Transcriptional regulation of MICA and MICB: a novel polymorphism in MICB promoter alters transcriptional regulation by Sp1

The role of hyperthermia in the treatment of tumor

Despite recent advancements in the diagnosis and treatment options for cancer, it remains one of the most serious threats to health. Hyperthermia (HT) has emerged as a highly promising area of research due to its safety and cost-effectiveness. Currently, based on temperature, HT can be categorized into thermal ablation and mild hyperthermia. Thermal ablation involves raising the temperature within the tumor to over 60°C, resulting in direct necrosis in the central region of the tumor. In contrast, mild hyperthermia operates at relatively lower temperatures, typically in the range of 41-45°C, to induce damage to tumor cells. Furthermore, HT also serves as an immune adjuvant strategy in radiotherapy, chemotherapy, and immunotherapy, enhancing the effectiveness of radiotherapy, increasing the uptake of chemotherapy drugs, and reprogramming the tumor microenvironment through the induction of immunogenic cell death, thereby promoting the recruitment of endogenous immune cells. This article reviews the current status and development of hyperthermia, outlines potential mechanisms by which hyperthermia inhibits tumors, describes clinical trial attempts combining hyperthermia with radiotherapy, chemotherapy, and immunotherapy, and discusses the relationship between nanoparticles and hyperthermia.

Characterisation of RAET1E/ULBP4 exon 4 and 3' untranslated region genetic architecture reveals further diversity and allelic polymorphism

NKG2D is a natural killer cell activating receptor recognising ligands on infected or tumorigenic cells, leading to their cytolysis. There are eight known genes encoding NKG2D ligands: MICA, MICB and ULBP1-6. MICA and MICB are highly polymorphic and well characterised, whilst ULBP ligands are less polymorphic and the functional implication of their diversity is not well understood. Using International HLA and Immunogenetics Workshop (IHIW) cell line DNA, we previously characterised alleles of the RAET1E gene (encoding ULBP4 proteins), including the 5' UTR promoter region and exons 1-3. We found 11 promoter haplotypes associating with alleles based on exons 1-3, revealing 19 alleles overall. The current study extends this analysis using 87 individual DNA samples from IHIW cell lines or cord blood to include RAET1E exon 4 and the 3' UTR, as polymorphism in these regions have not been previously investigated. We found two novel exon 4 polymorphisms encoding amino acid substitutions altering the transmembrane domain. An amino acid substitution at residue 233 was unique to the RAET1E*008 allele whereas the substitution at residue 237 was shared between groups of alleles. Additionally, four haplotypes were found based on 3' UTR sequences, which were unique to certain alleles or shared with allele groups based on exons 1-4 polymorphisms. Furthermore, putative microRNAs were identified that may interact with these polymorphic sites, repressing transcription and potentially affecting expression levels.

Immune evasion by proteolytic shedding of natural killer group 2, member D ligands in Helicobacter pylori infection

Background

Helicobacter pylori (H. pylori) uses various strategies that attenuate mucosal immunity to ensure its persistence in the stomach. We recently found evidence that H. pylori might modulate the natural killer group 2, member 2 (NKG2D) system. The NKG2D receptor and its ligands are a major activation system of natural killer and cytotoxic T cells, which are important for mucosal immunity and tumor immunosurveillance. The NKG2D system allows recognition and elimination of infected and transformed cells, however viruses and cancers often subvert its activation. Here we aimed to identify a potential evasion of the NKG2D system in H. pylori infection.

Methods

We analyzed expression of NKG2D system genes in gastric tissues of H. pylori gastritis and gastric cancer patients, and performed cell-culture based infection experiments using H. pylori isogenic mutants and epithelial and NK cell lines.

Results

In biopsies of H. pylori gastritis patients, NKG2D receptor expression was reduced while NKG2D ligands accumulated in the lamina propria, suggesting NKG2D evasion. In vitro, H. pylori induced the transcription and proteolytic shedding of NKG2D ligands in stomach epithelial cells, and these effects were associated with specific H. pylori virulence factors. The H. pylori-driven release of soluble NKG2D ligands reduced the immunogenic visibility of infected cells and attenuated the cytotoxic activity of effector immune cells, specifically the anti-tumor activity of NK cells.

Conclusion

H. pylori manipulates the NKG2D system. This so far unrecognized strategy of immune evasion by H. pylori could potentially facilitate chronic bacterial persistence and might also promote stomach cancer development by allowing transformed cells to escape immune recognition and grow unimpeded to overt malignancy.

The role of enhancers in psoriasis and atopic dermatitis

Regulatory elements, particularly enhancers, play a crucial role in disease susceptibility and progression. Enhancers are DNA sequences that activate gene expression and can be affected by epigenetic modifications, interactions with transcription factors (TFs) or changes to the enhancer DNA sequence itself. Altered enhancer activity impacts gene expression and contributes to disease. In this review, we define enhancers and the experimental techniques used to identify and characterize them. We also discuss recent studies that examine how enhancers contribute to atopic dermatitis (AD) and psoriasis. Articles in the PubMed database were identified (from 1 January 2010 to 28 February 2023) that were relevant to enhancer variants, enhancer-associated TFs and enhancer histone modifications in psoriasis or AD. Most enhancers associated with these conditions regulate genes affecting epidermal homeostasis or immune function. These discoveries present potential therapeutic targets to complement existing treatment options for AD and psoriasis.

Major Histocompatibility Complex Class I Chain-Related A and B (MICA and MICB) Gene, Allele, and Haplotype Associations With Dengue Infections in Ethnic Thais

BACKGROUND

Major histocompatibility complex class I chain-related (MIC) A and B (MICA and MICB) are polymorphic stress molecules recognized by natural killer cells. This study was performed to analyze MIC gene profiles in hospitalized Thai children with acute dengue illness.

METHODS

MIC allele profiles were determined in a discovery cohort of patients with dengue fever or dengue hemorrhagic fever (DHF) (n = 166) and controls (n = 149). A replication cohort of patients with dengue (n = 222) was used to confirm specific MICB associations with disease.

RESULTS

MICA*045 and MICB*004 associated with susceptibility to DHF in secondary dengue virus (DENV) infections (odds ratio [OR], 3.22; [95% confidence interval (CI), 1.18-8.84] and 1.99 [1.07-2.13], respectively), and MICB*002 with protection from DHF in secondary DENV infections (OR, 0.41; 95% CI, .21-.68). The protective effect of MICB*002 against secondary DHF was confirmed in the replication cohort (OR, 0.43; 95% CI, .22-.82) and was stronger when MICB*002 is present in individuals also carrying HLA-B*18, B*40, and B*44 alleles which form the B44 supertype of functionally related alleles (0.29, 95% CI, .14-.60).

CONCLUSIONS

Given that MICB*002 is a low expresser of soluble proteins, these data indicate that surface expression of MICB*002 with B44 supertype alleles on DENV-infected cells confer a protective advantage in controlling DENV infection using natural killer cells.

