NK Cell Activating Receptor NKG2D Research Articles

Tinostamustine (EDO-S101), an Alkylating Deacetylase Inhibitor, Enhances the Efficacy of Daratumumab in Multiple Myeloma by Upregulation of CD38 and NKG2D Ligands.

Multiple myeloma is a malignancy characterized by the accumulation of malignant plasma cells in bone marrow and the production of monoclonal immunoglobulin. A hallmark of cancer is the evasion of immune surveillance. Histone deacetylase inhibitors have been shown to promote the expression of silenced molecules and hold potential to increase the anti-MM efficacy of immunotherapy. The aim of the present work was to assess the potential effect of tinostamustine (EDO-S101), a first-in-class alkylating deacetylase inhibitor, in combination with daratumumab, an anti-CD38 monoclonal antibody (mAb), through different preclinical studies. Tinostamustine increases CD38 expression in myeloma cell lines, an effect that occurs in parallel with an increment in CD38 histone H3 acetylation levels. Also, the expression of MICA and MICB, ligands for the NK cell activating receptor NKG2D, augments after tinostamustine treatment in myeloma cell lines and primary myeloma cells. Pretreatment of myeloma cell lines with tinostamustine increased the sensitivity of these cells to daratumumab through its different cytotoxic mechanisms, and the combination of these two drugs showed a higher anti-myeloma effect than individual treatments in ex vivo cultures of myeloma patients' samples. In vivo data confirmed that tinostamustine pretreatment followed by daratumumab administration significantly delayed tumor growth and improved the survival of mice compared to individual treatments. In summary, our results suggest that tinostamustine could be a potential candidate to improve the efficacy of anti-CD38 mAbs.

Efficacy of Human iPSC-Derived CAR-NK Cells Targeting Multiple Myeloma Cells

NK cells armed with chimeric antigen receptors (CAR) enable NK cells specifically to target cancer cells by recognizing tumor associated antigens. Previous studies have proven that human iPSC-derived CAR-NK cells have enhanced anti-tumor activity. Targeted B-cell maturation antigen (BCMA) therapy for relapsed refractory MM (rrMM) has been widely used with antibody-drug conjugate (ADC), bispecific antibodies, and CART cells, which has produced a rapid response, but relapse is common. Recent work has revealed GPRC5D as an alternative target in MM for immunotherapy and patients who have previously received anti-BCMA therapy have responded to GPRC5D CART cells. To assess target GPRC5D therapy with CAR-NK cells, which may in future serve as allogeneic immunotherapy, we transduced anti-GPRC5D CAR into an iPSC line derived from a healthy donor using a piggybac transposon system. More than 97% of CAR inserted-iPSCs (CAR-iPSCs) expressed anti-GPRC5D scFV with a similar expression level identified in CAR-iPSC-derived-NK cells (CAR-iNK, 92.7%). The anti-GPRC5D CAR-iNK demonstrated high purity (>99.9% for CD45 + and CD56 +) and expressed a high level of CD16 (63.6%), the NK cell activating receptor NKG2D (96.3%) and NKp30 (98.7%), and the co-stimulatory receptors CD244 (99.6%) and CD226 (97.8%). Nonetheless expression of TCR⍺β and TCRƳ- was relatively low (<2%). Cytotoxicity assay revealed that anti-GPRC5D CAR-iNK had similar cytotoxicity against K562 cells (No GPRC5D antigen) to cord blood-derived NK cells (CB-NK), wide type (WT) iNK and anti-BCMA CAR-iNK. Cytotoxicity was dose-dependent indicating that these NK cells had similar innate anti-cancer cytotoxicity. When incubated at a ratio of 4:1 with NCI-H929 cells (MM) for 4 hours, which express a high level of both BCMA and GPRC5D, anti-GPRC5D CAR-iNK demonstrated an overwhelming advantage (approximately 90% killing rate) over the CB-NK (no killing) and WT iNK (around 10% killing rate). Furthermore, the anti-GPRC5D CAR-iNK also showed superior cytotoxicity to anti-BCMA CAR-iNK (Figure 1), indicating that GPRC5D may be a more efficient target for CAR-NK-based immunotherapy in MM. We further confirmed that anti-GPRC5D CAR-NK have acceptable cytotoxicity to NCI-H929 and OPM-2 cells, even when transported over a long distance (more than 2000 km) and following cryopreservation. The lower expression by OPM-2 cells of BCMA and GPRC5D compared with NCI-H929 indicates that both fresh and cryopreserved anti-GPRC5D CAR-iNK can specifically target MM with a higher and lower expression of GPRC5D. In addition, cryopreserved anti-GPRC5D CAR-iNK cells maintain comparable antigen-specific cytotoxicity in vitro, and demonstrate the ability to reduce tumor burden in an antigen-specific manner in an OPM-2 xenograft model. Our results demonstrate that genome-engineered human iPSCs can provide an unlimited source for manufacturing scalable, off-the-shelf, and cost-effective CAR-NK cells, and GPRC5D is a potent immunotherapeutic target in multiple myeloma.

