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Background: Both enzalutamide and abiraterone have demonstrated improved radiographic progression-free and overall survival for castration-resistant prostate cancer (CRPC) compared with placebo controls before docetaxel treatment in phase III studies. These oral agents target androgen and androgen receptor signaling and are thought to be less toxic than chemotherapy. Cross-resistance to these agents was recently reported because of their similar mechanism of action, and it is important to assess which agent is more effective to use initially for CRPC.Methods/design: The present study is a phase III, investigator-initiated, multicenter, head-to-head, randomized controlled trial investigating enzalutamide vs. abiraterone as a first-line treatment for CRPC patients. Patients will be randomly assigned to an enzalutamide or an abiraterone treatment group. The primary endpoint is the time to prostate-specific antigen progression. The target sample size is set at 100 patients per group (total, 200 patients). The study duration is 5 years, and the duration for recruitment is 2 years and 6 months.Discussion: Thus far, there have been no prospective head-to-head studies comparing enzalutamide and abiraterone. This ENABLE study will clarify which agent should be prioritized for CRPC patients and enable clinicians to decide the appropriate treatment before chemotherapy.Trial Registration: University hospital Medical Information Network (UMIN) Center identifier UMIN000015529 . Registrated 11/1/2014. [ABSTRACT FROM AUTHOR]

Activation of tumor-stromal interactions is considered to play a critical role in the promotion of tumorigenesis. To discover new therapeutic targets for hormone-refractory prostate tumor growth under androgen ablation therapy, androgen-sensitive LNCaP cells and the derived sublines, E9 (androgen-low-sensitive), and AIDL (androgen-insensitive), were recombined with androgen-dependent embryonic rat urogenital sinus mesenchyme (UGM). Tumors of E9 + UGM and AIDL + UGM were approximately three times as large as those of LNCaP + UGM. Tumors grown in castrated hosts exhibited reduced growth as compared with those in intact hosts. However, in castrated hosts, E9 + UGM and AIDL + UGM tumors were still approximately twice as large as those of LNCaP + UGM. Cell proliferation in tumors of E9 + UGM and AIDL + UGM grown in castrated host, was significantly higher than that in tumors of LNCaP + UGM. In vitro, expression of fibroblast growth factor (FGF)-2 and IGF-I, but not FGF-7 mRNA, was significantly reduced in UGM under androgen starvation. In cell culture, E9 cells were responsive to FGF-2 and FGF-7 stimulation, while AIDL responded to FGF-7 and IGF-1. Expression of FGFR1 and FGFR2 was considerably higher in E9 than those in LNCaP, similarly expression of FGFR2 and IGF-IR were elevated in AIDL. These data suggest that activation of prostate cancer cell growth through growth factor receptor expression may result in the activity of otherwise androgen-independent stromal growth factor signals such as FGF-7 under conditions of androgen ablation. [ABSTRACT FROM AUTHOR]