Tumor antigen-specific T cell and natural killer (NK) cell collaboration is indispensable for the elimination of tumor cells, including antigen-deficient tumor escape variants before metastasis. While mechanistic details are available for the innate instruction of T lymphocyte responses, little is known for the adaptive control of NK cell activity. We observed in a mouse model of mastocytoma expressing a self tumor antigen P1A that effector CD8+T cells provided a necessary “help” to dormant NK cells in eliciting their antitumor effector function. Bioluminescence imaging of mastocytoma tumors following adoptive transfer of P1A-specific T cells in RAG-/- and RAG-/-gamma chain-/- mice showed that NK cell anti-tumor activity requires cytolytic T cells, whereas T cells can function independent of NK cells. The goal of present study was to dissect the molecular mechanisms underlying functional cross-talk between activated CD8+T lymphocytes and naïve NK cells. In 2D and 3D co-culture systems, we observed that activated CD8+T cells form multiple intercellular contacts with naïve NK lymphocytes. Moreover, co-culture of activated T cells with naïve NK cells results in the selective down-regulation of CD25 molecule in T cells while elevating CD25 and CD69 expression on naïve NK cells. Further, CD8+T and NK cells cross-regulate their mitochondrial homeostasis including calcium transport. This effect is dependent on both cytokines and intercellular contacts, and partially involves natural killer group 2 member D (NKG2D) receptor activation. Data also indicate that activated CD8+T cells may exchange mitochondria and activation molecules such as CD25 and CD69 with naïve NK cells. Alterations in phosporylation status of multiple signaling proteins during CD8+T-NK interaction suggest a cellular remodeling whereby NK cells shift activated CD8+T cells towards T central-memory (TCM) phenotype and activated CD8+T lymphocytes alter the naïve state of NK cells towards effector/regulatory phenotype. Inhibition of mitochondrial Ca2+ uptake (mCU) or Na+/Ca2+ exchanger (mNCE) with Ru360 and CGP37157, respectively, mimicked observed alterations in CD8+ T and NK cell phenotypes upon their interaction. These results highlight a novel role of mitochondrial Ca2+ homeostasis in the re-modeling of memory differentiation and activation signaling of interacting CD8+T cells and NK cells, respectively. Improved mechanistic understanding of CD8+T-NK interplay will help refine cellular immunotherapy approach against cancer.

Citation Format: Roman V. Uzhachenko, J Shawn Goodwin, Lino Costa, Alexander Terekhov, Menaka C. Thounaojam, William H. Hofmeister, Anil Shanker. Mitochondrial Ca2+ transport fine-tunes functional cross-talk between antitumor CD8+T lymphocytes and natural killer cells. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B45.