Gene Summary

Gene:MICB; MHC class I polypeptide-related sequence B
Aliases: PERB11.2
Summary:This gene encodes a heavily glycosylated protein which is a ligand for the NKG2D type II receptor. Binding of the ligand activates the cytolytic response of natural killer (NK) cells, CD8 alphabeta T cells, and gammadelta T cells which express the receptor. This protein is stress-induced and is similar to MHC class I molecules; however, it does not associate with beta-2-microglobulin or bind peptides. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2014]
Databases:IMGT/GENE-DB (MICB), OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:MHC class I polypeptide-related sequence B
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
Show (15)
Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 01 September 2019 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.

  • Membrane Proteins
  • Chromosome 6
  • Histone Deacetylase Inhibitors
  • Natural Killer Cells
  • GPI-Linked Proteins
  • Polymerase Chain Reaction
  • Down-Regulation
  • Ligands
  • Polymorphism
  • Antineoplastic Agents
  • Pharmacogenetics
  • Young Adult
  • Breast Cancer
  • Valproic Acid
  • Virus Latency
  • Lymphocyte Activation
  • Cervical Cancer
  • T-Lymphocytes, Cytotoxic
  • Messenger RNA
  • Xenograft Models
  • Swine
  • Signal Transduction
  • Gene Expression
  • Mice, Inbred NOD
  • NK Cell Lectin-Like Receptor Subfamily K
  • Up-Regulation
  • Receptors, Immunologic
  • Hepatocellular Carcinoma
  • Cancer Gene Expression Regulation
  • Receptors, Natural Killer Cell
  • Type C Phospholipases
  • Liver Cancer
  • Flow Cytometry
  • Pancreatic Cancer
  • Histocompatibility Antigens Class I
  • Cytotoxicity, Immunologic
  • Intercellular Signaling Peptides and Proteins
  • Alleles
  • Promoter Regions
  • TNF
Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

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: MICB (cancer-related)

Hu X, Zhang J, Wang J, et al.
Landscape of B cell immunity and related immune evasion in human cancers.
Nat Genet. 2019; 51(3):560-567 [PubMed] Related Publications
Tumor-infiltrating B cells are an important component in the microenvironment but have unclear anti-tumor effects. We enhanced our previous computational algorithm TRUST to extract the B cell immunoglobulin hypervariable regions from bulk tumor RNA-sequencing data. TRUST assembled more than 30 million complementarity-determining region 3 sequences of the B cell heavy chain (IgH) from The Cancer Genome Atlas. Widespread B cell clonal expansions and immunoglobulin subclass switch events were observed in diverse human cancers. Prevalent somatic copy number alterations in the MICA and MICB genes related to antibody-dependent cell-mediated cytotoxicity were identified in tumors with elevated B cell activity. The IgG3-1 subclass switch interacts with B cell-receptor affinity maturation and defects in the antibody-dependent cell-mediated cytotoxicity pathway. Comprehensive pancancer analyses of tumor-infiltrating B cell-receptor repertoires identified novel tumor immune evasion mechanisms through genetic alterations. The IgH sequences identified here are potentially useful resources for future development of immunotherapies.

Luo D, Dong XW, Yan B, et al.
MG132 selectively upregulates MICB through the DNA damage response pathway in A549 cells.
Mol Med Rep. 2019; 19(1):213-220 [PubMed] Free Access to Full Article Related Publications
Natural killer (NK) cells recognize stress‑activated NK group 2, member D (NKG2D) ligands in tumors. In the present study, the expression levels of NKG2D ligands were examined in four lung cancer cell lines (A549, PLA801D, NCI‑H157 and NCI‑H520). In the A549 cells, the expression of MHC class I polypeptiderelated sequence (MIC)A/B and UL16 binding protein (ULBP)1 was weak, the expression of ULBP2 was typical, and neither ULBP3 nor ULBP4 were expressed. The mechanism underlying the regulatory effect of a cancer treatment agent on the expression of NKG2D ligands was investigated using the proteasome inhibitor MG132. Following treatment for 8 h with MG132, the transcription levels of MICB and ULBP1 were upregulated 10.62‑ and 11.09‑fold, respectively, and the expression levels of MICB and ULBP1 were increased by 68.18 and 23.65%, respectively. Notably, MICB exhibited significant time‑dependent change. MG132 increased the transcription of MICB by acting at a site in the 480‑bp MICB upstream promoter. The activity of the MICB promoter was upregulated 1.77‑fold following treatment with MG132. MG132 treatment improved the cytotoxicity of NK cells, which was partially blocked by an antibody targeting NKG2D, and more specifically the MICB molecule. The expression of MICB induced by MG132 was inhibited by KU‑55933 [ataxia telangiectasia mutated (ATM) kinase inhibitor], wortmannin (phosphoinositide 3 kinase inhibitor) and caffeine (ATM/ATM‑Rad3‑related inhibitor). The phosphorylation of checkpoint kinase 2 (Chk2), an event associated with DNA damage, was observed following treatment with MG132. These results indicated that MG132 selectively upregulates the expression of MICB in A549 cells, and increases the NKG2D‑mediated cytotoxicity of NK cells. The regulatory effect of MG132 may be associated with the activation of Chk2, an event associated with DNA damage. The combination of MG132 with NK cell immunotherapy may have a synergistic effect that improves the therapeutic effect of lung cancer treatment.

Zhou MT, Zhao C, Chen X, et al.
MicroRNA-34a promotes MICB expression in hepatocytes.
Carcinogenesis. 2018; 39(12):1477-1487 [PubMed] Related Publications
MicroRNA-34a (miR-34a) behaves as a tumor suppressor by decreasing the expression of oncogenes involved in multiple carcinogenic pathways. Intravenous delivery of miR-34a mimics has been investigated in clinical trials as a potential treatment for advanced cancers; however, the effect of miR-34a on cancer immune surveillance is controversial. In the current study, we found that miR-34a plays a dual role in the regulation of major histocompatibility complex class I-related sequence B (MICB) protein, a ligand of the NKG2D receptor. MiR-34a could both induce and reduce MICB expression by upregulating ataxia telangiectasia and Rad3-related (ATR) protein kinase and downregulating the transcription factor E2F1, respectively. The net effect of miR-34a on MICB expression depended on endogenous E2F1 levels. Overexpression of miR-34a promoted MICB expression in hepatocytes and hepatocellular carcinoma (HCC) cells that have low E2F1 levels but not in HCC cells that have high E2F1 levels. In HCC patients, the expression of miR-34a and MICB showed positive correlation in paratumor liver tissues, which have low E2F1 levels, but not in HCC tissues, which have high E2F1 levels. We showed that miR-34a overexpression in non-transformed liver cells enhanced cytolysis and interferon-γ production by NK-92MI cells. Furthermore, higher miR-34a expression in tumor and paratumor tissues was associated with positive and negative outcomes, respectively, in HCC patients. Our findings suggest that miR-34a induces MICB expression in paratumor liver tissues, which may cause liver damage and serious cytokine release syndrome, thus disclosing potential side effects of systemic administration of miR-34a in anticancer therapy.

