Bile salt exposure causes phosphatidyl-inositol-3-kinase-mediated proliferation in a Barrett's adenocarcinoma cell line.
BACKGROUND
The mechanisms by which gastroesophageal reflux promotes malignant progression in Barrett's esophagus are poorly understood. The phosphatidylinositol-3-kinase (PI3 kinase)/Akt pathway regulates proliferation and apoptosis. We hypothesized that the PI3 kinase/Akt pathway mediates the pro-proliferative and antiapoptotic effects of bile.


METHODS
The Barrett's adenocarcinoma cell line, SEG-1, was exposed to the conjugated bile salt, glycochenodeoxycholic acid (GCDA). Cell number was measured by the MTT incorporation assay and by Coulter counter. PI3 kinase/Akt activity was inferred from Western blots of phosphorylated and total Akt. Proliferation and apoptosis were determined by BrdU incorporation and cell death ELISA.


RESULTS
A dose-dependent cell number increase was seen with a 20-minute exposure to GCDA. On Western blot, 200 micromol/L GCDA caused a 3-fold increase in Akt phosphorylation within 20 minutes, which was inhibited by 90% with the addition of PI3 kinase inhibitor, LY294002. LY294002 produced dose-dependent inhibition of GCDA-induced cell number increases. 200 micromol/L GCDA decreased apoptosis by 25%. Addition of LY294002 did not completely inhibit the antiapoptotic effect of bile.


CONCLUSIONS
Bile salts activate the PI3 kinase/Akt signaling pathway and stimulate cell growth in SEG-1. The majority of this PI3 kinase-mediated effect is secondary to increases in proliferation rather than to decreases in apoptosis.
Jaiswal
Kshama
K
University of Texas Southwestern Medical Center at Dallas, VA North Texas Health Center, Dallas, TX 75216, USA.
Tello
Vincent
V
Lopez-Guzman
Christie
C
Nwariaku
Fiemu
F
Anthony
Thomas
T
Sarosi
George A
GA
D000230:Adenocarcinoma / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects; D001471:Barrett Esophagus / Q000150:complications*; D020169:Caspases / Q000378:metabolism; D002455:Cell Division; D045744:Cell Line, Tumor; D002867:Chromones / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004938:Esophageal Neoplasms / Q000473:pathology*; D005999:Glycochenodeoxycholic Acid / Q000494:pharmacology*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*
D002867:Chromones; D009025:Morpholines; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D005999:Glycochenodeoxycholic Acid; D019869:Phosphatidylinositol 3-Kinases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases