Regulation of human DAP10 gene expression in NK and T cells by Ap-1 transcription factors

NKG2D receptor signaling shapes T cell thymic education

The role of natural killer group 2D (NKG2D) in peripheral T cells as a costimulatory receptor is well established. However, its contribution to T cell thymic education and functional imprint is unknown. Here, we report significant changes in development, receptor signaling, transcriptional program, and function in T cells from mice lacking NKG2D signaling. In C57BL/6 (B6) and OT-I mice, we found that NKG2D deficiency results in Vβ chain usage changes and stagnation of the double-positive stage in thymic T cell development. We found that the expression of CD5 and CD45 in thymocytes from NKG2D deficient mice were reduced, indicating a direct influence of NKG2D on the strength of T cell receptor (TCR) signaling during the developmental stage of T cells. Depicting the functional consequences of NKG2D, peripheral OT-I NKG2D-deficient cells were unresponsive to ovalbumin peptide stimulation. Paradoxically, while αCD3/CD28 agonist antibodies led to phenotypic T cell activation, their ability to produce cytokines remained severely compromised. We found that OT-I NKG2D-deficient cells activate STAT5 in response to interleukin-15 but were unable to phosphorylate ERK or S6 upon TCR engagement, underpinning a defect in TCR signaling. Finally, we showed that NKG2D is expressed in mouse and human thymic T cells at the double-negative stage, suggesting an evolutionarily conserved function during T cell development. The data presented in this study indicate that NKG2D impacts thymic T cell development at a fundamental level by reducing the TCR threshold and affecting the functional imprint of the thymic progeny. In summary, understanding the impact of NKG2D on thymic T cell development and TCR signaling contributes to our knowledge of immune system regulation, immune dysregulation, and the design of immunotherapies.

AP-1 transcription factors in cytotoxic lymphocyte development and antitumor immunity

The proper functioning of cytotoxic lymphocytes, such as natural killer and CD8+ T cells, is essential for effective cancer-immunity and immunotherapy responses. The differentiation of these cells is controlled by several transcription factors (TFs), including members of the activator protein (AP)-1 family. The activity of AP-1 family members is regulated by various immune signaling pathways, which can be triggered by activating or inhibitory receptors as well as cytokines. The target genes controlled by AP-1 TFs are central to generate immunity to pathogens or malignancies. Here, we provide an overview of the current understanding of how AP-1 TFs regulate cytotoxic lymphocytes.

Fluid shear stress enhances natural killer cell's cytotoxicity toward circulating tumor cells through NKG2D-mediated mechanosensing

Tumor cells metastasize to distant organs mainly via hematogenous dissemination, in which circulating tumor cells (CTCs) are relatively vulnerable, and eliminating these cells has great potential to prevent metastasis. In vasculature, natural killer (NK) cells are the major effector lymphocytes for efficient killing of CTCs under fluid shear stress (FSS), which is an important mechanical cue in tumor metastasis. However, the influence of FSS on the cytotoxicity of NK cells against CTCs remains elusive. We report that the death rate of CTCs under both NK cells and FSS is much higher than the combined death induced by either NK cells or FSS, suggesting that FSS may enhance NK cell's cytotoxicity. This death increment is elicited by shear-induced NK activation and granzyme B entry into target cells rather than the death ligand TRAIL or secreted cytokines TNF-α and IFN-γ. When NK cells form conjugates with CTCs or adhere to MICA-coated substrates, NK cell activating receptor NKG2D can directly sense FSS to induce NK activation and degranulation. These findings reveal the promotive effect of FSS on NK cell's cytotoxicity toward CTCs, thus providing new insight into immune surveillance of CTCs within circulation.

