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A natural androgen receptor antagonist induces cellular senescence in prostate cancer cells.

Abstract
We have previously identified a natural occurring, androgen receptor-specific antagonist. Atraric acid (AA) inhibits the transactivation of the androgen receptor (AR) and androgen-mediated growth of AR-expressing human prostate cancer (PCa) cell lines. Here we show that AA treatment of living cells provokes molecular changes of AR signaling. In addition to a deceleration of nuclear translocation a block of the intramolecular amino/carboxy (N/C)-terminal interaction of the AR was observed. Furthermore, using high-resolution confocal fluorescence microscopy, a reduced speckle formation of the AR was observed in line with an increased intranuclear mobility of the receptor. This suggests decreased DNA binding of the AR, which is further indicated by an impaired chromatin recruitment of the AR to the prostate-specific antigen promoter and enhancer shown by chromatin immunoprecipitation experiments. Using inhibitors of the non-receptor tyrosine kinase Src or Akt, known interaction partners of AR, reduced the level of androgen-induced cellular senescence suggesting a partly non-genomic pathway to induce cellular senescence by AA. Using PP2 (4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine) pyrimidine or Akt inhibitors, inhibitors of the nonreceptor tyrosine kinase Src or Akt, known interaction partners of AR, reduced the level of androgen-induced cellular senescence, suggesting a partly nongenomic pathway to induce cellular senescence by AA. Treatment of LNCaP cells with AA is associated with hypophosphorylation of the retinoblastoma tumor suppressor and an increase of p16 expression, whereas the p53-p21 signaling pathway seems not be affected by AA treatment. Analyzing human PCa tissue samples treated with AA ex vivo also indicates an induction of cellular senescence associated with an increase of p16 expression but not p21. Taken together, these data indicate that AA exhibits novel features to inhibit AR amino/carboxy-terminal interaction, the AR-mediated nuclear activities and growth of PCa cells.
AuthorsWiebke Hessenkemper, Julia Roediger, Sophie Bartsch, Adriaan B Houtsmuller, Martin E van Royen, Iver Petersen, Marc-Oliver Grimm, Aria Baniahmad
JournalMolecular endocrinology (Baltimore, Md.) (Mol Endocrinol) Vol. 28 Issue 11 Pg. 1831-40 (Nov 2014) ISSN: 1944-9917 [Electronic] United States
PMID25203674 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • AR protein, human
  • Androgen Receptor Antagonists
  • Androgens
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p16
  • Cyclin-Dependent Kinase Inhibitor p21
  • Receptors, Androgen
  • Tumor Suppressor Protein p53
  • src-Family Kinases
  • Proto-Oncogene Proteins c-akt
  • Prostate-Specific Antigen
Topics
  • Androgen Receptor Antagonists (pharmacology)
  • Androgens (metabolism)
  • Cell Aging (drug effects)
  • Cell Line, Tumor
  • Cyclin-Dependent Kinase Inhibitor p16 (metabolism)
  • Cyclin-Dependent Kinase Inhibitor p21 (metabolism)
  • Gene Expression Regulation, Neoplastic (drug effects)
  • Humans
  • Male
  • Prostate (drug effects, metabolism)
  • Prostate-Specific Antigen (metabolism)
  • Prostatic Neoplasms (metabolism)
  • Proto-Oncogene Proteins c-akt (metabolism)
  • Receptors, Androgen (metabolism)
  • Signal Transduction (drug effects)
  • Transcriptional Activation (drug effects)
  • Tumor Suppressor Protein p53 (metabolism)
  • src-Family Kinases (metabolism)

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