AR and prostate cancer: Tumors were classified into four phenotypic subtypes based on immunohistochemical staining for androgen receptor (AR) signaling and neuroendocrine (NE) markers as previously described (24,25): AR-active prostate cancer (ARPC or AR+/NE−), amphicrine carcinoma (AR+/NE+), double negative mCRPC (AR−/NE−), neuroendocrine prostate cancer (NEPC or AR−/NE+).