Mutations in the
androgen receptor (AR) that enable activation by
antiandrogens occur in
hormone-refractory
prostate cancer, suggesting that mutant ARs are selected by treatment. To validate this hypothesis, we compared AR variants in
metastases obtained by rapid autopsy of patients treated with
flutamide or
bicalutamide, or by excision of
lymph node metastases from
hormone-naïve patients. AR mutations occurred at low levels in all specimens, reflecting genetic heterogeneity of
prostate cancer. Base changes recurring in multiple samples or multiple times per sample were considered putative selected mutations. Of 26 recurring missense mutations, most in the NH(2)-terminal domain (NTD) occurred in multiple
tumors, whereas those in the
ligand binding domain (LBD) were case specific.
Hormone-naïve
tumors had few recurring mutations and none in the LBD. Several AR variants were assessed for mechanisms that might underlie treatment resistance. Selection was evident for the promiscuous receptor AR-V716M, which dominated three
metastases from one
flutamide-treated patient. For the inactive cytoplasmically restricted splice variant AR23, coexpression with AR enhanced
ligand response, supporting a decoy function. A novel NTD mutation, W435L, in a motif involved in intramolecular interaction influenced promoter-selective, cell-dependent transactivation. AR-E255K, mutated in a domain that interacts with an
E3 ubiquitin ligase, led to increased protein stability and nuclear localization in the absence of
ligand. Thus, treatment with
antiandrogens selects for gain-of-function AR mutations with altered stability, promoter preference, or
ligand specificity. These processes reveal multiple targets for effective
therapies regardless of AR mutation.