Targeting WEE1/AKT Restores p53-Dependent Natural Killer-Cell Activation to Induce Immune Checkpoint Blockade Responses in "Cold" Melanoma.

Immunotherapy has revolutionized cancer treatment. Unfortunately, most tumor types do not respond to immunotherapy due to a lack of immune infiltration or "cold" tumor microenvironment (TME), a contributing factor in treatment failure. Activation of the p53 pathway can increase apoptosis of cancer cells, leading to enhanced antigen presentation, and can stimulate natural killer (NK) cells through expression of stress ligands. Therefore, modulation of the p53 pathway in cancer cells with wild-type TP53 has the potential to enhance tumor immunogenicity to NK cells, produce an inflammatory TME, and ultimately lead to tumor regression. In this study, we report simultaneous targeting of the AKT/WEE1 pathways is a novel and tolerable approach to synergistically induce p53 activation to inhibit tumor development. This approach reduced the growth of melanoma cells and induced plasma membrane surface localization of the ER-resident protein calreticulin, an indicator of immunogenic cell death (ICD). Increase in ICD led to enhanced expression of stress ligands recognized by the activating NK-cell receptor NKG2D, promoting tumor lysis. WEE1/AKT inhibition resulted in recruitment and activation of immune cells, including NK cells, in the TME, triggering an inflammatory cascade that transformed the "cold" TME of B16F10 melanoma into a "hot" TME that responded to anti-programmed cell death protein 1 (anti-PD-1), resulting in complete regression of established tumors. These results suggest that AKT/WEE1 pathway inhibition is a potential approach to broaden the utility of class-leading anti-PD-1 therapies by enhancing p53-mediated, NK cell-dependent tumor inflammation and supports the translation of this novel approach to further improve response rates for metastatic melanoma.

Abstract 1591: FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy

Abstract Cancer immunotherapies have revolutionized cancer treatment by showing clinical efficacy across multiple cancer indications. However, tumor heterogeneity and evasion from host immune cell surveillance often limit the durability and efficacy of these strategies as monotherapies. Consequently, it is becoming common practice to combine existing anticancer treatments and novel immunotherapies to maximize clinical efficacy. The pan tumor-associated antigens MICA and MICB (MICA/B) are surface proteins induced by cellular stress, often associated with tumorigenesis, and are recognized by the NK cell activating receptor NKG2D. To evade immune recognition, cancer cells often proteolytically shed the membrane distal domains of MICA/B, leading to reduced NKG2D recognition. To combat this pervasive tumor escape mechanism and create a ubiquitous cancer targeting platform, we have developed a novel CAR-iPSC-derived NK (iNK) cell that targets the conserved α3 domain of MICA/B, rendering it resistant to inhibition by shed MICA/B. To enhance effector cell function, persistence and multi-antigen capacity, further genetic editing at the iPSC stage was conducted to equip the CAR-iNK cells with a unique IL-15/IL-15 receptor fusion, the knockout of CD38 and a novel high-affinity, non-cleavable CD16 (hnCD16) to enhance antibody-dependent cellular cytotoxicity (ADCC). In this study, we evaluated the function of multiplexed engineered MICA/B CAR iNK cells (termed FT536) in combination with monoclonal antibodies (mAbs), to elicit multi-antigen targeting, and radiation therapy, to augment surface MICA/B expression. FT536 showed superior in vitro cytotoxicity and in vivo tumor control against an array of MICA/B expressing tumor lines. Furthermore, ADCC, induced in combination with cetuximab or trastuzumab, enhanced the potency of FT536 against various solid tumor lines (p <0.05). To demonstrate the capability of FT536 to synergize with irradiation therapy, we utilized a panel of tumor lines, divergent in tissue origin and MICA/B expression profiles. This approach highlighted that irradiation of the SK-BR-3 tumor line, a breast adenocarcinoma that expresses low levels of surface MICA/B and high levels of EGFR, induced the upregulation of MICA/B expression (p <0.05). As anticipated, FT536 exhibited enhanced, CAR-dependent cytotoxicity against irradiated SK-BR-3 cells. Ongoing work is focused on the development of in vivo models that combine FT536 with in situ tumor irradiation and mAbs in order to promote durable responses and the elimination of resistant and heterogenous cancer cells. These data demonstrate successful targeting of MICA/B positive tumors by FT536 can be augmented by mAb and radiation therapies as first-of-kind combinatorial strategies to broadly target escape-prone tumors. Citation Format: John Goulding, Robert Blum, Bryan Hancock, Moyar Ge, Brian Groff, Soheila Shirinbak, Joy Grant, Martin Hosking, Mochtar Pribadi, Yijia Pan, Hui-Yi Chui, Shohreh Sikaroodi, Lauren Fong, Janel Huffman, Wen-I Yeh, Chia-Wei Chang, Thomas Dailey, Miguel Meza, Cokey Nguyen, Lucas Ferrari de Andrade, Tom Lee, Ryan Bjordahl, Kai W. Wucherpfennig, Bahram Valamehr. FT536: Preclinical development of a novel off-the-shelf CAR-MICA/B NK cell immunotherapy combined with radiation and antibody treatments as a first-of-kind pan-cancer targeting strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1591.

