Abstract 389: The dual mTOR inhibitor, AZD2014, and castration increase intra-tumoral immune cell infiltration and anti-tumour activity in a genetically engineered mouse model of prostate cancer
Authors: Sandi Chiranjeevi , Ramos-Montoya Antonio , Filisbino Sergio L. , Hughes Adina , Mosely Suzanne , Morrow Michelle , Wilkinson Robert W. , Jurmeister Sarah , Wadhwa Karan , Richards Frances M. , Jodrell Duncan I. , Cosulich Sabina , Davies Barry R. , Pacey Simon 
Published: July 2016

Background: Medical therapy for men with prostate cancer (PCa) is evolving, including recent evidence to support the use of chemotherapy for men with hormone sensitive disease. PI3K/AKT/mTOR pathway aberrations are common in patients with primary PCa and almost universal in metastatic tumours. The mTOR pathway acts as a central regulator of tumour cell metabolism, proliferation, cell cycle progression and immune regulation. The aim of this study was to investigate the effects of mTOR inhibitor AZD2014 on tumour growth and immune infiltration in a genetically engineered mouse model of PCa.

Methods: PtenL/L;PB-Cre4 mice, which developed invasive hormone-sensitive prostate tumours between 10-14 months of age, were enrolled (n = 13-15 per group) and treated with AZD2014 (15mg/Kg) or vehicle orally for 14 doses (QD 5/7) with or without castration. Tumour volumes were assessed by ultrasound imaging. Tumour samples were collected within 4 hours post 14th dose for histological and molecular analysis.

Results: AZD2014 was well tolerated, no overt toxicity was observed. Mean plasma concentrations of AZD2014 were 4.4±2.1μM at time of tumour sampling. AZD2014 alone or AZD2014+castration inhibited mTORC1 and mTORC2 activity as demonstrated by reduced p4EBP1(Thr37/46) 48%±27% (P&lt;0.001) and 37%±11% (P&lt;0.001), pS6(Ser235/236) 74%±43% (P&lt;0.001) and 44%±13% (P&lt;0.001), pAKT(Ser473) 36%±8% (P&lt;0.001) and 20%±3% (P&lt;0.01), respectively compared to vehicle-treated mice. Proliferation (Ki67+) was reduced in AZD2014-treated tumours by 70%±45% (P&lt;0.001) and AZD2014+castration by 42%±16% (P&lt;0.001). Apoptosis (CC3+) was increased in AZD2014 and AZD2014+castration groups by 3.3-fold (both, P&lt;0.001) or castration only group by 2-fold (P&lt;0.001). Tumour volumes were significantly reduced (54%, p&lt;0.05) in AZD2014+castration group. Castration induced increased infiltration of T cells (CD3+, 2-fold, P&lt;0.001) and macrophages (F4/80+, 1.6-fold, P&lt;0.001) in the tumour tissues. These effects were more pronounced when combined with AZD2014 (CD3+, 2.8-fold, P&lt;0.001; F4/80+, 2.3-fold, P&lt;0.001). Multi-channel flow cytometry has confirmed increased proliferation of CD45+, CD3+ and CD8+ cells in tumours from the AZD2014+castration group.

Conclusion: These data confirm the anti cancer effect of AZD2014 in this PCa model. Furthermore, AZD2014+castration was more effective than either treatment as a single agent. The increased intra-tumoral T cell infiltration observed may have contributed to the anti-tumour effect. Further studies are ongoing to maximise this therapeutic effect and will inform current clinical studies in men with hormone sensitive, high risk prostate cancer.

Citation Format: Chiranjeevi Sandi, Antonio Ramos-Montoya, Sergio L. Filisbino, Adina Hughes, Suzanne Mosely, Michelle Morrow, Robert W. Wilkinson, Sarah Jurmeister, Karan Wadhwa, Frances M. Richards, Duncan I. Jodrell, Sabina Cosulich, Barry R. Davies, Simon Pacey. The dual mTOR inhibitor, AZD2014, and castration increase intra-tumoral immune cell infiltration and anti-tumour activity in a genetically engineered mouse model of prostate cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 389.