Abstract PR10: Enhancing the efficacy of T cell-based immunotherapies using miR-155 engineered tumor-specific CD8+ T cells

Abstract

Abstract Lymphodepleting regimens are employed prior to adoptive immunotherapy to augment the antitumor efficacy of transferred T cells by removing endogenous homeostatic cytokine sinks. These conditioning modalities, however, are often associated with severe toxicities. We found that miR-155 enabled B16 melanoma-specific CD8+ T cells to mediate profound antitumor responses in lymphoreplete hosts that were not potentiated by immune-ablation. miR-155 enhanced T cell responsiveness to limited amounts of homeostatic γc cytokines by restraining the expression of the Akt inhibitor Ship1 and multiple negative regulators of Stat5, such as Socs1 and Ptpn2, resulting in delayed cellular contraction and sustained cytokine production. To translate these findings into new clinical trials, we tested whether the overexpression of miR-155 in human T cells would enhance the antitumor efficacy of CD19-specific chimeric antigen receptor (CD19-CAR) cells against systemic acute lymphoblastic leukemia xenografts. As a safety measure, the suicide gene, inducible caspase 9, was included in the miR-155 construct. We found that miR-155 also augmented the antitumor efficacy of T cells in this xenograft tumor model. Recapitulating our findings in mouse cells, human T lymphocytes overexpressing miR-155 showed increased Stat5 signaling and enhanced survival. Our results indicate that overexpression of miR-155 in tumor-specific T cells can be employed to increase the effectiveness of adoptive immunotherapies in a cell intrinsic manner without the need of life-threatening, lymphodepleting maneuvers. This abstract is also being presented as Poster A82. Citation Format: Yun Ji, James Hocker, Jinhui Hu, Sanjivan Gautam, Neal Lacey, Luca Gattinoni. Enhancing the efficacy of T cell-based immunotherapies using miR-155 engineered tumor-specific CD8+ T cells. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2016 Oct 20-23; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2017;5(3 Suppl):Abstract nr PR10.