Induction of Innate Immune Visibility of Neuroendocrine Tumors Potentiates Immune Responses and Tumor Rejection

Abstract Natural killer (NK) cells serve as an important role in suppressing tumor growth by directly attacking malignant cells. These cells recognize the tumor cells through moleclar patterns associated with oncogenic transformation. NKG2D ligands (NKG2DLs) are one of these markers present on tumor cells which can activate NK cells and T cells by interacting with NKG2D receptors on these lymphocytes. Majority of tumors express NKG2DLs. Interestingly, tumors carrying neuroendocrine features such as small cell lung cancer (SCLC) and neuroblastoma express very low level of ligands for NK cell activating receptor NKG2D (MICA, MICB, ULBP1, ULBP2, ULBP3), which may help them escape from innate immune surveillance. Further characterization of SCLC immune environment showed reduced antigen presentation, reduced infiltration of total immune cells specifically NK cells, as compared to NSCLC, a more immunogenic tumor. Transcriptional inducers of NKG2DLs did not induce NKG2DL in SCLCs due to hypo-acetylation of MICA/B region. Histone deacetylase (HDAC) inhibitors were able to induce NKG2DL on tumor cell surface. Restoring NKG2DL in preclinical SCLC and neuroblastoma models either by ectopic expression or HDAC inhibitors stimulated direct NK cell killing in co-culture assays. NKG2DL stimulation also caused potentiation of antibody directed therapies such as CD3-EpCAM in neuroendocrine tumors. In vivo studies showed suppressed tumor growth and metastasis in an NK and CD8 T cell dependent manner when NKG2DLs are stimulated. We conclude that: restoring innate immune visibility can target neuroendocrine tumors to both innate and adaptive immune cytotoxicity.

Regulatory Role for NK Cells in a Mouse Model of Systemic Juvenile Idiopathic Arthritis.

Mice deficient in IFN-γ (IFN-γ knockout [KO] mice) develop a systemic inflammatory syndrome in response to CFA, in contrast to CFA-challenged wild-type (WT) mice who only develop a mild inflammation. Symptoms in CFA-challenged IFN-γ KO resemble systemic juvenile idiopathic arthritis (sJIA), a childhood immune disorder of unknown cause. Dysregulation of innate immune cells is considered to be important in the disease pathogenesis. In this study, we used this murine model to investigate the role of NK cells in the pathogenesis of sJIA. NK cells of CFA-challenged IFN-γ KO mice displayed an aberrant balance of activating and inhibitory NK cell receptors, lower expression of cytotoxic proteins, and a defective NK cell cytotoxicity. Depletion of NK cells (via anti-IL-2Rβ and anti-Asialo-GM1 Abs) or blockade of the NK cell activating receptor NKG2D in CFA-challenged WT mice resulted in increased severity of systemic inflammation and appearance of sJIA-like symptoms. NK cells of CFA-challenged IFN-γ KO mice and from anti-NKG2D-treated mice showed defective degranulation capacities toward autologous activated immune cells, predominantly monocytes. This is in line with the increased numbers of activated inflammatory monocytes in these mice which was particularly reflected in the expression of CCR2, a chemokine receptor, and in the expression of Rae-1, a ligand for NKG2D. In conclusion, NK cells are defective in a mouse model of sJIA and impede disease development in CFA-challenged WT mice. Our findings point toward a regulatory role for NK cells in CFA-induced systemic inflammation via a NKG2D-dependent control of activated immune cells.

Deletion of the activating NK cell receptor NKG2D accelerates rejection of cardiac allografts.

It has already been shown that neutralization of the activating NK cell receptor NKG2D in combination with co-stimulation blockade prolongs graft survival of vascularized transplants. In order to clarify the underlying cellular mechanisms, we transplanted complete MHC-disparate BALB/c-derived cardiac grafts into C57BL/6 wildtypes or mice deficient for NKG2D (Klrk1-/- ). Although median survival was 8 days for both recipient groups, we detected already at day 5 posttransplantation significantly greater intragraft frequencies of NKp46+ NK cells in Klrk1-/- recipients than in wildtypes. This was followed by a significantly greater infiltration of CD4+ , but a lesser infiltration of CD8+ T cell frequencies. Contrary to published observations, co-stimulation blockade with CTLA4-Ig resulted in a significant acceleration of cardiac rejection by Klrk1-/- recipients, and this result was confirmed by applying a neutralizing antibody against NKG2D to wildtypes. In both experimental setups, grafts derived from Klrk1-/- recipients were characterized by significantly higher levels of interferon-γ mRNA, and both CD4+ and CD8+ T cells displayed a greater capacity for degranulation and interferon-γ production. In summary, our results clearly illustrate that NKG2D expression in the recipient is important for cardiac allograft survival, thus supporting the hypothesis that impairment of NK cells prevents the establishment of graft acceptance.

