The role of Epstein-Barr virus in lymphoid malignancies

Oncogenes and RNA splicing of human tumor viruses

Approximately 10.8% of human cancers are associated with infection by an oncogenic virus. These viruses include human papillomavirus (HPV), Epstein–Barr virus (EBV), Merkel cell polyomavirus (MCV), human T-cell leukemia virus 1 (HTLV-1), Kaposi's sarcoma-associated herpesvirus (KSHV), hepatitis C virus (HCV) and hepatitis B virus (HBV). These oncogenic viruses, with the exception of HCV, require the host RNA splicing machinery in order to exercise their oncogenic activities, a strategy that allows the viruses to efficiently export and stabilize viral RNA and to produce spliced RNA isoforms from a bicistronic or polycistronic RNA transcript for efficient protein translation. Infection with a tumor virus affects the expression of host genes, including host RNA splicing factors, which play a key role in regulating viral RNA splicing of oncogene transcripts. A current prospective focus is to explore how alternative RNA splicing and the expression of viral oncogenes take place in a cell- or tissue-specific manner in virus-induced human carcinogenesis.

The enhanced expression of the matrix metalloproteinase 9 in nasal NK/T-cell lymphoma

Background

Nasal NK/T cell lymphoma is an aggressive disease and has a poor prognosis. Nasal NK/T cell lymphoma is refractory to conventional chemotherapy and has strong tendency of widespread relapse or dissemination into distant sites.

Methods

We immunohistochemically studied nasal NK/T-cell lymphoma to elucidate the unique characteristics of nasal NK/T-cell lymphoma, such as its higher metastatic tendency and its vast necrosis which leads to destruction of the involved tissues. The expression of P-glycoprotein and MMP-9 was evaluated in the 20 patients with nasal NK/T-cell lymphoma and 25 with nasal non-NK/T-cell lymphoma and the relationship between expression of these proteins and clinical results were analyzed in this report.

Results

Overall 5-year survival rates for patients with nasal NK/T cell lymphoma, and nasal non-NK/T cell lymphoma were 51%, and 84%. Distant involvement free 5-year survival rates for patients with nasal NK/T cell lymphoma, and nasal non-NK/T cell lymphoma were 53%, and 79%.

Overall positivity for P-glycoprotein was observed in 10 of 19 patients with NTL and in 13 of 23 patients with non-NTL. When the overall survival rate was compared between patients with P-glycoprotein positive and negative, there was no difference between them.

Sixteen of the 19 patients with nasal NK/T cell lymphoma expressed MMP-9. In contrast, only 8 of the 22 patients with nasal non-NK/T cell lymphoma expressed MMP-9. Distant involvement free 5-year survival rates for patients with MMP-9 negative, and MMP-9 positive were 92%, and 61%, respectively. The difference was statistically significant (p = 0.027).

Conclusion

Positive immunoreactivity for P-glycoprotein was not an independent prognostic factor in nasal NK/T-cell lymphomas, which stresses the importance of exploring other mechanisms of drug resistance. The strong expression of MMP-9 is uniquely characteristic of nasal NK/T cell lymphoma and may contribute to its strong tendency to disseminatate and the extensive necrosis which is always seen. However, our results are based on univariate comparisons, and as such, should be viewed with some caution.

Severe Epstein–Barr virus-associated hemophagocytic syndrome in six adult patients

BACKGROUND

EBV associated hemophagocytic syndrome (HPS) is an aggressive and potentially life-threatening condition. So far, most EBV associated HPS has been characterized mainly in infants and children in Asian countries.

RESULTS

Here, we report six cases of EBV associated HPS occurring in previously healthy adults in a non-endemic area within a short period of 3 years. All patients presented with fever, hepatosplenomegaly and pancytopenia as well as disturbed liver function tests and coagulopathy. Half were diagnosed as having lymphoma. While EBV-specific serological assays were non-diagnostic in four of the six patients, the presence of EBV DNA in plasma allowed the diagnosis of EBV associated HPS in all patients.

CONCLUSION

EBV associated HPS may be more prevalent in non-Japanese adults than was previously considered. Screening for hemophagocytic syndrome, in adults as well as in children, should include real-time PCR for EBV.