High-Throughput MICA/B Genotyping of Over Two Million Samples: Workflow and Allele Frequencies

MICA and MICB are ligands of the NKG2D receptor and thereby influence NK and T cell activity. MICA/B gene polymorphisms, expression levels and the amount of soluble MICA/B in the serum have been linked to autoimmune diseases, infections, and cancer. In hematopoietic stem cell transplantation, MICA matching between donor and patient has been correlated with reduced acute and chronic graft-vs.-host disease and improved survival. Hence, we developed an extremely cost-efficient high-throughput workflow for genotyping MICA/B for newly registered potential stem cell donors. Since mid-2017, we have genotyped over two million samples using NGS amplicon sequencing for MICA/B exons 2–5. In donors of German origin, MICA*008 is the most common MICA allele with a frequency of 42.3%. It is followed by MICA*002 (11.7%) and MICA*009 (8.8%). The three most common MICB alleles are MICB*005 (43.9%), MICB*004 (21.7%), and MICB*002 (18.9%). In general, MICB is less diverse than MICA and only 6 alleles, instead of 15, account for a cumulative allele frequency of 99.5%. In 0.5% of the samples we observed at least one allele of MICA or MICB which has so far not been reported to the IPD/IMGT-HLA database. By providing MICA/B typed voluntary donors, clinicians become empowered to include MICA/B into their donor selection process to further improve unrelated hematopoietic stem cell transplantation.

Diversity and characterisation of polymorphic 3' untranslated region haplotypes of MICA and MICB genes

MICA and MICB genes encode ligands that interact with the natural killer (NK) cell activating receptor, NKG2D. These ligands display a highly polymorphic allelic repertoire, although the true functional significance of this polymorphism remains elusive. We previously reported additional polymorphism in the 5' untranslated region (UTR) proximal promoter region of these genes by sequencing international histocompatibility workshop (IHW) cell line DNA promoter and coding regions. The present study extends this analysis by further characterising the 3'UTR region of the same IHW reference panel to achieve a more complete understanding of MICA and MICB haplotype diversity and possible functional relevance. We found 17 extended MICA haplotypes encompassing the coding region and 3'UTR, including four novel haplotypes identified in IHW cell line DNA. This increased to 21 when also considering the 5'UTR proximal promoter region. Analysis of the MICB 3'UTR revealed two novel sequences in cell lines KLO and WIN designated MICB-UTR8 and UTR9, respectively. A total of 11 MICB haplotypes were identified in this study and five were unique. The present study, characterising MICA/B 3'UTR polymorphism utilising IHW reference cell lines, could be useful for future studies investigating the role of microRNA in post-transcriptional repression of gene expression and for immunotherapy strategies to combat cancer progression.

Positive association between MIC gene polymorphism and tuberculosis in Chinese population

The disease progression and morbidity of tuberculosis (TB) infections are determined by virulence of the micro-organism, host genetic factors and environmental factors. The highly polymorphic MHC class I chain-related gene (MIC) could serve as a potential host genetic candidate. To investigate the association of MIC polymorphism with TB infection, 124 patients and 191 ethnically matched controls from Hunan province, Southern China, were genotyped for the MIC polymorphism using polymerase chain reaction-sequence specific priming and sequencing-based typing. The results showed that allele frequencies of MIC-sequence and MICA-STR were different in TB patients in comparison to normal controls (both P < 0.05). MICA-A4 and MICA*012:01 alleles were positive associated (OR = 2.42, 95% CI: 1.69-3.87; OR = 3.41, 95% CI: 2.19-5.33, respectively, both P_c < 0.05) while MICA -A5 were inversely associated (OR = 0.59, 95%CI: 0.41-0.94, P_c < 0.05) with TB. Homozygote MICA*012:01/012:01 was observed to have significant risk effects on TB (OR = 4.76, 95% CI: 1.94-11.69, P_c0000-0001-5151-1853 < 0.05). Additionally, MICB*008 allele conduct a significant risk effect for TB (OR = 3.17, 95%CI: 1.80-5.61, P_c < 0.05). All the data showed that MIC polymorphism was associated with the variable susceptibility to TB in Chinese population.

Transcription of the NKG2D ligand MICA is suppressed by the IRE1/XBP1 pathway of the unfolded protein response through the regulation of E2F1

The unfolded protein response (UPR) is an adaptive signaling pathway activated in response to endoplasmic reticulum (ER) stress. The effectors of the UPR are potent transcription activators; however, some genes are suppressed by ER stress at the mRNA level. The mechanisms underlying UPR-mediated gene suppression are less known. Exploration of the effect of UPR on NK cells ligand expression found that the transcription of NK group 2 member D (NKG2D) ligand major histocompatibility complex class I polypeptide-related sequence A/B (MICA/B) is suppressed by the inositol-requiring enzyme 1 (IRE1)/X-box binding protein 1 (XBP1) pathway of the UPR. Deletion of IRE1 or XBP1 was sufficient to promote mRNA and surface levels of MICA. Accordingly, NKG2D played a greater role in the killing of IRE1/XBP1 knockout target cells. Analysis of effectors downstream to XBP1s identified E2F transcription factor 1 (E2F1) as linking UPR and MICA transcription. The inverse correlation between XBP1 and E2F1 or MICA expression was corroborated in RNA-Seq analysis of 470 primary melanoma tumors. While mechanisms that connect XBP1 to E2F1 are not fully understood, we implicate a few microRNA molecules that are modulated by ER stress and possess dual suppression of E2F1 and MICA. Because of the importance of E2F1 and MICA in cancer progression and recognition, these observations could be exploited for cancer therapy by manipulating the UPR in tumor cells.-Obiedat, A., Seidel, E., Mahameed, M., Berhani, O., Tsukerman, P., Voutetakis, K., Chatziioannou, A., McMahon, M., Avril, T., Chevet, E., Mandelboim, O., Tirosh, B. Transcription of the NKG2D ligand MICA is suppressed by the IRE1/XBP1 pathway of the unfolded protein response through the regulation of E2F1.

NKG2D Ligands-Critical Targets for Cancer Immune Escape and Therapy

DNA damage, oncogene activation and excessive proliferation, chromatin modulations or oxidative stress are all important hallmarks of cancer. Interestingly, all of these abnormalities also induce a cellular stress response. By upregulating “stress-induced ligands,” damaged or transformed cells can be recognized by immune cells and cleared. The human genome encodes eight functional “stress-induced ligands”: MICA, MICB, and ULBP1-6. All of them are recognized by a single receptor, NKG2D, which is expressed on natural killer (NK) cells, cytotoxic T cells and other T cell subsets. The NKG2D ligand/NKG2D-axis is well-recognized as an important mediator of anti-tumor activity; however, patient data about the role of NKG2D ligands in immune surveillance and escape appears conflicting. As these ligands are often actively transcribed, tumor cells are urged to manipulate the expression of these ligands on post-transcriptional or post-translational level. Although our knowledge on the regulation of NKG2D ligand expression remains fragmentary, research of the past years revealed multiple cellular mechanisms that are adopted by tumor cells to reduce the expression of “stress-induced ligands” and therefore escape immune recognition. Here, we review the post-transcriptional and post-translational mechanisms by which NKG2D ligands are modulated in cancer cells and their impact on patient prognosis.We discuss controversies and approaches to apply our understanding of the NKG2D ligand/NKG2D-axis for cancer therapy.

