Enhanced Elimination of 6-Mercaptopurine or Methotrexate-Treated Acute Lymphoblastic Leukemia Cells by Natural Killer Lymphocytes In Vitro: A Potential Mechanism of Action of Maintenance Chemotherapy

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2128-2128 ◽  
Author(s):  
Abdual H. Siddiqui ◽  
Mohammad Bhuiyan ◽  
Akila Muthukumar ◽  
Steven Buck ◽  
Yaddanapudi Ravindranath ◽  
...  
Keyword(s):  
Nk Cells ◽  
Natural Killer ◽  
Drug Exposure ◽  
Nk Cell ◽  
Lymphoblastic Leukemia ◽  
Leukemia Cells ◽  
Target Cells ◽  
Lymphoma Cells ◽  
Nkg2d Ligands ◽  
Reh Cells

Abstract Abstract 2128 Background: Maintenance chemotherapy (MC) is an important component of childhood B-precursor acute lymphoblastic leukemia (ALL) therapy; however, it is not necessary in the treatment of mature B cell neoplasms. The operational mechanisms of MC are not understood. Improvement in immunologic function including near normal levels of natural killer (NK) lymphocytes was reported during ALL MC. We hypothesize that in addition to their direct cytotoxicity, MC drugs alter surviving lymphoblasts, rendering them susceptible to innate immune response, likely through cell mediated cytotoxicity via stress proteins such as NKG2D ligands, co-stimulatory or adhesion molecules. Objective: The effect of 6-mercaptopurine (6MP) or methotrexate (MTX) treatment of B-precursor and mature B leukemia/lymphoma cells in their elimination by NK lymphocytes was investigated in this study. Design and Methods: Allogeneic NK cell-mediated elimination of REH (TEL/AML-positive B-precursor ALL) and Raji (mature B cell lymphoma) cells treated with standard MC drugs was studied. High dose cytarabine (Ara-C) and MTX are used during the consolidation chemotherapy; therefore, Ara-C and MTX-resistant REH and Raji cell sub-lines were established by exposing wild type cells to increasing concentrations of drugs over several months. Natural killer cells from 17 healthy volunteers were separated using the MACS NK cell isolation kit. After purity evaluation, NK cells were incubated with interleukin-15 overnight. Leukemia cells were incubated in minimally toxic (20% cytotoxicity) concentrations of 6MP and MTX. The leukemia/lymphoma cells were then co-incubated with NK cells at different ratios. The NK cell-mediated leukemia/lymphoma cell cytotoxicity was measured by flow cytometric cell-mediated cytotoxicity assay, marking effector cells with lineage-specific monoclonal antibodies and staining target cells with propidium iodide and annexin-V and using microspheres for quantification of viable and apoptotic cells. The level of resistance of the respective cell sub-lines was evaluated using MTT assay. We also investigated whether NK cell exposure to same concentrations of MC drugs before co-incubation alters cytotoxicity. Surface expression of NKG2D ligands, ULBP 1, 2 and 3, MICA and MICB was studied by flow cytometry. Results: 6-mercaptopurine treatment of REH cells and MTX treatment of Raji cells resulted in enhanced NK cell-mediated elimination when compared to untreated cells by 25% and 20%, respectively. The results were similar when NK cells were exposed to the same concentrations of MC drugs before co-incubation, indicating lack of negative effect of the drug exposure in NK cells’ ability to kill. Similar experiments were conducted on resistant cells, in order to make the target cells more comparable to the residual lymphoblasts during MC. Most interestingly, the REH cells, but not the Raji cells, resistant to Ara-C and MTX showed about 14% and 4% enhancement of NK cell-mediated killing, respectively, after being exposed to the minimally toxic concentrations of MC drugs. This indicates that resistant B precursor ALL cells can be eliminated by NK cells upon MC drug exposure, but not mature B lymphoblasts, in this experimental setting. No increase in the expression of NKG2D ligands on drug treated ALL cells was observed. Conclusion: These findings suggest that enhanced susceptibility of drug-exposed leukemia cells to innate immune response may be an operational mechanism of MC. This mechanism may involve pathways other than NKG2D. Disclosures: No relevant conflicts of interest to declare.

