How Epstein–Barr Virus and Kaposi’s Sarcoma-Associated Herpesvirus Are Maintained Together to Transform the Same B-Cell

Epstein–Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV) independently cause human cancers, and both are maintained as plasmids in tumor cells. They differ, however, in their mechanisms of segregation; EBV partitions its genomes quasi-faithfully, while KSHV often clusters its genomes and partitions them randomly. Both viruses can infect the same B-cell to transform it in vitro and to cause primary effusion lymphomas (PELs) in vivo. We have developed simulations based on our measurements of these replicons in B-cells transformed in vitro to elucidate the synthesis and partitioning of these two viral genomes when in the same cell. These simulations successfully capture the biology of EBV and KSHV in PELs. They have revealed that EBV and KSHV replicate and partition independently, that they both contribute selective advantages to their host cell, and that KSHV pays a penalty to cluster its genomes.     

Toward microRNA-based therapeutics for heart disease: the sense in antisense

MicroRNAs act as negative regulators of gene expression by inhibiting the translation or promoting the degradation of target mRNAs. Because individual microRNAs often regulate the expression of multiple target genes with related functions, modulating the expression of a single microRNA can, in principle, influence an entire gene network and thereby modify complex disease phenotypes. Recent studies have identified signature expression patterns of microRNAs associated with pathological cardiac hypertrophy, heart failure, and myocardial infarction in humans and mouse models of heart disease. Gain- and loss-of-function studies in mice have revealed profound and unexpected functions for these microRNAs in numerous facets of cardiac biology, including the control of myocyte growth, contractility, fibrosis, and angiogenesis, providing glimpses of new regulatory mechanisms and potential therapeutic targets for heart disease. Especially intriguing is the discovery of a network of muscle-specific microRNAs embedded within myosin heavy chain genes, which control myosin expression and the response of the heart to stress and thyroid hormone signaling. Disease-inducing cardiac microRNAs can be persistently silenced in vivo through systemic delivery of antimiRs, allowing for the direct therapeutic modulation of disease mechanisms. Here, we summarize current knowledge of the roles of miRNAs in heart disease and consider the advantages and potential challenges of microRNA-based approaches compared to conventional drug-based therapies.     

AIDS related viruses, their association with leukemia, and Raf signaling

Leukemia is characterized by the production of an excessive number of abnormal white blood cells. Over time, this expanding population of poorly/non- functional white blood cells overwhelms the normal function of the body's blood and immune systems. DNA translocations have been found common to leukemia, including Raf mutations. While the cause of leukemia is not known, several risk factors have been identified. In this review, we present an update on the role of AIDS related viruses as an etiology for leukemia. Human immunodeficiency virus-1 and -2 (HIV-1; -2) are the cause for the development of acquired immune deficiency syndrome (AIDS). Epstein-Barr virus (EBV), human cytomegalovirus (HCMV), Human papillomavirus (HPV), and Kaposi's sarcoma-associated herpesvirus (KSHV) are specifically implicated in AIDS associated malignancies. However, there are other viruses that are associated to a lesser extent with the AIDS condition and they are Human T-cell leukemia virus-1 (HTLV-1), hepatitis B virus (HBV), hepatitis C virus (HCV), and human herpesvirus-6 (HHV-6). Of these viruses, HTLV-1 has been etiologically associated with leukemia. Recent evidence suggests that EBV, HBV, HCV, and KSHV may also play a role in the development of some types of leukemia. Raf signaling has been shown to aid in the infection and pathogenesis of many of these viruses, making Raf pathway components good potential targets for the treatment of leukemia induced by AIDS related viruses.     

基于GEO数据库对甲状腺乳头状癌的靶基因分析研究

目的初步探索分析甲状腺乳头状癌中的差异microRNA及其靶基因,为甲状腺乳头状癌的研究及治疗提供新的思路。方法从GEO数据库中查找适合的芯片,利用GEO2R在线网站及生物信息学分析软件进行差异的microRNA分析,并对符合筛选标准的microRNA及其靶基因进行GO和KEGG分析,筛选重要的microRNA及其靶基因。结果 (1)通过对芯片GSE73182及GSE113629数据挖掘发现,差异的microRNA有1535个,符合纳入研究标准的差异microRNA为12个,其中,上调的microRNA为8个,下调的microRNA为4个。(2)差异的microRNA进行预测靶基因,得出关键的靶基因有44个,主要参与生物学调控、代谢、免疫应答、蛋白质结合等方面。(3)文章发现:hsa-miR-21-5p与靶标JAG1及SOX5、hsa-miR-181a与靶标PROX1、hsa-miR-204-5p与其靶标BCL2可能存在作用。结论hsa-miR-21-5p与靶标JAG1及SOX5、hsa-miR-181a与靶标PROX1、hsa-miR-204-5p与其靶标BCL2有望成为新的研究方向。     

Vertebrate virus-encoded microRNAs and their sequence conservation

An increasing number of studies have reported that approximately 400 microRNAs (miRNAs), encoded by vertebrate viruses, regulate the expression of both host and viral genes. Many studies have used computational and/or experimental analyses to identify the target genes of miRNAs, thereby enabling us to understand miRNA functions. Here, we suggest that important aspects become apparent when we focus on conserved viral miRNAs, although these miRNA sequences generally show little similarity among viral species. Reliable viral miRNA-target gene pairs can be efficiently identified using evolutionary information. In this review, we summarize information on (i) the nucleotide sequence conservation among viral miRNAs and (ii) the RNAs targeted by viral miRNAs. Recent advances in these topics are discussed.     

The Role of MicroRNAs and Their Targets in Osteoarthritis

Micro ribonucleic acid (microRNA) regulation and expression has become an emerging field in determining the mechanisms regulating a variety of inflammation-mediated diseases. Several studies have focused on specific microRNAs that are differentially expressed in cases of osteoarthritis. Furthermore, several targets of these miRNAs important in disease progression have also been identified. In this review, we focus on microRNA biogenesis, regulation, detection, and quantification with an emphasis on cellular localization and how these concepts may be linked to disease processes such as osteoarthritis. Next, we review the relationships of specific microRNAs to certain features and risk factors associated with osteoarthritis such as inflammation, obesity, autophagy, and cartilage homeostasis. We also identify certain microRNAs that are differentially expressed in osteoarthritis but have unidentified targets and functions in the disease state. Lastly, we identify the potential use of microRNAs for therapeutic purposes and also mention certain remedies that regulate microRNA expression.     

Modulation of B-cell exosome proteins by gamma herpesvirus infection

The human gamma herpesviruses, Kaposi sarcoma-associated virus (KSHV) and EBV, are associated with multiple cancers. Recent evidence suggests that EBV and possibly other viruses can manipulate the tumor microenvironment through the secretion of specific viral and cellular components into exosomes, small endocytically derived vesicles that are released from cells. Exosomes produced by EBV-infected nasopharyngeal carcinoma cells contain high levels of the viral oncogene latent membrane protein 1 and viral microRNAs that activate critical signaling pathways in recipient cells. In this study, to determine the effects of EBV and KSHV on exosome content, quantitative proteomics techniques were performed on exosomes purified from 11 B-cell lines that are uninfected, infected with EBV or with KSHV, or infected with both viruses. Using mass spectrometry, 871 proteins were identified, of which ∼360 were unique to the viral exosomes. Analysis by 2D difference gel electrophoresis and spectral counting identified multiple significant changes compared with the uninfected control cells and between viral groups. These data predict that both EBV and KSHV exosomes likely modulate cell death and survival, ribosome function, protein synthesis, and mammalian target of rapamycin signaling. Distinct viral-specific effects on exosomes suggest that KSHV exosomes would affect cellular metabolism, whereas EBV exosomes would activate cellular signaling mediated through integrins, actin, IFN, and NFκB. The changes in exosome content identified in this study suggest ways that these oncogenic viruses modulate the tumor microenvironment and may provide diagnostic markers specific for EBV and KSHV associated malignancies.Microvesicles are membrane-enclosed vesicles secreted from cells that participate in intracellular communication events through the transfer of biologically active proteins, lipids, and RNAs (1). Perhaps the best-studied class of microvesicles is exosomes which are 40- to 100-nm vesicles that originate from internal endosomal-derived membranes of multivesicular bodies (MVBs). Upon fusion of MVBs with the cell surface, exosomes are released into the extracellular space and can be taken up by neighboring cells, degraded, or enter connecting bodily fluids and travel to distal sites within the body. To date, exosomes have been found in almost every bodily fluid and increasingly are evaluated for their potential as diagnostic biomarkers. Exosomes are thought potentially to modulate many physiological processes including development, cell growth, immune regulation, angiogenesis, neuronal communication, cell migration, and invasion (1). Accumulating evidence supports the hypothesis that disruption of or alterations in normal exosome function may contribute to disease pathogenesis, and unique properties have been identified in exosomes released from malignant cells.The human gamma herpesviruses, Kaposi sarcoma-associated virus (KSHV) and EBV, are considered the etiologic agents for several lymphoid malignancies (2–4). EBV is associated with Burkitt lymphoma, Hodgkin lymphoma, posttransplantation lymphoproliferative diseases, and AIDS-associated lymphomas, whereas KSHV is found in all primary effusion lymphomas (PELs) and multicentric Castleman’s disease. A subset of PELs contains both KSHV and EBV (5). Previous studies have shown that EBV affects exosome content and function, and virally modified exosomes can contain the viral oncoproteins latent membrane proteins 1 and 2 (LMP1 and LMP2) and virally encoded microRNAs (miRNAs) (6, 7). The transfer of LMP1-containing exosomes induces the activation of phosphoinositide 3-kinase (PI3K)/AKT and MAPK/ERK pathways in target cells (6). Additionally, exosomal transfer of EBV miRNAs has been shown to reduce target gene expression in recipient cells (8). Therefore, EBV-infected cells can modulate the cellular microenvironment through the transfer of virally modified exosomes. This transfer may be a significant mechanism through which herpesviruses maintain a latent and persistent infection within the host. Additionally, it is likely that tumorigenic herpesviruses such as EBV and KSHV modulate exosome content and function so that exosomes produced by the infected cells affect the tumor microenvironment and contribute to cancer progression.Multiple studies have begun to define the protein, RNA, and lipid components of exosomes secreted from various cell types (9–11). In this study, exosomes were purified from EBV-infected, KSHV-infected, and dually infected B-cell lines and were analyzed using quantitative proteomics approaches to determine how EBV and KSHV infection alters B-cell exosome components. Mass spectrometry analysis of purified exosomes from 11 different B-cell lines revealed 871 proteins. Data from spectral counting determined that the B-cell exosome proteome from the virally infected cells was significantly different from the exosomes produced by the uninfected B-cell control exosomes, with 345 proteins unique to the virally infected cells and with significant changes specific to each virus. These data show that EBV and KSHV potently affect the host exosome pathway.     

