Impaired Natural Killer Cells Immune Synapse Formation in Acute Myeloid Leukemia.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2663-2663
Author(s):  
Dongxia Xing ◽  
Alan G. Ramsay ◽  
William Decker ◽  
Sufang Li ◽  
Simon Robinson ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Immune Suppression ◽  
Direct Contact ◽  
Myeloid Leukemia ◽  
Synapse Formation ◽  
Nk Cell ◽  
Immune Synapse ◽  
Acute Myeloid

Abstract Abstract 2663 Poster Board II-639 Natural killer (NK) cells are an important component of the innate immune surveillance of tumor cells. Defective NK cell function has been correlated with poor prognosis in acute myeloid leukemia (AML). It is well established that NK cell-mediated cytolytic activity is significantly diminished in AML patients; the mechanisms of this hypo-function are not well understood. Identifying mechanisms of tumor-induced immune suppression of lymphocytes function will aid the development of effective immunotherapeutic strategies. In the present study we examined the molecular basis for impaired NK cell responses in AML and demonstrate impaired NK cell immunological synapse formation. Confocal microscopy was used to visualize F-actin polymerization at the immune synapse between CD56+ CD3- NK cells and autologous AML blasts. We identified a significant reduction in formation of the NK cell immune synapse (NKIS) (p<0.001) from AML patients compared healthy donors (> 70% reduction). This defect was induced by direct tumor contact since NK cell defects were induced in healthy NK cells when they were co-cultured (in direct contact) for 48 hr with allogeneic AML blasts, but not with healthy allogeneic monocytes (P < 0.01). In control transwell co-culture experiments, where the NK cells and AML blast were not in direct contact, we did not observe the induced defect. We examined the molecular nature of the AML blast induced defect by quantifying recruitment of a number of these NK cell adhesion and cytoskeletal signaling proteins to the immune synapse. Following primary co-culture with AML blasts, healthy NK cells showed significantly reduced recruitment of integrin LFA-1, CD2, Lck, WASP, and tyrosine-phosphorylated protein to the NK-AML target interactions synapse (P < 0.001). These studies demonstrate a role for the tumor induced immune suppression of NK cells and will aid in the development of immunotherapeutic approaches targeting AML. Disclosures: No relevant conflicts of interest to declare.

CD137L Reverse the Immunological Synapse Defects of Natural Killer Cells in Acute Myeloid Leukemia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 246-246
Author(s):  
Dongxia Xing ◽  
Alan G. Ramsay ◽  
William Decker ◽  
Dean A. Lee ◽  
Simon Robinson ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Synapse Formation ◽  
Immunological Synapse ◽  
Leukemic Cells ◽  
Cytolytic Function ◽  
Immunological Synapses ◽  
Acute Myeloid

Abstract Abstract 246 Natural killer (NK) cells are an innate component of immune system that can produce a graft vs. leukemia (GVL) effect after stem cell transplantation. NK cells derived from acute myeloid leukemia (AML) patients are defective in their cytolytic function against leukemic cells. In order to better understand the mechanism of this defect, we performed functional assays examining immunological synapse formation of AML patient NK cells with autologous and allogeneic primary AML cells acting as antigen-presenting cells (APCs). Confocal microscopy was used to image and score F-actin polymerization at the immunological synapse between patient NK cells and leukemic cells. Accumulation of F-actin beneath the area of the NK: APC contact site is a hallmark of NK lytic synapses and allows signaling molecules to regulate appropriate activation and effector function. AML patient derived NK cells (AML-NK cells) formed significantly fewer synapses with autologous leukemia cells than healthy donor NK cells (12% versus 30%, n = 16. p > 0.001). Moreover, AML-NK cells were defective in their ability to recruit the key receptor NKG2D and the signaling molecule phosphotyrosine to immunological synapse contact sites. Signaling through the costimulatory ligand4-1BB-L (CD137L) has been shown to activate T cells, enhance antitumor responses and has multiple immunomodulatory effects on dendritic cells and NK cells. We postulated that AML-NK cells could be activated for enhanced cytolytic activity using artificial APCs generated to express CD137L. To test this, we setup co-culture assays using AML-NK cells and artificial CD137L-APCs before subsequent examination of immunological synapse function with AML blasts. Stimulated AML-NK cells that formed cell conjugate interactions with AML blasts, showed a significant increase in formation of immunological synapses compared to unstimulated AML-NK cells. The number of AML-NK/AML blast immunological synapses increased 16 hours after stimulation and peaked at approximately 72 hours. CD137L stimulation of AML-NK cells was also associated with increased cytotoxic function against primary AML cells (n = 6, p <0.01). Furthermore, CD137L stimulation increased recruitment of tyrosine-phosphorylated proteins at AML-NK immunological synapses compared with unstimulated control experiments (RRI 4.1 versus 2.3, n = 3, p < 0.01). Taken together, our data suggests that immune functional suppression of AML-NK cells in leukemia patients can be reversed by CD137L activation signaling, resulting in enhanced F-actin synapse formation, phosphotyrosine signaling, and cytolytic function. Thus, enhanced recruitment of signaling molecules to the NKIS may represent a novel immunomodulatory function of CD137L in the NK cell–mediated killing of AML cells. These findings should aid development of new immune based therapies for leukemia. Disclosures: Gribben: Roche: Honoraria; Celgene: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria; Pharmacyclics: Honoraria.

