ULBP2

Gene Summary

Gene:ULBP2; UL16 binding protein 2
Aliases: N2DL2, RAET1H, NKG2DL2, ALCAN-alpha
Location:6q25
Summary:This gene encodes a major histocompatibility complex (MHC) class I-related molecule that binds to the NKG2D receptor on natural killer (NK) cells to trigger release of multiple cytokines and chemokines that in turn contribute to the recruitment and activation of NK cells. The encoded protein undergoes further processing to generate the mature protein that is either anchored to membrane via a glycosylphosphatidylinositol moiety, or secreted. Many malignant cells secrete the encoded protein to evade immunosurveillance by NK cells. This gene is located in a cluster of multiple MHC class I-related genes on chromosome 6. [provided by RefSeq, Jul 2015]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:NKG2D ligand 2
HPRD
Source:NCBIAccessed: 11 August, 2015

Ontology:

What does this gene/protein do?
Show (11)
Pathways:What pathways are this gene/protein implicaed in?
Show (1)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 11 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Down-Regulation
  • Flow Cytometry
  • Ligands
  • Cell Membrane
  • Intracellular Signaling Peptides and Proteins
  • Oligonucleotide Array Sequence Analysis
  • p53 Protein
  • Pancreatic Cancer
  • HEK293 Cells
  • T-Lymphocytes
  • Carrier Proteins
  • Western Blotting
  • ras Proteins
  • GPI-Linked Proteins
  • Intercellular Signaling Peptides and Proteins
  • Cancer Gene Expression Regulation
  • RTPCR
  • p38 Mitogen-Activated Protein Kinases
  • Messenger RNA
  • Up-Regulation
  • HL-60 Cells
  • Receptors, IgG
  • Membrane Proteins
  • rho GTP-Binding Proteins
  • Gene Expression
  • Acute Myeloid Leukaemia
  • Immunotherapy
  • Natural Killer Cells
  • Receptors, Immunologic
  • Chromosome 6
  • Receptors, Natural Killer Cell
  • Histocompatibility Antigens Class I
  • Gene Expression Regulation
  • Cell Proliferation
  • Lymphocyte Activation
  • Melanoma
  • CD Antigens
  • Cytotoxicity, Immunologic
  • NK Cell Lectin-Like Receptor Subfamily K
  • Transfection
  • MicroRNAs
Tag cloud generated 11 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (3)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: ULBP2 (cancer-related)

Baragaño Raneros A, Martín-Palanco V, Fernandez AF, et al.
Methylation of NKG2D ligands contributes to immune system evasion in acute myeloid leukemia.
Genes Immun. 2015 Jan-Feb; 16(1):71-82 [PubMed] Related Publications
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.

Wennerberg E, Pfefferle A, Ekblad L, et al.
Human anaplastic thyroid carcinoma cells are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract NK cells.
Clin Cancer Res. 2014; 20(22):5733-44 [PubMed] Related Publications
PURPOSE: Anaplastic thyroid carcinoma (ATC) is one of the most aggressive forms of cancer with no curative therapies available. To date, strategies to target ATC by immunotherapy have not been evaluated. We investigated whether ATC would be a suitable target for natural killer (NK) cell-based immunotherapy.
EXPERIMENTAL DESIGN: We first established seven new cell lines from ATC tumors, three from papillary thyroid carcinoma tumors and analyzed them together with eight additional ATC cell lines. Cells were analyzed for sensitivity to lysis by NK cells and their ability to chemoattract and regulate the activity of NK cells. In addition, fresh tumor samples and peripheral blood from six patients with ATC were analyzed for NK cell infiltration and phenotype.
RESULTS: We observed that ATC cell lines are sensitive to lysis by ex vivo expanded NK cells and that the lysis was abrogated upon blockade of NKG2D. Sensitivity of thyroid cancer cell lines to NK cell-mediated lysis correlated with surface expression of UL16-binding protein 2 on tumor cells. Moreover, ATC cell lines produced high levels of CXCL10 and stimulated migration of expanded NK cells and ATC tumors were enriched for NK cells expressing the cognate chemokine receptor CXCR3. However, compared with NK cells in peripheral blood, ATC tumor-derived NK cells displayed a suppressed phenotype with a downregulated expression of NKG2D. In vitro, suppression of NK cell-mediated lysis and NKG2D expression by ATC cells was restored upon neutralization of prostaglandin-E2.
CONCLUSIONS: ATC cell lines are sensitive to NK cell-mediated lysis via ULBP2/5/6 and chemoattract CXCR3-positive NK cells. Patients with ATC may benefit from NK cell-based immunotherapy.

Song H, Park H, Park G, et al.
Corticotropin-releasing factor induces immune escape of cervical cancer cells by downregulation of NKG2D.
Oncol Rep. 2014; 32(1):425-30 [PubMed] Related Publications
Corticotropin-releasing factor (CRF), a coordinator of the body's responses to stress, is found in various cancer tissues and cell lines. However, the exact abilities of CRF to manipulate natural killer (NK) cells during immune response have not been studied. NKG2D is an activating receptor that is expressed on most NK and CD8+ T cells. MHC class I-related chain A (MICA) and UL16-binding protein (ULBP) 1, 2 and 3 are well-known ligands for NKG2D. In the present study, we reported our findings regarding the role of CRF in cervical cancer cell survival. Human cervical cancer cell line, HeLa cells, had significantly higher intracellular expression of UL16-binding protein 2 (ULBP2) following CRF treatment but had only slightly increased surface expression of ULBP2. Notably, MMPi (pan-metalloproteases inhibitor) blocked the release of ULBP2 molecules from the surface of HeLa cells. Furthermore, incubating NK cells with culture supernatants from CRF-treated HeLa cells, which contained soluble NKG2D ligand, reduced NK cell activity by decreasing surface expression of NKG2D. Collectively, downregulation of NKG2D by CRF-induced soluble NKG2D ligand provides a potential mechanism by which cervical cancer cells escape NKG2D-mediated attack under stress conditions.

Nanbakhsh A, Pochon C, Mallavialle A, et al.
c-Myc regulates expression of NKG2D ligands ULBP1/2/3 in AML and modulates their susceptibility to NK-mediated lysis.
Blood. 2014; 123(23):3585-95 [PubMed] Free Access to Full Article Related Publications
Cytarabine (cytosine arabinoside) is one of the most effective drugs for the treatment of patients diagnosed with acute myeloid leukemia (AML). Despite its efficiency against AML cells, the emergence of drug resistance due to prolonged chemotherapy in most patients is still a major obstacle. Several studies have shown that drug resistance mechanisms alter the sensitivity of leukemia cells to immune system effector cells. To investigate this phenomenon, parental acute myeloid cell lines, HL-60 and KG-1, were continuously exposed to increasing doses of cytarabine in order to establish equivalent resistant cell lines, HL-60(R) and KG-1(R). Our data indicate that cytarabine-resistant cells are more susceptible to natural killer (NK)-mediated cell lysis as compared with parental cytarabine-sensitive cells. The increased susceptibility correlates with the induction of UL-16 binding proteins (ULBP) 1/2/3 and NK group 2, member D (NKG2D) ligands on target cells by a mechanism involving c-Myc induction. More importantly, chromatin immunoprecipitation assay revealed that ULBP1/3 are direct targets of c-Myc. Using drug-resistant primary AML blasts as target cells, inhibition of c-Myc resulted in decreased expression of NKG2D ligands and the subsequent impairment of NK cell lysis. This study provides for the first time, the c-Myc dependent regulation of NKG2D ligands in AML.

Leung WH, Vong QP, Lin W, et al.
Modulation of NKG2D ligand expression and metastasis in tumors by spironolactone via RXRγ activation.
J Exp Med. 2013; 210(12):2675-92 [PubMed] Free Access to Full Article Related Publications
Tumor metastasis and lack of NKG2D ligand (NKG2DL) expression are associated with poor prognosis in patients with colon cancer. Here, we found that spironolactone (SPIR), an FDA-approved diuretic drug with a long-term safety profile, can up-regulate NKG2DL expression in multiple colon cancer cell lines by activating the ATM-Chk2-mediated checkpoint pathway, which in turn enhances tumor elimination by natural killer cells. SPIR can also up-regulate the expression of metastasis-suppressor genes TIMP2 and TIMP3, thereby reducing tumor cell invasiveness. Although SPIR is an aldosterone antagonist, its antitumor effects are independent of the mineralocorticoid receptor pathway. By screening the human nuclear hormone receptor siRNA library, we identified retinoid X receptor γ (RXRγ) instead as being indispensable for the antitumor functions of SPIR. Collectively, our results strongly support the use of SPIR or other RXRγ agonists with minimal side effects for colon cancer prevention and therapy.

Dambrauskas Z, Svensson H, Joshi M, et al.
Expression of major histocompatibility complex class I-related chain A/B (MICA/B) in pancreatic carcinoma.
Int J Oncol. 2014; 44(1):99-104 [PubMed] Related Publications
Major histocompatibility complex class I-related chain A and B (MICA/B) are two stress-inducible ligands that bind to the immunoreceptor NKG2D and play an important role in mediating cytotoxicity of NK and T cells. Release of MIC molecules from the cell surface is thought to constitute an immune escape mechanism of tumor cells and thus could be associated with more aggressive course of tumor growth. In this study, we investigated the expression of MICA/B in ductal pancreatic carcinoma and serum in relation to tumor stage, differentiation and survival. MICA/B expression in tumor tissues and sera from patients with pancreatic cancer were analyzed by immunohistochemical staining (IHC), western blotting and ELISA, respectively. MICA/B expression was present in 17 of 22 (77%) of the tumors but not in normal pancreatic ductal epithelial cells. Poorly differentiated tumors showed more pronounced MICA/B expression compared to differentiated tumors, but did not correlate significantly to other tumor characteristics. MICA/B-negative tumors displayed significantly lower incidence of lymph node metastases (p<0.01), and less mortality within 3 years following resection (p<0.02). In conclusion, tissue levels of MICA/B expression were elevated in pancreatic cancer cells without elevated levels in serum, despite well-recognized acute phase reactants in serum. Poorly differentiated tumors showed high MICA/B expression, which was related to extended tumor lymph node metastases and less frequent long-term survival.

Zhang B, Liu Y, Wang X, et al.
A novel recombinant Salmonella vaccine enhances the innate immunity of NK cells against acute myeloid leukaemia cells Kasumi-1 in vitro.
Cell Biol Int. 2013; 37(12):1320-9 [PubMed] Related Publications
Minor histocompatibility antigen HA-1-specific cytotoxic lymphocyte (CTL) clones have apparent anti-leukaemic efficacy, and the AML/ETO gene is a special fusion gene in leukaemic cells. Thus, we hypothesised that a vaccine targeting HA-1 and AML/ETO could stimulate NK cells to target leukaemia cells. Furthermore, we packaged the vaccine using attenuated Salmonella to enhance its immuno-activity. Expression of the NK cell-activating ligand ULBP2 was notably elevated upon packaging in a co-recombinant group. An AML/ETO single plasmid gave the weakest vaccine. The level of miR-182, which targets ULBP2, significantly decreased with increasing IFN-γ and granzyme B in a co-recombinant group. In summary, DNA vaccines including AML/ETO and HA-1 fragments significantly enhance the innate immunity of NK cells in vitro.

Lamb LS, Bowersock J, Dasgupta A, et al.
Engineered drug resistant γδ T cells kill glioblastoma cell lines during a chemotherapy challenge: a strategy for combining chemo- and immunotherapy.
PLoS One. 2013; 8(1):e51805 [PubMed] Free Access to Full Article Related Publications
Classical approaches to immunotherapy that show promise in some malignancies have generally been disappointing when applied to high-grade brain tumors such as glioblastoma multiforme (GBM). We recently showed that ex vivo expanded/activated γδ T cells recognize NKG2D ligands expressed on malignant glioma and are cytotoxic to glioma cell lines and primary GBM explants. In addition, γδ T cells extend survival and slow tumor progression when administered to immunodeficient mice with intracranial human glioma xenografts. We now show that temozolomide (TMZ), a principal chemotherapeutic agent used to treat GBM, increases the expression of stress-associated NKG2D ligands on TMZ-resistant glioma cells, potentially rendering them vulnerable to γδ T cell recognition and lysis. TMZ is also highly toxic to γδ T cells, however, and to overcome this cytotoxic effect γδ T cells were genetically modified using a lentiviral vector encoding the DNA repair enzyme O(6)-alkylguanine DNA alkyltransferase (AGT) from the O(6)-methylguanine methyltransferase (MGMT) cDNA, which confers resistance to TMZ. Genetic modification of γδ T cells did not alter their phenotype or their cytotoxicity against GBM target cells. Importantly, gene modified γδ T cells showed greater cytotoxicity to two TMZ resistant GBM cell lines, U373(TMZ-R) and SNB-19(TMZ-R) cells, in the presence of TMZ than unmodified cells, suggesting that TMZ exposed more receptors for γδ T cell-targeted lysis. Therefore, TMZ resistant γδ T cells can be generated without impairing their anti-tumor functions in the presence of high concentrations of TMZ. These results provide a mechanistic basis for combining chemotherapy and γδ T cell-based drug resistant cellular immunotherapy to treat GBM.

