Abstract 2101: Ormeloxifene suppresses the growth of prostate tumor via inhibition of β-catenin induced AR signaling
Authors: Ganju Aditya , Hafeez Bilal Bin , Sikander Mohammed , Kashyap Vivek Kumar , Yallapu Murali Mohan , Chauhan Subhash C. , Jaggi Meena 
Published: July 2017

Background: Prostate cancer (PrCa) first manifests as an androgen-dependent disease and can be treated with androgen-deprivation therapy. Despite the initial success of androgen ablation therapy, resistance to anti-androgen therapy displays by progression to hormone refractory (androgen-independent) advanced stage PrCa which is primary cause of patient’s death. Main underlying cause for the onset of hormone refractory cancer is ligand independent activation of AR signaling in PrCa cells. It has been shown that β-catenin acts as a non-androgen activator of AR which enhances AR transactivation in PrCa cells. Thus, identification of agents with excellent pharmacokinetics and pharmacodynamics parameters that can inhibit ligand independent activation of AR signaling might be highly useful for the treatment of advanced stage PrCa. Herein, we identified a synthetic molecule, ormeloxifene (ORM), which efficiently represses β-catenin mediated ligand independent activation of AR signaling, thus, inhibits growth and metastatic features of PrCa cells.

Methods: Androgen-refractory but AR positive PrCa cell (C4-2) was used as an in vitro and in vivo model systems. Effect of ORM on AR and PSA protein levels was determined by Western blot analysis. Effect of ORM treatment was analyzed on AR and PSA luciferase activities by transiently transfecting the C4-2 cells by AR and PSA luciferase plasmids. Renilla construct was used as an internal control. C4-2 cells nuclear and cytoplasmic lysates were prepared using Active Motif kit. Immunoprecipitation analysis was performed to determine if ORM inhibits physical interaction of β-catenin with AR. Therapeutic efficacy of ORM was evaluated in cell lines and PrCa xenograft mouse models.

Results: ORM dose-dependently (10, 15 and 20 µM) inhibited the protein levels of AR and its downstream target protein PSA. ORM (10 and 20μM) treatment also inhibited AR transactivation as determined by decreased promoter activities of AR and its target gene PSA. ORM (10 and 20μM) treatment inhibited protein levels of nuclear β-catenin and physical interaction of β-catenin with AR in PrCa cells. ORM administration dose- dependently (intra-peritoneal; 100 and/or 500µg/mouse; thrice/week) significantly (P&lt;0.01) inhibited growth of C4-2 cells derived xenograft tumors in athymic nude mice. ORM treatment significantly (P&lt;0.01) inhibited the expressions of nuclear AR and β-catenin expressions in xenograft tumor tissues. These ORM treated mice did not show any apparent toxicity in our study.

Conclusion: Our study demonstrates that ORM is a potent inhibitor of β-catenin-mediated activation of AR signaling. Based on its safety profile, ORM might be an ideal candidate for repurposing to treat advanced stage PrCa alone or in combination with other therapies.

Citation Format: Aditya Ganju, Bilal Bin Hafeez, Mohammed Sikander, Vivek Kumar Kashyap, Murali Mohan Yallapu, Subhash C. Chauhan, Meena Jaggi. Ormeloxifene suppresses the growth of prostate tumor via inhibition of β-catenin induced AR signaling [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2101. doi:10.1158/1538-7445.AM2017-2101