Natural Killer Group 2 Member D Research Articles

Contrasting Effects of the Cytotoxic Anticancer Drug Gemcitabine and the EGFR Tyrosine Kinase Inhibitor Gefitinib on NK Cell-Mediated Cytotoxicity via Regulation of NKG2D Ligand in Non-Small-Cell Lung Cancer Cells.

IntroductionSeveral cytotoxic anticancer drugs inhibit DNA replication and/or mitosis, while EGFR tyrosine kinase inhibitors inactivate EGFR signalling in cancer cell. Both types of anticancer drugs improve the overall survival of the patients with non-small-cell lung cancer (NSCLC), although tumors often become refractory to this treatment. Despite several mechanisms by which the tumors become resistant having been described the effect of these compounds on anti-tumor immunity remains largely unknown.MethodsThis study examines the effect of the cytotoxic drug Gemcitabine and the EGFR tyrosine kinase inhibitor Gefitinib on the expression of NK group 2 member D (NKG2D) ligands as well as the sensitivity of NSCLC cells to the NK-mediated lysis.ResultsWe demonstrate that Gemcitabine treatment leads to an enhanced expression, while Gefitinib downregulated the expression of molecules that act as key ligands for the activating receptor NKG2D and promote NK cell-mediated recognition and cytolysis. Gemcitabine activated ATM and ATM- and Rad-3-related protein kinase (ATR) pathways. The Gemcitabine-induced phosphorylation of ATM as well as the upregulation of the NKG2D ligand expression could be blocked by an ATM-ATR inhibitor. In contrast, Gefitinib attenuated NKG2D ligand expression. Silencing EGFR using siRNA or addition of the PI3K inhibitor resulted in downregulation of NKG2D ligands. The observations suggest that the EGFR/PI3K pathway also regulates the expression of NKG2D ligands. Additionally, we showed that both ATM-ATR and EGFR regulate MICA/B via miR20a.ConclusionIn keeping with the effect on NKG2D expression, Gemcitabine enhanced NK cell-mediated cytotoxicity while Gefitinib attenuated NK cell killing in NSCLC cells.

Abstract B45: Mitochondrial Ca2+ transport fine-tunes functional cross-talk between antitumor CD8+T lymphocytes and natural killer cells

Abstract Tumor antigen-specific T cell and natural killer (NK) cell collaboration is indispensable for the elimination of tumor cells, including antigen-deficient tumor escape variants before metastasis. While mechanistic details are available for the innate instruction of T lymphocyte responses, little is known for the adaptive control of NK cell activity. We observed in a mouse model of mastocytoma expressing a self tumor antigen P1A that effector CD8+T cells provided a necessary “help” to dormant NK cells in eliciting their antitumor effector function. Bioluminescence imaging of mastocytoma tumors following adoptive transfer of P1A-specific T cells in RAG-/- and RAG-/-gamma chain-/- mice showed that NK cell anti-tumor activity requires cytolytic T cells, whereas T cells can function independent of NK cells. The goal of present study was to dissect the molecular mechanisms underlying functional cross-talk between activated CD8+T lymphocytes and naïve NK cells. In 2D and 3D co-culture systems, we observed that activated CD8+T cells form multiple intercellular contacts with naïve NK lymphocytes. Moreover, co-culture of activated T cells with naïve NK cells results in the selective down-regulation of CD25 molecule in T cells while elevating CD25 and CD69 expression on naïve NK cells. Further, CD8+T and NK cells cross-regulate their mitochondrial homeostasis including calcium transport. This effect is dependent on both cytokines and intercellular contacts, and partially involves natural killer group 2 member D (NKG2D) receptor activation. Data also indicate that activated CD8+T cells may exchange mitochondria and activation molecules such as CD25 and CD69 with naïve NK cells. Alterations in phosporylation status of multiple signaling proteins during CD8+T-NK interaction suggest a cellular remodeling whereby NK cells shift activated CD8+T cells towards T central-memory (TCM) phenotype and activated CD8+T lymphocytes alter the naïve state of NK cells towards effector/regulatory phenotype. Inhibition of mitochondrial Ca2+ uptake (mCU) or Na+/Ca2+ exchanger (mNCE) with Ru360 and CGP37157, respectively, mimicked observed alterations in CD8+ T and NK cell phenotypes upon their interaction. These results highlight a novel role of mitochondrial Ca2+ homeostasis in the re-modeling of memory differentiation and activation signaling of interacting CD8+T cells and NK cells, respectively. Improved mechanistic understanding of CD8+T-NK interplay will help refine cellular immunotherapy approach against cancer. Citation Format: Roman V. Uzhachenko, J Shawn Goodwin, Lino Costa, Alexander Terekhov, Menaka C. Thounaojam, William H. Hofmeister, Anil Shanker. Mitochondrial Ca2+ transport fine-tunes functional cross-talk between antitumor CD8+T lymphocytes and natural killer cells. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr B45.

