Barrett Esophagus/drug therapy; Esophageal Neoplasms/drug therapy; Gastrins/biosynthesis; Precancerous Conditions/drug therapy; Proton Pump Inhibitors/therapeutic use; Adult; Aged; Barrett Esophagus/metabolism; Barrett Esophagus/pathology; Cell Movement/drug effects; Cell Proliferation/drug effects; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay/methods; Esophageal Neoplasms/metabolism; Esophageal Neoplasms/pathology; Esophagus/metabolism; Female; Gastric Mucosa/metabolism; Gastrins/genetics; Gastrins/pharmacology; Gene Expression; Humans; Male; Middle Aged; Precancerous Conditions/metabolism; Precancerous Conditions/pathology; Proton Pump Inhibitors/adverse effects; RNA, Messenger/genetics; Receptor, Cholecystokinin B/biosynthesis; Receptor, Cholecystokinin B/genetics; Reverse Transcriptase Polymerase Chain Reaction/methods; Tumor Cells, Cultured