BIC and miR-155 are highly expressed in Hodgkin, primary mediastinal and diffuse large B cell lymphomas

Epstein-Barr virus modulates host cell microRNA-194 to promote IL-10 production and B lymphoma cell survival

Epstein-Barr virus (EBV) is a γ-herpesvirus that is linked to the development of posttransplant lymphoproliferative disorder (PTLD) in solid organ recipients. We previously demonstrated that EBV(+) B cell lymphoma cell lines isolated from patients with PTLD produce human IL-10 as an autocrine growth factor. However, little is known regarding IL-10 regulation in B cells. Here we show that EBV infection markedly alters the expression of host B cell microRNA, a class of small noncoding RNA that is an important regulator of transcriptional and posttranscriptional gene expression. Gene arrays reveal unique microRNA profiles in EBV(+) B cell lymphoma lines from patients with PTLD, compared to normal B cells or in vitro generated EBV(+) lymphoblastoid cell lines. We show that microRNA-194 expression is uniquely suppressed in EBV(+) B cell lines from PTLD patients and that the 3'untranslated region of IL-10 is targeted by microRNA-194. Overexpression of microRNA-194 attenuates IL-10 production and increases apoptosis of EBV(+) B cell lymphoma lines. Together, these data indicate that EBV co-opts the host B cell microRNA network and specifically suppresses microRNA-194 to override control of IL-10 expression. Thus, modulation of microRNA-194 may constitute a novel approach to inhibiting proliferation of EBV(+) B cell lymphomas in PTLD.

Does miRNA-155 Promote Cyclooxygenase-2 Expression in Cancer?

Preclinical Research MicroRNA (miR)-155 and cyclooxygenase (COX)-2 are both elevated in numerous cancers including colorectal cancer. MiR-155 enhances COX-2 expression and is an established regulator of epithelial-mesenchymal transition and inflammation. Inhibition of miR-155 or COX-2 exhibit similar negative effects on tumorigenicity. Thus, it is hypothesized that miR-155 may be a promising target for antagonizing COX-2 expression in colorectal and other cancers.

Five miRNAs considered as molecular targets for predicting neuroglioma

Neuroglioma is a complex neuroglial tumor involving dysregulation of many biological pathways at multiple levels. Here, we aim to screen differentially expressed miRNAs (DEMs) as well as the functions and pathways of their target genes in neuroglioma. miRNA high-throughput sequencing data were downloaded from The Cancer Genome Atlas (TCGA), and then the DEMs were subjected to perform principal component analysis (PCA) based on their expression values. Following that, Targetscan software was used to predict the target genes, and enrichment analysis and pathway annotation of these target genes were done by DAVID and KEGG, respectively. Finally, survival analysis between the DEMs and patients' survival time was done, and the miRNAs with prediction potential were obtained. A total of 33 DEMs were obtained, among which 25 miRNAs were upregulated including hsa-mir-675, hsa-mir-196a-1, and hsa-mir-196a-2, while eight miRNAs were downregulated including hsa-mir-1911, hsa-mir-1264, and hsa-mir-1298. Five miRNAs with diagnostic and preventive potentials were significantly correlated with survival time, including has-mir-155, has-mir-199b, has-mi-10a, has-mir-1274b, and has-mir-455. The target genes of miRNA identified in this study played important roles in tumor signaling pathways, and their detailed functions could be further studied so as to explore novel neuroglioma therapies.

Oncogenic microRNA-155 and its target PU.1: an integrative gene expression study in six of the most prevalent lymphomas

The transcription factor PU.1 and its inhibitory microRNA-155 (miR-155) are important regulators of B-cell differentiation. PU.1 downregulation coupled with oncogenic miR-155 upregulation has been reported in lymphoid malignancies; however, these data have not been studied across different subtypes in relation to clinical outcomes. We studied expression of miR-155 and PU.1 in the six most prevalent human B-cell lymphomas (n = 131) including aggressive (DLBCL, HL, MCL) and indolent (B-CLL/SLL, MZL, FL) types. Levels of miR-155 and PU.1 inversely correlated in DLBCL, B-CLL/SLL, and FL tumor tissues. In HL tissues, an exceptionally high level of miR-155 was found in patients with unfavorable responses to first-line therapy and those who had shorter survival times. PU.1 downregulation was noted in B-CLL/SLL samples positive for the adverse prognostic markers CD38 and ZAP-70. Upregulation of miR-155 and downregulation of PU.1 expression are integral aspects of lymphoma biology that could mark aggressive behavior of some, but not all, lymphoma types.

Small RNAs growing tall: miRNAs as drug targets in herpesvirus infections

Herpesviruses establish life-long latent infections. They can cause severe morbidity and significant mortality particularly in immunocompromised hosts. Several are associated with cancers. Most express large amounts of microRNAs during latent or lytic infection. There is increasing evidence that these small RNA molecules play important roles in many aspects of pathogenesis, including lytic and latent infections, immune evasion and tumorigenesis. Therapies targeting microRNAs have already successfully made it into clinics, for example, to treat hepatitis C virus (HCV) infection. In this review, we will focus on regulatory functions of herpesvirus miRNAs that may be suitable for antiviral intervention.

Genome-wide whole blood microRNAome and transcriptome analyses reveal miRNA-mRNA regulated host response to foodborne pathogen Salmonella infection in swine

To understand the role of miRNAs in regulating genes involved in host response to bacterial infection and shedding of foodborne pathogens, a systematic profiling of miRNAs and mRNAs from the whole blood of pigs upon Salmonella challenge was performed. A total of 62 miRNAs were differentially expressed post infection (false discovery rate <0.1). An integrative analysis of both the differentially expressed miRNAs and mRNAs using sequence-based miRNA target prediction and negative correlation of miRNA-mRNA profiles helped identify miRNA-mRNA networks that may potentially regulate host response to Salmonella infection. From these networks, miR-214 and miR-331-3p were identified as new candidates potentially associated with Salmonella infection. An miRNA seed sequence analysis suggested that these miRNAs regulate several critical immune-related genes including SLC11A1, PIGE-108A11.3 and VAV2. We showed that challenged pigs had reduced miR-214 expression and increased miR-331-3p expression in the whole blood. Furthermore, the expression of the proposed targets of miR-214 (SLC11A1 and PIGE-108A11.3) increased while that of the proposed target of miR-331-3p (VAV2) decreased following challenge (expression changes confirmed by in vitro assays). Based on these observations, we propose potential roles for miR-214 and miR-331-3p in regulation of immune responses to Salmonella infection.

