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

J Clin Invest. 2019 Mar 12;129(5):2094-2106. doi: 10.1172/JCI123955. Print 2019 May 1.


A key mechanism of tumor resistance to immune cells is mediated by expression of peptide-loaded HLA-E in tumor cells, which suppresses natural killer (NK) cell activity via ligation of the NK inhibitory receptor CD94/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 significantly more powerful than NKG2A+ NK cells against HLA-E-expressing tumors. Thus, NKG2A downregulation evades the HLA-E cancer immune-checkpoint, and increases the anti-tumor 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.

Keywords: Immunology; Immunotherapy; Innate immunity; NK cells; Oncology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cytotoxicity, Immunologic
  • Down-Regulation
  • Drug Resistance, Neoplasm*
  • Endoplasmic Reticulum / metabolism
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic
  • Histocompatibility Antigens Class I / immunology*
  • Humans
  • Immunotherapy / methods*
  • K562 Cells
  • Killer Cells, Natural / metabolism*
  • Mice
  • Mice, Inbred NOD
  • Mice, SCID
  • NK Cell Lectin-Like Receptor Subfamily C / antagonists & inhibitors
  • NK Cell Lectin-Like Receptor Subfamily C / metabolism*
  • NK Cell Lectin-Like Receptor Subfamily D / metabolism*
  • Neoplasm Transplantation
  • Protein Domains
  • Receptors, Immunologic / metabolism
  • U937 Cells


  • HLA-E antigen
  • Histocompatibility Antigens Class I
  • KLRC1 protein, human
  • KLRD1 protein, human
  • Klrc1 protein, mouse
  • NK Cell Lectin-Like Receptor Subfamily C
  • NK Cell Lectin-Like Receptor Subfamily D
  • Receptors, Immunologic