Abstract

Despite recent advances in diagnosis and management, prostrate cancer remains the second most common cause of death from cancer in American men, after lung cancer. Failure of chemotherapies and hormone-deprivation therapies is the major cause of death in patients with castration-resistant prostate cancer (CRPC). Currently, the androgen inhibitors enzalutamide and abiraterone are approved for treatment of metastatic CRPC. Here we show for the first time that both enzalutamide and abiraterone render prostate tumor cells more sensitive to T cell-mediated lysis through immunogenic modulation, and that these immunomodulatory activities are androgen receptor (AR)-dependent. In studies reported here, the NAIP gene was significantly down-regulated in human prostate tumor cells treated in vitro and in vivo with enzalutamide. Functional analysis revealed that NAIP played a critical role in inducing CTL sensitivity. Amplification of AR is a major mechanism of resistance to androgen-deprivation therapy (ADT). Here, we show that enzalutamide enhances sensitivity to immune-mediated killing of prostate tumor cells that overexpress AR. The immunomodulatory properties of enzalutamide and abiraterone provide a rationale for their use in combination with immunotherapeutic agents in CRPC, especially for patients with minimal response to enzalutamide or abiraterone alone, or for patients who have developed resistance to ADT.

Highlights

  • IntroductionMost patients eventually develop castration-resistant prostate cancer (CRPC)

  • Androgen deprivation therapy (ADT) is a standard of care for prostate cancer [1, 2]

  • Neither enzalutamide nor abiraterone improved PC-3 cells’ sensitivity to MUC1specific cytotoxic T-lymphocyte (CTL)-mediated lysis (Figs. 1D and 1H) relative to vehicle-treated tumor cells. These results suggested that both enzalutamide and abiraterone mediated immunogenic modulation in human prostate tumor cells, and this effect was dependent on androgen receptor (AR) expression

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Summary

Introduction

Most patients eventually develop castration-resistant prostate cancer (CRPC). The utility of enzalutamide has been demonstrated in clinical trials [4,5,6], including the AFFIRM trial where it mediated a 4.8-month advantage in overall survival compared to placebo [6]. Abiraterone is a potent inhibitor of CYP17A1, a rate-limiting enzyme in androgen biosynthesis. Inhibition of this enzyme subsequently blocks the production of androgen in all endocrine organs, including the testes, adrenal glands, and in the prostate tumor itself [7]. In a phase III study in patients with CRPC previously treated with docetaxel, abiraterone was shown to improve overall survival by 3.9 months compared to placebo [8]

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