Natural Killer Cells with NKDG2D Cytotoxicity but NKp30-Dull Phenotype Predominate in Myelodysplastic Syndrome (MDS).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 3436-3436
Author(s):  
Fanqi Bai ◽  
Jeffrey S. Painter ◽  
Cantor Alan ◽  
Zou JianXiang ◽  
Sheng Wei ◽  
...  
Keyword(s):  
Nk Cells ◽  
Natural Killer ◽  
Cell Line ◽  
Cell Lines ◽  
Nk Cell ◽  
B Cell Lymphoma ◽  
Target Cells ◽  
Nkg2d Ligands ◽  
Human Stress ◽  
Normal Controls

Abstract Natural Killer (NK) function in patients with MDS as measured by non-MHC-restricted cytotoxicity and activation-dependent cell cytotoxicity (ADCC) are reduced in patients with MDS, however, the mechanisms of the functional impairment are not known. Tumor cytolysis occurs through orchestrated control by inhibitory NK receptors (NKRs) and activating NKRs, which control signaling events that lead to polarized movement of perforin-containing granules toward the NK-tumor contact area. We found that NK cells from 23 out of 35 patients with MDS (66%) displayed reduced lysis of K562 tumor cells compared to age-matched normal controls (p<0.01). To better characterize this defect, we evaluated patient NK function against differential tumor targets including the MDS1 cell line established from an MDS patients. We found that MDS1 incited non-MHC-restricted lysis. Unactivated PBMCs, unactivated NK cells, NK cell lines (NK92 and NKL) but not purified unactivated T cells from normal donors killed MDS1 in 4-hr 51Cr-release assays. Normal NK cells and NK cell lines were also found to rapidly redistrubute perforin granules after exposure to MDS1suggesting that a perforin-dependent lytic pathway was activated. We then performed simultaneous cytolytic assays with K562, MDS1, and the 721.221 B cell lymphoma cell line as target cells. We found that NK cells from MDS patients had greater lytic activity against MDS1 (average 24% vs. average 8% at 50:1 Effector:Target ratio, respectively, p<0.01) Antibody-blocking experiments demonstrated that the NKL cell line and PBMCs from 8 out of 10 MDS patients predominantly used the NKG2D activating receptor to kill MDS1. Consistent with this finding, we showed that MDS1 cells express the major human stress-inducible endogenous proteins MICA and MICB, which are NKG2D ligands. In contast, lysis by NK92 cells and normal PBMCs was not appreciably reduced by NKG2D blocking antibodies suggesting that other unidentified NKR(s) also mediate lysis. To identify the NKRs expressed in MDS patients, we performed immunophenotyping for both the activating NKRs and inhibitory NKRs compared to age-matched normal controls. We found that two activating receptors, NKp30 and CD244 (2B4), were significantly reduced on NK cells from all MDS patients regardless of their ability to lyse NK targets. Inhibitory NKR expression and function were normal. Interestingly, NKG2D expression correlated with reduced cytolytic function. Similar to studies on normal NK cells with low NKp30 and NKp46 (NCRdull) phenotypes, these results suggest that low NKp30 expression leads to predominant NKG2D utilization for tumor cell lysis, which is reduced in MDS patients with defective NK function. Our findings provide critical information about potential importance for immunosurviellance through NKG2D-NKG2D ligands.

Expression of Activating Natural Killer Cell Receptor Ligands in Childhood Acute Lymphoblastic Leukemia.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4478-4478
Author(s):  
Ulrike Mura ◽  
Matthias Pfeiffer ◽  
Rupert Handgretinger ◽  
Peter J. Lang
Keyword(s):  
Flow Cytometry ◽  
Natural Killer ◽  
Nk Cell ◽  
Lymphoblastic Leukemia ◽  
Critical Role ◽  
Killer Cell ◽  
Negative Control ◽  
Target Cells ◽  
Nkg2d Ligands ◽  
Ligand Expression