Lee EK, Jo DH, Kim JH, et al.
NK cell-associated antigen expression in retinoblastoma animal model.
Cancer Invest. 2013; 31(1):67-73 [PubMed] Related Publications
Natural killer (NK) cells are critical components of our immune system. Herein, we for the first time analyzed the expression and localization of the activating receptor NK cell lectin-like receptor gene 2D (NKG2D) ligands, HLA-G, MICA, MICA/B, and ULBP-2 in orthotopic transplantation models of retinoblastoma. Interestingly, HLA-G and MICA/B were expressed in retinoblastoma cell, whereas MICA and ULBP-2 were not detected. Moreover, HLA-G and MICA/B were primarily detected in proliferative area of the tumor periphery with high Ki-67 immunostaining. Our results suggest that NKG2D ligands are differentially expressed in retinoblastoma, which would play a crucial role in immunomodulation in retinoblastoma.

Jensen H, Hagemann-Jensen M, Lauridsen F, Skov S
Regulation of NKG2D-ligand cell surface expression by intracellular calcium after HDAC-inhibitor treatment.
Mol Immunol. 2013; 53(3):255-64 [PubMed] Related Publications
In this study we demonstrate that histone deacetylase (HDAC)-inhibitor mediated cell surface expression of the structural different NKG2D-ligands MICA/B and ULBP2 is calcium-dependent. Treatment with the calcium chelator EGTA inhibited constitutive as well as HDAC-inhibitor induced MICA/B and ULBP2 cell surface expression on melanoma cells and Jurkat T-cells. A NKG2D-dependent cytolytic assay and staining with a recombinant NKG2D-Fc fusion protein showed that calcium chelation impaired the functional ability of NKG2D-ligands induced by HDAC-inhibitor treatment. The HDAC-inhibitor induced cell surface expression of ULBP2, but not MICA/B, was sensitive to treatment calmidazolium and trifluoperazine, two agents known to block calcium signaling. siRNA-mediated knock-down of the calcium-regulated proteins calmodulin or calpain did however not affect NKG2D-ligand cell surface expression on Jurkat T-cells. We further show that secretion and cell surface binding of the calcium-regulating protein galectin-1 is enhanced upon HDAC-inhibitor treatment of melanoma cells. However, binding of galectin-1 to cell surface glycoproteins was not critical for constitutive or HDAC-inhibitor induced MICA/B and ULBP2 cell surface expression. We provide evidence that MICA/B and ULBP2 cell surface expression is controlled differently by calcium, which adds to the increasing perception that cell surface expression of MICA/B and ULBP2 is controlled by distinct signal transduction pathways.

Hu L, Cao D, Li Y, et al.
Resveratrol sensitized leukemia stem cell-like KG-1a cells to cytokine-induced killer cells-mediated cytolysis through NKG2D ligands and TRAIL receptors.
Cancer Biol Ther. 2012; 13(7):516-26 [PubMed] Related Publications
Human promyeloblastic leukemia KG-1a cells exhibit many characteristics similar to leukemia stem cells, which are resistant to chemotherapeutic drugs and hyposensitive to cytotoxic cells. Resveratrol (RES), as a member of plant polyphenols, has gained considerable attention due to its ability to prevent cancer from progressing. In this study, the potential of RES to sensitize KG-1a cells to cytolysis of cytokine-induced killer cells (CIKs) through NKG2D ligands and TNF-related apoptosis-inducing ligand (TRAIL) receptors were investigated. Twenty-five micromolars RES was found to inhibit approximately 50% of KG-1a cell growth and had the least growth-inhibition effect on peripheral blood mononuclear cells (PBMCs) after 24 h. Utilizing cytokines including interleukin-2 (IL-2) and interleukin-15 (IL-15) to activate PBMCs, we obtained substantial CD3 (+) CD56 (+) natural killer cell-like T lymphocytes that secreted cytokine interferon-γ (IFN-γ) and expressed NKG2D and TRAIL on their surfaces (i.e., cytokine-induced killer cells, CIKs). RES was shown to render KG-1a cells susceptible to CIK-mediated cytolysis estimated by LDH-release assay. This heightened sensitivity correlated with an increase in cell-surface expression of NKG2D ligands and death receptor 4 (DR4), coupled with a downregulation of cell-surface expression of decoy receptor 1 (DcR1) in KG-1a cells. Blocking NKG2D ligands or TRAIL with monoclonal antibodies could abrogate CIKs-mediated cytolysis. These results demonstrated that increased sensitivity of KG-1a cells, modulated by RES to alloreactive CIKs-mediated cytolysis is a phenomenon attributable to induced expression of NKG2D ligands and activation of TRAIL pathway. Thus, resveratrol combined with alloreactive CIKs merits clinical evaluation as a novel and effective immunotherapy strategy to eliminate residual leukemia stem cells.

Jimenez-Perez MI, Jave-Suarez LF, Ortiz-Lazareno PC, et al.
Cervical cancer cell lines expressing NKG2D-ligands are able to down-modulate the NKG2D receptor on NKL cells with functional implications.
BMC Immunol. 2012; 13:7 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Cervical cancer represents the third most commonly diagnosed cancer and the fourth leading cause of cancer-related deaths in women worldwide. Natural killer (NK) cells play an important role in the defense against viruses, intracellular bacteria and tumors. NKG2D, an activating receptor on NK cells, recognizes MHC class I chain-related molecules, such as MICA/B and members of the ULBP/RAET1 family. Tumor-derived soluble NKG2D-ligands have been shown to down-modulate the expression of NKG2D on NK cells. In addition to the down-modulation induced by soluble NKG2D-ligands, it has recently been described that persistent cell-cell contact can also down-modulate NKG2D expression. The goal of this study was to determine whether the NKG2D receptor is down-modulated by cell-cell contact with cervical cancer cells and whether this down-modulation might be associated with changes in NK cell activity.
RESULTS: We demonstrate that NKG2D expressed on NKL cells is down-modulated by direct cell contact with cervical cancer cell lines HeLa, SiHa, and C33A, but not with non-tumorigenic keratinocytes (HaCaT). Moreover, this down-modulation had functional implications. We found expression of NKG2D-ligands in all cervical cancer cell lines, but the patterns of ligand distribution were different in each cell line. Cervical cancer cell lines co-cultured with NKL cells or fresh NK cells induced a marked diminution of NKG2D expression on NKL cells. Additionally, the cytotoxic activity of NKL cells against K562 targets was compromised after co-culture with HeLa and SiHa cells, while co-culture with C33A increased the cytotoxic activity of the NKL cells.
CONCLUSIONS: Our results suggest that differential expression of NKG2D-ligands in cervical cancer cell lines might be associated with the down-modulation of NKG2D, as well as with changes in the cytotoxic activity of NKL cells after cell-cell contact with the tumor cells.

Heinemann A, Zhao F, Pechlivanis S, et al.
Tumor suppressive microRNAs miR-34a/c control cancer cell expression of ULBP2, a stress-induced ligand of the natural killer cell receptor NKG2D.
Cancer Res. 2012; 72(2):460-71 [PubMed] Related Publications
Malignant cells express ligands for the natural killer cell immunoreceptor NKG2D, which sensitizes to early recognition and elimination by cytotoxic lymphocytes and provides an innate barrier against tumor development. However, the mechanisms that control NKG2D ligand (NKG2DL) expression in tumor cells remain unknown. We recently identified the NKG2DL ULBP2 as strong prognostic marker in human malignant melanoma. Here, we provide evidence that the tumor-suppressive microRNAs (miRNA) miR-34a and miR-34c control ULBP2 expression. Reporter gene analyses revealed that both miRNAs directly targeted the 3'-untranslated region of ULBP2 mRNA and that levels of miR-34a inversely correlated with expression of ULBP2 surface molecules. Accordingly, treatment of cancer cells with miRNA inhibitors led to upregulation of ULBP2, whereas miR-34 mimics led to downregulation of ULBP2, diminishing tumor cell recognition by NK cells. Treatment with the small molecule inhibitor Nutlin-3a also decreased ULBP2 levels in a p53-dependent manner, which was due to a p53-mediated increase in cellular miR-34 levels. Taken together, our study shows that tumor-suppressive miR-34a and miR-34c act as ULBP2 repressors. These findings also implicate p53 in ULBP2 regulation, emphasizing the role of the specific NKG2DL in tumor immune surveillance.

Li H, Lakshmikanth T, Garofalo C, et al.
Pharmacological activation of p53 triggers anticancer innate immune response through induction of ULBP2.
Cell Cycle. 2011; 10(19):3346-58 [PubMed] Related Publications
Escape of tumor cells from cell-intrinsic barrier mediated by tumor suppressors and cell-extrinsic barrier mediated by the immune system is crucial for tumorigenesis. Growing evidence suggests that reactivation of tumor suppressor function or restoration of anticancer immunity is promising strategy for anticancer therapy due to their high potential to combat cancer. p53, a key tumor suppressor, represses tumorigenesis by eliciting growth arrest, apoptosis or senescence in cancer cells. Here, we unravel that, apart from these cell-autonomous effects, p53 activates the innate immune response against cancer cells. Our results show that pharmacological reactivation of p53 can stimulate the expression of ULPB2, a ligand for NK cell activating receptor NKG2D in human tumor cells of different origin, which enhance the susceptibility of tumor cells to NK cell-mediated killing. The molecular mechanism controlling ULPB2 expression by p53 is neither ATM/ATR- nor caspase-dependent. Using several approaches, we identified p53 as a direct transcriptional regulator of ULBP2 and found a p53 response element within ULBP2 gene, which confers the p53 regulation. Furthermore, we demonstrated that demethylation of p53-binding region within ULBP2 gene was required for p53-dependent induction of ULPB2, which can be achieved via repression of DNA methyltransferases (DNMTs) by p53. This molecular evidence for the direct control of immunosurveillance by p53 links tumor suppressor activation to innate immune stimuli and provides a possibility to integrate cell-extrinsic and -intrinsic defenses against tumorigenesis by pharmacological activation of p53, which may increase the probability to achieve a durable therapeutic success.

Bormann F, Sers C, Seliger B, et al.
Methylation-specific ligation detection reaction (msLDR): a new approach for multiplex evaluation of methylation patterns.
Mol Genet Genomics. 2011; 286(3-4):279-91 [PubMed] Related Publications
A new sensitive method for multiplex gene-specific methylation analysis was developed using a ligation-based approach combined with a TaqMan-based detection and readout employing universal reporter probes. The approach, termed methylation-specific Ligation Detection Reaction (msLDR), was applied to test 16 loci in 8 different colorectal cancer cells in parallel. These loci encode immune regulatory genes involved in T-cell and natural killer cell activation, whose silencing is associated with the development or progression of colorectal cancer. Parallel analysis of HLA-A, HLA-B, STAT1, B2M, LMP2, LMP7, PA28α, TAP1, TAP2, TAPBP, ULBP2 and ULBP3 by msLDR in eight colorectal cancer cell lines showed preferential methylation at the HLA-B, ULBP2 and ULBB3 loci, but not at the other loci. MsLDR was found to represent a suitable and sensitive method for the detection of distinct methylation patterns as validated by conventional bisulphite Sanger sequencing and COBRA analysis. Since gene silencing by epigenetic mechanisms plays a central role during transformation of a normal differentiated somatic cell into a cancer cell, characterization of the gene methylation status in tumours is a major topic not only in basic research, but also in clinical diagnostics. Due to a very simple workflow, msLDR is likely to be applicable to clinical samples and thus comprises a potential diagnostic tool for clinical purposes.

