Epstein-Barr Virus DNA recombination and loss in sporadic Burkitt's lymphoma

Immune Modulation by Epstein-Barr Virus Lytic Cycle: Relevance and Implication in Oncogenesis

EBV infects more than 90% of people globally, causing lifelong infection. The phases of the EBV life cycle encompass primary infection, latency, and subsequent reactivation or lytic phase. The primary infection usually happens without noticeable symptoms, commonly in early life stages. If it manifests after childhood, it could culminate in infectious mononucleosis. Regarding potential late consequences, EBV is associated with multiple sclerosis, rheumatoid arthritis, chronic active EBV infection, lymphomas, and carcinomas. Previous reports that the lytic phase plays a negligible or merely secondary role in the oncogenesis of EBV-related tumors are steadily losing credibility. The right mechanisms through which the lytic cycle contributes to carcinogenesis are still unclear, but it is now recognized that lytic genes are expressed to some degree in different cancer-type cells, implicating their role here. The lytic infection is a persistent aspect of virus activity, continuously stimulating the immune system. EBV shows different strategies to modulate and avoid the immune system, which is thought to be a key factor in its ability to cause cancer. So, the principal goal of our review is to explore the EBV's lytic phase contribution to oncogenesis.

Worldwide Prevalence of Epstein-Barr Virus in Patients with Burkitt Lymphoma: A Systematic Review and Meta-Analysis

Burkitt lymphoma (BL) is a form of B-cell malignancy that progresses aggressively and is most often seen in children. While Epstein-Barr virus (EBV) is a double-stranded DNA virus that has been linked to a variety of cancers, it can transform B lymphocytes into immortalized cells, as shown in BL. Therefore, the estimated prevalence of EBV in a population may assist in the prediction of whether this population has a high risk of increased BL cases. This systematic review and meta-analysis aimed to estimate the prevalence of Epstein-Barr virus in patients with Burkitt lymphoma. Using the appropriate keywords, four electronic databases were searched. The quality of the included studies was assessed using the Joanna Briggs Institute's critical appraisal tool. The results were reported as percentages with a 95% confidence interval using a random-effects model (CI). PROSPERO was used to register the protocol (CRD42022372293), and 135 studies were included. The prevalence of Epstein-Barr virus in patients with Burkitt lymphoma was 57.5% (95% CI: 51.5 to 63.4, n = 4837). The sensitivity analyses demonstrated consistent results, and 65.2% of studies were of high quality. Egger's test revealed that there was a significant publication bias. EBV was found in a significantly high proportion of BL patients (more than 50% of BL patients). This study recommends EBV testing as an alternative for predictions and the assessment of the clinical disease status of BL.

Epstein-Barr-Virus infection patterns in nodular lymphocyte predominant Hodgkin-lymphoma

AIMS

We investigated 19 cases of Epstein-Barr virus (EBV)-positive nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) as information regarding latency types is currently incomplete.

METHODS & RESULTS

Immunohistochemistry (IHC) for CD20, CD79a, PAX5, OCT2 CD30, CD15, CD3, and PD1 was performed. For EBV-detection, in-situ hybridization (ISH) for EBV-encoded RNAs (EBER) was employed combined with IHC for EBV-encoded latent membrane protein (LMP)-1, -nuclear antigen (EBNA)-2 and -BZLF1. In 95% of the cases, neoplastic cells with features of Hodgkin- and Reed-Sternberg cells (HRS cells) were present, mostly showing expression of CD30. In all cases, the B-cell phenotype was largely intact, and delineation from classical HL (CHL) was further supported by MEF2A detection. All tumor cells were EBER-positive except two cases. EBV-latency type II was most frequent (89%) and type I rare. Cases with latency type I were CD30-negative. Five cases contained some BZLF1 and/or EBNA2-positive bystander lymphocytes.

CONCLUSIONS

As HRS-morphology of neoplastic cells combined with CD30 expression are frequent features of EBV-positive NLPHL, preservation of B-cell-transcription program, MEF2B expression combined with NLPHL-typical architecture and background composition facilitate distinction from CHL. EBER-ISH is the method of choice to identify these cases. The majority present with an EBV latency type II and only rarely with latency type I, which can be associated with missing CD30 expression. The presence of occasional bystander lymphocytes expressing BZLF1 and/or EBNA2 and the partial EBV-infection of neoplastic cells in some cases could indicate that EBV is either not primarily involved or only a transient driver in the pathogenesis of EBV-positive NLPHL.