Successful transfer of alloreactive haploidentical KIR ligand-mismatched natural killer cells after infusion in elderly high risk acute myeloid leukemia patients

Blood ◽  
2011 ◽  
Vol 118 (12) ◽  
pp. 3273-3279 ◽  
Author(s):  
Antonio Curti ◽  
Loredana Ruggeri ◽  
Alessandra D'Addio ◽  
Andrea Bontadini ◽  
Elisa Dan ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
High Risk ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Median Number ◽  
Active Disease ◽  
Acute Myeloid

Abstract Thirteen patients with acute myeloid leukemia, 5 with active disease, 2 in molecular relapse, and 6 in morphologic complete remission (CR; median age, 62 years; range, 53-73 years) received highly purified CD56+CD3− natural killer (NK) cells from haploidentical killer immunoglobulin-like receptor–ligand mismatched donors after fludarabine/cyclophosphamide immunosuppressive chemotherapy, followed by IL-2. The median number of infused NK cells was 2.74 × 106/Kg. T cells were < 105/Kg. No NK cell–related toxicity, including GVHD, was observed. One of the 5 patients with active disease achieved transient CR, whereas 4 of 5 patients had no clinical benefit. Both patients in molecular relapse achieved CR that lasted for 9 and 4 months, respectively. Three of 6 patients in CR are disease free after 34, 32, and 18 months. After infusion, donor NK cells were found in the peripheral blood of all evaluable patients (peak value on day 10). They were also detected in BM in some cases. Donor-versus-recipient alloreactive NK cells were shown in vivo by the detection of donor-derived NK clones that killed recipient's targets. Adoptively transferred NK cells were alloreactive against recipient's cells, including leukemia. In conclusion, infusion of purified NK cells is feasible in elderly patients with high-risk acute myeloid leukemia. This trial was registered at www.clinicaltrial.gov as NCT00799799.

scholarly journals Single-cell profiling reveals the trajectories of natural killer cell differentiation in bone marrow and a stress signature induced by acute myeloid leukemia

2020 ◽  
Author(s):  
Adeline Crinier ◽  
Pierre-Yves Dumas ◽  
Bertrand Escalière ◽  
Christelle Piperoglou ◽  
Laurine Gil ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Single Cell ◽  
Natural Killer ◽  
Rna Sequencing ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Single Cell Rna Sequencing ◽  
Acute Myeloid

SummaryNatural killer (NK) cells are innate cytotoxic lymphoid cells (ILCs) involved in the killing of infected and tumor cells. Among human and mouse NK cells from the spleen and blood, we previously identified by single-cell RNA sequencing (scRNAseq) two similar major subsets, NK1 and NK2. Using the same technology, we report here the identification, by single-cell RNA sequencing (scRNAseq), of three NK cell subpopulations in human bone marrow. Pseudotime analysis identified a subset of resident CD56bright NK cells, NK0 cells, as the precursor of both circulating CD56dim NK1-like NK cells and CD56bright NK2-like NK cells in human bone marrow and spleen under physiological conditions. Transcriptomic profiles of bone marrow NK cells from patients with acute myeloid leukemia (AML) exhibited stress-induced repression of NK cell effector functions, highlighting the profound impact of this disease on NK cell heterogeneity. Bone marrow NK cells from AML patients exhibited reduced levels of CD160, but the CD160high group had a significantly higher survival rate.

