Tumor-induced Natural Killer cell dysfunction is a rapid and reversible process uncoupled from the expression of immune checkpoints

Natural Killer (NK) cells often become dysfunctional during tumor progression but the molecular mechanisms underlying this phenotype remain unclear. To explore this phenomenon, we set up new mouse lymphoma models activating or not NK cells. Both tumor types elicited IFN-I production, leading to the expression of a T cell exhaustion-like signature in NK cells, which included immune checkpoint proteins (ICPs). However, NK cell dysfunction occurred exclusively in the tumor model that triggered NK cell activation. Additionally, ICP positive NK cells demonstrated heightened reactivity compared to negative ones. Furthermore, the onset of NK cell dysfunction was swift and temporally dissociated from the induction of ICPs, which occurred as a later event during tumor growth. Finally, NK cell responsiveness was restored when stimulation was discontinued, and IL-15 had a positive impact on this reversion. Therefore, our data demonstrate that the reactivity of NK cells is dynamically controlled, and that NK cell dysfunction is a reversible process uncoupled from the expression of ICPs We used two models of tumor cells, one that do not stimulate NK cells (RMA) and the other one that strongly stimulate them (RMA-KR). Tumor cells were independently injected intraveneously in C57BL/6J mice and NK cells from RMA or RMA-KR bearing mice at different time of tumor growth (Early : Day+2 ; Intermediate : Day +4 or +7 respectively for RMA and RMA-KR ; Late : Day +9 or +14 respectively for RMA and RMA-KR), or from control mice, were sorted by flow cytometry and subjected to bulk RNAseq analysis. (n=4 for control ; n= 3 to 5 for each time point)