NK Cell Priming From Endogenous Homeostatic Signals Is Modulated by CIS

Abstract

Natural killer (NK) cell activation is controlled by a balance of activating and inhibitory signals and cytokines such as IL-15. We previously identified cytokine-inducible SH2-containing protein (CIS) as a negative regulator of IL-15 signaling in NK cells under inflammatory conditions. While the functional effect of Cish-deficiency in NK cells was obvious by their increased anti-tumor immunity and hyper-proliferative response to IL-15, it remained unclear how CIS regulates NK cell biology in steady-state. Here, we investigated the role of CIS in the homeostatic maintenance of NK cells and found CIS-ablation promoted terminal differentiation of NK cells and increased turnover, suggesting that under steady-state conditions, CIS plays a role in maintaining IL-15 driven regulation of NK cells in vivo. However, hyper-responsiveness to IL-15 did not manifest in NK cell accumulation, even when the essential NK cell apoptosis mediator, Bcl2l11 (BIM) was deleted in addition to Cish. Instead, loss of CIS conferred a lower activation threshold, evidenced by augmented functionality on a per cell basis both in vitro and in vivo without prior priming. We conclude that Cish regulates IL-15 signaling in NK cells in vivo, and through the rewiring of several activation pathways leads to a reduction in activation threshold, decreasing the requirement for priming and improving NK cell anti-tumor function. Furthermore, this study highlights the tight regulation of NK cell homeostasis by several pathways which prevent NK cell accumulation when IL-15 signaling and intrinsic apoptosis are dysregulated.

Targeting CISH enhances natural cytotoxicity receptor signaling and reduces NK cell exhaustion to improve solid tumor immunity

“…Cish -deficient cells are terminally mature and we did not observe any differences in NK cell development in NK cells isolated from Cish fl/fl Ncr1 iCre mice compared to WT NK cells. This is contrasting with the maturation defect and DNAM-1 over expression that was found on germline CISH-deleted NK cells 13 . We believe that CISH regulates theses receptors expression processes at an earlier NK cell stage prior to NKp46 expression.…”

“…Targeting inhibitory intracellular proteins, such as CISH, a member of the SOCS (Suppressor of Cytokine Signaling) family, can be effective in enhancing CD8 + T cell tumor immunity in preclinical models 10, 11 these studies led to a clinical protocol NCT04426669. CISH has been also shown to be a critical immune checkpoint in NK cells 12 and we recently contributed to show the importance of CISH in NK cell homeostasis using a Cish KO germline mouse model 13 . However, we still do not fully appreciate mechanistically how CISH regulates NK anti-tumor functions.…”

Drug target validation in primary human natural killer cells using CRISPR RNP

“…11 In addition to numerous soluble factors, it is the balance of signals transduced through these receptors that also dictates whether an NK cell engages in a cytotoxic attack against a target cell. We previously described CIS (encoded by Cish) as a potent checkpoint in NK cell activation by limiting IL-15 signal transduction, 12,13 while CBL-B (Cblb) has also been proposed as an intracellular repressor of NK cell activation. 14 addition, the group of Mantovani described IL-1R8 (Il1r8) acting as a negative regulator of IL-18 responsiveness in NK cells 15 while more recently, TIGIT (Tigit) was shown to be a major inhibitory receptor on NK cells 16 with deletion of Cish, Cblb, Il1r8, or Tigit resulting in dramatically improved NK cell-dependent antitumor immunity.…”

Transcription Factors Associated With IL-15 Cytokine Signaling During NK Cell Development

“…SH2containing protein (CIS, encoded by Cish gene) directly interacts with JAK1 to mediate the inhibition of its enzymatic activity and proteasomal degradation, thereby constraining JAK-STAT5 signaling. Consistently, mice with CIS ablation exhibit accumulation of terminally differentiated CD27 − CD11b + NK cells in the BM and spleen, which is associated with the hyperresponsive nature of NK cells to IL-15 (114). By directly interacting with JAK2, SOCS2 attenuated JAK2 activity and the corresponding JAK2-STAT5 signaling to negatively regulate NK cell differentiation (91).…”