In vitro acid exposure has a differential effect on apoptotic and proliferative pathways in a Barrett's adenocarcinoma cell line.
BACKGROUND
Acid, a principal component of refluxate, may contribute to the neoplastic progression of Barrett's esophagus. Brief acid exposure in vivo and in vitro has been shown to increase cell proliferation. The mechanisms underlying the hyperproliferative response are not well elucidated but may include alterations in Na(+)-H+ exchanger activity and MAPK signaling pathways.


OBJECTIVE
To ascertain the effects of pulsatile acid exposure on gene expression in a Barrett's adenocarcinoma cell line (SEG-1).


METHODS
SEG-1 cells were exposed to either acidified DMEM at pH 3.5 (0.1 M hydrochloric acid) or pH 7.4 (control) for 20 min followed by neutralization of the medium. Total RNA was extracted before acid exposure and over a 10-h time course (0.5, 2, 4, 6, 8, and 10 hours) and hybridized to Affymetrix human U133A oligonucleotide arrays. Data were analyzed using the Affymetrix statistical expression algorithms. Only alterations in gene expression that were > or = 2 and < or = -2 fold were studied further and a subset was further investigated by reverse transcription polymerase chain reaction (RT-PCR) and densitometry. Apoptosis was assayed in SEG-1 cells by western blot for cleaved caspase 3 and an apoptosis ELISA assay.


RESULTS
Changes in expression were identified for 138 genes. Analysis of gene function identified immediate downregulation of genes associated with apoptosis and early upregulation of genes associated with proliferation. The gene expression profiles suggest that MAPK pathways may be involved and suppression of apoptosis may occur via p53-dependent mechanisms.


CONCLUSIONS
Microarray analysis of gene expression changes in a Barrett's adenocarcinoma cell line has identified cellular pathways that may be disrupted following acid exposure.
Morgan
Claire
C
MRC Cancer Cell Unit, Hutchison-MRC Research Centre, Hills Road, Cambridge CB2 2XZ, UK.
Alazawi
William
W
Sirieix
Pierre
P
Freeman
Tom
T
Coleman
Nicholas
N
Fitzgerald
Rebecca
R
D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001471:Barrett Esophagus / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D053148:Caspase 3; D020169:Caspases / Q000032:analysis / Q000235:genetics; D002453:Cell Cycle / Q000235:genetics; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D004938:Esophageal Neoplasms / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics*; D006801:Humans; D006851:Hydrochloric Acid / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods
C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D006851:Hydrochloric Acid