['Stromal smooth muscle cells (SMCs) play an important role in the pathogenesis and clinical symptom of benign prostatic hyperplasia. We had reported that estrogen enhances the phenotype of SMC in cultured prostate stromal cells (PRSCs). Here we further investigate the mechanism by which estrogen affects the differentiation of PRSCs.', 'Primary cultured PRSCs were stimulated with E2 or BSA-E2. The mRNA level of SMC-specific genes, smoothelin, and SM-MHC were measured by qRT-PCR. The SM-MHC protein was measured by Western blot. The mRNA and protein levels of TGF-beta1 were measured by qRT-PCR and ELISA. The MAPK inhibitor PD98059, the estrogen receptor antagonist ICI182,780 and neutralizing antibody to TGF-beta1 were used to reveal the mechanism of estrogen effect.', 'E2 and BSA-E2 significantly up-regulate the expression of SMC-specific genes in PRSCs. Both forms of estrogen could increase the expression of TGF-beta1, which can be blocked by pre-treating with PD98059. Moreover, PD98059 and TGF-beta1 neutralizing antibody could abrogate the effect of BSA-E2 on cell differentiation. However, they could only inhibit part of E2-induced SMC phenotype enhancement. ICI182,780 could partially suppress the pro-differentiation effect of E2 but had no influence on the effect of BSA-E2. Combined treatment with ICI182,780 and PD98059 can completely abrogate the effect of E2.'] Are both nongenomic and genomic effects involved in estradiol 's enhancing the phenotype of smooth muscle cells in cultured prostate stromal cells?