Antitumor immunity is defective in T cell-specific microRNA-155-deficient mice and is rescued by immune checkpoint blockade [Immunology]

MicroRNA-155 (miR-155) regulates antitumor immune responses. However, its specific functions within distinct immune cell types have not been delineated in conditional knockout (KO) mouse models. In this study, we investigated the role of miR-155 specifically within T cells during the immune response to syngeneic tumors. We found that miR-155 expression within T cells is required to limit syngeneic tumor growth and promote interferon gamma (IFNγ) production by T cells within the tumor microenvironment. Consequently, we found that miR-155 expression by T cells is necessary for proper tumor-associated macrophage (TAM) expression of IFNγ-inducible genes. We also found that immune checkpoint-blocking (ICB) antibodies against programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4) restored antitumor immunity in miR-155 T cell-conditional KO (TCKO) mice. We noted that these ICB antibodies rescued the levels of IFNγ; expressing T cells, expression of multiple activation and effector genes expressed by tumor-infiltrating CD8+ and CD4+ T cells, and TAM activation. Moreover, the ICB approach partially restored expression of several de-repressed miR-155 targets in tumor-infiltrating, miR-155 deficient CD8+ T cells, suggesting that miR-155 and the ICB regulate overlapping pathways to promote antitumor immunity. Taken together, our findings highlight miR-155s multifaceted role in T cells in which it promotes antitumor immunity. These results suggest that the augmentation of miR-155 expression could be used to improve anticancer immunotherapies.

from # All Medicine by Alexandros G. Sfakianakis via Alexandros G.Sfakianakis on Inoreader http://ift.tt/2ya6qmq
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