Adoptive Immunotherapy with Haploidentical Kir Ligand-Mismatched Natural Killer Cells In Elderly High Risk Acute Myeloid Leukemia Patients: Biological and Clinical Results of A Pilot Study

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4287-4287
Author(s):  
Antonio Curti ◽  
Loredana Ruggeri ◽  
Alessandra D'Addio ◽  
Andrea Bontadini ◽  
Valeria Giudice ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
High Risk ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Conflicts Of Interest ◽  
Interleukin 2 ◽  
Active Disease ◽  
Acute Myeloid

Abstract Abstract 4287 Purpose: To evaluate safety, feasibility and anti-leukemia potential of haploidentical KIR-L mismatched natural killer (NK) cell infusion in elderly high risk acute myeloid leukemia (AML) patients. Patients and Methods: Thirteen patients (5 active disease, 2 molecular relapse and 6 complete remissions) with median age 62 years (range 53–73) received NK cell infusion after immunosuppressive chemotherapy (fludarabine/cyclophosphamide), followed by interleukin-2. Highly purified CD56+CD3- NK cells from haploidentical KIR-L mismatched donors were used. The median number of infused NK cells was 2.74 × 106/Kg. T cells were less than 105/Kg. NK cell chimerism, phenotyping, and functional assays were performed. Results: No significant toxicity, including graft versus host disease, related to NK cell infusion was observed. Among patients with active disease, 1/5 obtained transient complete remission (CR), whereas 4/5 patients had no clinical benefit. Both patients in molecular relapse obtained CR, which lasted 9 and 4 months. Three/6 patients in morphologic CR are disease-free after 34, 32 and 18 months. Donor NK cells were demonstrated in the peripheral blood (PB) of all evaluable patients with a peak at day 10 after infusion and, in some cases, also in the bone marrow (BM). NK alloreactivity was demonstrated in vivo by the detection of donor-derived postinfusion NK clones capable of killing recipient targets. Conclusion: Infusion of purified CD56+CD3- NK cells is feasible and safe in elderly high risk AML patients. Adoptively transferred NK cells, which can be detected in PB and BM after infusion, are alloreactive against recipient cells and may induce an anti-leukemic activity. Disclosures: No relevant conflicts of interest to declare.

scholarly journals CD38 knockout natural killer cells expressing an affinity optimized CD38 chimeric antigen receptor successfully target acute myeloid leukemia with reduced effector cell fratricide.

Haematologica ◽  
2020 ◽  
Author(s):  
Mark Gurney ◽  
Arwen Stikvoort ◽  
Emma Nolan ◽  
Lucy Kirkham-McCarthy ◽  
Stanislav Khoruzhenko ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Cell Therapy ◽  
Nk Cells ◽  
Natural Killer ◽  
Chimeric Antigen Receptor ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Cd38 Expression ◽  
Nk Cell Therapy ◽  
Acute Myeloid

There is a strong biological rationale for the augmentation of allogeneic natural killer (NK) cell therapies with a chimeric antigen receptor (CAR) to enhance acute myeloid leukemia (AML) targeting. CD38 is an established immunotherapeutic target in multiple myeloma and under investigation as a target antigen in AML. CD38 expression on NK cells and its further induction during ex vivo NK cell expansion represents a barrier to the development of a CD38 CAR-NK cell therapy. We set out to develop a CD38 CAR-NK cell therapy for AML, first by using an NK cell line which has low baseline CD38 expression and subsequently healthy donor expanded NK cells. To overcome anticipated fratricide due to NK cell CD38 expression when using primary expanded NK cells, we applied CRISPR/Cas9 genome editing to disrupt the CD38 gene during expansion achieving a mean knockdown efficiency of 84%. The resulting CD38 KD expanded NK cells, after expression of an affinity optimized CD38 CAR, showed reduced NK cell fratricide and an enhanced ability to target primary AML blasts. Furthermore, the cytotoxic potential of CD38 CAR-NK cells was augmented by pre-treatment of the AML cells with all-trans retinoic acid which drove enhanced CD38 expression offering a rational combination therapy. These findings support the further investigation of CD38 KD - CD38 CAR-NK cells as a viable immunotherapeutic approach to the treatment of AML.

scholarly journals Natural Killer Cells Enhance Transplantation Outcomes

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. SCI-27-SCI-27
Author(s):  
Sarah A. Cooley
Keyword(s):  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Gene Content ◽  
Graft Vs Host Disease ◽  
Cytokine Stimulation ◽  
Cmv Reactivation ◽  
Acute Myeloid

Natural killer (NK) cells, the first lymphocyte subset to reconstitute after hematopoietic cell transplantation (HCT), may enhance transplant outcomes by killing virally-infected or malignant cells to reduce relapse and treatment-related mortality by promoting engraftment and by reducing graft vs. host disease. The function of NK cells is regulated by the net balance of signaling via several families of activating or inhibitory receptors. The killer-cell immunoglobulin-like receptor (KIR) family is of particular importance in HCT because of its interactions with class I human leukocyte antigen (HLA) molecules. HLA-C, HLA-Bw4 and some HLA-A allotypes function as ligands for the inhibitory KIR receptors, thus mediating tolerance to self. HLA-mismatched HCT may generate alloreactive NK cells in the recipient when there is a KIR-ligand mismatch at HLA-C, B or A. The proof of concept for this principle was established by the Perugia group in haploidentical transplants, where KIR-ligand mismatch was associated with reduced relapse in patients with acute myeloid leukemia. Subsequent groups have studied this and other algorithms, including KIR ligand absence or KIR-KIR ligand genotyping to evaluate the role of NK cells in mediating protection after allogeneic HCT. Human KIR haplotypes are defined by gene content, where the A haplotype contains mainly inhibitory KIR, and B haplotypes contain more activating KIR. Unrelated donors with more KIR B haplotype genes have been associated with protection from relapse and improved survival in AML, an effect which is enhanced in recipients expressing HLA-C1. Although NK cells mediate beneficial effects after HCT, compared to adult donor NK cells, engrafting NK cells are immature and hyporesponsive when exposed to tumor targets. Recently human cytomegalovirus (CMV) has been shown to drive the expansion of a population of long-lived CD57+NKG2C+ NK cells with attributes of immunologic memory. These cells have heightened capacity for cytokine production or cytolytic response to tumor targets. Several groups have shown that CMV reactivation correlates with reduced relapse after allogeneic HCT, suggesting that these CMV “adaptive” NK cells may contribute to the graft vs. leukemia effect. Strategies to isolate and expand “adaptive” NK cells without clinical CMV reactivation are being explored. Lastly, adult donor NK cells are an appealing population to exploit for adoptive cellular therapy. Donors can be chosen based on predicted NK cell alloreactivity or based on KIR gene content. Adoptively transferred NK cells which expand and proliferate in vivo in response to cytokine stimulation (IL-2 or IL-15) are potent anti-tumor effectors which do not mediate graft vs. host disease. Several groups are using haploidentical adult NK cell products to treat acute myeloid leukemia, multiple myeloma, lymphoma, myelodysplasic syndrome and a variety of solid tumors. Various approaches using adoptive transfer of NK cells, together with HCT, targeting antibodies which mediate antibody dependent cellular cytotoxicity, or cytokine stimulation are being tested clinically. In summary, we are just beginning to define the complexity of NK cell interactions with HLA and other ligands and to describe different properties of various NK cell subsets to develop more sophisticated strategies to exploit NK cells to treat cancer. Disclosures No relevant conflicts of interest to declare.

scholarly journals Bone marrow infiltrated natural killer cells predicted the anti-leukemia activity of MCL1 or BCL2 inhibitors in acute myeloid leukemia

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Yu-Jun Dai ◽  
Si-Yuan He ◽  
Fang Hu ◽  
Xue-Ping Li ◽  
Jian-Ming Zhang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Treatment Strategies ◽  
Leukemia Treatment ◽  
Acute Myeloid

AbstractAcute myeloid leukemia (AML) is still incurable due to its heterogeneity and complexity of tumor microenvironment. It is imperative therefore to understand the molecular pathogenesis of AML and identify leukemia-associated biomarkers to formulate effective treatment strategies. Here, we systematically analyzed the clinical characters and natural killer (NK) cells portion in seventy newly-diagnosis (ND) AML patients. We found that the proportion of NK cells in the bone marrow of ND-AML patients could predict the prognosis of patients by analyzing the types and expression abundance of NK related ligands in tumor cells. Furthermore, MCL1 inhibitor but not BCL2 inhibitor combined with NK cell-based immunotherapy could effectively improve the therapeutic efficiency via inhibiting proliferation and inducing apoptosis of AML primary cells as well as cell lines in vitro. There results provide valuable insights that could help for exploring new therapeutic strategies for leukemia treatment.

