In agreement with other studies of patient-derived xenografts, MDA-PCa-133 displayed similar complex tumor adaptation characteristics of those that occur in the absence of circulating testosterone, including increased expression of CYP17A1, wild-type full length AR and its ligand-independent variant AR-V7, and a gain-of-function mutation in the full-length AR ligand-binding domain sequence (H874Y)10, 14, 15. The gene discussed is AR; the disease is neoplasm.