To identify genomic modifiers of sensitivity to AR therapy, we constructed a pooled small hairpin RNA (shRNA) library targeting genes most frequently deleted in primary or metastatic prostate cancer, then screened for resistance to enzalutamide in a well-credentialed enzalutamide-sensitive xenograft model (Arora et al., 2013, Tran et al., 2009). The gene discussed is AR; the disease is metastatic prostate carcinoma.