MicroRNA expression in hepatitis C virus-related malignancies: A brief review

Not only is chronic hepatitis C virus (HCV) infection a major public health problem, but also it can cause hepatocellular carcinoma and, more rarely, non-Hodgkin’s lymphoma. These characteristics mean that HCV is the only virus infecting humans that is able to cause two different cancers. The fine pathogenetic and molecular mechanisms by which HCV induces these two malignancies are not completely clear. In the last decade, it has been shown that microRNAs (miRNAs), a class of 21-23-nucleotide molecules modulating post-transcriptional gene expression, make an important contribution to the pathogenesis of several cancers and are also considered highly promising biomarkers. Here, we briefly describe the current knowledge about microRNAs’ involvement in HCV-related molecular oncogenesis. We decided to focus our attention on studies fully conducted on ex vivo samples with this specific etiology, and on cultured cell lines partially or completely expressing the HCV genome. Some of the results reported in this review are controversial, possibly because of methodological issues, differences in sampling size and features, and ethnicity of patients. What is certain is that miRNAs play a remarkable role in regulating gene expression during oncogenetic processes and in viral infection. A clear understanding of their effects is fundamental to elucidating the mechanisms underlying virus-induced malignancies.

Delivery of miR-155 to retinal pigment epithelial cells mediated by Burkitt's lymphoma exosomes

Exosomes are extracellularly secreted vesicles ranging from 40 to 100 nm in diameter that are thought to play important roles in intercellular communication. Exosomes contain numerous proteins, RNA, and lipids that can affect the status of recipient cells under various pathological conditions. MicroRNAs (miRNAs) are small non-coding RNAs that play a major role in post-transcriptional gene silencing by interacting with the 3'-untranslated regions of target genes. Epstein-Barr virus (EBV) has been reported to induce sustained elevation of cellular miRNAs such as miR-155. We hypothesized that miRNAs delivered by exosomes might affect the angiogenesis of retinal pigment epithelial (RPE) cells. Here, we demonstrated that co-culture of EBV-positive Burkitt's lymphoma (BL) cells (Raji) with retinal pigment epithelial (ARPE-19) cells increased the level of miR-155 in recipient cells whereas no major difference was detected for co-culture with EBV-negative BL cells (Ramos). Isolated Raji exosomes increased transcriptional and translational levels of VEGF-A in ARPE-19 cells, which was reversely correlated with von Hippel-Lindau expression. A human umbilical vein endothelial cell tube formation assay showed that delivery of ectopic miR-155 rendered ARPE-19 cells proangiogenic. Our results demonstrate that sustained accumulation of miR-155 mediated by exosomes might affect remote recipient cells such as retinal pigment epithelial cells.

The Emerging Role of miRNAs in HTLV-1 Infection and ATLL Pathogenesis

Human T-cell leukemia virus (HTLV)-1 is a human retrovirus and the etiological agent of adult T-cell leukemia/lymphoma (ATLL), a fatal malignancy of CD4/CD25+ T lymphocytes. In recent years, cellular as well as virus-encoded microRNA (miRNA) have been shown to deregulate signaling pathways to favor virus life cycle. HTLV-1 does not encode miRNA, but several studies have demonstrated that cellular miRNA expression is affected in infected cells. Distinct mechanisms such as transcriptional, epigenetic or interference with miRNA processing machinery have been involved. This article reviews the current knowledge of the role of cellular microRNAs in virus infection, replication, immune escape and pathogenesis of HTLV-1.

Small RNA Detection by in Situ Hybridization Methods

Small noncoding RNAs perform multiple regulatory functions in cells, and their exogenous mimics are widely used in research and experimental therapies to interfere with target gene expression. MicroRNAs (miRNAs) are the most thoroughly investigated representatives of the small RNA family, which includes short interfering RNAs (siRNAs), PIWI-associated RNA (piRNAs), and others. Numerous methods have been adopted for the detection and characterization of small RNAs, which is challenging due to their short length and low level of expression. These include molecular biology methods such as real-time RT-PCR, northern blotting, hybridization to microarrays, cloning and sequencing, as well as single cell miRNA detection by microscopy with in situ hybridization (ISH). In this review, we focus on the ISH method, including its fluorescent version (FISH), and we present recent methodological advances that facilitated its successful adaptation for small RNA detection. We discuss relevant technical aspects as well as the advantages and limitations of ISH. We also refer to numerous applications of small RNA ISH in basic research and molecular diagnostics.

A novel semi-automated in situ hybridisation protocol for microRNA detection in paraffin embedded tissue sections

MicroRNAs (miRNAs) are small non-coding RNAs that modulate gene expression by binding to complementary sequences on target messenger RNA transcripts. In situ hybridisation (ISH) methods have been applied to the study of miRNA in tissue samples in order to understand which is the source of the miRNA of interest. In this paper, the authors describe a novel semi-automated bright field ISH method to visualise miRNAs in formalin fixed paraffin embedded tissue sections. The relevance of this work resides in the use of 3,3'-diaminobenzidine and peroxidase as the detection method, which provides a good defined deposition within tissues This method, which reveals the cells of origin of specific miRNAs, will enable investigators to further explore the biological role of miRNAs.

Noncoding RNAs as potential biomarkers to predict the outcome in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC), a common digestive system cancer, is highly malignant and has a poor disease outcome. Currently, all available examination and detection methods cannot accurately predict the clinical outcome. Therefore, it is extremely important to identify novel molecular biomarkers for personalized medication and to significantly improve the overall outcome. The “noncoding RNAs” (ncRNAs) are a group of RNAs that do not code for proteins, and they are categorized as structural RNAs and regulatory RNAs. It has been shown that microRNAs and long ncRNAs function as regulatory RNAs to affect the progression of various diseases. Many studies have confirmed a role for ncRNAs in the progression of PDAC during the last few years. Because of the significant role of ncRNAs in PDAC, ncRNA profiling may be used to predict PDAC outcome with high accuracy. This review comprehensively analyzes the value of ncRNAs as potential biomarkers to predict the outcome in PDAC and the possible mechanisms thereof.

Altered expression of long non-coding RNAs during genotoxic stress-induced cell death in human glioma cells

Long non-coding RNAs (lncRNAs), a recently discovered class of non-coding genes, are transcribed throughout the genome. Emerging evidence suggests that lncRNAs may be involved in modulating various aspects of tumor biology, including regulating gene activity in response to external stimuli or DNA damage. No data are available regarding the expression of lncRNAs during genotoxic stress-induced apoptosis and/or necrosis in human glioma cells. In this study, we detected a change in the expression of specific candidate lncRNAs (neat1, GAS5, TUG1, BC200, Malat1, MEG3, MIR155HG, PAR5, and ST7OT1) during DNA damage-induced apoptosis in human glioma cell lines (U251 and U87) using doxorubicin (DOX) and resveratrol (RES). We also detected the expression pattern of these lncRNAs in human glioma cell lines under necrosis induced using an increased dose of DOX. Our results reveal that the lncRNA expression patterns are distinct between genotoxic stress-induced apoptosis and necrosis in human glioma cells. The sets of lncRNA expressed during genotoxic stress-induced apoptosis were DNA-damaging agent-specific. Generally, MEG3 and ST7OT1 are up-regulated in both cell lines under apoptosis induced using both agents. The induction of GAS5 is only clearly detected during DOX-induced apoptosis, whereas the up-regulation of neat1 and MIR155HG is only found during RES-induced apoptosis in both cell lines. However, TUG1, BC200 and MIR155HG are down regulated when necrosis is induced using a high dose of DOX in both cell lines. In conclusion, our findings suggest that the distinct regulation of lncRNAs may possibly involve in the process of cellular defense against genotoxic agents.

The interplay between Epstein-Barr virus and B lymphocytes: implications for infection, immunity, and disease

Human B cells are the primary targets of Epstein-Barr virus (EBV) infection. In most cases, EBV infection is asymptomatic because of a highly effective host immune response, but some individuals develop self-limiting infectious mononucleosis, while others develop EBV-associated lymphoid or epithelial malignancies. The viral and immune factors that determine the outcome of infection are not understood. The EBV life cycle includes a lytic phase, culminating in the production of new viral particles, and a latent phase, during which the virus remains largely silent for the lifetime of the host in memory B cells. Thus, in healthy individuals, there is a tightly orchestrated interplay between EBV and the host that allows the virus to persist. To promote viral persistence, EBV has evolved a variety of strategies to modulate the host immune response including inhibition of immune cell function, blunting of apoptotic pathways, and interfering with antigen processing and presentation pathways. In this article, we focus on mechanisms by which dysregulation of the host B cell and immune modulation by the virus can contribute to development of EBV+ B cell lymphomas.

Therapeutic microRNAs targeting the NF-kappa B signaling circuits of cancers

MicroRNAs (miRNAs) not only directly regulate NF-κB expression, but also up- or down-regulate NF-κB activity via upstream and downstream signaling pathways of NF-κB. In many cancer cells, miRNA expressions are altered accompanied with an elevation of NF-κB activity, which often plays a role in promoting cancer development and progression as well as hindering the effectiveness of chemo and radiation therapies. Thus NF-κB-targeting miRNAs have been identified and characterized as potential therapeutics for cancer treatment and sensitizers of chemo and radiotherapies. However, due to cross-targeting and instability of miRNAs, some limitations of using miRNA as cancer therapeutics still exist. In this review, the mechanisms for miRNA-mediated alteration of NF-κB expression and activation in different types of cancers will be discussed. The results of therapeutic use of NF-κB-targeting miRNA for cancer treatment will be examined. Some limitations, challenges and potential strategies in future development of miRNA as cancer therapeutics are also assessed.

Gene expression profiling in non-Hodgkin lymphomas

Although the current WHO classification (Swerdlow et al. WHO classification of tumours of haematopoietic and lymphoid tissues. International Agency for Research on Cancer, Lyon, 2008 [1]) for hematolymphoid neoplasms has delineated lymphomas based on the combined morphologic, immunophenotypic, and genotypic findings, further refinement is necessary especially in regard to therapeutics and prognostic implications. High-throughput gene expression profiling (GEP) using microarray technology (Schena et al. Science 270:467-470, 1995 [2]; Augenlicht et al. Proc Natl Acad Sci USA 88:3286-3289, 1991 [3]) was developed about 20 years ago, and further refinement of the technology and analytical approaches has enabled us to routinely evaluate practically the entire transcriptome at a time. GEP has helped to improve the classification and prognostication of non-Hodgkin lymphomas (NHL) as well as improved our understanding of their pathophysiology and response to new therapeutics. In this paper, we will briefly review how this revolutionary tool has transformed our understanding of lymphomas and given us insight into targeted therapeutics. We will also discuss the current efforts in adapting the findings to routine clinical practice, the evolution of the research technology and directions in the future.

MicroRNAs in B-cells: from normal differentiation to treatment of malignancies

MicroRNAs (miRNAs) are small non-coding RNAs that play important post-transcriptional regulatory roles in a wide range of biological processes. They are fundamental to the normal development of cells, and evidence suggests that the deregulation of specific miRNAs is involved in malignant transformation due to their function as oncogenes or tumor suppressors. We know that miRNAs are involved in the development of normal B-cells and that different B-cell subsets express specific miRNA profiles according to their degree of differentiation. B-cell-derived malignancies contain transcription signatures reminiscent of their cell of origin. Therefore, we believe that normal and malignant B-cells share features of regulatory networks controlling differentiation and the ability to respond to treatment. The involvement of miRNAs in these processes makes them good biomarker candidates. B-cell malignancies are highly prevalent, and the poor overall survival of patients with these malignancies demands an improvement in stratification according to prognosis and therapy response, wherein we believe miRNAs may be of great importance. We have critically reviewed the literature, and here we sum up the findings of miRNA studies in hematological cancers, from the development and progression of the disease to the response to treatment, with a particular emphasis on B-cell malignancies.

microRNA and NF-kappa B

Nuclear Factor kappa B (NF-κB) plays important roles in regulation of countless cellular functions, including cell cycle and apoptosis. As a versatile transcription factor, NF-κB is a target of a large amount of miRNAs. Abnormal NF-κB activity is frequently associated with an abnormal level of miRNAs, which is found to play critical roles in disease progression including cancer. While the expression and activity of NF-κB can be directly or indirectly up-regulated or downregulated by various miRNAs, NF-κB can also regulate the expression of many miRNAs. Intriguingly, reciprocal regulation between miRNAs and NF-κB, which exists in the form of positive and negative feedback loops, is often observed in various cancers. In this chapter, the mechanisms and roles of miRNA-regulated NF-κB and NF-κB-regulated miRNAs in a variety of cancers will be discussed. The potential therapeutic use of miRNAs that are up- and down-stream of NF-κB signaling pathways as targets for cancer treatment will also be accessed.

Insights into epigenetic regulation of microRNA-155 expression in multiple myeloma

CONTEXT

MiR-155 plays a critical role in the development of B-cell malignancies. Previous studies have shown a deregulation of miR-155 in specific cytogenetic subtypes of multiple myeloma (MM). However, the mechanisms that regulate miR-155 expression in MM are not fully understood.

OBJECTIVE

In the present study, we explored the regulation of miRNA-155 in MM by DNA methylation mechanisms and the impact of miR-155 expression in survival of MM patients.

METHOD

Primary samples were obtained from 95 patients with newly diagnosed myeloma. Methylation was analyzed by Methylation Specific PCR, sequencing of bisulfite treated DNA and luciferase assay.

RESULTS

qRT-PCR analysis revealed that miR-155 was differentially expressed in MM and its upregulation was associated with longer survival. DNA methylation of CpG island present in the first exon of miR-155 host gene was associated with its low expression in MM cell lines and patient samples. Our results showed for the first time that in vitro methylation of part of the promoter and first exon abrogated the miR-155 expression. We further showed that miR-155 expression in MM cell lines was increased by demethylating 5-aza-dC treatment and decreased by RNA-directed DNA methylation. Additionally, we found that LPS "immunological challenge" was insufficient to induce miR-155 expression in MM cell lines with methylated DNA around transcription start site (TSS).

CONCLUSION

This study provides evidence that DNA methylation contributes to miR-155 expression in myeloma cells. Interestingly, the survival data showed an association between miR-155 expression and outcome of MM.

Malignant hematopoietic cell lines: in vitro models for the study of primary mediastinal B-cell lymphomas

Primary mediastinal B-cell lymphoma (PMBL) is a highly aggressive disease with a unique set of biological, clinical, morphological, immunological and in particular genetic features that in the molecular era of defining lymphomas clearly distinguishes it as a separate entity from other diffuse large B-cell lymphomas (DLBCL). A precise molecular diagnosis of PMBL can be achieved by gene expression profiling. The signature gene expression profile of PMBL is more closely related to classic Hodgkin lymphoma (cHL) than to other DLBCL subgroups. A number of common genetic aberrations in PMBL and cHL further underscore their close relationship. To investigate the pathobiology of lymphomas in depth, many groups have turned to cell lines that are suitable models facilitating molecular studies and providing unique insights. For the purposes of the current perspective, we focus on four bona fide PMBL-derived cell lines (FARAGE, KARPAS-1106, MEDB-1, U-2940) that we identified and validated as such through hierarchical cluster analysis among a large collection of leukemia-lymphoma cell lines. These gene expression profiles showed that the four PMBL cell lines represent a distinct entity and are most similar to cHL cell lines, confirming derivation from a related cell type. A validated cell line resource for PMBL should assist those seeking druggable targets in this entity. This review aims to provide a comprehensive overview of the currently available cellular models for the study of PMBL.

Pathogenic microRNA's in myeloid malignancies

Recent studies have significantly improved our understanding of the role microRNAs (miRNAs) play in regulating normal hematopoiesis. miRNAs are critical for maintaining hematopoietic stem cell function and the development of mature progeny. Thus, perhaps it is not surprising that miRNAs serve as oncogenes and tumor suppressors in hematologic malignancies arising from hematopoietic stem and progenitor cells, such as the myeloid disorders. A number of studies have extensively documented the widespread dysregulation of miRNA expression in human acute myeloid leukemia (AML), inspiring numerous explorations of the functional role of miRNAs in myeloid leukemogenesis. While these investigations have confirmed that a large number of miRNAs exhibit altered expression in AML, only a small fraction has been confirmed as functional mediators of AML development or maintenance. Herein, we summarize the miRNAs for which strong experimental evidence supports their functional roles in AML pathogenesis. We also discuss the implications of these studies on the development of miRNA-directed therapies in AML.

Isothermal amplified detection of DNA and RNA

This review highlights various methods that can be used for a sensitive detection of nucleic acids without using thermal cycling procedures, as is done in PCR or LCR. Topics included are nucleic acid sequence-based amplification (NASBA), strand displacement amplification (SDA), loop-mediated amplification (LAMP), Invader assay, rolling circle amplification (RCA), signal mediated amplification of RNA technology (SMART), helicase-dependent amplification (HDA), recombinase polymerase amplification (RPA), nicking endonuclease signal amplification (NESA) and nicking endonuclease assisted nanoparticle activation (NENNA), exonuclease-aided target recycling, Junction or Y-probes, split DNAZyme and deoxyribozyme amplification strategies, template-directed chemical reactions that lead to amplified signals, non-covalent DNA catalytic reactions, hybridization chain reactions (HCR) and detection via the self-assembly of DNA probes to give supramolecular structures. The majority of these isothermal amplification methods can detect DNA or RNA in complex biological matrices and have great potential for use at point-of-care.

Regulation of cancer metastasis by cell-free miRNAs

MicroRNAs (miRNAs) are integral molecules in the regulation of numerous physiological cellular processes that have emerged as critical players in cancer initiation and metastatic progression, both by promoting and suppressing metastasis. Recently, cell-free miRNAs shed from cancer cells into circulation have been reported in cancer patients, raising hope for development of novel biomarkers that can be routinely measured in easily accessible samples. In fact, establishing miRNA expression in the circulation likely has advantages over determination in primary tumor tissue, further augmenting the potential applications of miRNA detection in oncological practice. In addition, secretion of miRNAs impacting distant cell signaling or promoting the formation of a niche that sustains a distant tumor microenvironment allows for new treatment approaches to thwart cancer progression.

Discovery of prognostic factors for diagnosis and treatment of epithelial-derived ovarian cancer from laying hens

Ovarian cancer is a lethal gynecological cancer causing cancer-related deaths in women worldwide. It is difficult to diagnosis at an early stage when more than 90% patients can be cured because of lack of specific symptoms and early detection markers. Most of malignant ovarian tumors are originated from the germinal epithelium of the ovary. For investigation with animal models of epithelial-derived ovarian cancer (EOC), laying hens are the most relevant animal models because they spontaneously develop EOC as occurs in women through ovulating almost every day. As in women, EOC in the hen is age-related and grossly and histologically similar to that in women. However, domesticated animals are inappropriate for research human EOC due to multiple pregnancies and lactating or seasonally anestrous. In addition, the non-spontaneous nature of rodents EOC limits clinical relevance with human EOC. Recent studies have shown that ovarian cancer could arise from epithelium from the oviduct as oviduct-related genes are up-regulated in EOC of hens. Therefore, we showed in the review: 1) characterization and classification of EOC; 2) chicken models for EOC; 3) relationship estrogen with EOC; 4) candidate prognostic factors for EOC including serpin peptidase inhibior, clade B (ovalbumin), member 3 (SERPINB3), SERPINB11, gallicin 11 (GAL11), secreted phosphoprotein 1 (SPP1) and alpha 2 macroglobulin (A2M) in normal and cancerous ovaries of laying hens; 5) biological roles of microRNAs in development of EOC. Collectively, the present reviews indicate that expression of SERPINB3, SERPINB11, GAL11, SPP1 and A2M is clearly associated with the development of ovarian carcinogenesis. These results provide new insights into the prognostic biomarkers for EOC to diagnose and to evaluate responses to therapies for treating EOC of humans.

Novel treatment options for Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM), first described by Jan Waldenström in 1944, is a lymphoplasmacytic lymphoma characterized by the presence of an immunoglobulin M monoclonal gammopathy in the blood and monoclonal small lymphocytes and lymphoplasmacytoid cells in the bone marrow. WM is a rare and indolent disease but remains incurable. In this review we discuss the pathogenesis of WM and focus on novel treatment options that target pathways deregulated in this disease. Recent studies have helped us identify specific genetic mutations that are commonly seen in WM and might prove to be important therapeutic targets in the future. We discuss the role of epigenetics and the changes in the bone marrow microenvironment that are important in the pathogenesis of WM. The commonly used drugs are discussed with a focus on novel agents that are currently being used as single agents or in combination to treat WM. We finally focus on some agents that have shown preclinical efficacy and might be available in the near future.

MicroRNA-mediated mechanism of vitamin D regulation of innate immune response

Macrophages play a critical role in innate immune response to protect the host from pathogenic microorganisms. Inflammatory response is regulated by negative feedback mechanisms to prevent detrimental effects. The SOCS family of proteins is key component of the negative feedback loop that regulates the intensity, duration and quality of cytokine signaling, whereas miR-155 is a key regulator of Toll-like receptor (TLR) signaling that targets SOCS1 in activated macrophages to block the negative feedback loop. Recently we showed that 1,25-dihydroxyvitamin D (1,25(OH)2D3) modulates innate immune response by targeting the miR-155-SOCS1 axis. We found that Vdr deletion leads to hyper inflammatory response in mice and macrophage cultures when challenged with lipopolysaccharide (LPS), due to miR-155 overproduction to excessively suppress SOCS1. Using mice with bic/miR-155 deletion we confirmed that 1,25(OH)2D3 suppresses inflammation and stimulates SOCS1 by down-regulating miR-155. Mechanistically 1,25(OH)2D3 down-regulates bic transcription by blocking NF-κB activation, which is mediated by a κB cis-DNA element identified within the first intron of the bic gene. At the molecular level, we demonstrated that VDR inhibits NF-κB activation by directly interacting with IKKβ protein. Our studies identified a novel mechanism whereby VDR signaling attenuates TLR-mediated inflammation by enhancing the negative feedback regulation. This article is part of a Special Issue entitled '16th Vitamin D Workshop'.

Challenges and opportunities of microRNAs in lymphomas

MicroRNAs (miRNAs) are small non-coding RNAs that control the expression of many target messenger RNAs (mRNAs) involved in normal cell functions (differentiation, proliferation and apoptosis). Consequently their aberrant expression and/or functions are related to pathogenesis of many human diseases including cancers. Haematopoiesis is a highly regulated process controlled by a complex network of molecular mechanisms that simultaneously regulate commitment, differentiation, proliferation, and apoptosis of hematopoietic stem cells (HSC). Alterations on this network could affect the normal haematopoiesis, leading to the development of haematological malignancies such as lymphomas. The incidence of lymphomas is rising and a significant proportion of patients are refractory to standard therapies. Accurate diagnosis, prognosis and therapy still require additional markers to be used for diagnostic and prognostic purpose and evaluation of clinical outcome. The dysregulated expression or function of miRNAs in various types of lymphomas has been associated with lymphoma pathogenesis. Indeed, many recent findings suggest that almost all lymphomas seem to have a distinct and specific miRNA profile and some miRNAs are related to therapy resistance or have a distinct kinetics during therapy. MiRNAs are easily detectable in fresh or paraffin-embedded diagnostic tissue and serum where they are highly stable and quantifiable within the diagnostic laboratory at each consultation. Accordingly they could be specific biomarkers for lymphoma diagnosis, as well as useful for evaluating prognosis or disease response to the therapy, especially for evaluation of early relapse detection and for greatly assisting clinical decisions making. Here we summarize the current knowledge on the role of miRNAs in normal and aberrant lymphopoiesis in order to highlight their clinical value as specific diagnosis and prognosis markers of lymphoid malignancies or for prediction of therapy response. Finally, we discuss their controversial therapeutic role and future applications in therapy by modulating miRNA.

Identification and clinical implications of circulating microRNAs for estrogen receptor-positive breast cancer

Cancer-associated microRNAs have been stably detected in blood. The objective of this study was to identify a panel of circulating microRNAs with the potential to serve as biomarkers for estrogen receptor-positive (ER+)/human epidermal growth factor receptor 2 (HER2)- breast cancer. We used microarray-based expression profiling to compare the levels of circulating microRNAs in blood samples from 11 ER+/HER2- advanced breast cancer patients plus 5 age-matched controls. MicroRNA levels were validated by reverse transcription quantitative polymerase chain reaction in 40 control subjects, 187 early breast cancer patients, and 45 metastatic breast cancer patients. Then, we assessed the association between the levels of microRNA and clinical outcomes of ER+/HER2- metastatic breast cancer. Initially, we found that miR-1280, miR-1260, and miR-720 were up-regulated in blood from breast cancer patients (P < 0.05). In validation, miR-1280 levels significantly increased in breast cancer patients and reflected tumor status (control<<early cancer<metastatic cancer). Among 37 metastatic breast cancer patients, miR-1280 levels significantly decreased after treatment in patients who responded to systemic treatment (P < 0.001). We confirmed that miR-1280 was not a classic microRNA, but a tRNA(Leu)-derived fragment. These findings suggest that a circulating tRNA-derived microRNA, miR-1280, is differently expressed in breast cancer patients and may serve as a biomarker for ER-positive breast cancer.

miR-155 inhibitor reduces the proliferation and migration in osteosarcoma MG-63 cells

As the most common malignant primary bone tumor in childhood, osteosarcoma (OS) maintains a high recurrence, despite the significant improvements in the overall survival rate of high-grade OS patients during the recent decades. Therefore, a novel therapy strategy is required for OS treatment. Recently, various microRNAs (miRNAs or miRs) have been confirmed as deregulated in OS, and the miR-155 dysregulation in OS has been discovered by the microarray analysis. In the present study, the regulation of miR-155 on the OS cell proliferation, migration and invasion on the MG-63 cells was explored in vitro. The miR-155 mimics were found to promote cell proliferation, colony formation, migration and invasion significantly, compared to the control miRNA. An miR-155 inhibitor was also used to evaluate whether miR-155 served as a therapeutic target for OS. The results demonstrated that the miR-155 inhibitor significantly reduced the proliferation, colony formation, migration and invasion of the MG-63 OS cells. Thus, the study confirmed the oncogenic regulation on the OS progression of miR-155, which could serve as a therapeutic target with an miR-155 inhibitor.

MicroRNA-155 deficiency enhances the recruitment and functions of myeloid-derived suppressor cells in tumor microenvironment and promotes solid tumor growth

Immune cells in tumor microenvironment play a prominent role in tumor progression and metastasis. MicroRNA-155 (miR-155) represents an important player in innate and adaptive immunity by regulating differentiation, maturation and activation of macrophages, dendritic cells, B cells and T cells. However, the role of miR-155 expression in immune cells in solid tumor development is less elucidated. Our current study showed that both B16-F10 melanoma and Lewis lung carcinoma tumors grew much faster in bic/miR-155 knockout (miR-155(-/-) ) mice along with an increase of myeloid-derived suppressor cells (MDSCs) accumulation in tumors, compared to that in wild-type mice. Bone marrow transplantation study showed that bone marrow miR-155 deficiency could replicate the above tumor-promoting phenotype. In vitro study demonstrated that tumor-infiltrating miR-155(-/-) MDSCs showed greater migration ability and expressed higher level of multiple chemokines. Furthermore, we found that the level of HIF-1α, a direct target of miR-155, was increased in miR-155 deficient MDSCs, and that the increased HIF-1α upregulated CXCL1, CXCL3 and CXCL8 expression in MDSCs, contributing to the enhanced recruitment of miR-155(-/-) MDSCs to the tumors. Moreover, miR-155(-/-) MDSCs showed enhanced immunosuppressive and pro-angiogenic capacities. Taken together, our study, for the first time, demonstrated that miR-155 deficiency promoted solid tumor growth through increasing the recruitment of MDSCs to tumor microenvironment and enhancing the tumor-promoting functions of the recruited MDSCs. Thus, upregulating miR-155 expression in MDSCs may be developed as a therapeutic approach to halt tumor development.

A systems biology approach identified different regulatory networks targeted by KSHV miR-K12-11 in B cells and endothelial cells

Background

Kaposi’s sarcoma associated herpes virus (KSHV) is associated with tumors of endothelial and lymphoid origin. During latent infection, KSHV expresses miR-K12-11, an ortholog of the human tumor gene hsa-miR-155. Both gene products are microRNAs (miRNAs), which are important post-transcriptional regulators that contribute to tissue specific gene expression. Advances in target identification technologies and molecular interaction databases have allowed a systems biology approach to unravel the gene regulatory networks (GRNs) triggered by miR-K12-11 in endothelial and lymphoid cells. Understanding the tissue specific function of miR-K12-11 will help to elucidate underlying mechanisms of KSHV pathogenesis.

Results

Ectopic expression of miR-K12-11 differentially affected gene expression in BJAB cells of lymphoid origin and TIVE cells of endothelial origin. Direct miRNA targeting accounted for a small fraction of the observed transcriptome changes: only 29 genes were identified as putative direct targets of miR-K12-11 in both cell types. However, a number of commonly affected biological pathways, such as carbohydrate metabolism and interferon response related signaling, were revealed by gene ontology analysis. Integration of transcriptome profiling, bioinformatic algorithms, and databases of protein-protein interactome from the ENCODE project identified different nodes of GRNs utilized by miR-K12-11 in a tissue-specific fashion. These effector genes, including cancer associated transcription factors and signaling proteins, amplified the regulatory potential of a single miRNA, from a small set of putative direct targets to a larger set of genes.

Conclusions

This is the first comparative analysis of miRNA-K12-11’s effects in endothelial and B cells, from tissues infected with KSHV in vivo. MiR-K12-11 was able to broadly modulate gene expression in both cell types. Using a systems biology approach, we inferred that miR-K12-11 establishes its GRN by both repressing master TFs and influencing signaling pathways, to counter the host anti-viral response and to promote proliferation and survival of infected cells. The targeted GRNs are more reproducible and informative than target gene identification, and our approach can be applied to other regulatory factors of interest.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-668) contains supplementary material, which is available to authorized users.

NF-κB/STAT5/miR-155 network targets PU.1 in FLT3-ITD-driven acute myeloid leukemia

Almost 30% of all acute myeloid leukemias (AML) are associated with an internal tandem duplication (ITD) in the juxtamembrane domain of FMS-like tyrosine kinase 3 receptor (FLT3). Patients with FLT3-ITD mutations tend to have a poor prognosis. MicroRNAs (miRNAs) have a pivotal role in myeloid differentiation and leukemia. MiRNA-155 (MiR-155) was found to be upregulated in FLT3-ITD-associated AMLs. In this study, we discovered that FLT3-ITD signaling induces the oncogenic miR-155. We show in vitro and in vivo that miR-155 expression is regulated by FLT3-ITD downstream targets nuclear factor-κB (p65) and signal transducer and activator of transcription 5 (STAT5). Further, we demonstrate that miR-155 targets the myeloid transcription factor PU.1. Knockdown of miR-155 or overexpression of PU.1 blocks proliferation and induces apoptosis of FLT3-ITD-associated leukemic cells. Our data demonstrate a novel network in which FLT3-ITD signaling induces oncogenic miR-155 by p65 and STAT5 in AML, thereby targeting transcription factor PU.1.

miR-2909-mediated regulation of KLF4: a novel molecular mechanism for differentiating between B-cell and T-cell pediatric acute lymphoblastic leukemias

Background

microRNAs (miRNAs) play both oncogenic and oncostatic roles in leukemia. However, the molecular details underlying miRNA-mediated regulation of their target genes in pediatric B- and T-cell acute lymphoblastic leukemias (ALLs) remain unclear. The present study investigated the relationship between miR-2909 and Kruppel-like factor 4 (KLF4), and its functional relevance to cell cycle progression and immortalization in patients with pediatric ALL.

Methods

Elevated levels of miR-2909 targeted the tumor suppressor gene KLF4 in pediatric B-cell, but not pediatric T-cell ALL, as detected by pMIR-GFP reporter assay. Expression levels of genes including apoptosis-antagonizing transcription factor (AATF), MYC, B-cell lymphoma (BCL3), P21^CIP, CCND1 and SP1 in B- and T-cells from patients with pediatric ALL were compared with control levels using real-time quantitative reverse transcription polymerase chain reaction, western blotting, and reporter assays.

Results

We identified two novel mutations in KLF4 in pediatric T-ALL. A mutation in the 3′ untranslated region of the KLF4 gene resulted in loss of miR-2909-mediated regulation, while mutation in its first or third zinc-finger motif (Zf1/Zf3) rendered KLF4 transcriptionally inactive. This mutation was a frameshift mutation resulting in alteration of the Zf3 motif sequence in the mutant KLF4 protein in all pediatric T-ALL samples. Homology models, docking studies and promoter activity of its target gene P21^CIP confirmed the lack of function of the mutant KLF4 protein in pediatric T-ALL. Moreover, the inability of miR-2909 to regulate KLF4 and its downstream genes controlling cell cycle and apoptosis in T-cell but not in B-ALL was verified by antagomiR-2909 transfection. Comprehensive sequence analysis of KLF4 identified the predominance of isoform 1 (~55 kDa) in most patients with pediatric B-ALL, while those with pediatric T-ALL expressed isoform 2 (~51 kDa).

Conclusions

This study identified a novel miR-2909-KLF4 molecular axis able to differentiate between the pathogeneses of pediatric B- and T-cell ALLs, and which may represent a new diagnostic/prognostic marker.

MicroRNA-155 influences B-cell receptor signaling and associates with aggressive disease in chronic lymphocytic leukemia

High-level leukemia cell expression of micro-RNA 155 (miR-155) is associated with more aggressive disease in patients with chronic lymphocytic leukemia (CLL), including those cases with a low-level expression of ζ-chain-associated protein of 70 kD. CLL with high-level miR-155 expressed lower levels of Src homology-2 domain-containing inositol 5-phosphatase 1 and were more responsive to B-cell receptor (BCR) ligation than CLL with low-level miR-155. Transfection with miR-155 enhanced responsiveness to BCR ligation, whereas transfection with a miR-155 inhibitor had the opposite effect. CLL in lymphoid tissue expressed higher levels of miR155HG than CLL in the blood of the same patient. Also, isolated CD5(bright)CXCR4(dim) cells, representing CLL that had been newly released from the microenvironment, expressed higher levels of miR-155 and were more responsive to BCR ligation than isolated CD5(dim)CXCR4(bright) cells of the same patient. Treatment of CLL or normal B cells with CD40-ligand or B-cell-activating factor upregulated miR-155 and enhanced sensitivity to BCR ligation, effects that could be blocked by inhibitors to miR-155. This study demonstrates that the sensitivity to BCR ligation can be enhanced by high-level expression of miR-155, which in turn can be induced by crosstalk within the tissue microenvironment, potentially contributing to its association with adverse clinical outcome in patients with CLL.