Abstract Activating and inhibitory cell surface receptors regulate natural killer (NK) cell effector functions. The extent of expression of their activating ligands on target cells probably plays a critical role in tumor immune surveillance, but the data of this expression on blasts of leukemia patients are still poor. We examined blasts of children with ALL for the activating human NKG2D ligands MICA, MICB, ULBP1, ULBP2 and ULBP3, and for the ligands of the activating human natural cytotoxic receptors (NCRs) NKp30, NKp44 and NKp46. Using ligand specific mouse monoclonal antibodies and flow cytometry, we screened 24 children (23 common-ALL, one pre-T-ALL) for the expression of NKG2D ligands and 15 children (all common-ALL) for NCR ligands. In 13 patients (all common-ALL), also the density of the NKG2D ligands was determined by quantitative flow cytometry. Considering cells positive for a particular ligand in case of a two fold increase of median fluorescence above negative control, 38 percent of the patients were positive for one or more NKG2D ligands, while only 13 percent expressed one or more NCR ligands at significant levels. ULBP1 was most frequently expressed (29 percent of patients positive), while no patients were positive for ULBP2 and NKp44 ligands. ULBP3 was positive in 17 percent of the patients, NKp30 and NKp46 ligands in 13 percent, MICA and MICB in 4 percent. The patient with pre-T-ALL was positive only for ULBP1. So ULBP1 was expressed more frequently, while the other NKG2D ligands were expressed less frequently in children than reported for adult leukemia patients before (Salih et al. Blood.2003;102:1389–1396.). The density of detected NKG2D ligand molecules was always rather low. For MICA the maximum were 1700 molecules per cell in a single patient, for MICB 900, for ULBP1 1100, and for ULBP3 1000 molecules per cell. In summary, blasts of pediatric ALL patients displayed low or negative surface levels of ligands for the human activating NK cell receptors NKG2D, NKp30, NKp44 and NKp46. QUALITATIVE LIGAND EXPRESSION QUALITATIVE LIGAND EXPRESSION QUANTITATIVE LIGAND EXPRESSION QUANTITATIVE LIGAND EXPRESSION

Artificial Antigen Presenting Cells (aAPC) Expanded NK-Mediated Enhanced Lysis of Allogeneic Tumor Cells Regardless of HLA Class I/KIR Mismatch and Its Implication of Use in Eradicating Acute Lymphoblastic Leukemia (ALL).

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 3023-3023
Author(s):  
Hua Zhang ◽  
Bruce Levine ◽  
Nga Voong ◽  
Alan S. Wayne ◽  
Carl H. June ◽  
...  
Keyword(s):  
Acute Lymphoblastic Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Solid Tumors ◽  
Tumor Cells ◽  
Fusion Proteins ◽  
Nk Cell ◽  
Lymphoblastic Leukemia ◽  
Target Cells ◽  
Activating Receptors