Jensen H, Andresen L, Nielsen J, et al.
Vesicular stomatitis virus infection promotes immune evasion by preventing NKG2D-ligand surface expression.
PLoS One. 2011; 6(8):e23023 [PubMed] Free Access to Full Article Related Publications
Vesicular stomatitis virus (VSV) has recently gained attention for its oncolytic ability in cancer treatment. Initially, we hypothesized that VSV infection could increase immune recognition of cancer cells through induction of the immune stimulatory NKG2D-ligands. Here we show that VSV infection leads to a robust induction of MICA mRNA expression, however the subsequent surface expression is potently hindered. Thus, VSV lines up with human cytomegalovirus (HCMV) and adenovirus, which actively subvert the immune system by negatively affecting NKG2D-ligand surface expression. VSV infection caused an active suppression of NKG2D-ligand surface expression, affecting both endogenous and histone deacetylase (HDAC)-inhibitor induced MICA, MICB and ULBP-2 expression. The classical immune escape mechanism of VSV (i.e., the M protein blockade of nucleocytoplasmic mRNA transport) was not involved, as the VSV mutant strain, VSV(ΔM51), which possess a defective M protein, prevented MICA surface expression similarly to wild-type VSV. The VSV mediated down modulation of NKG2D-ligand expression did not involve apoptosis. Constitutive expression of MICA bypassed the escape mechanism, suggesting that VSV affect NKG2D-ligand expression at an early post-transcriptional level. Our results show that VSV possess an escape mechanism, which could affect the immune recognition of VSV infected cancer cells. This may also have implications for immune recognition of cancer cells after combined treatment with VSV and chemotherapeutic drugs.

Textor S, Fiegler N, Arnold A, et al.
Human NK cells are alerted to induction of p53 in cancer cells by upregulation of the NKG2D ligands ULBP1 and ULBP2.
Cancer Res. 2011; 71(18):5998-6009 [PubMed] Related Publications
Natural killer (NK) cells are immune cells sensing and eliminating foreign, stressed, transformed, and senescent cells through specialized surface receptors, such as NKG2D, that interacts with several virus- or stress-inducible ligands, including ULBP1 and -2, which are expressed on target cell surfaces. For example, induction of DNA damage or cellular senescence pathways in tumor cells led to upregulation of NKG2D ligands that activate NK cells. Although, both pathways activate p53, the relationship of p53 activation to upregulation of NKG2D ligands has not been addressed. In this study, we report that induction of wild-type p53, but not mutant p53, strongly upregulated mRNA and cell surface expression of ULBP1 and -2, whereas expression of other NK cell ligands was not affected. We defined intronic p53-responsive elements in these two novel p53 target genes. Coculture of wild-type p53-induced human tumor cells with primary human NK cells enhanced NKG2D-dependent degranulation and IFN-γ production by NK cells. Accordingly, treatment of certain wild-type p53-expressing tumor cell lines with the p53-reactivating small molecular compound RITA resulted in upregulation of ULBP2 mRNA and cell surface protein expression. Taken together, our findings define the involvement of p53 in the regulation of specific NKG2D ligands that enhance NK cell-mediated target recognition. One implication of our work is that activating p53 after adoptive transfer of NK cells might constitute an effective combinatorial strategy of NK cell-based immunochemotherapy in cancers in which wild-type p53 function is preserved.

Chang YT, Wu CC, Shyr YM, et al.
Secretome-based identification of ULBP2 as a novel serum marker for pancreatic cancer detection.
PLoS One. 2011; 6(5):e20029 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: To discover novel markers for improving the efficacy of pancreatic cancer (PC) diagnosis, the secretome of two PC cell lines (BxPC-3 and MIA PaCa-2) was profiled. UL16 binding protein 2 (ULBP2), one of the proteins identified in the PC cell secretome, was selected for evaluation as a biomarker for PC detection because its mRNA level was also found to be significantly elevated in PC tissues.
METHODS: ULBP2 expression in PC tissues from 67 patients was studied by immunohistochemistry. ULBP2 serum levels in 154 PC patients and 142 healthy controls were measured by bead-based immunoassay, and the efficacy of serum ULBP2 for PC detection was compared with the widely used serological PC marker carbohydrate antigen 19-9 (CA 19-9).
RESULTS: Immunohistochemical analyses revealed an elevated expression of ULPB2 in PC tissues compared with adjacent non-cancerous tissues. Meanwhile, the serum levels of ULBP2 among all PC patients (n = 154) and in early-stage cancer patients were significantly higher than those in healthy controls (p<0.0001). The combination of ULBP2 and CA 19-9 outperformed each marker alone in distinguishing PC patients from healthy individuals. Importantly, an analysis of the area under receiver operating characteristic curves showed that ULBP2 was superior to CA 19-9 in discriminating patients with early-stage PC from healthy controls.
CONCLUSIONS: Collectively, our results indicate that ULBP2 may represent a novel and useful serum biomarker for pancreatic cancer primary screening.

Kim H, Kim SH, Kim MJ, et al.
EGFR inhibitors enhanced the susceptibility to NK cell-mediated lysis of lung cancer cells.
J Immunother. 2011; 34(4):372-81 [PubMed] Related Publications
As quercetin, which can inhibit phosphatidylinositol 3-kinase, nuclear factor-kappa B, and protein kinase C (PKC) pathways, induced expression of natural killer group 2, member D (NKG2D) ligands on cancer cells and made the cells sensitive to NK -cell-mediated killing; inhibition of epidermal growth factor receptor (EGFR) pathway might lead to induction of NKG2D ligands. In this study, it was investigated whether EGFR inhibitors, including erlotinib or gefitinib, could regulate expression of NKG2D ligands in various lung cancer cells including A549, NCI-H23, and SW-900. The EGFR inhibitors predominantly increased transcription and surface expression of ULBP1, and subsequently increased susceptibility of the cancer cells to NK-92 cells. When the selective inhibitors of nuclear factor-kappa B, phosphatidylinositol 3-kinase, mitogen-activated protein kinases, and PKC were treated to discriminate downstream signaling of EGFR pathway, expression of ULBP1 in the cancer cells was induced by inhibition of PKC. Treatment with phorbol 12-myristate 13-acetate restored the EGFR inhibitor-induced ULBP1 transcription. Binding activity to ULBP1 promoter region of AP-2α, which suggested as suppressor of expression of ULBP1, was decreased by treatment with EGFR inhibitors, and restored by pretreatment with phorbol 12-myristate 13-acetate in A549 and SW-900. Rottlerin, a PKCδ inhibitor, also decreased the binding activity of AP-2α in dose-dependent manner. This study suggests that EGFR inhibitors enhanced the susceptibility to NK cell-mediated lysis of lung cancer cells by induction of ULBP1 by inhibition of PKC pathway and therapeutic efficacy of EGFR inhibitors in lung cancer may be mediated in part by increased susceptibility to NK cell-mediated cytotoxicity.

