KMUP-1is aα 1A/α 1D-adrenoceptor antagonist.Previously, we have demonstrated that KMUP-1 can regulate smooth muscle tone and inhibit epithelial cell proliferation in the prostate.Prostate cancer usually progresses from an androgen-dependent stage to an androgen-independent stage.Testosterone and dihydrotestosterone exert their biological effects through prostatic epithelial and storomal cell androgen receptor (AR), which plays an important role in the initiation and progression of prostate cancer.In thisstudy, we used LNCaP (androgen-dependent) cells and injected cells subcutaneously into lateral flanks of nude mice.When tumors were established, each animal received intraperitoneal (i.p.) injection of KMUP-1 (150, 100 mg/kg) once a day for 2 months.After 2 months treatment, Tumors were excised, weighed and one part were fixed in buffered formalin and remaining stored at80℃ until further analysis.The mice receiving 100 mg/kg and 150 mg/kg KMUP-1 had a fifty percent reduction of growth, compared to the non-treated controls.The serum PSA levels in the groups treated with KMUP-1 (150 mg/kg) had an 80% greater reduction than the control groups.Immunohistochemical staining showed that the group treated with KMUP-1 (150 mg/kg) had a weaker expression of AR than the control group.Together, these results suggest that KMUP-1 inhibits tumor growth and down-regulates AR and PSA in vivo.KMUP-1 might be potentially useful in the treatment of BPH and possesses anti-tumor activity in the treatment of androgen-dependent prostate cancer.