Abstract Abstract 3023 Poster Board II-999 NK Killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA) ligands play critical roles in maintaining natural killer (NK) cell tolerance, while providing surveillance against pathogens and malignant transformation. Natural killer (NK) cells have been explored as tools for adoptive anti-tumor or leukemia immunotherapy and current models hold that a mismatch or absence of KIR ligands on target cells is essential for efficient NK cell mediated cytolysis. However, new approaches are now available to activate NK cells and the role for KIR mediated signaling in regulating cytotoxicity of activated NK cells has not been well studied. In this study, aAPCs comprising IL15Ra+K562 cells engineered to express 4-1BBL activated and expanded peripheral NK cells in the presence of exogenous IL15 up to 1000-fold in 3 weeks. Compared to resting NK cells, 4-1BBL/IL15-activated NK cells upregulated TRAIL and NKp30, 44, 46 expression, and showed significantly enhanced cytotoxicity against a multitude of tumor targets including K562, Daudi, Ewing's tumors, osteosarcoma, as well as autologous tumors (50%-90% killing vs. 0%-8% with non-activated NK cells). Meanwhile we could detect little to no influence of KIR signaling in regulating cytotoxicity by aAPC activated NK cells, since sorted CD158a+ and CD158b+ activated NK cells showed similar killing of tumor cells expressing HLA group C1 (CD158b ligand) and/or C2 (CD158a ligand) antigens. In contrast, killer activating receptors (KARs) were indispensable for the cytolysis of solid pediatric tumors by aAPC-activated NK cells, since the killing was significantly inhibited by fusion proteins binding to the ligands of NKG2D, NK p30, p44, p46, p80 (KARs). About 20-40% inhibition of the killing was accomplished when all four activating receptors were blocked, though other activating receptors have not been well defined. Although acute lymphoblastic leukemia (ALL) blasts were refractory to fresh NK cytotoxicity, 4-1BBL/IL15 activated NK cells demonstrated higher lytic activities (20%-50%) against ALL blasts from either patients or cell lines. ALL blast lysis could be completely or partially inhibited by KAR-blocking fusion proteins, indicating that expression levels of KAR ligands vary among ALL cases and other solid tumors. We conclude that KIR ligand mismatch or absence is not essential for effective NK cytotoxicities on either solid tumors or ALL when fully activated NK cells are utilized. This suggests that adoptive therapy with autologous aAPC-activated NK cells may prove effective in some clinical settings, such as ALL, AML, or certain solid tumors. Further studies to assess the impact of KAR ligand expression on aAPC-activated NK killing of ALL blasts are in progress. Percentage of Activated NK Killings vs. Fresh NK's with/without KAR-Ig Fusion Proteins Activated NK (E:T=2.5:1) Fresh NK (E:T=25:1) -KAR-Ig Fc +KAR-Ig Fc SB tumor (Ewing's) 48% 30% 0.5% HOS (Osteo sarcoma) 63% 36% 0.7% Daudi (B. lymphoma) 78% 46% 0.2% REH (ALL) 54% 8% 3% Disclosures No relevant conflicts of interest to declare.

scholarly journals Exploitation of natural killer cells for the treatment of acute leukemia

Blood ◽  
2016 ◽  
Vol 127 (26) ◽  
pp. 3341-3349 ◽  
Author(s):  
Rupert Handgretinger ◽  
Peter Lang ◽  
Maya C. André
Keyword(s):  
Cell Therapy ◽  
Nk Cells ◽  
Natural Killer ◽  
Adoptive Transfer ◽  
Nk Cell ◽  
Lymphoblastic Leukemia ◽  
Leukemia Cell ◽  
Target Cells

Abstract Natural killer (NK) cells play an important role in surveillance and elimination of malignant cells. Their spontaneous cytotoxicity was first demonstrated in vitro against leukemia cell lines, and NK cells might play a crucial role in the therapy of leukemia. NK cell activity is controlled by an array of germ line–encoded activating and inhibitory receptors, as well as modulating coreceptors. This biologic feature can be exploited in allogeneic cell therapy, and the recognition of “missing-self” on target cells is crucial for promoting NK cell–mediated graft-versus-leukemia effects. In this regard, NK cells that express an inhibitory killer immunoglobulin-like receptor (iKIR) for which the respective major histocompatibility complex class I ligand is absent on leukemic target cells can exert alloreactivity in vitro and in vivo. Several models regarding potential donor–patient constellations have been described that have demonstrated the clinical benefit of such alloreactivity of the donor-derived NK cell system in patients with adult acute myeloid leukemia and pediatric B-cell precursor acute lymphoblastic leukemia after allogeneic stem cell transplantation. Moreover, adoptive transfer of mature allogeneic NK cells in the nontransplant or transplant setting has been shown to be safe and feasible, whereas its effectivity needs further evaluation. NK cell therapy can be further improved by optimal donor selection based on phenotypic and genotypic properties, by adoptive transfer of NK cells with ex vivo or in vivo cytokine stimulation, by the use of antibodies to induce antibody-dependent cellular cytotoxicity or to block iKIRs, or by transduction of chimeric antigen receptors.