Adapter CAR T Cell Therapy for the Treatment of B-Lineage Lymphomas

CD19CAR T cells facilitate a transformational treatment in various relapsed and refractory aggressive B-lineage cancers. In general, encouraging response rates have been observed in B-lineage-derived non-Hodgkin’s lymphomas treated with CD19CAR T cells. The major cause of death in heavily pretreated NHL patients is lymphoma progression and lymphoma recurrence. Inefficient CAR T cell therapy is the result of the limited potency of the CAR T cell product or is due to loss of the targeted antigen. Target antigen loss has been identified as the key factor that can be addressed stringently by dual- or multitargeted CAR T cell approaches. We have developed a versatile adapter CAR T cell technology (AdCAR) that allows multitargeting. Screening of three different B-lineage lymphoma cell lines has revealed distinct immune target profiles. Cancer-specific adapter molecule combinations may be utilized to prevent antigen immune escape. In general, CD19CAR T cells become non-functional in CD19 negative lymphoma subsets; however, AdCAR T cells can be redirected to alternative target antigens beyond CD19, such as CD20, CD22, CD79B, and ROR-1. The capability to flexibly shift CAR specificity by exchanging the adapter molecule’s specificity broadens the application and significantly increases the anti-leukemic and anti-lymphoma activity. The clinical evaluation of AdCAR T cells in lymphoma as a new concept of CAR T cell immunotherapy may overcome treatment failure due to antigen immune escape in monotargeted conventional CAR T cell therapies.

Mouse fetal growth restriction through parental and fetal immune gene variation and intercellular communications cascade

Fetal growth restriction (FGR) affects 5-10% of pregnancies, and can have serious consequences for both mother and child. Prevention and treatment are limited because FGR pathogenesis is poorly understood. Genetic studies implicate KIR and HLA genes in FGR, however, linkage disequilibrium, genetic influence from both parents, and challenges with investigating human pregnancies make the risk alleles and their functional effects difficult to map. Here, we demonstrate that the interaction between the maternal KIR2DL1, expressed on uterine natural killer (NK) cells, and the paternally inherited HLA-C*0501, expressed on fetal trophoblast cells, leads to FGR in a humanized mouse model. We show that the KIR2DL1 and C*0501 interaction leads to pathogenic uterine arterial remodeling and modulation of uterine NK cell function. This initial effect cascades to altered transcriptional expression and intercellular communication at the maternal-fetal interface. These findings provide mechanistic insight into specific FGR risk alleles, and provide avenues of prevention and treatment.

Fra-2 Is a Dominant Negative Regulator of Natural Killer Cell Development

Natural killer (NK) cells play an important role in recognizing and killing pathogen-infected or malignant cells. Changes in their numbers or activation can contribute to several diseases and pathologies including systemic sclerosis (SSc), an autoimmune disease characterized by inflammation and tissue remodeling. In these patients, increased expression of the AP-1 transcription factor, Fra-2 was reported. In mice ectopic overexpression of Fra-2 (TG) leads to SSc with strong pulmonary fibrosis, pulmonary hypertension, and inflammation. Analysis of the underlying immune cell profile in the lungs of young TG mice, which do not yet show any signs of lung disease, revealed increased numbers of eosinophils and T cells but strongly reduced NK numbers. Therefore, we aimed to identify the cause of the absence of NK cells in the lungs of these mice and to determine the potential role of Fra-2 in NK development. Examination of inflammatory cell distribution in TG mice revealed similar NK deficiencies in the spleen, blood, and bone marrow. Deeper analysis of the WT and TG bone marrow revealed a potential NK cell developmental defect beginning at the preNKP stage. To determine whether this defect was cell-intrinsic or extrinsic, mixed bone marrow chimera and in vitro differentiation experiments were performed. Both experiments showed that the defect caused by Fra-2 was primarily cell-intrinsic and minimally dependent on the environment. Closer examination of surface markers and transcription factors required for NK development, revealed the expected receptor distribution but changes in transcription factor expression. We found a significant reduction in Nfil3, which is essential for the transition of common lymphoid cells to NK committed precursor cells and an AP-1 binding site in the promotor of this gene. In Summary, our data demonstrates that regulation of Fra-2 is essential for NK development and maturation, and suggests that the early NK dysfunction plays an important role in the pathogenesis of systemic sclerosis.

ASB2 is a direct target of FLI1 that sustains NF-κB pathway activation in germinal center-derived diffuse large B-cell lymphoma

Background

Diffuse large B-cell lymphoma (DLBCL) comprises at least two main biologically distinct entities: germinal center B-cell (GCB) and activated B-cell (ABC) subtype. Albeit sharing common lesions, GCB and ABC DLBCL present subtype-specific oncogenic pathway perturbations. ABC DLBCL is typically characterized by a constitutively active NF-kB. However, the latter is seen in also 30% of GCB DLBCL. Another recurrent lesion in DLBCL is an 11q24.3 gain, associated with the overexpression of two ETS transcription factors, ETS1 and FLI1. Here, we showed that FLI1 is more expressed in GCB than ABC DLBCL and we characterized its transcriptional network.

Methods

Gene expression data were obtained from public datasets GSE98588, phs001444.v2.p1, GSE95013 and GSE10846. ChIP-Seq for FLI1 paired with transcriptome analysis (RNA-Seq) after FLI1 silencing (siRNAs) was performed. Sequencing was carried out using the NextSeq 500 (Illumina). Detection of peaks was done using HOMER (v2.6); differential expressed genes were identified using moderated t-test (limma R-package) and functionally annotated with g:Profiler. ChIP-Seq and RNA-Seq data from GCB DLBCL cell lines after FLI1 downregulation were integrated to identify putative direct targets of FLI1.

Results

Analysis of clinical DLBCL specimens showed that FLI1 gene was more frequently expressed at higher levels in GCB than in ABC DLBCL and its  protein levels were higher in GCB than in ABC DLBCL cell lines. Genes negatively regulated by FLI1 included tumor suppressor genes involved in negative regulation of cell cycle and hypoxia. Among positively regulated targets of FLI1, we found genes annotated for immune response, MYC targets, NF-κB and BCR signaling and NOTCH pathway genes. Of note, direct targets of FLI1 overlapped with genes regulated by ETS1, the other transcription factor gained at the 11q24.3 locus in DLBCL, suggesting a functional convergence within the ETS family. Positive targets of FLI1 included the NF-κB-associated ASB2, a putative essential gene for DLBCL cell survival. ASB2 gene downregulation was toxic in GCB DLBCL cell lines and induced NF-κB inhibition via downregulation of RelB and increased IκBα. Additionally, downregulation of FLI1, but not ASB2, caused reduction of NF-κB1 and RelA protein levels.

Conclusions

We conclude that FLI1 directly regulates a network of biologically crucial genes and processes in GCB DLBCL. FLI1 regulates both the classical NF-κB pathway at the transcriptional level, and the alternative NF-κB pathway, via ASB2. FLI1 and ASB2 inhibition represents a potential novel therapeutic approach for GCB DLBCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02159-3.

Role of ETS1 in the Transcriptional Network of Diffuse Large B Cell Lymphoma of the Activated B Cell-Like Type

Diffuse large B cell lymphoma (DLBCL) is a heterogenous disease that has been distinguished into at least two major molecular entities, the germinal center-like B cell (GCB) DLBCL and activated-like B cell (ABC) DLBCL, based on transcriptome expression profiling. A recurrent ch11q24.3 gain is observed in roughly a fourth of DLBCL cases resulting in the overexpression of two ETS transcription factor family members, ETS1 and FLI1. Here, we knocked down ETS1 expression by siRNA and analyzed expression changes integrating them with ChIP-seq data to identify genes directly regulated by ETS1. ETS1 silencing affected expression of genes involved in B cell signaling activation, B cell differentiation, cell cycle, and immune processes. Integration of RNA-Seq (RNA sequencing) data and ChIP-Seq (chromatin immunoprecipitation sequencing) identified 97 genes as bona fide, positively regulated direct targets of ETS1 in ABC-DLBCL. Among these was the Fc receptor for IgM, FCMR (also known as FAIM3 or Toso), which showed higher expression in ABC- than GCB-DLBCL clinical specimens. These findings show that ETS1 is contributing to the lymphomagenesis in a subset of DLBCL and identifies FCMR as a novel target of ETS1, predominantly expressed in ABC-DLBCL.

The Antitumor Effect of Xihuang Pill on Treg Cells Decreased in Tumor Microenvironment of 4T1 Breast Tumor-Bearing Mice by PI3K/AKT~AP-1 Signaling Pathway

