Blocking expression of inhibitory receptor NKG2A overcomes tumor resistance to NK cells
Takahiro Kamiya, See Voon Seow, Desmond Wong, Murray Robinson, Dario Campana
Takahiro Kamiya, See Voon Seow, Desmond Wong, Murray Robinson, Dario Campana
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Research Article Immunology Oncology

Blocking expression of inhibitory receptor NKG2A overcomes tumor resistance to NK cells

Abstract

A key mechanism of tumor resistance to immune cells is mediated by expression of peptide-loaded HLA class I molecule (HLA-E) in tumor cells, which suppresses NK cell activity via ligation of the NK inhibitory receptor CD94/NK group 2 member A (NKG2A). Gene expression data from approximately 10,000 tumor samples showed widespread HLAE expression, with levels correlating with those of KLRC1 (NKG2A) and KLRD1 (CD94). To bypass HLA-E inhibition, we developed a way to generate highly functional NK cells lacking NKG2A. Constructs containing a single-chain variable fragment derived from an anti-NKG2A antibody were linked to endoplasmic reticulum–retention domains. After retroviral transduction in human peripheral blood NK cells, these NKG2A protein expression blockers (PEBLs) abrogated NKG2A expression. The resulting NKG2Anull NK cells had higher cytotoxicity against HLA-E–expressing tumor cells. Transduction of anti-NKG2A PEBL produced more potent cytotoxicity than interference with an anti-NKG2A antibody and prevented de novo NKG2A expression without affecting NK cell proliferation. In immunodeficient mice, NKG2Anull NK cells were substantially more powerful than NKG2A+ NK cells against HLA-E–expressing tumors. Thus, NKG2A downregulation evades the HLA-E cancer immune checkpoint and increases the antitumor activity of NK cell infusions. Because this strategy is easily adaptable to current protocols for clinical-grade immune cell processing, its clinical testing is feasible and warranted.

Authors

Takahiro Kamiya, See Voon Seow, Desmond Wong, Murray Robinson, Dario Campana

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Figure 2

Downregulation of NKG2A expression in NK cells with anti-NKG2A PEBLs.

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Downregulation of NKG2A expression in NK cells with anti-NKG2A PEBLs. (A...
(A) Schematic representation of the anti-NKG2A PEBL constructs and their mechanisms of action. The PEBL constructs consist of a CD8α signal peptide and an anti-NKG2A scFv followed, at the C terminus, by the sequences listed in the box, according to each PEBL. PEBL1 binds to the KDEL receptor, which joins the COPI. PEBLs 2–4 bind directly to COPI. VL, light chain variable domain; VH, heavy chain variable domain. (B) Downregulation of NKG2A expression in NK92 cells. Flow cytometric histograms show surface expression of NKG2A, as detected by anti-NKG2A APC (Miltenyi Biotech), after transduction with a vector containing GFP only (Control) or GFP plus PEBLs 1–4. (C) NKG2A+ expanded human NK cells were purified by magnetic bead–positive selection and transduced with anti–NKG2A-PEBL2 or with GFP only. Shown are the percentages of NKG2A+ cells before and after purification and after transduction (10 experiments with NK cells from 9 donors), as measured by flow cytometry. ****P < 0.0001, t test. (D) Representative flow cytometry dot plots of 2 of the experiments shown in C. The right area in each dot plot encloses GFP+ (i.e., transduced) NK cells; the percentages of NKG2A+ and NKG2A cells among these cells are shown.