The clinical and biological significance of MICA in clear cell renal cell carcinoma patients.

Major histocompatibility complex class I-related chains A (MICA), a ligand of Natural killer group 2, member D (NKG2D) receptor, is broadly upregulated in epithelial originated tumor cells. MICA plays a critical role in the immune surveillance against tumor cells and is associated with the prognosis of several malignancies. The aim of this study is to evaluate the clinical and biological significance of MICA in clear cell renal cell carcinoma (ccRCC). The expression of MICA was analyzed by quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC). Both MICA mRNA and protein levels were upregulated in ccRCC tissues, compared with normal tissues. IHC staining revealed a homogenous pattern of MICA staining within each tumor, which combined both membrane staining and granular cytoplasmic staining. Furthermore, high MICA expression was associated with lymph node metastasis and advanced clinical stage and predicted poor prognosis in patients with ccRCC. Gene set enrichment analysis (GSEA) was performed using RNA-sequencing data from The Cancer Genome Atlas Research Network (TCGA) to elucidate the biological role of MICA in ccRCC and revealed that MICA was significantly associated with the epithelial-to-mesenchymal transition (EMT) gene set, which was further confirmed by qRT-PCR. Our findings contribute to the studies on biomarkers of kidney cancers and the mechanism of renal cancer progression driven by EMT pathway.

Transforming growth factor-β1 regulates human renal proximal tubular epithelial cell susceptibility to natural killer cells via modulation of the NKG2D ligands.

Transforming growth factor-β (TGF-β) has a significant role in the response to injury and tissue repair, and it has been detected in various cell types. However, the mechanism by which it regulates the response to ischemia‑reperfusion injury (IRI) and manipulates natural killer(NK) cells is not well understood. In the present study, TGF‑β modulated NK cell function, thereby promoting recovery from renal IRI. Human renal proximal tubular epithelial cells (HK‑2) treated with TGF‑β exhibited increased surface and intracellular expression of the NK group2 memberD (NKG2D) ligand MICA. This increased surface expression of MICA inhibited NK cell cytotoxicity to the HK‑2 cells. In addition, an enzyme‑linked immunosorbent assay revealed that TGF‑β treatment evidently increased the amount of soluble MICA released into the culture supernatant from HK‑2 cells. Taken together, these findings suggest that TGF‑β‑induced release of soluble MICA leads to downregulation of NKG2D, thereby preventing NK cell‑mediated cytotoxicity toward renal proximal tubular epithelial cells in renal IRI, which in turn improves the survival of these cells.

Identification of Anti-tumor Cells Carrying Natural Killer (NK) Cell Antigens in Patients With Hematological Cancers

Natural killer (NK) cells, a cytotoxic lymphocyte lineage, are able to kill tumor cells in vitro and in mouse models. However, whether these cells display an anti-tumor activity in cancer patients has not been demonstrated. Here we have addressed this issue in patients with several hematological cancers. We found a population of highly activated CD56dimCD16+ NK cells that have recently degranulated, evidence of killing activity, and it is absent in healthy donors. A high percentage of these cells expressed natural killer cell p46-related protein (NKp46), natural-killer group 2, member D (NKG2D) and killer inhibitory receptors (KIRs) and a low percentage expressed NKG2A and CD94. They are also characterized by a high metabolic activity and active proliferation. Notably, we found that activated NK cells from hematological cancer patients have non-NK tumor cell antigens on their surface, evidence of trogocytosis during tumor cell killing. Finally, we found that these activated NK cells are distinguished by their CD45RA+RO+ phenotype, as opposed to non-activated cells in patients or in healthy donors displaying a CD45RA+RO− phenotype similar to naïve T cells. In summary, we show that CD45RA+RO+ cells, which resemble a unique NK population, have recognized tumor cells and degranulate in patients with hematological neoplasias.

Abstract 3148: Implication of highly cytotoxic natural killer cells for esophageal cancer treatment

Abstract Natural killer cell-based immunotherapy is a potential treatment for esophageal cancer due to the cytotoxic effect of NK cell and minimal side effects. Natural Killer Activation and Expansion System (NKAES) is our unique system that capable to produce highly cytotoxic and highly proliferative NK cells. Previous studies showed that NKAES-generated NK cells exerted high cytotoxicity on various types of leukemic cell lines and soft tissue cancer cell lines. Our study focuses on the feasibility of NKAES-generated NK cell immunotherapy for esophageal cancer. To generate NKAES-generated NK, peripheral blood mononuclear cell (PBMC) is co-cultured with feeder cells (genetically modified K562 leukemic cell) in presence of interleukin 2. The feeder cells express 4-1BB ligands and membrane bound interleukin 15, which enhance NK responsiveness to interleukin 2, NK activation, NK proliferation and NK survival. Our NK cytotoxicity assay results indicate that seven esophageal cancer cell lines (TE1, TE2, TE3, TE4, TE5, KYSE110 and KYSE30) are highly sensitive to NKAES-generated NK cells. We further compared the cytotoxicity between resting NK, IL-2 activated NK, and NKAES-generated NK on these cell lines. We found that NKAES-generated NK produced the strongest cytotoxicity on these cancer cell lines. NK cytotoxicity is strongly depending on the expression of NK Group 2 Member D (NKG2D) ligands. During cancer metastasis, NKG2D ligands are shedded off by metalloproteinase, which contributes to immune evasion. Interestingly, a previous study showed that a colorectal cancer cell line was sensitive to NK cytotoxicity in early phase of EMT. We further investigated this phenomena in esophageal cancer. To study this, we successfully established an in vitro model, in which stimulated EMT event in esophageal cancer cell lines by using GSK3β inhibitor and epithelial growth factor (EGF). Astonishingly, beside EMT features, we observed that surface NKG2D ligand expression was higher in EMTed esophageal cancer cells compared with control. In addition, EMTed esophageal cancer cells were much sensitive to NKAES-generated NK cytotoxicity. The difference of NK sensitivity was insignificant in IL-2 activated NK. These findings suggest that early EMT event is a crucial checkpoint to prevent further progression that ultimately lead to cancer metastasis, and NK Immunosurveillance is important in this checkpoint. As a conclusion, NKAES-generated NK cells are capable to exert high cytotoxic effect on esophageal cancer cells as well as to establish a strong checkpoint to prevent the progression of EMT event. Citation Format: Kee Siang Lim, Ley Fang Kua, Kosaku Mimura, Kensuke Shiraishi, Wee Joo Chng, Wei Peng Yong, Dario Campana, Koji Kono. Implication of highly cytotoxic natural killer cells for esophageal cancer treatment. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3148. doi:10.1158/1538-7445.AM2015-3148

Lenalidomide augments actin remodeling and lowers NK-cell activation thresholds

AbstractAs multiple myeloma (MM) progresses, natural killer (NK)-cell responses decline against malignant plasma cells. The immunomodulatory drug lenalidomide is widely used for treatment of MM but its influence on NK-cell biology is unclear. Here, we report that lenalidomide lowers the threshold for NK-cell activation, causing a 66% decrease in the 50% effective concentration (EC50) for activation through CD16, and a 38% decrease in EC50 for NK group 2 member D (NKG2D)–mediated activation, allowing NK cells to respond to lower doses of ligand. In addition, lenalidomide augments NK-cell responses, causing a twofold increase in the proportion of primary NK cells producing interferon-γ (IFN-γ), and a 20-fold increase in the amount of IFN-γ produced per cell. Importantly, lenalidomide did not trigger IFN-γ production in unstimulated NK cells. Thus, lenalidomide enhances the NK-cell arm of the immune response, without activating NK cells inappropriately. Of particular clinical importance, lenalidomide also allowed NK cells to be activated by lower doses of rituximab, an anti-CD20 monoclonal antibody (mAb) widely used to treat B-cell malignancies. This supports combined use of lenalidomide and rituximab in a clinical setting. Finally, superresolution microscopy revealed that lenalidomide increased the periodicity of cortical actin at immune synapses, resulting in an increase in the area of the actin mesh predicted to be penetrable to vesicles containing IFN-γ. NK cells from MM patients also responded to lenalidomide in this way. This indicates that nanometer-scale rearrangements in cortical actin, a recently discovered step in immune synapse assembly, are a potential new target for therapeutic compounds.

Upregulated expression of NKG2D and its ligands give potential therapeutic targets for patients with thymoma.

The activating receptor NKG2D (natural killer group 2, member D) of natural killer (NK) cells promotes tumor immune surveillance by targeting ligands selectively induced on cancer cells, and thus having an important role in antitumor immune response. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present as useful target for immunotherapeutic approaches in cancer. In this study, to elucidate the role of NKG2D-NKG2D ligand interaction in thymoma tissues and to evaluate the potential role of NKG2D ligands as therapeutic target for thymoma, we examined the expression of NKG2D and its specific ligands: MICA (major histocompatibility complex class I chain-related protein A), MICB (major histocompatibility complex class I chain-related protein B) and ULBP (UL16-binding protein) in 36 thymomas (6 subtype A, 6 subtype AB, 8 subtype B1, 5 subtype B2, 6 subtype B3 and 5 subtype C), 15 thymic atrophy and 8 thymic hyperplasia by immunohistochemistry and reverse transcription-real-time-PCR methods. We demonstrated that both mRNA and protein levels of NKG2D, MICA, MICB and ULBP were upregulated in six types of thymomas compared with those in atrophic thymus or proliferating thymus. Furthermore, the NKG2D ligands were found to be frequently coexpressed on thymoma cells. Furthermore, the expression of MICA, MICB and ULBP in subtype C was higher compared with those in subtype A, AB, B1, B2 and B3. Thus, we concluded that high expressions of NKG2D, MICA, MICB and ULBP1 were shown in patients with thymoma, and this may enhance the recognition function of NK cells to eliminate tumor cells. MICA, MICB and ULBP presented an attractive target for thymoma therapy. The abnormal expression of NKG2D, MICA, MICB and ULBP1 can provide us with evidence of the occurrence of thymoma and could also be used as a target in the treatment of thymoma.

Revving up Natural Killer Cells and Cytokine-Induced Killer Cells Against Hematological Malignancies

Natural killer (NK) cells belong to innate immunity and exhibit cytolytic activity against infectious pathogens and tumor cells. NK-cell function is finely tuned by receptors that transduce inhibitory or activating signals, such as killer immunoglobulin-like receptors, NK Group 2 member D (NKG2D), NKG2A/CD94, NKp46, and others, and recognize both foreign and self-antigens expressed by NK-susceptible targets. Recent insights into NK-cell developmental intermediates have translated into a more accurate definition of culture conditions for the in vitro generation and propagation of human NK cells. In this respect, interleukin (IL)-15 and IL-21 are instrumental in driving NK-cell differentiation and maturation, and hold great promise for the design of optimal NK-cell culture protocols. Cytokine-induced killer (CIK) cells possess phenotypic and functional hallmarks of both T cells and NK cells. Similar to T cells, they express CD3 and are expandable in culture, while not requiring functional priming for in vivo activity, like NK cells. CIK cells may offer some advantages over other cell therapy products, including ease of in vitro propagation and no need for exogenous administration of IL-2 for in vivo priming. NK cells and CIK cells can be expanded using a variety of clinical-grade approaches, before their infusion into patients with cancer. Herein, we discuss GMP-compliant strategies to isolate and expand human NK and CIK cells for immunotherapy purposes, focusing on clinical trials of adoptive transfer to patients with hematological malignancies.

Efficient In Vitro Refolding and Characterization of Major Histocompatibility Complex Class I-Related Chain Molecules A (MICA) and Natural Killer Group 2 Member D (NKG2D) Expressed in E. coli.