The viral interferon-regulatory factor-3 is required for the survival of KSHV-infected primary effusion lymphoma cells

Human herpesvirus-8 (HHV-8), also known as Kaposi sarcoma-associated herpesvirus (KSHV), is etiologically linked to primary effusion lymphoma (PEL). At least 10 KSHV-encoded proteins with potential roles in KSHV-associated neoplasia have been identified. However, with few exceptions, these putative oncogenes were analyzed in heterologous systems only using overexpression of single genes. Thus, the pathogenetic relevance of most of these putative oncogenes remains essentially unclear. We used RNA interference (RNAi) to knock down the expression of several KSHV genes in cultured PEL cells carrying the KSHV genome. The viral interferon-regulatory factor-3 (vIRF-3) was found to be required for proliferation and survival of cultured PEL cells. Knock-down of vIRF-3 expression by various RNAi approaches unequivocally resulted in reduced proliferation and increased activity of caspase-3 and/or caspase-7. Thus, vIRF-3 can be seen as a bona fide oncogene of KSHV-associated lymphoma. Surprisingly, although the related Epstein-Barr virus (EBV) is usually sufficient to immortalize human B lymphocytes, silencing of vIRF-3 reduced the viability of both EBV(-) and EBV(+) PEL cells. This suggests that KSHV is the driving force in the pathogenesis of PEL.     

Molecular biology of Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus

Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV/HHV8) are human gammaherpesviruses that are etiologic in the development of a variety of hematologic disorders. Infection with these viruses occurs worldwide. EBV is ubiquitous and its prevalence approaches 100% in most adult populations. Both viruses establish persistent latent infection in lymphocytes, which is usually benign. However, in the presence of other environmental, genetic, and iatrogenic cofactors, EBV or KSHV infection is associated with a variety of lymphoproliferative diseases and lymphoma. This chapter summarizes the molecular function of genes expressed during latent and lytic infections that may play a role in oncogenesis. Those aspects of viral gene function that prevent apoptosis, enhance proliferation, and escape from immune attack are emphasized, as these are likely to be important in malignant transformation.     

Viral lymphomas: can antivirals be used to treat cancer?

Current knowledge suggests that EBV, KSHV and HTLV-1 contribute to lymphomagenesis by subverting the host-cell molecular signaling machinery to deregulate cell growth and survival. Some signaling pathways that are affected by these viruses are well characterized, such as the NF-kB pathway, which is activated by these three viruses to promote cellular survival by inhibiting apoptosis, thereby playing a critical role in tumorigenesis. Other pathways, such as MTOR and JAK-STAT are also likely involved in viral lymphomagenesis. This provides the opportunity to inhibit these cellular pathways using drugs developed for the treatment of other malignancies. However, since these compounds target cellular proteins, they always have the potential for toxicity. In the context of viral malignancies, we have the unique opportunity of targeting viral proteins, and developing completely specific therapies. Here we will examine the question of whether the pathobiology of EBV, KSHV and HTLV-1 will allow the use of such an approach.     

An Epstein-Barr-related herpesvirus from marmoset lymphomas

Epstein-Barr virus (EBV) is implicated in the development of human B cell lymphomas and carcinomas. Although related oncogenic herpesviruses were believed to be endemic only in Old World primate species, we now find these viruses to be endemic in New World primates. We have isolated a transforming, EBV-related virus from spontaneous B cell lymphomas of common marmosets (Callithrix jacchus). Sequencing of two-thirds of the genome reveals considerable divergence from the genomes of EBV and Old World primate EBV-related viruses, including differences in genes important for virus-induced cell growth transformation and pathogenesis. DNA related to the C. jacchus herpesvirus is frequently detected in squirrel monkey peripheral blood lymphocytes, indicating that persistent infection with EBV-related viruses is prevalent in both New World primate families. Understanding how these more divergent EBV-related viruses achieve similar biologic outcomes in their natural host is likely to provide important insights into EBV infection, B cell growth transformation, and oncogenesis.     

Suppression of immediate-early viral gene expression by herpesvirus-coded microRNAs: implications for latency

A quantitative algorithm was developed and applied to predict target genes of microRNAs encoded by herpesviruses. Although there is almost no conservation among microRNAs of different herpesvirus subfamilies, a common pattern of regulation emerged. The algorithm predicts that herpes simplex virus 1, human cytomegalovirus, Epstein-Barr virus, and Kaposi's sarcoma-associated herpesvirus all employ microRNAs to suppress expression of their own genes, including their immediate-early genes. In the case of human cytomegalovirus, a virus-coded microRNA, miR-112-1, was predicted to target the viral immediate-early protein 1 mRNA. To test this prediction, mutant viruses were generated that were unable to express the microRNA, or encoded an immediate-early 1 mRNA lacking its target site. Analysis of RNA and protein within infected cells demonstrated that miR-UL112-1 inhibits expression of the major immediate-early protein. We propose that herpesviruses use microRNA-mediated suppression of immediate-early genes as part of their strategy to enter and maintain latency.     

Role and therapeutic potential of microRNAs in diabetes

The discovery in mammalian cells of hundreds of small RNA molecules, called microRNAs, with the potential to modulate the expression of the majority of the protein-coding genes has revolutionized many areas of biomedical research, including the diabetes field. MicroRNAs function as translational repressors and are emerging as key regulators of most, if not all, physiological processes. Moreover, alterations in the level or function of microRNAs are associated with an increasing number of diseases. Here, we describe the mechanisms governing the biogenesis and activities of microRNAs. We present evidence for the involvement of microRNAs in diabetes mellitus, by outlining the contribution of these small RNA molecules in the control of pancreatic β-cell functions and by reviewing recent studies reporting changes in microRNA expression in tissues isolated from diabetes animal models. MicroRNAs hold great potential as therapeutic targets. We describe the strategies developed for the delivery of molecules mimicking or blocking the function of these tiny regulators of gene expression in living animals. In addition, because changes in serum microRNA profiles have been shown to occur in association with different human diseases, we also discuss the potential use of microRNAs as blood biomarkers for prevention and management of diabetes.     

Interaction of Human Tumor Viruses with Host Cell Surface Receptors and Cell Entry

Currently, seven viruses, namely Epstein-Barr virus (EBV), Kaposi’s sarcoma-associated herpes virus (KSHV), high-risk human papillomaviruses (HPVs), Merkel cell polyomavirus (MCPyV), hepatitis B virus (HBV), hepatitis C virus (HCV) and human T cell lymphotropic virus type 1 (HTLV-1), have been described to be consistently associated with different types of human cancer. These oncogenic viruses belong to distinct viral families, display diverse cell tropism and cause different malignancies. A key to their pathogenicity is attachment to the host cell and entry in order to replicate and complete their life cycle. Interaction with the host cell during viral entry is characterized by a sequence of events, involving viral envelope and/or capsid molecules as well as cellular entry factors that are critical in target cell recognition, thereby determining cell tropism. Most oncogenic viruses initially attach to cell surface heparan sulfate proteoglycans, followed by conformational change and transfer of the viral particle to secondary high-affinity cell- and virus-specific receptors. This review summarizes the current knowledge of the host cell surface factors and molecular mechanisms underlying oncogenic virus binding and uptake by their cognate host cell(s) with the aim to provide a concise overview of potential target molecules for prevention and/or treatment of oncogenic virus infection.