Inhibitory NK Cell Research Articles

Increased lipid metabolism impairs NK cell function and mediates adaptation to the lymphoma environment

AbstractNatural killer (NK) cells play critical roles in protection against hematological malignancies but can acquire a dysfunctional state, which limits antitumor immunity. However, the underlying reasons for this impaired NK cell function remain to be uncovered. We found that NK cells in aggressive B-cell lymphoma underwent substantial transcriptional reprogramming associated with increased lipid metabolism, including elevated expression of the transcriptional regulator peroxisome activator receptor-γ (PPAR-γ). Exposure to fatty acids in the lymphoma environment potently suppressed NK cell effector response and cellular metabolism. NK cells from both diffuse large B-cell lymphoma patients and Eµ-myc B-cell lymphoma-bearing mice displayed reduced interferon-γ (IFN-γ) production. Activation of PPAR-γ partially restored mitochondrial membrane potential and IFN-γ production. Overall, our data indicate that increased lipid metabolism, while impairing their function, is a functional adaptation of NK cells to the fatty-acid rich lymphoma environment.

IFN-γ–mediated negative feedback regulation of NKT-cell function by CD94/NKG2

Activation of invariant natural killer T (iNKT) cells with CD1d-restricted T-cell receptor (TCR) ligands is a powerful means to modulate various immune responses. However, the iNKT-cell response is of limited duration and iNKT cells appear refractory to secondary stimulation. Here we show that the CD94/NKG2A inhibitory receptor plays a critical role in down-regulating iNKT-cell responses. Both TCR and NK-cell receptors expressed by iNKT cells were rapidly down-modulated by priming with alpha-galactosylceramide (alpha-GalCer) or its analog OCH [(2S,3S,4R)-1-O-(alpha-D-galactopyranosyl)-N-tetracosanoyl-2-amino-1,3,4-nonanetriol)]. TCR and CD28 were re-expressed more rapidly than the inhibitory NK-cell receptors CD94/NKG2A and Ly49, temporally rendering the primed iNKT cells hyperreactive to ligand restimulation. Of interest, alpha-GalCer was inferior to OCH in priming iNKT cells for subsequent restimulation because alpha-GalCer-induced interferon gamma (IFN-gamma) up-regulated Qa-1b expression and Qa-1b in turn inhibited iNKT-cell activity via its interaction with the inhibitory CD94/NKG2A receptor. Blockade of the CD94/NKG2-Qa-1b interaction markedly augmented recall and primary responses of iNKT cells. This is the first report to show the critical role for NK-cell receptors in controlling iNKT-cell responses and provides a novel strategy to augment the therapeutic effect of iNKT cells by priming with OCH or blocking of the CD94/NKG2A inhibitory pathway in clinical applications.

Functionally Relevant Differences in Plasma Fatty Acid Composition and Expression of Cytotoxic and Inhibitory NK Cell Receptors between Healthy Young and Healthy Elder Adults.

(1) Background: In the healthy ageing, NK cell number is not modified; however, their spontaneous cytotoxicity decreases. We postulated that the age-dependent decline in metabolic activities might be responsible for this effect. (2) Methods: The fatty acid profile of 30 healthy young males (23 ± 4 years old, BMI 22.1 ± 1.3) and 30 older males (63 ± 5 years old, BMI 22.9 ± 2.5) donors were evaluated along with the expression of killing (KR) and inhibitory NK receptors (KIR) at basal level and after cultivation with fatty acids for 24 h. (3) Results: Significantly higher levels of oleic (p < 0.01), arachidonic (p < 0.001), lignoceric (p < 0.001), and nervonic acids (p < 0.0001) and significantly lower levels of docosapentaenoic and docosahexaenoic acids (p < 0.01) were found in elders as compared to young adults. At basal levels, significant (p < 0.005) differences in KR and KIR expression were encountered; 12/16 antigens. Treatment of cells with saturated fatty acids or arachidonic acid (AA) significantly enhanced KR expressions (p < 0.001). AA treatment decreased inhibitory KIR expression while docosahexaenoic, and eicosapentaenoic acid increased them. (4) Conclusions: Changes in fatty acids blood levels, and KR and KIR expression in NK cell, are age-dependent. Supplementation of NK cells with eicosapentaenoic or docosahexaenoic acid enhanced inhibitory KIR receptors’ expression which may improve their cell function.

CAR19 iPSC-Derived NK Cells Utilize the Innate Functional Potential Mediated through NKG2A-Driven Education and Override the HLA-E Check Point to Effectively Target B Cell Lymphoma

Induced pluripotent stem cell (iPSC)-derived natural killer (iNK) cells offer a promising platform for off-the-shelf immunotherapy against cancer. A unique benefit of iPSC-derived immune effector cells is the possibility to perform multiple precision editing steps at the single cell level to achieve a homogenous effector cell population tailored to target a desired cancer type and equipped with selected functional properties. These functional edits are superimposed on the innate reactivity of NK cells to stress ligands and MHC downregulation (missing self). The ability of NK cells to sense missing self is based on a functional calibration to self MHC during a process termed NK cell education, the latter being critically dependent on signaling through inhibitory receptors, including CD94/NKG2A and killer cell immunoglobulin-like receptors (KIR). Whereas the process of NK cell differentiation into mature effector cells from iPSCs has been well characterized, the role of natural variation in inhibitory receptor expression and NK cell education remains poorly defined in iNK cells. We used mass cytometry to map the receptor repertoire in series of iNK cell lines and genetic edits thereof during differentiation and in vitro expansion (Figure 1A and B). Similar to peripheral blood NK cells, the receptor repertoire was diversified but genetically hardwired showing consistent patterns within each iNK cell line but with slight variation between genetically distinct lines. NKG2A was the dominantly expressed inhibitory receptor ranging from 13% to 87% with the highest expression in multi-edited iNK cell lines engineered to express a chimeric antigen receptor against CD19, a high affinity, non-cleavable FcγRIIIa receptor (CD16) and a recombinant IL15 signaling complex (CAR19-iNK cells). KIR expression was generally low in all tested iNK cell lines but increased gradually during culture and was further increased by genetic silencing of NKG2A receptors. Interestingly, silencing of NKG2A lead to increased levels of the activating receptor NKG2C. We monitored degranulation by iNK cell variants against K562 engineered to express varying levels of HLA-E as well as CD19+ Nalm-6 cells. Genetic silencing of ß2microglobulin (ß2m), associated with reduced levels of HLA-class I and HLA-E, led to dampened global functional responses in iNK cells, suggesting a positive impact of education during iNK cell differentiation and expansion (Figure 1C). Subset stratification revealed that NKG2A+ iNK cells showed superior functionality compared to NKG2A- iNK cells across all iNK cell lines tested, albeit less striking in CAR19-iNK cells that showed the highest overall natural cytotoxicity (Figure 1D). Knockdown of NKG2A led to a general reduction in functional capacity of NK92 cells (Figure 1E-F) and CAR19-iNK cells (Figure 1H), supporting a critical role for NKG2A-driven education in iNK cells. Given the superior functionality of NKG2A+ iNK cells, we next addressed whether this advantage was countered by expression of the check point ligand HLA-E during target cell interactions. Although we noted a slight inhibitory impact on natural cytotoxicity in NK cells isolated and expanded from peripheral blood (PB-NK) against K562 cells expressing physiological levels of HLA-E, this effect was completely overridden in iNK cells and did not interfere with NKG2A+ CAR-iNK cell recognition of HLA-E expressing CD19+ target cells (Figure 1G-H). Indeed, NKG2A+ CAR19-iNK showed superior degranulation against HLA-E expressing CD19+ Nalm-6 targets compared to CRISPR-edited NKG2A-/- CAR19-iNK cells (Figure 1I). Our results shed light on the regulatory gene circuits and cellular programs that determine functional potential in iPSC-derived NK cells products. Specifically, our results point to a crucial role for NKG2A-driven acquisition of a mature effector cell phenotype in combination with functional education through cognate ligands. Importantly, iNK cell education is operational during iNK cell differentiation and expansion without interfering with recognition of tumor targets expressing HLA-E. Figure 1 Disclosures Cichocki: Fate Therapeutics, Inc: Consultancy, Patents &amp; Royalties, Research Funding. Mahmood:Fate Therapeutics, Inc: Current Employment. Gaidarova:Fate Therapeutics, Inc: Current Employment. Bjordahl:Fate Therapeutics: Current Employment. Chu:Fate Therapeutics, Inc: Current Employment. Groff:Fate Therapeutics, Inc: Current Employment. Denholtz:Fate Therapeutics, Inc: Current Employment. Miller:Fate Therapeutics, Inc: Consultancy, Patents &amp; Royalties, Research Funding; Vycellix: Consultancy; Onkimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Nektar: Honoraria, Membership on an entity's Board of Directors or advisory committees; GT Biopharma: Consultancy, Patents &amp; Royalties, Research Funding. Lee:Fate Therapeutics, Inc.: Current Employment. Kaufman:Fate Therapeutics: Consultancy. Goodridge:Fate Therapeutics, Inc: Current Employment. Valamehr:Fate Therapeutics, Inc: Current Employment, Current equity holder in publicly-traded company. Malmberg:Fate Therapeutics: Consultancy, Patents &amp; Royalties; Vycellix: Membership on an entity's Board of Directors or advisory committees.

