Heterogeneous Epstein-Barr virus latent gene expression in AIDS-associated lymphomas and in type I Burkitt's lymphoma cell lines

Latent Membrane Proteins from EBV Differentially Target Cellular Pathways to Accelerate MYC-induced Lymphomagenesis

EBV LMP1 enhances MYC-mediated degradation of the p27kip1 tumor suppressor and accelerates MYC-induced lymphomagenesis.

EBV LMP1 and LMP2A differentially use G1-specific cell cycle and BCR-mediated signaling to accelerate MYC-induced lymphomagenesis.

MYC translocations in association with Epstein-Barr virus (EBV) infection are often observed in B-cell lymphomas. A subset of Burkitt lymphoma (BL) expresses EBV latent membrane proteins 1 and 2A (LMP1 and LMP2A) in addition to the typical restricted EBV latent gene expression. EBV-associated diffuse large B-cell lymphoma (DLBCL) typically exhibits latency type II or III and expresses LMP1. Here, we investigate the role of LMP1 in MYC-driven lymphomagenesis in our murine model. λ-MYC mice develop tumors having a “starry sky” appearance and have abnormal p53 expression that is also observed in human BL. LMP2A/λ-MYC double-transgenic mice develop tumors significantly faster than mice only expressing MYC. Similar to LMP2A/λ-MYC mice, LMP1/λ-MYC mice also have accelerated MYC-driven lymphomagenesis. As observed in LMP2A/λ-MYC mice, p27^kip1 was degraded in LMP1/λ-MYC pretumor and tumor B cells. Coexpression of LMP1 and LMP2A resulted in the enhancement of B cell proliferation. In contrast to LMP2A, the inhibition of Syk or cyclin-dependant kinase (CDK)4/6 activity did not effectively inhibit LMP1-mediated MYC lymphomagenesis. Also, in contrast to LMP2A, LMP1 did not lessen abnormal p53 expression in λ-MYC tumors. To investigate the significance of LMP1 expression in human BL development, we reanalyzed RNA sequencing (RNA-Seq) data of primary human BL from previous studies. Interestingly, p53 mutations were less observed in LMP1-expressing BL, although they were not significantly changed by EBV infection, indicating LMP1 may lessen p53 mutations in human primary BL. This suggests that LMP1 effects in EBV-associated human BL vary from what we observe in our murine model. Finally, our studies suggest a novel pathogenic role of LMP1 in lymphomagenesis.

Stress-Induced Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) is typically found in a latent, asymptomatic state in immunocompetent individuals. Perturbations of the host immune system can stimulate viral reactivation. Furthermore, there are a myriad of EBV-associated illnesses including various cancers, post-transplant lymphoproliferative disease, and autoimmune conditions. A thorough understanding of this virus, and the interplay between stress and the immune system, is essential to establish effective treatment. This review will provide a summary of the interaction between both psychological and cellular stressors resulting in EBV reactivation. It will examine mechanisms by which EBV establishes and maintains latency and will conclude with a brief overview of treatments targeting EBV.

The EBNA3 Family: Two Oncoproteins and a Tumour Suppressor that Are Central to the Biology of EBV in B Cells

Epstein-Barr virus nuclear antigens EBNA3A , EBNA3B and EBNA3C are a family of three large latency-associated proteins expressed in B cells induced to proliferate by the virus. Together with the other nuclear antigens (EBNA-LP, EBNA2 and EBNA1), they are expressed from a polycistronic transcription unit that is probably unique to B cells. However, compared with the other EBNAs, hitherto the EBNA3 proteins were relatively neglected and their roles in EBV biology rather poorly understood. In recent years, powerful new technologies have been used to show that these proteins are central to the latency of EBV in B cells, playing major roles in reprogramming the expression of host genes affecting cell proliferation, survival, differentiation and immune surveillance. This indicates that the EBNA3s are critical in EBV persistence in the B cell system and in modulating B cell lymphomagenesis. EBNA3A and EBNA3C are necessary for the efficient proliferation of EBV-infected B cells because they target important tumour suppressor pathways--so operationally they are considered oncoproteins. In contrast, it is emerging that EBNA3B restrains the oncogenic capacity of EBV, so it can be considered a tumour suppressor--to our knowledge the first to be described in a tumour virus. Here, we provide a general overview of the EBNA3 genes and proteins. In particular, we describe recent research that has highlighted the complexity of their functional interactions with each other, with specific sites on the human genome and with the molecular machinery that controls transcription and epigenetic states of diverse host genes.