scholarly journals Natural Killer Cell Derived Exosomes As a Novel Therapeutic for Acute Myeloid Leukemia

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 5226-5226
Author(s):  
Michael Boyiadzis ◽  
Chang Sook Hong ◽  
Theresa L Whiteside
Keyword(s):  
Flow Cytometry ◽  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Granzyme B ◽  
Killer Cell ◽  
Primary Leukemia ◽  
Acute Myeloid

Abstract Introduction: Natural killer (NK) cells play a critical role in the innate immune response through their capacity to lyse malignant cells without prior antigen-specific priming. NK cells have been evaluated for safety and efficacy in acute myeloid leukemia (AML), both in the transplant and non-transplant settings. Exosomes, small, 30-150 nm-sized extracellular vesicles originating from the endocytic compartment of parent cells, have recently emerged as a universal intercellular communication system. Exosomes are released by virtually all cells and carry proteins, lipids, and nucleic acids from the parent to recipient cells at short and long distances. The exosome molecular cargo reflects the content of the parent cell and is delivered to recipient cells in a membrane-protected vesicle. We hypothesize that exosomes produced by human activated NK cells carry the machinery necessary for the killing of leukemic cells. Methods: Venous blood (20-50 mL) was obtained from healthy donors (n=10). NK cells were isolated using Ab-based immunomagnetic selection from the recovered peripheral blood mononuclear cells. NK cells were cultured in the presence of interleukin-2 and interleukin-15, and NK-cell supernatants were used for exosome isolation by size exclusion chromatography. Protein levels, numbers and size (qNano), and exosome morphology (transmission electron microscopy) were determined. Exosome cargos were studied by Western blots and/or flow cytometry for NK cell activating and inhibitory receptors, immune inhibitory molecules and for perforin and granzyme B. Cytotoxicity of the NK cell-derived exosomes for K562 targets, AML cell lines (Kasumi, MLL-1) and primary leukemia blasts was measured using flow cytometry-based assays. Results: Activated human NK cells produced large quantities of exosomes. PKH-26-labeled NK cell-derived exosomes were avidly taken up by leukemic blasts. NK cell derived exosomes carried activating NK cell receptor NKG2D, natural cytotoxicity receptors, perforin, granzyme B, transforming growth factor beta (TGF-β), killer-cell immunoglobulin-like receptors and PD-1. NK cell derived exosomes mediated anti-leukemia activity against K562 targets, AML cell lines and primary leukemia blasts. Lysis of leukemic blasts by NK cell-derived exosomes was exosome concentration dependent. Conclusion: We report that NK cell derived exosomes have anti leukemia activity in vitro. These data provide a foundation for the future development of new therapeutic strategies using NK cell-derived exosomes for the elimination of leukemia. Disclosures No relevant conflicts of interest to declare.

scholarly journals Chronic IL-15 Stimulation and Impaired mTOR Signaling and Metabolism in Natural Killer Cells During Acute Myeloid Leukemia

2021 ◽  
Vol 12 ◽  
Author(s):  
Berna Bou-Tayeh ◽  
Vladimir Laletin ◽  
Nassim Salem ◽  
Sylvaine Just-Landi ◽  
Joanna Fares ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Myeloid Leukemia ◽  
Nk Cell ◽  
Mtor Signaling ◽  
Cytokine Signaling ◽  
Type I ◽  
Acute Myeloid

Natural Killer (NK) cells are potent anti-leukemic immune effectors. However, they display multiple defects in acute myeloid leukemia (AML) patients leading to reduced anti-tumor potential. Our limited understanding of the mechanisms underlying these defects hampers the development of strategies to restore NK cell potential. Here, we have used a mouse model of AML to gain insight into these mechanisms. We found that leukemia progression resulted in NK cell maturation defects and functional alterations. Next, we assessed NK cell cytokine signaling governing their behavior. We showed that NK cells from leukemic mice exhibit constitutive IL-15/mTOR signaling and type I IFN signaling. However, these cells failed to respond to IL-15 stimulation in vitro as illustrated by reduced activation of the mTOR pathway. Moreover, our data suggest that mTOR-mediated metabolic responses were reduced in NK cells from AML-bearing mice. Noteworthy, the reduction of mTOR-mediated activation of NK cells during AML development partially rescued NK cell metabolic and functional defects. Altogether, our data strongly suggest that NK cells from leukemic mice are metabolically and functionally exhausted as a result of a chronic cytokine activation, at least partially IL-15/mTOR signaling. NK cells from AML patients also displayed reduced IL-2/15Rβ expression and showed cues of reduced metabolic response to IL-15 stimulation in vitro, suggesting that a similar mechanism might occur in AML patients. Our study pinpoints the dysregulation of cytokine stimulation pathways as a new mechanism leading to NK cell defects in AML.