Stepanenko AA, Chekhonin VP
A compendium of adenovirus genetic modifications for enhanced replication, oncolysis, and tumor immunosurveillance in cancer therapy.
Gene. 2018; 679:11-18 [PubMed] Related Publications
In this review, we specifically focus on genetic modifications of oncolytic adenovirus 5 (Ad5)-based vectors that enhance replication, oncolysis/spread, and virus-mediated tumor immunosurveillance. The finding of negative regulation of minor core protein V by SUMOylation led to the identification of amino acid residues, which when mutated increase adenovirus replication and progeny yield. Suppression of Dicer and/or RNAi pathway with shRNA or p19 tomato bushy stunt protein also results in significant enhancement of adenovirus replication and progeny yield. Truncation mutations in E3-19K or i-leader sequence or overexpression of adenovirus death protein (ADP) potently increase adenovirus progeny release and spread without affecting virus yield. Moreover, E3-19K protein, which was found to inhibit both major histocompatibility complex I (MHCI) and MHC-I chain-related A and B proteins (MICA/MICB) expression on the cell surface, protecting infected cells from T-lymphocyte and natural killer (NK) cell attack, may be tailored to selectively target only MHCI or MICA/MICB, or to lose the ability to downregulate both. At last, E3-19K protein may be exploited to deliver tumor-associated epitopes directly to the endoplasmic reticulum for loading MHCI in the transporter associated with antigen processing (TAP)-deregulated cells.

Wang Z, Wang Z, Li S, et al.
Decitabine Enhances Vγ9Vδ2 T Cell-Mediated Cytotoxic Effects on Osteosarcoma Cells
Front Immunol. 2018; 9:1239 [PubMed] Free Access to Full Article Related Publications
γδ T cell-based immunotherapy for osteosarcoma (OS) has shown limited success thus far. DNA-demethylating agents not only induce tumor cell death but also have an immunomodulatory function. In this study, we have assessed the potential benefit of combining decitabine (DAC, a DNA demethylation drug) and γδ T cells for OS immunotherapy. DAC increased the expression of natural killer group 2D (NKG2D) ligands (NKG2DLs), including major histocompatibility complex class I-related chains B (MICB) and UL16-binding protein 1 (ULBP1), on the OS cell surface, making the cells more sensitive to recognition and destruction by cytotoxic γδ T cells. The upregulation of MICB and ULBP1 was due to promoter DNA demethylation. Importantly, the killing of OS cells by γδ T cells was partially reversed by blocking the NKG2D receptor, suggesting that the γδ T cell-mediated cytolysis of DAC-pretreated OS cells was mainly dependent on the NKG2D-NKG2DL axis. The

Xu LJ, Ma Q, Zhu J, et al.
Combined inhibition of JAK1,2/Stat3‑PD‑L1 signaling pathway suppresses the immune escape of castration‑resistant prostate cancer to NK cells in hypoxia.
Mol Med Rep. 2018; 17(6):8111-8120 [PubMed] Free Access to Full Article Related Publications
Castration‑resistant prostate cancer (CRPC) is difficult to treat in current clinical practice. Hypoxia is an important feature of the CRPC microenvironment and is closely associated with the progress of CRPC invasion. However, no research has been performed on the immune escape of CRPC from NK cells. The present study focused on this subject. Firstly, when the CRPC cell lines C4‑2 and CWR22Rv1 were induced by hypoxia, the expression of the UL16 binding protein (ULBP) ligand family of natural killer (NK) group 2D (NKG2D; ULBP‑1, ULBP‑2 and ULBP‑3) and MHC class I chain‑related proteins A and B (MICA/MICB) decreased. NKG2D is the main activating receptor of NK cells. Tumor cells were then co‑cultured with NK cells to conduct NK cell‑mediated cytotoxicity experiments, which revealed the decreased immune cytolytic activity of NK cells on hypoxia‑induced CRPC cells. In exploring the mechanism behind this observation, an increase in programmed death‑ligand 1 (PD‑L1) expression in CRPC cells induced by hypoxia was observed, while the addition of PD‑L1 antibody effectively reversed the expression of NKG2D ligand and enhanced the cytotoxic effect of NK cells on CRPC cells. In the process of exploring the upstream regulatory factors of PD‑L1, inhibition of the Janus kinase (JAK)1,2/signal transducer and activator of transcription 3 (Stat3) signaling pathway decreased the expression of PD‑L1 in CRPC cells. Finally, it was observed that combined inhibition of JAK1,2/PD‑L1 or Stat3/PD‑L1 was more effective than inhibition of a single pathway in enhancing the immune cytolytic activity of NK cells. Taking these results together, it is thought that combined inhibition of the JAK1,2/PD‑L1 and Stat3/PD‑L1 signaling pathways may enhance the immune cytolytic activity of NK cells toward hypoxia‑induced CRPC cells, which is expected to provide novel ideas and targets for the immunotherapy of CRPC.

Yang X, Kuang S, Wang L, Wei Y
MHC class I chain-related A: Polymorphism, regulation and therapeutic value in cancer.
Biomed Pharmacother. 2018; 103:111-117 [PubMed] Related Publications
MICA and MICB are stress-induced molecules recognized by NKG2D, one of major activation receptors of natural killer (NK) cells. Upon binding to NKG2D, NKG2D-mediated cytolytic immune response of immune effector cells will be activated against virally infected and tumor cells expressing MICA. In the early oncogenic development, membrane-bound MICA serves as a key signal to recruit anti-tumor immune effectors. Nevertheless, both MICA polymorphic features and its dysregulated expression in evolving tumors have resulted in tumor evasion in various cancer types. Therefore, in order to reconstitute tumor immunosurveilance, it is of great significance that we understand MICA genetics, polymorphisms, mechanisms of MICA-associated tumor escape and molecular/cellular modulation of MICA. In this review, the MICA-associated co-expression networks involving microRNAs (miRNAs) and novel candidate long non-coding RNAs (lncRNAs) were also discussed. Given the current importance in the study of MICA gene, this review paper focuses on the role of MICA in different cancer types, and strategies that we manipulate MICA regulation against tumor proliferation.

Xie XP, Xie YF, Wang HQ
A regulation probability model-based meta-analysis of multiple transcriptomics data sets for cancer biomarker identification.
BMC Bioinformatics. 2017; 18(1):375 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Large-scale accumulation of omics data poses a pressing challenge of integrative analysis of multiple data sets in bioinformatics. An open question of such integrative analysis is how to pinpoint consistent but subtle gene activity patterns across studies. Study heterogeneity needs to be addressed carefully for this goal.
RESULTS: This paper proposes a regulation probability model-based meta-analysis, jGRP, for identifying differentially expressed genes (DEGs). The method integrates multiple transcriptomics data sets in a gene regulatory space instead of in a gene expression space, which makes it easy to capture and manage data heterogeneity across studies from different laboratories or platforms. Specifically, we transform gene expression profiles into a united gene regulation profile across studies by mathematically defining two gene regulation events between two conditions and estimating their occurring probabilities in a sample. Finally, a novel differential expression statistic is established based on the gene regulation profiles, realizing accurate and flexible identification of DEGs in gene regulation space. We evaluated the proposed method on simulation data and real-world cancer datasets and showed the effectiveness and efficiency of jGRP in identifying DEGs identification in the context of meta-analysis.
CONCLUSIONS: Data heterogeneity largely influences the performance of meta-analysis of DEGs identification. Existing different meta-analysis methods were revealed to exhibit very different degrees of sensitivity to study heterogeneity. The proposed method, jGRP, can be a standalone tool due to its united framework and controllable way to deal with study heterogeneity.

Nakajima NI, Niimi A, Isono M, et al.
Inhibition of the HDAC/Suv39/G9a pathway restores the expression of DNA damage-dependent major histocompatibility complex class I-related chain A and B in cancer cells.
Oncol Rep. 2017; 38(2):693-702 [PubMed] Free Access to Full Article Related Publications
Immunotherapy is expected to be promising as a next generation cancer therapy. Immunoreceptors are often activated constitutively in cancer cells, however, such levels of ligand expression are not effectively recognized by the native immune system due to tumor microenvironmental adaptation. Studies have demonstrated that natural-killer group 2, member D (NKG2D), a major activating immunoreceptor, responds to DNA damage. The upregulation of major histocompatibility complex class I-related chain A and B (MICA/B) (members of NKG2D ligands) expression after DNA damage is associated with NK cell-mediated killing of cancer cells. However, the regulation of DNA damage-induced MICA/B expression has not been fully elucidated in the context of the types of cancer cell lines. In the present study, we found that MICA/B expression varied between cancer cell lines after DNA damage. Screening in terms of chromatin remodeling identified that inhibitors related to chromatin relaxation via post-translational modification on histone H3K9, i.e. HDAC, Suv39 or G9a inhibition, restored DNA damage-dependent MICA/B expression in insensitive cells. In addition, we revealed that the restored MICA/B expression was dependent on ATR as well as E2F1, a transcription factor. We further revealed that low‑dose treatment of an HDAC inhibitor was sufficient to restore MICA/B expression in insensitive cells. Finally, we demonstrated that HDAC inhibition restored DNA damage‑dependent cytotoxic NK activity against insensitive cells. Thus, the present study revealed that DNA damage‑dependent MICA/B expression in insensitive cancer cells can be restored by chromatin relaxation via the HDAC/Suv39/G9a pathway. Collectively, manipulation of chromatin status by therapeutic cancer drugs may potentiate the antitumor effect by enhancing immune activation following radiotherapy and DNA damage-associated chemotherapy.

Garrido-Tapia M, Hernández CJ, Ascui G, et al.
STAT3 inhibition by STA21 increases cell surface expression of MICB and the release of soluble MICB by gastric adenocarcinoma cells.
Immunobiology. 2017; 222(11):1043-1051 [PubMed] Related Publications
NKG2D is an activating receptor expressed on NK cells that binds to a variety of ligands, including MICA and MICB. These cell surface glycoproteins are overexpressed under cellular transformation, thus playing an important role in cell-mediated immune response to tumors. STAT3 is a transcription factor that is constitutively active in cancer. It negatively regulates MICA expression on target cells, while its inhibition enhances NK cell cytotoxicity against tumors. In this work, we aimed to describe the effect of STAT3 signaling inhibition by STA21 on the regulation of MICB expression in gastric adenocarcinoma cells and its effect on the cytotoxic function of NK cells. Treatment of gastric adenocarcinoma cells with STA21 induced an increase in MICB expression and soluble MICB secretion, as well as a variable pattern on effector cell degranulation. Soluble MICB secretion by gastric adenocarcinoma cells was not affected by metalloprotease inhibition. We also observed that primary gastric adenocarcinoma tissue released soluble MICB into the extracellular milieu. Recombinant MICB induced a significant decrease in the levels of NKG2D receptor on effector NK and CD8+ T cells, which correlated with an impaired cytotoxic function. Altogether, our data provide evidence that STAT3 signaling pathway regulates MICB expression on gastric adenocarcinoma cells and that recombinant soluble MICB compromises the cytolytic activity of NK cells.