Resveratrol Enhances NKG2D-Mediated Cytotoxicity Against Leukemia Cells by Upregulating Both NKG2D Receptor on NK Cells As Well As NKG2D Ligands on Target Cells,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3236-3236
Author(s):  
Luis J. Espinoza ◽  
Akiyoshi Takami ◽  
Katsuya Nakata ◽  
Ly Quoc Trung ◽  
Kayoko Yamada ◽  
...  
Keyword(s):  
Nk Cells ◽  
Nk Cell ◽  
Conflicts Of Interest ◽  
Specific Inhibitor ◽  
Receptor Expression ◽  
Leukemia Cells ◽  
Target Cells ◽  
Lymphoid Leukemia ◽  
Nkg2d Ligands ◽  
Nkg2d Receptor

Abstract Abstract 3236 NKG2D is a powerful activating receptor expressed by natural killer (NK) cells that promotes cytotoxic lysis of cancer cells expressing NKG2D ligands (NKG2D-Ls). Pharmacological induction of NKG2D-Ls in malignant cells has been an attractive therapeutic approach but has gained poor clinical utility because currently available NKG2D-Ls inducers have been hampered either by their limited efficacy or by their associated toxicity. Resveratrol (RVT), a compound derived from several natural sources, has proved in vivo and in vitro potent anti-tumor effects against various cancers. Extensive research in the last decade has shown that such effects are mediated by targeting various molecules involved in the regulation of proliferation and cell survival and those include, NFκB, STAT3, ATM/ATR and ERK1/2. To date, it is unknown whether RVT has any effect on NKG2D-Ls expression. We report here NKG2D-Ls induction by RVT in a broad range of leukemia cells. RVT upregulated the NKG2D-Ls MICA/B, ULBP1, ULBP2 and ULBP3 in the myeloid leukemia cells OUN-1, NB4, THP-1 and KG1 and upregulated MICA/B, ULBP-1 and ULBP3 ligands in the lymphoid leukemia cells Jurkat and Molt-4. The upregulation of NKG2D-Ls by RVT was associated with increased transcription of each NKG2D-L gene. Ligand upregulation induced by RVT was prevented by cell pretreatment with caffeine, and inhibitor of ATM/ATR, which is the main signal regulator of NKG2D-Ls expression. Leukemia cells treated with RVT were more susceptible to killing by NK cells than untreated cells and the enhanced cytotoxicity of NK cells was blocked by the treatment of NK cells with anti-NKG2D monoclonal antibodies. Interestingly, the same concentration of RVT that effectively induced NKG2D-Ls in tumor cells, consistently upregulated NKG2D receptor expression in primary NK cells from healthy individuals and in the NK cell lines NKL and NK-92 and this effect was also associated with enhanced NKG2D-mediated NK cells cytotoxicity. RVT-induced NKG2D receptor enhancement in NK cells associated with the activation of the MAP kinase ERK1/2 and was prevented by the ERK1/2 specific inhibitor PD98059. Thus, RVT represents the first identified agent capable of activating both arms of the NKG2D axis. Since several clinical trials on RVT are ongoing, these previously unrecognized properties of this non toxic compound have an attractive immunotherapeutic potential. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Immunosenescence of Natural Killer Cells, Inflammation, and Alzheimer’s Disease

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Corona Solana ◽  
Raquel Tarazona ◽  
Rafael Solana
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Neurodegenerative Disorder ◽  
The Elderly ◽  
Lymphoid Cells ◽  
Target Cells ◽  
The Brain

Alzheimer’s disease (AD) represents the most common cause of dementia in the elderly. AD is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although the aetiology of AD is not clear, both environmental factors and heritable predisposition may contribute to disease occurrence. In addition, inflammation and immune system alterations have been linked to AD. The prevailing hypothesis as cause of AD is the deposition in the brain of amyloid beta peptides (Aβ). Although Aβ have a role in defending the brain against infections, their accumulation promotes an inflammatory response mediated by microglia and astrocytes. The production of proinflammatory cytokines and other inflammatory mediators such as prostaglandins and complement factors favours the recruitment of peripheral immune cells further promoting neuroinflammation. Age-related inflammation and chronic infection with herpes virus such as cytomegalovirus may also contribute to inflammation in AD patients. Natural killer (NK) cells are innate lymphoid cells involved in host defence against viral infections and tumours. Once activated NK cells secrete cytokines such as IFN-γ and TNF-α and chemokines and exert cytotoxic activity against target cells. In the elderly, changes in NK cell compartment have been described which may contribute to the lower capacity of elderly individuals to respond to pathogens and tumours. Recently, the role of NK cells in the immunopathogenesis of AD is discussed. Although in AD patients the frequency of NK cells is not affected, a high NK cell response to cytokines has been described together with NK cell dysregulation of signalling pathways which is in part involved in this altered behaviour.

scholarly journals Natural killer-mediated lysis of normal and malignant target cells, and its regulation by monocytes.