Diagnosis and management of lymphomas and other cancers in HIV-infected patients

Despite the introduction of highly active antiretroviral therapy or combination antiretroviral therapy (HAART and cART, respectively) patients infected with HIV might develop certain types of cancer more frequently than uninfected people. Lymphomas represent the most frequent malignancy among patients with HIV. Other cancer types that have increased in these patients include Kaposi sarcoma, cancer of the cervix, anus, lung and liver. In the post-HAART era, however, patients with HIV have experienced a significant improvement in their morbidity, mortality and life expectancy. This Review focuses on the different types of lymphomas that generally occur in patients with HIV. The combination of cART and antineoplastic treatment has resulted in remarkable prolongation of disease-free survival and overall survival among patients with HIV who develop lymphoma. However, the survival in these patients still lags behind that of patients with lymphoma who are not infected with HIV. We also provide an update of epidemiological data, diagnostic issues, and strategies regarding the most-appropriate management of patients with both HIV and lymphomas.

Salubrious effects of oxytocin on social stress-induced deficits

Social relationships are a fundamental aspect of life, affecting social, psychological, physiological, and behavioral functions. While positive social interactions can attenuate stress and promote health, the social environment can also be a major source of stress when it includes social disruption, confrontation, isolation, or neglect. Social stress can impair the basal function and stress-induced activation of the hypothalamic-pituitary-adrenal (HPA) axis, impairing function of multiple biological systems and posing a risk to mental and physical health. In contrast, social support can ameliorate stress-induced physiological and immunological deficits, reducing the risk of subsequent psychological distress and improving an individual's overall well-being. For better clinical treatment of these physiological and mental pathologies, it is necessary to understand the regulatory mechanisms of stress-induced pathologies as well as determine the underlying biological mechanisms that regulate social buffering of the stress system. A number of ethologically relevant animal models of social stress and species that form strong adult social bonds have been utilized to study the etiology, treatment, and prevention of stress-related disorders. While undoubtedly a number of biological pathways contribute to the social buffering of the stress response, the convergence of evidence denotes the regulatory effects of oxytocin in facilitating social bond-promoting behaviors and their effect on the stress response. Thus, oxytocin may be perceived as a common regulatory element of the social environment, stress response, and stress-induced risks on mental and physical health. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

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.

Phosphatidylinositol 3-kinase/Akt pathway targets acetylation of Smad3 through Smad3/CREB-binding protein interaction: contribution to transforming growth factor beta1-induced Epstein-Barr virus reactivation

Epstein-Barr virus, a ubiquitous human herpesvirus, is associated with the development of carcinomas and lymphomas. We previously showed that transforming growth factor beta1 (TGF-beta1) mediated the virus to enter the lytic cycle, which is triggered by expression of Z Epstein-Barr virus replication activator (ZEBRA), through the ERK 1/2 MAPK signaling pathway. We report here that Akt, activated downstream from ERK 1/2, was required for TGF-beta1-induced ZEBRA expression and enabled Smad3, a mediator of TGF-beta1 signaling, to be acetylated by direct interaction with the co-activator CREB-binding protein and then to regulate TGF-beta1-induced ZEBRA expression.