Raneros AB, Minguela A, Rodriguez RM, et al.
Increasing TIMP3 expression by hypomethylating agents diminishes soluble MICA, MICB and ULBP2 shedding in acute myeloid leukemia, facilitating NK cell-mediated immune recognition.
Oncotarget. 2017; 8(19):31959-31976 [PubMed] Free Access to Full Article Related Publications
Acute myeloid leukemia (AML) is a disease with great morphological and genetic heterogeneity, which complicates its prognosis and treatment. The hypomethylating agents azacitidine (Vidaza®, AZA) and decitabine (Dacogen®, DAC) have been approved for the treatment of AML patients, but their mechanisms of action are poorly understood. Natural killer (NK) cells play an important role in the recognition of AML blasts through the interaction of the activating NKG2D receptor with its ligands (NKG2DL: MICA/B and ULBPs1-3). However, soluble NKG2DL (sNKG2DL) can be released from the cell surface, impairing immune recognition. Here, we examined whether hypomethylating agents modulate the release of sNKG2DL from AML cells. Results demonstrated that AZA- and DAC-treated AML cells reduce the release of sNKG2DL, preventing downregulation of NKG2D receptor on the cell surface and promoting immune recognition mediated by NKG2D-NKG2DL engagement. We show that the shedding of MICA, MICB and ULBP2 is inhibited by the increased expression of TIMP3, an ADAM17 inhibitor, after DAC treatment. The TIMP3 gene is highly methylated in AML cells lines and in AML patients (25.5%), in which it is significantly associated with an adverse cytogenetic prognosis of the disease. Overall, TIMP3 could be a target of the demethylating treatments in AML patients, leading to a decrease in MICA, MICB and ULBP2 shedding and the enhancement of the lytic activity of NK cells through the immune recognition mediated by the NKG2D receptor.

Ghadially H, Brown L, Lloyd C, et al.
MHC class I chain-related protein A and B (MICA and MICB) are predominantly expressed intracellularly in tumour and normal tissue.
Br J Cancer. 2017; 116(9):1208-1217 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Major histocompatibility complex (MHC) class I chain-related protein A (MICA) and MHC class I chain-related protein B (MICB) are polymorphic proteins that are induced upon stress, damage or transformation of cells which act as a 'kill me' signal through the natural-killer group 2, member D receptor expressed on cytotoxic lymphocytes. MICA/B are not thought to be constitutively expressed by healthy normal cells but expression has been reported for most tumour types. However, it is not clear how much of this protein is expressed on the cell surface.
METHODS: Using a novel, well-characterised antibody and both standard and confocal microscopy, we systematically profiled MICA/B expression in multiple human tumour and normal tissue.
RESULTS: High expression of MICA/B was detected in the majority of tumour tissues from multiple indications. Importantly, MICA/B proteins were predominantly localised intracellularly with only occasional evidence of cell membrane localisation. MICA/B expression was also demonstrated in most normal tissue epithelia and predominantly localised intracellularly. Crucially, we did not observe qualitative differences in cell surface expression between tumour and MICA/B expressing normal epithelia.
CONCLUSIONS: This demonstrates for the first time that MICA/B is more broadly expressed in normal tissue and that expression is mainly intracellular with only a small fraction appearing on the cell surface of some epithelia and tumour cells.

Suresh PK
Membrane-bound versus soluble major histocompatibility complex Class I-related chain A and major histocompatibility complex Class I-related chain B differential expression: Mechanisms of tumor eradication versus evasion and current drug development strategies.
J Cancer Res Ther. 2016 Oct-Dec; 12(4):1224-1233 [PubMed] Related Publications
Major histocompatibility complex Class I-related chain A/chain B (MICA/MICB) is stress-inducible, highly polymorphic ligands whose expression at the transcript level has been detected in all tissues except the central nervous system. However, their restricted protein expression is due to their regulation at the posttranslational level. Its levels are elevated in virally infected and neoplastically transformed cells. Membrane expression of this NKG2DL marks the aberrant cells for elimination by those immune effector cells that express the cognate NKG2D receptor. Among the evasion strategies developed by tumors, the metalloprotease-dependent shedding of MICA/MICB from tumors (either the free or the exosome form) can contribute to the inhibition of cytolysis by the immune effector cells (all NK cells, most NKT cells; γδ CD8+ T cells and αβ CD8+ T cells, as well as some αβ CD4+ T cells). There are micro-RNA clusters that regulate surface expression and shedding. Polymorphic variants can be used as susceptibility/associative markers and can also possibly be used to correlate with tumor survival as well as staging/grading of tumors. Variations in the expression level require quantification of this marker for diagnostic/prognostic and therapeutic purposes. Mechanism-based studies would provide a better tumor-specific understanding of their relative roles in the processes of tumor cell elimination versus growth and progression. Last but not least, conventional, interlaboratory validated assays (for, e.g., antibody-based methods) should be replaced by robust, reproducible, feasible biophysics-based methods using tumor biopsies. Further, correlative DNA polymorphism-based studies can be done using biological fluids (for, e.g., human saliva) that can be sampled by minimally invasive means.

Wang W, Tian W, Zhu F, et al.
MICA Gene Deletion in 3411 DNA Samples from Five Distinct Populations in Mainland China and Lack of Association with Nasopharyngeal Carcinoma (NPC) in a Southern Chinese Han population.
Ann Hum Genet. 2016; 80(6):319-326 [PubMed] Related Publications
Deletion of major histocompatibility complex class I chain-related genes A (MICA*Del) was investigated in 3,411 DNA samples from two southern Chinese Han populations (Hunan Han, HNH; Guangdong Han, GDH), two northern Chinese populations (Inner Mongolia Han, IMH; Inner Mongolia Mongol, IMM) and one southeastern Chinese Han population (Fujian Han, FJH) using an in-house polymerase chain reaction-sequence specific priming (PCR-SSP) assay, which enables direct discrimination between heterozygote and homozygote for MICA*Del. MICA*Del showed a frequency ranging from 0.8% in FJH to 5.7% in IMM (P

Hilakivi-Clarke L, Wärri A, Bouker KB, et al.
Effects of In Utero Exposure to Ethinyl Estradiol on Tamoxifen Resistance and Breast Cancer Recurrence in a Preclinical Model.
J Natl Cancer Inst. 2017; 109(1) [PubMed] Free Access to Full Article Related Publications
Background: Responses to endocrine therapies vary among patients with estrogen receptor (ER+) breast cancer. We studied whether in utero exposure to endocrine-disrupting compounds might explain these variations.
Methods: We describe a novel ER+ breast cancer model to study de novo and acquired tamoxifen (TAM) resistance. Pregnant Sprague Dawley rats were exposed to 0 or 0.1 ppm ethinyl estradiol (EE2), and the response of 9,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors to 15 mg/kg TAM, with (n = 17 tumors in the controls and n = 20 tumors in EE2 offspring) or without 1.2 g/kg valproic acid and 5 mg/kg hydralazine (n = 24 tumors in the controls and n = 32 tumors in EE2 offspring) in the female offspring, was assessed. One-sided Chi2 tests were used to calculate P values. Comparisons of differentially expressed genes between mammary tumors in in utero EE2-exposed and control rats, and between anti-estrogen-resistant LCC9 and -sensitive LCC1 human breast cancer cells, were also performed.
Results: In our preclinical model, 54.2% of mammary tumors in the control rats exhibited a complete response to TAM, of which 23.1% acquired resistance with continued anti-estrogen treatment and recurred. Mammary tumors in the EE2 offspring were statistically significantly less likely to respond to TAM (P = .047) and recur (P = .007). In the EE2 offspring, but not in controls, adding valproic acid and hydralazine to TAM prevented recurrence (P < .001). Three downregulated and hypermethylated genes (KLF4, LGALS3, MICB) and one upregulated gene (ETV4) were identified in EE2 tumors and LCC9 breast cancer cells, and valproic acid and hydralazine normalized the altered expression of all four genes.
Conclusions: Resistance to TAM may be preprogrammed by in utero exposure to high estrogen levels and mediated through reversible epigenetic alterations in genes associated with epithelial-mesenchymal transition and tumor immune responses.

