OBJECTIVES: Preclinical studies with NK cells were promising and several clinical studies are ongoing to investigate their use in antibody therapies. However, more reliable ADCC assays are required for evaluating NK cell activity to optimise therapeutic antibodies. The therapeutic potential of NK cell therapy could then be improved by harnessing ADCC.
METHODS: This review discusses recent studies on key components of NK cell-mediated ADCC, current clinical trials involving NK cells, ADCC assay developments and various techniques to improve ADCC.
RESULTS: Improvements can be made to NK-mediated ADCC through modifications of antibodies, effector cells and target antigens. Different aspects of antibodies were studied extensively, including modifying glycosylation patterns, novel production methods, combination regiments, bispecific antibodies, and conjugated antibodies. Modification of NK cells and tumour surface markers could improve ADCC of even treatment-resistant cancer cells. Additives such as cytokines and other immunomodulatory agents can further augment ADCC to supplement NK cell-based therapies.
CONCLUSION: ADCC improvements could be incorporated with current biological techniques such as adoptive transfer of NK cells and chimeric antigen receptor (CAR) NK cells, to improve the outcome of NK cell-based therapy and pave the way for future immunotherapies.
METHODS: We established an isogeneic cell model consisting of parental dermal fibroblasts, fibroblast-like iPSC-derivatives (iPS-fibro) and iPS-fibro lacking beta-2-microglobulin (B2M). Using the cells obtained from two patients, we analyzed the activation of autologous and allogeneic T-lymphocytes and NK-cells co-cultured with target cells.
RESULTS: Here we report that cells differentiated from iPSCs can be recognized by NK-cells rather than by autologous T-cells. We observed that iPS-fibro elicited a high level of NK-cell degranulation and cytotoxicity, while isogeneic parental skin fibroblasts used to obtain iPSCs barely triggered an NK-cell response. iPSC-derivatives with B2M knockout did not cause an additional increase in NK-cell activation, although they were devoid of HLA-I, the major inhibitory molecules for NK-cells. Transcriptome analysis revealed a significant imbalance of ligands for activating and inhibitory NK-cell receptors in iPS-fibro. Compared to parental fibroblasts, iPSC-derivatives had a reduced expression of HLA-I simultaneously with an increased gene expression of major activating ligands, such as MICA, NECTIN2, and PVR. The lack of inhibitory signals might be due to insufficient maturity of cells differentiated from iPSCs. In addition, we showed that pretreatment of iPS-fibro with proinflammatory cytokine IFNγ restored the ligand imbalance, thereby reducing the degranulation and cytotoxicity of NK-cells.
CONCLUSION: In summary, we showed that iPSC-derived cells can be sensitive to the cytotoxic potential of autologous NK-cells regardless of HLA-I status. Thus, the balance of ligands for NK-cell receptors should be considered prior to iPSC-based cell therapies. Trial registration Not applicable.