[Effects of 4-hydroxytamoxifen on prostate smooth muscle cells: an in vitro experiment].

Objective: To investigate the effects of 4- hydroxytamoxifen (OHT) on the proliferation and apoptosis of prostate smooth muscle cells and the expression of estrogen receptor (ER) and androgen receptor (AR).

Methods: Prostate smooth muscle cells were isolated from the resected specimens of prostate glands of 10 patients with benign prostatic hypertrophy (BPH), cultured, and exposed to estradiol (E(2)), diethylstilbestrol (DES), and OHT of different concentrations (1 x 10(-8) - 1 x 10(-5) mol/L) or mixture of E(2) (1 x 10(-8) - 1 x 10(-6) mol/L) with OHT (1 x 10(-7) mol/L). Flow cytometry was used to test the proliferation and apoptosis of the cells, and immunocytochemistry was used to test the expression of estrogen and androgen receptors.

Results: E(2) and DES promoted the proliferation of the prostate smooth muscle cells in a certain concentration range, but not dose-dependently, and OHT at the concentration of 1 x 10(-8) mol/L slightly increased the G(2)-M peak rate of the prostate smooth muscle cells, but suppressed the G(2)-M peak rate dose-dependently when its concentration was >or= 1 x 10(-7) mol/L (P < 0.05) and this suppression effect was dose-dependently (r = -0.312, P = 0.011). E(2) at the concentration >or= 1 x 10(-5) mol/L and DES at the concentration >or= 1 x 10(-6) mol/L slightly promoted the apoptosis of the prostate smooth muscle cells, but not dose-dependently, and OHT at the concentrations from 1 x 10(-8) mol/L to 1 x 10(-5) mol/L promoted the apoptosis of the prostate smooth muscle cells dose-dependently (r = 0.363, P = 0.021) and this effect could not be reversed by administration of E(2) at the concentration 1 x 10(-8) - 1 x 10(-6) mol/L (P > 0.05). E(2), DES, and OHT of different concentrations all increased the ERalpha and AR positive staining rates of the prostate smooth muscle cells (all P < 0.05).

Conclusions: OHT suppresses the proliferation and promotes the apoptosis of prostate smooth muscle cells, and these functions do not depend on the estrogen receptor pathway. Low blood OHT concentration after oral administration of TAM and up-regulation of estrogen receptors by OHT may be the caused of the inefficiency of TAM for treatment of BPH.