Expression of Epstein-Barr virus transformation-associated genes in tissues of patients with EBV lymphoproliferative disease

Epstein-barr virus in gastric carcinoma

The Epstein-Barr virus (EBV) is detected in about 10% of gastric carcinoma cases throughout the world. In EBV-associated gastric carcinoma, all tumor cells harbor the clonal EBV genome. Gastric carcinoma associated with EBV has distinct clinicopathological features, occurs predominately in men and in younger-aged individuals, and presents a generally diffuse histological type. Most cases of EBV-associated gastric carcinoma exhibit a histology rich in lymphocyte infiltration. The immunological reactiveness in the host may represent a relatively preferable prognosis in EBV-positive cases. This fact highlights the important role of EBV in the development of EBV-associated gastric carcinoma. We have clearly proved direct infection of human gastric epithelialcells by EBV. The infection was achieved by using a recombinant EBV. Promotion of growth by EBV infection was observed in the cells. Considerable data suggest that EBV may directly contribute to the development of EBV-associated GC. This tumor-promoting effect seems to involve multiple mechanisms, because EBV affects several host proteins and pathways that normally promote apoptosis and regulate cell proliferation.

Human viruses and cancer

The first human tumor virus was discovered in the middle of the last century by Anthony Epstein, Bert Achong and Yvonne Barr in African pediatric patients with Burkitt's lymphoma. To date, seven viruses -EBV, KSHV, high-risk HPV, MCPV, HBV, HCV and HTLV1- have been consistently linked to different types of human cancer, and infections are estimated to account for up to 20% of all cancer cases worldwide. Viral oncogenic mechanisms generally include: generation of genomic instability, increase in the rate of cell proliferation, resistance to apoptosis, alterations in DNA repair mechanisms and cell polarity changes, which often coexist with evasion mechanisms of the antiviral immune response. Viral agents also indirectly contribute to the development of cancer mainly through immunosuppression or chronic inflammation, but also through chronic antigenic stimulation. There is also evidence that viruses can modulate the malignant properties of an established tumor. In the present work, causation criteria for viruses and cancer will be described, as well as the viral agents that comply with these criteria in human tumors, their epidemiological and biological characteristics, the molecular mechanisms by which they induce cellular transformation and their associated cancers.

Counteracting effects of cellular Notch and Epstein-Barr virus EBNA2: implications for stromal effects on virus-host interactions

A number of diverse environmental cues have been linked to B lymphocyte differentiation and activation. One such cue, Notch-2, may be particularly relevant to the biology of infection with Epstein-Barr virus (EBV), which colonizes the B cell compartment. Activated Notch and EBV nuclear antigen 2 (EBNA2) both function as transcriptional activators by virtue of their interactions with the transcription factor RBP-Jκ. Although EBNA2 and activated Notch appear to have partially overlapping functions, we now report that activated Notch counteracts a crucial EBNA2 function both in newly infected primary B cells and in lymphoblastoid cell lines (LCLs). EBNA2 is directly responsible for the initiation of transcription of the majority of EBV proteins associated with type III latency, leading to the outgrowth of LCLs. One of the key proteins driving this outgrowth is latent membrane protein 1 (LMP1), which is regulated by an EBNA2-responsive element within its ED-L1 promoter. Activation of Notch-2 via Delta-like ligand 1 inhibits EBNA2-mediated initiation of LMP1 transcription. Furthermore, ligated Notch-2 also efficiently turns off LMP1 expression from the ED-L1 promoter in LCLs already expressing LMP1. Modulation of EBV gene expression by Notch was not confined to EBNA2-dependent events. Activated Notch-2 also inhibited EBV entry into the lytic cycle in a B cell non-Hodgkin's lymphoma line by upregulating the cellular transcription factor Zeb2, which represses the transcription of BZLF1. These results support the concept that in vivo, cumulative signals from the microenvironment downregulate EBV gene expression in B cells to the latency 0 gene expression profile observed in B cells entering the peripheral blood. Importance: Experimental infection of resting B cells by Epstein-Barr virus leads to the growth transformation program of virus gene expression and the outgrowth of lymphoblastoid cell lines. Previous studies at the single-cell level revealed complex cellular and viral signaling networks regulating transcription of the viral genome. This study demonstrates that viral gene expression can also be radically altered by molecules expressed on stromal cells in the microenvironment of lymphoid tissue, specifically, Delta-like ligand 1 on stromal cells ligating Notch-2 on infected B cells. Activation of Notch interferes with the transactivation function of EBNA2, downregulates the expression of LMP1 and LMP2a, and inhibits the activation of lytic virus replication in a B cell non-Hodgkin's lymphoma line by preventing expression of BZLF1. The significance of these observations is that they indicate new mechanisms whereby the microenvironment in normal lymphoid tissue may facilitate the repression of viral gene expression, enabling establishment of true latency in memory B cells.

Co-infections, inflammation and oncogenesis: future directions for EBV research

Epstein-Barr virus (EBV) is aetiologically linked to a wide range of human tumours. Some arise as accidents of the virus' lifestyle in its natural niche, the B lymphoid system; these include B-lymphoproliferative disease of the immunocompromised, Hodgkin Lymphoma, Burkitt Lymphoma and particular forms of diffuse large B cell lymphoma. Interestingly, HIV infection increases the incidence of each of these B cell malignancies, though by different degrees and for different reasons. Other EBV-associated tumours arise through rare viral entry into unnatural target tissues; these include all cases of nasal T/NK cell lymphoma and of undifferentiated nasopharyngeal carcinoma plus a small but significant subset of gastric carcinomas, a tumour type more generally associated with chronic Helicobacter pylori infection. Understanding EBV's involvement in the pathogenesis of these different malignancies is an important long-term goal. This article focuses on two overlapping, but relatively neglected, areas of research that could contribute to that goal. The first addresses the mechanisms whereby coincident infections with other pathogens increase the risk of EBV-positive malignancies, and takes as its paradigm the actions of holoendemic malaria and HIV infections as co-factors in Burkitt lymphomagenesis. The second widens the argument to include both infectious and non-infectious sources of chronic inflammation in the pathogenesis of EBV-positive tumours such as T/NK cell lymphoma, nasopharyngeal carcinoma and gastric carcinoma.

Repression of the proapoptotic cellular BIK/NBK gene by Epstein-Barr virus antagonizes transforming growth factor β1-induced B-cell apoptosis

The Epstein-Barr virus (EBV) establishes a lifelong latent infection in humans. EBV infection of primary B cells causes cell activation and proliferation, a process driven by the viral latency III gene expression program, which includes EBV nuclear proteins (EBNAs), latent membrane proteins, and untranslated RNAs, including microRNAs. Some latently infected cells enter the long-lived memory B-cell compartment and express only EBNA1 transiently (Lat I) or no EBV protein at all (Lat 0). Targeting the molecular machinery that controls B-cell fate decisions, including the Bcl-2 family of apoptosis-regulating proteins, is crucial to the EBV cycle of infection. Here, we show that BIK (also known as NBK), which encodes a proapoptotic "sensitizer" protein, is repressed by the EBNA2-driven Lat III program but not the Lat I program. BIK repression occurred soon after infection of primary B cells by EBV but not by a recombinant EBV in which the EBNA2 gene had been knocked out. Ectopic BIK induced apoptosis in Lat III cells by a mechanism dependent on its BH3 domain and the activation of caspases. We show that EBNA2 represses BIK in EBV-negative B-cell lymphoma-derived cell lines and that this host-virus interaction can inhibit the proapoptotic effect of transforming growth factor β1 (TGF-β1), a key physiological mediator of B-cell homeostasis. Reduced levels of TGF-β1-associated regulatory SMAD proteins were bound to the BIK promoter in response to EBV Lat III or ectopic EBNA2. These data are evidence of an additional mechanism used by EBV to promote B-cell survival, namely, the transcriptional repression of the BH3-only sensitizer BIK.

IMPORTANCE

Over 90% of adult humans are infected with the Epstein-Barr virus (EBV). EBV establishes a lifelong silent infection, with its DNA residing in small numbers of blood B cells that are a reservoir from which low-level virus reactivation and shedding in saliva intermittently occur. Importantly, EBV DNA is found in some B-cell-derived tumors in which viral genes play a key role in tumor cell emergence and progression. Here, we report for the first time that EBV can shut off a B-cell gene called BIK. When activated by a molecular signal called transforming growth factor β1 (TGF-β1), BIK plays an important role in killing unwanted B cells, including those infected by viruses. We describe the key EBV-B-cell molecular interactions that lead to BIK shutoff. These findings further our knowledge of how EBV prevents the death of its host cell during infection. They are also relevant to certain posttransplant lymphomas where unregulated cell growth is caused by EBV genes.

Gene expression profiling of Epstein-Barr virus-positive diffuse large B-cell lymphoma of the elderly reveals alterations of characteristic oncogenetic pathways

Epstein–Barr virus (EBV)-positive diffuse large B-cell lymphoma (DLBCL) of the elderly (EBV[+]DLBCL-E) is classified as a subtype of DLBCL. Until now, its molecular pathogenesis has remained unknown. To identify pathways characteristic of EBV(+)DLBCL-E, gene expression profiling of five EBV(+)DLBCL-E and seven EBV-negative DLBCL (EBV[−]DLBCL) cases was undertaken using human oligonucleotide microarray analysis. Gene set enrichment analysis and gene ontology analysis showed that gene sets of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) and nuclear factor kappa B (NF-κB) pathways were enriched in EBV(+)DLBCL-E cases. To confirm the results of the expression profiles, in vitro analysis was performed. Expression profiling analysis showed that high activation of the JAK-STAT and NF-κB pathways was induced by EBV infection into DLBCL cell lines. Activation of the NF-κB pathway was confirmed in EBV-infected cell lines using an electrophoretic mobility shift assay. Western blot analysis revealed an increased protein expression level of phosphorylated signal transducer and activator of transcription 3 (STAT3) in an EBV-infected cell line. Protein expression of phosphorylated STAT3 was frequently observed in lymphoma cells of EBV(+)DLBCL-E clinical samples using immunohistochemistry (EBV[+]DLBCL-E: 80.0% [n = 20/25] versus EBV[−]DLBCL: 38.9% [n = 14/36]; P = 0.001). The results of the present study suggest that activation of the JAK-STAT and NF-κB pathways was characteristic of EBV(+)DLBCL-E, which may reflect the nature of EBV-positive tumor cells. Targeting these pathways as therapies might improve clinical outcomes of EBV(+)DLBCL-E.

Small molecule inhibition of Epstein-Barr virus nuclear antigen-1 DNA binding activity interferes with replication and persistence of the viral genome

The replication and persistence of extra chromosomal Epstein-Barr virus (EBV) episome in latently infected cells are primarily dependent on the binding of EBV-encoded nuclear antigen 1 (EBNA1) to the cognate EBV oriP element. In continuation of the previous study, herein we characterized EBNA1 small molecule inhibitors (H20, H31) and their underlying inhibitory mechanisms. In silico docking analyses predicted that H20 fits into a pocket in the EBNA1 DNA binding domain (DBD). However, H20 did not significantly affect EBNA1 binding to its cognate sequence. A limited structure-relationship study of H20 identified a hydrophobic compound H31, as an EBNA1 inhibitor. An in vitro EBNA1 EMSA and in vivo EGFP-EBNA1 confocal microscopy analysis showed that H31 inhibited EBNA1-dependent oriP sequence-specific DNA binding activity, but not sequence-nonspecific chromosomal association. Consistent with this, H31 repressed the EBNA1-dependent transcription, replication, and persistence of an EBV oriP plasmid. Furthermore, H31 induced progressive loss of EBV episome. In addition, H31 selectively retarded the growth of EBV-infected LCL or Burkitt's lymphoma cells. These data indicate that H31 inhibition of EBNA1-dependent DNA binding decreases transcription from and persistence of EBV episome in EBV-infected cells. These new compounds might be useful probes for dissecting EBNA1 functions in vitro and in vivo.

The labyrinth of interactions of Epstein-Barr virus-encoded small RNAs

Epstein-Barr Virus (EBV) is an oncogenic herpesvirus implicated in the pathogenesis of a number of human malignancies. However, the mechanism by which EBV leads to malignant transformation is not clear. A number of viral latent gene products, including non-protein coding small RNAs, are believed to be involved. Epstein-Barr virus-encoded RNA 1 (EBER1) and EBER2 are two such RNA molecules that are abundantly expressed (up to 10(7) copies) in all EBV-infected cells, but their function remains poorly understood. These polymerase III transcripts have extensive secondary structure and exist as ribonucleoproteins. An accumulating body of evidence suggests that EBERs play an important role, directly or indirectly, in EBV-induced oncogenesis. Here, we summarize the current understanding of the complex interactions of EBERs with various cellular factors and the potential pathways by which these small RNAs are able to influence EBV-infected cells to proliferate and to induce tumorigenesis. The exosome pathway is probably involved in the cellular excretion of EBERs and facilitating some of their biological effects.

Identification of genes specifically methylated in Epstein-Barr virus-associated gastric carcinomas

We studied the comprehensive DNA methylation status in the naturally derived gastric adenocarcinoma cell line SNU-719, which was infected with the Epstein-Barr virus (EBV) by methylated CpG island recovery on chip assay. To identify genes specifically methylated in EBV-associated gastric carcinomas (EBVaGC), we focused on seven genes, TP73, BLU, FSD1, BCL7A, MARK1, SCRN1, and NKX3.1, based on the results of methylated CpG island recovery on chip assay. We confirmed DNA methylation of the genes by methylation-specific PCR and bisulfite sequencing in SNU-719. The expression of the genes, except for BCL7A, was upregulated by a combination of 5-Aza-2'-deoxycytidine and trichostatin A treatment in SNU-719. After the treatment, unmethylated DNA became detectable in all seven genes by methylation-specific PCR. We verified DNA methylation of the genes in 75 primary gastric cancer tissues from 25 patients with EBVaGC and 50 EBV-negative patients who were controls. The methylation frequencies of TP73, BLU, FSD1, BCL7A, MARK1, SCRN1, and NKX3.1 were significantly higher in EBVaGC than in EBV-negative gastric carcinoma. We identified seven genes with promoter regions that were specifically methylated in EBVaGC. Inactivation of these genes may suppress their function as tumor suppressor genes or tumor-associated antigens and help to develop and maintain EBVaGC.

Viral genome maintenance and latent replication of human gammaherpesviruses

During gammaherpesvirus latency, only a few genes are expressed and required for maintenance of viral latency over a long period. While the expressed latent viral proteins play functional roles in viral latent DNA replication, they do not have replication-associated enzymatic activity such as polymerase or helicase activity. Viral genomes are detected in a similar copy number per infected cell, suggesting that the viral genome is replicated and segregated using host replication machinery. Kaposi’s sarcoma-associated herpesvirus and EBV have trans-acting elements required for viral genome maintenance during latency; LANA1 and EBNA1, respectively. The proteins recruit host replication-associated proteins at their latent origins, leading to initiation of viral replication and segregation with host chromosomes once per cell cycle. In addition, viral latent origins (cis-elements) provide trans-element-binding sites as well as a sufficient space for recruitment of cellular factors. In this review, we describe the molecular mechanisms required for replication of the viral genome during latency, including interactions with cellular factors and the interplay between viral trans- and cis-elements.

Therapeutic options in post-transplant lymphoproliferative disorders

Post-transplantation lymphoproliferative disorders (PTLD) are the second most frequent malignancies after solid organ transplantation and cover a wide spectrum ranging from polyclonal early lesions to monomorphic lymphoma. Available treatment modalities include immunosuppression reduction, immunotherapy with anti-B-cell monoclonal antibodies, chemotherapy, antiviral therapy, cytotoxic T-cell therapy as well as surgery and irradiation. Owing to the small number of cases and the heterogeneity of PTLD, current treatment strategies are mostly based on case reports and small, often retrospective studies. Moreover, many studies on the treatment of PTLD have involved a combination of different treatment options, complicating the evaluation of individual treatment components. However, there has been significant progress over the last few years. Three prospective phase II trials on the efficacy of rituximab monotherapy have shown significant complete remission rates without any relevant toxicity. A prospective, multicenter, international phase II trial evaluating sequential treatment with rituximab and CHOP-based chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone) is ongoing and preliminary results have been promising. Cytotoxic T-cell therapy targeting Epstein-Barr virus (EBV)-infected B cells has shown low toxicity and high efficacy in a phase II trial and will be a future therapeutic option at specialized centers. Here, we review the currently available data on the different treatment modalities with a focus on PTLD following solid organ transplantation in adult patients.

Uncommon gastrointestinal complications after liver transplantation: radiologic findings and clinical features

There are various uncommon gastrointestinal complications, as liver transplantation becomes increasingly popular as the only curative method for patients with end-stage liver diseases. It is important for radiologists evaluating postoperative liver transplantation recipients to have a perspective on the possible gastrointestinal complications after liver transplantation and their radiologic features for early detection and early treatment. This article illustrates radiologic findings and clinical features of various uncommon gastrointestinal complications after liver transplantation.

Epstein-Barr virus infection and posttransplant lymphoproliferative disorder

Epstein-Barr virus (EBV) is an important pathogen in recipients of solid organ transplants (SOT). Infection with EBV manifests as a spectrum of diseases/malignancies ranging from asymptomatic viremia through infectious mononucleosis to posttransplant lymphoproliferative disorder (PTLD). EBV disease and its associated PTLD is more frequently seen when primary EBV infection occurs after transplant, a common scenario in pediatric SOT recipients. Intensity of immunosuppressive therapies also influences the risk for PTLD. The use of EBV viral load monitoring facilitates the diagnosis and management of EBV/PTLD as well as being used to inform preemptive therapy with reduction of immunosuppression, the most effective intervention for prevention of and treatment for PTLD. Other therapies, including the rituximab (anti-CD20 monoclonal antibody) and traditional chemotherapy, are also useful in the treatment of established PTLD. The future development of standards for management based on EBV viral load and routine monitoring of EBV-specific CTL responses promise further improvement in outcomes with EBV and PTLD.

Identification of transmembrane protein 134 as a novel LMP1-binding protein by using bimolecular fluorescence complementation and an enhanced retroviral mutagen

Latent membrane protein 1 (LMP1) of Epstein-Barr virus induces constitutive signaling in infected cells. LMP1 signaling requires oligomerization of LMP1 via its transmembrane domain, localization to lipid rafts in the membrane, and association of the LMP1 cytoplasmic domain to adaptor proteins, such as the tumor necrosis factor receptor-associated factors (TRAFs). Protein complementation is a novel technique to examine protein-protein interaction through the assembly of functional fluorescent proteins or enzymes from inactive fragments. A previous study in our lab demonstrated the use of bimolecular fluorescence complementation (BiFC) to study the assembly of the LMP1 signaling complexes within the plasma membrane of mammalian cells. In the present study, LMP1 was used as bait in a genome-wide BiFC screen with an enhanced retroviral mutagen to identify new LMP1-binding proteins. Our screen identified a novel LMP1-binding protein, transmembrane protein 134 (Tmem134). Tmem134 is a candidate oncogene that is amplified in breast cancer cell lines. Binding, colocalization, and cofractionation between LMP1 and Tmem134 were confirmed. Finally, Tmem134 affected LMP1-induced NF-κB induction. Together, these data suggest that BiFC is a unique and novel platform to identify proteins recruited to the LMP1-signaling complex.

Hepatitis C virus infection can affect lymphoproliferative disorders only as a cofactor for Epstein-Barr virus in liver transplant recipients: PTLD.Int survey

OBJECTIVES

Hepatitis C virus infection has a 10.5% frequency in liver transplant posttransplant lymphoproliferative disorders. Studies have suggested that hepatitis C virus infection plays a role in developing posttransplant lymphoproliferative disorders. Pooling data of posttransplant lymphoproliferative disorders developing in liver recipients from the literature, we analyzed and compared characteristics, behavior, and prognoses of posttransplant lymphoproliferative disorders arising in hepatitis C virus-positive versus negative liver graft recipients.

MATERIALS AND METHODS

We conducted a search for the available data though PubMed and Google Scholar for reports of posttransplant lymphoproliferative disorders and hepatitis C virus infection in liver transplant recipients. Overall, 29 studies were found and their data are included in the analyses.

RESULTS

Overall, data of 212 liver transplant patients were included. Sixty-three percent were male. No difference was found between hepatitis C virus-positive liver transplant patients with posttransplant lymphoproliferative disorders compared to their hepatitis C virus-negative counterparts regarding sex, time from transplant to lymphoma development, lymphoma cell type, remission, mortality rate, multiorgan involvement, disseminated posttransplant lymphoproliferative disorders, and histopathologic evaluations (P > .1 for all). Hepatitis C virus-positive liver transplant recipients representing posttransplant lymphoproliferative disorders who were concomitantly positive for Epstein-Barr virus were significantly more likely to develop lymphomas in the early posttransplant period (26 [67%] vs 16 [40%]; P = .024) and to complicate liver (19 [63%] vs 8 [30%]; P = .017) than hepatitis C virus-/Epstein-Barr virus+ patients.

