In this study we propose to circumvent HLA-E/NKG2A mediated Natural Killer (NK) cell inhibition by suppression of NKG2A, to enhance cytotoxicity of ex vivo expanded NK cells. One mechanism employed by tumor cells to evade immunosurveillance is through induction of the surface expression of unconventional HLA ligands that agonize inhibitory receptors on immune cells. Specifically on some tumors, HLA-E is either expressed or its expression is known to be induced by IFNγ and is indicative of resistance to immunotherapy. HLA-E agonizes the CD94/NKG2A inhibitory complex on NK cells and some T cells to lessen their cytotoxicity, potentially decreasing the efficacy of cellular therapy with these immune cells. The CD94/NKG2A inhibitory complex is in balance with CD94/NKG2C stimulatory complex. HLA-E binds both of these complexes and the cytolytic activity of NK cells is influenced by the relative ratios of CD94 complexed to NKG2A or NKG2C. Thus, altering the ratio to increase NKG2C will increase NK cell cytotoxicity. In this study we show that NK cells ex vivo expanded with PM21-particle technology are highly cytotoxic and have elevated expression of NKG2A. These expanded NK cells also secrete high levels of IFNγ, inducing expression of HLA-E in tumor cells. To increase the cytotoxic potential of these ex vivo expanded NK cells, the potential to form CD94/NKG2A inhibitory complex was suppressed by either antibody blockade of NKG2A or deletion of the NKG2A gene by CRISPR/Cas9 editing. Cytotoxicity of NK cells against a lung cancer cell line stably expressing HLA-E were determined by kinetic live-cell imaging. Multiple NK cell:target (NK:T) ratios were used to show an increase in cytotoxicity over control NK cell conditions (alone or with isotype control) in the presence of NKG2A blocking antibodies with 39% increase observed at 1:10 NK:T ratio at 96h with anti-NKG2A and 56% increase with NKG2A knockout NK cells. These data suggest that blockade of CD94/NKG2A complex can improve cytotoxic activity of ex vivo expanded NK cells and could provide a promising effector population with the potential for enhanced therapeutic efficacy.

Citation Format: Tayler J. Croom-Perez, Liza D. Robles-Carrillo, Thomas A. Dieffenthaller, Alicja J. Copik. Suppression of NKG2A mediated inhibition in ex vivo expanded natural killer cells increases their cytotoxicity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2819.