Downregulation of p63 upon exposure to bile salts and acid in normal and cancer esophageal cells in culture.
p63 is a member of the p53 protein family that regulates differentiation and morphogenesis in epithelial tissues and is required for the formation of squamous epithelia. Barrett's mucosa is a glandular metaplasia of the squamous epithelium that develops in the lower esophagus in the context of chronic, gastroesophageal reflux and is considered as a precursor for adenocarcinoma. Normal or squamous cancer esophageal cells were exposed to deoxycholic acid (DCA, 50, 100, or 200 microM) and chenodeoxycholic and taurochenodeoxycholic acid at pH 5. p63 and cyclooxygenase-2 (COX-2) expressions were studied by Western blot and RT-PCR. DCA exposure at pH 5 led to a spectacular decrease in the levels of all isoforms of the p63 proteins. This decrease was observed within minutes of exposure, with a synergistic effect between DCA and acid. Within the same time frame, levels of p63 mRNA were relatively unaffected, whereas levels of COX-2, a marker of stress responses often induced in Barrett's mucosa, were increased. Similar results were obtained with chenodeoxycholic acid but not its taurine conjugate at pH 5. Proteasome inhibition by lactacystin or MG-132 partially blocked the decrease in p63, suggesting a posttranslational degradation mechanism. These results show that combined exposure to bile salt and acid downregulates a critical regulator of squamous differentiation, providing a mechanism to explain the replacement of squamous epithelium by a glandular metaplasia upon exposure of the lower esophagus to gastric reflux.
Roman
Sabine
S
Digestive Physiology, Pavillon H, Hopital Edouard Herriot, Place d'Arsonval, 69437 Lyon Cedex 03, France. sabine.roman@chu-lyon.fr
Pétré
Aurélia
A
Thépot
Amélie
A
Hautefeuille
Agnès
A
Scoazec
Jean-Yves
JY
Mion
François
F
Hainaut
Pierre
P
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D017209:Apoptosis; D001471:Barrett Esophagus / Q000503:physiopathology; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002635:Chenodeoxycholic Acid / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D003840:Deoxycholic Acid / Q000494:pharmacology*; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000378:metabolism*; D004947:Esophagus / Q000187:drug effects / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007976:Leupeptins / Q000494:pharmacology; D061988:Proteasome Inhibitors; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology; D015534:Trans-Activators / Q000096:biosynthesis*; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis*
D004268:DNA-Binding Proteins; D007976:Leupeptins; D061988:Proteasome Inhibitors; C115051:TP63 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D003840:Deoxycholic Acid; D002635:Chenodeoxycholic Acid; C067713:lactacystin; D013655:Taurochenodeoxycholic Acid; D004317:Doxorubicin; D051546:Cyclooxygenase 2; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000111:Acetylcysteine