Mitochondrial Ca2+ transport-dependent intercellular crosstalk between CD8 T and natural killer cells prevents tumor development and escape

Abstract Unraveling the complexity of lymphocyte interactions is key to understanding immune network and improving cancer immunotherapy. By designing various adoptive cell transfer protocols in solid tumors established in RAG−/−, RAG−/−gc−/− and RAG−/−GzmB-Tom mice and tracing lymphocytes specific to a self-tumor antigen P1A encoded by an X-linked cancer-germline gene Trap1a, we explored the functional dynamics between T and NK cells. We found that activated CD8+T cells augmented NK cell effector function in a pre-tumor T cell protocol that prevented the development of antigen-escape tumor variants. Using a silica nanofiber 3D matrix to control cellular mobility, confocal imaging showed intercellular contacts of activated CD8+T cells (CD69highCD25high) with multiple naïve NK cells, while naïve CD8+T cells formed single or no contact with NK cells. This interaction led to crossregulation of mitochondrial Ca2+ (mitoCa2+) oscillations in both cells whereby activated CD8+T cells induced differentiation of NK cell effector phenotype and NK cells polarized CD8+T cells towards a central memory phenotype. Intracellularly, CD8+T cells increased JAK1, JAK3, TYK2, STAT2 and STAT6 phosphorylation and oxidative signaling in NK cells. In turn, NK cells restrained IL-2 signaling in CD8+T cells by dampening activation-induced STAT5-dependent expression of IL-2-receptor-a chain. These effects were abrogated following the blockade of mitoCa2+ uptake. Mice deficient in mitoCa2+ handling-regulatory gene Fus1 showed increased incidence of a range of spontaneous sarcomas, lymphomas and leukemia. Data suggest that mitoCa2+ transport-guided intercellular crosstalk between CD8+T and NK cells is critical to prevent tumor development and escape.