Intrinsic Functional Potential of NK-Cell Subsets Constrains Retargeting Driven by Chimeric Antigen Receptors.

Natural killer (NK) cells hold potential as a source of allogeneic cytotoxic effector cells for chimeric antigen receptor (CAR)-mediated therapies. Here, we explored the feasibility of transfecting CAR-encoding mRNA into primary NK cells and investigated how the intrinsic potential of discrete NK-cell subsets affects retargeting efficiency. After screening five second- and third-generation anti-CD19 CAR constructs with different signaling domains and spacer regions, a third-generation CAR with the CH2-domain removed was selected based on its expression and functional profiles. Kinetics experiments revealed that CAR expression was optimal after 3 days of IL15 stimulation prior to transfection, consistently achieving over 80% expression. CAR-engineered NK cells acquired increased degranulation toward CD19+ targets, and maintained their intrinsic degranulation response toward CD19- K562 cells. The response of redirected NK-cell subsets against CD19+ targets was dependent on their intrinsic thresholds for activation determined through both differentiation and education by killer cell immunoglobulin-like receptors (KIR) and/or CD94/NKG2A binding to self HLA class I and HLA-E, respectively. Redirected primary NK cells were insensitive to inhibition through NKG2A/HLA-E interactions but remained sensitive to inhibition through KIR depending on the amount of HLA class I expressed on target cells. Adaptive NK cells, expressing NKG2C, CD57, and self-HLA-specific KIR(s), displayed superior ability to kill CD19+, HLA low, or mismatched tumor cells. These findings support the feasibility of primary allogeneic NK cells for CAR engineering and highlight a need to consider NK-cell diversity when optimizing efficacy of cancer immunotherapies based on CAR-expressing NK cells. Cancer Immunol Res; 6(4); 467-80. ©2018 AACR.

Oei VYS ，Siernicka M ，Graczyk-Jarzynka A ，Hoel HJ ，Yang W ，Palacios D ，Almåsbak H ，Bajor M ，Clement D ，Brandt L ，Önfelt B ，Goodridge J ，Winiarska M ，Zagozdzon R ，Olweus J ，Kyte JA ，Malmberg KJ ... -  《-》

Preclinical Assessment of Suitable Natural Killer Cell Sources for Chimeric Antigen Receptor Natural Killer-Based "Off-the-Shelf" Acute Myeloid Leukemia Immunotherapies.

Kloess S ，Oberschmidt O ，Dahlke J ，Vu XK ，Neudoerfl C ，Kloos A ，Gardlowski T ，Matthies N ，Heuser M ，Meyer J ，Sauer M ，Falk C ，Koehl U ，Schambach A ，Morgan MA ... -  《-》

CAR-NK Cells: From Natural Basis to Design for Kill.

Chimeric antigen receptors (CARs) are fusion proteins with an extracellular antigen recognition domain and numerous intracellular signaling domains that have been genetically modified. CAR-engineered T lymphocyte-based therapies have shown great success against blood cancers; however, potential fatal toxicity, such as in cytokine release syndrome, and high costs are some shortcomings that limit the clinical application of CAR-engineered T lymphocytes and remain to overcome. Natural killer (NK) cells are the focal point of current immunological research owing to their receptors that prove to be promising immunotherapeutic candidates for treating cancer. However, to date, manipulation of NK cells to treat malignancies has been moderately successful. Recent progress in the biology of NK cell receptors has greatly transformed our understanding of how NK cells recognize and kill tumor and infected cells. CAR-NK cells may serve as an alternative candidate for retargeting cancer because of their unique recognition mechanisms, powerful cytotoxic effects especially on cancer cells in both CAR-dependent and CAR-independent manners and clinical safety. Moreover, NK cells can serve as an 'off-the-shelf product' because NK cells from allogeneic sources can also be used in immunotherapies owing to their reduced risk of alloreactivity. Although ongoing fundamental research is in the beginning stages, this review provides an overview of recent developments implemented to design CAR constructs to stimulate NK activation and manipulate NK receptors for improving the efficiency of immunotherapy against cancer, summarizes the preclinical and clinical advances of CAR-NK cells against both hematological malignancies and solid tumors and confronts current challenges and obstacles of their applications. In addition, this review provides insights into prospective novel approaches that further enhance the efficiency of CAR-NK therapies and highlights potential questions that require to be addressed in the future.

Khawar MB ，Sun H 《Frontiers in Immunology》

HLA-E binds to natural killer cell receptors CD94/NKG2A, B and C.

Braud VM ，Allan DS ，O'Callaghan CA ，Söderström K ，D'Andrea A ，Ogg GS ，Lazetic S ，Young NT ，Bell JI ，Phillips JH ，Lanier LL ，McMichael AJ ... -  《NATURE》

The CD94/NKG2C killer lectin-like receptor constitutes an alternative activation pathway for a subset of CD8+ T cells.

Gumá M ，Busch LK ，Salazar-Fontana LI ，Bellosillo B ，Morte C ，García P ，López-Botet M ... -  《EUROPEAN JOURNAL OF IMMUNOLOGY》