Castration resistance in human prostate cancer is conferred by a frequently occurring androgen receptor splice variant
Shihua Sun, … , Peter S. Nelson, Stephen R. Plymate
Shihua Sun, … , Peter S. Nelson, Stephen R. Plymate
Published July 19, 2010
Citation Information: J Clin Invest. 2010;120(8):2715-2730. https://doi.org/10.1172/JCI41824.
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Research Article Oncology

Castration resistance in human prostate cancer is conferred by a frequently occurring androgen receptor splice variant

Abstract

Progression of prostate cancer following castration is associated with increased androgen receptor (AR) expression and signaling despite AR blockade. Recent studies suggest that these activities are due to the generation of constitutively active AR splice variants, but the mechanisms by which these splice variants could mediate such effects are not fully understood. Here we have identified what we believe to be a novel human AR splice variant in which exons 5, 6, and 7 are deleted (ARv567es) and demonstrated that this variant can contribute to cancer progression in human prostate cancer xenograft models in mice following castration. We determined that, in human prostate cancer cell lines, ARv567es functioned as a constitutively active receptor, increased expression of full-length AR (ARfl), and enhanced the transcriptional activity of AR. In human xenografts, human prostate cancer cells transfected with ARv567es cDNA formed tumors that were resistant to castration. Furthermore, the ratio of ARv567es to ARfl expression within the xenografts positively correlated with resistance to castration. Importantly, we also detected ARv567es frequently in human prostate cancer metastases. In summary, these data indicate that constitutively active AR splice variants can contribute to the development of castration-resistant prostate cancers and may serve as biomarkers for patients who are likely to suffer from early recurrence and are candidates for therapies directly targeting the AR rather than ligand.

Authors

Shihua Sun, Cynthia C.T. Sprenger, Robert L. Vessella, Kathleen Haugk, Kathryn Soriano, Elahe A. Mostaghel, Stephanie T. Page, Ilsa M. Coleman, Holly M. Nguyen, Huiying Sun, Peter S. Nelson, Stephen R. Plymate

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Figure 3

Constitutive activation of the ARv567es in M12 prostate cancer cells.

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Constitutive activation of the ARv567es in M12 prostate cancer cells. ...
(A) The AR-null M12 human prostate cancer cells were transiently transfected with ARfl or the splice variant ARv567es. The Western immunoblot of transfected cells shows expression of either ARfl or ARv567es. AR was detected with AR sc441 antibody, which detects both full-length and variant AR. GAPDH was used as a loading control. (B) ARE luciferase assay with the ARR3-Luc reporter. The M12 pcDNA empty vector control cells show that no AR activity is detected for any of the treatments. The M12 ARfl cells had very low reporter activity in the absence of androgen as well as in the presence of the AR antagonist, flutamide, but had a clear increase in luciferase activity when 10–9 M DHT was added. In contrast, M12 ARv567es cells showed maximal reporter activity regardless of treatment. Values are mean ± SEM. *P < 0.01, DHT vs. no added DHT or DHT plus flutamide compared with DHT alone for ARfl. There were no differences among treatments for pcDNA or ARv567es cells. (C) Immunofluorescence staining of ARfl and ARv567es. In the absence of ligand, ARfl is in the cytoplasm and translocates to the nucleus after addition of DHT. However, the constitutively active AR variant is primarily intranuclear in the absence of DHT and no change is seen when DHT is added. Nuclei are shown with DAPI staining. Arrows indicate examples of cells that are positive for nuclear translocation of AR. Scale bars: 10 μm.