Pathological and molecular analysis of a composite lymphoma of mantle cell lymphoma and Epstein-Barr virus-positive follicular lymphoma

Composite lymphoma (CL) is a very rare clinical entity defined by the presence of two or more different subtypes of lymphoma in the same lymph node. We report a case of CL in a 78-year-old male presenting with leukocytosis and swelling of multiple lymph nodes. A left axillary node biopsy showed atypical lymphocytes in both the interfollicular and follicular areas. Immunohistochemistry revealed that mantle cell lymphoma (MCL) was mainly present in the interfollicular area and follicular lymphoma (FL) was present in the follicular area. Polymerase chain reaction analysis of immunoglobulin heavy chain gene rearrangements confirmed that they were clonally related neoplasms. However, Epstein-Barr virus (EBV) DNA was detected in only FL cells, suggesting that MCL and FL had split into two clones in the early steps of pathogenesis. This is the first reported case of CL with EBV-negative B-cell non-Hodgkin lymphoma (NHL) and EBV-positive B-cell NHL with a clonal relationship. We discuss the developmental processes of these two lymphomas.

Frequent traces of EBV infection in Hodgkin and non-Hodgkin lymphomas classified as EBV-negative by routine methods: expanding the landscape of EBV-related lymphomas

The Epstein-Barr virus (EBV) is linked to various B-cell lymphomas, including Burkitt lymphoma (BL), classical Hodgkin lymphoma (cHL) and diffuse large B-cell lymphoma (DLBCL) at frequencies ranging, by routine techniques, from 5 to 10% of cases in DLBCL to >95% in endemic BL. Using higher-sensitivity methods, we recently detected EBV traces in a few EBV-negative BL cases, possibly suggesting a "hit-and-run" mechanism. Here, we used routine and higher-sensitivity methods (qPCR and ddPCR for conserved EBV genomic regions and miRNAs on microdissected tumor cells; EBNA1 mRNA In situ detection by RNAscope) to assess EBV infection in a larger lymphoma cohort [19 BL, 34 DLBCL, 44 cHL, 50 follicular lymphomas (FL), 10 T-lymphoblastic lymphomas (T-LL), 20 hairy cell leukemias (HCL), 10 mantle cell lymphomas (MCL)], as well as in several lymphoma cell lines (9 cHL and 6 BL). qPCR, ddPCR, and RNAscope consistently documented the presence of multiple EBV nucleic acids in rare tumor cells of several cases EBV-negative by conventional methods that all belonged to lymphoma entities clearly related to EBV (BL, 6/9 cases; cHL, 16/32 cases; DLBCL, 11/30 cases), in contrast to fewer cases (3/47 cases) of FL (where the role of EBV is more elusive) and no cases (0/40) of control lymphomas unrelated to EBV (HCL, T-LL, MCL). Similarly, we revealed traces of EBV infection in 4/5 BL and 6/7 HL cell lines otherwise conventionally classified as EBV negative. Interestingly, additional EBV-positive cases (1 DLBCL, 2 cHL) relapsed as EBV-negative by routine methods while showing EBNA1 expression in rare tumor cells by RNAscope. The relapse specimens were clonally identical to their onset biopsies, indicating that the lymphoma clone can largely loose the EBV genome over time but traces of EBV infection are still detectable by high-sensitivity methods. We suggest EBV may contribute to lymphoma pathogenesis more widely than currently acknowledged.

A "hit-and-run" affair - A possible link for cancer progression in virally driven cancers

BACKGROUND

It is well-known that certain cancers are caused by viruses. However, viral oncogenesis is complex and only a small fraction of the infected people develop cancer. Indeed, a number of environmental factors can contribute to virally infected cells developing cancer hallmarks, promoting tumorigenesis.

SCOPE OF REVIEW

The hit-and-run theory proposes that viruses facilitate the accumulation of mutations and promote genomic instability until the virus becomes dispensable for tumour maintenance. Indeed, several studies have reported viral genome, episome and/or oncogene loss in tumour cells without losing malignant phenotype.

