Bicalutamide functions as an androgen receptor antagonist by assembly of a transcriptionally inactive receptor

J Biol Chem. 2002 Jul 19;277(29):26321-6. doi: 10.1074/jbc.M203310200. Epub 2002 May 15.

Abstract

Prostate cancers (PCa) that relapse after androgen deprivation therapy invariably express high levels of androgen receptor (AR) and AR-regulated genes. Most do not respond to secondary hormonal therapies, including AR antagonists, and the mechanisms of AR activation in these clinically androgen-independent tumors are unclear. Bicalutamide, the most widely used AR antagonist, is a competitive antagonist shown previously to stabilize AR association with cytosolic heat shock protein complexes. This study found nuclear AR expression in bicalutamide-treated androgen-independent PCa and found that bicalutamide could stimulate AR nuclear translocation. Moreover, specific DNA binding by the bicalutamide-liganded AR was demonstrated in vivo using a VP16-AR fusion protein and was confirmed by chromatin immunoprecipitation showing binding to the prostate-specific antigen enhancer in LNCaP PCa cells. Nonetheless, bicalutamide could not stimulate interactions between the AR N and C termini or recruitment of steroid receptor coactivator proteins (SRC-1 or -2), although SRC transfection augmented AR activity in the presence of dihydrotestosterone and inhibitory concentrations of bicalutamide. These results demonstrate that bicalutamide stimulates the assembly of a transcriptionally inactive AR on DNA and support altered coactivator (or corepressor) expression as a mechanism of bicalutamide-resistant androgen-independent PCa.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Androgen Antagonists / pharmacology*
  • Androgen Receptor Antagonists*
  • Anilides / pharmacology*
  • Animals
  • Coleoptera
  • Etoposide / metabolism
  • Histone Acetyltransferases
  • Humans
  • Male
  • Mice
  • Nitriles
  • Nuclear Receptor Coactivator 1
  • Nuclear Receptor Coactivator 2
  • Prostate-Specific Antigen / biosynthesis
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / metabolism
  • Rabbits
  • Receptors, Androgen / genetics
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Tosyl Compounds
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic / drug effects*
  • Transfection

Substances

  • Androgen Antagonists
  • Androgen Receptor Antagonists
  • Anilides
  • Nitriles
  • Nuclear Receptor Coactivator 2
  • Receptors, Androgen
  • Recombinant Fusion Proteins
  • Tosyl Compounds
  • Transcription Factors
  • Etoposide
  • bicalutamide
  • Histone Acetyltransferases
  • NCOA1 protein, human
  • Ncoa1 protein, mouse
  • Nuclear Receptor Coactivator 1
  • Prostate-Specific Antigen