Abstract 3722: In vitro induced regulatory T cells for understanding the nature of peripherally induced regulatory cells in relation to cell mediated immunotherapy for cancer

Abstract

Abstract Background: pTregs are appearing to be one of the major obstacles of cellular immunotherapy of cancer. Tumor specific in vivo induced Cytotoxic T lymphocytes (CTL) are rapidly eliminated with concomitant expansion of pTreg cells. In human melanoma in ex vivo condition, tumor antigen specific CTL generated with CD8+ cells persisted for months while ex vivo induced CTL with whole PBL stimulated with Mart-127-35 A2 (tumor antigen) pulsed autologousDC, died within three weeks. Whereas Influenza (Flu 58-66) antigen specific CTL continued to expand and remained functional beyond four weeks. Method: Peripheral blood and tumors were obtained from patients diagnosed with metastatic melanoma after informed consent. Blood derived dendritic cells, PBL, CD4+ and CD8+ cells were isolated for in vitro co-cultures with Mart-1 or Flu peptide pulsed autologous DC or autologous tumor cells. CD8+ CTL response and CD4+ positive Treg responses were measured. Freshly obtained tumor tissue derived lymphocytes (TIL) were also used for the study. Results: Our results show that CTL response against Flu survived longer in culture with total PBL than CTL response against Mart-1 in identical culture conditions. CTL response using autologous tumor cells with PBL in culture lasted for a shorter duration but growth of Treg cells were observed. Cytokine analysis with expanding Treg cells showed secretion of IL-10 upon re-stimulation with autologous DC or anti-CD3 ab. Similarly, CD4+ cells isolated from freshly obtained tumor tissue (TIL, representing in vivo condition), suppressed T cell activation and secreted high amount of IL-10 upon re-stimulation. Conclusion: These findings suggested that in vitro induced iTreg from cultures or pTreg from TILs (in vivo), work identical way, to negatively regulate effector immune response by secreting IL-10. Further analysis with iTregs for their use of metabolic pathways would be important to identify the specific signaling molecules used by autologous (person specific) pTregs , as target molecules, to block the expansion of such pTregs for the better outcome for CTL mediated immunotherapy for cancer. Citation Format: Upendra P. Hegde, Nitya G. Chakraborty. In vitro induced regulatory T cells for understanding the nature of peripherally induced regulatory cells in relation to cell mediated immunotherapy for cancer [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 3722. doi:10.1158/1538-7445.AM2017-3722