Genetic polymorphism analysis of MICB gene in Jing ethnic minority of Southern China

In the present study, the polymorphism in the 5'-upstream regulation region (5'-URR), coding region (exons 2-4), and the 3'-untranslated region (3'-UTR) of MICB gene were investigated for 150 healthy unrelated Jing individuals in Guangxi Zhuang Autonomous Region, by using PCR-SBT method. A total of 14 variation sites in the 5'-URR, 9 in coding region, and 6 in the 3'-UTR were detected in the Jing population. The MICB gene seems to present two different lineages showing functional variations mainly in nucleotides of the promoter region. Nineteen different MICB extended haplotypes (EHs) encompassing the 5'-URR, exons 2-4, and 3'-UTR were found in this population, and the most frequent was EH2 (20.33%). The findings here are of importance for future studies on the potential role of regulation region of MICB gene in disease association, transplantation, viral infection, and tumor progression among Jing population.

Functional Characterisation and Analysis of the Soluble NKG2D Ligand Repertoire Detected in Umbilical Cord Blood Plasma

We previously reported that cord blood plasma (CBP) contains significantly more soluble NKG2D ligands (sNKG2DLs), such as sMICB and sULBP1, than healthy adult plasma. Viral infection or malignant transformation upregulates expression of NKG2D ligand on affected cells, leading to NK group 2, member D (NKG2D)-mediated natural killer (NK) cell lysis. Conversely, sNKG2DL engagement of NKG2D decreases NK cell cytotoxicity leading to viral or tumour immune escape. We hypothesised that sNKG2DLs detected in CBP may represent an additional fetal–maternal tolerance mechanism. To further understand the role of sNKG2DL in pregnancy and individual contributions of the various ligand types, we carried out functional analysis using 181 CBP samples. To test the ability of CBP to suppress the function of NK cells in vitro, we measured expression of NKG2D, CD107a, and IFN-γ in NK cells from control donors after exposure to 181 individual CBP samples and characterised the sMICA, sMICB, and sULBP1 content of each one. Furthermore, to detect possible allelic differences between samples that may also affect function, we carried out umbilical cord blood typing for MHC class I-related chain A (MICA) and MHC class I-related chain B (MICB) coding and promoter allelic types. Strongest functional correlations related to increasing concentration of exosomal sULBP1, which was present in all CBP samples tested. In addition, common MICB alleles, such as MICB*005:02, resulted in increased concentration of sMICB. Interestingly, MICB*005:02 uniquely associated with eight different promoter types. Among promoter polymorphisms, P2 resulted in the highest expression of sMICB and P9 the least and was confirmed using luciferase reporter assays. Higher levels of sMICB associated with lower IFN-γ production, indicating that sMICB also suppressed NK cell function. We also examined the MICA functional dimorphism encoding methionine (met) or valine (val) at residue 129 associated with strong or weak NKG2D binding, respectively. Most sMICA associated with val/val, some with met/val but none with met/met and, counter-intuitively, the presence of sMICA in CBP increased NK cell cytotoxicity. We propose a model for fetal–maternal tolerance, whereby NK cell activity is limited by sULBP1 and sMICB in CBP. The release of 129val sMICA with weak NKG2D signalling may reduce the overall net suppressive signal and break tolerance thus allowing fetal NK cells to overcome immunological threats in utero.

The Donor Major Histocompatibility Complex Class I Chain-Related Molecule A Allele rs2596538 G Predicts Cytomegalovirus Viremia in Kidney Transplant Recipients

The interaction of major histocompatibility complex class I chain-related protein A (MICA) and its cognate activating receptor natural killer (NK) group 2 member D (NKG2D) receptor plays a significant role in viral immune control. In the context of kidney transplantation (KTx), cytomegalovirus (CMV) frequently causes severe complications. Hypothesizing that functional polymorphisms of the MICA/NKG2D axis might affect antiviral NK and T cell responses to CMV, we explored the association of the MICA-129 Met/Val single nucleotide polymorphism (SNP) (affecting the binding affinity of MICA with the NKG2D receptor), the MICA rs2596538 G/A SNP (influencing MICA transcription), and the NKG2D rs1049174 G/C SNP (determining the cytotoxic potential of effector cells) with the clinical outcome of CMV during the first year after KTx in a cohort of 181 kidney donor-recipients pairs. Univariate analyses identified the donor MICA rs2596538 G allele status as a protective prognostic determinant for CMV disease. In addition to the well-known prognostic factors CMV high-risk sero-status of patients and the application of lymphocyte-depleting drugs, the donor MICA rs2596538 G allele carrier status was confirmed by multivariate analyses as novel-independent factor predicting the development of CMV infection/disease during the first year after KTx. The results of our study emphasize the clinical importance of the MICA/NKG2D axis in CMV control in KTx and point out that the potential MICA transcription in the donor allograft is of clinically relevant importance for CMV immune control in this allogeneic situation. Furthermore, they provide substantial evidence that the donor MICA rs2596538 G allele carrier status is a promising genetic marker predicting CMV viremia after KTx. Thus, in the kidney transplant setting, donor MICA rs2596538 G may help to allow the future development of personal CMV approaches within a genetically predisposed patient cohort.

NKG2D and Its Ligands: "One for All, All for One"

The activating receptor NKG2D is peculiar in its capability to bind to numerous and highly diversified MHC class I-like self-molecules. These ligands are poorly expressed on normal cells but can be induced on damaged, transformed or infected cells, with the final NKG2D ligand expression resulting from multiple levels of regulation. Although redundant molecular mechanisms can converge in the regulation of all NKG2D ligands, different stimuli can induce specific cellular responses, leading to the expression of one or few ligands. A large body of evidence demonstrates that NK cell activation can be triggered by different NKG2D ligands, often expressed on the same cell, suggesting a functional redundancy of these molecules. However, since a number of evasion mechanisms can reduce membrane expression of these molecules both on virus-infected and tumor cells, the co-expression of different ligands and/or the presence of allelic forms of the same ligand guarantee NKG2D activation in various stressful conditions and cell contexts. Noteworthy, NKG2D ligands can differ in their ability to down-modulate NKG2D membrane expression in human NK cells supporting the idea that NKG2D transduces different signals upon binding various ligands. Moreover, whether proteolytically shed and exosome-associated soluble NKG2D ligands share with their membrane-bound counterparts the same ability to induce NKG2D-mediated signaling is still a matter of debate. Here, we will review recent studies on the NKG2D/NKG2D ligand biology to summarize and discuss the redundancy and/or diversity in ligand expression, regulation, and receptor specificity.

The association between MICA/MICB polymorphism and respiratory syncytial virus infection in children

MICA/MICB gene polymorphisms are related to several cancers and infectious diseases, but there are no reports on the association between MICA/MICB gene polymorphisms and respiratory syncytial virus (RSV) infection. To clarify the association between MICA/MICB gene polymorphisms and infection of RSV in children, we collected fresh blood samples from paediatric patients with and without pneumonia after RSV infection. The MICA/MICB alleles were characterized by PCR sequence-specific primers (PCR-SSP) and PCR sequence-based genotyping (PCR-SBT), and then, the frequency of the MICA/MICB alleles and haplotypes was calculated. The results showed that the frequencies of MICA*002:01 and MICA-A9 in RSV-infected patients were significantly lower than in controls (9% vs. 20%, pc = 0.04). The allele frequency of MICA*002:01 in pneumonia patients (8%) and nonpneumonia patients (9%) was significantly lower than in controls (20%, pc = 0.02). MICA*002:01-MICB*008(Δrel = 0.616), MICA*009-MICB*016 (Δrel = 0.506), and MICA*045-MICB*014 (Δrel = 0.700) showed linkage disequilibrium in patients infected with RSV. The haplotype frequency of MICA*002:01-MICB*005:02 in RSV-infected patients was significantly lower than in controls (10% vs. 16%, pc = 0.033). In conclusion, allele MICA*002:01/A9 and haplotype MICA*002:01-MICB*005:02 were negatively associated with RSV respiratory tract infections.

The TGF-β-induced up-regulation of NKG2DLs requires AKT/GSK-3β-mediated stabilization of SP1

Natural killer (NK) cells play an important role in preventing cancer development. NK group 2 member D (NKG2D) is an activating receptor expressed in the membrane of NK cells. Tumour cells expressing NKG2DL become susceptible to an immune‐dependent rejection mainly mediated by NK cells. The paradoxical roles of transforming growth factor beta (TGF‐β) in regulation of NKG2DL are presented in many studies, but the mechanism is unclear. In this study, we showed that TGF‐β up‐regulated the expression of NKG2DLs in both PC3 and HepG2 cells. The up‐regulation of NKG2DLs was characterized by increasing the expression of UL16‐binding proteins (ULBPs) 1 and 2. TGF‐β treatment also increased the expression of transcription factor SP1. Knockdown of SP1 significantly attenuated TGF‐β‐induced up‐regulation of NKG2DLs in PC3 and HepG2 cells, suggesting that SP1 plays a key role in TGF‐β‐induced up‐regulation of NKG2DLs. TGF‐β treatment rapidly increased SP1 protein expression while not mRNA level. It might be due to that TGF‐β can elevate SP1 stability by activating PI3K/AKT signalling pathway, subsequently inhibiting GSK‐3β activity and decreasing the association between SP1 and GSK‐3β. Knockdown of GSK‐3β further verified our findings. Taken together, these results revealed that AKT/GSK‐3β‐mediated stabilization of SP1 is required for TGF‐β induced up‐regulation of NKG2DLs. Our study provided valuable evidence for exploring the tumour immune modulation function of TGF‐β.

Polymorphism rs3828903 within MICB Is Associated with Susceptibility to Systemic Lupus Erythematosus in a Northern Han Chinese Population

Objectives. The variant rs3828903 within MICB, a nonclassical MHC class I chain-related gene, was detected to contribute to systemic lupus erythematosus (SLE) in a Caucasian population. This study aimed to investigate the association in a northern Han Chinese population. Methods. We recruited 1077 SLE patients and 793 controls for analysis. rs3828903 was genotyped by TaqMan allele discrimination assay. Using the public databases, its functional annotations and gene differential expression analysis of MICB were evaluated. Results. Significant association between the allele G of rs3828903 and risk susceptibility to SLE was observed after adjusting for sex and age (P = 1.87 × 10⁻²). In silico analyses predicted a higher affinity to transcription factors for allele G (risk) and cis-expression quantitative trait loci (cis-eQTL) effects of rs3828903 in multiple tissues (P ranging from 2.79 × 10⁻⁶ to 6.27 × 10⁻³⁸). Furthermore, higher mRNA expressions of MICB were observed in B cells, monocytes, and renal biopsies from SLE patients compared to controls. Conclusion. An association between rs3828903 and susceptibility to SLE has been detected in a Chinese population. This together with the functional annotations of rs3828903 converts MICB into a main candidate in the pathogenesis of SLE.

Reversal of epigenetic silencing of MHC class I chain-related protein A and B improves immune recognition of Merkel cell carcinoma

Merkel cell carcinoma (MCC) is a virally associated cancer characterized by its aggressive behavior and strong immunogenicity. Both viral infection and malignant transformation induce expression of MHC class I chain-related protein (MIC) A and B, which signal stress to cells of the immune system via Natural Killer group 2D (NKG2D) resulting in elimination of target cells. However, despite transformation and the continued presence of virally-encoded proteins, MICs are only expressed in a minority of MCC tumors in situ and are completely absent on MCC cell lines in vitro. This lack of MIC expression was due to epigenetic silencing via MIC promoter hypo-acetylation; indeed, MIC expression was re-induced by pharmacological inhibition of histone deacetylases (HDACs) both in vitro and in vivo. This re-induction of MICs rendered MCC cells more sensitive to immune-mediated lysis. Thus, epigenetic silencing of MICs is an important immune escape mechanism of MCCs.

Further diversity of the 5' promoter region of the MHC class I-related chain B gene

We have now found a total of 15 individual MICB promoter sequences, varying by combination of 18 polymorphic positions within the MICB minimal promoter sequence. Sequence-based typing and cloning characterized the three new 5' promoter sequences as MICB-P13, MICB-P14 and MICB-P15.

The tertiary prevention of hepatocellular carcinoma in chronic hepatitis C patients

BACKGROUND AND AIM

Pegylated interferon-alpha plus ribavirin combination (PegIFN/RBV) therapy possesses positive effect in the secondary prevention of hepatocellular carcinoma (HCC) in chronic hepatitis C (CHC) patients. The current study aimed to assess its efficacy in the tertiary prevention and to validate the performance of the MHC class I polypeptide-related chain A (MICA) level in the prediction of hepatocellular carcinoma (HCC) recurrence.

METHODS

A multi-center study enrolling 105 consecutive HCC patients post curative therapies were prospectively recruited. The primary outcome measurement was recurrence of HCC.

RESULTS

The mean observational period was 52.7 months (range = 3.9-121.5 months). Fifty-six (53.3%) patients achieved sustained virological response (SVR). After completion of treatment, 43 (41.0%) patients developed HCC recurrence, and 24 (55.8%) of them had their recurrence within 6 months after completion of therapy. Thirty-three (76.7%) of the patients with HCC recurrence were of de novo pattern. Those responders tended to have a lower cumulative incidence of recurrence than those non-responders (43.2 vs 84.8/100 person-month, log-rank P = 0.13). Those non-responders with a high MICA level (>100 pg/mL) carried the lowest cancer-free survival than those non-responders with a low MICA level and those responders (P = 0.002). Cox regression hazard analysis showed high baseline MICA level (Odds ratio [OR] = 4.8, 95% confidence interval [CI] = 1.1-20.8, P = 0.04) and a low platelet count (<100 000/mm(3) ) (OR = 5.4, 95% CI = 1.1-27.0, P = 0.04) predicted HCC recurrence.

CONCLUSIONS

PegIFN/RBV therapy carried a limited effect in the tertiary prevention of HCC. A high MICA level predicted HCC recurrence, particularly among those non-responders.

Pleiotropic Anti-Angiogenic and Anti-Oncogenic Activities of the Novel Mithralog Demycarosyl-3D-ß-D-Digitoxosyl-Mithramycin SK (EC-8042)

Demycarosyl-3D-ß-D-digitoxosyl-mithramycin SK (DIG-MSK) is a recently isolated analogue of mithramycin A (MTA) that showed differences with MTA in the DNA binding strength and selectivity. These differences correlated with a better therapeutic index and less toxicity in animal studies. Herein, we show that DIG-MSK displays a potent anti-tumor activity against different types of cancer cell lines, ovarian tumor cells being particularly sensitive to this drug. Of relevance, DIG-MSK exerts low toxicity on fibroblasts and peripheral blood mononuclear cells, this toxicity being significantly lower than that of MTA. In correlation with its antitumor activity, DIG-MSK strongly inhibited Sp1-mediated transcription and endogenous Sp1 mRNA expression, which correlated with the inhibition of the expression of key Sp1-regulated genes involved in tumorigenesis, including VEGFA, BCL2L1 (Bcl-XL), hTERT, BRCA2, MYC and SRC in several ovarian cells. Significantly, DIG-MSK was a stronger inhibitor of VEGFA expression than MTA. Accordingly, DIG-MSK also exhibited potent anti-angiogenic activity on microvascular endothelial cells. Likewise, it significantly inhibited the gene expression of VEGFR1, VEGFR2, FGFR, PDGFB and PDGFRA and, additionally, it induced the expression of the anti-angiogenic factors angiostatin and tunstatin. These effects correlated with a pro-apoptotic effect on proliferating microvascular endothelial cells and the inhibition of the formation of endothelial capillary structures. Overall, the pleiotropic activity of DIG-MSK in inhibiting key oncogenic and angiogenic pathways, together with its low toxicity profile, highlight the therapeutic potential of this new drug.