Major Histocompatibility Complex class I-related chain molecules A (MICA) and receptor Natural killer group 2 member D (NKG2D) are important membrane proteins with immunosurveillance properties which could serve as therapeutic targets for immunotherapy. However, expression of MICA and NKG2D in E. coli often leads to the formation of inclusion bodies. Here, we present simple, inexpensive and convenient protocol for the solubilization and refolding of inclusion bodies of MICA and NKG2D expressed in E. coli. The inclusion bodies were firstly dissolved in strong chaotropic reagent (8M urea) and subsequently purified by immobilized-metal affinity column. The denatured MICA/NKG2D was refolded by gradually removing both denaturant (8M urea) and imidazole via dialysis in dialysis buffer of pH 7.4. The appropriate pH of the dialysis buffer was selected based on the theoretical isoelectric points of MICA and NKG2D which were 5.0 and 5.2 respectively. The folded MICA and NKG2D demonstrated the capacity to bind to recombinant NKG2D and MICA respectively by ELISA, Western blot and Surface Plasmon Resonance (SPR) assays. Additionally, the folded MICA and NKG2D demonstrated significant binding to NKG2D-positive Human leukemic cell line U937 and MICA-positive Human pancreatic carcinoma, epithelial-like cell line (PANC-1) respectively, suggesting successful refolding. Successful refolding was further confirmed by Circular Dichroism spectroscopy (CD). We have successfully dissolved, refolded and characterized inclusion bodies of MICA/NKG2D expressed in E. coli using simple, inexpensive and convenient protocol which can be carried out in laboratories under-resourced.

Studying the antagonistic relationship between NKG2D and TGF-β in CD8+ T cells (IRM14P.449)

Abstract One of the major hurdles in cancer vaccine and adoptive T cell transfer therapy (ACT) development is diminished effectiveness and persistence of T lymphocytes due to immuno-suppressive factors. TGF-β is highly prevalent immuno-suppressive factor secreted by tumor which negatively regulates persistence and functionality of CD8+ T cells. Natural killer group 2, member D (NKG2D) is a stimulatory receptor majorly expressed on the surface of NK and CD8+ T cells. Others including our lab have shown that NKG2D activation on CD8+ T cells enhances their function, proliferation and persistence. Accordingly, we hypothesized that NKG2D signaling reverses the inhibitory effects of TGF-β on CD8+ T cells. We found that in vitro NKG2D activation prevented TGF-β mediated inhibition of proliferation and granzyme B expression in human CD8+ T cells. Interestingly, we also found that TGF-β down regulates the surface expression of NKG2D in human and mouse CD8+ T cells. In the presented research we will test two alternative hypotheses to elucidate molecular mechanism underlying NKG2D and TGF-β’s antagonistic effects. NKG2D opposes TGF-β’s suppressive effects in CD8+ T cells by i) repressing levels of transcription factor T-bet ii) increasing levels of inhibitor of TGF-β signaling-regulator of G-protein signaling 3 (RGS3). The findings from this research will form basis to develop a therapeutic strategy to reverse TGF-β’s immunosuppressive effects in vivo that results in better anti-tumor immunity.

A Thr72Ala polymorphism in the NKG2D gene is associated with early symptomatic congenital cytomegalovirus disease.

The potential risk factors for congenital cytomegalovirus (cCMV) infection or development of disease remain unclear. Here, we investigated the genetic polymorphisms in natural killer (NK) group 2, member D (NKG2D), an activating receptor expressed on NK cells, and in MHC class I-related chains A, the ligand of NKG2D, in 87 cCMV cases, and found that there was a significant association between cCMV disease and a single nucleotide polymorphism, Thr72Ala, in NKG2D.

