Abstract 4690: FoxP3+T cells program/re-program the prostatic tumor microenvironment

Foxp3+ T cells play a critical role in maintaining immunological tolerance by regulating functions of other immune cells, thus preventing autoimmunity. Previous studies have demonstrated the importance of Foxp3+ T cells in the tumor, however, the role increasingly recruited FoxP3+ T cells in the programming of prostatic tumor microenvironment is not well illustrated. Therefore, in this study, we have investigated the role of Foxp3+ T cells in the prostatic tumor microenvironment with the notion that increased Foxp3+ T cells facilitate tumor growth. To accomplish this, we carried out tumor induction studies in C57/BL-6 mice using transgenic adenocarcinoma of mouse prostate (TRAMP cell lines: -C1, -C2 and -C3) as tumor models. Mice were administered with TRAMP (C1-3) cells using the Matrigel system. TRAMP-C3 cells are non-tumorigenic while TRAMP-C1 and TRAMP-C2 cells form tumors. Mice were sacrificed by cervical dislocation when tumor sizes reached ~18-20mm in diameter. To prepare single cell suspension, spleen and tumor were dissected out and cells were stained with various cell surface as well as intracellular immune markers to determine the number of Foxp3+ T cells and other immune cells in the prostatic tumor microenvironment. Our findings suggest that the high number of Foxp3+ T cells was found in the spleen and tumor of TRAMP-C1 and TRAMP-C2 mice than the spleen and tiny tumor of TRAMP-C3 mice. Furthermore, the number of cytotoxic T lymphocytes and NK cells were also observed to be low in the tumorigenic TRAMP-C1 and -C2 mice as compared to non-tumorigenic mice (TRAMP-C3). Therefore, our findings suggest that the number of Foxp3+ T cells may play a critical role in shaping the prostatic tumor microenvironment. Citation Format: Sanjay Kumar, James Stoke III, Shalie Malik, Udai P. Singh, Selvarangan Ponnazhagan, Upender Manne, Manoj K. Mishra. FoxP3+T cells program/re-program the prostatic tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4690.