagus (BE) and EA. When compared with normal epithelium of NERD patients, (i) cathepsin D mRNA levels demonstrated a stepwise increase in expression (p < 0.05) in erosive, metaplastic and EA tissue; (ii) AKR1B10 expression increased (p < 0.05) 3- and 9-fold in erosive and Barrett's epithelium, respectively; and (iii) AKR1C2 levels increased (p < 0.05) in erosive and Barrett's epithelium, but were reduced (p < 0.05) in EA. These proteins may contribute to disease development via effects on apoptosis, transport of bile acids and retinoid metabolism and should be considered as candidates for further mechanistic and clinical investigations.