MicroRNAs and the immune response to respiratory virus infections

MicroRNAs (miRNAs) are small ssRNA molecules, which are involved in gene expression regulation at the post-transcriptional level. Their biological functions include modulation of both innate and adaptive immune response. miRNAs participate in the maintenance of the airway epithelial barrier and are also implicated in the modulation of antiviral defense in epithelial cells. The immune response to respiratory viruses such as rhinovirus, influenza virus and respiratory syncytial virus is associated with an altered expression of distinct miRNAs, and the changes in the miRNA expression profile in epithelial cells may contribute to the pathogenesis of both acute and chronic airway disease. Understanding the role of these small molecules in the antiviral immune response and identification of miRNAs target genes may help to clarify the mechanisms of virus-host interaction, and in the future may lead to development of new antiviral treatments.

MicroRNAs in allergy and asthma

microRNAs (miRNAs) are short, single-stranded RNA molecules that function together with the partner proteins and cause degradation of target mRNAs or inhibit their translation. A particular miRNA can have hundreds of targets; therefore, miRNAs cumulatively influence the expression of a large proportion of genes. The functions of miRNAs in human diseases have been studied since their discovery in mammalian cells approximately 12 years ago. However, the role of miRNAs in allergic disease has only very recently begun to be uncovered. The purpose of this review is to provide an overview of the functions of miRNAs involved in the development of allergic diseases. We describe here the functions of miRNAs that regulate Th2 polarization and influence general inflammatory and tissue responses. In addition, we will highlight findings about the functions of extracellular miRNAs as possible noninvasive biomarkers of diseases with heterogeneous phenotypes and complex mechanisms and briefly discuss advances in the development of miRNA-based therapeutics.

Two novel human cytomegalovirus NK cell evasion functions target MICA for lysosomal degradation

NKG2D plays a major role in controlling immune responses through the regulation of natural killer (NK) cells, αβ and γδ T-cell function. This activating receptor recognizes eight distinct ligands (the MHC Class I polypeptide-related sequences (MIC) A andB, and UL16-binding proteins (ULBP)1-6) induced by cellular stress to promote recognition cells perturbed by malignant transformation or microbial infection. Studies into human cytomegalovirus (HCMV) have aided both the identification and characterization of NKG2D ligands (NKG2DLs). HCMV immediate early (IE) gene up regulates NKGDLs, and we now describe the differential activation of ULBP2 and MICA/B by IE1 and IE2 respectively. Despite activation by IE functions, HCMV effectively suppressed cell surface expression of NKGDLs through both the early and late phases of infection. The immune evasion functions UL16, UL142, and microRNA(miR)-UL112 are known to target NKG2DLs. While infection with a UL16 deletion mutant caused the expected increase in MICB and ULBP2 cell surface expression, deletion of UL142 did not have a similar impact on its target, MICA. We therefore performed a systematic screen of the viral genome to search of addition functions that targeted MICA. US18 and US20 were identified as novel NK cell evasion functions capable of acting independently to promote MICA degradation by lysosomal degradation. The most dramatic effect on MICA expression was achieved when US18 and US20 acted in concert. US18 and US20 are the first members of the US12 gene family to have been assigned a function. The US12 family has 10 members encoded sequentially through US12-US21; a genetic arrangement, which is suggestive of an 'accordion' expansion of an ancestral gene in response to a selective pressure. This expansion must have be an ancient event as the whole family is conserved across simian cytomegaloviruses from old world monkeys. The evolutionary benefit bestowed by the combinatorial effect of US18 and US20 on MICA may have contributed to sustaining the US12 gene family.

Human cytomegalovirus and autoimmune disease

Human cytomegalovirus (HCMV) represents a prototypic pathogenic member of the β-subgroup of the herpesvirus family. A range of HCMV features like its lytic replication in multiple tissues, the lifelong persistence through periods of latency and intermitting reactivation, the extraordinary large proteome, and extensive manipulation of adaptive and innate immunity make HCMV a high profile candidate for involvement in autoimmune disorders. We surveyed the available literature for reports on HCMV association with onset or exacerbation of autoimmune disease. A causative linkage between HCMV and systemic lupus erythematosus (SLE), systemic sclerosis (SSc), diabetes mellitus type 1, and rheumatoid arthritis (RA) is suggested by the literature. However, a clear association of HCMV seroprevalence and disease could not be established, leaving the question open whether HCMV could play a coresponsible role for onset of disease. For convincing conclusions population-based prospective studies must be performed in the future. Specific immunopathogenic mechanisms by which HCMV could contribute to the course of autoimmune disease have been suggested, for example, molecular mimicry by UL94 in SSc and UL83/pp65 in SLE patients, as well as aggravation of joint inflammation by induction and expansion of CD4+/CD28− T-cells in RA patients. Further studies are needed to validate these findings and to lay the grounds for targeted therapeutic intervention.

Secretory pathways generating immunosuppressive NKG2D ligands: New targets for therapeutic intervention

Natural Killer Group 2 member D (NKG2D) activating receptor, present on the surface of various immune cells, plays an important role in activating the anticancer immune response by their interaction with stress-inducible NKG2D ligands (NKG2DL) on transformed cells. However, cancer cells have developed numerous mechanisms to evade the immune system via the downregulation of NKG2DL from the cell surface, including the release of NKG2DL from the cell surface in a soluble form. Here, we review the mechanisms involved in the production of soluble NKG2DL (sNKG2DL) and the potential therapeutic strategies aiming to block the release of these immunosuppressive ligands. Therapeutically enabling the NKG2D-NKG2DL interaction would promote immunorecognition of malignant cells, thus abrogating disease progression.

Cytomegalovirus microRNAs

The discovery that animals, plants and DNA viruses encode microRNAs (miRNAs) has transformed our understanding of the regulation of gene expression. miRNAs are ubiquitous small non-coding RNAs that regulate gene expression post-transcriptionally, generally by binding to sites within the 3' untranslated regions (UTR) of messenger RNA (mRNA) transcripts. To date, over 250 viral miRNAs have been identified primarily in members of the herpesvirus family. These viral miRNAs target both viral and cellular genes in order to regulate viral replication, the establishment and maintenance of viral latency, cell survival, and innate and adaptive immunity. This review will focus on our current knowledge of the targets and functions of human cytomegalovirus (HCMV) miRNAs and their functional equivalents in other herpesviruses.

Know Thyself: NK-Cell Inhibitory Receptors Prompt Self-Tolerance, Education, and Viral Control

Natural killer (NK) cells provide essential protection against viral infections. One of the defining features of this lymphocyte population is the expression of a wide array of variable cell surface stimulatory and inhibitory NK receptors (sNKR and iNKR, respectively). The iNKR are particularly important in terms of NK-cell education. As receptors specific for MHC class I (MHC I) molecules, they are responsible for self-tolerance and adjusting NK-cell reactivity based on the expression level of self-MHC I. The end result of this education is twofold: (1) inhibitory signaling tunes the functional capacity of the NK cell, endowing greater potency with greater education, and (2) education on self allows the NK cell to detect aberrations in MHC I expression, a common occurrence during many viral infections. Many studies have indicated an important role for iNKR and MHC I in disease, making these receptors attractive targets for manipulating NK-cell reactivity in the clinic. A greater understanding of iNKR and their ability to regulate NK cells will provide a basis for future attempts at translating their potential utility into benefits for human health.

