Abstract 4535: Thalidomide inhibits the TGFβ-mediated synthesis of testosterone from DHEA in prostate cancer
Authors: Tristan M. Sissung, C. Tyler Kirkland, Kelie Reece, Julia Tyler Arnold, William D. Figg
Journal: Cancer Research (2011)

Abstract Recent studies suggest that TGFβ-1 induces formation of reactive stroma and conversion of DHEA to testosterone in prostate cancer stromal cells. We hypothesized that thalidomide would inhibit this process through its anti-inflammatory activity. To this end, we grew LAPC-4 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). The Wilcoxon rank-sum test was used for analysis of testosterone data, while given high inter-experimental variance in PSA data, the Wilcoxon signed-rank test was employed. DHEA induced an approximate 4-fold median increase in the formation of testosterone over untreated cocultured cells while TGFβ-1 induced a further dose-dependent increase in the formation of testosterone (∼5-6 fold; P&amp;lt;0.0001). Thalidomide (100μM) inhibited the formation of testosterone in cocultured cells treated with DHEA and TGFβ-1 (40pM) by 35% (5.2 versus 3.4 ng/mL; P=0.0008). The thalidomide analogues, CPS49 (10μM) and lenalidomide (CC5013; (10μM)) also had activity; CPS49 inhibited testosterone synthesis by 54% (5.2 versus 2.4 ng/mL; P=0.010) while lenalidomide reduced testosterone by 15% (5.2 versus 4.4 ng/mL; P=0.011) in cocultured cells. However, only thalidomide and CPS49 decreased median PSA secretion (a marker of LAPC-4 androgen receptor transcription; 2.0 to 1.2ng/mL (40%), and 2.0 to 0.15ng/mL (93%) respectively; P≤0.031). Interestingly, other angiogenesis inhibitors (i.e., suramin (10μM) and sorafenib (500pM)) had no effect on testosterone synthesis (P&amp;gt;0.05). Therefore, anti-androgen activity was restricted to thalidomide analogues in cocultured cells and was not related to other studied 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). To establish a putative mechanism of thalidomide activity in this system, we assessed the total protein levels and phosphorylation status of TGFβ-1 pathway constituents (i.e., SMAD2/3, p38, JNK, and ERK) in cocultured cells treated as above. The results revealed that 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. 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. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4535. doi:10.1158/1538-7445.AM2011-4535