Pathogenesis and mechanism of disease progression from hemophagocytic lymphohistiocytosis to Epstein-Barr virus-associated T-cell lymphoma: nuclear factor-kappa B pathway as a potential therapeutic target

Epstein-Barr virus (EBV) can infect T lymphocytes and manifests as hemophagocytic lymphohistiocytosis (HLH), a distinct entity of hemophagocytic syndrome (HPS) characterized by fever, hepatosplenomegaly, cytopenia, hypercytokinemia, and systemic macrophage activation with hemophagocytosis. In a substantial percentage of HLH patients, the disease may relapse or progress to T-cell lymphoma in months to years. In the present review, the authors summarize the previous studies on the pathogenesis of HLH and the potential mechanism for the progression of disease from HLH to T-cell lymphoma. The infection of T cells by EBV could activate T cells to secrete proinflammatory cytokines, particularly tumor necrosis factor-alpha (TNF-alpha), which subsequently activate macrophages. EBV latent membrane protein-1 (LMP-1) is the viral product responsible for the activation of the TNF receptor (TNFR) associated factors/nuclear factor-kappaB (NF-kappaB)/ERK pathway to enhance cytokine secretion mediated through the suppression of the SAP/SH2D1A gene. The activation of NF-kappaB will confer resistance to TNF-alpha-induced apoptosis on EBV-infected T cells through the down-regulation of TNFR-1. Consistent with in vitro observations, EBV-associated T or natural killer/T-cell lymphoma showed constitutive activation of NF-kappaB, explaining its drug resistance, hypercytokinemia, and poor prognosis. Therefore, similar to other inflammation-associated cancers, HLH provides a unique model to study the mechanism of disease progression from a benign virus-infected disorder (HLH) to T-cell lymphoma. Inhibition of the NF-kappaB signal pathway should provide a potential target for the treatment of HLH and EBV-associated T-cell lymphoma.

Cellular responses to viral infection in humans: lessons from Epstein-Barr virus

Epstein-Barr virus (EBV) provides a useful model to study cellular immunity to a genetically stable, persistent human virus. Different sets of proteins expressed during EBV's lytic and cell transforming infections induce qualitatively different cellular immune responses. The factors governing immunodominance hierarchies and the biological effectiveness of these different responses are now being revealed. Analysis of infectious mononucleosis (IM), a clinical syndrome that can arise during primary EBV infection, has allowed the evolution of the responses to be tracked over time, giving an understanding of the immune response kinetics and of those determinants affecting selection into memory. Furthermore, following IM, expression of the receptor for the homeostatic cytokine IL-15 on NK and T cells is lost within these individuals. This experiment of nature provides a system to advance understanding of immunological homeostasis in humans, illustrating how data obtained from the study of EBV have wider significance to the immunological community.

Epstein-Barr virus LMP1 inhibits the expression of SAP gene and upregulates Th1 cytokines in the pathogenesis of hemophagocytic syndrome

The primary infection of Epstein-Barr virus (EBV) may result in fatal infectious mononucleosis or hemophagocytic syndrome (HPS) in 2 diseases; that is, X-linked lymphoproliferative disorder (XLP) and hemophagocytic lymphohistiocytosis (HLH). XLP is linked to mutations of the SAP/SH2D1A gene with dysregulated T-cell activation in response to EBV infection. Patients with sporadic HLH, however, usually have no mutation of the SAP/SH2D1A gene, and EBV latent membrane protein-1 (LMP1) can up-regulate Th1 cytokines in EBV-infected T cells. Since both diseases share common manifestations of HPS, it is important to clarify whether a cross-talk exists between signaling lymphocyte activation molecule (SLAM)-associated protein (SAP) and LMP1-mediated pathways to explain the common pathogenesis of HPS. In this study, no mutation of the SAP/SH2D1A gene at exon 2/3 was detected in 7 HLH cases. Interestingly, EBV LMP1 could transcriptionally inhibit the expression of SAP/SH2D1A and activate downstream molecules ERK and interferon-gamma (IFN-gamma). LMP1-mediated SAP/ERK/IFN-gamma signals appear to act via the TNF receptor-associated factor (TRAF)2,5/nuclear factor kappaB (NF-kappaB) pathway, since dominant-negative TRAF2/5 and NF-kappaB inhibitor could rescue SAP expression and downregulate IFN-gamma. Although HLH is genetically distinct from XLP, our data suggest that both diseases share a common signal pathway, through either the mutation or LMP1-mediated suppression of the SAP gene, leading to overt T-cell activation and enhanced Th1 cytokine secretion in response to EBV infection.