Role of HCMV miR-UL70-3p and miR-UL148D in overcoming the cellular apoptosis

The studies into the pathophysiology of viral miRNAs are still in infancy; the interspecies regulation at the miRNA level fuels the spark of the investigation into the repertoire of virus-host interactions. Reports pertaining to the viral miRNAs role in modulating/evading the host immune response are surging up; we initiated this in silico study to speculate the role of human cytomegalovirus (HCMV)-encoded miRNAs on human antiviral mechanisms such as apoptosis and autophagy. The results indicate that both the above mechanisms were targeted by the HCMV miRNAs, located in the unique long region of the HCMV genome. The proapoptotic genes MOAP1, PHAP, and ERN1 are identified to be the potential targets for the miR-UL70-3p and UL148D, respectively. The ERN1 gene plays a role in the initiation of Endoplasmic reticulum stress-induced apoptosis as well as autophagosome formation. This study shows that HCMV employs its miRNA repertoire for countering the cellular apoptosis and autophagy, particularly the mitochondrial-dependent intrinsic pathway of apoptosis. In addition, the homology studies reveal no HCMV miRNA bears sequence homology with human miRNAs.

Immunological visibility: posttranscriptional regulation of human NKG2D ligands by the EGF receptor pathway

Human cytolytic T lymphocytes and natural killer cells can limit tumor growth and are being increasingly harnessed for tumor immunotherapy. One way cytolytic lymphocytes recognize tumor cells is by engagement of their activating receptor, NKG2D, by stress antigens of the MICA/B and ULBP families. This study shows that surface up-regulation of NKG2D ligands by human epithelial cells in response to ultraviolet irradiation, osmotic shock, oxidative stress, and growth factor provision is attributable to activation of the epidermal growth factor receptor (EGFR). EGFR activation causes intracellular relocalization of AUF1 proteins that ordinarily destabilize NKG2D ligand mRNAs by targeting an AU-rich element conserved within the 3' ends of most human, but not murine, NKG2D ligand genes. Consistent with these findings, NKG2D ligand expression by primary human carcinomas positively correlated with EGFR expression, which is commonly hyperactivated in such tumors, and was reduced by clinical EGFR inhibitors. Therefore, stress-induced activation of EGFR not only regulates cell growth but also concomitantly regulates the cells' immunological visibility. Thus, therapeutics designed to limit cancer cell growth should also be considered in terms of their impact on immunosurveillance.

MicroRNAs as potential circulating biomarkers of drug-induced liver injury: key current and future issues for translation to humans

Drug-induced liver injury (DILI) is a common form of adverse drug reaction seen within the clinic. Sensitive, specific and non-invasive biomarkers of liver toxicity are required to help diagnose hepatotoxicity and also to identify safety liabilities during drug development. Limitations exist in the current gold standard DILI biomarkers: alanine aminotransferase is not liver-specific and therefore gives rise to false-positive signals. Interest has grown in the potential of microRNAs (miRNAs) as biomarkers of DILI. Some miRNAs display remarkable organ specificity, can be measured sensitively and are stable in a wide range of biofluids. However, little is currently known about the mechanisms through which miRNAs are released from cells. Furthermore, a clinically suitable method to measure miRNAs has not yet been developed. This review aims to highlight the current research surrounding these markers and areas in which further work is required to establish these markers within clinical and pre-clinical settings.

Potential regulatory role of microRNAs in the development of bovine gastrointestinal tract during early life

This study aimed to investigate the potential regulatory role of miRNAs in the development of gastrointestinal tract (GIT) during the early life of dairy calves. Rumen and small intestinal (mid-jejunum and ileum) tissue samples were collected from newborn (30 min after birth; n = 3), 7-day-old (n = 6), 21-day-old (n = 6), and 42-day-old (n = 6) dairy calves. The miRNA profiling was performed using Illumina RNA-sequencing and the temporal and regional differentially expressed miRNAs were further validated using qRT-PCR. Analysis of 16S rRNA gene copy numbers was used to quantify total bacteria, Bifidobacterium and Lactobacillus species. The expression of miR-143 was abundant in all three gut regions, at all time points and it targets genes involved primarily in the proliferation of connective tissue cells and muscle cells, suggesting a role in regulating rapid tissue development during the early life of calves. The expression of miR-146, miR-191, miR-33, miR-7, miR-99/100, miR-486, miR-145, miR-196 and miR-211 displayed significant temporal differences (FDR <0.05), while miR-192/215, miR-194, miR-196, miR-205 and miR-31 revealed significant regional differences (FDR <0.05). The expression levels of miR-15/16, miR-29 and miR-196 were positively correlated with the copy numbers of 16S rRNA gene of Bifidobacterium or Lactobacillus species or both (P<0.05). Functional analysis using Ingenuity Pathway Analysis identified the above mentioned differentially expressed miRNAs as potential regulators of gut tissue cell proliferation and differentiation. The bacterial density-associated miRNAs were identified as modulators of the development of lymphoid tissues (miR-196), maturation of dendritic cells (miR-29) and development of immune cells (miR-15/16). The present study revealed temporal and regional changes in miRNA expression and a correlation between miRNA expression and microbial population in the GIT during the early life, which provides further evidence for another mechanism by which host-microbial interactions play a role in regulating gut development.

A day in the life of the spliceosome

One of the most amazing findings in molecular biology was the discovery that eukaryotic genes are discontinuous, with coding DNA being interrupted by stretches of non-coding sequence. The subsequent realization that the intervening regions are removed from pre-mRNA transcripts via the activity of a common set of small nuclear RNAs (snRNAs), which assemble together with associated proteins into a complex known as the spliceosome, was equally surprising. How do cells coordinate the assembly of this molecular machine? And how does the spliceosome accurately recognize exons and introns to carry out the splicing reaction? Insights into these questions have been gained by studying the life cycle of spliceosomal snRNAs from their transcription, nuclear export and re-import to their dynamic assembly into the spliceosome. This assembly process can also affect the regulation of alternative splicing and has implications for human disease.

Intestinal epithelial barrier disruption through altered mucosal microRNA expression in human immunodeficiency virus and simian immunodeficiency virus infections

Epithelial barrier dysfunction during human immunodeficiency virus (HIV) infection has largely been attributed to the rapid and severe depletion of CD4(+) T cells in the gastrointestinal (GI) tract. Although it is known that changes in mucosal gene expression contribute to intestinal enteropathy, the role of small noncoding RNAs, specifically microRNA (miRNA), has not been investigated. Using the simian immunodeficiency virus (SIV)-infected nonhuman primate model of HIV pathogenesis, we investigated the effect of viral infection on miRNA expression in intestinal mucosa. SIV infection led to a striking decrease in the expression of mucosal miRNA compared to that in uninfected controls. This decrease coincided with an increase in 5'-3'-exoribonuclease 2 protein and alterations in DICER1 and Argonaute 2 expression. Targets of depleted miRNA belonged to molecular pathways involved in epithelial proliferation, differentiation, and immune response. Decreased expression of several miRNA involved in maintaining epithelial homeostasis in the gut was localized to the proliferative crypt region of the intestinal epithelium. Our findings suggest that SIV-induced decreased expression of miRNA involved in epithelial homeostasis, disrupted expression of miRNA biogenesis machinery, and increased expression of XRN2 are involved in the development of epithelial barrier dysfunction and gastroenteropathy.

IMPORTANCE

MicroRNA (miRNA) regulate the development and function of intestinal epithelial cells, and many viruses disrupt normal host miRNA expression. In this study, we demonstrate that SIV and HIV disrupt expression of miRNA in the small intestine during infection. The depletion of several key miRNA is localized to the proliferative crypt region of the gut epithelium. These miRNA are known to control expression of genes involved in inflammation, cell death, and epithelial maturation. Our data indicate that this disruption might be caused by altered expression of miRNA biogenesis machinery during infection. These findings suggest that the disruption of miRNA in the small intestine likely plays a role in intestinal enteropathy during HIV infection.

microRNAs of parasitic helminths - Identification, characterization and potential as drug targets

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Importance of microRNAs in helminth post-transcriptional gene regulation is reviewed.

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Increasing helminth miRNA data are available from deep sequencing.

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Some miRNAs are helminth-specific, many are novel to each species.

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miRNAs may regulate parasite and host gene expression.

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Uptake of miRNA inhibitors and mimics is feasible for functional analysis.

microRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional gene regulation. They were first identified in the free-living nematode Caenorhabditis elegans, where the miRNAs lin-4 and let-7 were shown to be essential for regulating correct developmental progression. The sequence of let-7 was subsequently found to be conserved in higher organisms and changes in expression of let-7, as well as other miRNAs, are associated with certain cancers, indicating important regulatory roles. Some miRNAs have been shown to have essential functions, but the roles of many are currently unknown. With the increasing availability of genome sequence data, miRNAs have now been identified from a number of parasitic helminths, by deep sequencing of small RNA libraries and bioinformatic approaches. While some miRNAs are widely conserved in a range of organisms, others are helminth-specific and many are novel to each species. Here we review the potential roles of miRNAs in regulating helminth development, in interacting with the host environment and in development of drug resistance. Use of fluorescently-labeled small RNAs demonstrates uptake by parasites, at least in vitro. Therefore delivery of miRNA inhibitors or mimics has potential to alter miRNA activity, providing a useful tool for probing the roles of miRNAs and suggesting novel routes to therapeutics for parasite control.

Molecular Bases for the Regulation of NKG2D Ligands in Cancer

NKG2D is an activating receptor expressed by NK and T cells primarily involved in the elimination of transformed and infected cells. NKG2D ligands are self-proteins restrictedly expressed in healthy tissues, but induced in response to signaling pathways commonly associated with transformation. Proliferative, tumor suppressor, and stress signaling pathways linked to the tumorigenic process induce the expression of NKG2D ligands, initiating an immune response against the incipient tumor. Nevertheless, the activity of NKG2D ligands is counter-regulated in vivo by the immunoediting of cancer cells, resulting in the expression of multiple mechanisms of immune evasion in advanced tumors. The redundancy of NKG2D ligands, besides increasing the complexity of their regulation, may impair the generation of these immune evasion mechanisms. In this review, we attempt to integrate the mechanisms and pathways involved in the regulation of NKG2D ligand expression in cancer.

Proteins associated with SF3a60 in T. brucei

Trypanosoma brucei relies on Spliced leader trans splicing to generate functional messenger RNAs. Trans splicing joins the specialized SL exon from the SL RNA to pre-mRNAs and is mediated by the trans-spliceosome, which is made up of small nuclear ribonucleoprotein particles and non-snRNP factors. Although the trans spliceosome is essential for trypanosomatid gene expression, not all spliceosomal protein factors are known and of these, only a few are completely characterized. In this study, we have characterized the trypanosome Splicing Factor, SF3a60, the only currently annotated SF3a component. As expected, epitope-tagged SF3a60 localizes in the trypanosome nucleus. SF3a60 is essential for cell viability but its depletion seem to have no detectable effect on trans-splicing. In addition, we used SF3a60 as bait in a Yeast-2-hybrid system screen and identified its interacting protein factors. The interactions with SF3a120, SF3a66 and SAP130 were confirmed by tandem affinity purification and mass spectrometry.

Immunobiology and conflicting roles of the human NKG2D lymphocyte receptor and its ligands in cancer

Cancers adopt diverse strategies to safeguard their survival, which often involve blinding or incapacitating the immune response, thereby gaining battleground advantage against the host. In immune responses against cancer, an important stimulatory lymphocyte receptor is NKG2D because the tumor-associated expression of its ligands promotes destruction of malignant cells. However, with advanced human cancers profound changes unfold wherein NKG2D and its ligands are targeted or exploited for immune evasion and suppression. This negative imprinting on the immune system may be accompanied by another functional state wherein cancer cells coopt expression of NKG2D to complement the presence of its ligands for self-stimulation of tumor growth and presumably malignant progression. This review emphasizes these conflicting functional dynamics at the immunity-cancer biology interface in humans, within an overview of the immunobiology of NKG2D and mechanisms underlying the regulation of its ligands in cancer, with reference to instructive clinical observations and translational approaches.

Obesity and cancer: a gut microbial connection

Multiple epidemiological studies have revealed that excess bodyweight, such as in people who are overweight or obese (defined by a body mass index higher than 25 kg/m(2)), is a major risk factor for not only diabetes and cardiovascular diseases but also cancer. Effective strategies for obesity prevention are therefore needed for cancer prevention. However, because the prevalence of excess bodyweight in most developed countries has been increasing markedly over the past several decades, with no signs of abating, alternative approaches are also required to conquer obesity-associated cancer. Therefore, we sought to understand the molecular mechanisms underlying obesity-associated cancer. Although several phenomena have been proposed to explain how obesity increases cancer risk, the exact molecular mechanisms that integrate these phenomena have remained largely obscure. Recently, we have traced the association between obesity and increased cancer risk to gut microbiota communities that produce a DNA-damaging bile acid. The analyses also revealed the role of cellular senescence in cancer, which we have been studying for the past few decades. In this review, we provide an overview of our work and discuss the next steps, focusing on the potential clinical implications of these findings.

A novel HIV-1-encoded microRNA enhances its viral replication by targeting the TATA box region

Background

A lot of microRNAs (miRNAs) derived from viral genomes have been identified. Many of them play various important roles in virus replication and virus-host interaction. Cellular miRNAs have been shown to participate in the regulation of HIV-1 viral replication, while the role of viral-encoded miRNAs in this process is largely unknown.

Results

In this report, through a strategy combining computational prediction and deep sequencing, we identified a novel HIV-1-encoded miRNA, miR-H3. MiR-H3 locates in the mRNA region encoding the active center of reverse transcriptase (RT) and exhibits high sequence conservation among different subtypes of HIV-1 viruses. Overexpression of miR-H3 increases viral production and the mutations in miR-H3 sequence significantly impair the viral replication of wildtype HIV-1 viruses, suggesting that it is a replication-enhancing miRNA. MiR-H3 upregulates HIV-1 RNA transcription and protein expression. A serial deletion assay suggests that miR-H3 targets HIV-1 5′ LTR and upregulates the promoter activity. It interacts with the TATA box in HIV-1 5′ LTR and sequence-specifically activates the viral transcription. In addition, chemically-synthesized small RNAs targeting HIV-1 TATA box activate HIV-1 production from resting CD4⁺ T cells isolated from HIV-1-infected patients on suppressive highly active antiretroviral therapy (HAART).

Conclusions

We have identified a novel HIV-1-encoded miRNA which specifically enhances viral production and provide a specific method to activate HIV-1 latency.

Non-coding RNAs turn up the heat: an emerging layer of novel regulators in the mammalian heat shock response

The field of non-coding RNA (ncRNA) has expanded over the last decade following the discoveries of several new classes of regulatory ncRNA. A growing amount of evidence now indicates that ncRNAs are involved even in the most fundamental of cellular processes. The heat shock response is no exception as ncRNAs are being identified as integral components of this process. Although this area of research is only in its infancy, this article focuses on several classes of regulatory ncRNA (i.e., miRNA, lncRNA, and circRNA), while summarizing their activities in mammalian heat shock. We also present an updated model integrating the traditional heat shock response with the activities of regulatory ncRNA. Our model expands on the mechanisms for efficient execution of the stress response, while offering a more comprehensive summary of the major regulators and responders in heat shock signaling. It is our hope that much of what is discussed herein may help researchers in integrating the fields of heat shock and ncRNA in mammals.

The structure of cytomegalovirus immune modulator UL141 highlights structural Ig-fold versatility for receptor binding

Natural killer (NK) cells are critical components of the innate immune system as they rapidly detect and destroy infected cells. To avoid immune recognition and to allow long-term persistence in the host, Human cytomegalovirus (HCMV) has evolved a number of genes to evade or inhibit immune effector pathways. In particular, UL141 can inhibit cell-surface expression of both the NK cell-activating ligand CD155 as well as the TRAIL death receptors (TRAIL-R1 and TRAIL-R2). The crystal structure of unliganded HCMV UL141 refined to 3.25 Å resolution allowed analysis of its head-to-tail dimerization interface. A `dimerization-deficient' mutant of UL141 (ddUL141) was further designed, which retained the ability to bind to TRAIL-R2 or CD155 while losing the ability to cross-link two receptor monomers. Structural comparison of unliganded UL141 with UL141 bound to TRAIL-R2 further identified a mobile loop that makes intimate contacts with TRAIL-R2 upon receptor engagement. Superposition of the Ig-like domain of UL141 on the CD155 ligand T-cell immunoreceptor with Ig and ITIM domains (TIGIT) revealed that UL141 can potentially engage CD155 similar to TIGIT by using the C'C'' and GF loops. Further mutations in the TIGIT binding site of CD155 (Q63R and F128R) abrogated UL141 binding, suggesting that the Ig-like domain of UL141 is a viral mimic of TIGIT, as it targets the same binding site on CD155 using similar `lock-and-key' interactions. Sequence alignment of the UL141 gene and its orthologues also showed conservation in this highly hydrophobic (L/A)X6G `lock' motif for CD155 binding as well as conservation of the TRAIL-R2 binding patches, suggesting that these host-receptor interactions are evolutionary conserved.

MicroRNA editing facilitates immune elimination of HCMV infected cells

The human cytomegalovirus (HCMV) is extremely prevalent in the human population. Infection by HCMV is life threatening in immune compromised individuals and in immune competent individuals it can cause severe birth defects, developmental retardation and is even associated with tumor development. While numerous mechanisms were developed by HCMV to interfere with immune cell activity, much less is known about cellular mechanisms that operate in response to HCMV infection. Here we demonstrate that in response to HCMV infection, the expression of the short form of the RNA editing enzyme ADAR1 (ADAR1-p110) is induced. We identified the specific promoter region responsible for this induction and we show that ADAR1-p110 can edit miR-376a. Accordingly, we demonstrate that the levels of the edited-miR-376a (miR-376a(e)) increase during HCMV infection. Importantly, we show that miR-376a(e) downregulates the immune modulating molecule HLA-E and that this consequently renders HCMV infected cells susceptible to elimination by NK cells.

Influenza virus uses its neuraminidase protein to evade the recognition of two activating NK cell receptors

Natural Killer (NK) cells play a central role in the defense against viral infections and in the elimination of transformed cells. The recognition of pathogen-infected and tumor cells is controlled by inhibitory and activating receptors. We have previously shown that among the activating (killer) NK cell receptors the natural cytotoxicity receptors, NKp44 and NKp46, interact with the viral hemagglutinin (HA) protein expressed on the cell surface of influenza-virus-infected cells. We further showed that the interaction between NKp44/NKp46 and viral HA is sialic-acid dependent and that the recognition of HA by NKp44 and NKp46 leads to the elimination of the infected cells. Here we demonstrate that the influenza virus developed a counter-attack mechanism and that the virus uses its neuraminidase (NA) protein to prevent the recognition of HA by both the NKp44 and NKp46 receptors, resulting in reduced elimination of the infected cells by NK cells.

Time-dependent expression profiles of microRNAs and mRNAs in rat milk whey

Functional RNAs, such as microRNA (miRNA) and mRNA, are present in milk, but their roles are unknown. To clarify the roles of milk RNAs, further studies using experimental animals such as rats are needed. However, it is unclear whether rat milk also contains functional RNAs and what their time dependent expression profiles are. Thus, we prepared total RNA from whey isolated from rat milk collected on days 2, 9, and 16 postpartum and analyzed using microarrays and quantitative PCR. The concentration of RNA in colostrum whey (day 2) was markedly higher than that in mature milk whey (days 9 and 16). Microarray analysis detected 161 miRNAs and 10,948 mRNA transcripts. Most of the miRNAs and mRNA transcripts were common to all tested milks. Finally, we selected some immune- and development-related miRNAs and mRNAs, and analysed them by quantitative PCR (in equal sample volumes) to determine their time-dependent changes in expression in detail. Some were significantly more highly expressed in colostrum whey than in mature milk whey, but some were expressed equally. And mRNA expression levels of some cytokines and hormones did not reflect the protein levels. It is still unknown whether RNAs in milk play biological roles in neonates. However, our data will help guide future in vivo studies using experimental animals such as rats.

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.

Advances in NKG2D ligand recognition and responses by NK cells

The natural killer (NK) group 2 member D (NKG2D) is an activating immune receptor expressed on NK cells, cytotoxic T cells and a subset of other T cells. It has an important role in the recognition and lysis of a variety of infected and tumor cells. Despite significant gains in our understanding of NKG2D, the relevance of NKG2D and its ligands in human diseases has only recently started to emerge. Here, we present an overview of the recent advances in NKG2D biology, discuss the expression of NKG2D ligands in cancer patients and evaluate the diagnostic and prognostic potential of NKG2D ligands.

Downregulation of microRNA-107 in intestinal CD11c(+) myeloid cells in response to microbiota and proinflammatory cytokines increases IL-23p19 expression

Commensal flora plays an important role in the development of the mucosal immune system and in maintaining intestinal homeostasis. However, the mechanisms involved in regulation of host-microbiota interaction are still not completely understood. In this study, we examined how microbiota and intestinal inflammatory conditions regulate host microRNA expression and observed lower microRNA-107 (miR-107) expression in the inflamed intestines of colitic mice, compared with that in normal control mice. miR-107 was predominantly reduced in epithelial cells and CD11c(+) myeloid cells including dendritic cells and macrophages in the inflamed intestines. We demonstrate that IL-6, IFN-γ, and TNF-α downregulated, whereas TGF-β promoted, miR-107 expression. In addition, miR-107 expression was higher in the intestines of germ-free mice than in mice housed under specific pathogen-free conditions, and the presence of microbiota downregulated miR-107 expression in DCs and macrophages in a MyD88- and NF-κB-dependent manner. We determined that the ectopic expression of miR-107 specifically repressed the expression of IL-23p19, a key molecule in innate immune responses to commensal bacteria. We concluded that regulation of miR-107 by intestinal microbiota and proinflammatory cytokine serve as an important pathway for maintaining intestinal homeostasis.

Interplay between DNA repair and inflammation, and the link to cancer

DNA damage and repair are linked to cancer. DNA damage that is induced endogenously or from exogenous sources has the potential to result in mutations and genomic instability if not properly repaired, eventually leading to cancer. Inflammation is also linked to cancer. Reactive oxygen and nitrogen species (RONs) produced by inflammatory cells at sites of infection can induce DNA damage. RONs can also amplify inflammatory responses, leading to increased DNA damage. Here, we focus on the links between DNA damage, repair, and inflammation, as they relate to cancer. We examine the interplay between chronic inflammation, DNA damage and repair and review recent findings in this rapidly emerging field, including the links between DNA damage and the innate immune system, and the roles of inflammation in altering the microbiome, which subsequently leads to the induction of DNA damage in the colon. Mouse models of defective DNA repair and inflammatory control are extensively reviewed, including treatment of mouse models with pathogens, which leads to DNA damage. The roles of microRNAs in regulating inflammation and DNA repair are discussed. Importantly, DNA repair and inflammation are linked in many important ways, and in some cases balance each other to maintain homeostasis. The failure to repair DNA damage or to control inflammatory responses has the potential to lead to cancer.

Ocular adnexal non-Hodgkin's lymphoma: a review of epidemiology and risk factors

Ocular adnexal non-Hodgkin's lymphoma (NHL), the most common form of ophthalmic NHL, has a unique incidence pattern showing a steady and rapid increase in the past few decades, nearly equal rates among both genders, and predominance among Asians/Pacific Islanders. No major cause for ocular adnexal NHL has been identified, although infectious agents, immune disorders and genetic/epigenetic factors have all been implicated in its etiology. Identifying putative risk factors and biologic mechanisms leading to carcinogenesis in ocular adnexal NHL may enable implementation of effective preventive and/or therapeutic approaches for this malignancy. This article summarizes current knowledge on epidemiology of ocular adnexal NHL and the role of various potential risk factors in its etiology.

Human cytomegalovirus suppresses Fas expression and function

Human cytomegalovirus (HCMV) is known to evade extrinsic pro-apoptotic pathways not only by downregulating cell surface expression of the death receptors TNFR1, TRAIL receptor 1 (TNFRSF10A) and TRAIL receptor 2 (TNFRSF10B), but also by impeding downstream signalling events. Fas (CD95/APO-1/TNFRSF6) also plays a prominent role in apoptotic clearance of virus-infected cells, so its fate in HCMV-infected cells needs to be addressed. Here, we show that cell surface expression of Fas was suppressed in HCMV-infected fibroblasts from 24 h onwards through the late phase of productive infection, and was dependent on de novo virus-encoded gene expression but not virus DNA replication. Significant levels of the fully glycosylated (endoglycosidase-H-resistant) Fas were retained within HCMV-infected cells throughout the infection within intracellular membranous structures. HCMV infection provided cells with a high level of protection against Fas-mediated apoptosis. Downregulation of Fas was observed with HCMV strains AD169, FIX, Merlin and TB40.

Viral microRNAs targeting virus genes promote virus infection in shrimp in vivo

Viral microRNAs (miRNAs), most of which are characterized in cell lines, have been found to play important roles in the virus life cycle to avoid attack by the host immune system or to keep virus in the latency state. Viral miRNAs targeting virus genes can inhibit virus infection. In this study, in vivo findings in Marsupenaeus japonicus shrimp revealed that the viral miRNAs could target virus genes and further promote the virus infection. The results showed that white spot syndrome virus (WSSV)-encoded miRNAs WSSV-miR-66 and WSSV-miR-68 were transcribed at the early stage of WSSV infection. When the expression of WSSV-miR-66 and WSSV-miR-68 was silenced with sequence-specific anti-miRNA oligonucleotides (AMOs), the number of copies of WSSV and the WSSV-infected shrimp mortality were significantly decreased, indicating that the two viral miRNAs had a great effect on virus infection. It was revealed that the WSSV wsv094 and wsv177 genes were the targets of WSSV-miR-66 and that the wsv248 and wsv309 genes were the targets of WSSV-miR-68. The data demonstrate that the four target genes play negative roles in the WSSV infection. The targeting of the four virus genes by WSSV-miR-66 and WSSV-miR-68 led to the promotion of virus infection. Therefore, our in vivo findings show a novel aspect of viral miRNAs in virus-host interactions.

miR146a impairs the IFN-induced anti-HBV immune response by downregulating STAT1 in hepatocytes

BACKGROUND & AIMS

Previous studies have shown that hepatitis B virus (HBV) interferes with host antiviral immunity via multiple pathways. In clinical practice, interferon resistance is a serious issue for treatment of HBV infection. Now, miRNAs have been reported to be widely involved in antiviral immunity and have become a novel tool to study virus-host interaction. We question whether miRNAs play a role in HBV-induced interferon resistance in hepatocytes.

METHODS

MiRNAs levels in HepG2 and HepG2.2.15 cells were compared by qRT-PCR. The effects of miR146a on HBV infection were characterized by interference miR146a level, followed by the quantification of HBV mRNA, DNA and antigens. We employed qRT-PCR and western blot to study the effects of miR146a on the IFN-α signalling pathway. The miR146a promoter activity was validated by a luciferase reporter assay.

RESULTS

HBV infection impaired IFN-α signalling pathway in hepatocytes. MiR146a was upregulated in HBV+ HepG2.2.15 cells, and the transcriptional activity of miR146a in HepG2.2.15 cells was increased compared with HepG2 cells. HBV infection, especially the introduction of HBx, induced miR146a expression in vitro. Moreover, miR146a attenuated the production of type I interferon-induced antiviral factors. Low STAT1 levels were noticed in HBV+ HCC cells, and the luciferase reporter assay showed that STAT1 was post-transcriptionally downregulated by miR146a. Furthermore, the silencing of miR146a by antisense inhibitors enhanced IFN-α-mediated anti-HBV efficiency.

CONCLUSIONS

Our findings demonstrate that HBV infection promotes miR146a transcription, which represses STAT1 and results in interferon resistance. These observations reveal a novel role for miR146a in HBV immunopathogenesis, and provide a potential target for the therapeutic recovery of IFN-α-induced anti-HBV effects.

Molecular biology of human herpesvirus 8: novel functions and virus-host interactions implicated in viral pathogenesis and replication

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus (KSHV), is the second identified human gammaherpesvirus. Like its relative Epstein-Barr virus, HHV-8 is linked to B-cell tumors, specifically primary effusion lymphoma and multicentric Castleman's disease, in addition to endothelial-derived KS. HHV-8 is unusual in its possession of a plethora of "accessory" genes and encoded proteins in addition to the core, conserved herpesvirus and gammaherpesvirus genes that are necessary for basic biological functions of these viruses. The HHV-8 accessory proteins specify not only activities deducible from their cellular protein homologies but also novel, unsuspected activities that have revealed new mechanisms of virus-host interaction that serve virus replication or latency and may contribute to the development and progression of virus-associated neoplasia. These proteins include viral interleukin-6 (vIL-6), viral chemokines (vCCLs), viral G protein-coupled receptor (vGPCR), viral interferon regulatory factors (vIRFs), and viral antiapoptotic proteins homologous to FLICE (FADD-like IL-1β converting enzyme)-inhibitory protein (FLIP) and survivin. Other HHV-8 proteins, such as signaling membrane receptors encoded by open reading frames K1 and K15, also interact with host mechanisms in unique ways and have been implicated in viral pathogenesis. Additionally, a set of micro-RNAs encoded by HHV-8 appear to modulate expression of multiple host proteins to provide conditions conducive to virus persistence within the host and could also contribute to HHV-8-induced neoplasia. Here, we review the molecular biology underlying these novel virus-host interactions and their potential roles in both virus biology and virus-associated disease.

Systematic microRNA analysis identifies ATP6V0C as an essential host factor for human cytomegalovirus replication

Recent advances in microRNA target identification have greatly increased the number of putative targets of viral microRNAs. However, it is still unclear whether all targets identified are biologically relevant. Here, we use a combined approach of RISC immunoprecipitation and focused siRNA screening to identify targets of HCMV encoded human cytomegalovirus that play an important role in the biology of the virus. Using both a laboratory and clinical strain of human cytomegalovirus, we identify over 200 putative targets of human cytomegalovirus microRNAs following infection of fibroblast cells. By comparing RISC-IP profiles of miRNA knockout viruses, we have resolved specific interactions between human cytomegalovirus miRNAs and the top candidate target transcripts and validated regulation by western blot analysis and luciferase assay. Crucially we demonstrate that miRNA target genes play important roles in the biology of human cytomegalovirus as siRNA knockdown results in marked effects on virus replication. The most striking phenotype followed knockdown of the top target ATP6V0C, which is required for endosomal acidification. siRNA knockdown of ATP6V0C resulted in almost complete loss of infectious virus production, suggesting that an HCMV microRNA targets a crucial cellular factor required for virus replication. This study greatly increases the number of identified targets of human cytomegalovirus microRNAs and demonstrates the effective use of combined miRNA target identification and focused siRNA screening for identifying novel host virus interactions.

Human cytomegalovirus is a prevalent pathogen. Like other herpesviruses, human cytomegalovirus expresses small regulatory RNAs called microRNAs. The focus of this study was to understand the role of these RNAs in the context of viral infection and to use this information to identify novel host factors involved in human cytomegalovirus biology. We used a biochemical approach that allowed us to systematically identify cellular genes targeted by virus microRNAs. Because the virus targets these genes, it is reasonable to propose that these genes play an important role during infection. We confirmed this hypothesis using a second screen in which we knocked down expression of a number of the identified targets of the virus microRNAs. Knock down of one of the targets, a cellular factor called ATP6V0C, resulted in an almost complete block in production of infectious virus. These data suggest that endosomal acidification is crucial to HCMV replication, and the virus targets this process by microRNA regulation.

The critical role of the tumor microenvironment in shaping natural killer cell-mediated anti-tumor immunity

Considerable evidence has been gathered over the last 10 years showing that the tumor microenvironment (TME) is not simply a passive recipient of immune cells, but an active participant in the establishment of immunosuppressive conditions. It is now well documented that hypoxia, within the TME, affects the functions of immune effectors including natural killer (NK) cells by multiple overlapping mechanisms. Indeed, each cell in the TME, irrespective of its transformation status, has the capacity to adapt to the hostile TME and produce immune modulatory signals or mediators affecting the function of immune cells either directly or through the stimulation of other cells present in the tumor site. This observation has led to intense research efforts focused mainly on tumor-derived factors. Notably, it has become increasingly clear that tumor cells secrete a number of environmental factors such as cytokines, growth factors, exosomes, and microRNAs impacting the immune cell response. Moreover, tumor cells in hostile microenvironments may activate their own intrinsic resistance mechanisms, such as autophagy, to escape the effective immune response. Such adaptive mechanisms may also include the ability of tumor cells to modify their metabolism and release several metabolites to impair the function of immune cells. In this review, we summarize the different mechanisms involved in the TME that affect the anti-tumor immune function of NK cells.

Human cytomegalovirus latent infection alters the expression of cellular and viral microRNA

BACKGROUND

MicroRNAs (miRNAs) play important roles in regulating gene expression of plants, animals and viruses. Comprehensive characterization of host and viral miRNA will help uncover the molecular mechanisms that underlie the progression of human cytomegalovirus (HCMV) latent infection. To investigate the miRNA expression profile of HCMV and host cells during latent infection, we performed deep-sequencing analysis of the small RNAs isolated from HCMV-infected and mock-infected human monocytic leukemia cell line, THP-1.