MAJOR CONCLUSIONS

The current evidence supports the clear contribution of certain viruses to develop cancers. Importantly, the evidence supporting the sustained maintenance of malignancy after the loss of viral "presence" is sufficient to support the hit-and-run hypothesis of viral cancer development. Long-term tracking of vaccination outcome over the decades will test this theory.

GENERAL SIGNIFICANCE

If the hit-and-run theory is true, viruses might cause more cancers than previously thought and will have implications in the prevention of many cancers through implementing vaccination programs.

Molecular Pathogenesis of Hodgkin Lymphoma: Past, Present, Future

Our understanding of the tumorigenesis of classical Hodgkin lymphoma (cHL) and the formation of Reed–Sternberg cells (RS-cells) has evolved drastically in the last decades. More recently, a better characterization of the signaling pathways and the cellular interactions at play have paved the way for new targeted therapy in the hopes of improving outcomes. However, important gaps in knowledge remain that may hold the key for significant changes of paradigm in this lymphoma. Here, we discuss the past, present, and future of cHL, and review in detail the more recent discoveries pertaining to genetic instability, anti-apoptotic signaling pathways, the tumoral microenvironment, and host-immune system evasion in cHL.

Seroepidemiological analysis and literature review of the prevalence of Epstein-Barr virus and herpesvirus infections in pediatric cases with non-Hodgkin lymphoma in Central Europe

BACKGROUND

Epstein-Barr virus (EBV) is linked to a variety of malignancies; most endemic Burkitt lymphoma (BL) harbor EBV, whereas only a subset of the cases of sporadic BL is EBV positive.

PROCEDURE

We retrospectively determined the herpesvirus seroprevalence at the time of diagnosis in pediatric non-Hodgkin lymphoma (NHL) patients enrolled in NHL-BFM (Berlin-Frankfurt-Muenster) studies. We accessed the seroepidemiological data from 1147 patients that became available during 1990-2007. We included the records from patients 6 months to 18 years of age with BL, T-cell lymphoblastic lymphoma (T-LBL), lymphoblastic precursor B-cell lymphoma (pB-LBL), diffuse large B-cell lymphoma (DLBCL), or anaplastic large cell lymphoma (ALCL).

RESULTS

EBV seropositivity was significantly more frequent in patients with BL than in those with T-LBL. EBV was more prevalent in patients younger than 6 years of age and in patients with BL than in those with non-BL or T-LBL. Event-free survival was significantly lower in varicella-zoster-seronegative patients, but there was no indication of an association to complications due to varicella zoster infection. We found no associations between herpes simplex virus, varicella zoster virus, or human cytomegalovirus seroprevalence and the pediatric Central European NHL cases.

CONCLUSION

Early EBV exposure may increase the risk of BL in Central Europe. A higher involvement of EBV in European BL than originally reported appears at least probable. Our data support the thesis that the distinction between endemic and sporadic BL is artificial and should be replaced by the differentiation between EBV-positive and EBV-negative BL.

Lack of Hcv Infection in Malignant, Cells Refutes the Hypothesis of a Direct Transforming Action of the Virus in the Pathogenesis of Hcv-Associated B-Cell Nhls

Aims and background

Preliminary evidence suggests that hepatitis C virus (HCV) might play a pathogenetic role in autoimmune-related, non-malignant B-cell lymphoproliferation, as well as in a subset of B-cell non-Hodgkin's lymphomas (NHLs). With regard to the mechanism(s) by which HCV might favor B-cell expansion and malignant transformation, most data support an indirect pathogenetic role of the virus as an exogenous trigger. A direct oncogenetic role of HCV by direct cell infection and deregulation has only been hypothesized on the basis of the lymphotropism of the virus.

Methods

In this study we investigated the possible HCV infection of NHL B cells by means of sensitive and quantitative polymerase chain reaction (PCR) on affinity-purified neoplastic cells, and by HCV-specific immunohistochemistry and in situ hybridization.

Results

HCV infection of neoplastic B cells was documented in only three cases, namely the low-grade B-cell NHLs that arose in the course of mixed cryoglobulinemia syndrome (MC). HCV infection, below one viral genome per cell, was detectable only by PCR. All the remaining low-grade (one case) and high-grade B-cell NHLs (two cases) were HCV uninfected. Previous immunoglobulin gene analyses were consistent with an antigen-driven B-cell lymphoproliferation in the studied cases.