Abstract 2012: UVB-induced ULBP1 upregulation in melanocytes depends on HMGB1-mediated activation of NF-κB and IRF3

Abstract Anti-tumor immune surveillance mediated by innate immunity cells such as NK cells plays a critical role in eliminating “damaged” cells at precancerous stage and preventing cancer progression. As a key epidemiological factor associated with melanoma, solar UV radiation also elicit immunosurveillance by upregulating ligands for NK cell activating receptor NKG2D. Nevertheless, how UVR upregulates NKG2DL in melanocytes is not completely understood. We found UVB exposure induced secretion of damage-associated molecular patterns molecule HMGB1 from skin cells. HMGB1 activates transcription factors NF-κB and IRF3 in melanocytes which synergistically enhances NKG2D ligand ULBP1 transcription. Moreover, RAGE is essential for HMGB1-induced activation of NF-κB and IRF3, which serves as the HMGB1 receptor and mediates activation of TBK1. Consistently, HMGB1 deficient melanoma cells are less susceptible to NK cells mediated cytotoxicity. Our study provides a mechanistic link between environmental UV radiation and antitumor immunosurveillance induced in melanocytes, which may play a critical role in the early stages of melanomagenesis. Citation Format: Zhaohui Wu, Wei Wang. UVB-induced ULBP1 upregulation in melanocytes depends on HMGB1-mediated activation of NF-κB and IRF3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2012. doi:10.1158/1538-7445.AM2017-2012

Modulation of signaling preference of NK cells by different forms of NKG2D ligands and its implications

Abstract The significance of ligand-induced activation of NK cell activating receptor NKG2D has been well established in controlling tumor growth in various experimental animal models. Amongst different types of NKG2D ligands, MHC I chain related molecule MICA/B is expressed most prevalently in various human cancers. In particular, proteolytically shed form of MICA/B (sMIC) has been shown to suppress the immune system and found to correlate with advanced disease stages in cancer patients. Previous studies in our lab using two humanized bi-transgenic mice, one expressing native ligand (TRAMP/MICB) and the other expressing the shedding-resistant mutant (TRAMP/MICB.A2) revealed opposite roles of these ligands in regulating tumor immunity. MICB expressing mice exhibited increased tumor progression, whereas MICB.A2 expressing mice had tumor free survival. These findings raised the intriguing question of why do these structurally similar forms of MIC have vastly different effects on tumor immunity. To address this question, we investigated the signaling events and functional outcomes in NK cells upon stimulation by the two forms of ligands. In vitro co-culture studies of NK cells with tumor cell lines expressing sMICB and MICB.A2 revealed elevated pro-inflammatory and immunosuppressive cytokine production by NK cells upon stimulation with sMICB. In contrast, NK cells stimulated with MICB.A2 displayed enhanced expression of cytotoxicity mediators and signaling molecules of cytotoxicity pathway. This suggests that signaling through sMICB may polarize the NKG2D signaling pathways with preferential activation of inflammatory cytokine pathways. Our data has uncovered a new potential mechanism whereby sMIC promotes tumor progression.

Atorvastatin-Induced Inhibition of Human Melanoma In Vivo Development

Statins, 3-hydroxy 3-methylglutaryl CoA (HMG-CoA) reductase inhibitors, are pleiotropic pharmacological inhibitors, which block the mevalonate synthesis pathway. They are widely used as hypocholesterolemic agents and have shown protective effects against cancers. Our previous data showed that statin treatment induced MHC class I chain-related protein A (MICA) membrane overexpression in human melanoma cells, which increased their sensitivity to NK cell cytotoxicity and thus the inhibition of tumor development. MICA is a ligand of the NK cell activating receptor NKG2D. This receptor is essential for NK cell control of tumor development and it has the unique property of being able to recognize tumor cells of both murine and human origin. Here, using atorvastatin and the WM-266-4 melanoma cell line, we first confirmed that statin treatment enhances MICA membrane expression and decreases local tumor growth and pulmonary metastasis implantation in vivo. Furthermore our new experiments showed that atorvastatin intraperitoneal repeated injections induced a reduction of tumor growth following subcutaneous implantation of untreated WM 266-4 cells into NMRI nude mice and favored the innate anti-melanoma immune response by increasing splenic NK cell concentration and activation. This report confirms that statins could become effective pharmacological agents for melanoma immunotherapy.

Generation of Ips Cell-Derived Hematopoietic Progenitor Cells from Patients with Acquired Aplastic Anemia Harboring Copy Number Neutral Loss of Heterozygosity of the Short Arm of Chromosome 6

Aplastic anemia (AA) is a syndrome of bone marrow failure characterized by peripheral pancytopenia and marrow hypoplasia. Because of the low number of hematopoietic stem/progenitor cells (HSPCs) in the bone marrow, it has been intrinsically difficult to study AA. Although autoimmunity to HSPCs is considered a key factor responsible for the pathogenesis of this disorder, little is known about the molecular basis of this autoimmunity. We have previously reported that leukocytes lacking HLA class I alleles are frequently detectable in patients with AA and are derived from HSPCs that undergo copy number neutral loss of heterozygosity of the short arm of chromosome 6 (6pLOH), and thereby escape the cytotoxic T-cell (CTL) attack against HSPCs (Katagiri et al, Blood 2011). Studying HSPCs derived from AA patients with 6pLOH(+) and their 6pLOH(-) counterparts should therefore be useful for identifying specific antigens that are targeted by CTLs in AA. In this study we generated human induced pluripotent stem cells (iPSCs) from monocytes derived from four AA patients with 6pLOH. Our generated iPSCs had normal karyotypes and were positive for human pluripotent stem cell markers such as Oct4 and SSEA4. The proportion of 6pLOH(+) iPSC clones generated from each patient was similar to the proportion 6pLOH(+) cells in the parental monocytes (50%, 100%, 100% and 100%, respectively). Unlike to their parental monocytes and consistent with previous reports, iPSCs poorly expressed class I and class II HLAs. Using an in vitro differentiation system with various hematopoietic cytokines and growth factors, iPSCs were successfully differentiated into CD34+ hematopoietic progenitor cells (iPSC-HPCs). Phenotypic studies revealed that on day 21 of the differentiation process, HPCs expressed CD34 (44.0%), the erythroid cell marker CD235a (10.5%), and CD45 (73.3%) but did not express the lineage-committed marker CD33or CD38, which is a marker expressed by a variety of mature hematopoietic cell types (Figure 1). As expected, both HLA-A alleles were highly expressed by in vitro differentiated HPCs derived from 6pLOH(-) wild type iPSC clones while the one HLA-A allele that was missing on the parental monocytes (HLA-A24) was undetectable in HPCs derived from 6pLOH(+) iPSC clones. Similarly, iPSC-HPCs did not express MHC class I-related chain (MIC)-A/B, the ligands for the NK cell activating receptor NKG2D. To further determine the hematopoietic potential of the iPSC-HPCs, they were cultured in the methylcellulose medium containing various colony stimulating factors. iPSC-HPCs were able to generate various types of colonies including CFU-GEMM (granulocyte, erythrocyte, macrophage, and megakaryocyte) and BFU-E at the plating efficiency of approximately 50%. Our study demonstrated, for the first time, that functional HPCs that lack particular HLA alleles due to 6pLOH can be successfully generated in vitro. The large number of HSCs generated from patients' derived iPSCs may be an excellent tool for searching antigens targeted by CTLs and investigating the pathogenesis of AA and thus developing novel therapeutic approaches. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Varicella-Zoster Virus and Herpes Simplex Virus 1 Differentially Modulate NKG2D Ligand Expression during Productive Infection

Natural killer (NK) cell-deficient patients are particularly susceptible to severe infection with herpesviruses, especially varicella-zoster virus (VZV) and herpes simplex virus 1 (HSV-1). The critical role that NK cells play in controlling these infections denotes an intricate struggle for dominance between virus and NK cell antiviral immunity; however, research in this area has remained surprisingly limited. Our study addressed this absence of knowledge and found that infection with VZV was not associated with enhanced NK cell activation, suggesting that the virus uses specific mechanisms to limit NK cell activity. Analysis of viral regulation of ligands for NKG2D, a potent activating receptor ubiquitously expressed on NK cells, revealed that VZV differentially modulates expression of the NKG2D ligands MICA, ULBP2, and ULBP3 by upregulating MICA expression while reducing ULBP2 and ULBP3 expression on the surface of infected cells. Despite being closely related to VZV, infection with HSV-1 produced a remarkably different effect on NKG2D ligand expression. A significant decrease in MICA, ULBP2, and ULBP3 was observed with HSV-1 infection at a total cellular protein level, as well as on the cell surface. We also demonstrate that HSV-1 differentially regulates expression of an additional NKG2D ligand, ULBP1, by reducing cell surface expression while total protein levels are unchanged. Our findings illustrate both a striking point of difference between two closely related alphaherpesviruses, as well as suggest a powerful capacity for VZV and HSV-1 to evade antiviral NK cell activity through novel modulation of NKG2D ligand expression. Patients with deficiencies in NK cell function experience an extreme susceptibility to infection with herpesviruses, in particular, VZV and HSV-1. Despite this striking correlation, research into understanding how these two alphaherpesviruses interact with NK cells is surprisingly limited. Through examination of viral regulation of ligands to the activating NK cell receptor NKG2D, we reveal patterns of modulation by VZV, which were unexpectedly varied in response to regulation by HSV-1 infection. Our study begins to unravel the undoubtedly complex interactions that occur between NK cells and alphaherpesvirus infection by providing novel insights into how VZV and HSV-1 manipulate NKG2D ligand expression to modulate NK cell activity, while also illuminating a distinct variation between two closely related alphaherpesviruses.