Lack of evidence for a role of Epstein-Barr virus in the increase of lung cancer in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is known as an independent risk factor for lung cancer. Because Epstein-Barr virus (EBV) may be involved in the genesis of IPF as well as certain malignancies, we investigated whether EBV contributes to the increased incidence of lung cancer in IPF The formalin-fixed and paraffin-embedded lung sections were prepared from 22 lung cancer patients with IPF and 22 lung cancer patients without IPF All ofthe IPF patients pathologically showed usual interstitial pneumonia. In situ hybridization for EBV-encoded small non-polyadenylated RNAs failed to show positive signals in the cancer tissues of either IPF or non-IPF patients. This study did not provide evidence for an etiologic role of EBV in the development of lung cancer in IPF.

Epstein-barr virus latent membrane protein-1 mediates upregulation of tumor necrosis factor-alpha in EBV-infected T cells: implications for the pathogenesis of hemophagocytic syndrome

The infection of human T cells by Epstein-Barr virus (EBV) may result in a fatal hemophagocytic syndrome (HS). We have previously shown that EBV can selectively upregulate the tumor necrosis factor-alpha (TNFalpha) gene and lead to activation of macrophages in a manner similar to the pathobiology of HS in EBV-infected T lymphoproliferative disorders (LPDs). This study was designed to further clarify the specific EBV gene product(s) responsible for TNFalpha upregulation. RT-PCR analysis of EBV gene expression was performed on 2 CR2-transfected EBV-infected T lymphoma lines and 2 EBV-infected B cell lines. To identify the EBV gene responsible for upregulation of TNFalpha, 2 reporter recombinant plasmids, pTNF-CAT and pTNFalpha-Luc, were then constructed and cotransfected with the expression plasmids of the EBV latent and lytic genes (EBNA-1, EBNA-2, LMP-1, LMP-2A, and BZLF-1) in both T and B cell lines. Analyses using ELISA and Western blotting were further performed to detect the secreted TNFalpha. The results revealed that EBNA-1 and LMP-1 were consistently expressed in EBV-infected T cell lines (type II latency), while a type III latency with expression of EBNA-1, EBNA-2, LMP-1, and lytic BZLF transcripts was detected in EBV-infected B cell lines. LMP-1 was demonstrated to be the only EBV gene product to transactivate the TNFalpha gene, and this phenomenon was observed only in T, not in B, cells. Enhanced secretion of TNF-alpha protein was also detected in LMP1-transfected T cell lines. We concluded that LMP1 is the candidate protein in the upregulation of the TNFalpha gene in T cells and is probably responsible for the pathogenesis of HS in EBV-infected T lymphoproliferative disorders.

Molecular analysis of latent membrane protein 1 in patients with Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis in Japan

Latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) is considered to be an oncoprotein because it is crucial for B-lymphocyte transformation. Since a 30 base pair (bp) deletion in the carboxy-terminal portion of the LMP1 gene was found in a CAO cell line derived from nasopharyngeal carcinoma containing EBV, an association between EB viral genetic alteration and tumorigenicity has been postulated. In this study we have analyzed LMP1 DNA isolated from 10 Japanese patients with EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH). In all HLH patients, we found the 30 bp deletion and 4-8-tandem repeats of the sequence DNGPQDPDNTD in the LMP1 gene. Furthermore, detailed amino acid (aa) sequence analysis revealed that 7 aa substitutions identical to those found in CAO-LMP1 but not in B95.8 cell line-LMP1 were found in all the HLH cases. NF-kappaB assay revealed that HLH-LMP1 activated NF-kappaB significantly more than that of B95.8-LMP1 (p=0.032). We conclude that EBV from all of our HLH cases shared common genetic characteristics with EBV obtained from the CAO cell line, which is distinct from the wild-type EBV isolated from the B95.8 cell line. These data suggest that the mutational changes of the LMP1 gene may play an important role in the pathogenesis of these fatal EBV-related disorders.

