Epstein-Barr Virus Latent Gene Expression in Primary Effusion Lymphomas Containing Kaposi's Sarcoma–Associated Herpesvirus/Human Herpesvirus-8

HIV-associated cancers and lymphoproliferative disorders caused by Kaposi sarcoma herpesvirus and Epstein-Barr virus

SUMMARYWithin weeks of the first report of acquired immunodeficiency syndrome (AIDS) in 1981, it was observed that these patients often had Kaposi sarcoma (KS), a hitherto rarely seen skin tumor in the USA. It soon became apparent that AIDS was also associated with an increased incidence of high-grade lymphomas caused by Epstein-Barr virus (EBV). The association of AIDS with KS remained a mystery for more than a decade until Kaposi sarcoma-associated herpesvirus (KSHV) was discovered and found to be the cause of KS. KSHV was subsequently found to cause several other diseases associated with AIDS and human immunodeficiency virus (HIV) infection. People living with HIV/AIDS continue to have an increased incidence of certain cancers, and many of these cancers are caused by EBV and/or KSHV. In this review, we discuss the epidemiology, virology, pathogenesis, clinical manifestations, and treatment of cancers caused by EBV and KSHV in persons living with HIV.

Combined Flow-Fluorescence in situ hybridization to HHV-8 and EBV reveals the viral heterogeneity of primary effusion lymphoma

Primary effusion lymphoma (PEL) is a rare B-cell non-Hodgkin lymphoma associated with Kaposi Sarcoma-associated herpesvirus (KSHV/HHV8) infection. Lymphoma cells are coinfected with Epstein-Barr virus (EBV) in 60-80% of cases. Tools allowing a reliable PEL diagnosis are lacking. This study reports PEL diagnosis in 4 patients using a Flow-Fluorescence in situ hybridization (FlowFISH) technique that allowed detection of differentially expressed EBV and HHV8 transcripts within the same sample, revealing viral heterogeneity of the disease. Moreover, infected cells exhibited variable expressions of CD19, CD38, CD40, and CD138. Therefore, FlowFISH is a promising tool to diagnose and characterize complex viral lymphoproliferations.

Primary human herpesvirus 8-negative effusion-based lymphoma: a large B-cell lymphoma with favorable prognosis

Primary effusion-based lymphoma (EBL) presents as a malignant effusion in a body cavity. The clinicopathologic features and prognosis of primary human herpesvirus 8 (HHV8)-negative EBL remain unclear. We therefore conducted a retrospective study of 95 patients with EBL, regardless of HHV8 status, in Japan. Of 69 patients with EBL tested for HHV8, a total of 64 were negative. The median age of patients with primary HHV8-negative EBL at diagnosis was 77 years (range, 57-98 years); all 58 tested patients were negative for HIV. Primary HHV8-negative EBL was most commonly diagnosed in pleural effusion (77%). Expression of at least 1 pan B-cell antigen (CD19, CD20, or CD79a) was observed in all cases. According to the Hans algorithm, 30 of the 38 evaluated patients had nongerminal center B-cell (non-GCB) tumors. Epstein-Barr virus-encoded small RNA was positive in 6 of 45 patients. In 56 of 64 HHV8-negative patients, systemic therapy was initiated within 3 months after diagnosis. Cyclophosphamide, doxorubicin, vincristine, and prednisolone (CHOP) or CHOP-like regimens with or without rituximab (n = 48) were the most common primary treatments. The overall response and complete response rates were 95% and 73%, respectively. Three patients did not progress without systemic treatment for a median of 24 months. With a median 25-month follow-up, the 2-year overall survival and progression-free survival rates were 84.7% and 73.8%. Sixteen patients died; 12 were lymphoma-related deaths. Thus, most EBL cases in Japan are HHV8-negative and affect elderly patients. The non-GCB subtype is predominant. Overall, primary HHV8-negative EBL exhibits a favorable prognosis after anthracycline-based chemotherapy.

The role of EBV in haematolymphoid proliferations: emerging concepts relevant to diagnosis and treatment

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus with >90% of the adult population worldwide harbouring latent infection. A small subset of those infected develop EBV-associated neoplasms, including a range of lymphoproliferative disorders (LPD). The diagnostic distinction of these entities appears increasingly relevant as our understanding of EBV-host interactions and mechanisms of EBV-driven lymphomagenesis improves. EBV may lower the mutational threshold for malignant transformation, create potential vulnerabilities related to viral alteration of cell metabolism and allow for improved immune targeting. However, these tumours may escape immune surveillance by affecting their immune microenvironment, limiting viral gene expression or potential loss of the viral episome. Methods to manipulate the latency state of the virus to enhance immunogenicity are emerging as well as the potential to detect so-called 'hit and run' cases where EBV has been lost. Finally, measurement of EBV DNA remains an important biomarker for screening and monitoring of LPD. Methods to distinguish EBV DNA derived from virions during lytic activation from latent, methylated EBV DNA present in EBV-associated neoplasms may broaden the utility of this testing, particularly in patients with compromised immune function. We highlight some of these emerging areas relevant to the diagnosis and treatment of EBV-associated LPD with potential applicability to other EBV-associated neoplasms.

Kaposi Sarcoma With Intravascular Primary Effusion Lymphoma in the Skin: A Potential Pitfall in HHV8 Immunohistochemistry Interpretation

Primary effusion lymphoma is a rare, clinically aggressive large B-cell neoplasm universally associated with human herpesvirus 8 that occurs in the setting of immune compromise. It is classically described as a lymphomatous effusion occurring within body cavities. Recently, however, solid tumor masses, and rarely an intravascular form, have been described. We report a case of a cutaneous intravascular primary effusion lymphoma occurring within ectatic vascular spaces of a Kaposi sarcoma skin lesion in a human immunodeficiency virus-positive adult. Human herpesvirus 8 immunohistochemistry was positive in the nuclei of the Kaposi sarcoma spindled cells as well as within large intravascular plasmacytoid cells. This unusual case highlights the importance of careful assessment of the nature of human herpesvirus 8-positive staining cells in an otherwise typical Kaposi sarcoma. A careful search for dual pathology in immune-compromised patients as well as the importance of histologic assessment of skin lesions in human immunodeficiency virus-positive patients is also highlighted.