RESULTS

We established a HCMV latent infection cell model using the THP-1 cells. High-throughput sequencing technology was used to sequence small RNA libraries of the HCMV-infected and mock-infected THP-1 and to investigate their small RNA transcriptomes. We found eight miRNAs including miR-US25-1, miR-US25-2-5p and miR-UL112 that were expressed by HCMV during latent infection. The expressions of the host miRNAs were also affected by HCMV latent infection. At least 49 cellular miRNAs were differentially expressed: 39 were up-regulated and 10 were down-regulated upon HCMV latent infection. The expression of the human miRNA hsa-miR-124-3p was significantly up-regulated in the HCMV latent infection library. In addition, we found 14 cellular novel miRNAs in the HCMV-infected and mock-infected THP-1 libraries. Functional annotation of the target genes of the differentially expressed miRNAs suggested that the majority of the genes are involved in melanogenesis, pathways in cancer, endocytosis and wnt signaling pathway.

CONCLUSIONS

The small RNA transcriptomes obtained in this study demonstrate the usefulness of the deep-sequencing combined with bioinformatics approach in understanding of the expression and function of host and viral small RNAs in HCMV latent infection. This approach can also be applied to the study of other kinds of viruses.

Involvement of viral microRNA in the regulation of antiviral apoptosis in shrimp

Viruses, in particular DNA viruses, generate microRNAs (miRNAs) to control the expression of host and viral genes. Due to their essential roles in virus-host interactions, viral miRNAs have attracted extensive investigations in recent years. To date, however, most studies on viral miRNAs have been conducted in cell lines. In this study, the viral miRNAs from white spot syndrome virus (WSSV) were characterized in shrimp in vivo. On the basis of our previous study and small RNA sequencing in this study, a total of 89 putative WSSV miRNAs were identified. As revealed by miRNA microarray analysis and Northern blotting, the expression of viral miRNAs was tissue specific in vivo. The results indicated that the viral miRNA WSSV-miR-N24 could target the shrimp caspase 8 gene, and this miRNA further repressed the apoptosis of shrimp hemocytes in vivo. As a result, the number of WSSV copies in shrimp in vivo was significantly increased compared with the control level (WSSV only). Therefore, our study presents the first report on the in vivo molecular events of viral miRNA in antiviral apoptosis.

Non-coding RNAs in homeostasis, disease and stress responses: an evolutionary perspective

Cells and organisms are subject to challenges and perturbations in their environment and physiology in all stages of life. The molecular response to such changes, including insulting conditions such as pathogen infections, involves coordinated modulation of gene expression programmes and has not only homeostatic but also ecological and evolutionary importance. Although attention has been primarily focused on signalling pathways and protein networks, non-coding RNAs (ncRNAs), which comprise a significant output of the genomes of prokaryotes and especially eukaryotes, are increasingly implicated in the molecular mechanisms of these responses. Long and short ncRNAs not only regulate development and cell physiology, they are also involved in disease states, including cancers, in host-pathogen interactions, and in a variety of stress responses. Indeed, regulatory RNAs are part of genetically encoded response networks and also underpin epigenetic processes, which are emerging as key mechanisms of adaptation and transgenerational inheritance. Here we present the growing evidence that ncRNAs are intrinsically involved in cellular and organismal adaptation processes, in both robustness and protection to stresses, as well as in mechanisms generating evolutionary change.

Cellular and molecular mechanisms in cancer immune escape: a comprehensive review

Immune escape is the final phase of cancer immunoediting process wherein cancer modulates our immune system to escape from being destroyed by it. Many cellular and molecular events govern the cancer's evasion of host immune response. The tumor undergoes continuous remodeling at the genetic, epigenetic and metabolic level to acquire resistance to apoptosis. At the same time, it effectively modifies all the components of the host's immunome so as to escape from its antitumor effects. Moreover, it induces accumulation of suppressive cells like Treg and myeloid derived suppressor cells and factors which also enable it to elude the immune system. Recent research in this area helps in defining the role of newer players like miRNAs and exosomes in immune escape. The immunotherapeutic approaches developed to target the escape phase appear quite promising; however, the quest for a perfect therapeutic agent that can achieve maximum cure with minimal toxicity continues.

The intestinal microbiota interferes with the microRNA response upon oral Listeria infection

The intestinal tract is the largest reservoir of microbes in the human body. The intestinal microbiota is thought to be able to modulate alterations of the gut induced by enteropathogens, thereby maintaining homeostasis. Listeria monocytogenes is the agent of listeriosis, an infection transmitted to humans upon ingestion of contaminated food. Crossing of the intestinal barrier is a critical step of the infection before dissemination into deeper organs. Here, we investigated the role of the intestinal microbiota in the regulation of host protein-coding genes and microRNA (miRNA or miR) expression during Listeria infection. We first established the intestinal miRNA signatures corresponding to the 10 most highly expressed miRNAs in the murine ileum of conventional and germfree mice, noninfected and infected with Listeria. Next, we identified 6 miRNAs whose expression decreased upon Listeria infection in conventional mice. Strikingly, five of these miRNA expression variations (in miR-143, miR-148a, miR-200b, miR-200c, and miR-378) were dependent on the presence of the microbiota. In addition, as is already known, protein-coding genes were highly affected by infection in both conventional and germfree mice. By crossing bioinformatically the predicted targets of the miRNAs to our whole-genome transcriptomic data, we revealed an miRNA-mRNA network that suggested miRNA-mediated global regulation during intestinal infection. Other recent studies have revealed an miRNA response to either bacterial pathogens or commensal bacteria. In contrast, our work provides an unprecedented insight into the impact of the intestinal microbiota on host transcriptional reprogramming during infection by a human pathogen.

While the crucial role of miRNAs in regulating the host response to bacterial infection is increasingly recognized, the involvement of the intestinal microbiota in the regulation of miRNA expression has not been explored in detail. Here, we investigated the impact of the intestinal microbiota on the regulation of protein-coding genes and miRNA expression in a host infected by L. monocytogenes, a food-borne pathogen. We show that the microbiota interferes with the microRNA response upon oral Listeria infection and identify several protein-coding target genes whose expression correlates inversely with that of the miRNA. Further investigations of the regulatory networks involving miR-143, miR-148a, miR-200b, miR-200c, and miR-378 will provide new insights into the impact of the intestinal microbiota on the host upon bacterial infection.

miR-homoHSV of Singapore grouper iridovirus (SGIV) inhibits expression of the SGIV pro-apoptotic factor LITAF and attenuates cell death

Growing evidence demonstrates that various large DNA viruses could encode microRNAs (miRNAs) that regulate host and viral genes to achieve immune evasion. In this study, we report that miR-homoHSV, an miRNA encoded by Singapore grouper iridovirus (SGIV), can attenuate SGIV-induced cell death. Mechanistically, SGIV miR-homoHSV targets SGIV ORF136R, a viral gene that encodes the pro-apoptotic lipopolysaccharide-induced TNF-α (LITAF)-like factor. miR-homoHSV suppressed exogenous and endogenous SGIV LITAF expression, and thus inhibited SGIV LITAF-induced apoptosis. Meanwhile, miR-homoHSV expression was able to attenuate cell death induced by viral infection, presumably facilitating viral replication through the down-regulation of the pro-apoptotic gene SGIV LITAF. Together, our data suggest miR-homoHSV may serve as a feedback regulator of cell death during viral infection. The findings of this study provide a better understanding of SGIV replication and pathogenesis.

Diagnostic and prognostic value of plasma microRNA deregulation in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is uncommon worldwide but often highly invasive in late stages. Due to its special location and lack of specific symptoms, NPC is hardly detected in regular medical examination at the beginning. Development of sensitive and specific biomarkers should help to save lives against this type of disease. In the present report, we investigated the value of plasma miRNAs for diagnosis and prognosis of NPC. Using candidate approach, we selected 21 miRNAs from literature to compare their expression levels in the plasma of NPC patients and controls. As a result, 5 miRNAs showed diagnostic potentials (P<0.01). Among them, miR-16, -21, -24, and -155 had increased levels in NPC patients, whereas the level of miR-378 was decreased. There was a negative correlation between plasma miRNA expression and cancer progression, where miR-21 was statistically significant in T and N staging and miR-16 and 24 were significant in N staging only. Combination of miR-16, -21, -24, -155, and -378 gives 87.7% of sensitivity and 82.0% of specificity for NPC diagnosis. Without miR-16, combination of the rest 4 miRNAs gives the same sensitivity but a slightly reduced specificity. After treatment, all 5 miRNAs were somewhat back to normal levels in patients without cancer recurrence but the prognostic value was not statistically significant. In conclusion, plasma miRNA expression is a useful biomarker for NPC diagnosis but not for its prognosis. More importantly, it is simple, effective, and non-invasive. Combination of several plasma miRNAs can increase both NPC diagnostic sensitivity and specificity.

MicroRNAs as tools to predict glucocorticoid response in inflammatory bowel diseases

In spite of the introduction in therapy of highly effective biological agents, glucocorticoids (GCs) are still employed to induce remission in moderate to severe inflammatory bowel diseases (IBD), but considerable inter-individual differences in their efficacy and side effects have been reported. The effectiveness of these drugs is indeed very variable and side effects, particularly severe in pediatric patients, are common and often unpredictable: the understanding of the complex gene regulation mediated by GCs could shed light on the causes of this variability. In this context, microRNAs (miRNAs) represent a new and promising field of research. miRNAs are small non-coding RNA molecules that suppress gene expression at post-transcriptional level, and are fine-tuning regulators of diverse biological processes, including the development and function of the immune system, apoptosis, metabolism and inflammation. Emerging data have implicated the deregulated expression of certain miRNA networks in the pathogenesis of autoimmune and inflammatory diseases, such as IBD. There is a great interest in the identification of the role of miRNAs in the modulation of pharmacological response; however, the association between miRNA and GC response in patients with IBD has not yet been evaluated in a prospective clinical study. The identification of miRNAs differently expressed as a consequence of GC treatment in comparison to diagnosis, represents an important innovative approach that could be translated into clinical practice. In this review we highlight the altered regulation of proteins involved in GC molecular mechanism by miRNAs, and their potential role as molecular markers useful for predicting in advance GC response.

MiRNA-296-3p-ICAM-1 axis promotes metastasis of prostate cancer by possible enhancing survival of natural killer cell-resistant circulating tumour cells

Natural killer (NK) cells are important in host to eliminate circulating tumour cells (CTCs) in turn preventing the development of tumour cells into metastasis but the mechanisms are very poorly defined. Here we find that the expression level of miR-296-3p is much lower in the non-metastatic human prostate cancer (PCa) cell line P69 than that in the highly metastatic cell line M12, which is derived from P69. We demonstrate that miR-296-3p directly targets and inhibits the expression of intercellular adhesion molecule 1 (ICAM-1) in the malignant M12. The data from clinical tissue microarrays also show that miR-296-3p is frequently upregulated and ICAM-1 is reversely downregulated in PCa. Interestingly, ectopic expression of miR-296-3p in P69 increases the tolerance to NK cells whereas knockdown of miR-296-3p in M12 reduces the resistance to NK cells, which both phenotypes can be rescued by re-expression or silencing of ICAM-1 in P69 and M12, respectively. These results are also manifested in vivo by the decrease in the incidence of pulmonary tumour metastasis exhibited by knockdown of miR-296-3p in M12 when injected into athymic nude mice via tail vein, and consistently down-expression of ICAM-1 reverses this to increase extravasation of CTCs into lungs. Above results suggest that this newly identified miR-296-3p-ICAM-1 axis has a pivotal role in mediating PCa metastasis by possible enhancing survival of NK cell-resistant CTC. Our findings provide novel potential targets for PCa therapy and prognosis.

MicroRNA expression aberration in Chinese patients with relapsing remitting multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease that is caused by an abnormal immune system that attacks the central nervous system. MicroRNAs (miRNAs) are known to play essential roles in the immune system. Most of the previous studies about miRNA dysregulation in MS have focused on European populations. In the present study, the miRNA expression profiles associated with Chinese MS patients are investigated. Here, human miRNA expression profiling experiments were performed on the peripheral blood mononuclear leukocytes from ten MS patients and ten healthy controls. Nine overexpressed and six underexpressed miRNAs were found. The 15 miRNAs were validated independently in a second cohort of 40 MS patients and 40 controls by real-time PCR; six miRNAs were significantly abnormally expressed, and principal component analysis of six miRNAs indicated that the MS patients could be clearly differentiated from the healthy controls based on the miRNA expression patterns. This study provided the indications of abnormal miRNA expression patterns in the peripheral blood mononuclear leukocytes of Chinese MS patients. The potential roles of these differentially expressed miRNAs as MS biomarker and in pathogenesis need to be investigated in future studies.

Guest list or black list: heritable small RNAs as immunogenic memories

Small RNA-mediated gene silencing plays a pivotal role in genome immunity by recognizing and eliminating viruses and transposons that may otherwise colonize the genome. However, individual genomic parasites are highly diverse and employ multiple immune-evasion techniques, making this silencing challenging. Here I review a new theory proposing that the integrity of the germline is maintained by transgenerationally transmitted RNA 'memories' that record ancestral gene expression patterns and delineate 'self' from 'foreign' sequences. To maintain such recollection, two tactics are employed in parallel: 'black listing' of invading nucleic acids and 'guest listing' of endogenous genes. Studies in several organisms have shown that this memorization is used by the next generation of small RNAs to act as 'inherited vaccines' that attack invading elements or as 'inherited licenses' that permit the transcription of autogenous sequences.