Conclusions

Overall, our data are consistent with an indirect oncogenetic role of HCV in B-cell lymphomagenesis as an exogenous trigger. Infection of B cells by HCV appears possible in some NHL subsets, but the implications remain unknown.

Genomic, Recombinational and Phylogenetic Characterization of Global Feline Herpesvirus 1 Isolates

Feline herpes virus type 1 (FHV-1) is widely considered to be the leading cause of ocular disease in cats and has been implicated in upper respiratory tract infections. Little, however is known about interstrain phylogenetic relationships, and details of the genomic structure. For the present study, twenty-six FHV-1 isolates from different cats in animal shelters were collected from eight separate locations in the USA, and the genomes sequenced. Genomic characterization of these isolates includied short sequence repeat (SSR) detection, with fewer SSRs detected, compared to herpes simplex viruses type 1 and 2. For phylogenetic and recombination analysis, 27 previously sequenced isolates of FHV-1 were combined with the 26 strains sequenced for the present study. The overall genomic interstrain genetic distance between all available isolates was 0.093%. Phylogenetic analysis identified four main FHV-1 clades primarily corresponding to geographical collection site. Recombination analysis suggested that interclade recombination has occurred.

Coordinated repression of BIM and PUMA by Epstein-Barr virus latent genes maintains the survival of Burkitt lymphoma cells

While the association of Epstein-Barr virus (EBV) with Burkitt lymphoma (BL) has long been recognised, the precise role of the virus in BL pathogenesis is not fully resolved. EBV can be lost spontaneously from some BL cell lines, and these EBV-loss lymphoma cells reportedly have a survival disadvantage. Here we have generated an extensive panel of EBV-loss clones from multiple BL backgrounds and examined their phenotype comparing them to their isogenic EBV-positive counterparts. We report that, while loss of EBV from BL cells is rare, it is consistently associated with an enhanced predisposition to undergo apoptosis and reduced tumorigenicity in vivo. Importantly, reinfection of EBV-loss clones with EBV, but surprisingly not transduction with individual BL-associated latent viral genes, restored protection from apoptosis. Expression profiling and functional analysis of apoptosis-related proteins and transcripts in BL cells revealed that EBV inhibits the upregulation of the proapoptotic BH3-only proteins, BIM and PUMA. We conclude that latent EBV genes cooperatively enhance the survival of BL cells by suppression of the intrinsic apoptosis pathway signalling via inhibition of the potent apoptosis initiators, BIM and PUMA.

Plasma Epstein Barr virus (EBV) DNA as a biomarker for EBV associated Hodgkin lymphoma

OBJECTIVE

To assess plasma Epstein-Barr virus (EBV) DNA as a biomarker of tumour burden at diagnosis and during therapy in children with Hodgkin lymphoma.

DESIGN

Case-control study, with prospective follow-up of the Hodgkin lymphoma cohort (2007-2012).

SETTING

Pediatric Hematology Oncology unit of a tertiary care hospital in Delhi.

PATIENTS

Thirty children with Hodgkin lymphoma and 70 sex and age-matched controls (benign lymphadenopathy 19, non-lym-phoid malignancy 29, Burkitt lymphoma 5, healthy children 17).

INTERVENTION

Positive EBV-staining on immunohistochemistry was defined as EBV-associated Hodgkin lymphoma. Plasma EBV real-time quantitative polymerase chain reaction (PCR) was tested at presentation, after first and last chemotherapy cycles, and on follow-up.

MAIN OUTCOME MEASURES

Plasma EBV quantitative PCR was compared between cases and controls. Its kinetics was assessed during and after chemotherapy.

RESULTS

EBV quantitative PCR was positive in 19 (63%) Hodgkin lymphoma cases (range 500 to 430,000 copies/mL), with 87.5% accuracy (kappa=0.69) as compared with EBV immunohistochemistry. Sensitivity and specificity of the quantitative PCR were 87.5% and 81.8%, respectively. Only boys showed positive EBV immunohistochemistry and,or quantitative PCR positivity. All controls were quantitative PCR negative. All quantitative PCR positive cases with follow up blood sample showed EBV clearance after the first cycle. A quantitative PCR negative case in long-term remission became positive at relapse. EBV status did not influence survival.

