Physical Crosstalk Between Cd8(+)T And Natural Killer Cells Elicits Antitumor Effector Response

The interaction between the innate and adaptive immune components is fundamental for an effective antitumor immunity. Our studies in murine solid tumor models showed that productive antitumor effector response relies on functional crosstalk between innate immune effectors—natural killers (NK), and adaptive immune effectors—cytolytic CD8+T lymphocytes. We found that this lymphocyte cooperativity between CD8+T and NK cells can prevent the development of antigen-escape tumor variants. In this study, we first investigated the role of physical contacts in during the functional crosstalk between CD8+T and NK cells. Since, studying dynamic lymphocyte interactions present extreme challenges, in this study, we engineered a 3D nanofiber matrix to provide lymphocytes a 3D culture environment for a controlled interaction. Confocal imaging showed that CD3/CD28-activated CD8+T cells (CD69+CD25+) formed multiple intercellular contacts with several naive NK cells upon coculture, while naive CD8+T cells made single or no contact with NK cells. In lymphocyte coculture (physical contact possible) we found that activated CD8+T and NK cells cross-regulate each other phenotype wherein NK cells polarize activated CD8+T cells towards “T central memory phenotype” and activated CD8+T lymphocytes induce acquisition of “effector/regulatory phenotype” by naive NK cells. This cross-regulation of lymphocytes disappeared in trans-well system (no physical contact) indicating the necessity of cell-to-cell physical interaction during CD8+T—NK crosstalk. Notably, intercellular physical interaction led to cross regulation of mitoCa2+ oscillations in both activated CD8+T and NK cells. Inhibition of mitochondrial Ca2+ uptake or Na+/Ca2+ exchanger with Ru360 and CGP37157, respectively, mimicked observed alterations in both lymphocytes. Further, NK cells displayed increased oxidative signaling, Tyk2, Jak 1 and 3, Stat2 and Stat6 phosphorylation while inhibiting TCR- and various cytokine receptors-mediated signaling. In turn, NK cells selectively restrain IL-2 signaling in CD8+T cells by dampening activation-induced up-regulation of CD25, Stat5 phosphorylation, IL-2 synthesis and elevation in IL-2 uptake. These data underscore a novel mitochondrial Ca2+ transport-regulated acquisition of activation/regulatory phenotype by NK and CD8+T cells upon their interaction. Understanding the critical factors involved in this NK—CD8+T cells immunological synapse allowing their functional remodeling with the intact tissues in tumor settings will lead to novel strategies for effective cancer immunotherapies, with a potential of relapse-free survival in cancer patients. Citation Format: Roman V. Uzhachenko, Ashutosh Singhal, Shawn J. Goodwin, William H. Hofmeister, Anil Shanker. Physical crosstalk between CD8+T and natural killer cells elicits antitumor effector response [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 5665. doi:10.1158/1538-7445.AM2017-5665