KLK3 and prostate cancer: 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).