title: Effect of celecoxib on cyclooxygenase-2 expression and possible variants in a patient with Barrett's esophagus.
abstract: Cyclooxygenase-2 (COX-2) expression is increased in metaplastic and dysplastic Barrett's esophageal epithelium and it is thought that selective COX-2 inhibitors could offer hope as chemoprevention therapy. The aim of the study was to investigate the in vivo effect of celecoxib on COX-2 expression in patients with Barrett's esophagus and no recent history of non-steroidal anti-inflammatory drug use. Endoscopic mucosal biopsy specimens were collected at baseline and after 28 days of therapy in a patient treated with celecoxib 200 mg twice daily. Samples were analyzed for COX-2 expression by immunoblot analysis with chemiluminescence detection. COX-2 expression was found to decline 20% and 44% at two different biopsy sites compared to the baseline sample. Longer exposures revealed a number of previously unidentified proteins above and below the 67 kDa COX-2 protein including 38 kDa and 45 kDa proteins which were present only at study completion consistent with up-regulation after celecoxib therapy. Further investigations of the 38 kDa and 45 kDa proteins were undertaken using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) with immunoblot and MALDI-TOF (matrix assisted laser desorption ionization - time of flight) analysis but no matches were found and results were inconclusive. Unmatched masses from MALDI-TOF peptide mass fingerprinting were compared with human COX-2 (67 kDa) and COX-2b (39 kDa) using unspecific cleavage. Peptide sequence homology with COX-2 and COX-2b was found for a length of 19 amino acids. Based on immunodetection, molecular weight and equivical MALDI-TOF results, one of these up-regulated proteins may be COX-2b.
authors.affiliation: School of Pharmacy, University of Tasmania, and Royal Hobart Hospital, Tasmania, Australia. glenn.jacobson@utas.edu.au
authors.forename: G A
authors.initials: GA
authors.lastname: Jacobson
authors.forename: C
authors.initials: C
authors.lastname: Narkowicz
authors.forename: R
authors.initials: R
authors.lastname: Lord
authors.forename: B-J
authors.initials: BJ
authors.lastname: Howard
authors.forename: S
authors.initials: S
authors.lastname: Chung
mesh_terms: D000328:Adult; D001471:Barrett Esophagus / Q000378:metabolism* / Q000473:pathology; D000068579:Celecoxib; D051546:Cyclooxygenase 2 / Q000187:drug effects* / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D011720:Pyrazoles / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: D016861:Cyclooxygenase Inhibitors; D011720:Pyrazoles; D013449:Sulfonamides; D051546:Cyclooxygenase 2; D000068579:Celecoxib