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Keywords:

  • bile acids;
  • farnesoid X-activated receptor;
  • retinoic acid receptor;
  • cyclooxygenase 2;
  • guggulsterone;
  • esophageal cancer

Abstract

BACKGROUND:

Gastroesophageal reflux is a risk factor for esophageal adenocarcinoma, and bile acid and its farnesoid X receptor (FXR) have been implicated in esophageal tumorigenesis. The authors investigated the role of FXR expression and activity in esophageal cancer initiation and growth.

METHODS:

FXR expression in esophageal adenocarcinoma tissues was assessed by immunohistochemistry. Knockdown of FXR expression in esophageal cancer cells in vitro and in nude mice xenografts was suppressed by FXR small hairpin RNA (shRNA) and guggulsterone (a natural FXR inhibitor). Esophageal cancer cells were treated with bile acids to demonstrate their effects on growth-promoting genes.

RESULTS:

FXR was expressed in 48 of 59 esophageal adenocarcinoma tissues (81.3%), and this overexpression was associated with higher tumor grade, larger tumor size, and lymph node metastasis; however, was inversely associated with retinoic acid receptor-β2 (RAR2) expression. Knockdown of FXR expression suppressed tumor cell growth in vitro and in nude mouse xenografts. Guggulsterone reduced the viability of esophageal cancer cells in a time-dependent and dose-dependent manner, whereas this effect was diminished after knockdown of FXR expression. Guggulsterone induced apoptosis through activation of caspase-8, caspase-9, and caspase-3 in tumor cells. FXR mediated bile acid-induced alterations of gene expression, eg, RAR2 and cyclooxygenase-2 (COX-2).

CONCLUSIONS:

Inhibition of FXR by FXR shRNA or guggulsterone suppressed tumor cell viability and induced apoptosis in vitro, and it reduced tumor formation and growth in nude mouse xenografts. FXR also mediated bile acid-induced alterations of cell growth-related genes in esophageal cancer cells. Cancer 2013. © 2012 American Cancer Society.