To study the antitumor effect of Xihuang pill (XHP) on the number of Treg cells in the tumor microenvironment of 4T1 breast tumor-bearing mice by PI3K/AKT/AP-1 pathway, a mouse model was established. Flow cytometry (FCM) and immunohistochemistry (IHC) were used to detect the number of Treg cells in the tumor microenvironment; terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was used to detect the apoptosis of Treg cells in tumor microenvironment. Quantitative real-time PCR (RT-qPCR) was used to detect the mRNA expression of PI3K, AKT, and AP-1 in Treg cells in tumor microenvironment; immunofluorescence (IF) and Western Blot (WB) were used to detect the protein expression of PI3K, AKT, and AP-1 in Treg cells in tumor microenvironment. Compared with the naive control group, the tumor weight in XHP groups decreased significantly (P < 0.05); FCM and IHC results showed that the number of Treg cells in the tumor microenvironment decreased with the dose of XHP groups (P < 0.05); TUNEL staining showed that the number of Treg cells in tumor microenvironment increased with the dose of XHP groups (P < 0.05); RT-qPCR results showed that the mRNA expression of PI3K and AKT in Treg cells decreased with the dose of XHP groups, while RNA expression of AP-1 increased with the dose of XHP groups (P < 0.05); IF and WB results showed that the protein expression of PI3K and AKT in Treg cells decreased with the dose of XHP groups and the protein expression of AP-1 increased with the dose of XHP groups (P < 0.05). The results suggested that XHP decreased the number of Treg cells via inhibiting PI3K and AKT expression and upregulating AP-1 expression in Treg cells and then promoting the apoptosis of Treg cells. Thus, XHP could improve the immunosuppressive state of tumor microenvironment and reverse the immune escape to inhibit tumor growth.

MicroRNA-30c promotes natural killer cell cytotoxicity via up-regulating the expression level of NKG2D

AIMS

Natural killer (NK) cells play critical roles in antitumor immunity. Our previous study showed that over-expression of miR-30c-1* enhanced NKL cell cytotoxicity through up-regulation of tumor necrosis factor-α via directly targeting transcription factor homeobox containing 1. MiR-30c, the complimentary microRNA of miR-30c-1*, has been found to exert regulatory effect on T cell function. However, the effect of miR-30c on NK cells is unknown. Therefore, this study aimed to investigate whether miR-30c could play a role to enhance NK cell activation and cytotoxicity.

MAIN METHODS

Chemosynthesis exogenous miR-30c mimics and miR-30c inhibitor were transfected into NKL cells and isolated human peripheral blood NK cells, respectively. The expression levels of NK group 2, member D (NKG2D), CD107a and FasL on cell surface and cytotoxic ability of miRNAs transfected NKL cells against SMMC-7721 cells were evaluated.

KEY FINDINGS

MiR-30c could increase the expression of NKG2D and CD107a on NKL cells, and enhance cytotoxic ability of NKL cells to kill SMMC-7721 cells. Moreover, miR-30c could up-regulate the expression of FasL on both NKL cells and human peripheral blood NK cells. However, the peripheral blood NK cells from only four in ten healthy donors appeared high expression levels of NKG2D and CD107a after miR-30c transfection.

SIGNIFICANCE

MiR-30c could promote the cytotoxicity of NKL cells in vitro by up-regulating the expression levels of NKG2D, CD107a and FasL. However, the effect of miR-30c on ex vivo NK cells from different human individuals is diverse, indicating that miR-30c may play complicate and fine adjustment in immune system.

Functional analysis of differences in transcriptional activity conferred by genetic variants in the 5' flanking region of the IL12RB2 gene

Interleukin 12 receptor β chain (IL12RB2) is a crucial regulatory factor involved in cell-mediated immune responses, and genetic variants of the gene encoding IL12RB2 are associated with susceptibility to various immune-related diseases. We previously demonstrated that haplotypes with single nucleotide polymorphisms (SNPs) in the 5' flanking region of IL12RB2, including -1035A>G (rs3762315) and -1023A>G (rs3762316), affect the expression of IL12RB2, thereby altering susceptibility to leprosy and periodontal diseases. In the present study, we identified transcription factors associated with the haplotype-specific transcriptional activity of IL12RB2 in T cells and NK cells. The -1023G polymorphism was found to create a consensus binding site for the transcription factor activating protein (AP)-1, and enzyme-linked immunosorbent assay (ELISA)-based binding assays showed that these SNPs enhanced AP-1 binding to this region. In reporter assays, suppression of JunB expression using siRNA eliminated differences in the -1035G/-1023G and -1035A/-1023A regions containing IL12RB2 promoter activity in Jurkat T cells and NK3.3 cells. These results suggested that the -1035/-1023 polymorphisms created differential binding affinities for JunB that could lead to differential IL12RB2 expression. Moreover, the -1035G and -1035A alleles formed binding sites for GATA-3 and myocyte enhancer factor-2 (MEF-2), respectively. Our data indicated that in addition to JunB, the SNP at -1035/-1023 influenced GATA-3 and MEF-2 binding affinity, potentially altering IL12RB2 transcriptional activity. These findings confirm the effects of rs3762315 and rs3762316 on IL12RB2 transcription. These genetic variants may alter cellular activation of T cells and NK cells and modify cell-mediated immune responses.