Characterization of 5' promoter and exon 1-3 polymorphism of the RAET1E gene

NKG2D is an activating receptor utilized by natural killer (NK) cells that recognizes upregulated ligands on infected, tumorigenic and damaged cells, leading to their cytolysis. However, the NKG2D ligand (NKG2DL) system is very complex with eight known gene loci encoding slightly different molecules. Furthermore, most NKG2DL gene loci such as MICA and MICB are highly polymorphic with potential for functional differences. NKG2DL expression on tumors varies depending on the malignancy and tumors can also release soluble NKG2DL that exert anergic effects on NK cells when engagement with NKG2D occurs, allowing escape from NK cell immunosurveillance. We carried out RAET1E typing of IHW cell line DNA, including a 580 bp proximal promoter fragment and exons 1-3 identifying 13 of 15 known RAET1E alleles. We determined 7 polymorphisms within the promoter region, including 2 already known that contributed to 9 promoter types. RAET1E alleles with variability in the extracellular region also differed with respect to promoter type and one allele, RAET1E(∗)003, associated with 5 promoter types. We then identified putative transcription factor binding sites for RAET1E, and found 5 of the 7 promoter polymorphisms may disrupt these sites, abrogating binding of transcription factors and varying the potential level of expression.

Two novel 5' promoter sequences of the MHC class I-related chain A gene

In this study, we have characterized two novel polymorphism of the 5' promoter sequence of MICA gene, MICA-P13 and MICA-P14, by sequence-based typing and cloning.

Diversity and characterization of polymorphic 5' promoter haplotypes of MICA and MICB genes

The major histocompatibility complex (MHC) class I-related chain A (MICA) and B (MICB) are ligands for the natural killer group 2, member D (NKG2D) activating receptor expressed on natural killer (NK) cells, natural killer T (NKT) cells, CD8+ T cells and γδ T cells. Natural killer group 2, member D (NKG2D) ligand expression is stress-related and upregulated by infected or oncogenic cells leading to cytolysis. MICA and MICB genes display considerable polymorphism among individuals and studies have investigated allelic association with disease and relevance of MICA in transplantation, with variable success. It is now known that promoters of MICA and MICB are polymorphic with some polymorphisms associating with reduced expression. We sequenced International Histocompatibility Workshop (IHW) cell line DNA to determine promoter types and alleles encoded by exons 2-6. We found 8 of 12 known MICA promoter polymorphisms and although promoter P7 dominated, other promoters associated with the same allele. For example, MICA*002:01 had promoters P3, P4 or P7 and the common MICA*008:01/04 type had P1, P6 or P7. Similarly, we sequenced 8 of 12 known MICB promoter haplotypes. Some coding region defined MICB alleles had a single promoter, for example, MICB*002:01 and promoter P9, whereas the promiscuous MICB*005 allele had promoters P1, P2, P5, P6, P10 or P12. The results indicate potential for variation in expression of MICA and MICB ligands between individuals with the same allelic types. If differential expression by polymorphic MICA and MICB promoters is confirmed by functional studies, involvement of these genes in disease susceptibility or adverse transplantation outcomes may require knowledge of both promoter and allelic types to make meaningful conclusions.

Reactive oxygen species- and DNA damage response-dependent NK cell activating ligand upregulation occurs at transcriptional levels and requires the transcriptional factor E2F1

Increasing evidence indicates that cancer cell stress induced by chemotherapeutic agents promote antitumor immune responses and contribute to their full clinical efficacy. In this article, we identify the signaling events underlying chemotherapy-induced NKG2D and DNAM-1 ligand expression on multiple myeloma (MM) cells. Our findings indicate that sublethal doses of doxorubicin and melphalan initiate a DNA damage response (DDR) controlling ligand upregulation on MM cell lines and patient-derived malignant plasma cells in Chk1/2-dependent and p53-independent manner. Drug-induced MICA and PVR gene expression are transcriptionally regulated and involve DDR-dependent E2F1 transcription factor activity. We also describe the involvement of changes in the redox state in the control of DDR-dependent upregulation of ligand surface expression and gene transcriptional activity by using the antioxidant agent N-acetyl-L-cysteine. Finally, in accordance with much evidence indicating that DDR and oxidative stress are major determinants of cellular senescence, we found that redox-dependent DDR activation upon chemotherapeutic treatment is critical for MM cell entry in premature senescence and is required for the preferential ligand upregulation on senescent cells, which are preferentially killed by NK cells and trigger potent IFN-γ production. We propose immunogenic senescence as a mechanism that promotes the clearance of drug-treated tumor cells by innate effector lymphocytes, including NK cells.

Enhanced sensitivity of colon tumour cells to natural killer cell cytotoxicity after mild thermal stress is regulated through HSF1-mediated expression of MICA

PURPOSE

Previously we showed that mild thermal stress increased natural killer (NK) cell-mediated tumour cytotoxicity and that this could be blocked by anti-NKG2D or anti-MICA (major histolocompatability complex (MHC) class I related chain A) antibodies. Here, we investigated the role of the transcription factor heat shock factor 1 (HSF1) in thermal regulation of MICA expression in tumour cells in vitro and in vivo.

MATERIALS AND METHODS

Hyperthermia experiments were conducted in vitro and in mice using a target temperature of 39.5 °C. Apoptotic cells and NK cells in situ were visualised by use of the TUNEL assay or expression of NKp46 respectively. Using Colo205 cells, HSF1 message was blocked utilising siRNA while luciferase reporter assays were used to measure the activity of the MICA promoter in vitro. Cell surface MICA was measured by flow cytometry.

RESULTS

Following whole body hyperthermia (WBH), tumour tissues showed an increase in NK cells and apoptosis. Mild thermal stress resulted in a transient increase in surface MICA and enhanced NK cytotoxicity of the Colo205 colon cancer cell line. Silencing (mRNA) HSF1 expression in Colo205 cells prevented the thermal enhancement of MICA message and surface protein levels, with partial loss of thermally enhanced NK cytotoxicity. Mutations of the HSF1 binding site on the MICA promoter implicated HSF1 in the thermal enhancement of MICA. Some, but not all, patient-derived colon tumour derived xenografts also exhibited an enhanced MICA message expression after WBH.

CONCLUSIONS

Up-regulation of MICA expression in Colo205 cells and enhanced sensitivity to NK cell killing following mild thermal stress is dependent upon HSF1.