Guan Y, Li W, Hou Z, et al.
HBV suppresses expression of MICA/B on hepatoma cells through up-regulation of transcription factors GATA2 and GATA3 to escape from NK cell surveillance.
Oncotarget. 2016; 7(35):56107-56119 [PubMed] Free Access to Full Article Related Publications
Decreased expression of NKG2D ligands on HBV-infected human hepatoma cells impairs NK cells lysis. However, which components of HBV exert this effect and the precise mechanisms need to be further investigated. In the present study, we observed that the HBx and HBc genes significantly down-regulated MICA expression. Through analysis with the chromatin immunoprecipitation assay, we found that HBV infection promotes the expression of transcription factors GATA-2 and GATA-3, which specifically suppressed MICA/B expression by directly binding to the promoter region of MICA/B. HBx protein, acting as a co-regulator, forms a tripolymer with GATA2 and GATA3, thus promotes the GATA-2 or GATA-3-mediated of MICA/B suppression. HBc protein inhibits MICA/B expression via directly binding to the CpG island in the MICA/B promoter. Thus, our study identified the novel role of transcription factors GATA-2 and GATA-3 in suppressing MICA/B expression and clarified the mechanisms of HBx and HBc in downregulation of MICA/B expression. These findings provide novel mechanisms for the contribution of HBV to hepatoma cells escape from NK cell surveillance.

Xu X, Rao G, Li Y
Xanthine oxidoreductase is required for genotoxic stress-induced NKG2D ligand expression and gemcitabine-mediated antitumor activity.
Oncotarget. 2016; 7(37):59220-59235 [PubMed] Free Access to Full Article Related Publications
MICA/B (the major histocompatibility antigen-related chain A and B) and Rae I are stress-inducible ligands for the immune-receptor NKG2D. Mechanisms by which genotoxic stress and DNA damage induce the expression of NKG2D ligands remain incompletely understood. Here, we report that inhibition of xanthine oxidoreductase (XOR) activity by allopurinol or inhibition of XOR expression by gene knockdown abrogated genotoxic stress-induced expression of MICA/B and Rae I in three tumor cell lines. XOR knockdown also blocked gemcitabine-mediated antitumor activity in an orthotopic syngeneic mouse model of breast cancer. As a rate-limiting enzyme in the purine catabolic pathway, XOR generates two end-products, uric acid and reactive oxygen species (ROS). ROS scavenging had an insignificant effect on genotoxic drug-induced MICA/B expression but modestly inhibited radiation-induced MICA/B expression. Exogenous uric acid (in the form of monosodium urate) induced MICA/B expression by activating the MAP kinase pathway. Allopurinol blocked genotoxic stress-induced MAP kinase activation. Our study provides mechanistic insights into genotoxic stress-induced activation of the MAP kinase pathway and suggests that XOR is required for genotoxic stress-induced NKG2D ligand expression and gemcitabine-mediated antitumor activity.

Sauer M, Schuldner M, Hoffmann N, et al.
CBP/p300 acetyltransferases regulate the expression of NKG2D ligands on tumor cells.
Oncogene. 2017; 36(7):933-941 [PubMed] Free Access to Full Article Related Publications
Tumor surveillance of natural killer (NK) cells is mediated by the cytotoxicity receptor natural-killer group 2 member D (NKG2D). Ligands for NKG2D are generally not expressed on healthy cells, but induced on the surface of malignant cells. To date, NKG2D ligand (NKG2D-L) induction was mainly described to depend on the activation of the DNA damage response, although the molecular mechanisms that regulate NKG2D-L expression remain largely unknown. Here, we show that the acetyltransferases CBP (CREB-binding protein) and p300 play a crucial role in the regulation of NKG2D-L on tumor cells. Loss of CBP/p300 decreased the basal cell surface expression of human ligands and reduced the upregulation of MICA/B and ULBP2 in response to histone deacetylase inhibitors or DNA damage. Furthermore, CBP/P300 deficiency abrogated the sensitivity of stressed cells to NK cell-mediated killing. CBP/p300 were also identified as major regulators of mouse NKG2D ligand RAE-1 in vitro and in vivo using the Eμ-Myc lymphoma model. Mechanistically, we observed an enhanced activation of the CBP/p300 binding transcription factor CREB (cAMP response element-binding protein) correlating to the NKG2D-L upregulation. Moreover, increased binding of CREB and CBP/p300 to NKG2D-L promoters and elevated histone acetylation were detectable. This study provides strong evidence for a major role of CBP and p300 in orchestrating NKG2D-L induction and consequently immunosurveillance of tumors in mice and humans. These findings might help to develop novel immunotherapeutic approaches against cancer.