CMV-Specific Cytokine-Induced Killer Cells Comprise Concomitant Cytotoxicity Against Leukemia and Cytomegalovirus

IntroductionInfection is one of the main causes of mortality and morbidity after allogeneic stem cell transplantation, especially in patients who received T cell depleted haploidentical stem cells. Reactivation or de novo infection of cytomegalovirus (CMV) is amongst the most frequent complications and occur due to a lack of virus-specific T cells post-transplant. Pre-emptive immunotherapy may support both reconstitution of viral specific responses on one hand and may prevent impending leukemic relapse on the other hand. Therefore we established a protocol to generate CMV-specific cytokine-induced killer cells (CIKpp65) with dual cytolytic function against CMV and AML.ProtocolCIK cells were generated in vitro from peripheral blood mononuclear cells (PBMC) of CMV-seropositive healthy donors using IFN-γ, activating monoclonal anti-CD3 antibody (MAb), interleukin (IL)-2 and IL-15. An additional single stimulation with human CMVpp65 protein was adequate to increase the amount of cytotoxic CMV-specificcells within CIK cells up to 23%. In total the CMVpp65 stimulation resulted in up to 11.0-fold increased frequency of CMV-dextramer+CD8+cells after 15 days of expansion (n=12).ResultsCytotoxicityNext we investigated cell-mediated cytotoxicity against leukemic cell lines THP-1 and K562, pp65 loaded cell line T2 and CMV-infected primary fibroblasts. CIK cell cytotoxicity is described as mediated by activating NK-cell receptor NKG2D. This receptor was blocked in order to determine the specific MHC-mediated cytotoxicity in experiments targeting pp65 loaded cells. The lysis of pp65 loaded cells by CIKpp65 cells was significant higher as compared to conventional CIK cells (effector to target cell ratio of 5:1, 39.9±21.6% to 13.6±10.6%, P<0.01). CIKpp65 cells also induced high cytotoxicity in infected fibroblasts (up to 55%, 10:1 E:T ratio). The anti-leukemic effect was retained in CIKpp65 cells. CIKpp65 cells revealed a mean cytotoxicity of 71.5%, 60.7% and 37.8% against THP-1 and 55.0%, 50.0%, 20.5% against K562 in 40:1, 20:1 and 5:1 E:T ratio, respectively. In contrast, the reactivity against allogeneic PBMC remained low (18% lysis, 40:1 E:T ratio) and allogeneic mock-infected fibroblasts were not lysed at all. This clearly indicates towards the low alloreactive potential of CIKpp65 cells.PhenotypeFurthermore we characterized subpopulation and memory phenotype of CIKpp65 cells in detailed flow cytometric analyses and examined the cytokine secretion pattern by cytometric bead array. After expansion the population mainly consisted of a CD3+CD56- T cell (77.6±4.5%) and CD3+CD56+ T-NK cell phenotype (20.0±12.6%). The T-NK cells additionally co-expressed high amounts of CD8 cytotoxic antigen (63.8±16.8%). Interestingly, the T-NK cell compartment contained higher amounts CMV-specific CD8+ cells (mean 5.5%) than the T cell compartment (mean 1.3%). Expression of activating NKG2D and CD25 receptor was strongly positive in both cell fractions. Remarkably, almost 30% of T-NK cells expressed γδ+ T cell receptor, whereas T cells only expressed 4.5% of this receptor type. The cytotoxic T cells within the CIKpp65 cells consisted of a mixed naïve (CD45RA+CD62L+), central memory (CD45RO+CD62L+) and effector memory (CD45RO+CD62L-) phenotype, the cytotoxic T-NK cells mainly of effector memory and EMRA (CD45RA+CD62L-) phenotype. Cytokine secretion (granzyme B, IFN-γ, MIP-1α, TNF-α, Fas-L, IP-10, IL-10, IL-6 and IL-4) were measured during the expansion period and cytotoxic assays and resulting data confirmed the cytotoxic nature of the cells and indicated towards a mainly TH1 cell type character.ConclusionIn conclusion CIKpp65 cells can easily be generated from donor PBMC and might represent advantage to conventional CIK cells. Our pre-clinical data demonstrate the concomitant cytotoxicity of generated cells against leukemia cells and CMV, as well as low alloreactivity and limited risk to induce GvHD. Therefore CIKpp65 cells may represent an effective tool for pre-emptive immunotherapy in patients which have both an apparent risk of CMV reactivation and leukemic relapse after allogeneic stem cell transplantation. DisclosuresNo relevant conflicts of interest to declare.

MICA/B expression is inhibited by unfolded protein response and associated with poor prognosis in human hepatocellular carcinoma.