NK cell-derived exosomes improved lung injury in mouse model of Pseudomonas aeruginosa lung infection

BackgroundPseudomonas aeruginosa (PA) is one of the most common bacteria that causes lung infection in hospital. The aim of our study is to explore the role and action mechanism of NK cells in lung PA infection.MethodsIn this present study, 2.5 × 108 CFU/mouse PA was injected into murine trachea to make lung PA infection mouse model. Anti-asialo GM1 was used to inhibit NK cell. The percentage of NK cells was ensured by flow cytometry, and the M1- and M2-polarized macrophages were determined by flow cytometry, qRT-PCR, and ELISA assay. Besides, H&E staining was performed to ensure the pathological changes in lung tissues. Transmission electron microscopy and western blot were carried out to identify the exosome.ResultsHere, in the mouse model of PA lung infection, NK cell depletion caused M2 polarization of lung macrophage, and exacerbated PA-induced lung injury. Next, our data shown that M2 macrophage polarization was enhanced when the generation of NK cell-derived exosome was blocked in the co-culture system of NK cells and macrophages. Subsequently, we demonstrated that NK cells promoted M1 macrophage polarization both in PA-infected macrophage and the mouse model of PA lung infection, and attenuated lung injury through exosome.ConclusionOverall, our data proved that NK cell may improve PA-induced lung injury through promoting M1 lung macrophage polarization by secreting exosome. Our results provide a new idea for the treatment of PA lung infection.

Association between rs1049174 NKG2D gene polymorphism and idiopathic recurrent spontaneous abortion in Iranian women: a case-control study

Natural killer group 2, member D (NKG2D) is one of the best known activating receptors of NK cells, which recognises its ligand on altered or stressed cells and activates NK cells to kill them. In this study, the single nucleotide polymorphism of the NKG2D gene for rs1049174 mutation was compared in 140 women with recurrent spontaneous abortion (RSA) and 175 control women with at least one successful pregnancy and without any known pregnancy loss. The findings just revealed that GG genotype and G allele were significantly higher in the case group compared with the control group (p < .001). Our results regarding decreased risk of RSA in C allele (OR = 0.438; 95%CI = 0.310–0.619; p < .001), and GC genotype (OR = 0.492; 95%CI = 0.214–0.574; p < .001) compared with G allele and GG genotype respectively. This study demonstrated a significant association between NKG2D gene polymorphism (rs1049174 G/C) and the risk of RSA in Iranian women. Impact statement What is already known on this subject? According to previous investigations, maternal immune responses may affect the foetus, causing recurrent spontaneous abortion (RSA). The main cause of RSA has not yet been detected in nearly 50% of the cases. What do the results of this study add? The results showed that the frequency of G allele and C allele were significantly different in the case group and control group. What are the implications of these findings for clinical practice and/or further research? The results suggest a protective function of C allele because it significantly decreased the risk of RSA compared to G allele. It improves inhibition of NK cells and probably participates in maintaining pregnancy in fertile controls; whereas, G allele is related to a slight inhibition of NK cells, probably leading to increase effectiveness of NK activation and undesirable inflammation, which consequently causes foetal rejection.

Increased Expression of TIGIT/CD57 in Peripheral Blood/Bone Marrow NK Cells in Patients with Chronic Myeloid Leukemia.

The antitumor activity of NK cells in patients with chronic myeloid leukemia (CML) is inhibited by the leukemia microenvironment. Recent studies have identified that the expression of TIGIT, CD57, and KLRG1 is related to the function, maturation, and antitumor capabilities of NK cells. However, the characteristics of the expression of these genes in the peripheral blood (PB) and bone marrow (BM) from patients with CML remain unknown. In this study, we used multicolor flow cytometry to assay the quantity and phenotypic changes of NK cells in PB and BM from de novo CML (DN-CML) and CML patients acquiring molecular response (MR-CML). We found that the expression of TIGIT, which inhibits NK cell function, is increased on CD56+ and CD56dim NK cells in DN-CML PB compared with those in healthy individuals (HIs), and it is restored to normal in patients who achieve MR. We also found that the expression of CD57 on NK cells was approximately the same level in PB and BM from DN-CML patients, while decreased CD57 expression was found on CD56+ and CD56dim NK cells in HI BM compared with PB. Additionally, those two subsets were significantly increased in DN-CML BM compared to HI BM. The expression of CD57 correlates with replicative senescence and maturity for human NK cells; therefore, the increase in TIGIT on PB NK cells together with an increase in CD57 on BM NK cells may explain the subdued NK cell antileukemia capacity and proliferative ability in DN-CML patients. These results indicate that reversing the immune suppression of PB NK cells by blocking TIGIT while improving the proliferation of BM NK cells via targeting CD57 may be more effective in removing tumor cells.

NK cells in the tumor microenvironment and thioredoxin activity.

NK cells are responsible for defense against viral infections and cancer. Although activated NK cells are armed to combat tumors, the tumor microenvironment (TME) contains ROS, which suppress NK cell antitumor activity. In this issue of the JCI, Yang, Neo, and colleagues explored NK cell resistance to oxidative stress in vitro and in human non-small-cell lung cancer (NSCLC). High surface thiol density and elevated expression of the ROS scavenger thioredoxin (Trx1) protected NK cells from ROS. Trx1 and thiol levels were higher in IL-15- than in IL-2-primed NK cells. Tumor-infiltrating Trx1+ NK cells were present in patients with NSCLC with elevated ROS levels in the tumor. Smokers scored higher for the ROS signature, which predicted poor prognosis, compared with nonsmokers. This study explains how activated NK cells survive in the ROS-rich TME and suggests that smokers with lung cancer may benefit from therapies using IL-15-primed NK cells.

Inhibitory Receptors and Checkpoints in Human NK Cells, Implications for the Immunotherapy of Cancer.

The highly destructive mechanisms by which the immune system faces microbial infections is under the control of a series of inhibitory receptors. While most of these receptors prevent unwanted/excessive responses of individual effector cells, others play a more general role in immunity, acting as true inhibitory checkpoints controlling both innate and adaptive immunity. Regarding human NK cells, their function is finely regulated by HLA-class I-specific inhibitory receptors which allow discrimination between HLA-I+, healthy cells and tumor or virus-infected cells displaying loss or substantial alterations of HLA-I molecules, including allelic losses that are sensed by KIRs. A number of non-HLA-specific receptors have been identified which recognize cell surface or extracellular matrix ligands and may contribute to the physiologic control of immune responses and tolerance. Among these receptors, Siglec 7 (p75/AIRM-1), LAIR-1 and IRp60, recognize ligands including sialic acids, extracellular matrix/collagen or aminophospholipids, respectively. These ligands may be expressed at the surface of tumor cells, thus inhibiting NK cell function. Expression of the PD-1 checkpoint by NK cells requires particular cytokines (IL-15, IL-12, IL-18) together with cortisol, a combination that may occur in the microenvironment of different tumors. Blocking of single or combinations of inhibitory receptors unleashes NK cells and restore their anti-tumor activity, with obvious implications for tumor immunotherapy.

Natural killer cell impairment in ovarian clear cell carcinoma.

In the present study, we report the analysis of NK cells derived from patients suffering from a rare ovarian cancer histotype of clear cell carcinoma (OCCC) resistant to conventional chemotherapies. We analyzed the phenotype of NK cells derived from peripheral blood (PB) and peritoneal fluid (PF) and evaluated cytotoxic interactions between NK cells and autologous tumor cells (ATC) derived from patients. We provided evidence of impaired degranulation capacity of NK cells derived from patients' PF in the presence of ATC. Analyzing tumor cell ligands recognized by NK cell receptors, we found that ATC are characterized by an HLA class I+ phenotype (although the level of HLA-I expression varies among all patients) and by a heterogeneous expression of ligands for activating NK receptors (from normal to decreased expression of some markers). Furthermore, we observed a down-regulation of crucial NK cell activating receptors, primarily DNAX Accessory Molecule-1 (DNAM-1), on tumor-associated NK cells. Based on these results, we propose that this severe lysis defect may be due to both negative interactions between HLA-I-specific inhibitory NK cell receptors/HLA-I molecules and to defective interactions between activating NK receptors and cognate ligands. In conclusion, for the first time, the phenotypic and functional properties of tumor-associated NK cells and their ATC derived from PF of patients with advanced stage of OCCC were characterized. Taken together results indicate altered interactions between NK cells and ATC and shed light on the aggressive mechanisms of this cancer histotype. Further studies on this rare tumor will be helpful to improve and define more effective therapies.

Abstract 3333: EMT-6 tumor conditioned Breg cells inhibit NK cell proliferation and cytotoxic activity

Abstract Purpose: Breg (B regulatory) cells have been implicated in suppression of anti-tumor response in murine and human solid tumors. Prior studies in our laboratory demonstrated that murine EMT-6 breast carcinoma is rejected in B cell deficient mice (BCDM), but not in wild type (WT) mice, due to an enhanced immune response. Tumor infiltrating B cells (TIL-B), and normal splenic B cells co-cultured with EMT-6 (EMT6-B), express LAP/TGF-β, PD-L1, and suppress CD8+ and NK cell proliferation in vitro. Increased CD8+ and NK cell infiltration into the tumor bed is seen in BCDM. BCDM tumor rejection is abrogated by NK depletion. We studied EMT6-B effects on NK cell phenotype, proliferation and cytokine expression in vitro and in vivo. Experimental design: Normal splenic B cells were co-cultured with mitomycin C treated EMT-6, and Breg phenotype, and effects on NK cell phenotype and proliferation and cytokine function were studied in vitro and in vivo. Results: EMT6-B but not WT splenic B cells inhibited CFSE labeled CD49b+ NK cell proliferation in response to IL-15 in dose dependent fashion. EMT-6-B suppressed expression of CD226 and NKG2D activating receptors on NK cells, and increased expression of PD-1 and PD-L1 respectively. EMT6-B suppressed the induction of IFNγ+/CD49b+ NK cells following PMA/ION stimulation as assayed by intracellular flow cytometry (10%±1.2 to 2%±0.5) and also suppressed IL-2 induced induction of IFNγ+/CD49b+ NK cells (70%±5 to 20%±7.8). EMT-6 and CT26 colon carcinoma conditioned B cells, but not C166 endothelial cell conditioned B cells suppressed NK degranulation (IFNγ+/CD107a+ NK cells). EMT6-B inhibited YAC-1 cell induced NK cell degranulation, and killing of YAC-1 targets, more effectively than naïve B cells (40%±6.2 to 18%±5.1) (P=0.05). NK suppression was inhibited by anti-PD-L1, and anti-TGF-β antibody. EMT6-B expressed increased FasL compared to splenic B cells, and induced NK apoptosis as measured by 7AAD/Annexin-V staining. Blocking antibody to FasL decreased NK apoptosis, and restored NK cell proliferation. Infiltrating NK cells in the EMT6 tumor bed demonstrated increased PD-1 compared to splenic and TDLN NK cells, and higher levels of IFN-γ, CD107a, and Granzyme B in BCDM vs. WT mice. EMT6 expressed high levels of CD155 NK inhibitory ligand compared to C166 endothelial cells. The EMT-6 tumor bed contained higher levels of CD19+CD155+ B cells (22% / tumor bed vs 6% / TDLN, vs 9%/ spleen). BCDM expressed higher levels of CD226+/Ki67+ NK cells in spleen compared to WT splenic NK cells. Antibodies to Fas-L, TGF-beta, and PD-L1 partially restored anti-tumor response in WT mice and decreased tumor growth. Conclusions: EMT-6 TIL-B or normal B cells conditioned by EMT-6 coculture acquire an NK suppressive phenotype which inhibits NK cell activation, proliferation, degranulation and cytotoxic function. Targeting of Breg-NK interactions may improve anti-tumor immune response. Citation Format: Yu Zhang, Muhammad Husnain, Zhifen Luo, Mahmood Al Bayati, Joseph D. Rosenblatt. EMT-6 tumor conditioned Breg cells inhibit NK cell proliferation and cytotoxic activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3333.

Decreased HLA-C1 alleles in couples of KIR2DL2 positive women with recurrent pregnancy loss

Specific killer cell immunoglobulin-like receptor (KIR) in women with recurrent pregnancy loss (RPL) and HLA ligands in couples invoke a susceptibility to RPL. However, the relationship between KIR2DL2 and its cognate ligand HLA-C1 has not been explored. In this prospective cohort study, 160 Caucasian women with RPL and 99 partners were included. KIR/HLA-C typing, NK assay, Th1/Th2 intracellular cytokine ratios, 25-(OH)-vitamin D level, and the presence of autoantibodies were analyzed. KIR2DL2 positive women (P = 0.023) and their partners (P = 0.017) had lower allele frequencies of HLA-C1 than those of KIR2DL2 negative women. KIR2DL2 positive women had significantly lower genotype frequency of HLA-C1C1 as compared to the North American Caucasian population controls (P < 0.05). In the partners of KIR2DL2 positive women, there was a substantially higher frequency of HLA-C2C2 than controls (P = 0.016). Besides, KIR2DL2 negative women had a higher prevalence of anti-ssDNA antibody as compared with that of KIR2DL2 positive women (P = 0.043). There were no differences in the distribution of HLA-C genotypes based on KIR2DL2, regardless of pregnancy outcome in women with RPL and their partners while on immunomodulation treatment. In conclusion, decreased ligands for inhibitory KIRs (inhKIR) could lead to insufficient inhibition of maternal uterine NK cells toward the trophoblast, thereby contributing to the pathogenesis of RPL. Specific KIR and HLA-C genotyping may predict the reproductive outcome of women with RPL.

Abstract 5614: Combination of anti-TIGIT and anti-PD-1 antibodies enhance antitumor response in a PD-1/TIGIT double HuGEMM™ model engrafted with mouse syngeneic tumors

Abstract Introduction: Ample clinical and preclinical evidence have shown the remarkable antitumor effects of anti-PD-1 antibodies. However, the fact that only around 20% of patients respond to anti-PD-1 immunotherapy indicates that additional inhibitory circuits may be activated to suppress efficient antitumor response, mediated by innate or adaptive immune cells. Notably, TIGIT (T cell immunoreceptor with Ig and ITIM domains) is identified as a co-inhibitory molecule belonging to the PVR family of immunoglobulin (Ig) proteins, and has been shown to inhibit immune cells at multiple steps in the cancer immunity cycle through at least three distinct mechanisms of action: 1. The binding of TIGIT on NK cells to PVR on tumor cells can inhibit NK cell effector function.2. The binding of TIGIT on T cells (Teff and Treg) with PVR on dendritic cells (DCs) or tumor cells can suppress tumor antigen presentation.3. TIGIT on CD8+ T cells can inhibit adjacent CD226 co-stimulatory signaling by binding to PVR at a higher affinity or disrupting the homodimerization of CD226.Therefore, various therapeutic monoclonal antibodies against TIGIT have been developed and are now undergoing clinical testing, for example, tiragolumab (Phase II), BMS-986207 (Phase II), AB-154 (Phase I), MK-7684 (Phase I), etc. However, we are still lacking suitable preclinical models for the efficacy assessment and PK/PD evaluation of human TIGIT antibodies. Methods: We have developed a human TIGIT single knock-in model (TIGIT HuGEMM) as well as a human PD-1/TIGIT double knock-in model (PD-1/TIGIT dKI HuGEMM), of which the extracellular domain of the mouse proteins is replaced by human counterparts, leading to expression of chimeric TIGIT or PD-1 with a human extracellular domain and mouse trans-membrane and intracellular domains. Results: FACS analysis was used to characterize the surface expression of human/mouse chimeric TIGIT on CD4+ and CD8+ T cells. The expression pattern of humanized TIGIT in splenocytes of HuGEMM mice is the same as wild-type mice, with high levels of TIGIT detectable in Treg. We then inoculated Hepa 1-6 syngeneic tumors into TIGIT HuGEMM mice and treated with 1mg/kg or 5mg/kg tiragolumab. Both doses of the TIGIT antibody led to &amp;gt;90% tumor growth inhibition (TGI). We also used Balb/c background PD-1/TIGIT dKI HuGEMM mice to test the antitumor effects of tiragolumab monotherapy and its combination with the anti-PD1 antibody Keytruda®, where CT26.WT syngeneic tumors were treated. We found that tiragolumab monotherapy resulted in modest antitumor effects (41% TGI), while its combination with low dose Keytruda led to much enhanced efficacy (68% TGI). We also observed increased CD8+ T cell infiltration following combination treatment. Conclusions: Our TIGIT KI HuGEMM and PD-1/TIGIT dKI HuGEMM provide powerful preclinical models to assess the efficacy of human TIGIT antibodies and their combination with human anti-PD-1 or other immune modulators. Citation Format: Daniel Xianfei He, Chenpan Nie, Lei Zheng, Ruilin Sun, Mingkun Zhang, Annie Xiaoyu An, Cunxiang Ju, Henry Q. X. Li, Davy Xuesong Ouyang. Combination of anti-TIGIT and anti-PD-1 antibodies enhance antitumor response in a PD-1/TIGIT double HuGEMM™ model engrafted with mouse syngeneic tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5614.

MiR-92 overexpression suppresses immune cell function in ovarian cancer via LATS2/YAP1/PD-L1 pathway

Increasing evidence suggested that microRNA plays an important role in ovarian cancer. In this study, the role of miR-92 in ovarian cancer was investigated. In this study, miR-92 expression in clinical sample was evaluated, role of miR-92 was investigated in vitro, and underlying mechanism was investigated using Chip, co-IP, and western blot. In this study, we show that miR-92 is overexpressed in ovarian cancer tissue compared with normal cancer tissue. Transfection of miR-92 increased proliferation of ovarian cancer cell, and increased migration capacity and colony formation were observed after miR-92 transfection; we found that expression of LATS2 was decreased by miR-92, and this was further confirmed by luciferase assay, which proved that miR-92 is targeting 3' of the endogenous LATS2 gene. Downregulation of LATS2 resulted in increased translocation of YAP1 and upregulation of PD-L1, which subsequently suppressed NK cell function and promoted T cell apoptosis. Moreover, co-transfection of YAP1-targeted shRNA could relieve miR-92-induced immune suppression effect. Mechanically, immunoprecipitation (IP) was used to show that LATS2 interacted with YAP1 and subsequently limited nuclear translocation of YAP1; chromatin immunoprecipitation (ChIP) was used to confirm that YAP1 could bind to enhancer region of PD-L1 to enhance transcription activity of PD-L1. Our data revealed a novel mechanism which finally resulted in immune suppression in ovarian cancer.

Structural basis for RIFIN-mediated activation of LILRB1 in malaria.

