14-3-3{eta} Amplifies Androgen Receptor Actions in Prostate Cancer.
PURPOSE: Androgen receptor abundance and androgen receptor-regulated gene expression in castration-recurrent prostate cancer are indicative of androgen receptor activation in the absence of testicular androgen. Androgen receptor transactivation of target genes in castration-recurrent prostate cancer occurs in part through mitogen signaling that amplifies the actions of androgen receptor and its coregulators. Herein we report on the role of 14-3-3eta in androgen receptor action. Experimental Design and RESULTS: Androgen receptor and 14-3-3eta colocalized in COS cell nuclei with and without androgen, and 14-3-3eta promoted androgen receptor nuclear localization in the absence of androgen. 14-3-3eta interacted with androgen receptor in cell-free binding and coimmunoprecipitation assays. In the recurrent human prostate cancer cell line, CWR-R1, native endogenous androgen receptor transcriptional activation was stimulated by 14-3-3eta at low dihydrotestosterone concentrations and was increased by epidermal growth factor. Moreover, the dihydrotestosterone- and epidermal growth factor-dependent increase in androgen receptor transactivation was inhibited by a dominant negative 14-3-3eta. In the CWR22 prostate cancer xenograft model, 14-3-3eta expression was increased by androgen, suggesting a feed-forward mechanism that potentiates both 14-3-3eta and androgen receptor actions. 14-3-3eta mRNA and protein decreased following castration of tumor-bearing mice and increased in tumors of castrate mice after treatment with testosterone. CWR22 tumors that recurred 5 months after castration contained 14-3-3eta levels similar to the androgen-stimulated tumors removed before castration. In a human prostate tissue microarray of clinical specimens, 14-3-3eta localized with androgen receptor in nuclei, and the similar amounts expressed in castration-recurrent prostate cancer, androgen-stimulated prostate cancer, and benign prostatic hyperplasia were consistent with androgen receptor activation in recurrent prostate cancer. CONCLUSION: 14-3-3eta enhances androgen- and mitogen-induced androgen receptor transcriptional activity in castration-recurrent prostate cancer. (Clin Cancer Res 2009;15(24):7571-81).
Titus
Mark A
MA
Authors' Affiliations: Departments of Pediatrics (Laboratories for Reproductive Biology), Surgery (Division of Urology) and Pathology and Laboratory Medicine, Biochemistry and Biophysics, and Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina; Department of Urologic Oncology, Roswell Park Cancer Institute, and Department of Urology, University at Buffalo School of Medicine and Biotechnology, Buffalo, New York; and Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia.
Tan
Jiann-An
JA
Gregory
Christopher W
CW
Ford
O Harris
OH
Subramanian
Romesh R
RR
Fu
Haian
H
Wilson
Elizabeth M
EM
Mohler
James L
JL
French
Frank S
FS