Restoration of natural killer activity in hepatocellular carcinoma by treatment with antibody against granulin-epithelin precursor

Impairment of natural killer (NK) cell activity is an important mechanism of tumor immunoevasion. We have previously shown that expression of granulin-epithelin precursor (GEP) in hepatocellular carcinoma (HCC) cells rendered the cells resistant to NK cell immunosurveillance. Here, we examined whether targeting GEP could rescue NK activity in HCC patients. The current study demonstrated that quantities and activities of NK cells were significantly lower in HCC patients compared with healthy individuals, and were negatively correlated with GEP levels in HCC cells. NK cells demonstrated enhanced expression of the stimulatory receptors natural-killer group 2, member D (NKG2D) and CD69, increased secretion of IFN-γ and perforin, and cytotoxicity against HCC cells upon GEP suppression. Opposite phenotypes of NK cells were observed when GEP was overexpressed in HCC cells. Importantly, GEP blockage by monoclonal antibody A23 restored NK activity in HCC patients and sensitized HCC cells to NK cytotoxicity. Furthermore, A23 induced NK-mediated antibody-dependent cell-mediated cytotoxicity against HCC. In summary, the activity of NK cells in HCC was impaired by GEP expression, which could be rescued by GEP antibody. This study provides new insight for treatments targeting GEP to boost NK activity in HCC patients.

NKG2D Ligands in Tumor Immunity: Two Sides of a Coin.

The activating/co-stimulatory receptor NKG2D (natural-killer group 2, member D) is expressed on the surface of all human NK, NKT, CD8+ T, and subsets of γδ+ T cells. The significance of NKG2D function in tumor immunity has been well demonstrated in experimental animal models. However, the role of human NKG2D ligands in regulating tumor immunity and cancer prognosis had been controversial in the literature. In this review, we summarize the latest advancement, discuss the controversies, and present evidence that membrane-bound and soluble NKG2D ligands oppositely regulate tumor immunity. We also discuss new perspectives of targeting NKG2D ligands for cancer immunotherapy.

Enhancing Natural Killer Cell-Mediated Lysis of Lymphoma Cells By Combining Therapeutic Antibodies with CD20-Specific Immunoligands Engaging NKG2D or NKp30

Abstract Antibody-dependent cell-mediated cytotoxicity (ADCC) represents a major effector function of many therapeutic antibodies. Thus, enhancing ADCC is a promising approach to further improve antibody therapy. Here, the CD20-specific immunoligands ULBP2:7D8 and B7-H6:7D8, which engage the stimulatory NK cell receptors natural killer group 2 member D (NKG2D) and NKp30, respectively, were compared for their abilities to boost ADCC in an attempt to design an effective antibody combination strategy. The immunoligands are designed as single chain molecules, with a single chain fragment variable (scFv) of the CD20 antibody 7D8 fused to UL16-binding protein (ULBP) 2 or B7 homologue 6 (B7-H6), which are ligands of the activating NK cell receptors NKG2D and NKp30, respectively. By binding to lymphoma cells the immunoligands designated as ULBP2:7D8 and B7-H6:7D8 mimicked an induced self phenotype and thereby triggered NK cells to kill lymphoma and leukemia cells. Both immunoligands augmented ADCC by NK cells synergistically when combined with the lymphoma-directed antibodies rituximab or daratumumab recognizing CD20 and CD38, respectively. Antibody combinations with ULBP2:7D8 resulted in higher cytotoxicity (up to 10-fold lower EC50-values) in comparison to combinations with B7-H6:7D8, which in individual experiments failed to boost ADCC. Thus, NK cells were triggered more efficiently when NKG2D rather than NKp30 was co-ligated together with FcγRIIIA. Although a combination of ULBP2:7D8 and B7-H6:7D8 produced synergistic effects, no significant improvements were obtained by combining the three agents rituximab, B7-H6:7D8 and ULBP2:7D8. Enhancement of ADCC by the immunoligands was also achieved when NK cells from lymphoma or leukemia patients were analyzed as effector cells. ULBP2:7D8 in particular increased lysis not only of allogeneic but also of autologous tumor cells. In summary, co-targeting of NKG2D was more effective in promoting NK cell-mediated ADCC than co-ligation of NKp30 and may represent a promising approach to further enhance the efficacy of therapeutic antibodies. Based on these results we propose a ‘dual-dual-targeting’ concept by co-targeting of two surface antigens on tumor cells and concomitant engagement of two different activating NK cell receptors. Disclosures van de Winkel: Genmab BV: Employment, Patents & Royalties. Parren:Genmab: Employment, Equity Ownership.

