Retargeting NK-92 cells by means of CD19- and CD20-specific chimeric antigen receptors compares favorably with antibody-dependent cellular cytotoxicity

Abstract

Multiple natural killer (NK) cell-based anticancer therapies are currently under development. Here, we compare the efficiency of genetically modified NK-92 cells expressing chimeric antigen receptors (CARs) at killing NK cell-resistant B-lymphoid leukemia cells to the antibody-dependent cell-mediated cytotoxicity (ADCC) of NK-92 cells expressing a high affinity variant of the IgG Fc receptor (FcγRIII). First, we compared in vitro the abilities of NK-92 cells expressing CD20-targeting CARs to kill primary chronic lymphocytic leukemia (CLL) cells derived from 9 patients with active, untreated disease to the cytotoxicity of NK-92 cells expressing FcγRIII combined with either of the anti-CD20 monoclonal antibodies (mAbs) rituximab or ofatumumab. We found that CAR-expressing NK-92 cells effectively kill NK cell-resistant primary CLL cells and that such a cytotoxic response is significantly stronger than that resulting from ADCC. For studying CAR-expressing NK cell-based immunotherapy in vivo, we established xenograft mouse models of residual leukemia using the human BCR-ABL1+ cell lines SUP-B15 (CD19+CD20−) and TMD-5 (CD19+CD20+), two acute lymphoblastic leukemia (ALL) lines that are resistant to parental NK-92 cells. Intravenous injection of NK-92 cells expressing CD19-targeting CARs eliminated SUP-B15 cells, whereas they had no such effect on TMD-5 cells. However, the intrafemoral injection of NK-92 cells expressing CD19-targeting CAR resulted in the depletion of TMD-5 cells from the bone marrow environment. Comparative studies in which NK-92 cells expressing either CD19- or CD20-targeting CARs were directly injected into subcutaneous CD19+CD20+ Daudi lymphoma xenografts revealed that CD20-targeting CAR is superior to its CD19-specific counterpart in controlling local tumor growth. In summary, we show here that CAR-expressing NK-92 cells can be functionally superior to ADCC (as mediated by anti-CD20 mAbs) in the elimination of primary CLL cells. Moreover, we provide data demonstrating that the systemic administration of CAR-expressing NK-92 cells can control lymphoblastic leukemia in immunocompromised mice. Our results also suggest that the direct injection of CAR-expressing NK-92 cells to neoplastic lesions could be an effective treatment modality against lymphoma.

NK cells and cancer: you can teach innate cells new tricks

“…161) showed increased responses to tumour cells in vitro and suppressed tumour growth when tested in vivo in xenograft models 162,163 . Although initially considered as receptors providing 'built-in' ADCC-like NCRL activity against specific tumour antigens, CARs actually elicit a significantly stronger NK cell cytotoxic response than ADCC mediated by anti bodies against the same targets 164 . This may be because the ligand-binding portion of the CAR has higher affinity than the Fc region of the IgG antibody for the CD16 Fc receptor on NK cells and because the cytoplasmic domain of the CAR has been engineered to maximize intracellular signalling.…”

Clinical Applications of Natural Killer Cells

“…NK cell line has been applied to genetic modification technology for expressing intracellular IL-2 for the forced expression of CD16, natural cytotoxicity receptor (NCR), chimeric antigen receptor (CAR) and NK cell activation [68,69]. The most widely clinically used cell line is the NK-92 cell line, which is cytotoxic to a wide range of malignant cells [70,71].…”

T-cell and natural killer cell therapies for hematologic malignancies after hematopoietic stem cell transplantation: enhancing the graft-versus-leukemia effect

“…123,124 Rendering NK cells resistant to tumor microenvironment using gene modification rection of specificity enabled these cells to eliminate previously NK cell-resistant tumors in murine models. 100 Similarly, another group targeted multiple myeloma cells by transfecting NK cells with an anti-CD138 CAR.…”