Bargostavan MH, Eslami G, Esfandiari N, Shams Shahemabadi A
MMP9 Promoter Polymorphism (-1562 C/T) Does not Affect the Serum Levels of Soluble MICB and MICA in Breast Cancer.
Iran J Immunol. 2016; 13(1):45-53 [PubMed] Related Publications
BACKGROUND: The role of Matrix Metalloproteinase 9 (MMP9) in tumor invasion and progression is prominent. A single nucleotide polymorphism (SNP) in the promoter region of MMP9 (-1562 C/T) increases the transcription and expression of this gene. On the other hand, MHC class I chain-related protein A and B (MICA/B) in soluble forms may impair tumor immunogenicity by reducing Natural Killer Group 2D (NKG2D) densities on NK cells and MMP9 enzyme activity has a prominent role in shedding of MICA/B.
OBJECTIVES: To investigate the association between MMP9 (-1562 C/T) polymorphism and serum MICA/B level in breast cancer patients.
METHODS: In this case-control study, 105 patients with breast cancer and 100 healthy age-matched women were selected from Yazd hospitals, Iran. The polymorphism of MMP9 (-1562 C/T) was determined by PCR-RFLP. Concentration of MICB and MICA in the sera of breast cancer patients and healthy women were measured using ELISA method.
RESULTS: The frequency of CC, CT and TT genotypes and T allele of the MMP9 (-1562 C/T) did not show significant differences between breast cancer patients and healthy donors (p>0.05). On the other hand, the mean serum levels of MICB and MICA were significantly elevated in patients compared with healthy individuals (p<0.05). In patients with MMP9CC genotype, the mean serum MICB concentration was significantly higher than those patients with CT polymorphism (p<0.05). Although the mean of blood MICA concentration in patients with the CT genotype was higher than those patients with CC genotype, the difference was not statistically significant.
CONCLUSION: The T allele of the MMP9 (-1562 C/T) does not show a correlation with serum levels of MICA and MICB in breast cancer patients.

Shiraishi K, Mimura K, Kua LF, et al.
Inhibition of MMP activity can restore NKG2D ligand expression in gastric cancer, leading to improved NK cell susceptibility.
J Gastroenterol. 2016; 51(12):1101-1111 [PubMed] Related Publications
BACKGROUND AND METHODS: Natural killer (NK) cells can react with tumor cells through the balance of inhibitory and stimulatory signals between NK cell surface receptors and their ligands, such as MHC class I chain-related A (MICA), MHC class I chain-related B (MICB), and several UL16-binding proteins (ULBPs). In the present study, we evaluated the relationship between NKG2D ligand expression and matrix metalloproteinase (MMP) activity in in vitro culture systems of a panel of gastric cancer cell lines (n = 10) and clinical samples (n = 102).
RESULTS: First, the surface expression of NK group 2 member D (NKG2D) ligands (MICA, MICB, ULBP-2, and ULBP-3) on tumor cells was markedly downregulated on in vitro culture, in parallel to the upregulation of MMPs analyzed by gelatin zymography and gene expression microarray, whereas the transcript levels of NKG2D ligands remained unchanged on in vitro culture. Second, MMP-specific inhibitors could restore the downregulated expression of NKG2D ligands and functionally improve susceptibilities to NK cells in vitro. Third, the production of soluble NKG2D ligands was increased on in vitro culture and was inhibited by MMP-specific inhibitors. Finally, there was a significant inverse correlation between MMP-9 expression and NKG2D ligand expression as analyzed by immunohistochemistry in clinical tumor samples.
CONCLUSION: The present study is a comprehensive study demonstrating that upregulation of MMP activity can induce a downregulation of expression of NKG2D ligands in gastric cancer cells, leading to lower-level susceptibility to NK cells.

Ritter C, Fan K, Paulson KG, et al.
Reversal of epigenetic silencing of MHC class I chain-related protein A and B improves immune recognition of Merkel cell carcinoma.
Sci Rep. 2016; 6:21678 [PubMed] Free Access to Full Article Related Publications
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.

Ribeiro CH, Kramm K, Gálvez-Jirón F, et al.
Clinical significance of tumor expression of major histocompatibility complex class I-related chains A and B (MICA/B) in gastric cancer patients.
Oncol Rep. 2016; 35(3):1309-17 [PubMed] Free Access to Full Article Related Publications
Gastric cancer (GC) is the third most common cause of cancer death worldwide. Natural killer cells play an important role in the immune defense against transformed cells. They express the activating receptor NKG2D, whose ligands belong to the MIC and ULBP/RAET family. Although it is well established that these ligands are generally expressed in tumors, the association between their expression in the tumor and gastric mucosa and clinical parameters and prognosis of GC remains to be addressed. In the present study, MICA and MICB expression was analyzed, by flow cytometry, in 23 and 20 pairs of gastric tumor and adjacent non-neoplasic gastric mucosa, respectively. Additionally, ligands expression in 13 tumors and 7 gastric mucosa samples from GC patients were evaluated by immunohistochemistry. The mRNA levels of MICA in 9 pairs of tumor and mucosa were determined by quantitative PCR. Data were associated with the clinicopathological characteristics and the patient outcome. MICA expression was observed in 57% of tumors (13/23) and 44% of mucosal samples (10/23), while MICB was detected in 50% of tumors (10/20) and 45% of mucosal tissues (9/20). At the protein level, ligand expression was significantly higher in the tumor than in the gastric mucosa. MICA mRNA levels were also increased in the tumor as compared to the mucosa. However, clinicopathological analysis indicated that, in patients with tumors >5 cm, the expression of MICA and MICB in the tumor did not differ from that of the mucosa, and tumors >5 cm showed significantly higher MICA and MICB expression than tumors ≤5 cm. Patients presenting tumors >5 cm that expressed MICA and MICB had substantially shorter survival than those with large tumors that did not express these ligands. Our results suggest that locally sustained expression of MICA and MICB in the tumor may contribute to the malignant progression of GC and that expression of these ligands predicts an unfavorable prognosis in GC patients presenting large tumors.

Miyashita T, Miki K, Kamigaki T, et al.
Low-dose gemcitabine induces major histocompatibility complex class I-related chain A/B expression and enhances an antitumor innate immune response in pancreatic cancer.
Clin Exp Med. 2017; 17(1):19-31 [PubMed] Related Publications
We investigated the effect of gemcitabine (GEM), a key drug for pancreatic cancer treatment, on the expression of cell surface MICA/B in pancreatic cancer cells and resulting cytotoxicity of γδ T cells. We assessed the effect of GEM on the upregulation of cell surface MICA/B expression by flow cytometry, utilizing six pancreatic cancer cell lines. MICA and CD16 expressions from resected pancreatic cancer patient specimens, which received neoadjuvant chemotherapy (NAC) with GEM, were analyzed by immunohistochemistry. GEM could increase MICA/B expression on cell surface in pancreatic cancer cell lines (in 2 of 6 cell lines). This effect was most effectively at concentration not affecting cell growth of GEM (0.001 μM), because MICA/B negative population was appeared at concentration at cytostatic and cytotoxic effect to cell growth (0.1 and 10 μM). The cytotoxic activity of γδ T cells against PANC-1 was detected and functions through interactions between NKG2D and MICA/B. However, the enhancement of NKG2D-dependent cytotoxicity with increased MICA/B expression, by GEM treatment, was not observed. In addition, soluble MIC molecules were released from pancreatic cancer cell lines in culture supernatant with GEM treatment. Immunohistochemical staining demonstrated that MICA expression in tumor cells and CD16 positive cells surrounding tumors were significantly higher in the NAC group compared to that of the control group. There was a significant correlation between NAC and MICA expression, as well as NAC and CD16 positive cell expression. The present results indicate that low-dose GEM-induced MICA/B expression enhances innate immune function rather than cytotoxicity in pancreatic cancer. In addition, our result suggests that the inhibition of cleavage and release of MIC molecules from the tumor surface could potentially improve NKG2D-dependent cytotoxicity.

