FcɛR1γ-based Activating Chimeric Antigen Receptors enhanced Natural Killer cell function against HLA-E ⁺ cells

FcɛR1γ is a transmembrane adaptor protein regulating NKp30, NKp46, and CD16 expression and function in human NK cells. HLA-E expression by cancer cells suppresses NK cell function through interaction with NKG2A. Here, we engineered human NK cells to express a modified FcɛR1γ with a 4-1BB co-stimulatory motif. FcɛR1γ ^41BB expression led to upregulation of NKp30, NKp46, and CD16 expression and enhanced NKp30 and CD16-mediated target cell lysis. Against cells expressing HLA-E, FcɛR1γ ^41BB improved NK cell lytic function relative to FcɛR1γ. We then generated an CD19 ^ScFv -CD8 ^hinge -FcεR1γ ^41BB(TM-IC) CAR (FCRG10). Engineering human NK cells to express FCRG10 led to upregulation of NKp30 and CD16, and improved NK cell-mediated cytotoxicity against cells co-expressing B7H6, CD19, and HLA-E relative to NK cells expressing the conventional CD19CAR ^41BB-CD3ζ with a CD8 transmembrane domain. Our results indicate that modification of FcɛR1γ enhanced NK cell lytic function mediated by several activating receptors and improved CAR NK cell response in conditions favoring NK cell suppression by HLA-E. Our work may contribute to NK cell-based cancer immunotherapy mediated by co-recognition of stress-induced ligands, antibody-coated cells, and tumor-associated antigens.