CONCLUSION

Plasma EBV-DNA, detectable in EBV-associated Hodgkin lymphoma, becomes undetectable early after initiating therapy. It can be used as a biomarker of treatment response in EBV-associated Hodgkin lymphoma.

The Role of Gammaherpesviruses in Cancer Pathogenesis

Worldwide, one fifth of cancers in the population are associated with viral infections. Among them, gammaherpesvirus, specifically HHV4 (EBV) and HHV8 (KSHV), are two oncogenic viral agents associated with a large number of human malignancies. In this review, we summarize the current understanding of the molecular mechanisms related to EBV and KSHV infection and their ability to induce cellular transformation. We describe their strategies for manipulating major cellular systems through the utilization of cell cycle, apoptosis, immune modulation, epigenetic modification, and altered signal transduction pathways, including NF-kB, Notch, Wnt, MAPK, TLR, etc. We also discuss the important EBV latent antigens, namely EBNA1, EBNA2, EBNA3’s and LMP’s, which are important for targeting these major cellular pathways. KSHV infection progresses through the engagement of the activities of the major latent proteins LANA, v-FLIP and v-Cyclin, and the lytic replication and transcription activator (RTA). This review is a current, comprehensive approach that describes an in-depth understanding of gammaherpes viral encoded gene manipulation of the host system through targeting important biological processes in viral-associated cancers.

Epstein- Barr Virus: Clinical and Epidemiological Revisits and Genetic Basis of Oncogenesis

Epstein-Barr virus (EBV) is classified as a member in the order herpesvirales, family herpesviridae, subfamily gammaherpesvirinae and the genus lymphocytovirus. The virus is an exclusively human pathogen and thus also termed as human herpesvirus 4 (HHV4). It was the first oncogenic virus recognized and has been incriminated in the causation of tumors of both lymphatic and epithelial nature. It was reported in some previous studies that 95% of the population worldwide are serologically positive to the virus. Clinically, EBV primary infection is almost silent, persisting as a life-long asymptomatic latent infection in B cells although it may be responsible for a transient clinical syndrome called infectious mononucleosis. Following reactivation of the virus from latency due to immunocompromised status, EBV was found to be associated with several tumors. EBV linked to oncogenesis as detected in lymphoid tumors such as Burkitt's lymphoma (BL), Hodgkin's disease (HD), post-transplant lymphoproliferative disorders (PTLD) and T-cell lymphomas (e.g. Peripheral T-cell lymphomas; PTCL and Anaplastic large cell lymphomas; ALCL). It is also linked to epithelial tumors such as nasopharyngeal carcinoma (NPC), gastric carcinomas and oral hairy leukoplakia (OHL). In vitro, EBV many studies have demonstrated its ability to transform B cells into lymphoblastoid cell lines (LCLs). Despite these malignancies showing different clinical and epidemiological patterns when studied, genetic studies have suggested that these EBV- associated transformations were characterized generally by low level of virus gene expression with only the latent virus proteins (LVPs) upregulated in both tumors and LCLs. In this review, we summarize some clinical and epidemiological features of EBV- associated tumors. We also discuss how EBV latent genes may lead to oncogenesis in the different clinical malignancies

The tumor virus landscape of AIDS-related lymphomas

Immunodeficiency dramatically increases susceptibility to cancer as a result of reduced immune surveillance and enhanced opportunities for virus-mediated oncogenesis. Although AIDS-related lymphomas (ARLs) are frequently associated with known oncogenic viruses, many cases contain no known transforming virus. To discover novel transforming viruses, we profiled a set of ARL samples using whole transcriptome sequencing. We determined that Epstein-Barr virus (EBV) was the only virus detected in the tumor samples of this cohort, suggesting that if unidentified pathogens exist in this disease, they are present in <10% of cases or undetectable by our methods. To evaluate the role of EBV in ARL pathogenesis, we analyzed viral gene expression and found highly heterogeneous patterns of viral transcription across samples. We also found significant heterogeneity of viral antigen expression across a large cohort, with many patient samples presenting with restricted type I viral latency, indicating that EBV latency proteins are under increased immunosurveillance in the post-combined antiretroviral therapies era. Furthermore, EBV infection of lymphoma cells in HIV-positive individuals was associated with a distinct host gene expression program. These findings provide insight into the joint host-virus regulatory network of primary ARL tumor samples and expand our understanding of virus-associated oncogenesis. Our findings may also have therapeutic implications, as treatment may be personalized to target specific viral and virus-associated host processes that are only present in a subset of patients.

