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.
University of Texas Southwestern Medical Center at Dallas, VA North Texas Health Center, Dallas, TX 75216, USA.
Kshama
K
Jaiswal
Vincent
V
Tello
Christie
C
Lopez-Guzman
Fiemu
F
Nwariaku
Thomas
T
Anthony
George A
GA
Sarosi
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