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Suppression of beta-catenin signaling by liver X receptor ligands

Shigeyuki Uno1, Kaori Endo, Yangsik Jeong

  • 1Division of Biochemistry, Department of Biomedical Sciences, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan.

Biochemical Pharmacology
|November 6, 2008
PubMed

Insights

Liver X receptors (LXRs) regulate lipid metabolism and colon cancer pathways. LXR activation suppresses beta-catenin activity, inhibiting cell proliferation by targeting key genes.

Area of Science:

  • Molecular Biology
  • Oncology
  • Lipid Metabolism

Background:

  • Nuclear receptors liver X receptor (LXR) alpha and LXRbeta are key regulators of lipid metabolism.
  • The Wnt signaling pathway, involving beta-catenin, is crucial in colon carcinogenesis.
  • Understanding the interplay between LXRs and beta-catenin is vital for cancer research.

Purpose of the Study:

  • To investigate the effects of LXRs on colon carcinogenesis pathways.
  • To determine how LXR activation influences beta-catenin transactivation activity.
  • To elucidate the molecular mechanisms underlying LXR-beta-catenin interactions in colon cancer.

Main Methods:

  • Ligand-dependent and independent assays to assess LXR and beta-catenin interactions.
  • Co-immunoprecipitation in HCT116 colon cancer cells.
  • Analysis of mRNA expression of beta-catenin target genes (MYC, MMP7, BMP4).
  • Experiments using dominant-negative LXR and LXR-null cells.

Main Results:

  • LXR activation suppressed beta-catenin transactivation activity in a ligand-dependent manner.
  • LXRs directly bind to the Armadillo repeat region of beta-catenin.
  • LXR activation decreased MYC, MMP7, and BMP4 mRNA expression and recruited LXRs to their promoters.
  • Cellular LXRs were involved in beta-catenin suppression and inhibition of colon cancer cell proliferation.

Conclusions:

  • Lipid-sensing receptors LXRs play a regulatory role in beta-catenin activity and cellular proliferation.
  • LXR activation presents a potential therapeutic strategy for colon cancer by modulating Wnt signaling.
  • The findings highlight a novel mechanism linking lipid metabolism and colon cancer progression.

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