Bile acids induce overexpression of homeobox gene CDX-2 and vascular endothelial growth factor (VEGF) in human Barrett's esophageal mucosa and adenocarcinoma cell line.
OBJECTIVE
Barrett's esophagus (BE) is an acquired precancerous condition that develops from mucosal injury incurred after chronic gastroesophageal acid and bile reflux. The mechanism of progression of carcinogenesis in BE is still not fully understood. Recently, the role of bile acids and the homeobox gene transcription factor CDX-2 has been suggested in the pathogenesis of BE. The aims of the present study were 1) to compare the mRNA and protein expression of CDX-2 in biopsies obtained from patients with BE and normal squamous epithelium and 2) to study the effect of two different bile salts, ursodeoxycholic acid (UDCA) and deoxycholic acid (DCA), on the mRNA expression of CDX-2 and vascular endothelial growth factor (VEGF) in Barrett's the adenocarcinoma cell line (OE-33).


METHODS
CDX-2 expression was measured in Barrett's mucosa and normal esophageal mucosa obtained from 15 patients with BE histologically diagnosed by immunohistochemistry, Western blot, and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In in vitro experiments, OE-33 cells were incubated with DCA (100 microM) and UDCA (100 microM) in neutral and shortly acidified media (pulse acidification). The expression of CDX-2 and VEGF was assessed by quantitative RT-PCR.


RESULTS
Both mRNA and protein expression of CDX-2 were significantly up-regulated in Barrett's mucosa as compared to normal esophageal mucosa. In neutral medium, OE-33 cells showed an increase in CDX-2 expression after incubation with DCA or UDCA. After short acidification of the medium, expression of CDX-2 in OE-33 cells was significantly higher than that in cells incubated in neutral pH. The addition of DCA and UDCA did not cause any further alteration in CDX-2 expression. In neutral and acidified medium, VEGF mRNA expression was only significantly up-regulated by DCA, but not by UDCA.


CONCLUSIONS
Bile acids, especially in acidic medium, increase expression of CDX-2. DCA appears to be a stronger stimulant of the expression of VEGF than UDCA in the Barrett's carcinoma cell line, indicating a stronger carcinogenic potential of this bile salt.
Burnat
Grzegorz
G
First Department of Medicine, University Erlangen-Nuremberg, Erlangen, Germany.
Rau
Tilman
T
Elshimi
Esam
E
Hahn
Eckhart Georg
EG
Konturek
Peter Christopher
PC
D000230:Adenocarcinoma / Q000235:genetics / Q000378:metabolism*; D000704:Analysis of Variance; D001471:Barrett Esophagus / Q000235:genetics / Q000378:metabolism*; D001647:Bile Acids and Salts / Q000494:pharmacology*; D015153:Blotting, Western; D000071616:CDX2 Transcription Factor; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism*; D004945:Esophagoscopy; D015972:Gene Expression Regulation, Neoplastic; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
D001647:Bile Acids and Salts; D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A