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EBP1, an ErbB3-binding protein, is decreased in prostate cancer and implicated in hormone resistance.

Abstract
Aberrant activation of the androgen receptor (AR) by the ErbB2/ErbB3 heterodimer contributes to the development of hormone resistance in prostate cancer. EBP1, an ErbB3-binding protein, acts as an AR corepressor. As EBP1 is decreased in preclinical models of hormone-refractory prostate cancer, we studied the expression of EBP1 in human prostate cancer. We found that the expression of the EBP1 gene was significantly decreased in prostate cancer tissues compared with benign prostate at both mRNA and protein levels. Restoration of EBP1 expression in the hormone-refractory LNCaP C81 cell line led to an amelioration of the androgen-independent phenotype based on established biological criteria and a reduction in the expression of a cohort of AR target genes. The ability of the ErbB3 ligand heregulin (HRG) to stimulate growth and AKT phosphorylation of hormone-refractory prostate cancer cells was abolished. Abrogation of EBP1 expression by short hairpin RNA in hormone-dependent LNCaP cells, which undergo apoptosis in response to HRG, resulted in HRG-stimulated cell growth. Restoration of EBP1 expression decreased the tumorigenicity of C81 xenografts in female mice, whereas elimination of EBP1 expression enhanced the ability of LNCaP cells to grow in female mice. Our data support a role for EBP1 in the development of hormone-refractory prostate cancer via inhibition of both AR- and HRG-stimulated growth and present a novel strategy for treating androgen-refractory prostate cancer.
AuthorsYuexing Zhang, Douglas Linn, Zhenqiu Liu, Jonathan Melamed, Fabio Tavora, Charles Y Young, Angelika M Burger, Anne W Hamburger
JournalMolecular cancer therapeutics (Mol Cancer Ther) Vol. 7 Issue 10 Pg. 3176-86 (Oct 2008) ISSN: 1535-7163 [Print] United States
PMID18852121 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Adaptor Proteins, Signal Transducing
  • Androgens
  • Neuregulin-1
  • PA2G4 protein, human
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • Phosphatidylinositol 3-Kinases
  • Receptor, ErbB-3
  • Proto-Oncogene Proteins c-akt
Topics
  • Adaptor Proteins, Signal Transducing (genetics, metabolism)
  • Androgens (pharmacology)
  • Animals
  • Cell Line, Tumor
  • Cell Proliferation (drug effects)
  • Disease Models, Animal
  • Disease Progression
  • Drug Resistance, Neoplasm (drug effects)
  • Gene Expression Regulation, Neoplastic (drug effects)
  • Humans
  • Male
  • Mice
  • Neuregulin-1 (metabolism)
  • Phenotype
  • Phosphatidylinositol 3-Kinases (metabolism)
  • Prostatic Neoplasms (enzymology, genetics, metabolism)
  • Proto-Oncogene Proteins c-akt (metabolism)
  • RNA, Small Interfering (metabolism)
  • RNA-Binding Proteins (genetics, metabolism)
  • Receptor, ErbB-3 (metabolism)
  • Signal Transduction (drug effects)
  • Transfection

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