The Plasmodium species that cause malaria are obligate intracellular parasites, and disease symptoms occur as they replicate within human blood. Despite risking immune detection, the parasite delivers proteins that bind host receptors to infected erythrocyte surfaces. In the causative agent of the most deadly human malaria, Plasmodium falciparum, RIFINs form the largest erythrocyte surface protein family1. Some RIFINs can bind inhibitory immune receptors, acting as targets for unusual antibodies containing a LAIR1 ectodomain2-4, or as ligands for LILRB15. RIFINs stimulate LILRB1 activation and signalling5, thereby potentially dampening human immune responses. To understand this process, we determined a structure of a RIFIN bound to LILRB1. We show that the RIFIN mimics the natural activating ligand of LILRB1, MHC class I, in its LILRB1-binding mode. A single RIFIN mutation disrupts the complex, blocks LILRB1 binding by all tested RIFINs and abolishes signalling in a reporter assay. In a supported lipid bilayer system, which mimics NK cell activation by antibody- dependent cell-mediated cytotoxicity, both RIFIN and MHC are recruited to the NK cell immunological synapse and reduce cell activation, as measured by perforin mobilisation. Therefore, LILRB1-binding RIFINs mimic the binding mode of the natural ligand of LILRB1 and suppress NK cell function.

Cancer cell-derived exosomal circUHRF1 induces natural killer cell exhaustion and may cause resistance to anti-PD1 therapy in hepatocellular carcinoma

ObjectiveNatural killer (NK) cells play a critical role in the innate antitumor immune response. Recently, NK cell dysfunction has been verified in various malignant tumors, including hepatocellular carcinoma (HCC). However, the molecular biological mechanisms of NK cell dysfunction in human HCC are still obscure.MethodsThe expression of circular ubiquitin-like with PHD and ring finger domain 1 RNA (circUHRF1) in HCC tissues, exosomes, and cell lines was detected by qRT-PCR. Exosomes were isolated from the culture medium of HCC cells and plasma of HCC patients using an ultracentrifugation method and the ExoQuick Exosome Precipitation Solution kit and then characterized by transmission electronic microscopy, NanoSight and western blotting. The role of circUHRF1 in NK cell dysfunction was assessed by ELISA. In vivo circRNA precipitation, RNA immunoprecipitation, and luciferase reporter assays were performed to explore the molecular mechanisms of circUHRF1 in NK cells. In a retrospective study, the clinical characteristics and prognostic significance of circUHRF1 were determined in HCC tissues.ResultsHere, we report that the expression of circUHRF1 is higher in human HCC tissues than in matched adjacent nontumor tissues. Increased levels of circUHRF1 indicate poor clinical prognosis and NK cell dysfunction in patients with HCC. In HCC patient plasma, circUHRF1 is predominantly secreted by HCC cells in an exosomal manner, and circUHRF1 inhibits NK cell-derived IFN-γ and TNF-α secretion. A high level of plasma exosomal circUHRF1 is associated with a decreased NK cell proportion and decreased NK cell tumor infiltration. Moreover, circUHRF1 inhibits NK cell function by upregulating the expression of TIM-3 via degradation of miR-449c-5p. Finally, we show that circUHRF1 may drive resistance to anti-PD1 immunotherapy in HCC patients.ConclusionsExosomal circUHRF1 is predominantly secreted by HCC cells and contributes to immunosuppression by inducing NK cell dysfunction in HCC. CircUHRF1 may drive resistance to anti-PD1 immunotherapy, providing a potential therapeutic strategy for patients with HCC.

Tumor-Derived Exosomes in Immunosuppression and Immunotherapy.

Tumor-derived exosomes (TEX) are involved in cancer development, metastasis, and disease progression. They can modulate angiogenesis to elevate the malignant degree of tumor cells. TEX carry immunosuppressive factors affecting the antitumor activities of immune cells. Tumor cells as well as immune cells secrete immunologically active exosomes which affect intercellular communication, antigen presentation, activation of immune cells, and immune surveillance. Cell proliferation and immune response suppression create a favorable microenvironment for tumor. TEX can inhibit immune cell proliferation, induce apoptosis of activated CD8+ Teffs, suppress NK cell activity, interfere with monocyte differentiation, and promote Treg as well as MDSC expansion. Exosomes of microenvironment cells may also contribute to the development of drug resistance in cancer therapy. An important role of TEX in modulating the sensitivity of tumor cells to immunotherapy is a promising area of research to make the cancer therapy more successful.

A phase I and randomized phase II etctn study of KW-0761 (Mogamulizumab) and MK-3475 (Pembrolizumab) in relapsed and refractory diffuse large B-cell lymphoma.

