title: An Fc-optimized NKG2D-immunoglobulin G fusion protein for induction of natural killer cell reactivity against leukemia.
abstract: Recruitment of Fc-receptor-bearing effector cells, such as natural killer (NK) cells, is a feature critical for the therapeutic success of antitumor antibodies and can be improved by the modifications of an antibody's Fc part. The various ligands of the activating immunoreceptor NKG2D, NKG2DL) are selectively expressed on malignant cells including leukemia. We here took advantage of the tumor-associated expression of NKG2DL for targeting leukemic cells by NKG2D-immunoglobulin G (IgG)1 fusion proteins containing modified Fc parts. Compared to NKG2D-Fc containing a wild-type Fc part (NKG2D-Fc-WT), our mutants (S239D/I332E and E233P/L234V/L235A/ΔG236/A327G/A330S) displayed highly enhanced (NKG2D-Fc-ADCC) and abrogated (NKG2D-Fc-KO) affinity to the NK cell Fc receptor, respectively. Functional analyses with allogenic as well as autologous NK cells and primary malignant cells of leukemia patients revealed that NKG2D-Fc-KO significantly reduced NK reactivity by blocking immunostimulatory NKG2D-NKG2DL interaction. NKG2D-Fc-WT already enhanced antileukemia reactivity by inducing antibody-dependent cellular cytotoxicity (ADCC) with NKG2D-Fc-ADCC mediating significantly stronger effects. Parallel application of NKG2D-Fc-ADCC with Rituximab caused additive effects in lymphoid leukemia. In line with the tumor-associated expression of NKG2DL, no NK cell ADCC against resting healthy blood cells was induced. Thus, NKG2D-Fc-ADCC potently enhances NK antileukemia reactivity despite the inevitable reduction of activating signals upon binding to NKG2DL and may constitute an attractive means for immunotherapy of leukemia.
authors.affiliation: Department of Hematology and Oncology, Eberhard Karls University, Tuebingen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Steinbacher
authors.forename: Katrin
authors.initials: K
authors.lastname: Baltz-Ghahremanpour
authors.forename: Benjamin Joachim
authors.initials: BJ
authors.lastname: Schmiedel
authors.forename: Alexander
authors.initials: A
authors.lastname: Steinle
authors.forename: Gundram
authors.initials: G
authors.lastname: Jung
authors.forename: Ayline
authors.initials: A
authors.lastname: Kübler
authors.forename: Maya Caroline
authors.initials: MC
authors.lastname: André
authors.forename: Ludger
authors.initials: L
authors.lastname: Grosse-Hovest
authors.forename: Helmut Rainer
authors.initials: HR
authors.lastname: Salih
mesh_terms: D000920:Antibody-Dependent Cell Cytotoxicity; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000276:immunology*; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology*; D007167:Immunotherapy; D007694:Killer Cells, Natural / Q000276:immunology* / Q000473:pathology; D007938:Leukemia / Q000235:genetics / Q000276:immunology* / Q000473:pathology*; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000235:genetics / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; C527085:KLRK1 protein, human; D055655:NK Cell Lectin-Like Receptor Subfamily K; D011993:Recombinant Fusion Proteins
keywords: ADCC; NK cells; NKG2D ligands; leukemia