Molecular piracy: the viral link to carcinogenesis

The vast majority of the human experience with viral infections is associated with acute symptoms, such as malaise, fever, chills, rhinitis and diarrhea. With this acute or lytic phase, the immune system mounts a response and eliminates the viral agent while acquiring antibodies to that specific viral subtype. With latent or chronic infections, the viral agent becomes incorporated into the human genome. Viral agents capable of integration into the host's genetic material are particularly dangerous and may commandeer the host's ability to regulate normal cell growth and proliferation. The oncogenic viruses may immortalize the host cell, and facilitate malignant transformation. Cell growth and proliferation may be enhanced by viral interference with tumor suppressor gene function (p53 and pRb). Viruses may act as vectors for mutated proto-oncogenes (oncogenes). Overexpression of these oncogenes in viral-infected cells interferes with normal cell function and allows unregulated cell growth and proliferation, which may lead to malignant transformation and tumour formation. Development of oral neoplasms, both benign and malignant, has been linked to several viruses. Epstein-Barr virus is associated with oral hairy leukoplakia, lymphoproliferative disease, lymphoepithelial carcinoma, B-cell lymphomas, and nasopharyngeal carcinoma. Human herpesvirus-8 has been implicated in all forms of Kaposi's sarcoma, primary effusion lymphomas, multiple myeloma, angioimmunoblastic lymphadenopathy, and Castleman's disease. Human herpesvirus-6 has been detected in lymphoproliferative disease, lymphomas, Hodgkin's disease, and oral squamous cell carcinoma. The role of human papillomavirus in benign (squamous papilloma, focal epithelial hyperplasia, condyloma acuminatum, verruca vulgaris), premalignant (oral epithelial dysplasia), and malignant (squamous cell carcinoma) neoplasms within the oral cavity is well recognized. Herpes simplex virus may participate as a cofactor in oral squamous cell carcinoma development by enhancing activation, amplification, and overexpression of pre-existing oncogenes within neoplastic tissues. Because of the integral role of viruses in malignant transformation of host cells, innovative antiviral therapy may prevent tumour development, involute neoplastic proliferations, or arrest malignant progression.

[Hodgkin's disease in patients infected with the human immunodeficiency virus]

INTRODUCTION

Hodgkin's disease in patients infected by the human immunodeficiency virus (HIV) is still not part of the definition of acquired immune deficiency syndrome. Nonetheless, this entity has a particular presentation when compared to the disease occurring in immune-competent patients.

CURRENT KNOWLEDGE AND KEY POINTS

Increased frequency (> 75%) of advanced anatomical stages and extranodular localizations (Ann Arbor system stages III and IV) has been outlined in HIV-infected patients. Mediastinal involvement is more unusual in immunocompromised than in immune-competent patients. The presence of B symptoms (fever, weight loss, nocturnal sweats) is very frequent. Finally, the predominance of mixed cellularity (type 3) characterizes Hodgkin's disease in immunocompromised patients. Due to either the immunodeficiency, antiretroviral treatments, poor hematological tolerance in response to chemotherapy, or to advanced anatomical stages, disease management may be hampered. Current therapeutical approaches often obtain complete remission; however, some deaths are still related to the disease progression to acquired immune deficiency syndrome.

FUTURE PROSPECTS AND PROJECTS

From these observations, Hodgkin's disease management in HIV-infected patients relies on therapeutical approaches similar to those used for non infected patients, with some specific recommendations. Chemotherapy should be conducted in the shortest time in order to minimize chemotherapy-induced immunosuppression. Simultaneous use of antiretroviral treatment and reinforced opportunistic infection prophylaxis are of pivotal importance. Finally, the use of hematopoietic growth factors appears to be safe regarding viral replication, but still requires further evaluation.

The complexity of the Epstein-Barr virus infection in humans

The Epstein-Barr virus (EBV) was isolated 40 years ago from cultures of Burkitt lymphoma cells (BL). The tumor was encountered in Africa and exhibited characteristical geographical, clinical and pathological features. Serological studies revealed that the virus is ubiquitous in humans. The primary infection is often accompanied by the syndrome of acute infectious mononucleosis (IM). It can induce malignant proliferation of B lymphocytes in conditions of immunodeficiency. EBV can immortalize B lymphocytes in culture. These cells carry the virus as episomes and express 9 virally encoded proteins. Their immunological recognition constitutes the surveillance which is responsible for the healthy virus carrier state. The main virus reservoir is represented by a low number of resting B lymphocyte which contain the viral genome but do not express its transformation proteins. The viral genome is detectable in all African BLs, in variable proportions of nasopharyngeal carcinoma, Hodgkin's disease, T cell lymphoma, lymphoepithelial like carcinoma, gastric carcinoma and leiomyosarcoma cases. The role of EBV in the genesis of these tumors is unknown.