Development of NK cell expansion methods using feeder cells from human myelogenous leukemia cell line

Background

Natural killer (NK) cells constantly survey surrounding tissues and remove newly generated cancer cells, independent of cancer antigen recognition. Although there have been a number of attempts to apply NK cells for cancer therapy, clinical application has been somewhat limited because of the difficulty in preparing a sufficient number of NK cells. Therefore, ex vivo NK cell expansion is one of the important steps for developing NK cell therapeutics.

Methods

CD3⁺ depleted lymphocytes were cocultured with IL-2 and with feeder cells (peripheral blood mononuclear cells [PBMCs], K562, and Jurkat) for 15 days. Expanded NK cells were tested for cytotoxicity against cancer cell lines.

Results

We compared feeder activities of three different cells-PBMC, K562, and Jurkat. K562 expanded NK cells by almost 20 fold and also showed powerful cytotoxic activity against cancer cells. K562-NK cells remarkably expressed the NK cell activation receptors, NKG2D, and DNAM-1. K562-NK cells exhibited more than two-fold production of cytotoxic granules compared with Jurkat-NK cells, producing more perforin and granzyme B than naïve NK cells.

Conclusion

Our findings suggest that K562 are more efficient feeder cells than Jurkat or PBMCs. K562 feeder cells expanded NK cells by almost 20 fold and showed powerful cytotoxic activity against cancer cells. We herein propose an intriguing approach for a design of NK cell expansion.

Transcription of the activating receptor NKG2D in natural killer cells is regulated by STAT3 tyrosine phosphorylation

Signal transducer and activator of transcription 3 (STAT3) is considered a negative regulator of inflammation, as inhibition of STAT3 signaling enhances antitumor immunity. However, STAT3 activation is a key oncogenic pathway in natural killer (NK)-lineage large granular lymphomas, and we recently reported enhanced proliferation and function of human NK cells activated with IL-21, which signals primarily through STAT3. These IL-21-expanded NK cells also have increased NKG2D expression, which led us to focus our investigation on whether STAT3 regulates NKG2D. In this study, we show that modulation of STAT3 phosphorylation with cytokines and small-molecule inhibitors correlates with NKG2D expression on human NK cells, leading to altered NK-cell degranulation. Moreover, NKG2D expression on murine NK cells having conditional STAT3 ablation is lower than on NK cells from wild-type mice, and human NK cells carrying dominant-negative STAT3 mutations have decreased baseline NKG2D expression and blunted responses to IL-10 and IL-21. Lastly, we show binding of STAT3 to a predicted STAT3 binding site upstream of the NKG2D gene, which is enhanced by IL-10 and IL-21 and decreased by STAT3 inhibition. Taken together, these data show that NKG2D expression in NK cells is regulated at the transcriptional level by STAT3, resulting in a functional NK cell defect in patients with STAT3 mutations.

The natural killer-activating receptor, NKG2D, on CD3+CD8+ T cells plays a critical role in identifying and killing autologous myeloma cells

BACKGROUND

The NKG2D receptor, one of the natural killer (NK) cell-activating receptors, is expressed on the surface of CD3+CD8+ T cells, γδ+ T cells, NK cells, NKT cells, and a few CD4+ T cells. We show, for the first time, a critical role for the NKG2D receptor on CD3+CD8+ T cells isolated from myeloma patients, in identifying and killing autologous myeloma cells isolated from the same patients' marrow. We also show that blocking NKG2D using anti-NKG2D reverses the cytotoxicity while blocking HLA-I using antibodies does not have the same effect, showing that the autologous cytotoxicity is NKG2D dependent and major histocompatibility complex (MHC)-I independent. We further confirmed the NKG2D specificity by small interfering RNA (siRNA) down regulation of NKG2D receptor.

STUDY DESIGN AND METHODS

Using ex vivo expansion methods that enrich for NKG2D+CD3+CD8+ T cells, we investigated whether these ex vivo expanded NKG2D+CD3+CD8+ T cells would recognize and lyse autologous and allogeneic myeloma cells, independent of T-cell receptor or MHC-I expression.

RESULTS

Myeloma cell lysis by the NKG2D+CD3+CD8+ T cells correlated with the amount of NKG2D ligand expression. With receptor-ligand interaction, interferon-γ and tumor necrosis factor-α were released. Blocking the NKG2D receptor by using either monoclonal antibodies or siRNAs inhibited the receptor's function and prevented myeloma cell lysis.

CONCLUSION

Clinical trials are ongoing to determine a correlation with the number and function of NKG2D+CD3+CD8+ T cells and clinical outcomes in transplanted myeloma patients, including lymphocyte recovery following transplant and overall survival.

Runx3-mediated transcriptional program in cytotoxic lymphocytes

The transcription factor Runx3 is highly expressed in CD8⁺ T and NK cytotoxic lymphocytes and is required for their effective activation and proliferation but molecular insights into the transcription program regulated by Runx3 in these cells are still missing. Using Runx3-ChIP-seq and transcriptome analysis of wild type vs. Runx3^-/- primary cells we have now identified Runx3-regulated genes in the two cell types at both resting and IL-2-activated states. Runx3-bound genomic regions in both cell types were distantly located relative to gene transcription start sites and were enriched for RUNX and ETS motifs. Bound genomic regions significantly overlapped T-bet and p300-bound enhancer regions in Runx3-expressing Th1 helper cells. Compared to resting cells, IL-2-activated CD8⁺ T and NK cells contain three times more Runx3-regulated genes that are common to both cell types. Functional annotation of shared CD8⁺ T and NK Runx3-regulated genes revealed enrichment for immune-associated terms including lymphocyte activation, proliferation, cytotoxicity, migration and cytokine production, highlighting the role of Runx3 in CD8⁺ T and NK activated cells.

Natural killer cells in patients with allergic diseases

Natural killer (NK) cells not only exert cytotoxic activity against tumor cells or infected cells but also act to regulate the function of other immune cells through secretion of cytokines and chemokines or cell contact-dependent mechanisms. NK cells are able to polarize in vitro into 2 functional distinct subsets, NK1 or NK2 cells, which are analogous to the T-cell subsets TH1 or TH2. In addition, a regulatory NK cell subset has been described that secretes IL-10, shows antigen-specific T-cell suppression, and suppresses IgE production. Although it has been demonstrated that NK cells play important roles in autoimmunity, cancer, transplantation, and pregnancy, the role of NK cells in allergy has not been extensively discussed. This review aims to discuss our understanding of NK cells and NK cell subsets in allergic inflammation and IgE regulation.

The AP-1 transcription factor JunD activates the leukocyte immunoglobulin-like receptor 1 distal promoter

Leukocyte immunoglobulin-like receptor 1 (LILRB1) is an inhibitory receptor that binds classical and non-classical MHC-I as well as UL18, a viral MHC-I homolog. LILRB1 is encoded within the leukocyte receptor complex and is widely expressed on immune cells. Two distinct promoters used differentially by lymphoid and myeloid cells were previously identified, but little is known regarding molecular regulation of each promoter or cell-type-specific usage. Here, we have investigated the transcriptional regulation of human LILRB1 focusing on elements that drive expression in NK cells. We found that while both the distal and proximal promoter regions are active in reporter plasmids in lymphoid and myeloid cells, the proximal promoter is used minimally to transcribe LILRB1 in NK cells compared with monocytes. We defined a 120-bp core region of transcriptional activity in the distal promoter that can bind several factors in NK cell nuclear extracts. Within this region, we investigated overlapping putative AP-1 sites. An inhibitor of JNK decreased LILRB1 transcript in a LILRB1⁺ NK cell line. Upon examining binding of specific AP-1 factors, we found JunD associated with the LILRB1 distal promoter. Finally, depletion of JunD led to a decrease in distal promoter transcript, indicating an activating role for JunD in regulation of LILRB1 transcription. This study presents the first description of regions/factors required for activity of the LILRB1 distal promoter, the first description of a role for JunD in NK cells and suggests a potential mechanism for dynamic regulation of LILRB1 by cytokines.

