Tamoxifen, a partial ER agonist/antagonist or a selective ER modulator, completely blocked the DHT-induced cell proliferation in HAECs, but did not affect the DHT-induced cell proliferation and PSA expression in prostate cancer cells, which could partially explain the ineffectiveness of tamoxifen in the treatment of prostate cancer in clinical trials (16,34). This evidence concerns the gene ESR1 and Familial prostate cancer.