CONCLUSIONS

Hepatitis C virus infection alone has no significant effect on lymphoproliferative disorders after liver transplant; but when combined with Epstein-Barr virus infection, it represents some significant different presentations of the disease. However, no survival effect was found for hepatitis C virus with or without simultaneous Epstein-Barr virus infection, in the posttransplant lymphoproliferative disorders setting. Future prospective studies are needed for confirming our results.

Microbiome and malignancy

Current knowledge is insufficient to explain why only a proportion of individuals exposed to environmental carcinogens or carrying a genetic predisposition to cancer develop disease. Clearly, other factors must be important, and one such element that has recently received attention is the human microbiome, the residential microbes including Bacteria, Archaea, Eukaryotes, and viruses that colonize humans. Here, we review principles and paradigms of microbiome-related malignancy, as illustrated by three specific microbial-host interactions. We review the effects of the microbiota on local and adjacent neoplasia, present the estrobolome model of distant effects, and discuss the complex interactions with a latent virus leading to malignancy. These are separate facets of a complex biology interfacing all the microbial species we harbor from birth onward toward early reproductive success and eventual senescence.

Contributions of CTCF and DNA methyltransferases DNMT1 and DNMT3B to Epstein-Barr virus restricted latency

Establishment of persistent Epstein-Barr virus (EBV) infection requires transition from a program of full viral latency gene expression (latency III) to one that is highly restricted (latency I and 0) within memory B lymphocytes. It is well established that DNA methylation plays a critical role in EBV gene silencing, and recently the chromatin boundary protein CTCF has been implicated as a pivotal regulator of latency via its binding to several loci within the EBV genome. One notable site is upstream of the common EBNA gene promoter Cp, at which CTCF may act as an enhancer-blocking factor to initiate and maintain silencing of EBNA gene transcription. It was previously suggested that increased expression of CTCF may underlie its potential to promote restricted latency, and here we also noted elevated levels of DNA methyltransferase 1 (DNMT1) and DNMT3B associated with latency I. Within B-cell lines that maintain latency I, however, stable knockdown of CTCF, DNMT1, or DNMT3B or of DNMT1 and DNMT3B in combination did not result in activation of latency III protein expression or EBNA gene transcription, nor did knockdown of DNMTs significantly alter CpG methylation within Cp. Thus, differential expression of CTCF and DNMT1 and -3B is not critical for maintenance of restricted latency. Finally, mutant EBV lacking the Cp CTCF binding site exhibited sustained Cp activity relative to wild-type EBV in a recently developed B-cell superinfection model but ultimately was able to transition to latency I, suggesting that CTCF contributes to but is not necessarily essential for the establishment of restricted latency.

Newly emerging therapies targeting viral-related lymphomas

Gamma-(γ)-herpes virus lymphomas comprise a heterogenous group of B-cell and T-cell neoplasms most commonly associated with Epstein-Barr virus and rarely human herpes virus-8 infection. Adult T-cell leukemia/lymphoma (ATLL) is a unique disease entity caused by the human T-cell lymphotrophic virus, type 1 (HTLV-I), the only retrovirus known to cause cancer in humans. Viral lymphomas behave aggressively and disproportionally affect immunocompromised individuals and those living in underdeveloped regions. These diseases are often difficult to treat with conventional approaches. Despite recent advancements using cytotoxic, lymphoma-specific, and adoptive therapies, the long-term outcome of patients with γ-herpesvirus lymphomas occurring in severely immunocompromised patients and ATLL continues to be poor. Lytic-inducing therapies targeting NF-κB, and viral and tumor cell epigenetic mechanisms afford the advantage of exploiting the intrinsic presence of oncogenic viruses to eradicate infected tumor cells. In this review, viral-related lymphomas and newly emerging clinical approaches targeting viral latency are discussed.

Deciphering the role of Epstein-Barr virus in the pathogenesis of T and NK cell lymphoproliferations

Epstein-Barr virus (EBV) is a highly successful herpesvirus, colonizing more than 90% of the adult human population worldwide, although it is also associated with various malignant diseases. Primary infection is usually clinically silent, and subsequent establishment of latency in the memory B lymphocyte compartment allows persistence of the virus in the infected host for life. EBV is so markedly B-lymphotropic when exposed to human lymphocytes in vitro that the association of EBV with rare but distinct types of T and NK cell lymphoproliferations was quite unexpected. Whilst relatively rare, these EBV-associated T and NK lymphoproliferations can be therapeutically challenging and prognosis for the majority of patients is dismal. In this review, we summarize the current knowledge on the role of EBV in the pathogenesis of these tumours, and the implications for treatment.

A multiplex calibrated real-time PCR assay for quantitation of DNA of EBV-1 and 2

Accurate and highly sensitive tests for the diagnosis of active Epstein-Barr virus (EBV) infection are essential for the clinical management of individuals infected with EBV. A calibrated quantitative real-time PCR assay for the measurement of EBV DNA of both EBV-1 and 2 subtypes was developed, combining the detection of the EBV DNA and a synthetic DNA calibrator in a multiplex PCR format. The assay displays a wide dynamic range and a high degree of accuracy even in the presence of 1μg of human genomic DNA. This assay measures with the same efficiency EBV DNA from strains prevalent in different geographic areas. The clinical sensitivity and specificity of the system were evaluated by testing 181 peripheral blood mononuclear cell (PBMCs) and plasma specimens obtained from 21 patients subjected to bone marrow transplantation, 70 HIV-seropositive subjects and 23 healthy controls. Patients affected by EBV-associated post-transplant lymphoprolipherative disorders had the highest frequency of EBV detection and the highest viral load. Persons infected with HIV had higher levels of EBV DNA load in PBMCs and a higher frequency of EBV plasma viremia compared to healthy controls. In conclusion, this new assay provides a reliable high-throughput method for the quantitation of EBV DNA in clinical samples.

Characterization of the latent membrane protein 1 signaling complex of Epstein-Barr virus in the membrane of mammalian cells with bimolecular fluorescence complementation

Background

Bimolecular fluorescence complementation (BiFC) is a novel technique to examine protein-protein interaction through the assembly of fluorescent proteins. In the present study, BiFC was used to study the assembly of the Epstein-Barr virus latent membrane protein 1 (LMP1) signaling complex within the membrane of mammalian cells. LMP1 signaling requires oligomerization, localization to lipid rafts, and association of the cytoplasmic domain to adaptor proteins, such as the tumor necrosis factor receptor associated factors (TRAFs).

Methods

LMP1-TRAF and LMP1-LMP1 interactions were assayed by BiFC using fluorescence microscopy and flow cytometry. Function of LMP1 BiFC contructs were confirmed by transformation assays and nuclear factor- κB (NF-κB) reporter assays.

Results

BiFC was observed between LMP1 and TRAF2 or TRAF3 and mutation of the LMP1 signaling domains reduced complementation. Fluorescence was observed in previously described LMP1 signaling locations. Oligomerization of LMP1 with itself induced complementation and BiFC. LMP1-BiFC constructs were fully functional in rodent fibroblast transformation assays and activation of NF-κB reporter activity. The BiFC domain partially suppressed some LMP1 mutant phenotypes.

Conclusions

Together these data suggest that BiFC is a unique and novel platform to identify and characterize proteins recruited to the LMP1-signaling complex.

trans-Repression of protein expression dependent on the Epstein-Barr virus promoter Wp during latency

An ordered silencing of Epstein-Barr virus (EBV) latency gene transcription is critical for establishment of persistent infection within B lymphocytes, yet the mechanisms responsible and the role that the virus itself may play are unclear. Here we describe two B-cell superinfection models with which to address these problems. In the first, Burkitt lymphoma (BL) cells that maintain latency I, when superinfected, initially supported transcription from the common EBNA promoters Wp and Cp (latency III) but ultimately transitioned to latency I (Cp/Wp silent), an essential requirement for establishment of EBV latency in vivo. We used this model to test whether the early lytic-cycle gene BHLF1, implicated in silencing of the Cp/Wp locus, is required to establish latency I. Upon superinfection with EBV deleted for the BHLF1 locus, however, we have demonstrated that BHLF1 is not essential for this aspect of EBV latency. In the second model, BL cells that maintain Wp-restricted latency, a variant program in which Cp is silent but Wp remains active, sustained the latency III program of transcription from the superinfecting-virus genomes, failing to transition to latency I. Importantly, there was substantial reduction in Wp-mediated protein expression from endogenous EBV genomes, in the absence of Cp reactivation, that could occur independent of a parallel decrease in mRNA. Thus, our data provide evidence of a novel, potentially posttranscriptional mechanism for trans-repression of Wp-dependent gene expression. We suggest that this may ensure against overexpression of the EBV nuclear antigens (EBNAs) prior to the transcriptional repression of Wp in cis that occurs upon activation of Cp.

Epstein-Barr virus infection in transplant recipients: Summary of a workshop on surveillance, prevention and treatment

Diseases caused by the Epstein-Barr virus are of great significance among organ transplant recipients. One of these diseases, post-transplant lymphoproliferative disease, is a major complication among organ transplant recipients. Management of this entity is problematic due to the difficulties with laboratory surveillance, diagnosis, prevention and treatment. A group of Canadian and American experts was assembled to discuss these aspects of Epstein-Barr virus diseases in Canadian organ transplant recipients. This report summarizes the relevant background literature and levels of evidence in relation to the outcomes of the deliberations and recommendations by the expert panel.

AIDS-Related EBV-Associated Smooth Muscle Tumors: A Review of 64 Published Cases

The number of reported cases of smooth muscle tumor (SMT) arising in patients with AIDS has been increasing since the mid-1990s. The aim of this study is to characterize the epidemiology, clinical manifestations, pathologic features, prognosis and, management of Epstein-Barr virus-related SMT (EBV-SMT) in patients with AIDS. An English language literature search identified 53 articles including 64 reported cases of EBV-SMT. The majority of these reports involved patients who were young, severely immunosuppressed, and had multifocal tumors. The central nervous system was the most common site to be involved. Histologically, tumors had smooth muscle features and were immunoreactive for muscle markers and all but two tumors demonstrated the presence of EBV by either immunohistochemistry, in situ hybridization, and/or PCR. While mitoses and/or necrosis were used to separate leiomyoma from leiomyosarcoma, these features did not correlate with clinical outcome. Treatment included primarily resection, and less often radiotherapy, chemotherapy and highly active antiretroviral therapy (HAART). Overall, EBV-SMTs appear to have variable aggressiveness and clinical outcome and may exhibit a more favorable prognosis compared to conventional leiomyosarcoma. Tumor-related death from EBV-SMT occurred in only 4 of 51 patients.

Roscovitine inhibits EBNA1 serine 393 phosphorylation, nuclear localization, transcription, and episome maintenance

Latent Epstein-Barr virus (EBV) infection causes human lymphomas and carcinomas. EBV usually persists as an episome in malignant cells. EBV episome persistence, replication, and gene expression are dependent on EBNA1 binding to multiple cognate sites in oriP. To search for inhibitors of EBNA1- and oriP-dependent episome maintenance or transcription, a library of 40,550 small molecules was screened for compounds that inhibit EBNA1- and oriP-dependent transcription and do not inhibit EBNA1- and oriP-independent transcription. This screening identified roscovitine, a selective inhibitor of cyclin-dependent kinase 1 (CDK1), CDK2, CDK5, and CDK7. Based on motif predictions of EBNA1 serine 393 as a CDK phosphorylation site and (486)RALL(489) and (580)KDLVM(584) as potential cyclin binding domains, we hypothesized that cyclin binding to EBNA1 may enable CDK1, -2, -5, or -7 to phosphorylate serine 393. We found that Escherichia coli-expressed EBNA1 amino acids 387 to 641 were phosphorylated in vitro by CDK1-, -2-, -5-, and -7/cyclin complexes and serine 393 phosphorylation was roscovitine inhibited. Further, S393A mutation abrogated phosphorylation. S393A mutant EBNA1 was deficient in supporting EBNA1- and oriP-dependent transcription and episome persistence, and roscovitine had little further effect on the diminished S393A mutant EBNA1-mediated transcription or episome persistence. Immunoprecipitated FLAG-EBNA1 was phosphorylated in vitro, and roscovitine inhibited this phosphorylation. Moreover, roscovitine decreased nuclear EBNA1 and often increased cytoplasmic EBNA1, whereas S393A mutant EBNA1 was localized equally in the nucleus and cytoplasm and was unaffected by roscovitine treatment. These data indicate that roscovitine effects are serine 393 specific and that serine 393 is important in EBNA1- and oriPCp-dependent transcription and episome persistence.

A novel latent membrane 2 transcript expressed in Epstein-Barr virus-positive NK- and T-cell lymphoproliferative disease encodes a target for cellular immunotherapy

Therapeutic targeting of virus-encoded proteins using cellular immunotherapy has proved successful for Epstein-Barr virus (EBV)-associated posttransplant lymphoproliferative disease. However, the more limited repertoire and immunogenicity of EBV-encoded proteins in other malignancies such as Hodgkin lymphoma and extranodal natural killer (NK)/T lymphoma has been more challenging to target. The immunosubdominant latent membrane protein 2 (LMP2) is considered the optimal target in such Latency II tumors, although data relating to its expression in T/NK malignancies are limited. In addressing the validity of LMP2 as an immunotherapeutic target we found that LMP2-specific effector CD8(+) T cells recognized and killed EBV-positive NK- and T-cell tumor lines, despite an apparent absence of LMP2A protein and barely detectable levels of LMP2 transcripts from the conventional LMP2A and LMP2B promoters. We resolved this paradox by identifying in these lines a novel LMP2 mRNA, initiated from within the EBV terminal repeats and containing downstream, epitope-encoding exons. This same mRNA was also highly expressed in primary (extra-nodal) NK/T lymphoma tissue, with virtually undetectable levels of conventional LMP2A/B transcripts. Expression of this novel transcript in T/NK-cell lymphoproliferative diseases validates LMP2 as an attractive target for cellular immunotherapy and implicates this truncated LMP2 protein in NK- and T-cell lymphomagenesis. This study is registered at clinicaltrials.gov as NCT00062868.

Quantitative studies of Epstein-Barr virus-encoded microRNAs provide novel insights into their regulation

Epstein-Barr virus (EBV) has been shown to encode at least 40 microRNAs (miRNAs), an important class of molecules that negatively regulate the expression of many genes through posttranscriptional mechanisms. Here, we have used real-time PCR assays to quantify the levels of EBV-encoded BHRF1 and BART miRNAs in latently infected cells and in cells induced into the lytic cycle. During latency, BHRF1 miRNAs were seen only in cells with detectable Cp- and/or Wp-initiated EBNA transcripts, while the BART miRNAs were expressed in all forms of latent infection. Surprisingly, levels of different BART miRNAs were found to vary up to 50-fold within a cell line. However, this variation could not be explained by differential miRNA turnover, as all EBV miRNAs appeared to be remarkably stable. Following entry into the virus lytic cycle, miR-BHRF1-2 and -1-3 were rapidly induced, coincident with the onset of lytic BHRF1 transcripts, while miR-BHRF1-1 expression was delayed until 48 h and correlated with the appearance of Cp/Wp-initiated EBNA transcripts. In contrast, levels of BART miRNAs were relatively unchanged during virus replication, despite dramatic increases in BART transcription. Finally, we show that BHRF1 and BART miRNAs were delayed relative to the induction of BHRF1 and BART transcripts in freshly infected primary B cell cultures. In summary, our data show that changes in BHRF1 and BART transcription are not necessarily reflected in altered miRNA levels, suggesting that miRNA maturation is a key step in regulating steady-state levels of EBV miRNAs.

STAT6 signaling pathway activated by the cytokines IL-4 and IL-13 induces expression of the Epstein-Barr virus-encoded protein LMP-1 in absence of EBNA-2: implications for the type II EBV latent gene expression in Hodgkin lymphoma

In line with the B-lymphotropic nature of Epstein-Barr virus (EBV), the virus is present in several types of B-cell lymphomas. EBV expresses a different set of latent genes in the associated tumors, such as EBV nuclear antigen 1 (EBNA-1) and latent membrane proteins (LMPs; type II latency) in classical Hodgkin lymphomas (HLs). We previously reported that exposure of in vitro EBV-converted, HL-derived cell line KMH2-EBV to CD40-ligand and interleukin-4 (IL-4) induced the expression of LMP-1. Here, we show that exposure to IL-4 or IL-13 alone induced LMP-1 in the absence of EBNA-2. Induction of LMP-1 by IL-4 and IL-13 was mediated by the signal transducer signal transducer and activator of transcription 6 (STAT6) and a newly defined high-affinity STAT6-binding site in the LMP-1 promoter. IL-4 induced LMP-1 also in Burkitt lymphoma-derived lines and in tonsillar B cells infected with the EBNA-2-deficient EBV strain P3HR-1. Furthermore, coculture of EBV-carrying Burkitt lymphoma cells with activated CD4(+) T cells resulted in the induction of LMP-1 in the absence of EBNA-2. Because Hodgkin/Reed-Sternberg cells are known to secrete IL-13, to have constitutively activated STAT6, and to be closely surrounded by CD4(+) T cells, these mechanisms may be involved in the expression of LMP-1 in EBV-positive chronic HLs.

Expansion of EBNA1-specific effector T cells in posttransplantation lymphoproliferative disorders

Immunosuppression resulting in impaired Epstein-Barr virus (EBV)-specific T-cell immunity is involved in the pathogenesis of EBV-positive post-transplantation lymphoproliferative disorder (EBV(+) PTLD). Restoration of EBV-specific T-cell immunity by adoptive immunotherapy can induce remission. EBV-nuclear antigen-1 (EBNA1) is unique in being expressed in all cases of EBV(+) PTLD. Recent data demonstrate that EBNA1 is not immunologically silent and can be exploited as a T-cell target. There are no data on EBNA1-specific T cells in PTLD. EBNA1-specific T cells capable of proliferation, interferon-γ release, and CD107a/b degranulation were assayed in 14 EBV(+) PTLD diagnostic blood samples and 19 healthy controls. EBNA1-specific CD4(+) T cells predominated and were expanded in 10 of 14 patients and 19 of 19 controls. Although human leukocyte antigen class I alleles influenced the magnitude of the response, EBNA1-specific CD8(+) effector T cells were successfully generated in 9 of 14 EBV(+) PTLD patients and 16 of 19 controls. The majority of PTLD patients had a polymorphism in an EBNA1 epitope, and T-cell recognition was greatly enhanced when EBNA1 peptides derived from the polymorphic epitope were used. These results indicate that EBNA1-specific T cells should be included in adoptive immunotherapy for PTLD. Furthermore, expansion protocols should use antigenic sequences from relevant EBV strains.

Early and late virological monitoring of cytomegalovirus, Epstein-Barr virus, and human herpes virus 6 infections in small bowel/multivisceral transplant recipients

BACKGROUND

Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) are the major causes of graft failure and posttransplantation mortality among small bowel and multivisceral transplantations (SB/MVT). Little is known about human herpes virus 6 (HHV-6) infections in transplant recipients.

STUDY PURPOSE

The purposes of this study were to analyze the clinical relevance of CMV, EBV, and HHV-6 infections after small bowel transplantation and to establish whether routine monitoring for HHV-6 infection should be recommended for the prevention of severe complications in this population.

METHODS

Ten adult patients were monitored based on CMV, EBV, and HHV6 DNA quantifications in blood and biopsy tissue samples. Three patients were monitored for at least 5 months (early period) and 7 patients were monitored for 1 to 5 years after transplantation (late period).

RESULTS

In the early period, despite prophylaxis all 3 patients developed symptomatic CMV infections: 1 fever/diarrhea, 1 enteritis and rejection, as well as 1 fever and pneumonia. Only 1 patient developed EBV and HHV-6 infections. The average time of onset of CMV infection was 3 months after transplantation and only 24 days for HHV6 infection. In the late period, of the 7 SB/MVT recipients only 1 developed an EBV infection at 2 years after transplantation. No CMV or HHV-6 infections were identified in any patient.

CONCLUSIONS

CMV infection is a major cause of organ disease and rejection in the early period after transplantation. EBV infection in adult recipients must be considered also in the late period, particularly in association with severe immunosuppression. Because HHV-6 infection occurs earlier than CMV/EBV, it may serve as an indicator for more intense virological surveillance.

Post-transplant lymphoproliferative disorder in pediatric heart transplant recipients

BACKGROUND

Post-transplantation lymphoproliferative disorder (PTLD) is a major cause of morbidity and mortality after pediatric heart transplantation.

METHODS

Heart transplant recipients at The Hospital for Sick Children, Toronto, from 1990 to May 2008, were reviewed. Competing risk hazard analysis was used to model the natural history of the disease. Patients were matched for gender and duration of follow-up to identify potential covariates associated with increased risk of PTLD.

RESULTS

A total of 173 heart transplant recipients (42% <1 year old) were reviewed. Twenty-three developed PTLD at a median of 4 years post-transplantation. After transplantation, PTLD affected 9%, 15% and 28% at 3, 5 and 10 years, respectively. Freedom from death or PTLD recurrence was 72%, 58% and 50% at 1, 3 and 5 years, respectively, after PTLD diagnosis. Higher maximum Epstein-Barr viral (EBV) load (hazard ratio [HR]: 2.6, p = 0.004) and longer duration of induction therapy (HR: 1.7, p = 0.02) were associated with increased risks of PTLD. Higher cumulative cyclosporine doses over the first year post-transplantation were associated with increased risks of PTLD (HR: 1.2 per 1 mg/kg/day equivalent, p = 0.03), but higher tacrolimus doses were not (p = 0.38). Patients on cyclosporine at 6 months post-transplantation were at higher risk of PTLD than those on tacrolimus (HR: 5.2, p = 0.003). The use of anti-viral prophylaxis in patients with high EBV load may provide some protection (HR: 7.6 vs 15.4 with no anti-viral, p = 0.02).

CONCLUSIONS

PTLD is a major concern in pediatric heart transplant recipients and is associated with high morbidity/mortality. Exposure to EBV and higher intensity of immunosuppression seems to be associated with increased risk.

Effect of reduced immunosuppression after kidney transplant failure on risk of cancer: population based retrospective cohort study

OBJECTIVE

To compare cancer incidence in kidney transplant recipients during periods of transplant function (and immunosuppression) and after transplant failure (when immunosuppression is ceased or reduced). Design, setting, and participants Nationwide, population based retrospective cohort study of 8173 Australian kidney transplant recipients registered on the Australia and New Zealand Dialysis and Transplant Registry who first received a transplant during 1982-2003. Incident cancers were ascertained using linkage with national cancer registry records.

MAIN OUTCOME MEASURES

Cancer-specific standardised incidence ratios for periods of transplant function and for dialysis after transplant failure. Incidence was compared between periods using multivariate incidence rate ratios adjusted for current age, sex, and duration of transplantation.

RESULTS

All cases of Kaposi's sarcoma occurred during transplant function. Standardised incidence ratios were significantly elevated during transplant function, but not during dialysis after transplant failure, for non-Hodgkin's lymphoma, lip cancer, and melanoma. For each of these cancers, incidence was significantly lower during dialysis after transplant failure in multivariate analysis (incidence rate ratios 0.20 (95% CI 0.06 to 0.65) for non-Hodgkin's lymphoma, 0.04 (0.01 to 0.31) for lip cancer, and 0.16 (0.04 to 0.64) for melanoma). In contrast, standardised incidence ratios during dialysis after transplant failure remained significantly elevated for leukaemia and lung cancer, and cancers related to end stage kidney disease (kidney, urinary tract, and thyroid cancers), with thyroid cancer incidence significantly higher during dialysis after transplant failure (incidence rate ratio 6.77 (2.64 to 17.39)). There was no significant difference in incidence by transplant function for other cancers.

CONCLUSIONS

The effect of immunosuppression on cancer risk is rapidly reversible for some, but not all, cancer types. Risk reversal was mainly observed for cancers with a confirmed infectious cause. Risk of other cancers, especially those related to end stage kidney disease, remained significantly increased after reduction of immunosuppression.

Regulation of microtubule dynamics through phosphorylation on stathmin by Epstein-Barr virus kinase BGLF4

Stathmin is an important microtubule (MT)-destabilizing protein, and its activity is differently attenuated by phosphorylation at one or more of its four phosphorylatable serine residues (Ser-16, Ser-25, Ser-38, and Ser-63). This phosphorylation of stathmin plays important roles in mitotic spindle formation. We observed increasing levels of phosphorylated stathmin in Epstein-Barr virus (EBV)-harboring lymphoblastoid cell lines (LCLs) and nasopharyngeal carcinoma (NPC) cell lines during the EBV lytic cycle. These suggest that EBV lytic products may be involved in the regulation of stathmin phosphorylation. BGLF4 is an EBV-encoded kinase and has similar kinase activity to cdc2, an important kinase that phosphorylates serine residues 25 and 38 of stathmin during mitosis. Using an siRNA approach, we demonstrated that BGLF4 contributes to the phosphorylation of stathmin in EBV-harboring NPC. Moreover, we confirmed that BGLF4 interacts with and phosphorylates stathmin using an in vitro kinase assay and an in vivo two-dimensional electrophoresis assay. Interestingly, unlike cdc2, BGLF4 was shown to phosphorylate non-proline directed serine residues of stathmin (Ser-16) and it mediated phosphorylation of stathmin predominantly at serines 16, 25, and 38, indicating that BGLF4 can down-regulate the activity of stathmin. Finally, we demonstrated that the pattern of MT organization was changed in BGLF4-expressing cells, possibly through phosphorylation of stathmin. In conclusion, we have shown that a viral Ser/Thr kinase can directly modulate the activity of stathmin and this contributes to alteration of cellular MT dynamics and then may modulate the associated cellular processes.

Post-transplant lymphoproliferative disorders: role of viral infection, genetic lesions and antigen stimulation in the pathogenesis of the disease

Post-transplant lymphoproliferative disorders (PTLD) are a life-threatening complication of solid organ transplantation or, more rarely, hematopoietic stem cell transplantation. The majority of PTLD is of B-cell origin and associated with Epstein–Barr virus (EBV) infection. PTLD generally display involvement of extranodal sites, aggressive histology and aggressive clinical behavior. The molecular pathogenesis of PTLD involves infection by oncogenic viruses, namely EBV, as well as genetic or epigenetic alterations of several cellular genes. At variance with lymphoma arising in immunocompetent hosts, whose genome is relatively stable, a fraction of PTLD are characterized by microsatellite instability as a consequence of defects in the DNA mismatch repair mechanism. Apart from microsatellite instability, molecular alterations of cellular genes recognized in PTLD include alterations of cMYC, BCL6, TP53, DNA hypermethylation, and aberrant somatic hypermutation of protooncogenes. The occurrence of IGV mutations in the overwhelming majority of PTLD documents that malignant transformation targets germinal centre (GC) B-cells and their descendants both in EBV–positive and EBV–negative cases. Analysis of phenotypic markers of B-cell histogenesis, namely BCL6, MUM1 and CD138, allows further distinction of PTLD histogenetic categories. PTLD expressing the BCL6+/MUM1+/-/CD138− profile reflect B-cells actively experiencing the GC reaction, and comprise diffuse large B-cell lymphoma (DLBCL) centroblastic and Burkitt lymphoma. PTLD expressing the BCL6−/MUM1+/CD138− phenotype putatively derive from B-cells that have concluded the GC reaction, and comprise the majority of polymorphic PTLD and a fraction of DLBCL immunoblastic. A third group of PTLD is reminiscent of post-GC and preterminally differentiated B-cells that show the BCL6−/MUM1+/CD138+ phenotype, and are morphologically represented by either polymorphic PTLD or DLBCL immunoblastic.

Burkitt's lymphoma: the Rosetta Stone deciphering Epstein-Barr virus biology

Epstein-Barr virus was originally identified in the tumour cells of a Burkitt's lymphoma, and was the first virus to be associated with the pathogenesis of a human cancer. Studies on the relationship of EBV with Burkitt's lymphoma have revealed important general principles that are relevant to other virus-associated cancers. In addition, the impact of such studies on the knowledge of EBV biology has been enormous. Here, we review some of the key historical observations arising from studies on Burkitt's lymphoma that have informed our understanding of EBV, and we summarise the current hypotheses regarding the role of EBV in the pathogenesis of Burkitt's lymphoma.

Transcriptional downregulation of p27KIP1 through regulation of E2F function during LMP1-mediated transformation

LMP1 induces the phenotypic transformation of fibroblasts and affects regulators of the cell cycle during this process. LMP1 decreases expression of the cyclin-dependent kinase inhibitor p27 and increases the levels and phosphorylation of cyclin-dependent kinase 2 and the retinoblastoma protein. In the present study, the effects of LMP1 on cell cycle progression and the mechanism of p27 downregulation by LMP1 were determined. Although p27 is frequently regulated at the posttranscriptional level during cell cycle progression and in cancer, LMP1 did not decrease ectopically expressed p27. However, LMP1 did decrease p27 RNA levels and inhibited the activity of p27 promoter reporters. The LMP1-regulated promoter element was mapped to a region containing two E2F sites. Electrophoretic mobility shift assays determined that the regulated cis element bound an inhibitory E2F complex containing E2F4 and p130. These findings indicate that LMP1 decreases p27 transcription through effects on E2F family transcription factors. This property likely contributes to the ability of LMP1 to stimulate cell cycle progression.

Quantitative analysis of Epstein-Barr virus (EBV)-related gene expression in patients with chronic active EBV infection

Chronic active Epstein-Barr virus (CAEBV) infection is a systemic Epstein-Barr virus (EBV)-positive lymphoproliferative disorder characterized by persistent or recurrent infectious mononucleosis-like symptoms in patients with no known immunodeficiency. The detailed pathogenesis of the disease is unknown and no standard treatment regimen has been developed. EBV gene expression was analysed in peripheral blood samples collected from 24 patients with CAEBV infection. The expression levels of six latent and two lytic EBV genes were quantified by real-time RT-PCR. EBV-encoded small RNA 1 and BamHI-A rightward transcripts were abundantly detected in all patients, and latent membrane protein (LMP) 2 was observed in most patients. EBV nuclear antigen (EBNA) 1 and LMP1 were detected less frequently and were expressed at lower levels. EBNA2 and the two lytic genes were not detected in any of the patients. The pattern of latent gene expression was determined to be latency type II. EBNA1 was detected more frequently and at higher levels in the clinically active patients. Quantifying EBV gene expression is useful in clarifying the pathogenesis of CAEBV infection and may provide information regarding a patient's disease prognosis, as well as possible therapeutic interventions.

Expression of EBV latent antigens, mammalian target of rapamycin, and tumor suppression genes in EBV-positive smooth muscle tumors: clinical and therapeutic implications

PURPOSE

EBV-positive smooth muscle tumor (EBV+SMT) is a rare disease with no established therapy. We describe the largest single institution analysis in renal transplant recipients. It aims to define its clinical features and determine the expression of EBV latent genes as well as key molecular pathways.

EXPERIMENTAL DESIGN

Patients with EBV+SMT were identified from the Singapore General Hospital Renal Transplant Registry database. These tumors were investigated for expression of EBV latent genes with Southern blots, EBV latent antigens, mammalian target of rapamycin (mTOR), Akt, p70 S6 kinase, and vascular endothelial growth factor using immunohistochemistry, as well as methylation status of cancer-related genes using methylation-specific PCR.

RESULTS

Eight were found to be EBV+SMT in 1,123 transplant patients. All displayed indolent clinical courses and were unresponsive to immunosuppression reduction. Complete tumor regression was seen in one patient following administration of sirolimus. These tumors display the full range of known EBV latent genes. Immunohistochemistry with total and phosphorylated mTOR and Akt were positive for all patients, and vascular endothelial growth factor was positive in 25% of patients, suggesting activation of the mTOR/Akt pathway. Methylation of RASSF1A was found in all tissue samples, whereas promoter hypermethylation of RARbeta, GSTP1, DAPK, and p14 was observed in some samples.

CONCLUSIONS

Our results suggest that these tumors display a EBV type III latency pattern. The mTOR pathway is also activated. EBV may play a role in silencing RASSF1A. EBV-specific immunotherapy, mTOR inhibitors, and demethylating agents are possible therapeutic options in this disease.

Clinical values of multiple Epstein-Barr virus (EBV) serological biomarkers detected by xMAP technology

Background

Serological examination of Epstein-Barr virus (EBV) antibodies has been performed for screening nasopharyngeal carcinoma (NPC) and other EBV-associated diseases.

Methods

By using xMAP technology, we examined immunoglobulin (Ig) A antibodies against Epstein-Barr virus (EBV) VCA-gp125, p18 and IgA/IgG against EA-D, EBNA1 and gp78 in populations with distinct diseases, or with different genetic or geographic background. Sera from Cantonese NPC patients (n = 547) and healthy controls (n = 542), 90 members of high-risk NPC families and 52 non-endemic healthy individuals were tested. Thirty-five of NPC patients were recruited to observe the kinetics of EBV antibody levels during and after treatment. Patients with other EBV-associated diseases were collected, including 16 with infectious mononucleosis, 28 with nasal NK/T cell lymphoma and 14 with Hodgkin's disease.

Results

Both the sensitivity and specificity of each marker for NPC diagnosis ranged 61–84%, but if combined, they could reach to 84.5% and 92.4%, respectively. Almost half of NPC patients displayed decreased EBV immunoactivities shortly after therapy and tumor recurrence was accompanied with high EBV antibody reactivates. Neither the unaffected members from high-risk NPC families nor non-endemic healthy population showed statistically different EBV antibody levels compared with endemic controls. Moreover, elevated levels of specific antibodies were observed in other EBV-associated diseases, but all were lower than those in NPC.

Conclusion

Combined EBV serological biomarkers could improve the diagnostic values for NPC. Diverse EBV serological spectrums presented in populations with different EBV-associated diseases, but NPC patients have the highest EBV activity.

Kaposi sarcoma-associated herpesvirus (KSHV): molecular biology and oncogenesis

Kaposi sarcoma-associated herpesvirus (KSHV) is a double-stranded DNA herpesvirus belonging to the gamma-herpesvirinae subfamily. KSHV has been associated with the development of three neoplastic diseases: Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman disease (MCD). In this review, we discuss the three KSHV-associated malignancies, KSHV genome, latent and lytic aspects of the viral lifecycle, putative viral oncogenes, as well as therapeutic regimens used for the treatment of KS, PEL, and MCD.