Liver X Receptor activation downregulates AKT survival signaling in lipid rafts and induces apoptosis of prostate cancer cells

Oncogene. 2010 May 6;29(18):2712-23. doi: 10.1038/onc.2010.30. Epub 2010 Mar 1.

Abstract

Cholesterol is a structural component of lipid rafts within the plasma membrane. These domains, used as platforms for various signaling molecules, regulate cellular processes including cell survival. Cholesterol contents are tightly correlated with the structure and function of lipid rafts. Liver X receptors (LXRs) have a central role in the regulation of cholesterol homeostasis within the cell. Therefore, we investigated whether these nuclear receptors could modulate lipid raft signaling and consequently alter prostate cancer (PCa) cell survival. Treatment with the synthetic LXR agonist T0901317 downregulated the AKT survival pathway and thus induced apoptosis of LNCaP PCa cells in both xenografted nude mice and cell culture. The decrease in tumor cholesterol content resulted from the upregulation of ABCG1 and the subsequent increase in reverse cholesterol transport. RNA interference experiments showed that these effects were mediated by LXRs. Atomic force microscopy scanning of the inner plasma membrane sheet showed smaller and thinner lipid rafts after LXR stimulation, associated with the downregulation of AKT phosphorylation in these lipid rafts. Replenishment of cell membranes with exogenous cholesterol antagonized these effects, showing that cholesterol is a key modulator in this process. Altogether, pharmacological modulation of LXR activity could thus reduce prostate tumor growth by enhancing apoptosis in a lipid raft-dependent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 1
  • ATP-Binding Cassette Transporters / physiology
  • Animals
  • Apoptosis*
  • Carbon-Carbon Ligases / physiology
  • Cell Line, Tumor
  • Cholesterol / metabolism
  • Down-Regulation
  • Hydrocarbons, Fluorinated / pharmacology
  • Liver X Receptors
  • Male
  • Membrane Microdomains / physiology*
  • Mice
  • Mice, Nude
  • Orphan Nuclear Receptors / physiology*
  • Prostatic Neoplasms / pathology*
  • Proto-Oncogene Proteins c-akt / antagonists & inhibitors
  • Proto-Oncogene Proteins c-akt / physiology*
  • Signal Transduction*
  • Sulfonamides / pharmacology

Substances

  • ABCG1 protein, human
  • ATP Binding Cassette Transporter, Subfamily G, Member 1
  • ATP-Binding Cassette Transporters
  • Hydrocarbons, Fluorinated
  • Liver X Receptors
  • Orphan Nuclear Receptors
  • Sulfonamides
  • TO-901317
  • Cholesterol
  • Proto-Oncogene Proteins c-akt
  • Carbon-Carbon Ligases
  • acyl-CoA carboxylase