miR-30c-1* promotes natural killer cell cytotoxicity against human hepatoma cells by targeting the transcription factor HMBOX1

Natural killer (NK) cells play a critical role in antitumor immunity, and the activation of NK cells is regulated by a series of NK cell receptors. Here, we show that crosslinking CD226, an important NK cell receptor, with the anti-CD226 mAb LeoA1 on NKL cells, regulated the expression of several microRNA and transmembrane tumor necrosis factor-α. Among them, miR-30c-1(*) was noticed because overexpression of miR-30c-1(*) triggered upregulation of transmembrane tumor necrosis factor-α expression and enhanced NK cell cytotoxicity against hepatoma cell lines SMMC-7721 and HepG2. Furthermore, we proved that the inhibitory transcription factor HMBOX1, which depressed the activation of NK cells, was the direct target gene of miR-30c-1(*). In conclusion, our results revealed a novel regulatory mechanism: miR-30c-1(*) promoted NK cell cytotoxicity against hepatoma cells by targeting HMBOX1.

Complex regulation of human NKG2D-DAP10 cell surface expression: opposing roles of the γc cytokines and TGF-β1

Natural killer (NK) cells help protect the host against viral infections and tumors. NKG2D is a vital activating receptor, also expressed on subsets of T cells, whose ligands are up-regulated by cells in stress. Ligation of NKG2D leads to phosphorylation of the associated DAP10 adaptor protein, thereby activating immune cells. Understanding how the expression of NKG2D-DAP10 is regulated has implications for immunotherapy. We show that IL-2 and TGF-β1 oppositely regulate NKG2D-DAP10 expression by NK cells. IL-2 stimulation increases NKG2D surface expression despite a decrease in NKG2D mRNA levels. Stimulation with IL-2 results in a small increase of DAP10 mRNA and a large up-regulation of DAP10 protein synthesis, indicating that IL-2-mediated effects are mostly posttranscriptional. Newly synthesized DAP10 undergoes glycosylation that is required for DAP10 association with NKG2D and stabilization of NKG2D expression. TGF-β1 has an opposite and dominant effect to IL-2. TGF-β1 treatment decreases DAP10, as its presence inhibits the association of RNA polymerase II with the DAP10 promoter, but not NKG2D mRNA levels. This leads to the down-regulation of DAP10 expression and, as a consequence, NKG2D protein as well. Finally, we show that other γ(c) cytokines act similarly to IL-2 in up-regulating DAP10 expression and NKG2D-DAP10 surface expression.

Expression, signaling proficiency, and stimulatory function of the NKG2D lymphocyte receptor in human cancer cells

The stimulatory natural killer group 2 member D (NKG2D) lymphocyte receptor and its tumor-associated ligands are important mediators in the immune surveillance of cancer. With advanced human tumors, however, persistent NKG2D ligand expression may favor tumor progression. We have found that cancer cells themselves express NKG2D in complex with the DNAX-activating protein 10 (DAP10) signaling adaptor. Triggering of NKG2D on ex vivo cancer cells or on tumor lines which express only few receptor complexes activates the oncogenic PI3K-protein kinase B (PKB/AKT)-mammalian target of rapamycin (mTOR) signaling axis and downstream effectors, the ribosomal protein S6 kinase 1 (S6K1) and the translation initiation factor 4E-binding protein 1 (4E-BP1). In addition, as in lymphocytes, NKG2D ligand engagement stimulates phosphorylation of JNK and ERK in MAP kinase cascades. Consistent with these signaling activities, above-threshold expression of NKG2D-DAP10 in a ligand-bearing tumor line increases its bioenergetic metabolism and proliferation, thus suggesting functional similarity between this immunoreceptor and tumor growth factor receptors. This relationship is supported by significant correlations between percentages of cancer cells that are positive for surface NKG2D and criteria of tumor progression. Hence, in a conceptual twist, these results suggest that tumor co-option of NKG2D immunoreceptor expression may complement the presence of its ligands for stimulation of tumor growth.

