Because AR regulates 5α-reductase expression in a cell type–dependent manner, we would not expect to prevent prostate cancer in all men by administering finasteride (a specific SRD5A2 inhibitor) or dutasteride (an inhibitor of both SRD5A1 and SRD5A2); this concurs with the results of the PCPT and REDUCE trials. This evidence concerns the gene AR and prostate cancer.