A functional mammalian display screen identifies rare antibodies that stimulate NK cell–mediated cytotoxicity

Abstract

Therapies that boost the antitumor immune response have shown a great deal of success. Although most of these therapies have focused on enhancing T cell functions, there is a growing interest in developing therapies that can target other immune cell subsets. Like T cells, natural killer (NK) cells are cytotoxic effector cells that play a key role in the antitumor response. To advance the development of NK-based therapies, we developed a functional screen to rapidly identify antibodies that can activate NK cells. We displayed antibodies on a mammalian target cell line and probed their ability to stimulate NK cell–mediated cytotoxicity. From this screen, we identified five antibodies that bound with high affinity to NK cells and stimulated NK cell–mediated cytotoxicity and interferon-γ (IFN-γ) secretion. We demonstrate that these antibodies can be further developed into bispecific antibodies to redirect NK cell–mediated cytotoxicity toward CD20+ B cell lymphoma cells and HER2+ breast cancer cells. While antibodies to two of the receptors, CD16 and NCR1, have previously been targeted as bispecific antibodies to redirect NK cell–mediated cytotoxicity, we demonstrate that bispecific antibodies targeting NCR3 can also potently activate NK cells. These results show that this screen can be used to directly identify antibodies that can enhance antitumor immune responses.

Altered NCR3 Splice Variants May Result in Deficient NK Cell Function in Renal Cell Carcinoma Patients

“…Although most immune therapies have focused on enhancing T cell functions, there is a growing interest in developing therapies that can target other immune cell subsets, such as natural killer cells. For example, one study focusing on a functional screen to rapidly identify antibodies that can activate NK cells, found that bispecific antibodies targeting NCR3 can potently activate NK cells (28). In terms of studies focused on the NK cell phenotype in RCC, researchers have investigated the phenotype of NK cells extracted from peripheral blood lymphocytes and TILs in renal cancer patients, as early as 1997 (29).…”

High-fidelity large-diversity monoclonal mammalian cell libraries by cell cycle arrested recombinase-mediated cassette exchange

“…Performing massively parallel genetic assays ( 1–3 ) and directed evolution ( 4 , 5 ) in mammalian cells offers unique opportunities that other systems cannot provide. Besides supporting proper protein folding, posttranslational modifications and subcellular localization, the mammalian system has been ingeniously applied for engineering proteins possessing special functions of biomedical interests, including stem cell differentiation ( 6 , 7 ), virus maturation inhibition ( 8 ), NK cell stimulation ( 9 ), tolerance to lysosomal pH ( 10 ) and receptor activation or blockage ( 11–14 ). In addition, mammalian cells have been utilized to generate novel ion channels ( 15 , 16 ), GPCRs ( 17 ), enhanced pluripotency factors ( 18 ) and functional TCRs, CARs and T cell antigens ( 19–21 ).…”