Constitutively Active Androgen Receptor Variant Detected in a Human Prostate Cancer

Human androgen receptor (AR) mutation is a possible alternative used by prostate adenocarcinoma (PCA) cells to escape androgen dependence. These mutations may broaden the specificity and/or the sensitivity of the AR to other hormones, resulting in the inappropriate receptor activation, and thus, affecting the PCA response to hormonal therapies. We have developed a yeast-based functional assay to detect mutant ARs in PCA by analyzing their transactivation capacities in response to different ligands. We report herein the detection of two different mutant ARs within the same metastatic tumor sample. Concomitantly to the T877A mutant AR, we identified an additional double mutant AR harboring the nonsense mutation Q640Stop, just downstream of the DNA binding domain together with the T877A point mutation. This mutation leads to a C-terminal truncated AR. This study is the first description of this type of mutation in PCA. We demonstrated that this truncated AR exhibited constitutive transactivation properties. In conclusion, our data suggest that mutation-induced constitutive activation of the AR may be an alternative mechanism used by PCA cells to escape androgen deprivation.