1985 ◽  
Vol 162 (2) ◽  
pp. 472-486 ◽  
Author(s):  
K Oshimi ◽  
Y Oshimi ◽  
M Satake ◽  
H Mizoguchi
Keyword(s):  
Nk Cells ◽  
Natural Killer ◽  
B Lymphocytes ◽  
Leukemia Cells ◽  
Target Cells ◽  
Large Granular Lymphocytes ◽  
Percoll Density Gradient ◽  
Granular Lymphocytes ◽  
Density Gradient Sedimentation

After depletion of monocytes, natural killer (NK) cells were partially purified from peripheral blood by Percoll density gradient sedimentation. The NK cells were then cultured for 1 d and assayed for their cytotoxicity against various types of normal and malignant target cells. All types of target cells tested were found to be susceptible to NK cells. The susceptible targets were autologous T and B lymphocytes, mitogen-induced T and B blasts, monocytes, large granular lymphocytes, autologous or allogeneic lymphoma and leukemia cells isolated from patients, and cultured cell lines, including those resistant to interferon-activated lymphocytes. Such a broad spectrum of cytotoxicity was demonstrated in 1 d of culture, and freshly prepared NK cells were not cytotoxic, or, if anything, were less cytotoxic. Monocytes and their supernatants, added throughout the course of culture, markedly inhibited the development of their cytotoxicity. These results may suggest that, although NK cells having ability to lyse autologous normal and malignant target cells are present in vivo, their lytic activity is regulated by coexisting monocytes.

scholarly journals Recognition of virus-infected cells by natural killer cell clones is controlled by polymorphic target cell elements.

1993 ◽  
Vol 178 (3) ◽  
pp. 961-969 ◽  
Author(s):  
M S Malnati ◽  
P Lusso ◽  
E Ciccone ◽  
A Moretta ◽  
L Moretta ◽  
...  
Keyword(s):  
T Cells ◽  
Nk Cells ◽  
Natural Killer ◽  
Target Cell ◽  
Nk Cell ◽  
Class I ◽  
Target Cells ◽  
Cell Recognition ◽  
Infected Cells ◽  
Nk Cell Recognition

Natural killer (NK) cells provide a first line of defense against viral infections. The mechanisms by which NK cells recognize and eliminate infected cells are still largely unknown. To test whether target cell elements contribute to NK cell recognition of virus-infected cells, human NK cells were cloned from two unrelated donors and assayed for their ability to kill normal autologous or allogeneic cells before and after infection by human herpesvirus 6 (HHV-6), a T-lymphotropic herpesvirus. Of 132 NK clones isolated from donor 1, all displayed strong cytolytic activity against the NK-sensitive cell line K562, none killed uninfected autologous T cells, and 65 (49%) killed autologous T cells infected with HHV-6. A panel of representative NK clones from donors 1 and 2 was tested on targets obtained from four donors. A wide heterogeneity was observed in the specificity of lysis of infected target cells among the NK clones. Some clones killed none, some killed only one, and others killed more than one of the different HHV-6-infected target cells. Killing of infected targets was not due to complete absence of class I molecules because class I surface levels were only partially affected by HHV-6 infection. Thus, target cell recognition is not controlled by the effector NK cell alone, but also by polymorphic elements on the target cell that restrict NK cell recognition. Furthermore, NK clones from different donors display a variable range of specificities in their recognition of infected target cells.