Expression of stress ligands of the immunoreceptor NKG2D in melanoma: regulation and clinical significance

Tumor cells, in particular melanoma cells, can be detected as abnormal self by cytotoxic lymphocytes of the innate and adaptive immune system. Of major importance in this process is the activating lymphocyte receptor NKG2D that in humans binds to MIC and ULBP surface molecules on tumor cells. Expression of NKG2D ligands (NKG2DL) is an early event in malignant transformation, induced by stress-associated and oncogene-driven pathways. Thus NKG2DL expression is considered as an innate barrier against tumor development. However, tumor cells can overcome this barrier by shedding of NKG2DL. Ligand shedding leads to elevated levels of soluble ligands in sera of tumor patients that in case of melanoma are of strong prognostic relevance. Here we review important aspects of NKG2DL expression and regulation in tumor cells with a focus on melanoma, and discuss their clinical relevance and potential in immunotherapy.

An in-depth characterization of the major psoriasis susceptibility locus identifies candidate susceptibility alleles within an HLA-C enhancer element

Psoriasis is an immune-mediated skin disorder that is inherited as a complex genetic trait. Although genome-wide association scans (GWAS) have identified 36 disease susceptibility regions, more than 50% of the genetic variance can be attributed to a single Major Histocompatibility Complex (MHC) locus, known as PSORS1. Genetic studies indicate that HLA-C is the strongest PSORS1 candidate gene, since markers tagging HLA-Cw*0602 consistently generate the most significant association signals in GWAS. However, it is unclear whether HLA-Cw*0602 is itself the causal PSORS1 allele, especially as the role of SNPs that may affect its expression has not been investigated. Here, we have undertaken an in-depth molecular characterization of the PSORS1 interval, with a view to identifying regulatory variants that may contribute to disease susceptibility. By analysing high-density SNP data, we refined PSORS1 to a 179 kb region encompassing HLA-C and the neighbouring HCG27 pseudogene. We compared multiple MHC sequences spanning this refined locus and identified 144 candidate susceptibility variants, which are unique to chromosomes bearing HLA-Cw*0602. In parallel, we investigated the epigenetic profile of the critical PSORS1 interval and uncovered three enhancer elements likely to be active in T lymphocytes. Finally we showed that nine candidate susceptibility SNPs map within a HLA-C enhancer and that three of these variants co-localise with binding sites for immune-related transcription factors. These data indicate that SNPs affecting HLA-Cw*0602 expression are likely to contribute to psoriasis susceptibility and highlight the importance of integrating multiple experimental approaches in the investigation of complex genomic regions such as the MHC.

Regulation of NKG2D signaling during the epithelial-to-mesenchymal transition

The plasma membrane receptor natural killer group 2 member D (NKG2D) underpins a major mechanism whereby natural killer (NK) and T cells recognize malignant cells. We have recently demonstrated that the epithelial-to-mesenchymal transition, one of the first steps of metastatic dissemination, is under the control of an immunological checkpoint that relies on NKG2D-mediated immune responses.

Identification of a functional variant in the MICA promoter which regulates MICA expression and increases HCV-related hepatocellular carcinoma risk

Hepatitis C virus (HCV) infection is the major cause of hepatocellular carcinoma (HCC) in Japan. We previously identified the association of SNP rs2596542 in the 5' flanking region of the MHC class I polypeptide-related sequence A (MICA) gene with the risk of HCV-induced HCC. In the current study, we performed detailed functional analysis of 12 candidate SNPs in the promoter region and found that a SNP rs2596538 located at 2.8 kb upstream of the MICA gene affected the binding of a nuclear protein(s) to the genomic segment including this SNP. By electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) assay, we identified that transcription factor Specificity Protein 1 (SP1) can bind to the protective G allele, but not to the risk A allele. In addition, reporter construct containing the G allele was found to exhibit higher transcriptional activity than that containing the A allele. Moreover, SNP rs2596538 showed stronger association with HCV-induced HCC (P = 1.82 × 10(-5) and OR = 1.34) than the previously identified SNP rs2596542. We also found significantly higher serum level of soluble MICA (sMICA) in HCV-induced HCC patients carrying the G allele than those carrying the A allele (P = 0.00616). In summary, we have identified a functional SNP that is associated with the expression of MICA and the risk for HCV-induced HCC.

Epithelial-mesenchymal transition induces an antitumor immune response mediated by NKG2D receptor

Epithelial-mesenchymal transition (EMT) is a morphogenetic process characterized by the acquisition of mesenchymal properties linked with an invasive phenotype and metastasis of tumor cells. NK group 2, member D (NKG2D) is an NK cell-activating receptor crucially involved in cancer immunosurveillance. In this study, we show that induction of EMT by TGF-β stimulation of human keratinocytes, by glycogen synthase kinase-3β inhibition in several epithelial tumor cell lines, and by Snail1 overexpression in colorectal cancer cells strongly upregulated the expression of NKG2D ligands (NKG2DLs), MHC class I chain-related molecules A and B (MICA/B) and ULBP1-3. Overexpression of Snail1 and inhibition of glycogen synthase kinase-3β in colorectal tumor cells markedly induced the activity of Sp1 transcription factor, which plays a key role in the upregulation of NKG2DL expression during EMT. The stimulation of MICA/B expression by TGF-β treatment was independent of Sp1, but it involved posttranslational mechanisms mediated by mammalian target of rapamycin pathway. Accordingly, with the increased expression of NKG2DLs, triggering of EMT rendered cancer cells more susceptible to NKG2D-mediated killing by NK cells. In agreement, MICA/B were expressed in vivo in well-differentiated colorectal tumors with retained epithelial characteristics, whereas no expression of MICA/B was detected in poorly differentiated and invasive colorectal tumors that have lost epithelial characteristics. This decrease of MICA/B expression was associated with a dramatic increase of NKG2D(+)-tumor infiltrating lymphocytes. Overall, our findings indicate that EMT is a relevant checkpoint in the control of tumor progression through NKG2D-mediated immune responses.

17β-Estradiol suppresses MHC class I chain-related B gene expression via an intact GC box

Major histocompatibility complex class I chain-related B (MICB) is a membrane-bound glycoprotein involved in both innate and adaptive immunity through its interaction with NKG2D receptors present on γδ T, αβ CD8(+) T, and natural killer cells. Factors known to upregulate MICB expression include heat shock, viral or bacterial infection, and tumorigenesis, and here, we explored the effect of 17β-estradiol (E2) on MICB regulation. Physiological concentrations of E2 were found to suppress MICB mRNA and surface protein levels and this effect was antagonized by the antiestrogen ICI 182780. The inhibitory effect of E2 was also observed for other NKG2D ligands, MICA and ULBPs. Evaluation of promoter fragments from the common MICB*00502 allele revealed that inhibition of transcription by E2 required the GC box at -87. The electrophoretic mobility shift assay and supershift analysis established the presence of SP1, SP3, or estrogen receptor α recognition sites within the MICB promoter sequence and interaction of these factors in situ was confirmed by chromatin immunoprecipitation. We conclude that E2 upon forming a complex with its cognate receptor suppresses MICB expression through binding with SP1/SP3 sites within the MICB promoter GC box. These results suggest that the partial benefit of 17β-estradiol on autoimmune diseases may be mediated by reducing the immune NKG2D ligands like MICB.