Defective Natural Killer (NK) Receptor Expression and Effector Function in Acute Myeloid Leukemia Partially Normalize At Remission and Predict Response to Chemotherapy.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2591-2591
Author(s):  
Kate Stringaris ◽  
Takuye Sekine ◽  
Ahmad Khoder ◽  
Abdullah Alsuliman ◽  
Pavlu Jiri ◽  
...  
Keyword(s):  
Acute Myeloid Leukemia ◽  
Nk Cells ◽  
Natural Killer ◽  
Induction Chemotherapy ◽  
Myeloid Leukemia ◽  
Healthy Donor ◽  
Nk Cell ◽  
Effector Function ◽  
And Function ◽  
Acute Myeloid

Abstract Abstract 2591 Despite favorable initial responses to induction chemotherapy, most patients with acute myeloid leukemia (AML) will relapse. We hypothesized that just as cancers evade immunosurveillance by suppressing the immune response (“immunoediting”), remission and relapse in AML may be determined by similar immune interactions. After stem cell transplantation natural killer (NK) cells exert powerful allogeneic graft vs. leukemia effects. To explore immunosurveillance by autologous NK cells and immunoediting by AML blasts, we prospectively analyzed NK surface phenotype and function in AML patients at presentation and following remission induction. Using multi-color flow cytometry, we analyzed the surface expression of natural cytotoxicity receptors (NCRs), killer immunoglobulin receptors (KIRs) and C-type lectins directly ex-vivo in 32 consecutive patients at presentation and following complete remission (CR) in 12 patients for whom remission samples were available. Results were compared with 15 healthy controls. NK effector function in AML was measured against K562 leukemia targets and autologous AML blasts by CD107a degranulation and interferon-gamma (IFNγ) and TNF-alpha (TNFα) production. NK cells from 32 patients with AML at diagnosis had an abnormal phenotype compared to controls, with downregulation of the activatory receptor NKp46 (MFI 187± 15 vs. 266± 24, p=0.007) and upregulation of the inhibitory receptor NKG2A (mean 45%± 4.2 vs. 32%± 2.7, p=0.046). Moreover, AML-NK cells were defective in their effector function with significantly reduced CD107a degranulation (5% vs. 11%, p=0.0002), TNFα (1% vs. 3%, p=0.008) and IFNγ production (1% vs. 5%, p=<0.0001). In the 12 patients who achieved remission following induction chemotherapy NKp46 expression normalized from an MFI 122 at presentation to 242 (p=0.01); however, NKG2A expression continued to increase (45% vs. 61%, p=0.008). At remission AML-NK cells displayed CD107a degranulation levels comparable to that of healthy donor NK cells (9% vs. 11%, p=0.4). In contrast, TNFα and IFNγ production only partially normalized (2% vs. 3%, p=0.3) and (3% vs. 5%, p=0.04), respectively. AML patients with NKG2A overexpression (> median of 32.6%) at diagnosis were significantly less likely to achieve CR post chemotherapy compared to those with lower NKG2A expression (78% vs. 32% p= 0.041). Furthermore, patients who failed to respond to induction chemotherapy had significantly reduced NK effector function at diagnosis compared to normal controls (mean TNFα production 1% cf. 5% p=0.019). We then sought for evidence of immunoediting by AML on NK cell phenotype and function. Co-incubation of healthy donor NK cells with primary AML blasts for 24 hours resulted in significant reduction in TNFα production (p=0.02), IFNγ production (p=0.01) and a trend to reduced CD107a degranulation (p=0.07) against K562 leukemia targets. Our results indicate that AML blasts can produce long-lasting changes in NK cell subsets and impair their effector function and favouring immune escape from NK cell control. This work justifies larger prospective analyses to relate NK-based prognostic factors to classical predictive factors for remission and relapse, and should guide the development of NK cell based immunotherapy to improve outcome in AML. Disclosures: No relevant conflicts of interest to declare.

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