KSHV/HHV8-positive large B-cell lymphomas and associated diseases: a heterogeneous group of lymphoproliferative processes with significant clinicopathological overlap

In this review, we focus on the current understanding of the diagnosis of human herpesvirus 8 (HHV8)-associated lymphoproliferative disorders-a group of entities that range from hyperplastic proliferations to frank lymphomas. These diseases tend to occur in immunodeficient patients, but may occur in immunocompetent individuals as well. In recent years, we have learned of occasional cases with overlapping features among HHV8 entities, such as lesions intermediate between primary effusion lymphoma and HHV8-positive diffuse large B-cell lymphoma, not otherwise specified or cases sharing features of multicentric Castleman disease and germinotropic lymphoproliferative disorder. There is also a significant clinical overlap between these entities. It is important to have a better understanding of the biology of these lesions and to refine diagnostic criteria of these lesions, as the use of immunosuppressive agents to treat a variety of diseases, the expanded use of transplant as a therapeutic modality for a variety of cancers and organ failure patients, and the extended longevity of HIV-positive patients will likely result in an increased incidence of these lymphoproliferative processes in the future.

Kaposi sarcoma-associated herpesvirus/human herpesvirus 8-associated lymphoproliferative disorders

Kaposi sarcoma-associated herpesvirus/human herpesvirus 8 is associated with multicentric Castleman disease (MCD) and primary effusion lymphoma (PEL). In MCD, infected B cells, although polyclonal, express a monotypic immunoglobulin Mλ phenotype, probably through editing toward λ light chain in mature B cells. They are considered to originate from pre-germinal center (GC) naive B cells. Both viral and human interleukin-6 contribute to the plasmacytic differentiation of these cells, and viral replication can be observed in some infected cells. PEL cells are clonal B cells considered as GC/post-GC B cells. One can also hypothesize that they originate from the same infected naive B cells and that additional factors could be responsible for their peculiar phenotype.

Simultaneous Detection of Beta and Gamma Human Herpesviruses by Multiplex qPCR Reveals Simple Infection and Coinfection Episodes Increasing Risk for Graft Rejection in Solid Organ Transplantation

Herpesviruses are common components of the human microbiome that become clinically relevant when a competent immunosurveillance is compromised, such as in transplantation. Members of the beta and gamma subfamilies are associated with a wide diversity of pathologies, including end-organ disease and cancer. In this study, we developed a multiplex qPCR technique with high specificity, sensitivity, efficiency and predictability that allowed the simultaneous detection and quantification of beta and gamma human herpesviruses. The technique was tested in a cohort of 34 kidney- or liver-transplanted pediatric patients followed up for up to 12 months post-transplant. Viral load was determined in 495 leukocyte-plasma paired samples collected bi-weekly or monthly. Human herpesvirus (HHV) 7 was the herpesvirus most frequently found in positive samples (39%), followed by Epstein-Barr virus (EBV) (20%). Also, EBV and HHV7 were present in the majority of coinfection episodes (62%). The share of positive samples exclusively detected either in leukocytes or plasma was 85%, suggesting that these herpesviruses tended to take a latent or lytic path in an exclusive manner. Infection by human cytomegalovirus (HCMV) and HHV6, as well as coinfection by EBV/HHV7 and EBV/HHV6/HHV7, were associated with graft rejection (RR = 40.33 (p = 0.0013), 5.60 (p = 0.03), 5.60 (p = 0.03) and 17.64 (p = 0.0003), respectively). The routine monitoring of beta and gamma herpesviruses should be mandatory in transplant centers to implement preventive strategies.

Pathological Features of Kaposi's Sarcoma-Associated Herpesvirus Infection

Kaposi's sarcoma-associated herpesvirus (KSHV, human herpesvirus 8, or HHV-8) was firstly discovered in Kaposi's sarcoma tissue derived from patients with acquired immune deficiency syndrome. KSHV infection is associated with malignancies and certain inflammatory conditions. In addition to Kaposi's sarcoma, KSHV has been detected in primary effusion lymphoma, KSHV-associated lymphoma, and some cases of multicentric Castleman disease (MCD). Recently, KSHV inflammatory cytokine syndrome (KICS) was also defined as a KSHV-associated disease. In KSHV-associated malignancies, such as Kaposi's sarcoma and lymphoma, KSHV latently infects almost all tumor cells, and lytic proteins are rarely expressed. A high titer of KSHV is detected in the sera of patients with MCD and KICS, and the expression of lytic proteins such as ORF50, vIL-6, and vMIP-I and vMIP-II is frequently observed in the lesions of patients with these diseases. Immunohistochemistry of LANA-1 is an important diagnostic tool for KSHV infection. However, much of the pathogenesis of KSHV remains to be elucidated, especially regarding oncogenesis. Some viral proteins have been shown to have transforming activity in mammalian cells; however, these proteins are not expressed in latently KSHV-infected cells. KSHV encodes homologs of cellular proteins in its genome such as cyclin D, G-protein coupled protein, interleukin-6, and macrophage inflammatory protein-1 and -2. Molecular mimicry by these viral proteins may contribute to the establishment of microenvironments suitable for tumor growth. In this review, the virus pathogenesis is discussed based on pathological and experimental findings and clinical aspects.

Biology and management of primary effusion lymphoma

Primary effusion lymphoma (PEL) is a rare B-cell malignancy that most often occurs in immunocompromised patients, such as HIV-infected individuals and patients receiving organ transplantation. The main characteristic of PEL is neoplastic effusions in body cavities without detectable tumor masses. The onset of the disease is associated with latent infection of human herpes virus 8/Kaposi sarcoma–associated herpes virus, and the normal counterpart of tumor cells is B cells with plasmablastic differentiation. A condition of immunodeficiency and a usual absence of CD20 expression lead to the expectation of the lack of efficacy of anti-CD20 monoclonal antibody; clinical outcomes of the disease remain extremely poor, with an overall survival at 1 year of ∼30%. Although recent progress in antiretroviral therapy has improved outcomes of HIV-infected patients, its benefit is still limited in patients with PEL. Furthermore, the usual high expression of programmed death ligand 1 in tumor cells, one of the most important immune-checkpoint molecules, results in the immune escape of tumor cells from the host immune defense, which could be the underlying mechanism of poor treatment efficacy. Molecular-targeted therapies for the activating pathways in PEL, including NF-κB, JAK/STAT, and phosphatidylinositol 3-kinase/AKT, have emerged to treat this intractable disease. A combination of immunological recovery from immune deficiency, overcoming the immune escape, and the development of more effective drugs will be vital for improving the outcomes of PEL patients in the future.

Multi-targeted therapy of everolimus in Kaposi's sarcoma associated herpes virus infected primary effusion lymphoma

Kaposi's sarcoma associated herpes virus (KSHV) infected primary effusion lymphoma (PEL) is a rare aggressive form of non-Hodgkin's lymphoma of B cells. KSHV latent and lytic antigens modulate several host cellular signalling pathways especially mammalian target of rapamycin (mTOR), STAT-3 and nuclear factor-kappa B (NF-κB) for rapid tumor progression and immune evasion. Current chemotherapeutic strategies are becoming ineffective as they kill only dividing cells and inefficient to target molecular pathways crucial for active virus replication and its survival. In this study, we evaluated the efficacy of everolimus, an mTOR inhibitor in inducing apoptosis of PEL cells. Dose-dependent treatment of everolimus triggered mitochondria-mediated caspase-dependent apoptosis in PEL cells. Everolimus downregulated KSHV latent antigen expression with concurrent blocking of lytic reactivation for active virus replication. Everolimus also inhibited latent antigen mediated constitutively active STAT-3 and NF-κB signalling. We co-cultured everolimus treated PEL cells with immature dendritic cells and found activation of dendritic cells with increase in surface expression of CD86 and HLA-DR. As everolimus targets and disrupts KSHV antigens as well as antigen facilitated multiple signalling pathways necessary for KSHV survival and maintenance of infection with synchronised boosting of immune system against viral infection, it can be a better therapeutic approach towards treatment of PEL.

Persistent KSHV Infection Increases EBV-Associated Tumor Formation In Vivo via Enhanced EBV Lytic Gene Expression

The human tumor viruses Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) establish persistent infections in B cells. KSHV is linked to primary effusion lymphoma (PEL), and 90% of PELs also contain EBV. Studies on persistent KSHV infection in vivo and the role of EBV co-infection in PEL development have been hampered by the absence of small animal models. We developed mice reconstituted with human immune system components as a model for KSHV infection and find that EBV/KSHV dual infection enhanced KSHV persistence and tumorigenesis. Dual-infected cells displayed a plasma cell-like gene expression pattern similar to PELs. KSHV persisted in EBV-transformed B cells and was associated with lytic EBV gene expression, resulting in increased tumor formation. Evidence of elevated lytic EBV replication was also found in EBV/KSHV dually infected lymphoproliferative disorders in humans. Our data suggest that KSHV augments EBV-associated tumorigenesis via stimulation of lytic EBV replication.

Metagenomic deep sequencing of aqueous fluid detects intraocular lymphomas

Introduction

Currently, the detection of pathogens or mutations associated with intraocular lymphomas heavily relies on prespecified, directed PCRs. With metagenomic deep sequencing (MDS), an unbiased high-throughput sequencing approach, all pathogens as well as all mutations present in the host’s genome can be detected in the same small amount of ocular fluid.

Methods

In this cross-sectional case series, aqueous fluid samples from two patients were submitted to MDS to identify pathogens as well as common and rare cancer mutations.

Results

MDS of aqueous fluid from the first patient with vitreal lymphoma revealed the presence of both Epstein-Barr virus (HHV-4/EBV) and human herpes virus 8 (HHV-8) RNA. Aqueous fluid from the second patient with intraocular B-cell lymphoma demonstrated a less common mutation in the MYD88 gene associated with B-cell lymphoma.

Conclusion

MDS detects pathogens that, in some instances, may drive the development of intraocular lymphomas. Moreover, MDS is able to identify both common and rare mutations associated with lymphomas.

Epigenetic manipulation of host chromatin by Kaposi sarcoma-associated herpesvirus: a tumor-promoting factor?

Molecular and epidemiological evidence links Kaposi sarcoma-associated herpesvirus (KSHV) to a number of malignancies of endothelial or B cell origin. As for most virus-associated cancers, however, the tumor initiating and promoting events remain poorly understood. Given the emerging role of epigenetic alterations as drivers of human cancers, an interesting (and as of yet under-explored) hypothesis is that viral manipulation of host cell chromatin may contribute to the pathogenesis of KSHV-associated tumors. We here review the current knowledge regarding the interplay between KSHV-encoded factors and host chromatin and discuss how epigenetic alterations may contribute to the pathogenesis of KSHV-associated tumors.

Multiple viral infections in primary effusion lymphoma: a model of viral cooperation in lymphomagenesis

INTRODUCTION

Primary effusion lymphoma (PEL) is a rare B-cell lymphoid neoplasm mainly associated with HIV infection, presenting as pleural, peritoneal, and pericardial effusions. A defining property of PEL is its consistent association with Kaposi sarcoma associated herpesvirus (KSHV) infection, and, in most cases, Epstein Barr virus (EBV) co-infection. On these grounds, a review of the literature related to viral cooperation and lymphomagenesis can help to understand the complex interplay between KSHV and EBV in PEL pathogenesis. Areas covered: In this review, the authors highlight clinical, pathologic, genetic and proteomic features of PEL, in the context of viral cooperation in PEL lymphomagenesis. Expert commentary: Tumour cells are characterized by the overexpression of genes that are involved in inflammation and invasion. Coherently, PEL secretomes are enriched in proteins probably responsible for the particular tropism (cell adhesion and migration) of PEL cells. The development of PEL in HIV+ patients is multifactorial and involves a complex interplay among co-infection with oncogenic viruses (EBV and KSHV), inflammatory factors, and environmental conditions.

Primary lymphocyte infection models for KSHV and its putative tumorigenesis mechanisms in B cell lymphomas

Kaposi's sarcoma-associated herpesvirus (KSHV) is the latest addition to the human herpesvirus family. Unlike alpha- and beta-herpesvirus subfamily members, gamma-herpesviruses, including Epstein-Barr virus (EBV) and KSHV, cause various tumors in humans. KSHV primarily infects endothelial and B cells in vivo, and is associated with at least three malignancies: Kaposi's sarcoma and two B cell lymphomas, respectively. Although KSHV readily infects endothelial cells in vitro and thus its pathogenic mechanisms have been extensively studied, B cells had been refractory to KSHV infection. As such, functions of KSHV genes have mostly been elucidated in endothelial cells in the context of viral infection but not in B cells. Whether KSHV oncogenes, defined in endothelial cells, play the same roles in the tumorigenesis of B cells remains an open question. Only recently, through a few ground-breaking studies, B cell infection models have been established. In this review, those models will be compared and contrasted and putative mechanisms of KSHV-induced B cell transformation will be discussed.

An Unusual Case of Invasive Kaposi's Sarcoma with Primary Effusion Lymphoma in an HIV Positive Patient: Case Report and Literature Review

We report a case of AIDS-related Kaposi's sarcoma (KS) with Primary Effusion Lymphoma (PEL) in a 28-year-old, African American male. Kaposi's sarcoma is an AIDS defining disease and typically will disseminate early in the course of the disease affecting the skin, mucous membranes, gastrointestinal tract, lymph nodes, and lungs. This case reports an unusual presentation of the disease along with primary effusion lymphoma. Although the most common organ systems affected by KS are the respiratory and the gastrointestinal systems, the lungs of this patient did not show any evidence of KS. Additionally, the patient demonstrates the rarely seen liver and unique pancreatic involvement by KS along with unusual synchronous bilateral pleural and peritoneal cavity involvement by PEL, adding to the distinct pattern of invasive AIDS-related Kaposi's sarcoma.

Human Exportin-1 is a Target for Combined Therapy of HIV and AIDS Related Lymphoma

Infection with HIV ultimately leads to advanced immunodeficiency resulting in an increased incidence of cancer. For example primary effusion lymphoma (PEL) is an aggressive non-Hodgkin lymphoma with very poor prognosis that typically affects HIV infected individuals in advanced stages of immunodeficiency. Here we report on the dual anti-HIV and anti-PEL effect of targeting a single process common in both diseases. Inhibition of the exportin-1 (XPO1) mediated nuclear transport by clinical stage orally bioavailable small molecule inhibitors (SINE) prevented the nuclear export of the late intron-containing HIV RNA species and consequently potently suppressed viral replication. In contrast, in CRISPR-Cas9 genome edited cells expressing mutant C528S XPO1, viral replication was unaffected upon treatment, clearly demonstrating the anti-XPO1 mechanism of action. At the same time, SINE caused the nuclear accumulation of p53 tumor suppressor protein as well as inhibition of NF-κB activity in PEL cells resulting in cell cycle arrest and effective apoptosis induction. In vivo, oral administration arrested PEL tumor growth in engrafted mice. Our findings provide strong rationale for inhibiting XPO1 as an innovative strategy for the combined anti-retroviral and anti-neoplastic treatment of HIV and PEL and offer perspectives for the treatment of other AIDS-associated cancers and potentially other virus-related malignancies.

How do viruses trick B cells into becoming lymphomas?

PURPOSE OF REVIEW

Since the discovery of Epstein-Barr virus in Burkitt's lymphoma 50  years ago, only one other virus, namely Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8, has been confirmed to be a direct cause of B-cell lymphoma. Here we will review the evidence for Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus as causal lymphoma agents.

RECENT FINDINGS

A deeper understanding of specific mechanisms by which Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus cause B-cell lymphomas has been acquired over the past years, in particular with respect to viral protein interactions with host cell pathways, and microRNA functions. Specific therapies based on knowledge of viral functions are beginning to be evaluated, mostly in preclinical models.

SUMMARY

Understanding the causal associations of specific infectious agents with certain B-cell lymphomas has allowed more accurate diagnosis and classification. A deeper knowledge of the specific mechanisms of transformation is essential to begin assessing whether virus-targeted treatment modalities may be used in the future.

EBV-driven B-cell lymphoproliferative disorders: from biology, classification and differential diagnosis to clinical management

Epstein–Barr virus (EBV) is a ubiquitous herpesvirus, affecting >90% of the adult population. EBV targets B-lymphocytes and achieves latent infection in a circular episomal form. Different latency patterns are recognized based on latent gene expression pattern. Latent membrane protein-1 (LMP-1) mimics CD40 and, when self-aggregated, provides a proliferation signal via activating the nuclear factor-kappa B, Janus kinase/signal transducer and activator of transcription, phosphoinositide 3-kinase/Akt (PI3K/Akt) and mitogen-activated protein kinase pathways to promote cellular proliferation. LMP-1 also induces BCL-2 to escape from apoptosis and gives a signal for cell cycle progression by enhancing cyclin-dependent kinase 2 and phosphorylation of retinoblastoma (Rb) protein and by inhibiting p16 and p27. LMP-2A blocks the surface immunoglobulin-mediated lytic cycle reactivation. It also activates the Ras/PI3K/Akt pathway and induces Bcl-xL expression to promote B-cell survival. Recent studies have shown that ebv-microRNAs can provide extra signals for cellular proliferation, cell cycle progression and anti-apoptosis. EBV is well known for association with various types of B-lymphocyte, T-lymphocyte, epithelial cell and mesenchymal cell neoplasms. B-cell lymphoproliferative disorders encompass a broad spectrum of diseases, from benign to malignant. Here we review our current understanding of EBV-induced lymphomagenesis and focus on biology, diagnosis and management of EBV-associated B-cell lymphoproliferative disorders.

Influence of ND10 components on epigenetic determinants of early KSHV latency establishment

We have previously demonstrated that acquisition of intricate patterns of activating (H3K4me3, H3K9/K14ac) and repressive (H3K27me3) histone modifications is a hallmark of KSHV latency establishment. The precise molecular mechanisms that shape the latent histone modification landscape, however, remain unknown. Promyelocytic leukemia nuclear bodies (PML-NB), also called nuclear domain 10 (ND10), have emerged as mediators of innate immune responses that can limit viral gene expression via chromatin based mechanisms. Consequently, although ND10 functions thus far have been almost exclusively investigated in models of productive herpesvirus infection, it has been proposed that they also may contribute to the establishment of viral latency. Here, we report the first systematic study of the role of ND10 during KSHV latency establishment, and link alterations in the subcellular distribution of ND10 components to a temporal analysis of histone modification acquisition and host cell gene expression during the early infection phase. Our study demonstrates that KSHV infection results in a transient interferon response that leads to induction of the ND10 components PML and Sp100, but that repression by ND10 bodies is unlikely to contribute to KSHV latency establishment. Instead, we uncover an unexpected role for soluble Sp100 protein, which is efficiently and permanently relocalized from nucleoplasmic and chromatin-associated fractions into the insoluble matrix. We show that LANA expression is sufficient to induce Sp100 relocalization, likely via mediating SUMOylation of Sp100. Furthermore, we demonstrate that depletion of soluble Sp100 occurs precisely when repressive H3K27me3 marks first accumulate on viral genomes, and that knock-down of Sp100 (but not PML or Daxx) facilitates H3K27me3 acquisition. Collectively, our data support a model in which non-ND10 resident Sp100 acts as a negative regulator of polycomb repressive complex-2 (PRC2) recruitment, and suggest that KSHV may actively escape ND10 silencing mechanisms to promote establishment of latent chromatin.

Human herpesvirus 8-unrelated primary effusion lymphoma-like lymphoma: report of a rare case and review of 54 cases in the literature

OBJECTIVES

To report a patient with primary effusion lymphoma who was negative for human herpesvirus-8 (HHV-8), human immunodeficiency virus, Epstein-Barr virus, hepatitis C virus, and hepatitis B virus, as well as review 54 reported cases of HHV-8-unrelated primary effusion lymphoma (PEL)-like lymphoma in the literature to clarify the nature of this entity.

METHODS

The patients' characteristics, clinical presentation, pathogenesis, morphologic-immunophenotypic features, clinical management, and prognosis were studied.

RESULTS

HHV-8-negative PEL-like lymphomas often occur in immunocompetent and elderly patients, are sometimes associated with chronic inflammation-related fluid overload, are mostly large B-cell or large B-cell with plasmacytic differentiation type, and are associated with a better prognosis.

CONCLUSIONS

In various aspects, HHV-8-unrelated PEL-like lymphoma is a different entity from HHV-8-related PEL. Immunophenotype, morphology, and c-myc/8q24 status should be included for differential diagnosis. A test for c-myc or 8q24 abnormalities should be recommended for subdividing HHV-8-unrelated PEL-like lymphoma, which may have benefits in patient management.

Strong cross-talk between angiogenesis and EBV: do we need different treatment approaches in lymphoma cases with EBV and/or high angiogenic capacity

Angiogenesis is the new blood vessels formation and is the critical event for the growth of malignant diseases and plays a key role in the development, invasion, and metastasis of malignant tumors. Epstein-Barr virus (EBV) is an important carcinogen causing to the some neoplastic disorders and lytically infected cells may contribute to the growth of EBV-associated malignancies, and this phenomenon is related with enhancing angiogenesis. Due to the strong cross-talk between angiogenesis and viral carcinogenesis and increased information about the angiogenesis and viral carcinogenesis in lymphomas, we need new therapeutic approaches to cases with lymphoma. Due to the strong cross-talk between angiogenesis and viral lymphomagenesis, this association was reviewed in this study.

Phosphatase and tensin homolog on chromosome 10 is phosphorylated in primary effusion lymphoma and Kaposi's sarcoma

Primary effusion lymphoma (PEL) is a non-Hodgkin's B-cell lymphoma driven by Kaposi's sarcoma-associated herpesvirus. It is uniquely sensitive to mTOR, PI3K, and Akt inhibitors; however, the basis of this requirement for the mTOR pathway remains to be elucidated. The phosphatase and tensin homolog gene (PTEN) on chromosome 10 controls the first step in the phosphatidylinositol 3 kinase (PI3K)-Akt-mammalian target of rapamycin (mTOR) pathway and is genetically inactivated in many solid tumors. We find an absence of PTEN deletions, mutations, or protein mislocalization in PEL. However, we find consistent hyperphosphorylation at serine 380 of PTEN, which is an inactivating modification, in PEL cell lines and in tumor xenografts. We also evaluated a large tissue microarray of Kaposi's sarcoma biopsies and observed concordant high levels of phospho-PTEN, phospho-Akt, and phospho-S6 ribosomal protein. Reintroduction of PTEN into PEL inhibited colony formation in soft agar, verifying the functional dependence of PEL on PI3K signaling. This was also true for PEL cell lines that carried mutant p53 and for KS-like cell lines. Activating PTEN in these cancers may yield a new treatment strategy for PEL, KS, and similar PTEN wild-type lymphomas.

Gammaherpesvirus and lymphoproliferative disorders in immunocompromised patients

Two lymphotropic human gamma herpesviruses can cause lymphoproliferative disorders: Epstein Barr virus (EBV, formally designated as human herpesvirus 4) and Kaposi sarcoma herpesvirus (KSHV, also called human herpesvirus 8). Individuals with inherited or acquired immunodeficiency have a greatly increased risk of developing a malignancy caused by one of these two viruses. Specific types of lymphoproliferations, including malignant lymphomas, occur in individuals with HIV infection, transplant recipients and children with primary immunodeficiency. Some of these diseases, such as Hodgkin's and non-Hodgkin lymphoma resemble those occurring in immunocompetent patients, but the proportion of tumors in which EBV is present is increased. Others, like primary effusion lymphoma and polymorphic post-transplant lymphoproliferative disorder are rarely seen outside the context of a specific immunodeficient state. Understanding the specific viral associations in selected lymphoproliferative disorders, and the insights into the molecular mechanisms of viral oncogenesis, will lead to better treatments for these frequently devastating diseases.

Infectious agents in human cancers: lessons in immunity and immunomodulation from gammaherpesviruses EBV and KSHV

Members of the herpesvirus family have evolved the ability to persist in their hosts by establishing a reservoir of latently infected cells each carrying the viral genome with reduced levels of viral protein synthesis. In order to spread within and between hosts, in some cells, the quiescent virus will reactivate and enter lytic cycle replication to generate and release new infectious virus particles. To allow the efficient generation of progeny viruses, all herpesviruses have evolved a wide variety of immunomodulatory mechanisms to limit the exposure of cells undergoing lytic cycle replication to the immune system. Here we have focused on the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) that, uniquely among the eight human herpesviruses identified to date, have growth transforming potential. Most people infected with these viruses will not develop cancer, viral growth-transforming activity being kept under control by the host's antigen-specific immune responses. Nonetheless, EBV and KSHV are associated with several malignancies in which various viral proteins, either predominantly or exclusively latency-associated, are expressed; at least some of these proteins also have immunomodulatory activities. Of these malignancies, some are the result of a disrupted virus/immune balance through genetic, infectious or iatrogenic immune suppression. Others develop in people that are not overtly immune suppressed and likely modulate the immunological response. This latter aspect of immune modulation by EBV and KSHV forms the basis of this review.

Insights into the evolution of lymphomas induced by Epstein-Barr virus

Epstein-Barr virus (EBV) encodes a wealth of oncogenic instructions, including the abilities to drive a resting normal B cell to proliferate and to override apoptotic stimuli. EBV is found in almost all types of lymphomas at varying frequencies. However, the particular viral genes expressed differ considerably among tumors. We have examined the role of EBV in several lymphomas by conditionally evicting the extrachromosomal viral genome from tumor cells in vitro and have found a graded dependence on the virus. Tumor cells that express all the known latent viral genes have been found to depend on the virus to drive proliferation and to block apoptosis at least in part by repressing the proapoptotic protein Bim. Other tumor cells, which express fewer viral genes, also depend on the virus to block apoptosis, but rely on the virus to promote but not to drive proliferation. Lastly, tumor cells with the fewest viral genes expressed have been found to require EBV to prevent the inefficient induction of a Bim-independent apoptosis. We present a model for the evolution of EBV-induced lymphomas in which tumors are initially "addicted" to the virus for almost all oncogenic functions. These tumors are targets for the immune system because they express multiple immunogenic viral proteins. Therefore, EBV-induced tumors are under selective pressure to acquire cellular mutations that can replace viral functions. We posit that the heterogeneity in viral gene expression among different EBV-associated lymphomas reflects a dynamic process by which tumors evolve to be less dependent on the virus.

A human herpesvirus miRNA attenuates interferon signaling and contributes to maintenance of viral latency by targeting IKKε

Type I interferon (IFN) signaling is the principal response mediating antiviral innate immunity. IFN transcription is dependent upon the activation of transcription factors IRF3/IRF7 and NF-κB. Many viral proteins have been shown as being capable of interfering with IFN signaling to facilitate evasion from the host innate immune response. Here, we report that a viral miRNA, miR-K12-11, encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) is critical for the modulation of IFN signaling and acts through targeting I-kappa-B kinase epsilon (IKKɛ). Ectopic expression of miR-K12-11 resulted in decreased IKKɛ expression, while inhibition of miR-K12-11 was found to restore IKKɛ expression in KSHV-infected cells. Importantly, expression of miR-K12-11 attenuated IFN signaling by decreasing IKKɛ-mediated IRF3/IRF7 phosphorylation and by inhibiting the activation of IKKɛ-dependent IFN stimulating genes (ISGs), allowing miR-K12-11 suppression of antiviral immunity. Our data suggest that IKKɛ targeting by miR-K12-11 is an important strategy utilized by KSHV to modulate IFN signaling during the KSHV lifecycle, especially in latency. We also demonstrated that IKKɛ was able to enhance KSHV reactivation synergistically with the treatment of 12-O-tetradecanoylphorbol 13-acetate. Moreover, inhibition of miR-K12-11 enhanced KSHV reactivation induced by vesicular stomatitis virus infection. Taken together, our findings also suggest that miR-K12-11 can contribute to maintenance of KSHV latency by targeting IKKɛ.

Herpesvirus-Associated B-cell Proliferations

This article reviews the spectrum of Epstein-Barr virus and Kaposi sarcoma herpesvirus (KSHV/HHV-8)-associated B-cell lymphoid proliferations, their pathologic features and clinical presentation, diagnostic criteria, and pathogenetic aspects. Emphasis is on the differential diagnosis issues and difficulties that the pathologist may face for the correct identification and interpretation of these lesions.