Role of miR-155 in the regulation of lymphocyte immune function and disease

MicroRNAs (miRNAs) have emerged as critical regulators of gene expression within cells. One particular miRNA, miR-155, is highly expressed within lymphocytes (both B and T cells) and mediates a number of important roles. These include shaping the transcriptome of lymphoid cells that control diverse biological functions vital in adaptive immunity. The use of mice engineered to be deficient in miR-155, as well as the identification of endogenous targets of miR-155 in T cells by transcriptome-wide analysis, has helped to unravel the crucial role that this miRNA plays in fine tuning the regulation of lymphocyte subsets such as B cells, CD8(+) and CD4(+) T cells ranging from T helper type 1 (Th1), Th2, Th17 and regulatory T cells. In this review, we summarize what we have learned about miR-155 in the regulation of lymphocyte responses at the cellular and molecular levels and in particular, we focus on the recent findings showing that miR-155 shapes the balance between tolerance and immunity.

MicroRNA-155 as an inducer of apoptosis and cell differentiation in Acute Myeloid Leukaemia

Background

Acute myeloid leukaemia (AML) is characterised by the halt in maturation of myeloid progenitor cells, combined with uncontrolled proliferation and abnormal survival, leading to the accumulation of immature blasts. In many subtypes of AML the underlying causative genetic insults are not fully described. MicroRNAs are known to be dysregulated during oncogenesis. Overexpression of miR-155 is associated with some cancers, including haematological malignancies, and it has been postulated that miR-155 has an oncogenic role. This study investigated the effects of modulating miR-155 expression in human AML cells, and its mechanism of action.

Results

Analysis of miR-155 expression patterns in AML patients found that Fms-like tyrosine kinase 3 (FLT3)-wildtype AML has the same expression level as normal bone marrow, with increased expression restricted to AML with the FLT3-ITD mutation. Induction of apoptosis by cytarabine arabinoside or myelomonocytic differentiation by 1,23-dihydroxyvitaminD3 in FLT3-wildtype AML cells led to upregulated miR-155 expression. Knockdown of miR-155 by locked nucleic acid antisense oligonucleotides in the FLT3-wildtype AML cells conferred resistance to cytarabine arabinoside induced apoptosis and suppressed the ability of cells to differentiate.

Ectopic expression of miR-155 in FLT3-wildtype AML cells led to a significant gain of myelomonocytic markers (CD11b, CD14 and CD15), increase in apoptosis (AnnexinV binding), decrease in cell growth and clonogenic capacity.

In silico target prediction identified a number of putative miR-155 target genes, and the expression changes of key transcription regulators of myeloid differentiation and apoptosis (MEIS1, GF1, cMYC, JARID2, cJUN, FOS, CTNNB1 and TRIB2) were confirmed by PCR. Assessment of expression of apoptosis-related proteins demonstrated a marked increase in cleaved caspase-3 expression confirming activation of the apoptosis cascade.

Conclusions

This study provides evidence for an anti-leukaemic role for miR-155 in human FLT3-wildtype AML, by inducing cell apoptosis and myelomonocytic differentiation, which is in contrast to its previously hypothesized role as an oncogene. This highlights the complexity of gene regulation by microRNAs that may have tumour repressor or oncogenic effects depending on disease context or tissue type.

Mir-155, a central modulator of T-cell responses

The activation of T cells is a tightly regulated process that has evolved to maximize protective immune responses to pathogens while minimizing damage to self-tissues. A delicate balance of cell-intrinsic, costimulatory, and transcriptional pathways as well as micro-environmental cues such as local cytokines controls the magnitude and nature of T-cell responses in vivo. The discovery of functional small noncoding RNAs called micro-RNAs (miRNAs) has introduced new mechanisms that contribute to the regulation of protein translation and cellular responses to stimuli. miRNAs are short (approximately 22 bp) RNA species, which bind to mRNAs and suppress translation. Due to their short length and imperfect base pairing requirements, each miRNA has the potential to regulate various pathways through the translational inhibition of multiple mRNAs. The human and mouse genomes each encode hundreds of miRNAs, and studying the function of miRNAs has led to the realization that they play important roles in diverse biological processes from development and cancer to immunity. This review focuses on the function of mir-155 in T cells and the impact of this miRNA on autoimmunity, tumor immunity, and pathogen-induced immunity.

microRNA therapies in cancer

MicroRNAs (miRNAs or miRs) are a family of small non-coding RNA species that have been implicated in the control of many fundamental cellular and physiological processes such as cellular differentiation, proliferation, apoptosis and stem cell maintenance. miRNAs regulate gene expression by the sequence-selective targeting of mRNAs, leading to translational repression or mRNA degradation. Some microRNAs have been categorized as “oncomiRs” as opposed to “tumor suppressor miRs” Modulating the miRNA activities may provide exciting opportunities for cancer therapy. This review highlights the latest discovery of miRNAs involved in carcinogenesis as well as the potential applications of miRNA regulations in cancer treatment. Several studies have demonstrated the feasibility of restoring tumor suppressive miRNAs and targeting oncogenic miRNAs for cancer therapy using in vivo model systems.

Integrating non-coding RNAs in JAK-STAT regulatory networks

Being a well-characterized pathway, JAK-STAT signaling serves as a valuable paradigm for studying the architecture of gene regulatory networks. The discovery of untranslated or non-coding RNAs, namely microRNAs and long non-coding RNAs, provides an opportunity to elucidate their roles in such networks. In principle, these regulatory RNAs can act as downstream effectors of the JAK-STAT pathway and/or affect signaling by regulating the expression of JAK-STAT components. Examples of interactions between signaling pathways and non-coding RNAs have already emerged in basic cell biology and human diseases such as cancer, and can potentially guide the identification of novel biomarkers or drug targets for medicine.

MicroRNA-155 promotes glioma cell proliferation via the regulation of MXI1

Gliomas are the most common and aggressive primary tumors in the central nervous system. Recently, Max interactor-1 (MXI1), an antagonist of c-Myc that is involved in brain tumor progression, has been reported to be deregulated in a variety of tumors including glioma. However, the mechanism of MXI1 deregulation in gliomas remains unclear. In this study, we show that the relative expression level of MXI1 is markedly down-regulated in glioma cell lines. Using integrated bioinformatic analysis and experimental confirmation, we identified several miRNAs by screening a panel of predicted miRNAs that may regulate the MXI1 3′UTR. The strongest inhibitory miRNA, miR-155, can attenuate the activity of a luciferase reporter gene that is fused with the MXI1 3′UTR and decrease the expression levels of MXI1 mRNA and protein in U87 glioma cells. The potential role of miR-155 in promoting glioma cell proliferation by targeting MXI1 was confirmed in various glioma cell lines by rescue experiments using MTT assays, EdU incorporation assay, and cell counting experiments. In addition, we determined that the level of MXI1 mRNA was inversely correlated with the expression of miR-155 in 18 sets of glioblastoma multiforme specimens. These findings reveal for the first time that the targeting of MXI1 by miR-155 may result in a reduction in MXI1 expression and promote glioma cell proliferation; this result suggests a novel function of miR-155 in targeting MXI1 in glioma-genesis.

Comparative analysis of microRNAs from the lungs and trachea of dogs (Canis familiaris) infected with canine influenza virus

MicroRNAs (miRNAs) are a class of endogenous non-coding small RNAs of 18-22-nucleotides in length that regulate gene expression at the post-transcriptional level. The objective of this study was to examine the differences in the miRNA expression profiles of the lungs and trachea of beagle dogs infected with canine influenza virus (CIV). Total RNA was isolated from lung and trachea tissues of beagle dogs infected and non-infected with H3N2 CIV at 4 dpi. A total of 41,512,315 and 39,107,475 reads were obtained from the lung and trachea, respectively. Out of a total 288 dog miRNAs available in miRBase, 227 and 236 miRNAs were detected in the infected (Fg) and the non-infected lungs (Fc), respectively, whereas 242 miRNAs were detected in both the infected (Qg) and the non-infected trachea (Qc). From these, 34 and 45 miRNAs were differentially expressed in the lungs and trachea between the infected and non-infected dogs, respectively. More miRNAs were highly expressed in the non-infected tissues than in the infected tissues. miR-143 was the most abundantly expressed miRNA in the four samples, followed by let-7. In total, 252, 234, 196 and 235 novel miRNAs were identified in the Fc, Fg, Qc, and Qg groups, respectively. To our knowledge, this is the first study examining the miRNA gene expression in CIV infected dogs using the Solexa sequencing approach. We have revealed the existence of a large number miRNAs that are affected by CIV infection as well as identified some potentially new miRNAs. These findings will help us better understand the host-CIV interaction and its relationship to pathogenesis, as well as contribute to the prevention and control of CIV.

Helicobacter pyloriγ-glutamyl transpeptidase: A formidable virulence factor

Helicobacter pylori (H. pylori) produce an enzyme known as γ-glutamyl transpeptidase (HpGGT) that is highly conserved and common to all strains. HpGGT has been gaining increasing attention as an important virulence factor of the bacterium, having been demonstrated to be an important colonization factor in several animal models and has also recently been strongly associated with the development of peptic ulcer disease. From the results of various independent researcher groups, it is clear that HpGGT acts through several pathways to damage gastric epithelial cells including the induction of apoptosis and cell cycle arrest, production of reactive oxygen species leading to DNA damage, promotion of inflammation by increasing cyclooxygenase-2 and interleukin-8 expression, and upregulation of heparin-binding epidermal growth factor-like growth factor resulting in cell survival and proliferation. In addition, the potential role of HpGGT in promoting gastric carcinogenesis will also be discussed in this review. Apart from affecting the gastric epithelium, HpGGT also has immunomodulatory actions on host immune cells where it displays an antiproliferative effect on T cells by inducing cell cycle arrest and also works with other H. pylori virulence factors to skew dendritic cells towards a tolerogenic phenotype, possibly contributing to the persistence of the pathogen in the gastric mucosa.

Hypoxia-induced MIR155 is a potent autophagy inducer by targeting multiple players in the MTOR pathway

Hypoxia activates autophagy, an evolutionarily conserved cellular catabolic process. Dysfunction in the autophagy pathway has been implicated in an increasing number of human diseases, including cancer. Hypoxia induces upregulation of a specific set of microRNAs (miRNAs) in a variety of cell types. Here, we describe hypoxia-induced MIR155 as a potent inducer of autophagy. Enforced expression of MIR155 increases autophagic activity in human nasopharyngeal cancer and cervical cancer cells. Knocking down endogenous MIR155 inhibits hypoxia-induced autophagy. We demonstrated that MIR155 targets multiple players in MTOR signaling, including RHEB, RICTOR, and RPS6KB2. MIR155 suppresses target-gene expression by directly interacting with their 3′ untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness. Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G₁/S cell cycle arrest. Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.

MicroRNAs with a role in gene regulation and in human diseases

MicroRNAs (miRNAs) are short 20-22 nucleotide non-coding RNA sequences. Recently identified, these are novel regulators of gene expression at translational level as well as transcriptional level. Alteration in miRNAs level has been observed in a number of human diseases and studies have been conducted on the effect of altered expression level of miRNAs on the development and progression of different diseases. The miRNAs can be used as molecular biomarkers in a number of diseases. Also, miRNAs are promising in providing a new platform for molecular therapeutics of previously incurable diseases. This review will focus on the introduction, recent advances in the field of miRNA and its importance in some human disorders.

Small molecule with big role: MicroRNAs in cancer metastatic microenvironments

Cancer metastasis is closely related to tumor cell microenvironments. Cancer cells and stromal cells interact with one another through extracellular matrix (ECM) and jointly participate in establishing the microenvironments. However, many questions remain to be addressed, in particular, a crucial question is which messengers mediate the mutual interaction and regulation between cancer cells and stromal cells. MicroRNAs (miRNAs), as oncogenic and oncosuppressor genes, regulate the expression and function of their related target genes to affect the biological behaviors of cancer cells and stromal cells, which may play an important role in cancer metastasis. Many miRNAs associated with cancer metastasis have been identified. The molecules of miRNAs are small and relatively easy to be secreted into extracellular microenvironments and devoured by nearby cells. As the regulatory messengers between cells, the secreted miRNAs function to regulate cancer cell proliferation, migration, intercellular communication and stromal modification, thereby helping cancer cells to establish their microenvironments for metastasis. In conclusion, miRNAs are small molecules, but they play a powerful role in regulating cancer metastatic ability by construction and modification of microenvironments.

MicroRNA-regulated pathways in hematological malignancies: how to avoid cells playing out of tune

The coordinated expression and interplay among lineage specific transcription factors and microRNAs contribute to the regulation of gene expression and determination of cell specificity. In hematopoietic stem cells (HSCs), unique combinations of transcription factors largely control growth and maturation of different blood cell lineages through cooperative regulation of specific target genes. MicroRNAs provide an additional level of control beyond transcription factors. By acting as regulators of crucial lineage-specific genetic programs, microRNAs direct early multipotential progenitor cells to adopt a certain cell fate program. Thus, alteration of specific microRNA levels may affect proliferation, differentiation and genetic stability of HSCs, contributing to the onset of myeloproliferative disorders and leukemia. The major aim of this review is to highlight the critical role of microRNA-regulated pathways during the establishment and progression of hematological malignancies, with a particular attention to leukemia, lymphomas and myelodysplastic syndromes. This will give us the opportunity to discuss the potential use of microRNA-based therapeutic approaches in these diseases. MicroRNAs are indeed emerging as relevant tools to improve the efficacy of currently used therapeutic protocols.