Abstract LB337: Inhibition of the E3 ligase CBL-B enhances the effector function and proliferation of natural killer cells

Abstract

Abstract The E3 ubiquitin ligase CBL-B is a master regulator of effector T cells through its downstream regulation of T-cell receptor and co-stimulatory stimulation, but it has also been shown to play a negative feedback role in NK cells. CBL-B depletion enhances the production of IFNγ and the cytotoxicity of activated NK cells. Similar to the effect of depleting CD8 T cells in mice, depletion of NK cells abolishes the tumor growth delay observed in Cbl-b-/- mice. With emerging data supporting the potential role of exogenous NK cells in anti-tumor immunity, inhibition of CBL-B represents a promising approach to enhance both adaptive and innate immunity for cancer immunotherapy. Using one of our small molecules, allosteric CBL-B inhibitors, HOT-A, we demonstrated that CBL-B inhibition enhanced NK activation, IFNγ production and granzyme B secretion in response to the various stimulation conditions, including cytokines (such as IL-15 and IL12 + IL-18) and stimulatory receptors (such as NKp30 and NKG2D + CD244). NK cell proliferation was also enhanced in the presence of HOT-A. Single cell analysis further suggested that HOT-A increased NK polyfunctional cytokine expression during IL-12 + IL-18 activation. In a coculture system of NK cells and K562 target cells, HOT-A dose-dependently promoted primary human NK cell activation, cytokine production and cytotoxicity in the K562 cells. In the in vivo CT-26 tumor model, granzyme B+ NK cells in the TIL were significantly increased in the HOT-A treated tumor bearing mice and NK function gene signature was also increased by Nanostring analysis, suggesting an enhanced NK function in the tumor microenvironment. Taken together, the pre-clinical data presented here demonstrate that our CBL-B inhibitor enhances NK cell function in vitro and in vivo, suggesting that its enhancement of anti-tumor immunity may be driven through both effector T cell and NK cell-driven biology. Citation Format: Yilin Qi, Jun Kuai, Yingzhi Bi, David Greco, Samira Jaeger, Ken Carson, Hadi Danaee, Timothy Reilly, Geraldine Harriman, Fang Wang. Inhibition of the E3 ligase CBL-B enhances the effector function and proliferation of natural killer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB337.