Atypical Epstein-Barr viral genomic structure in lymphoma tissue and lymphoid cell lines

Epstein-Barr virus (EBV) DNA is found within the malignant cells of some subtypes of lymphoma, and viral presence is being exploited for improved diagnosis, monitoring, and management of affected patients. Recent work suggests that viral genomic polymorphism, such as partial deletion of the viral genome, could interfere with virus detection in tumor tissues. To test for atypical forms of the EBV genome, 98 lymphomas and 6 infected cell lines were studied using a battery of 6 quantitative polymerase chain reaction assays targeting disparate sections of EBV DNA. Fifty of the lymphomas (51%) had no amplifiable EBV DNA, and 38 lymphomas (39%) had low-level EBV infection that was deemed incidental based on EBV-encoded RNA (EBER) in situ hybridization results. The remaining 10 lymphomas (10%) had high EBV loads and EBER localization to malignant cells by EBER in situ hybridization. All 10 represented lymphoma subtypes were previously associated with EBV (Burkitt, diffuse large B-cell, or T-cell type), whereas no remnants of EBV were detected in other lymphoma subtypes (follicular, small lymphocytic, mantle cell, or marginal zone type). Interestingly, 4 of the 10 infected lymphomas had evidence of atypical viral genomes, including 3 of 4 infected T-cell lymphomas with aberrant loss of LMP2 amplicons, and a single diffuse large B-cell lymphoma lacking the central part of the viral genome spanning BamH1W, BZLF1, and EBNA1 gene segments. A reasonable screening strategy for infected malignancy involves applying EBER1 and LMP1 quantitative polymerase chain reaction assays and confirming that values exceeding 2000 copies of EBV per 100,000 cells have EBER localization to malignant cells.

Peripheral T-cell lymphomas of follicular T-helper cell derivation with Hodgkin/Reed-Sternberg cells of B-cell lineage: both EBV-positive and EBV-negative variants exist

Peripheral T-cell lymphomas (PTCLs) are functionally and morphologically complex. Epstein-Barr virus (EBV)-positive B cells have been reported in angioimmunoblastic T-cell lymphoma (AITL) and other PTCLs and may mimic Hodgkin/Reed-Sternberg (HRS) cells, but EBV-negative HRS-like B cells have not been described. We wished to assess the nature of the PTCL associated with HRS-like cells and to determine whether EBV-negative HRS-like cells may be seen. We identified 57 PTCL cases reported as containing HRS-like cells. These included 32 AITL, 19 PTCL, not otherwise specified (NOS), 3 PTCL-NOS, follicular variant, 1 PTCL-NOS, T-zone variant, and 2 adult T-cell leukemia/lymphoma cases. All patients were adults with a median age of 63 and presented with lymphadenopathy. The male:female ratio was 31:26 (1.2:1). Clonal TRG rearrangement was detected in 46/53 cases. Six of 38 cases had a concomitant clonal immunoglobulin gene rearrangement. In 52/57 cases the HRS cells were positive for EBV. Five cases, 3 classified as AITL and 2 as PTCL-NOS, follicular variant, contained HRS-like cells negative for EBV. All PTCLs with EBV-negative HRS cells had a T follicular helper cell immunophenotype. The neoplastic T cells expressed CD3, CD4, and PD-1 and formed rosettes around the HRS-like cells. The HRS-like cells were positive for CD20 (variable intensity), PAX5, CD30, and CD15 (4/5). We conclude that both EBV-positive and EBV-negative HRS-like B cells may occur in the background of PTCL; caution is needed to avoid misdiagnosis as classical Hodgkin lymphoma. The close interaction between the HRS-like cells and the rosetting PD-1-positive T cells suggests a possible pathogenetic role in this phenomenon and provides new insights into the abnormal B-cell proliferations that occur in the context of TFH malignancies.

Lymphoepithelioma-like carcinoma of the vulva: a case report

This report describes a lymphoepithelioma-like carcinoma of the vulva in a 64-year-old woman. The tumor showed distinct morphologic features including syncytial sheets of malignant epithelioid cells and a dense lymphoplasmacytoid infiltrate. In situ hybridization and immunohistochemistry for Epstein-Barr virus were negative. The tumor was treated by surgical excision. No evidence of recurrence has been detected 3 years after treatment. To our knowledge this is the second reported case of lymphoepithelioma-like carcinoma of the vulva.