The genotype of RAET1L (ULBP6), a ligand for human NKG2D (KLRK1), markedly influences the clinical outcome of allogeneic stem cell transplantation

NKG2D (KLRK1) is an activating receptor on natural killer (NK) and T-cells and binds a diverse panel of polymorphic ligands encoded by the MIC and RAET1 gene families. We studied the clinical importance of retinoic acid early transcript-1 (RAET1) polymorphism in allogeneic stem cell transplantation (SCT) by determining the frequency of 18 single nucleotide polymorphisms (SNPs) and individual RAET1 alleles in 371 patient-donor pairs and relating this to clinical outcome. A strong association was observed between the presence of five SNPs within the patient RAET1L (ULBP6) gene and relapse-free survival and overall survival. Two common alleles of RAET1L were determined and the presence of the protective RAET1L*02 allele in the patient was associated with a relapse-free survival of 44% at 8 years compared with just 25% in patients who lacked a RAET1L*02 allele (P < 0·001). Overall survival at this time was 55% in those with RAET1L*02 allele compared to 39% in patients who lacked a RAET1L*02 allele (P = 0·003). These novel findings indicate a critical role for NKG2D-RAET1L interactions in determining SCT clinical outcome and show RAET1L may have an important influence on regulating the strength of the alloreactive immune response. The data will be of value in guiding the development of future transplant therapy protocols.

Susceptibility to natural killer cell-mediated lysis of colon cancer cells is enhanced by treatment with epidermal growth factor receptor inhibitors through UL16-binding protein-1 induction

We have previously shown that inhibition of intracellular signaling pathways by treatment with quercetin induced the expression of natural killer cell group 2D (NKG2D) ligands on cancer cells and made the cells sensitive to natural killer (NK)-cell mediated cytotoxicity. In the present study, we investigated whether epidermal growth factor receptor (EGFR) inhibitors could induce the expression of NKG2D ligands in colon cancer cells. Treatment with EGFR inhibitors predominantly increased the levels of mRNA transcripts and surface protein of UL16-binding protein-1 (ULBP1) in various colon cancer cells, including KM12, Caco-2, HCT-15, and HT-29, which express EGFR, and increased susceptibility of these colon cancer cells to NK-92 cells. The expression of ULBP1 was not induced by inhibitors of nuclear factor-κB, phosphatidylinositol 3 kinase, and MAPK, but was induced by inhibitors of PKC, and the induction of ULBP1 expression with EGFR inhibitors was prevented by treatment with PMA in colon cancer cells. A transcription factor, activator protein-2 alpha (AP-2α), which has a suppressive effect on ULBP1 transcription, was prevented from binding to the ULBP1 promoter by treatment with EGFR inhibitors. The present study suggests that EGFR inhibitors can enhance the susceptibility to NK cell-mediated lysis of colon cancer cells by induction of ULBP1 via inhibition of the PKC pathway.

MHC class I-related chain A and B ligands are differentially expressed in human cervical cancer cell lines

BACKGROUND

Natural killer (NK) cells are an important resource of the innate immune system directly involved in the spontaneous recognition and lysis of virus-infected and tumor cells. An exquisite balance of inhibitory and activating receptors tightly controls the NK cell activity. At present, one of the best-characterized activating receptors is NKG2D, which promotes the NK-mediated lysis of target cells by binding to a family of cell surface ligands encoded by the MHC class I chain-related (MIC) genes, among others. The goal of this study was to describe the expression pattern of MICA and MICB at the molecular and cellular levels in human cervical cancer cell lines infected or not with human papillomavirus, as well as in a non-tumorigenic keratinocyte cell line.

RESULTS

Here we show that MICA and MICB exhibit differential expression patterns among HPV-infected (SiHa and HeLa) and non-infected cell lines (C33-A, a tumor cell line, and HaCaT, an immortalized keratinocyte cell line). Cell surface expression of MICA was higher than cell surface expression of MICB in the HPV-positive cell lines; in contrast, HPV-negative cells expressed lower levels of MICA. Interestingly, the MICA levels observed in C33-A cells were overcome by significantly higher MICB expression. Also, all cell lines released higher amounts of soluble MICB than of soluble MICA into the cell culture supernatant, although this was most pronounced in C33-A cells. Additionally, Real-Time PCR analysis demonstrated that MICA was strongly upregulated after genotoxic stress.

CONCLUSIONS

This study provides evidence that even when MICA and MICB share a high degree of homology at both genomic and protein levels, differential regulation of their expression and cell surface appearance might be occurring in cervical cancer-derived cells.

Therapeutic effects of the Sp1 inhibitor mithramycin A in glioblastoma

Mithramycin A (MitA) is a chemotherapeutic compound which has been used in the therapy of several types of cancer. For experimental cancer it has been shown that MitA mediates the expression of genes involved in tumor progression such as genes involved in immunosurveillance, cell motility or cell death. MitA works synergistically with Apo2L/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), and with antiangiogenic agents. We were therefore interested in analyzing whether MitA might be a suitable agent for glioma therapy. We demonstrate herein that the cell death sensitizing effects of MitA are cell line specific, independent of the endogenous status of the tumor suppressor p53 as well as of the endogenous expression of X-linked inhibitor of apoptosis (XIAP) or basal sensitivity towards death ligand-induced cell death. In glioma cells, MitA reduced the secretion and activity of the migration-involved matrix metalloproteinases (MMP), diminished vascular endothelial growth factor (VEGF), and increased recepteur d'origine nantais (RON) kinase messenger RNA (mRNA), paralleled by a significant reduction of glioma cell migration. In contrast to other cancer types, in glioma cells MitA did not alter the expression of the immunorelevant genes major histocompatibility complex I class related (MIC)-A, MIC-B or UL16 binding proteins (ULBP). We conclude that, whereas MitA-mediated reduction of XIAP expression and sensitization to Apo2L/TRAIL are cell line specific, its antimigratory effects are more general and might be the result of altered expression of MMP, VEGF, and/or RON kinase. Therefore, MitA might be a potential agent to reduce glioma cell migration.

MICA polymorphism identified by whole genome array associated with NKG2D-mediated cytotoxicity in T-cell large granular lymphocyte leukemia

BACKGROUND

Large granular lymphocyte leukemia is a semi-autonomous clonal proliferation of cytotoxic T cells accompanied by immune cytopenias and various autoimmune conditions. Due to the rarity of this disease and its association with autoimmune diseases, a theoretical germline or somatic mutation might have significant penetrance, thus enabling detection, even from samples of suboptimal size, through genome-wide association studies.

DESIGN AND METHODS

To investigate a non-mendelian genetic predisposition to large granular lymphocyte leukemia, we used a step-wise method for gene discovery. First, a modified 'random forests' technique was used for candidate gene identification: this was followed by traditional allele-specific polymerase chain reaction, sequencing modalities, and mechanistic assays.

RESULTS

Our analysis found an association with MICA, a non-peptide-presenting, tightly regulated, stress-induced MHC-like molecule and cognate receptor for NKG2D, found abundantly on large granular lymphocyte leukemia cells. Sequencing of germline DNA revealed a higher frequency of MICA*00801/A5.1 in patients with large granular lymphocyte leukemia than in matched controls (64% versus 41%, P<0.001, homozygous 40% versus 15%, P<0.001). Flow cytometry was employed to determine the expression of MICA within hematologic compartments, showing that the signal intensity of MICA was increased in granulocytes from neutropenic patients with large granular lymphocyte leukemia in comparison with that in controls (P=0.033). Furthermore, neutrophil counts were inversely correlated with MICA expression (R(2)=0.50, P=0.035). Finally, large granular lymphocyte leukemia cells were able to selectively kill MICA(+) Ba/F3 lymphocytes transfected with human MICA*019 in a dose-dependent manner compared to naïve cells (P<0.001), an effect mitigated by administration of an anti-NKG2D antibody (P=0.033).

