The invention concerns two classes of differentially regulated genes: 1) genes that are more highly expressed in prostate cancer cells treated with testosterone than in untreated prostate cancer cells; and 2) genes that are more highly expressed in prostate cancer cells treated with bicalutamide, an anti-androgenic compound, than in untreated prostate cancer cells. Disclosed are methods for selecting and monitoring the effectiveness of therapeutic agents used for the treatment of prostate cancer. Also disclosed are methods for identifying novel therapeutic agents for the treatment of prostate cancer and methods and compositions for preventing, treating, and diagnosing prostate cancer.