Park MJ, Bae JH, Chung JS, et al.
Induction of NKG2D ligands and increased sensitivity of tumor cells to NK cell-mediated cytotoxicity by hematoporphyrin-based photodynamic therapy.
Immunol Invest. 2011; 40(4):367-82 [PubMed] Related Publications
Natural killer (NK) cells are important innate effector cells which can irradicate tumor cells through specific interactions between activating receptors on NK cells and their cognate ligands on cancer cells. Recently, it has been known that induction of activating NKG2D ligands including MHC class I chain-related (MIC) and UL16-binding protein (ULBP) families on tumor cells by various stresses makes them more susceptible to NK cell-mediated cytotoxicity. Therefore, it was investigated whether sublethal dose of hematoporphyrin-based photodynamic therapy (PDT) could up-regulate NKG2D ligands on tumor cells and increase the susceptibility of cancer cells against NK cells. Treatment with sublethal dose of hematoporphyrin-based PDT increased mRNA transcription and surface expression of ULBP1 and ULBP2 genes in SNU-1 human gastric tumor cell line and MICA/B, ULBP1, ULBP2 and ULBP3 genes in SW-900 human lung cancer cell line. These results were followed by increased susceptibility of cancer cells to NK cell-mediated cytotoxicity after sublethal PDT, which was abolished by addition of a blocking NKG2D mAb. Therefore, it could be suggested that the effect of hematoporphyrin-based PDT might be mediated in part by the increased susceptibility to NK cells via induction of NKG2D ligands on tumor cells, which survived after treatment with PDT.

Huang Y, Wang Y, Li Y, et al.
Role of sorafenib and sunitinib in the induction of expressions of NKG2D ligands in nasopharyngeal carcinoma with high expression of ABCG2.
J Cancer Res Clin Oncol. 2011; 137(5):829-37 [PubMed] Related Publications
BACKGROUND: Sorafenib and sunitinib are novel small molecule tyrosine kinase inhibitors with multiple targets on tumor cells, which have been demonstrated to be beneficial in the treatment of several carcinomas. Combining the usage of molecular targeted agents and adoptive cellular immunotherapy (ACI) against drug-resistant relapse nasopharyngeal carcinoma which had no standard therapeutic regimen was investigated by our research in order to study whether synergistic effects exist and related mechanisms.
METHODS: Human multidrug-resistant nasopharyngeal carcinoma cell line CNE2/DDP with high and low expressions of ABCG(2) (abbreviated to ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP) cells and NK cells were isolated by magnetic activated cell sorting, and the purity of isolated cells was detected by flow cytometry. mRNA expressions of drug-resistant gene ABCG(2), Bcl-2, MDR1, MRP and MGMT in ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP cells were detected by reverse transcription polymerase chain reaction (RT-PCR). Drug sensitivity of two kinds of cells to fluorouracil, cisplatin, vincristine, carboplatin, epirubicin, daunorubicin, paclitaxel, mitomycin, sorafenib, and sunitinib were detected by MTT assay. FCM was used to evaluate the expressions of NKG2D ligands (NKG2DLs,) on target cells before and after incubated with sorafenib and sunitinib. Subsequently, the cytotoxic sensitivity of incubated and un-incubated ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP cells to NK cells was measured by CytoTox 96(®) Non-Radioactive Cytotoxicity Assay.
RESULTS: The results revealed that target cells' cytotoxic sensitivity to natural killer (NK) cells increased in association with up-regulation of NKG2DLs on tumor cells after incubation with sorafenib and sunitinib. Furthermore, up-regulation in sunitinib group was much higher than in sorafenib group when it came to the expressions of NKG2DLs on tumor cells. For another, ABCG (2) (High) CNE2/DDP was much more sensitive to the regulation than ABCG (2) (Low) CNE2/DDP.
CONCLUSIONS: Our research revealed for the first time that sorafenib and sunitinib could up-regulate NKG2DLs on tumor cells resulting in markedly increased tumor cells cytotoxic sensitivity to NK cells, which suggested that combining usage of molecular targeted agents and ACI may result in great benefits in clinical practice for the therapy-resistant cases and drug-resistant relapse.

Serrano AE, Menares-Castillo E, Garrido-Tapia M, et al.
Interleukin 10 decreases MICA expression on melanoma cell surface.
Immunol Cell Biol. 2011; 89(3):447-57 [PubMed] Related Publications
Natural-killer group 2, member D (NKG2D) binds to a variety of ligands, including the major histocompatibility complex (MHC) class I chain-related proteins (MIC) and UL16-binding proteins (ULBP). It is regarded as a co-activating receptor on NK cells, having an important role in the cell-mediated immune response to tumours. We studied the influence of interleukin (IL)-10 on the regulation of MIC and ULBP expression on melanoma cells, and its effect on the cytotoxic function of NK cells in vitro. Here, we show that, in the presence of IL-10, FMS mel and BL mel cell lines decreased MICA and ULBP2 surface expression, whereas MHC class I did not change substantially on the cell surface. MICA mRNA levels decreased in IL-10-treated FMS and IL-10-transduced BL cell lines. Interestingly, we observed that MICB surface expression and its mRNA levels increased upon IL-10 treatment in a melanoma cell line. These changes in NKG2D ligands surface expression patterns owing to IL-10 treatment resulted in an effect on lysis susceptibility mediated by lymphocyte-activated killer cells, as tumour cell lines that displayed a higher decrease of MICA on their surface had lower levels of lysis. In addition, expression of CD107a was downregulated on the surface of NK cells following stimulation with IL-10-treated FMS cells. Our results suggest a novel function for IL-10 in the modulation of NKG2D ligand expression and in the control of cytotoxicity mediated by NKG2D/NKG2D ligand axis.

Bryant NL, Gillespie GY, Lopez RD, et al.
Preclinical evaluation of ex vivo expanded/activated γδ T cells for immunotherapy of glioblastoma multiforme.
J Neurooncol. 2011; 101(2):179-88 [PubMed] Related Publications
We have previously shown that expanded/activated γδ T cells from healthy donors are cytotoxic to GBM cell lines and primary GBM explants. In this report, we examined the therapeutic effect of intracranial infusion of expanded/activated γδ T cells on human minimal and established U251 tumor xenografts in athymic nude mice. Immunohistochemistry was used to determine the presence of NKG2D ligands on cell lines and tumors, and blocking studies were used to determine the effect of these ligands on γδ T cell recognition. Expanded/activated γδ T cells were prepared by 18-day culture in RPMI, human serum (HS), anti-CD2, IL-12, IFN-γ, and OKT-3. Anti-GBM activity of the cell product was assessed using in vitro cytotoxicity assays against the GBM cell line U251MG in suspension and in adherent culture. Ex vivo expanded/activated γδ T cells were of the effector/memory phenotype, expressed Th1 cytokines, and effectively killed U251 cells in vitro. Xenografts were prepared using a U251 cell line following transfection with a firefly luciferase gene to monitor tumor progression. Mice treated with γδ T cells showed slower progression of both new and established GBM xenografts versus mice that received vehicle only as determined by photon emission over time. Median survival was improved in all γδ T cell treated groups between 32 and 50 days by Kaplan-Meier analysis. U251 cells expressed ULBP-2 and ULBP-3, although blocking of these reduced in vitro cytotoxicity of γδ T cells to U251MG by only 33 and 25%, respectively. These studies show that expanded/activated γδ T cells can mediate killing of new or established GBM xenografts, reduce tumor progression, and constitute a potentially effective novel immunotherapeutic strategy against GBM.