BackgroundMICA/B are major ligands for NK cell activating receptor NKG2D and previous studies showed that the serum level of soluble MICA (sMICA) is an independent prognostic factor for advanced human hepatocellular carcinoma. However, the correlation between cellular MICA/B expression pattern and human hepatocellular carcinoma progression has not been well explored. The unfolded protein response is one of the main causes of resistance to chemotherapy and radiotherapy in tumor cells. However, whether the UPR in HCC could regulate the expression levels of MICA/B and affect the sensitivity of HCC cells to NK cell cytolysis has not been established yet.MethodsMICA/B expression pattern was evaluated by immunohistochemistry and Kaplan-Meier survival analysis was done to explore the relationship between MICA/B expression level and patient survival. The protein and mRNA expression levels of MICA/B in SMMC7721 and HepG2 cells treated by tunicamycin were evaluated by flow cytometry, Western Blot and RT-PCR. The cytotoxicity analysis was performed with the CytoTox 96 Non-Radioactive LDH Cytotoxicity Assay.ResultsMICA/B was highly expressed in human hepatocellular carcinoma and the expression level was significantly and negatively associated with tumor-node metastasis (TNM) stages. Patients with low level of MICA/B expression showed a trend of shorter survival time. The unfolded protein response (UPR) downregulated the expression of MICA/B. This decreased protein expression occurred via post-transcriptional regulation and was associated with proteasomal degradation. Moreover, decreased expression level of MICA/B led to the attenuated sensitivity of human HCC to NK cell cytotoxicity.ConclusionThese new findings of the connection of MICA/B, UPR and NK cells may represent a new concrete theory of NK cell regulation in HCC, and suggest that targeting this novel NK cell-associated immune evasion pathway may be meaningful in treating patients with HCC.Electronic supplementary materialThe online version of this article (doi:10.1186/s13046-014-0076-7) contains supplementary material, which is available to authorized users.

Novel Candidate Markers Characterizing Cellular Senescence in Aged Zero Hour Kidney Biopsies Predict Post Transplant Outcome.

Advanced donor age adversely affects allograft outcome following renal transplantation.Candidate genes involved in cellcycle regulation and telomere shortening have been already described as markers for cellular senescence.There is still a lack of biomarkers for defining older and marginal organs in order to adopt immunosuppression for improved long-term outcome.To characterize senescence in the donor organ, we first studied gene expression for selected candidate markers(CM) in a small sample cohort of 57 zero hour kidney biopsies derived from deceased donors.Among them 26 biopsies were derived from donors>55 yrs(mean66.5±7.4) and 31 specimens were derived from donors<55 yrs(mean 41.35±8.4).Compared with younger donors,elderly donors revealed a significant de novo mRNA expression of CM including immunoproteasome subunits PSMB8,9,10;(p<0.001 respectively), MHC classII transcripts including HLA-DRB(p<0.01)or transcripts of the receptor NKG2D(p=0.0036).Next, we confirmed gene expression of CM in an independent patient cohort consisting of 139 biopsy samples.Based on sample size,3 groups were defined according to donor age:0-30yrs(group I,21±4.9yrs,n=30),31-54yrs(group II, 46.5±6.6yrs,n=50)and>55 yrs(group III,64.07±7yrs,n=59).Whereas no differences were observed between group I and group II, aged kidneys(group III) revealed a significant gene expression of PSMB9(p=0.0405) and PSMB10(p=0.0223) compared with middle aged kidneys(group II).In addition,HLA-DRB(p=0.0215) and PSMB9(p=0.0129) were significantly induced in group III in comparison with group I.Strikingly,transcripts of the activating NK cell receptor NKG2D revealed the highest gene induction in group III versus group II and group I(p<0.001,respectively) indicating enhanced infiltration of NKG2D+ CD8+ T cells or NK cells in elderly kidneys. Linear restriction analysis revealed a strong correlation especially for pre-transplant NKG2D mRNA expression with serum creatinine levels at hospital discharge(p=0.0003), at 3months(p=0.004) and at 6months post transplantation(p=0.0031).Our results reveal novel candidate markers in aged renal allografts providing help in the assessment of organ quality and implicating the potential of pretreatment strategies.

MICA/B expression is inhibited by unfolded protein response and associated with poor prognosis in human hepatocellular carcinoma

MICA/B are major ligands for NK cell activating receptor NKG2D and previous studies showed that the serum level of soluble MICA (sMICA) is an independent prognostic factor for advanced human hepatocellular carcinoma. However, the correlation between cellular MICA/B expression pattern and human hepatocellular carcinoma progression has not been well explored. The unfolded protein response is one of the main causes of resistance to chemotherapy and radiotherapy in tumor cells. However, whether the UPR in HCC could regulate the expression levels of MICA/B and affect the sensitivity of HCC cells to NK cell cytolysis has not been established yet. MICA/B expression pattern was evaluated by immunohistochemistry and Kaplan-Meier survival analysis was done to explore the relationship between MICA/B expression level and patient survival. The protein and mRNA expression levels of MICA/B in SMMC7721 and HepG2 cells treated by tunicamycin were evaluated by flow cytometry, Western Blot and RT-PCR. The cytotoxicity analysis was performed with the CytoTox 96 Non-Radioactive LDH Cytotoxicity Assay. MICA/B was highly expressed in human hepatocellular carcinoma and the expression level was significantly and negatively associated with tumor-node metastasis (TNM) stages. Patients with low level of MICA/B expression showed a trend of shorter survival time. The unfolded protein response (UPR) downregulated the expression of MICA/B. This decreased protein expression occurred via post-transcriptional regulation and was associated with proteasomal degradation. Moreover, decreased expression level of MICA/B led to the attenuated sensitivity of human HCC to NK cell cytotoxicity. These new findings of the connection of MICA/B, UPR and NK cells may represent a new concrete theory of NK cell regulation in HCC, and suggest that targeting this novel NK cell-associated immune evasion pathway may be meaningful in treating patients with HCC.