Activation of the lytic program of the Epstein-Barr virus in Burkitt's lymphoma cells leads to a two steps downregulation of expression of the proapoptotic protein BimEL, one of which is EBV-late-gene expression dependent

The Epstein-Barr virus (EBV) generally latently infects its target cells with expression of genes conferring resistance to apoptosis. However, the modulation of apoptotic signals during lytic cycle remains poorly understood. We show here that resulting from viral reactivation in the EBV-positive Mutu-I and Akata Burkitt's lymphoma cell lines, a two steps proteasome-dependent downregulation of expression of the proapoptotic protein BimEL occurs. The first drop might be EBV-independent, is ERK 1/2 dependent, and BimEL is phosphorylated on Ser69. A second dramatic drop of the BimEL level observed during the lytic cycle is dependent of EBV-late-gene expression, ERK 1/2 independent, and no further phosphorylation of BimEL on Ser69 occurred. These results demonstrate for the first time, that the lytic cycle contributes to downregulation of BimEL and then could add to protection against apoptosis.

EBV microRNAs in primary lymphomas and targeting of CXCL-11 by ebv-mir-BHRF1-3

EBV-encoded microRNAs (miRNAs) have been identified and their functions are being studied. The expression pattern of these miRNAs in clinical samples of EBV-associated non-Hodgkin's lymphomas is unknown. We analyzed five primary "endemic" pediatric Burkitt's lymphomas (BL), two acquired immunodeficiency syndrome (AIDS)-related type I latency BL lines, a type III latency line, three EBV(+) primary effusion lymphomas (PEL), and three AIDS-related diffuse large B-cell lymphomas (DLBCL) for expression of EBV-encoded miRNAs. A markedly elevated expression of miRNA BHRF1-3 in type III relative to its parental type I BL line was found. Primary unmanipulated type I BLs and EBV(+) PELs expressed high levels of BART2 miRNA, whereas DLBCLs expressed both BART2 and BHRF1-3 species. BHRF1-3 miRNA expression inversely correlated with levels of a putative cellular target, the IFN-inducible T-cell attracting chemokine CXCL-11/I-TAC, and suppression of this factor was reversed by transfection of an antisense oligo to the EBV miRNA BHRF1-3. EBV-encoded miRNAs are expressed in primary lymphomas classically linked to the virus and are associated with the viral latency status. Targeted suppression of CXCL-11/I-TAC by a viral-encoded miRNA may serve as an immunomodulatory mechanism in these tumors.

EBV-encoded dUTPase induces immune dysregulation: Implications for the pathophysiology of EBV-associated disease

Epstein-Barr virus (EBV) encodes for several enzymes that are involved in viral DNA replication. There is evidence that some viral proteins, by themselves, can induce immune dysregulation that may contribute to the pathophysiology of the virus infection. In this study, we focused on the EBV-encoded deoxyuridine triphosphate nucleotidohydrolase (dUTPase) and present the first evidence that the dUTPase is able to induce immune dysregulation in vitro as demonstrated by the inhibition of the replication of stimulated peripheral blood mononuclear cells (PBMCs) and the upregulation of several proinflammatory cytokines including TNF-alpha, IL-1beta, IL-8, IL-6, and IL-10 produced by unstimulated PBMCs treated with purified EBV-encoded dUTPase. Depletion of CD14-positive cells (monocytes) eliminated the cytokine profile induced by EBV dUTPase treatment. The data support the hypothesis that at least one protein of the EBV early antigen complex can induce immune dysregulation and may be involved in the pathophysiology of EBV-associated disease.