Primary effusion lymphoma: genomic profiling revealed amplification of SELPLG and CORO1C encoding for proteins important for cell migration

Primary effusion lymphoma (PEL) is associated with Kaposi sarcoma herpesvirus (KSHV) but its pathogenesis is poorly understood. Many KSHV-associated products can deregulate cellular pathways commonly targeted in cancer. However, KSHV infection alone is insufficient for malignant transformation. PEL also lacks the chromosomal translocations seen in other lymphoma subtypes. We investigated 28 PELs and ten PEL cell lines by 1 Mb resolution array comparative genomic hybridization (CGH) and found frequent gains of 1q21-41 (47%), 4q28.3-35 (29%), 7q (58%), 8q (63%), 11 (32%), 12 (61%), 17q (29%), 19p (34%), and 20q (34%), and losses of 4q (32%), 11q25 (29%), and 14q32 (63%). Recurrent focal amplification was seen at several regions on chromosomes 7, 8, and 12. High-resolution chromosome-specific tile-path array CGH confirmed these findings, and identified selectin-P ligand (SELPLG) and coronin-1C (CORO1C) as the targets of a cryptic amplification at 12q24.11. Interphase FISH and quantitative PCR showed SELPLG/CORO1C amplification (>4 extra copies) and low levels of copy number gain (1-4 extra copies) in 23% of PELs, respectively. Immunohistochemistry revealed strong expression of both SELPLG and coronin-1C in the majority of PELs, irrespective of their gene dosage. SELPLG is critical for cell migration and chemotaxis, while CORO1C regulates actin-dependent processes, thus important for cell motility. Their overexpression in PEL is expected to play an important role in its pathogenesis.

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.

Castleman's disease--a two compartment model of HHV8 infection

Castleman's disease is a primary infectious disease of the lymph node that causes local symptoms or a systemic inflammatory syndrome. Histopathology reveals a destroyed lymph node architecture that can range from hyaline-vascular disease to plasma-cell disease. Viral interleukin 6 (vIL-6) produced during the replication of human herpesvirus type 8 (HHV8) is the key driver of systemic inflammation and cellular proliferation. Stage progression of Castleman's disease results from switches between viral latency and lytic replication, and lymphatic and hematogenous spread. Multicentric plasma-cell disease in HIV-1 patients is associated with HHV8 infection. Polyclonal plasmablast proliferation escapes control in the germinal center with eventual malignant transformation into non-Hodgkin lymphoma. Surgery produces excellent results in unicentric disease, while multicentric disease responds to anti-CD20 therapy or IL-6 and chemotherapy. Lymphovascular endothelium and naive B cells are infectious reservoir-opening options for antiangiogenic and anti-CD19 strategies to enhance outcomes in patients with systemic disease.

Epstein-Barr virus encoded LMP1 downregulates TCL1 oncogene through miR-29b

Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is noted for its transforming potential. Yet, it also acts as a cytostatic and growth-relenting factor in Burkitt's lymphoma (BL) cells. The underlying molecular mechanisms of the growth inhibitory property of LMP1 have remained largely unknown. In this study, we show that LMP1 negatively regulates a major oncogene, TCL1, in diffuse large B-cell lymphoma (DLBCL) and BL cells. MicroRNA (miR) profiling of LMP1 transfectants showed that among others, miR-29b, is upregulated. LMP1 diminished TCL1 by inducing miR-29b through C-terminus activation region 1 (CTAR1) and CTAR2. miR-29b locked nucleic acid (LNA) antisense oligonucleotide transfection into LMP1-expressing cells reduced miR-29b expression and consequently reconstituted TCL1, suggesting that LMP1 negatively regulates TCL1 through miR-29b upregulation. The miR-29b increase by LMP1 was due to an increase in the cluster pri-miR-29b1-a transcription, derived from human chromosome 7. Using pharmacological inhibitors, we found that p38 mitogen-activated protein kinase-activating function of LMP1 is important for this effect. The ability of LMP1 to negatively regulate TCL1 through miR-29b might underlie its B-cell lymphoma growth antagonistic property. As LMP1 is also important for B-cell transformation, we suggest that the functional dichotomy of this viral protein may depend on a combination of levels of its expression, lineage and differentiation of the target cells and regulation of miRs, which then directs the outcome of the cellular response.

Prognostic significance of EBV-LMP1 and VEGF-A expressions in non-Hodgkin's lymphomas

BACKGROUND AND AIM

EBV is an important virus in the pathogenesis of NHL. VEGF-A is the essential factor in tumor angiogenesis. There is evidence of cross talk between angiogenesis and viral carcinogenesis. The viral latent protein LMP1, may play a role by inducing expression of angiogenic factors In this study EBV-LMP1 and VEGF-A expressions have been studied in cases with NHL and prognostic significance of these has been evaluated.

PATIENTS AND METHODS

One hundred seventy-seven cases (60 had low grade lymphoma (LGL), 117 had aggressive lymphoma (AL)) with NHL have been included in this analysis. Immunohistochemistry has been used for the detection of EBV and VEGF-A.

RESULTS

EBV was found in 25 cases (14%); 5 of 60 cases with LGL while 20 of 117 cases with AL had EBV positivity; (OR: 2.3, 95% CI: 0.8-6.3, p=0.113). VEGF-A expression was found in 108 cases (61%); 30 of 60 cases with LGL and 78 of 117 cases with AL showed VEGF-A expression. There was an association between VEGF-A and aggressive histology (OR: 2.0, 95% CI: 1.1-3.8, p=0.031). EBV positivity was associated with VEGF-A expression in diffuse large B cell lymphoma (DLBCL) (0.045). Mean Survival rates were shorter in EBV (+) and/or VEGF-A (+) cases.

COMMENT

Highly significant association between VEGF-A and EBV expression and survival rate, suggests an association between angiogenesis and viral lymphomagenesis. Targeting both the angiogenesis and EBV may be important in the therapy of cases with NHL expressing EBV and/or VEGF-A.

Primary effusion lymphoma

Primary effusion lymphoma (PEL) is a rare HIV-associated non-Hodgkin's lymphoma (NHL) that accounts for approximately 4% of all HIV-associated NHL. PEL has a unique clinical presentation in having a predilection for arising in body cavities such as the pleural space, pericardium, and peritoneum. PEL cells are morphologically variable with a null lymphocyte immunophenotype and evidence of human herpesvirus (HHV)-8 infection. The exact oncogenic mechanisms of HHV-8 have not been clearly defined. Treatment is usually with combination CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy and antiretroviral therapy (if HIV positive). The prognosis for PEL is poor, with a median survival time of around 6 months. As the exact molecular steps in HHV-8-driven oncogenesis are unraveled, it is hoped that more specific therapeutic targets will be revealed.

Deregulation of c-Myc in primary effusion lymphoma by Kaposi's sarcoma herpesvirus latency-associated nuclear antigen

Primary effusion lymphoma (PEL) is a rare subtype of non-Hodgkin's lymphoma, which is associated with infection by Kaposi's sarcoma herpesvirus (KSHV)/human herpesvirus-8. The c-Myc transcription factor plays an important role in cellular proliferation, differentiation and apoptosis. Lymphomas frequently have deregulated c-Myc expression owing to chromosomal translocations, amplifications or abnormal stabilization. However, no structural abnormalities were found in the c-myc oncogene in PEL. Given that c-Myc is often involved in lymphomagenesis, we hypothesized that it is deregulated in PEL. We report that PEL cells have abnormally stable c-Myc protein. The turnover of c-Myc protein is stringently regulated by post-transcriptional modifications, including phosphorylation of c-Myc threonine 58 (T58) by glycogen synthase kinase-3beta (GSK-3beta). Our data show that the impaired c-Myc degradation in PEL cells is associated with a significant underphosphorylation of c-Myc T58. The KSHV latency-associated nuclear antigen (LANA) is responsible for this deregulation. Overexpression of LANA in human embryonic kidney 293 or peripheral blood B cells leads to post-transcriptional deregulation of c-Myc protein. Conversely, when LANA is eliminated from PEL cells using RNA interference, GSK-3beta-mediated c-Myc T58 phosphorylation is restored. The presence of c-Myc and LANA in GSK-3beta-containing complexes in PEL cells further confirms the significance of these interactions in naturally KSHV-infected cells.

A case of HHV-8-associated HIV-negative primary effusion lymphoma in Moscow

Primary effusion lymphoma is a rare tumor of B-cell derivation which is associated with human herpes virus type 8 (HHV-8) in 100% and with human immunodeficiency virus (HIV) in most of cases. The paper describes the first case in Russia of HIV(-) HHV-8(+) Epstein-Barr virus (EBV)(+) primary effusion lymphoma in a male patient aged 56 years. The tumor was located in the pleural cavity. Interestingly, the patient was HIV-negative while having a positive tumor HHV-8 test. There are only 22 similar cases described worldwide.

AIDS malignancies

Among individuals with HIV-infection, coinfection with oncogenic viruses including EBV, HHV-8, and HPV cause significant cancer-related morbidity and mortality. It is clear that these viruses interact with HIV in unique ways that predispose HIV-infected individuals to malignant diseases. In general, treatment directed specifically against these viruses does not appear to change the natural history of the malignant disease, and once the malignancy develops, if their health permits, HIV-infected patients should be treated using similar treatment protocols to HIV-negative patients. However, for the less frequent HIV-related malignancies, such as PEL, or MCD, optimal treatments are still emerging. For certain AIDS-defining malignancies, it is clear that the widespread access to HAART has significantly decreased the incidence, and improved outcomes. However, for other cancers, such as the HPV-related tumors, the role of HAART is much less clear. Further research into prevention and treatment of these oncogenic virally mediated AIDS-related malignancies is necessary.

Potential role of natural killer cells in controlling growth and infiltration of AIDS-associated primary effusion lymphoma cells

Natural killer (NK) cells are an important component of the innate immune response against microbial infections and tumors. Direct involvement of NK cells in tumor growth and infiltration has not yet been demonstrated clearly. Primary effusion lymphoma (PEL) cells were able to produce tumors and ascites very efficiently with infiltration of cells in various organs of T-, B- and NK-cell knock-out NOD/SCID/gammac(null) (NOG) mice within 3 weeks. In contrast, PEL cells formed small tumors at inoculated sites in T- and B-cell knock-out NOD/SCID mice with NK-cells while completely failing to infiltrate into various organs. Immunosupression of NOD/SCID by treatment with an antimurine TM-beta1 antibody, which transiently abrogates NK cell activity in vivo, resulted in enhanced tumorigenicity and organ infiltration in comparison with non-treated NOD/SCID mice. Activated human NK cells inhibited tumor growth and infiltration in NOG mice. Our results suggest that NK cells play an important role in growth and infiltration of PEL cells, and activated NK cells could be a promising immunotherapeutic tool against tumor or virus-infected cells either alone or in combination with conventional therapy. The rapid and efficient engraftment of PEL cells in NOG mice also suggests that this new animal model could provide a unique opportunity to understand and investigate the mechanism of pathogenesis and malignant cell growth.

Kaposi sarcoma-associated herpesvirus and other viruses in human lymphomagenesis

Kaposi sarcoma-associated herpesvirus (KSHV), also called human herpesvirus 8 (HHV-8), is associated with a specific subset of lymphoproliferative disorders. These include two main categories. The first is primary effusion lymphomas and related solid variants. The second is multicentric Castleman disease, from which KSHV-positive plasmablastic lymphomas can arise. KSHV contributes to lymphomagenesis by subverting the host cell molecular signaling machinery to deregulate cell growth and survival. KSHV expresses a selected set of genes in the lymphoma cells, encoding viral proteins that play important roles in KSHV lymphomagenesis. Deregulation of the NF-kappaB pathway is an important strategy used by KSHV to promote lymphoma cell survival, and the viral protein vFLIP is essential for this process. Two other viruses that are well documented to be causally associated with lymphoid neoplasia in humans are Epstein-Barr virus (EBV/HHV-4) and human T-cell lymphotropic virus (HTLV-1). Both of these are similar to KSHV in their use of viral proteins to promote cell survival by deregulating the NF-kappaB pathway. Here we review the basic information and recent developments that have contributed to our knowledge of lymphomas caused by KSHV and other viruses. The understanding of the mechanisms of viral lymphomagenesis should lead to the identification of novel therapeutic targets and to the development of rationally designed therapies.