Human Vgamma9Vdelta2 T cells: from signals to functions

Human Vgamma9Vdelta2 T cells, a major innate-like peripheral T cell subset, are thought to play in vivo a key role in innate and adaptive immune responses to infection agents and tumors. Vgamma9Vdelta2 T cell activation is tightly regulated by a variety of activating or inhibitory receptors which are specific for constitutively expressed or stress-modulated ligands. However, the mechanisms and signal transduction pathways regulating their broad effector functions, such as cytotoxicity and cytokine responses, remain poorly understood. Here we provide an updated overview of the activation modalities of Vgamma9Vdelta2 T cells by highlighting the respective role played by T cell receptor (TCR) versus non-TCR stimuli, and focus on recent studies showing how Vgamma9Vdelta2 T cells integrate the numerous activating and inhibitory signals and translate them into a particular effector and biological function. A better understanding of these critical issues should help optimize immunotherapeutic approaches targeting Vgamma9Vdelta2 T cells.

Ran overexpression leads to diminished T cell responses and selectively modulates nuclear levels of c-Jun and c-Fos

Ras-related nuclear protein (Ran) is a Ras family GTPase, and its documented functions are the regulation of DNA replication, cell cycle progression, nuclear structure formation, RNA processing and exportation, and nuclear protein importation. In this study, we performed detailed mapping of Ran expression during mouse ontogeny using in situ hybridization. High Ran expression was found in various organs and tissues including the thymus cortex and spleen white pulp. Ran was induced in T cells 24 h after their activation. The function of Ran in the immune system was investigated using Ran transgenic (Tg) mice. In Ran Tg T cells, there was compromised activation marker expression, lymphokine secretion, and proliferation upon T cell receptor activation in vitro when compared with wild type T cells. Tg mice also manifested defective delayed type hypersensitivity in vivo. Upon PMA and ionomycin stimulation, Tg T cells were defective in nuclear accumulation of AP-1 factors (c-Jun and c-Fos) but not NF-kappaB family members. Our experiments showed that Ran had important regulatory function in T cell activation. One of the possible mechanisms is that intracellular Ran protein levels control the nuclear retention for selective transcription factors such as c-Jun and c-Fos of AP-1, which is known to be critical in T cell activation and proliferation and lymphokine secretion.

Evidence for no relevance of anti-major histocompatibility complex class I-related chain a antibodies in liver transplantation

The polymorphic major histocompatibility complex class I-related chain A (MICA) antigen is being increasingly recognized as a potential target molecule for immune cells during allograft rejection. Here we studied whether MICA is a target antigen for antibodies in liver transplant patients. Eighty-four patients were investigated for the presence of MICA antibodies before and after liver transplantation with MICA-transfected cells and flow cytometry. MICA typing was performed by polymerase chain reaction. Expression of MICA in liver cells was determined by reverse-transcription polymerase chain reaction, Western blotting, and flow cytometry. Liver biopsy specimens from liver transplant patients were examined for MICA expression. A total of 22 of 84 (26%) patients had MICA antibodies either pre-transplant (8/84, 9.5%) or post-transplant (14/84, 17%). No correlation between rejection frequencies (14/22, 63%) or other clinical parameters was observed in patients with MICA antibody versus those without MICA antibody (29/62, 47% P = not significant). We found weak messenger RNA expression for MICA in liver cells but no protein or cell surface expression. In addition, no MICA expression in liver biopsy sections from liver transplant patients was observed at any time point, including rejections. Thus, our preliminary results demonstrate no causal relationship between the presence of MICA antibodies and liver allograft rejections. Therefore, it is likely that MICA may not be an important target antigen during liver allograft rejections.

The NKG2D receptor: sensing stressed cells

The activating killer cell lectin-like receptor NKG2D plays a key role in the natural killer (NK) cell-mediated lysis of tumours and infected cells. Unlike other receptors, the ligands recognised by NKG2D are 'induced-self' ligands on stressed cells. This system requires precise regulation because inappropriate expression of NKG2D ligands might compromise NK cell activation. For therapeutic purposes it is essential to understand the mechanisms that regulate the expression and function of the NKG2D system. This review focuses on the importance of the signalling pathways involved in the regulation of the NKG2D receptor and its ligand expression in arming the immune response against infected or tumour cells and for the identification of new molecular targets and therapeutic strategies.