Natural killer cell NKG2D and granzyme B are critical for allergic pulmonary inflammation⋆

BackgroundThe diverse roles of innate immune cells in the pathogenesis of asthma remain to be fully defined. Natural killer (NK) cells are innate lymphocytes that can regulate adaptive immune responses. NK cells are activated in asthma; however, their role in allergic airway inflammation is not fully understood.ObjectiveWe investigated the importance of NK cells in house dust mite (HDM)-triggered allergic pulmonary inflammation. Specifically, we aimed to determine the role of the major NK-cell activating receptor NKG2D and NK-cell effector functions mediated by granzyme B.MethodsAllergic airway inflammation was induced in the airways of mice by repeated intranasal HDM extract administration and responses in wild-type and NKG2D-deficient mice were compared. Adoptive transfer studies were used to identify the cells and mechanisms involved.ResultsMice that lacked NKG2D were resistant to the induction of allergic inflammation and showed little pulmonary eosinophilia, few airway TH2 cells, and no rise in serum IgE after multiple HDM-allergen exposures. However, NKG2D was not required for pulmonary inflammation after a single inoculation of allergen. NKG2D-deficient mice showed no alteration in responses to respiratory virus infection. Transfer of wild-type NK cells (but not CD3+ cells) into NKG2D-deficient mice restored allergic inflammatory responses only if the NK cells expressed granzyme B.ConclusionsThese studies established a pivotal role for NK-cell NKG2D and granzyme B in the pathogenesis of HDM-induced allergic lung disease, and identified novel therapeutic targets for the prevention and treatment of asthma.

Ras Activation Induces Expression of Raet1 Family NK Receptor Ligands

NK cells play a crucial role in innate immunity against tumors. In many human tumors, Ras is chronically active, and tumor cells frequently express ligands for the activating NK cell receptor NKG2D. In this study, we report that Ras activation upregulates the expression of Raet1 protein family members Rae1α and Rae1β in mouse and ULBP1-3 in human cells. In addition, Ras also induced MHC class I chain-related protein expression in some human cell lines. Overexpression of the constitutively active H-RasV12 mutant was sufficient to induce NKG2D ligand expression. H-RasV12-induced NKG2D ligand upregulation depended on Raf, MAPK/MEK, and PI3K, but not ATM or ATR, two PI3K-like kinases previously shown to induce NKG2D ligand expression. Analysis of the 5' untranslated regions of Raet1 family members suggested the presence of features known to impair translation initiation. Overexpression of the rate-limiting translation initiation factor eIF4E induced Rae1 and ULBP1 expression in a Ras- and PI3K-dependent manner. Upregulation of NKG2D ligands by H-RasV12 increased sensitivity of cells to NK cell-mediated cytotoxicity. In summary, our data suggest that chronic Ras activation is linked to innate immune responses, which may contribute to immune surveillance of H-Ras transformed cells.

A dual function of NKG2D ligands in NK‐cell activation

NK-cell killing requires both the expression of activating receptor ligands and low MHC class I expression by target cells. Here we demonstrate that the expression of any of the murine ligands for the NK-cell activating receptor NKG2D results in a concomitant reduction in MHC class I expression. We show this both in tumor cell lines and in vivo. NK-cell lysis is enhanced by the decrease in MHC class I expression, suggesting the change is biologically relevant. These results demonstrate that NKG2D ligand expression on target cells not only allows for activating receptor recognition, but also actively reduces expression of the inhibitory ligand, MHC class I, leading to enhanced recognition and killing by NK cells.

Pharmacological activation of p53 triggers anticancer innate immune response through induction of ULBP2

Escape of tumor cells from cell-intrinsic barrier mediated by tumor suppressors and cell-extrinsic barrier mediated by the immune system is crucial for tumorigenesis. Growing evidence suggests that reactivation of tumor suppressor function or restoration of anticancer immunity is promising strategy for anticancer therapy due to their high potential to combat cancer. p53, a key tumor suppressor, represses tumorigenesis by eliciting growth arrest, apoptosis or senescence in cancer cells. Here, we unravel that, apart from these cell-autonomous effects, p53 activates the innate immune response against cancer cells. Our results show that pharmacological reactivation of p53 can stimulate the expression of ULPB2, a ligand for NK cell activating receptor NKG2D in human tumor cells of different origin, which enhance the susceptibility of tumor cells to NK cell-mediated killing. The molecular mechanism controlling ULPB2 expression by p53 is neither ATM/ATR- nor caspase-dependent. Using several approaches, we identified p53 as a direct transcriptional regulator of ULBP2 and found a p53 response element within ULBP2 gene, which confers the p53 regulation. Furthermore, we demonstrated that demethylation of p53-binding region within ULBP2 gene was required for p53-dependent induction of ULPB2, which can be achieved via repression of DNA methyltransferases (DNMTs) by p53. This molecular evidence for the direct control of immunosurveillance by p53 links tumor suppressor activation to innate immune stimuli and provides a possibility to integrate cell-extrinsic and -intrinsic defenses against tumorigenesis by pharmacological activation of p53, which may increase the probability to achieve a durable therapeutic success.