Granulin-epithelin precursor renders hepatocellular carcinoma cells resistant to natural killer cytotoxicity.

Immunoevasion is an emerging hallmark of cancer. Impairment of natural killer (NK) cytotoxicity is a mechanism to evade host immunosurveillance. Granulin-epithelin precursor (GEP) is a hepatic oncofetal protein regulating growth, invasion, and chemoresistance in hepatocellular carcinoma (HCC). We examined the role of GEP in conferring HCC cells the ability to evade NK cytotoxicity. In HCC cell lines, GEP overexpression reduced, whereas GEP suppression enhanced sensitivity to NK cytotoxicity. GEP downregulated surface expression of MHC class I chain-related molecule A (MICA), ligand for NK stimulatory receptor NK group 2 member D (NKG2D), and upregulated human leukocyte antigen-E (HLA-E), ligand for NK inhibitory receptor CD94/NKG2A. Functionally, GEP augmented production of soluble MICA, which suppressed NK activation. Matrix metalloproteinase (MMP)2 and MMP9 activity was involved partly in the GEP-regulated MICA shedding from HCC cells. In primary HCCs (n = 80), elevated GEP (P < 0.001), MICA (P < 0.001), and HLA-E (P = 0.089) expression was observed when compared with those in nontumor (n = 80) and normal livers (n = 10). Serum GEP (P = 0.010) and MICA (P < 0.001) levels were higher in patients with HCC (n = 80) than in healthy individuals (n = 30). High serum GEP and/or MICA levels were associated with poor recurrence-free survival (log-rank test, P = 0.042). Importantly, GEP blockade by mAbs sensitized HCC cells to NK cytotoxicity through MICA. In summary, GEP rendered HCC cells resistant to NK cytotoxicity by modulating MICA expression, which could be reversed by GEP blockade using antibody. Serum GEP and MICA levels are prognostic factors and can be used to stratify patients for targeted therapy.

X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection, and neoplasia disease: a combined immune deficiency with magnesium defect.

To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications. The magnesium transporter protein MAGT1 participates in the intracellular magnesium ion (Mg) homeostasis and facilitates a transient Mg influx induced by the activation of the T-cell receptor. Loss-of-function mutations in MAGT1 cause an immunodeficiency named 'XMEN syndrome', characterized by CD4 lymphopenia, chronic EBV infection, and EBV-related lymphoproliferative disorders. Patients with XMEN disease have impaired T-cell activation and decreased cytolytic function of natural killer (NK) and CD8 T cells because of decreased expression of the NK stimulatory receptor 'natural-killer group 2, member D' (NKG2D). Patients may have defective specific antibody responses secondary to T cell dysfunction, but B cells have not been shown to be directly affected by mutations in MAGT1. XMEN disease has revealed a novel role for free intracellular magnesium in the immune system. Further understanding of the MAGT1 signaling pathway may lead to new diagnostic and therapeutic approaches.

MICA/B and ULBP1 NKG2D ligands are independent predictors of good prognosis in cervical cancer.

BackgroundNKG2D (natural killer group 2, member D) is thought to play an important role in mediating the activation of anticancer immune response. Expression of NKG2D ligands (NKG2DLs) is pronounced in malignancies and the heterogeneity of NKG2DL expression remains unclear. Here, we investigate the expression and clinical significance of NKG2DLs in cervical cancer.MethodsImmunohistochemical analyses of MICA/B, ULBP1, ULBP2, ULBP3, RAET1E, and RAET1G were performed using tissue microarray analysis of 200 cervical cancers, 327 high-grade cervical intraepithelial neoplasias (CINs), 99 low-grade CINs, and 541 matched nonadjacent normal cervical epithelial tissues and compared the data with clinicopathologic variables, including the survival of cervical cancer patients.ResultsMICA/B, ULBP1, and RAET1E expression was higher in cervical cancer than in low-grade CIN (p < 0.001, p = 0.012, p = 0.013, respectively) and normal cervix (all p < 0.001). Among these markers, expression of ULBP1 was significantly different depending on patient tumor stage (p = 0.010) and tumor size (p = 0.045). ULBP1 expression was correlated with MICA/B (p < 0.001) and ULBP2 (p = 0.002) expression in cervical cancer. While MICA/B+ or ULBP1+ patients had improved disease-free survival time (p = 0.027 and p = 0.009, respectively) relative to that of the low expression group, RAET1E+ or RAET1G+ was correlated with shorter survival time (p = 0.018 and p = 0.029, respectively). However, in terms of overall survival, the ULBP1+ group had significantly longer survival time than the low expression group (p = 0.009). Multivariate analysis indicated that MICA/B+/ULBP1+ (HR = 0.16, p = 0.015) and ULBP1+ (HR = 0.31, p = 0.024) are independent prognostic factors of disease-free survival in cervical cancer.ConclusionsHigh expression of either ULBP1 or MICA/B and ULBP1 combined is an indicator of good prognosis in cervical cancer, suggesting their potential utility as prognostic tests in clinical assessment.

Methylation of NKG2D ligands contributes to immune system evasion in acute myeloid leukemia.

Engagement of the activating receptor NKG2D (natural killer group 2 member D) with its ligands (NKG2DL) major histocompatibility complex class I related-A and -B (MICA/B), UL-16 binding protein families (ULBPs 1-6) is important to ensure the innate immunity to tumor cells. However, these cells have developed strategies to downregulate NKG2DL expression and avoid immune recognition. We demonstrate that DNA methylation can contribute to the absence of NKG2DL expression during tumor progression. We analyzed the DNA methylation profiles for each NKG2DL by pyrosequencing in acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), hepatocellular carcinoma (HC), breast cancer and colon cancer cell lines. High levels of DNA methylation for NKG2DL were found in some tumor cell lines, mainly in AML cells. This hypermethylation was correlated with the absence of transcription for NKG2DL. Higher DNA methylation levels for MICA, ULBP1 and ULBP2 were observed in AML patients (n=60) compared with healthy donors (n=25). However, no DNA methylation for NKG2DL was found in colon cancer patients (n=44). Treatment with demethylating agents (5-azacytidine and 5-aza-2'-deoxycytidine) restored the expression of NKG2DL on the cell surface of AML cells, leading to an enhanced recognition by NKG2D-expressing cells. Our data suggest that NKG2DL may be aberrantly silenced by DNA methylation as a consequence of tumor development in AML patients.

Cross-talk between CD8+ T cells and natural killers: the role of mitochondrial Aa2+ transport

Unraveling complex interactions between immune cells is a key to the development of new strategies for immunotherapy. In the present study, we investigated functional outcome of bidirectional interaction between activated CD8+T and naive natural killer (NK) cells. We found that phorbol 12-myristate 13-acetate (PMA)/Ionomycin (Io)-stimulated CD8+T cells form multiple intercellular contacts with naive NK lymphocytes. Co-culture of activated T cells with naive NK cells results in the selective down-regulation of CD25 molecule in T cells while elevating CD25 and CD69 expression on naive NK cells. Further, CD8+T and NK cells cross-regulate mitochondrial homeostasis including calcium transport. This effect is dependent on both cytokines and intercellular contacts, and partially involves natural killer group 2 member D (NKG2D) receptor activation. Data also suggest that activated CD8+T cells might directly transfer mitochondria and activation molecules such as CD25 and CD69 to naive NK cells. Alterations in phosporylation status of multiple signaling proteins during CD8+T/NK interaction suggest a functional remodeling whereby NK cells shift activated CD8+T cells towards T central-memory (TCM) phenotype and activated CD8+T lymphocytes alter naive state of NK cells towards effector/regulatory phenotype. Inhibition of mitochondrial Ca2+ uptake (mCU) or Na+/Ca2+ exchanger (mNCE) with Ru360 and {type:entrez-protein,attrs:{text:CGP37157,term_id:875406365,term_text:CGP37157}}CGP37157 respectively mimicked observed alterations in CD8+ and NK cells upon their interaction. These data suggest a potential role of mitochondrial Ca2+ homeostasis in the acquisition of mixed activation/regulatory phenotype by NK cells during T cell-NK cell interaction. We believe that understanding the mechanisms of CD8+-NK interplay will help to develop new approaches for cellular immunotherapy.