Lu X, Ohata K, Kondo Y, et al.
Hydroxyurea upregulates NKG2D ligand expression in myeloid leukemia cells synergistically with valproic acid and potentially enhances susceptibility of leukemic cells to natural killer cell-mediated cytolysis.
Cancer Sci. 2010; 101(3):609-15 [PubMed] Related Publications
Valproic acid (VPA), a histone deacetylase inhibitor, upregulates NKG2D ligands (NKG2DLs) on some monocytic and lymphoid leukemic cells. However, its effect on myeloid leukemia cells and synergistic agents that can augment the effect of VPA remains unknown. Of the various myeloid cell lines examined, OUN-1, a chronic myelogenous leukemia cell line, showed the most prominent upregulation of MICA/B and ULBP2 in response to VPA. The NKG2DL upregulation was observed only in leukemic cells without apoptosis and the effect was abrogated by pretreatment of cells with caffeine, an inhibitor of ATM/ATR. Several activators of ATM/ATR were screened for their effect on NKG2DL expression, but only hydroxyurea (HU) efficiently upregulated both MICA/B and ULPB2 expression on the cell line. VPA and HU synergistically upregulated the NKG2DLs on OUN-1 cells as well as primary leukemic cells from some patients with acute myeloid leukemia. The upregulation of NKG2DLs by VPA and/or HU was associated with increased transcription of each NKG2DL gene. OUN-1 cells treated with VPA + HU were more susceptible to killing by natural killer (NK) cells than untreated cells and the enhanced cytotoxicity of NK cells was blocked by the treatment of NK cells with anti-NKG2D monoclonal antibodies. The same concentrations of VPA and HU did not affect the cytotoxicity of NK cells against OUN-1 cells. These data suggest that VPA and HU might enhance the NK cell-mediated antileukemia effect by increasing the susceptibility of myeloid leukemic cells to NK cells.

Fionda C, Soriani A, Malgarini G, et al.
Heat shock protein-90 inhibitors increase MHC class I-related chain A and B ligand expression on multiple myeloma cells and their ability to trigger NK cell degranulation.
J Immunol. 2009; 183(7):4385-94 [PubMed] Related Publications
Modulation of the host immune system represents a promising therapeutic approach against cancer, including multiple myeloma. Recent findings indicate that the NK group 2D (NKG2D)- and DNAX accessory molecule-1 (DNAM-1)-activating receptors play a prominent role in tumor recognition and elimination by cytotoxic lymphocytes, suggesting that the levels of NKG2D and DNAM-1 ligand expression on tumor cells may be a critical factor to improve the immune response against cancer. In this study, we tested the effect of 17-allylaminogeldanamycin and radicicol, drugs targeting the heat shock protein-90 (HSP-90) chaperone protein and displaying antimyeloma activity, on the expression of NKG2D and DNAM-1 ligands in human myeloma cell lines. We demonstrate that HSP-90 inhibitors are able to up-regulate both MHC class I chain-related (MIC) A and MICB protein surface and mRNA expression in human myeloma cell lines, without any significant effect on the basal expression of the DNAM-1 ligand poliovirus receptor CD155, or induction of nectin-2 and UL16-binding proteins. Activation of the transcription factor heat shock factor-1 by HSP-90 inhibitors is essential for the up-regulation of MICA/MICB expression and knockdown of heat shock factor-1 using small hairpin RNA interference blocks this effect. Moreover, in vitro and in vivo binding of heat shock factor-1 to MICA and MICB promoters indicates that it may enhance NKG2D ligand expression at the transcriptional level. Finally, exposure to HSP-90 inhibitors renders myeloma cells more efficient to activate NK cell degranulation and a blocking Ab specific for NKG2D significantly reduces this effect. Thus, these results provide evidence that targeting NKG2D ligands expression may be an additional mechanism supporting the antimyeloma activity of HSP-90 inhibitors and suggest their possible immunotherapeutic value.

Sers C, Kuner R, Falk CS, et al.
Down-regulation of HLA Class I and NKG2D ligands through a concerted action of MAPK and DNA methyltransferases in colorectal cancer cells.
Int J Cancer. 2009; 125(7):1626-39 [PubMed] Related Publications
Most malignant features of cancer cells are triggered by activated oncogenes and the loss of tumor suppressors due to mutation or epigenetic inactivation. It is still unclear, to what extend the escape of emerging cancer cells from recognition and elimination by the immune system is determined by similar mechanisms. We compared the transcriptomes of HCT116 colorectal cancer cells deficient in DNA methyltransferases (DNMTs) and of cells, in which the RAS pathway as the major growth-promoting signaling system is blocked by inhibition of MAPK. We identified the MHC Class I genes HLA-A1/A2 and the ULBP2 gene encoding 1 of the 8 known ligands of the activating NK receptor NKG2D among a cluster of immune genes up-regulated under the conditions of both DNMT-deficiency and MEK-inhibition. Bisulphite sequencing analyses of HCT116 with DNMT deficiency or after MEK-inhibition showed that de-methylation of the ULPB2 promoter correlated with its enhanced surface expression. The HLA-A promoters were not methylated indicating that components of the HLA assembly machinery were also suppressed in DNMT-deficient and MEK-inhibited cells. Increased HLA-A2 surface expression was correlated with enhanced recognition and lysis by A2-specific CTL. On the contrary, elevated ULBP2 expression was not reflected by enhanced recognition and lysis by NK cells. Cosuppression of HLA Class I and NKG2D ligands and genes encoding peptide transporters or proteasomal genes mediates a strong functional link between RAS activation, DNMT activity and disruption of the antigen presenting system controlling immune recognition in colorectal cancer cells.