CONCLUSIONS

Our results illustrate that MICA-NKG2D played a role in disease pathogenesis in the majority of patients in our cohort of cases of large granular lymphocyte leukemia and further investigation into this signaling axis may provide potent therapeutic targets.

Sodium butyrate upregulates expression of NKG2D ligand MICA/B in HeLa and HepG2 cell lines and increases their susceptibility to NK lysis

Natural killer (NK) cells are important effectors in the immune response to tumors. A number of cell-surface inhibitory and activating receptors on NK cells tightly regulate their interaction with target cell ligands. In particular, the strength of an anti-tumor immune response appears to depend critically on surface levels of one activating receptor, NKG2D. Correspondingly, expression of NKG2D ligands on target cells is a requirement for effective tumor immunosurveillance and the elimination of pathogen-infected cells. Sodium butyrate, a potent repressor of histone deacetylase (HDAC), has recently been proposed as a potential agent in cancer treatment based on its ability to modify, in several cancer cell types, the expression of a variety of genes related to cell cycle regulation and apoptosis. Here we report that, in the HeLa and HepG2 tumor cell lines, sodium butyrate upregulated the expression of the MHC class I-related chain molecules A and B (MICA and MICB) at both the mRNA and protein levels, resulting in an enhanced susceptibility of cells in both lines to NK lysis. It also led to an elevated expression of heat shock protein 70 (HSP70) and transcription factor Sp1, and increased the binding of transcription factors Sp1 and heat shock transcription factor 1 (HSF1) to the MICA/B promoter, resulting in increased expression of MICA and MICB. siRNA targeting Sp1 significantly attenuate the enhancement of MICA expression by sodium butyrate. These results suggest that sodium butyrate and other HDAC inhibitors may have therapeutic potential by enhancing the immune response to cancer.

Potential role of NKG2D and its ligands in organ transplantation: new target for immunointervention

NKG2D is one of the best characterized activating receptors on Natural Killer (NK) and CD8+ T cells. This receptor recognizes several different ligands (MICA/MICB and ULBPs) induced by cellular stress and infection. In addition to the role described in cancer surveillance, recent data highlight the importance of NKG2D and its ligands in organ transplantation. Allografts show evidence of MICA and MICB expression in both acute and chronic rejection. The presence of anti-MICA antibodies has been correlated with incidence of graft rejection. Furthermore, NKG2D-ligand engagement activates NK cells, which provides T-cell costimulation, and enhances antigen specific CTL-mediated cytotoxicity. Activated NK cells may function as a bridge between innate and adaptive immunity associated with transplantation. Activated NK cells in response to IL-15 can also trigger organ rejection through NKG2D and affect the maturation of both donor and recipient antigen presenting cells (APCs) and ultimately the T-cell allogeneic response. Regulatory T cells, which modulate T-cell responses in organ transplantation and infections, were reduced in numbers by NK cells exposed to intracellular pathogens, possibly via interaction with one NK2GD receptor. Blockage of NKG2D-NKG2D-L interactions provides a novel pathway for development of inhibitors. These studies have important clinical and therapeutic implications in solid organ transplantation.

Genetic influence of the nonclassical major histocompatibility complex class I molecule MICB in multiple sclerosis susceptibility

It has been widely reported that the major histocompatibility complex (MHC) class II region provides the main genetic contribution to multiple sclerosis (MS) susceptibility. However, recent studies have suggested that the MHC class I region may also contribute to the development of MS. In this study, we investigated the possible association of the human leukocyte antigen (HLA)-B, MHC class I chain-related gene B (MICB) and MHC class I chain-related gene A (MICA) genes, located in the MHC class I region, with MS susceptibility. For this purpose, we analyzed the distribution of HLA-DR, HLA-B, MICB and MICA alleles in 121 MS patients and 156 healthy controls. Neither HLA-B nor MICA alleles were found to be associated with MS susceptibility, and only the frequency of HLA-DRB1*01 allele was found to be increased in controls (31% vs 14%, P(c) = 0.011). However, MICB*004 allele frequency was significantly increased in MS patients (46.3% vs 23.3%, P(c) < 0.001, odds ratio = 2.82, 95% confidence interval = 1.68-4.73). Although, MICB*004 and HLA-DRB1*15 belong to the AH 7.1 ancestral haplotype, the association of MICB*004 to MS susceptibility was found to be independent of HLA-DRB1*15 in our population. This and previous studies clearly suggest that the MHC class I, in addition to class II, could be involved in MS susceptibility.

NKG2D ligands: key targets of the immune response

NKG2D is an activating receptor expressed by NK and T cells. NKG2D ligands show a restricted expression in normal tissues, but they are frequently overexpressed in cancer and infected cells. The binding of NKG2D to its ligands activates NK and T cells and promotes cytotoxic lysis of the cells expressing these molecules. The mechanisms involved in the expression of the ligands of NKG2D play a key role in the recognition of stressed cells by the immune system and represent a promising therapeutic target for improving the immune response against cancer or autoimmune disease. In this review, we analyse the recent advances in understanding the regulation of NKG2D ligand expression and their therapeutic implications.

Opposing effects of interferon-alpha and interferon-gamma on the expression of major histocompatibility complex class I chain-related A in tumors

Natural killer cells are an important component of innate resistance to viruses, bacteria, certain parasites, and tumors. The activating receptor natural killer group 2D (NKG2D) plays a critical role in the elimination of tumor cells by cytotoxic effector cells. It has been shown that the strength of an antitumor immune response might be critically dependent on NKG2D ligard surface levels. Thus, it is essential to regulate the expression of NKG2D ligands in order to ensure effective tumor immunosurveillance and the elimination of pathogen-infected cells. In the present study, we found that interferon (IFN)-alpha and IFNgamma exert opposing effects on major histocompatibility complex class I-related chain A (MICA) expression in human tumor cells. IFNalpha promotes expression of the NKG2D ligand MICA in tumor cells and therefore enhances their sensitivity to natural killer lysis. In contrast, IFNgamma exerts the opposite effect. IFNalpha promotes MICA expression at the level of transcription by augmenting MICA promoter activity. IFNgamma modulates MICA expression not only at the transcriptional level, but also at the post-translational level by promoting proteolytic cleavage by matrix metalloproteinases. Further study is needed to clarify the precise regulatory mechanisms. The pathways involved in NKG2D ligand induction might represent a promising target for improving immune responses to cancer or infections.

Human MHC architecture and evolution: implications for disease association studies

Major histocompatibility complex (MHC) variation is a key determinant of susceptibility and resistance to a large number of infectious, autoimmune and other diseases. Identification of the MHC variants conferring susceptibility to disease is problematic, due to high levels of variation and linkage disequilibrium. Recent cataloguing and analysis of variation over the complete MHC has facilitated localization of susceptibility loci for autoimmune diseases, and provided insight into the MHC's evolution. This review considers how the unusual genetic characteristics of the MHC impact on strategies to identify variants causing, or contributing to, disease phenotypes. It also considers the MHC in relation to novel mechanisms influencing gene function and regulation, such as epistasis, epigenetics and microRNAs. These developments, along with recent technological advances, shed light on genetic association in complex disease.