Bile acids induce ectopic expression of intestinal guanylyl cyclase C Through nuclear factor-kappaB and Cdx2 in human esophageal cells.
OBJECTIVE
Although progression to adenocarcinoma at the gastroesophageal junction reflects exposure to acid and bile acids associated with reflux, mechanisms mediating this transformation remain undefined. Guanylyl cyclase C (GC-C), an intestine-specific tumor suppressor, may represent a mechanism-based marker and target of transformation at the gastroesophageal junction. The present studies examine the expression of GC-C in normal tissues and tumors from esophagus and stomach and mechanisms regulating its expression by acid and bile acids.


METHODS
Gene expression was examined by reverse-transcription polymerase chain reaction, promoter analysis, immunohistochemistry, immunoblotting, and functional analysis. Promoter transactivation was quantified by using luciferase constructs and mutational analysis. DNA binding of transcription factors was examined by electromobility shift analysis.


RESULTS
GC-C mRNA and protein were ectopically expressed in approximately 80% of adenocarcinomas arising in, but not in normal, esophagus and stomach. Similarly, in OE19 human esophageal cancer cells, deoxycholate and acid induced expression of GC-C. This was associated with the induction of expression of Cdx2, a transcription factor required for GC-C expression. In turn, induction of Cdx2 expression by deoxycholate was mediated by binding sites in the proximal promoter for nuclear factor kappaB (NF-kappaB). Furthermore, deoxycholate increased NF-kappaB activity, associated with nuclear translocation and Cdx2 promoter binding of the NF-kappaB subunit p50. Moreover, a dominant negative construct for NF-kappaB prevented deoxycholate-induced p50 nuclear translocation and activation of the Cdx2 promoter.


CONCLUSIONS
Transformation associated with reflux at the gastroesophageal junction reflects activation by bile acid and acid of a transcriptional program involving NF-kappaB and Cdx2, which mediate intestinal metaplasia and ectopic expression of GC-C.
Debruyne
Philip R
PR
Department of Pharmacology and Experimental Therapeutics, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Witek
Matthew
M
Gong
Li
L
Birbe
Ruth
R
Chervoneva
Inna
I
Jin
Tianru
T
Domon-Cell
Claire
C
Palazzo
Juan P
JP
Freund
Jean-Noel
JN
Li
Peng
P
Pitari
Giovanni M
GM
Schulz
Stephanie
S
Waldman
Scott A
SA
D000230:Adenocarcinoma / Q000201:enzymology; D001647:Bile Acids and Salts / Q000494:pharmacology*; D000071616:CDX2 Transcription Factor; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D003840:Deoxycholic Acid / Q000494:pharmacology; D004938:Esophageal Neoplasms / Q000201:enzymology; D004943:Esophagogastric Junction / Q000201:enzymology / Q000378:metabolism; D004947:Esophagus / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D015870:Gene Expression; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007422:Intestines / Q000201:enzymology*; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects
D001647:Bile Acids and Salts; D000071616:CDX2 Transcription Factor; C491270:CDX2 protein, human; D018398:Homeodomain Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D018000:Receptors, Peptide; D003840:Deoxycholic Acid; D006162:Guanylate Cyclase; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled