Inhibition of the tyrosine kinase GSK 3 during IL-15-driven ex vivo expansion of natural killer (NK) cells enhanced the acquisition of a mature NK phenotype, as defined by the increased expression of CD57, T-BET, ZEB2, and BLIMP-1. Cells expanded in this way produced more TNF and IFN-γ in response to target cell recognition, showed enhanced antibody-dependent cellular cytotoxicity, and were more effective against ovarian cancer in murine xenograft models, prompting initiation of a clinical trial.
Maturation of human natural killer cells (NK cells) as defined by accumulation of cell surface expression of CD57 is associated with increased cytotoxic character and TNF and IFN-gamma production upon target cell recognition. Notably, multiple studies point to a unique role for CD57+ NK cells in cancer immunosurveillance, yet there is scant information about how they mature. In this study, we show that pharmacological inhibition of GSK3 kinase in peripheral blood NK cells expanded ex vivo with IL-15 greatly enhances CD57 upregulation and late-stage maturation. GSK3 inhibition elevated the expression of several transcription factors associated with late-stage NK cell maturation including T-BET, ZEB2 and BLIMP-1 without affecting viability or proliferation. When exposed to human cancer cells, NK cell expanded ex vivo in the presence of a GSK3 inhibitor exhibited significantly higher production of TNF and IFN-gamma, elevated natural cytotoxicity, and increased antibody-dependent cellular cytotoxicity (ADCC). In an established mouse xenograft model of ovarian cancer, adoptive transfer of NK cells conditioned in the same way also displayed more robust and durable tumor control. Our findings show how GSK3 kinase inhibition can greatly enhance the mature character of NK cells most desired for effective cancer immunotherapy.