Effect of thalidomide on the TGFβ-1-mediated synthesis of testosterone from DHEA in prostate cancer.

141 Background: TGFβ-1 induces conversion of DHEA to testosterone in prostate cancer stromal cells. We hypothesized that thalidomide would inhibit TGFβ-1-mediated formation of testosterone from DHEA. Methods: We grew LAPC4 or LNCaP prostate cancer epithelial cells and 6S primary prostate stromal cells in mono-/co-culture with DHEA (100nM) and/or TGFβ-1 (40 or 100pM). Testosterone and PSA concentration in media were ascertained using ELISA and corrected for cell count using CCK8 (%DHEA controls). Results: TGFβ-1 and DHEA induced a dose-dependent increase in the formation of testosterone over controls (∼5-6 fold; P<0.0001). Thalidomide (100μM) inhibited the formation of testosterone in cocultured cells treated with DHEA and TGFβ-1 (40pM) by 35% (P=0.0008). The thalidomide analogues, CPS49 (10μM) and lenalidomide (10μM) also had activity; CPS49 inhibited testosterone synthesis by 54% (P=0.010) while lenalidomide reduced testosterone by 15% (P=0.011). However, only thalidomide and CPS49 decreased median PSA secretion (40% and 93% respectively; P≤0.031). Other angiogenesis inhibitors (i.e., suramin (10μM) and sorafenib (500pM)) had no effect on testosterone synthesis (P>0.05). Therefore, anti-androgen activity was not a class effect of antiangiogenesis agents. Ketoconazole also did not have activity suggesting that TGFβ-1-induced testosterone synthesis from DHEA evades standard therapies designed to inhibit androgen synthesis enzymes (i.e. CYP3A4 and CYP17 inhibitors). We assessed the phosphorylation status of TGFβ-1 pathway constituents (i.e., SMAD2/3, p38, JNK, and ERK) in cocultured cells treated as above. Thalidomide inhibits the phosphorylation of ERK without affecting total ERK levels; however, neither MEK inhibition (via U0126) nor Raf inhibition (via sorafenib) resulted in anti-androgenic effects in these cells suggesting that the canonical RAF/MEK/ERK pathway is not responsible for the difference in testosterone secretion phenotype. Conclusions: These results indicate that thalidomide and its analogues have anti-androgen activity and may explain the success of thalidomide and its analogues in clinical treatment of hormone-dependent and castration-resistant prostate cancer.