BACKGROUND Androgens and the androgen receptor (AR) play critical roles in the prostate development via mesenchymal-epithelial interactions. Smooth muscle cells, differentiated from mesenchyme, are one of the basic components of the prostate stroma. However, the roles of smooth muscle AR in prostate development are still obscure. METHODS We established the smooth muscle selective AR knockout (SM-ARKO) mouse model using the Cre-loxP system, and confirmed the AR knockout efficiency at RNA, DNA and protein levels. Then we observed the prostate morphology changes, and determined the epithelial proliferation, apoptosis, and differentiation. We also knocked down the AR in a prostate smooth muscle cell line (PS-1) to confirm the in vivo findings and to probe the mechanism. RESULTS The AR was selectively and efficiently knocked out in the anterior prostates of SM-ARKO mouse. The SM-ARKO prostates have defects with loss of infolding structures, and decrease of epithelial proliferation, but with little change of apoptosis and differentiation. The mechanism studies showed that IGF-1 expression level decreased in the SM-ARKO prostates and AR-knockdown PS-1 cells. The decreased IGF-1 expression might contribute to the defective development of SM-ARKO prostates. CONCLUSIONS The AR in smooth muscle cells plays important roles in the prostate development via the regulation of IGF-1 signal.

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Our data suggests that the VES derivative, TOB, is effective in inhibiting prostate cancer cell proliferation, suggesting that TOB could be used for both chemopreventive and chemotherapeutic purposes in the future.