Siew YY, Neo SY, Yew HC, et al.
Oxaliplatin regulates expression of stress ligands in ovarian cancer cells and modulates their susceptibility to natural killer cell-mediated cytotoxicity.
Int Immunol. 2015; 27(12):621-32 [PubMed] Related Publications
Selected cytotoxic chemicals can provoke the immune system to recognize and destroy malignant tumors. Most of the studies on immunogenic cell death are focused on the signals that operate on a series of receptors expressed by dendritic cells to induce tumor antigen-specific T-cell responses. Here, we explored the effects of oxaliplatin, an immunogenic cell death inducer, on the induction of stress ligands and promotion of natural killer (NK) cell-mediated cytotoxicity in human ovarian cancer cells. The results indicated that treatment of tumor cells with oxaliplatin induced the production of type I interferons and chemokines and enhanced the expression of major histocompatibility complex class I-related chains (MIC) A/B, UL16-binding protein (ULBP)-3, CD155 and TNF-related apoptosis-inducing ligand (TRAIL)-R1/R2. Furthermore, oxaliplatin but not cisplatin treatment enhanced susceptibility of ovarian cancer cells to NK cell-mediated cytolysis. In addition, activated NK cells completely abrogated the growth of cancer cells that were pretreated with oxaliplatin. However, cancer cells pretreated with the same concentration of oxaliplatin alone were capable of potentiating regrowth over a period of time. These results suggest an advantage in combining oxaliplatin and NK cell-based therapy in the treatment of ovarian cancer. Further investigation on such potential combination therapy is warranted.

Xuan XY, Zhang JF, Hu GM, et al.
Upregulated expression of NKG2D and its ligands give potential therapeutic targets for patients with thymoma.
Cancer Gene Ther. 2015; 22(7):368-74 [PubMed] Related Publications
The activating receptor NKG2D (natural killer group 2, member D) of natural killer (NK) cells promotes tumor immune surveillance by targeting ligands selectively induced on cancer cells, and thus having an important role in antitumor immune response. Because these ligands are not widely expressed on healthy adult tissue, NKG2D ligands may present as useful target for immunotherapeutic approaches in cancer. In this study, to elucidate the role of NKG2D-NKG2D ligand interaction in thymoma tissues and to evaluate the potential role of NKG2D ligands as therapeutic target for thymoma, we examined the expression of NKG2D and its specific ligands: MICA (major histocompatibility complex class I chain-related protein A), MICB (major histocompatibility complex class I chain-related protein B) and ULBP (UL16-binding protein) in 36 thymomas (6 subtype A, 6 subtype AB, 8 subtype B1, 5 subtype B2, 6 subtype B3 and 5 subtype C), 15 thymic atrophy and 8 thymic hyperplasia by immunohistochemistry and reverse transcription-real-time-PCR methods. We demonstrated that both mRNA and protein levels of NKG2D, MICA, MICB and ULBP were upregulated in six types of thymomas compared with those in atrophic thymus or proliferating thymus. Furthermore, the NKG2D ligands were found to be frequently coexpressed on thymoma cells. Furthermore, the expression of MICA, MICB and ULBP in subtype C was higher compared with those in subtype A, AB, B1, B2 and B3. Thus, we concluded that high expressions of NKG2D, MICA, MICB and ULBP1 were shown in patients with thymoma, and this may enhance the recognition function of NK cells to eliminate tumor cells. MICA, MICB and ULBP presented an attractive target for thymoma therapy. The abnormal expression of NKG2D, MICA, MICB and ULBP1 can provide us with evidence of the occurrence of thymoma and could also be used as a target in the treatment of thymoma.

Zingoni A, Cecere F, Vulpis E, et al.
Genotoxic Stress Induces Senescence-Associated ADAM10-Dependent Release of NKG2D MIC Ligands in Multiple Myeloma Cells.
J Immunol. 2015; 195(2):736-48 [PubMed] Related Publications
Genotoxic stress can promote antitumor NK cell responses by upregulating the surface expression of activating ligands on cancer cells. Moreover, a number of studies suggested a role for soluble NK group 2D ligands in the impairment of NK cell tumor recognition and killing. We investigated whether genotoxic stress could promote the release of NK group 2D ligands (MHC class I-related chain [MIC]A and MICB), as well as the molecular mechanisms underlying this event in human multiple myeloma (MM) cells. Our results show that genotoxic agents used in the therapy of MM (i.e., doxorubicin and melphalan) selectively affect the shedding of MIC molecules that are sensitive to proteolytic cleavage, whereas the release of the short MICA*008 allele, which is frequent in the white population, is not perturbed. In addition, we found that a disintegrin and metalloproteinase 10 expression is upregulated upon chemotherapeutic treatment both in patient-derived CD138(+)/CD38(+) plasma cells and in several MM cell lines, and we demonstrate a crucial role for this sheddase in the proteolytic cleavage of MIC by means of silencing and pharmacological inhibition. Interestingly, the drug-induced upregulation of a disintegrin and metalloproteinase 10 on MM cells is associated with a senescent phenotype and requires generation of reactive oxygen species. Moreover, the combined use of chemotherapeutic drugs and metalloproteinase inhibitors enhances NK cell-mediated recognition of MM cells, preserving MIC molecules on the cell surface and suggesting that targeting of metalloproteinases in conjunction with chemotherapy could be exploited for NK cell-based immunotherapeutic approaches, thus contributing to avoid the escape of malignant cells from stress-elicited immune responses.

Lanier LL
NKG2D Receptor and Its Ligands in Host Defense.
Cancer Immunol Res. 2015; 3(6):575-82 [PubMed] Free Access to Full Article Related Publications
NKG2D is an activating receptor expressed on the surface of natural killer (NK) cells, CD8(+) T cells, and subsets of CD4(+) T cells, invariant NKT cells (iNKT), and γδ T cells. In humans, NKG2D transmits signals by its association with the DAP10 adapter subunit, and in mice alternatively spliced isoforms transmit signals either using DAP10 or DAP12 adapter subunits. Although NKG2D is encoded by a highly conserved gene (KLRK1) with limited polymorphism, the receptor recognizes an extensive repertoire of ligands, encoded by at least eight genes in humans (MICA, MICB, RAET1E, RAET1G, RAET1H, RAET1I, RAET1L, and RAET1N), some with extensive allelic polymorphism. Expression of the NKG2D ligands is tightly regulated at the level of transcription, translation, and posttranslation. In general, healthy adult tissues do not express NKG2D glycoproteins on the cell surface, but these ligands can be induced by hyperproliferation and transformation, as well as when cells are infected by pathogens. Thus, the NKG2D pathway serves as a mechanism for the immune system to detect and eliminate cells that have undergone "stress." Viruses and tumor cells have devised numerous strategies to evade detection by the NKG2D surveillance system, and diversification of the NKG2D ligand genes likely has been driven by selective pressures imposed by pathogens. NKG2D provides an attractive target for therapeutics in the treatment of infectious diseases, cancer, and autoimmune diseases.

Schilling D, Kühnel A, Tetzlaff F, et al.
NZ28-induced inhibition of HSF1, SP1 and NF-κB triggers the loss of the natural killer cell-activating ligands MICA/B on human tumor cells.
Cancer Immunol Immunother. 2015; 64(5):599-608 [PubMed] Free Access to Full Article Related Publications
The activity of natural killer (NK) cells is regulated by activating and inhibiting receptors, whereby the C-type lectin natural killer group 2D (NKG2D) receptor serves as the major activating receptor on NK cells which recognizes major histocompatibility class I chain-related proteins A and B (MICA/B). The MICA/B expression has been described to be regulated by the transcription factor heat shock factor 1 (HSF1). Inhibition of heat shock protein 90 (Hsp90) is known to induce the heat shock response via activation of HSF1 which is associated with tumor development, metastasis and therapy resistance and also with an increased susceptibility to NK cell-mediated lysis. Therefore, we compared the effects of Hsp90 inhibitor NVP-AUY922, HSF1 inhibitor NZ28 and HSF1 knockdown on the sensitivity of lung (H1339) and breast (MDA-MB-231, T47D) cancer cells to NK cell-mediated cytotoxicity and the expression of the NKG2D ligands MICA/B. Although NVP-AUY922 activates HSF1, neither the MICA/B surface density on tumor cells nor their susceptibility to NK cell-mediated lysis was affected. A single knockdown of HSF1 by shRNA decreased the surface expression of MICB but not that of MICA, and thereby, the NK cell-mediated lysis was only partially blocked. In contrast, NZ28 completely blocked the MICA/B membrane expression on tumor cells and thereby strongly inhibited the NK cell-mediated cytotoxicity. This effect might be explained by a simultaneous inhibition of the transcription factors HSF1, Sp1 and NF-κB by NZ28. These findings suggest that new anticancer therapeutics should be investigated with respect to their effects on the innate immune system.

Amin PJ, Shankar BS
Sulforaphane induces ROS mediated induction of NKG2D ligands in human cancer cell lines and enhances susceptibility to NK cell mediated lysis.
Life Sci. 2015; 126:19-27 [PubMed] Related Publications
AIMS: The goal of this study is to investigate the tumor cytotoxic effects of sulforaphane (SFN) and ionizing radiation (IR) as well as their ability to up-regulate natural killer group 2, member D (NKG2D) ligands and modulate the susceptibility of tumor cells to natural killer (NK) cell-mediated killing.
MAIN METHODS: Expression of MHC class I-related chain molecules A and B (MICA/MICB) and total reactive oxygen species (ROS) were assessed by flow cytometry following labeling with appropriate dyes or antibodies. NK cell cytotoxicity was determined by calcein release of target cells.
KEY FINDINGS: The expression of NKG2D ligands MICA/MICB was found to vary in all the four tumor cell lines tested (MCF7 < A549 < MDA-MB-231 < U937). Exposure of these cells to IR and SFN resulted in a differential induction of these ligands. IR induced an increase in expression of MICA/MICB in MCF7 cells and SFN induced MICA/MICB expression in A549 and MDA-MB-231 cells. This SFN induced increase in receptor expression resulted in increased susceptibility to NK cell mediated killing of tumor cells which was abrogated by blocking with anti-MICA/MICB antibody. SFN induced increase in MICA/MICB expression as well as increased susceptibility to NK cell mediated killing was abrogated by N-acetyl cysteine in A549 and MDA-MB-231 cells suggesting a ROS mediated mechanism.
SIGNIFICANCE: Our results indicate that SFN has an immunotherapeutic potential to be used in cancer therapy.

Lu Y, Hu J, Sun W, et al.
Hypoxia-mediated immune evasion of pancreatic carcinoma cells.
Mol Med Rep. 2015; 11(5):3666-72 [PubMed] Related Publications
Hypoxia is one of the characteristics of human and animal tumors. To investigate the association between hypoxia and the immune evasion of cancer cells, the present study examined paraffin sections of pancreatic tissues from patients with pancreatic carcinoma, chronic pancreatitis and normal pancreatic tissue and established a series of PANC‑1 cell lines, which were cultured under various hypoxic and normoxic conditions. The results demonstrated that the expression of hypoxia‑inducible 1α (HIF‑1α) in pancreatic carcinoma was significantly higher compared with that in the chronic pancreatitis and normal pancreatic tissues, which revealed that a hypoxic microenvironment existed in pancreatic carcinoma. HIF‑1α was inversely correlated with major histocompatibility complex class I chain‑related (MIC) genes, which indicated that hypoxia was involved in tumor immune evasion. The cell experiments demonstrated that the mechanism involved shedding of the MIC from the membrane of the pancreatic carcinoma cells, which then formed soluble (s)MIC. The sMIC genes downregulated natural killer (NK) group 2, member D and the cytotoxic activity of NK cells. Depending on its activity, the nitric oxide‑cyclic guanosine monophosphate‑protein kinase G signaling pathway can either increase or inhibit immune evasion of pancreatic cancer cells.

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