Prostate cancer that progresses on ADT (for example, in the form of increased serum PSA, new metastasis, or progression of pre-existing metastasis) at castrate level testosterone level (<50 ng/dL) is termed castration-resistant prostate cancer (CRPC), and is characterized by changes in androgen receptor (AR) signaling [1,2,4]. This evidence concerns the gene AR and prostate cancer.