scholarly journals The Ly-49D Receptor Activates Murine Natural Killer Cells

1996 ◽  
Vol 184 (6) ◽  
pp. 2119-2128 ◽  
Author(s):  
L.H. Mason ◽  
S.K. Anderson ◽  
W.M. Yokoyama ◽  
H.R.C. Smith ◽  
R. Winkler-Pickett ◽  
...  
Keyword(s):  
Gene Family ◽  
Nk Cells ◽  
Natural Killer ◽  
Cell Function ◽  
Nk Cell ◽  
Cell Subset ◽  
Class I ◽  
Target Cells ◽  
Color Flow ◽  
Functional Capabilities

Proteins encoded by members of the Ly-49 gene family are predominantly expressed on murine natural killer (NK) cells. Several members of this gene family have been demonstrated to inhibit NK cell lysis upon recognizing their class I ligands on target cells. In this report, we present data supporting that not all Ly-49 proteins inhibit NK cell function. Our laboratory has generated and characterized a monoclonal antibody (mAb) (12A8) that can be used to recognize the Ly-49D subset of murine NK cells. Transfection of Cos-7 cells with known members of the Ly-49 gene family revealed that 12A8 recognizes Ly-49D, but also cross-reacts with the Ly-49A protein on B6 NK cells. In addition, 12A8 demonstrates reactivity by both immunoprecipitation and two-color flow cytometry analysis with an NK cell subset that is distinct from those expressing Ly-49A, C, or G2. An Ly-49D+ subset of NK cells that did not express Ly49A, C, and G2 was isolated and examined for their functional capabilities. Tumor targets and concanovalin A (ConA) lymphoblasts from a variety of H2 haplotypes were examined for their susceptibility to lysis by Ly-49D+ NK cells. None of the major histocompatibility complex class I–bearing targets inhibited lysis of Ly-49D+ NK cells. More importantly, we demonstrate that the addition of mAb 12A8 to Ly-49D+ NK cells can augment lysis of FcγR+ target cells in a reverse antibody-dependent cellular cytotoxicity–type assay and induces apoptosis in Ly49D+ NK cells. Furthermore, the cytoplasmic domain of Ly-49D does not contain the V/IxYxxL immunoreceptor tyrosine-based inhibitory motif found in Ly-49A, C, or G2 that has been characterized in the human p58 killer inhibitory receptors. Therefore, Ly-49D is the first member of the Ly-49 family characterized as transmitting positive signals to NK cells, rather than inhibiting NK cell function.

scholarly journals Inhibition of Enhancer of zeste homolog 2 (EZH2) induces natural killer cell-mediated eradication of hepatocellular carcinoma cells

2018 ◽  
Vol 115 (15) ◽  
pp. E3509-E3518 ◽  
Author(s):  
Suresh Bugide ◽  
Michael R. Green ◽  
Narendra Wajapeyee
Keyword(s):  
Hepatocellular Carcinoma ◽  
Nk Cells ◽  
Natural Killer ◽  
Nk Cell ◽  
Killer Cell ◽  
Transcriptional Level ◽  
Dependent Manner ◽  
Down Regulation ◽  
Nkg2d Ligands ◽  
Enhancer Of Zeste

Natural killer (NK) cell-mediated tumor cell eradication could inhibit tumor initiation and progression. However, the factors that regulate NK cell-mediated cancer cell eradication remain unclear. We determined that hepatocellular carcinoma (HCC) cells exhibit transcriptional down-regulation of NK group 2D (NKG2D) ligands and are largely resistant to NK cell-mediated eradication. Because the down-regulation of NKG2D ligands occurred at the transcriptional level, we tested 32 chemical inhibitors of epigenetic regulators for their ability to re-express NKG2D ligands and enhance HCC cell eradication by NK cells and found that Enhancer of zeste homolog 2 (EZH2) was a transcriptional repressor of NKG2D ligands. The inhibition of EZH2 by small-molecule inhibitors or genetic means enhanced HCC cell eradication by NK cells in a NKG2D ligand-dependent manner. Collectively, these results demonstrate that EZH2 inhibition enhances HCC eradication by NK cells and that EZH2 functions, in part, as an oncogene by inhibiting immune response.

Sign in / Sign up

Export Citation Format

Share Document