López-Soto A, Folgueras AR, Seto E, Gonzalez S
HDAC3 represses the expression of NKG2D ligands ULBPs in epithelial tumour cells: potential implications for the immunosurveillance of cancer.
Oncogene. 2009; 28(25):2370-82 [PubMed] Related Publications
The expression of the NKG2D ligands on cancer cells leads to their recognition and elimination by host immune responses mediated by natural killer and T cells. UL16-binding proteins (ULBPs) are NKG2D ligands, which are scarcely expressed in epithelial tumours, favouring their evasion from the immune system. Herein, we investigated the epigenetic mechanisms underlying the repression of ULBPs in epithelial cancer cells. We show that ULBP1-3 expression is increased in tumour cells after exposure to the inhibitor of histone deacetylases (HDACs) trichostatin A (TSA), which enhances the natural killer cell-mediated cytotoxicity of HeLa cells. Our experiments showed that the transcription factor Sp3 is crucial in the activation of the ULBP1 promoter by TSA. Furthermore, by small interfering RNA-mediated knockdown and overexpression of HDAC1-3, we showed that HDAC3 is a repressor of ULBPs expression in epithelial cancer cells. Remarkably, TSA treatment caused the complete release of HDAC3 from the ULBP1-3 promoters. HDAC3 is recruited to the ULBP1 promoter through its interaction with Sp3 and TSA treatment interfered with this association. Together, we describe a new mechanism by which cancer cells may evade the immune response through the epigenetic modulation of the ULBPs expression and provide a model in which HDAC inhibitors may favour the elimination of transformed cells by increasing the immunogenicity of epithelial tumours.

Schwinn N, Vokhminova D, Sucker A, et al.
Interferon-gamma down-regulates NKG2D ligand expression and impairs the NKG2D-mediated cytolysis of MHC class I-deficient melanoma by natural killer cells.
Int J Cancer. 2009; 124(7):1594-604 [PubMed] Related Publications
NKG2D operates as an activating receptor on natural killer (NK) cells and costimulates the effector function of alphabeta CD8(+) T cells. Ligands of NKG2D, the MHC class I chain-related (MIC) and UL16 binding protein (ULBP) molecules, are expressed on a variety of human tumors, including melanoma. Recent studies in mice demonstrated that NKG2D mediates tumor immune surveillance, suggesting that antitumor immunity in humans could be enhanced by therapeutic manipulation of NKG2D ligand (NKG2DL) expression. However, signals and mechanisms regulating NKG2DL expression still need to be elucidated. Here, we asked whether the proinflammatory cytokine Interferon-gamma (IFN-gamma) affects NKG2DL expression in melanoma. Cell lines, established from MHC class I-negative and -positive melanoma metastases, predominantly expressed MICA and ULBP2 molecules on their surface. Upon IFN-gamma treatment, expression of MICA, in some cases, also of ULBP2 decreased. Besides melanoma, this observation was made also for glioma cells. Down-regulation of NKG2DL surface expression was dependent on the cytokine dose and the duration of treatment, but was neither due to an intracellular retention of the molecules nor to an increased shedding of ligands from the tumor cell surface. Instead, quantitative RT-PCR revealed a decrease of MICA-specific mRNA levels upon IFN-gamma treatment and siRNA experiments pointed to an involvement of STAT-1 in this process. Importantly, IFN-gamma-treated MHC class I-negative melanoma cells were less susceptible to NKG2D-mediated NK cell cytotoxicity. Our study suggests that IFN-gamma, by down-regulating ligand expression, might facilitate escape of MHC class I-negative melanoma cells from NKG2D-mediated killing by NK cells.

Nausch N, Cerwenka A
NKG2D ligands in tumor immunity.
Oncogene. 2008; 27(45):5944-58 [PubMed] Related Publications
The activating receptor NKG2D (natural-killer group 2, member D) and its ligands play an important role in the NK, gammadelta(+) and CD8(+) T-cell-mediated immune response to tumors. Ligands for NKG2D are rarely detectable on the surface of healthy cells and tissues, but are frequently expressed by tumor cell lines and in tumor tissues. It is evident that the expression levels of these ligands on target cells have to be tightly regulated to allow immune cell activation against tumors, but at the same time avoid destruction of healthy tissues. Importantly, it was recently discovered that another safeguard mechanism controlling activation via the receptor NKG2D exists. It was shown that NKG2D signaling is coupled to the IL-15 receptor pathway in a cell-specific manner suggesting that priming of NKG2D-mediated activation depends on the cellular microenvironment and the distinct cellular context. This review will provide a broad overview of our up-to-date knowledge of the NKG2D receptor and its ligands in the context of tumor immunology. Strategies to amplify NKG2D-mediated antitumor responses and counteract tumor immune escape mechanisms will be discussed.

Kohga K, Takehara T, Tatsumi T, et al.
Serum levels of soluble major histocompatibility complex (MHC) class I-related chain A in patients with chronic liver diseases and changes during transcatheter arterial embolization for hepatocellular carcinoma.
Cancer Sci. 2008; 99(8):1643-9 [PubMed] Related Publications
Soluble forms of major histocompatibility complex (MHC) class I-related chain A and B (MICA/B) are increased in the sera of patients with malignancy and impair the antitumor immune response by downregulating expression of their cognate immunoreceptor natural killer group 2, member D (NKG2D). Recently, soluble MICA/B were reported to appear even in some premalignant diseases, raising questions about the impact of soluble MICA/B produced from tumors on the expression of NKG2D. The present study examined soluble MICA/B in chronic liver disease and hepatocellular carcinoma (HCC) and their involvement in the immune-cell expression of NKG2D during transcatheter arterial embolization for HCC. The levels of soluble MICA/B were significantly higher in chronic liver disease and HCC patients than in healthy volunteers. The progression of liver disease and that of the tumor were independent determinants for soluble MICA/B levels. Immunohistochemistry revealed that MICA/B were expressed not only in HCC tissue but also on hepatocytes in cirrhotic livers. The transcatheter arterial embolization therapy significantly decreased serum levels of soluble MICA, but not soluble MICB, and increased the NKG2D expression on natural killer cells and CD8-positive T cells; there was an inverse correlation between changes in soluble MICA levels and in NKG2D expression. In conclusion, although soluble MICA/B are produced from both HCC and premalignant cirrhotic livers, therapeutic intervention for HCC can reduce the levels of soluble MICA and thereby upregulate the expression of NKG2D. Cancer therapy may have a beneficial effect on NKG2D-mediated antitumor immunity.

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