All-trans retinoic acid induces XAF1 expression through an interferon regulatory factor-1 element in colon cancer

Gastroenterology. 2006 Mar;130(3):747-58. doi: 10.1053/j.gastro.2005.12.017.


Background & aims: X-linked inhibitor of apoptosis protein (XIAP)-associated factor 1 (XAF1) is a novel tumor suppressor and interferon (IFN)-stimulated gene. All-trans retinoic acid (ATRA) exerts an antiproliferative effect on tumor cells through up-regulation of IFN regulatory factor 1 (IRF-1) and the downstream IFN-stimulated genes. The aim of this study was to determine the effect and mechanism of ATRA on XAF1 expression and the role of XAF1 in ATRA-induced growth inhibition in colon cancer.

Methods: Gene expression is detected by reverse-transcription polymerase chain reaction and immunoblotting. The transcription activity of XAF1 promoter is examined by luciferase reporter assay. The activity of IFN regulatory factor binding element (IRF-E) is assessed by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Cell growth is evaluated by both in vitro and in vivo in nude mice xenografts.

Results: IFN-alfa stimulates XAF1 promoter activity in the colon cancer cells Lovo and SW1116 dose-dependently. An IRF-1 binding element (IRF-E-XAF1) is found in the -30 to -38 nucleotide region upstream of the ATG initiator codon of the XAF1 gene. Site-directed mutagenesis of IRF-E-XAF1 abrogates native and IFN-induced promoter activity and binding capacity. ATRA induces XAF1 expression both in vitro and in vivo through interaction with IRF-E-XAF1. Overexpression of XAF1 increases cell susceptibility to ATRA-induced growth suppression both in vitro and in vivo. Furthermore, the effect of ATRA on XAF1 expression is independent of the promoter methylation and the subcellular distribution of XIAP.

Conclusions: XAF1 participates in ATRA-induced growth suppression through IRF-1-mediated transcriptional regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Colonic Neoplasms / drug therapy
  • Colonic Neoplasms / metabolism*
  • CpG Islands
  • DNA Methylation
  • Gene Expression Regulation / drug effects
  • Humans
  • Interferon Regulatory Factor-1 / physiology*
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Mutagenesis, Site-Directed
  • Neoplasm Proteins / genetics*
  • Neoplasm Proteins / physiology
  • Promoter Regions, Genetic
  • Transcription Initiation Site
  • Tretinoin / pharmacology*


  • Interferon Regulatory Factor-1
  • Intracellular Signaling Peptides and Proteins
  • Neoplasm Proteins
  • XAF1 protein, human
  • Tretinoin