Blocking expression of inhibitory receptor NKG2A overcomes tumor resistance to NK cells
Takahiro Kamiya, … , Murray Robinson, Dario Campana
Takahiro Kamiya, … , Murray Robinson, Dario Campana
Published March 12, 2019
Citation Information: J Clin Invest. 2019;129(5):2094-2106. https://doi.org/10.1172/JCI123955.
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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 7

Antitumor capacity of anti-NKG2A PEBL-transduced NK cells in immunodeficient mice.

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Antitumor capacity of anti-NKG2A PEBL-transduced NK cells in immunodefic...
(A) ES8 cells (2 × 105) transduced with GpHLA-E and luciferase were injected i.p. in 23 NOD/SCID IL2RGnull mice. One day later, mice were treated with 1 × 107 expanded NKG2A+ NK cells transduced with either GFP alone (Control) or with anti-NKG2A PEBL (n = 7 for each group); another group of mice received tissue culture medium instead (no NK; n = 9). One additional injection of NK cells or medium was given 4 days later. All mice received i.p. injections of IL-2 (20,000 IU each) 3 times per week. Bioluminescence was measured with a Xenogen IVIS Spectrum System, with imaging beginning 5 minutes after i.p. injection of d-luciferin (150 μg/g body weight) and analyzed with Living Image 3.0 software. Collated ventral images of mice in 2 independent experiments are shown, 1 with 9 mice (3 in each group) and the other with 14 mice (6 injected with tumor alone, 4 treated with control NK cells, and 4 with anti-NKG2A PEBL NK cells). (B) Luminescence measurements of tumor cell growth. Each symbol corresponds to the sum of bioluminescence measurements by ventral and dorsal imaging in each mouse. (C) Kaplan-Meier curves and log-rank test for overall survival. Mice were euthanized when the sum of ventral and dorsal bioluminescence signal reached 5 × 1010 photons per second. **P = 0.0034; ***P < 0.001.