Epstein-Barr virus (EBV) genome and expression in breast cancer tissue: effect of EBV infection of breast cancer cells on resistance to paclitaxel (Taxol)

The Epstein-Barr virus (EBV) has been detected in subsets of breast cancers. In order to elaborate on these observations, we quantified by real-time PCR (Q-PCR) the EBV genome in biopsy specimens of breast cancer tissue as well as in tumor cells isolated by microdissection. Our findings show that EBV genomes can be detected by Q-PCR in about half of tumor specimens, usually in low copy numbers. However, we also found that the viral load is highly variable from tumor to tumor. Moreover, EBV genomes are heterogeneously distributed in morphologically identical tumor cells, with some clusters of isolated tumor cells containing relatively high genome numbers while other tumor cells isolated from the same specimen may be negative for EBV DNA. Using reverse transcription-PCR, we detected EBV gene transcripts: EBNA-1 in almost all of the EBV-positive tumors and RNA of the EBV oncoprotein LMP-1 in a smaller subset of the tissues analyzed. Moreover, BARF-1 RNA was detected in half of the cases studied. Furthermore, we observed that in vitro EBV infection of breast carcinoma cells confers resistance to paclitaxel (taxol) and provokes overexpression of a multidrug resistance gene (MDR1). Consequently, even if a small number of breast cancer cells are EBV infected, the impact of EBV infection on the efficiency of anticancer treatment might be of importance.

Ganciclovir is associated with low or undetectable Epstein-Barr virus DNA load in cerebrospinal fluid of patients with HIV-related primary central nervous system lymphoma

BACKGROUND

Epstein-Barr virus (EBV) is pathogenically linked to human immunodeficiency virus (HIV)-related primary central nervous system lymphoma (PCNSL) and is found in virtually all HIV-related PCNSL cases. The objective of this study was to assess the effect of ganciclovir on EBV DNA replication in patients with HIV-related PCNSL.

PATIENTS AND METHODS

EBV DNA was measured by real-time polymerase chain reaction in cerebrospinal fluid and plasma samples from 25 patients with HIV-related PCNSL. Eight of these patients were receiving ganciclovir for concurrent cytomegalovirus infections.

RESULTS

EBV DNA was detected in cerebrospinal fluid samples obtained from 15 (88%) of 17 ganciclovir-untreated patients and 4 (50%) of 8 ganciclovir-treated patients (P = .028). EBV DNA load was significantly lower for treated patients, compared with untreated patients (median value, 2.15 vs. 4.16 log copies/mL; P = .001). Analysis of sequential cerebrospinal fluid samples from 7 patients showed that EBV DNA decreased in samples obtained from 2 patients following the start of ganciclovir administration but did not decrease in samples obtained from the 5 untreated patients. In addition, patients who received ganciclovir survived longer than the untreated patients (median duration of survival, 181 vs. 72 days; P = .006).

CONCLUSION

The effect of ganciclovir on EBV DNA load in cerebrospinal fluid supports the hypothesis that EBV is replicating in patients with PCNSL. This observation, together with the effect of ganciclovir therapy on patient survival, suggests that this drug might be useful for the management of PCNSL.

Azidothymidine inhibits NF-kappaB and induces Epstein-Barr virus gene expression in Burkitt lymphoma

The antiviral compound azidothymidine (AZT), alone or in combination with other agents, induces apoptosis in early-passage, Epstein-Barr virus-positive Burkitt lymphoma (EBV+ BL) lines and has clinical activity in EBV+ BL. We report here a mechanism of AZT's antitumor activity. The nuclei of these cells contain activated nuclear factor-kappaB (NF-kappaB) subunits p50, c-Rel, RelB, and p52, but not p65. Treatment of primary EBV+ BL lines with AZT inhibited NF-kappaB within 1 to 2 hours. This was followed by up-regulation of EBV gene expression including viral thymidine kinase (vTK) and apoptosis. Subclones of EBV+ BL cells that demonstrated activated p65 were resistant to AZT. In EBV+ BLs, AZT but not ganciclovir (GCV) was highly phosphorylated to its monophosphate form (AZT-MP). Phosphorylation, as well as apoptosis, was markedly enhanced in the presence of hydroxyurea. AZT inhibits NF-kappaB and up-regulates EBV gene expression in primary EBV+ BLs. AZT with hydroxyurea may represent an inexpensive, targeted regimen for endemic BL.