Blocking NK cell inhibitory self-recognition promotes antibody-dependent cellular cytotoxicity in a model of anti-lymphoma therapy.

Department of Medical Oncology and Division of Basic Science, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
The Journal of Immunology (Impact Factor: 5.36). 06/2008; 180(9):6392-401. DOI: 10.4049/jimmunol.180.9.6392
Source: PubMed

ABSTRACT Human NK cells lyse Ab-coated target cells through the process of Ab-dependent cellular cytotoxicity (ADCC). Improving ADCC responses is desirable because it is thought to be an important antitumor mechanism for some Abs. NK cell inhibitory receptors, such as killer cell Ig-like receptors, engage with MHC class I molecules on self-cells to block NK cell activation. Accordingly, we enhanced ADCC responses by blocking NK cell inhibitory receptors, thus perturbing induction of the self-recognition signal. In a cell line model of anti-lymphoma therapy, the combination of rituximab with an Ab that blocks inhibitory self-recognition yielded increased NK cell-mediated target cell lysis when compared with rituximab alone. To validate this proof-of-concept, we then used a more representative approach in which an individual's fresh primary NK cells encountered autologous, EBV-transformed B cells. In this system, rituximab and a combination of Abs that block NK cell inhibitory receptors yielded improved NK cell-mediated lysis over rituximab alone. The results show, for the first time, that disruption of inhibitory self-recognition can efficiently promote ADCC in a human model, applying an autologous system in which physiologic checkpoints are in place. This method provides an alternative approach to potentiate the therapeutic benefit of antitumor Abs that mediate ADCC.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Human Cytomegalovirus (HCMV) transmission within the host is important for the pathogenesis of HCMV diseases. Natural Killer (NK) cells are well known to provide a first line of host defense against virus infections. However, the role of NK cells in the control of HCMV transmission is still unknown. Here, we provide the first experimental evidence that NK cells can efficiently control HCMV transmission in different cell types. NK cells engage different mechanisms to control the HCMV transmission both via soluble factors and by cell contact. NK cell produced interferon gamma (IFN-γ) suppresses HCMV production and induces resistance of bystander cells to HCMV infection. The viral gene UL16 contributes to an immune evasion from the NK cell mediated control of HCMV transmission. Furthermore, the efficacy of the antibody dependent NK cell mediated control of HCMV transmission is dependent on CD16-158V/F polymorphisms. Our findings indicate that NK cells may have a clinical relevance in HCMV infection and highlight the need to consider potential therapeutic strategies based on the manipulation of NK cells. Human Cytomegalovirus (HCMV) infects 40% to 100% of the human population worldwide. After primary infection, mainly in childhood, the virus establishes a lifelong persistence with possible reactivations. Most infections remain asymptomatic; however, HCMV represents a major health problem since it is the most frequent cause of infection-induced birth defects and is responsible for a high morbidity and mortality in immunocompromised patients. The immune system normally controls the infection by antibodies and immune effector cells. One type of effector cells are the Natural Killer (NK) cells which provide a rapid response to virus-infected cells. NK cells participate in the viral clearance by inducing the death of infected cells. NK cells also secrete anti-viral cytokines as a consequence of the interaction with an infected cell. In this study, we investigated the mechanisms by which NK cells control HCMV transmission, from the perspectives of immune surveillance and immune evasion. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Journal of Virology 12/2014; 89(5). DOI:10.1128/JVI.03489-14 · 4.65 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: CD16a and CD16b are IgG Fc receptors expressed by human natural killer (NK) cells and neutrophils, respectively. Both CD16 isoforms undergo a rapid down-regulation in expression by ADAM17-mediated proteolytic cleavage upon cell activation by various stimuli. We examined soluble CD16 released from activated NK cells and neutrophils by mass spectrometric analysis, and identified three separate cleavage sites in close proximity at P1/P1' positions alanine195/valine196, valine196/serine197, and threonine198/isoleucine199, revealing a membrane proximal cleavage region in CD16. Substitution of the serine at position 197 in the middle of the cleavage region for a proline (S197P) effectively blocked CD16a and CD16b cleavage in cell-based assays. We also show that CD16a/S197P was resistant to cleavage when expressed in the human NK cell line NK92 and primary NK cells derived from genetically-engineered human induced pluripotent stem cells. CD16a is a potent activating receptor and despite blocking CD16a shedding, the S197P mutation did not disrupt IgG binding by the receptor or its activation of NK92 cells by antibody-treated tumor cells. Our findings provide further characterization of CD16 cleavage by ADAM17 and they demonstrate that a non-cleavable version of CD16a can be expressed in engineered NK cells.
    PLoS ONE 01/2015; 10(3):e0121788. DOI:10.1371/journal.pone.0121788 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Monoclonal antibodies can modulate cancer cell signal transduction and recruit anti-tumor immune effector mechanisms - including antibody-dependent cellular cytotoxicity (ADCC). Although several clinically effective antibodies can promote ADCC, therapeutic resistance is common. We hypothesized that oncogenic signaling networks within tumor cells affect their sensitivity to ADCC. We developed a screening platform and targeted 60 genes derived from an EGFR gene network using RNA interference (RNAi) in an in vitro ADCC model system. Knockdown of GRB7, PRKCE, and ABL1 enhanced ADCC by primary and secondary screens. ABL1 knockdown also reduced cell proliferation, independent of its ADCC enhancement effects. c-Abl overexpression decreased ADCC sensitivity and rescued the effects of ABL1 knockdown. Imatinib inhibition of c-Abl kinase activity also enhanced ADCC - phenocopying ABL1 knockdown - across several EGFR-expressing head-and-neck squamous cell carcinoma (HNSCC) cell lines by ex vivo primary NK cells. Our findings suggest that combining c-Abl inhibition with ADCC-promoting antibodies, such as cetuximab, could translate into increased therapeutic efficacy of monoclonal antibodies.
    10/2014; 2(12). DOI:10.1158/2326-6066.CIR-14-0083