Role of the androgen receptor in breast cancer and preclinical analysis of enzalutamide

INTRODUCTION: The androgen receptor (AR) is widely expressed in breast cancers and has been proposed as a therapeutic target in estrogen receptor alpha (ER) negative breast cancers that retain AR. However, controversy exists regarding the role of AR, particularly in ER + tumors. Enzalutamide, an AR inhibitor that impairs nuclear localization of AR, was used to elucidate the role of AR in preclinical models of ER positive and negative breast cancer. METHODS: We examined nuclear AR to ER protein ratios in primary breast cancers in relation to response to endocrine therapy. The effects of AR inhibition with enzalutamide were examined in vitro and in preclinical models of ER positive and negative breast cancer that express AR. RESULTS: In a cohort of 192 women with ER + breast cancers, a high ratio of AR:ER (≥2.0) indicated an over four fold increased risk for failure while on tamoxifen (HR = 4.43). The AR:ER ratio had an independent effect on risk for failure above ER % staining alone. AR:ER ratio is also an independent predictor of disease-free survival (HR = 4.04, 95% CI: 1.68, 9.69; p = 0.002) and disease specific survival (HR = 2.75, 95% CI: 1.11, 6.86; p = 0.03). Both enzalutamide and bicalutamide inhibited 5-alpha-dihydrotestosterone (DHT)-mediated proliferation of breast cancer lines in vitro; however, enzalutamide uniquely inhibited estradiol (E2)-mediated proliferation of ER+/AR + breast cancer cells. In MCF7 xenografts (ER+/AR+) enzalutamide inhibited E2-driven tumor growth as effectively as tamoxifen by decreasing proliferation. Enzalutamide also inhibited DHT- driven tumor growth in both ER positive (MCF7) and negative (MDA-MB-453) xenografts, but did so by increasing apoptosis. CONCLUSIONS: AR to ER ratio may influence breast cancer response to traditional endocrine therapy. Enzalutamide elicits different effects on E2-mediated breast cancer cell proliferation than bicalutamide. This preclinical study supports the initiation of clinical studies evaluating enzalutamide for treatment of AR(+) tumors regardless of ER status, since it blocks both androgen- and estrogen- mediated tumor growth

A p38 Mitogen‐Activated Protein Kinase Inhibitor Arrests Active Alveolar Bone Loss in a Rat Periodontitis Model

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141943/1/jper1992.pd

Effect of MDV3100, a novel androgen receptor signaling inhibitor, on cell proliferation and tumor size in an apocrine breast cancer xenograft model.

3072 Background: MDV3100, a new androgen receptor (AR) signaling inhibitor, has demonstrated therapeutic effects in men with post-docetaxel prostate cancer (AFFIRM). AR is also expressed in the majority of breast cancers. Molecular profiling of estrogen receptor negative (ER-) breast cancer classifies this disease into basal and molecular apocrine subtypes. Apocrine breast cancer represents ~50% of ER- tumors and is characterized by a steroid response gene signature that includes AR expression. Here we report the effects of MDV3100 on the growth of the ER-/AR+ breast cancer cell line MDA-MB-453 in tissue culture and in an in vivo xenograft mouse model. Methods: MDA-MB-453 cells were maintained in 5% complete or 5% charcoal-stripped serum supplemented with dihydrotestosterone (CSS-DHT). The DHT induced nuclear translocation of AR was determined by subcellular fractionation followed by western blot. AR target gene expression was measured by qPCR. To generate a mouse xenograft model, 5-6 wk old female NOD-SCID-IL2Rgc–/– mice were injected ortotopically with 6x106 MDA-MB-453 cells into the fourth inguinal gland and were administered exogenous DHT (12.5 mg in a 60 day release pellet) or control pellets. When tumor size reached 100 mm3, mice were treated with 10 mg/kg/day MDV3100 or vehicle (0.5% methocel solution) by oral gavage for 33 days. Results: Viability of MDA-MB-453 cells treated with 10 uM MDV3100 was reduced by 10% after 3 days and 27% after 6 days. Treatment with 25 uM MDV3100 reduced cell viability by 27% after 3 days and 36% after 6 days. Similar results were obtained when cells maintained in CSS-DHT were treated with MDV3100. Treatment with MDV3100 blocked DHT-induced nuclear translocation and concordantly reduced the expression of AR-targets fatty acid synthase, prolactin receptor, and gross cystic disease protein-15. In the xenograft model, MDV3100 inhibited tumor growth by 78% as compared to tumors treated with vehicle. Conclusions: MDV3100 reduced cell proliferation in apocrine cell lines. MDV3100 also suppressed exogenous DHT-induced growth of ER-/AR+ tumors in vivo. These results support the evaluation of MDV3100 as a treatment for apocrine tumors. </jats:p

Abstract A76: MDV3100, a novel androgen receptor signaling inhibitor, promotes cell apoptosis and tumor regression in both in vitro and in vivo models of castration-resistant prostate cancer.

Abstract Prostate tumors initially respond to androgen deprivation therapy but eventually progress despite low serum levels of testosterone. In this stage, known as castration-resistant prostate cancer (CRPC), abnormal androgen receptor (AR) signaling persists and classic anti-androgens such as bicalutamide are ineffective at controlling tumor growth. The novel AR signaling inhibitor MDV3100 has been demonstrated to inhibit AR signaling in preclinical models of CRPC. Here, we investigate further the cellular effects of MDV3100 treatment on AR signaling in in vitro models and in vivo xenograft models of CRPC. Our experiments reveal that MDV3100 (&amp;gt; 100 nM) inhibits dihydrotestosterone (DHT) induced AR-target gene expression in LNCaP cells and LNCaP/AR cells, a CRPC cell culture model in which AR is over-expressed. Inhibition of Prostate-Specific Antigen mRNA expression by MDV3100 was effective at concentrations 10-fold lower than with bicalutamide. As evidenced in other studies and in contrast to bicalutamide, MDV3100 did not display agonistic effects on AR signaling at 10 μM. In contrast to bicalutamide, MDV3100 (&amp;gt; 1 μM) inhibited androgen dependent nuclear translocation of AR, as measured with a quantitative optical based enzyme fragment complementation assay and AR-YFP localization in HEK-293 cells. Furthermore, in the presence of DHT, MDV3100 effectively reduced cell viability of LNCaP cells at concentrations as low as 0.1 μM, 10-fold lower than bicalutamide. MDV3100 also decreased cell viability of LNCaP/AR and W741C-LNcaP cells. We found that the apoptosis marker cleaved-caspase 3 was induced in LNCaP/AR cells treated with 1 M MDV3100 for 48 hours. Under these conditions, MDV3100 was more potent than bicalutamide in decreasing cell viability. Finally, we show that MDV3100 inhibited tumor growth and induced regression of tumor volume in a xenograft model of CRPC generated with LNCaP/AR cells. These results demonstrate that MDV3100, unlike anti-androgens, is effective in both in vitro and in vivo models of CRPC and that its mechanistic advantages over other anti-androgens could be explained by its ability to inhibit AR nuclear translocation and induce cell death. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A76.</jats:p