The decreased expression of Beclin-1 correlates with progression to esophageal adenocarcinoma: the role of deoxycholic acid.
Beclin-1 has a central role in the regulation of autophagy. Barrett's esophagus (BE) is associated with a significantly increased risk for the development of esophageal adenocarcinoma (EAC). In the current study, we evaluated the role of Beclin-1 and autophagy in the EAC. Biopsies obtained from patients with BE and EAC, tissues from a rat model of BE and EAC, and esophageal cell lines were evaluated for the expression of Beclin-1 by immunohistochemistry, immunoblotting, or RT-PCR. Since reflux of bile acids is important in EAC, we also evaluated the effect of exposure to deoxycholic acid (DCA) on autophagy and Beclin-1 expression. Beclin-1 expression was high in squamous epithelium and nondysplastic BE, whereas its expression was low in dysplastic BE and EAC. The same pattern of expression was observed in rat tissues and in esophageal cell lines. Normal esophageal epithelium and HET-1A cells (derived from normal squamous epithelium) show high levels of Beclin-1, but lower levels of Beclin-1 were found in BE and EAC cell lines (CP-A, CP-C, and OE33). Acute exposure to DCA led to increased Beclin-1 expression and increased autophagy as evaluated by electron microscopy and counting percentage of GFP-LC3-positive BE cells with punctate pattern. In contrast, chronic exposure to DCA did not result in the alteration of Beclin-1 levels or autophagy. In summary, these data suggest that autophagy is initially activated in response to bile acids, but chronic exposure to bile acids leads to decreased Beclin-1 expression and autophagy resistance.
Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA.
Heather B
HB
Roesly
Mohammad R
MR
Khan
Hwu Dau Rw
HD
Chen
Kimberly A
KA
Hill
Nirushan
N
Narendran
George S
GS
Watts
Xiaoxin
X
Chen
Katerina
K
Dvorak
D000230:Adenocarcinoma / Q000473:pathology*; D000596:Amino Acids / Q000172:deficiency; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000096:biosynthesis* / Q000502:physiology*; D001343:Autophagy; D001471:Barrett Esophagus / Q000473:pathology; D000071186:Beclin-1; D001647:Bile Acids and Salts / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D003840:Deoxycholic Acid / Q000494:pharmacology / Q000502:physiology*; D018450:Disease Progression; D004938:Esophageal Neoplasms / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000502:physiology*; D046228:Microarray Analysis; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction
D000596:Amino Acids; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D001647:Bile Acids and Salts; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D003840:Deoxycholic Acid; D012313:RNA