TPS8072 Background: Diffuse large B-cell lymphoma (DLBCL) escapes host immune responses via inhibition of the B2M and CD58 pathways and upregulation of PD-1 ligands. However, treatment results with PD-1 blockade have been disappointing. One potential mechanism is the recruitment of intra-tumoral regulatory T-cells (Tregs) which suppress anti-tumor immunity and inhibit NK cell cytotoxicity. Targeting regulatory T cells with the CCR4 antibody mogamulizumab (KW-0761) represents a molecularly informed strategy to overcome this resistance. Mogamulizumab has been safely administered in combination with pembrolizumab (MK-3475) in patients with solid malignancies and may promote CD8 T-cell dependent effector and NK cell-dependent cytotoxicity in lymphomas. Methods: This is a multi-center NIH-ETCTN phase Ib/randomized phase II study. The phase I will evaluate the safety and tolerability of mogamulizumab in combination with pembrolizumab in patients with R/R DLBCL and determine the recommended phase II dose (RP2D). A traditional 3+3 design with a starting dose of pembrolizumab 200mg IV on day 1 of a 21-day cycle and mogamulizumab 1mg/kg IV on days 1, 8, 15 and then 1.5 mg/kg IV every 21 days. The phase II will evaluate the efficacy of the combination by PFS (primary endpoint) ORR and CR (secondary endpoints). This will be a randomized 1:1 study with allowed crossover, comparing the combination to single agent pembrolizumab Correlative studies will evaluate the association of tumor infiltrating CD8 and NK cells with response to treatment, somatic mutations in B2M and CD58 and with MHC-I expression on DLBCL cells. Functional characterization of circulating immune cells in the peripheral blood and measurement of pro and anti-inflammatory cytokines will be used to assess the levels, activation status and effector function of Tregs and circulating T cells. Inclusion criteria include measurable disease, ≥2 prior lines of therapy including or ineligible for autologous stem cell transplant, ECOG ≤ 2 and normal organ function. Prior or planned allogeneic stem cell transplant, as well as prior treatment with an anti PD-1/PD-L1/CTLA4 antibody, preexisting autoimmune disease or CNS involvement by lymphoma are exclusion criteria. The study aims to enroll up to 12 patients on the phase I and up to 58 patients on the phase II and can be opened at any ETCTN participating site. To date it has been opened at two sites and is accruing the first patients for the phase I portion. Clinical trial information: NCT03309878 .

Targeting intracellular check points to unleash natural killer cell cytotoxicity

Abstract Natural killer (NK) cells are a potent weapon of the immune system against viral infections and tumor growth. The actomyosin network generates forces through the activity of actin filaments and myosin motors. This machinery is responsible for the conversion of mechanical forces into biochemical signals in a process termed mechanotransduction. However, the mechanism by which mechanotransduction controls the immune response, and specifically lymphocyte activity, is poorly understood. Here, we demonstrate that actomyosin retrograde flow (ARF) controls NK cell response through a novel interaction between beta-actin with the SH2-domain containing protein tyrosine phosphatase-1 (SHP-1), converting its conformation state, thereby regulating NK cell cytotoxicity. Actin dynamics govern SHP-1 conformational structure dictating its catalytic activity. Indeed, blocking actin dynamics results in reduced SHP-1 activity, by confining SHP-1 to its inactivated “closed” conformation. This reduced enzymatic activity of SHP-1 leads to increased phosphorylation of SHP-1 substrates, an elevation of intracellular calcium flux, and NK cell cytotoxicity. Using multidisciplinary approaches including functional and advanced molecular imaging, we followed the signaling events in individual NK cells from the moment of target cell encounter until the final outcome – target cell killing or NK cell inhibition. Our data suggest that SHP-1 plays a major role as a sensor of ARF-generated forces in the process of mechanotransduction, and reveal a novel mechanism by which regulation of SHP-1 by ARF dictates NK cell killing decisions. Our data identify ARF as a master regulator of the lymphocyte response.

Alteration of liver immunity by increasing inflammatory response during co-administration of methamphetamine and atazanavir

Objective: Use of methamphetamine (METH) is prevalent among HIV-infected individuals. Previous research has shown that both METH and HIV protease inhibitors exert influences on mitochondrial respiratory metabolism and hepatic nervous system. This study aims to study the joint effect of METH and HIV protease inhibitors on hepatic immune function.Materials and methods: Based on the differentially expressed genes obtained from RNA-seq of the liver from mouse model, the expression levels of CD48 and Macrophage Receptor with Collagenous Structure (MARCO) were examined using qRT-PCR and flow cytometry, and the expression and secretion of cytokines IL-1β, IL-6, IL-8, IL-10, IFN-γ, IFN-β, and TNF-α were determined using qRT-PCR and ELISA in THP-1-derived macrophages.Results: Our results indicated that compared with the control group, CD48 molecules were significantly down-regulated by METH–atazanavir co-treatment, and the expression level of CD48 decreased as METH concentration increases. MARCO molecules were increased, especially at larger doses of METH and atazanavir treatment. In addition, in the presence of METH–atazanavir, the expression and secretion of a series of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8 increased while the expression and secretion of anti-inflammatory cytokine IL-10 decreased.Conclusion: These results demonstrated that METH and atazanavir had a combined impact on the liver immunity, suggesting that the co-treatment could enhance inflammatory response and suppress NK cell activation via CD48.