Article
NKG2C-positive NK cells from patient blood for immunotherapy of HLA-E-positive glioma
NKG2C-positive NK-Zellen aus Patientenblut für die Immuntherapie von HLA-E-positiven Gliomen
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Published: | June 26, 2020 |
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Objective: Natural killer (NK) cells hold potential as promising effector cells in immunotherapy of human malignancies. This study focuses on NKG2C+ NK cells, a small NK cell subpopulation in the blood of human cytomegalovirus (HCMV) seropositive patients. These NK cells are able to recognize the HLA-G signal peptide or peptides of HCMV presented by HLA-E molecules on the surface of glioblastoma cells via their activating NKG2C receptor. Consequently, NKG2C+ NK cells have a higher intrinsic capability to specifically kill glioblastoma cells. In our study we investigated, whether ex vivo expanded NKG2C+ NK cells from HCMV seropositive GBM patients have an anti-tumour effect against autologous and allogenic HLA-E+ glioblastoma cells.
Methods: NK cells were isolated from blood of HCMV seropositive GBM patients and NKG2C+ NK cells were specifically expanded for two weeks via novel HLA-E+ feeder cell lines. Furthermore NK cells were analysed in respect to expression of inhibitory receptors, activation and exhaustion markers before and after expansion. In parallel GBM tumour tissue of the patients was cultivated and analysed in respect of GBM-associated immune cell populations by flow cytometry. Afterwards cytotoxicity of ex vivo expanded NKG2C+ NK cells was investigated by chromium release assays using autologous and allogenic primary glioblastoma cells.
Results: Co-cultivation of isolated primary NK cells with HLA-E+ feeder cells for 14 days resulted in percentage of more than 85% NKG2C+ NK cells. These expanded NKG2C+ NK cells displayed a slight increase of KIRs and an induced expression of high affinity IL-2 receptor (>70%). Of note, PD-1 levels were not affected. Parallel cultivated GBM tumour tissue of the patients displayed an infiltration of T lymphocytes (median of 4%), but no B and NK cells. In subsequent experiments expanded NKG2C+ NK cells showed cytotoxicity against HLA-E+ primary glioblastoma cells irrespective of KIR:KIR-ligand settings.
Conclusion: Our results demonstrate a novel highly efficient ex vivo expansion method to gain NKG2C+ NK cells from blood of HCMV seropositive GBM patients. This is a first step in the development of an adoptive cellular immunotherapy using NKG2C+ NK cells for treatment of GBM.