Atypical prediagnosis Epstein-Barr virus serology restricted to EBV-positive Hodgkin lymphoma

An altered anti-Epstein-Barr virus (EBV) serologic profile preceding diagnosis is associated with an increased risk of Hodgkin lymphoma. It is unknown whether this atypical pattern predicts Hodgkin lymphoma risk further subdivided by determination of EBV in tumor cells. A nested case-control study of 128 incident Hodgkin lymphoma cases and 368 matched controls from active-duty military personnel with archived serum in the US Department of Defense Serum Repository was conducted to determine whether a panel of anti-EBV antibody titers differed in EBV(+) and EBV(-) Hodgkin lymphoma. Among 40 EBV(+) Hodgkin lymphoma cases and matched controls, statistically significant increased risks were associated with elevated anti-EBV VCA IgG antibody titers (relative risk = 3.1; 95% confidence interval [CI], 1.1-8.7), and an anti-EBNA-1/anti-EBNA-2 antibody ratio ≤ 1.0 versus > 1.0 (relative risk = 4.7; 95% CI, 1.6-13.8). In contrast, no significant associations were found among 88 EBV(-) Hodgkin lymphoma cases relative to their matched controls. In case-case analysis, EBV(+) disease was significantly associated with a low anti-EBNA-1/anti-EBNA-2 antibody ratio. This distinctive serologic response to EBV latent antigens, indicative of immune dysfunction in other clinical settings, is associated with an increased risk of developing EBV(+) but not EBV(-) Hodgkin lymphoma.

Epithelial cell retention of transcriptionally active, P3HR-1-derived heterogeneous Epstein-Barr virus DNA with concurrent loss of parental virus

Deleted, rearranged, heterogeneous (het) Epstein-Barr virus (EBV) DNA with the distinctive capability of disrupting EBV latency has been reported in biopsy samples of EBV-associated tumors whose onset in immunocompetent hosts is characteristically preceded by an antibody response indicative of EBV reactivation. Using the EBV P3HR-1 strain, we have reproduced in long-term culture of SVK epithelial cells an unusual pattern of infection previously observed in a subset of tumor biopsy samples: the persistence of het DNA in the absence of the parental helper virus. Fluorescence in situ hybridization (FISH) of infected cell subclones indicated the retention of het DNA in an integrated form. Incorporation of an intact het DNA molecule was confirmed by PCR, using primers that framed junctions of the four rearranged EBV DNA segments comprising P3HR-1-derived het DNA. Structural analysis of EBV terminal repeats revealed a banding pattern consistent with the integration of het DNA as a concatemer. Linkage of concatemeric monomers was defined at a nucleotide level, and that junctional sequence was detected in cell-free P3HR-1 virion DNA, confirming that subgenomic het DNA was packaged into infectious particles in a concatemeric configuration. Stable integration into cells having lost the standard viral genome allowed the unambiguous designation of het DNA as the source for viral gene products potentially encoded by both. Continuous expression of the latency-to-lytic switch protein Zta and detection of the BALF4 gene product gB, known to expand the target cell range of standard virus when incorporated at augmented levels into infectious progeny, add to a presumption of het DNA-enhanced pathogenesis in diseases of EBV reactivation.

Herpesvirus-associated lymphomas: Investigations in humans and animal models

Lymphomas are solid tumors consisting of lymphoid cells; they form a heterogeneous group of less or more malignant disorders. A portion of lymphomas develop due to latent herpesvirus infections established in B and/or T-lymphocytes. The basis for latency is a lifelong presence of the circularized covalently linked viral genome within nuclei of carrier lymphocytes. In certain cases, however, the essential event leading to tumor formation is the integration of a portion(s) of viral DNA into the host cell DNA. This leads to rearrangements within the host cell genome on one hand, and, on other hand, to unregulated expression of oncoproteins encoded by the integrated fragment. Our review deals with mechanisms of lymphoma formation regarding to the role of non-structural herpesvirus oncoproteins interfering with the regulation of cell division and/or exerting anti-apoptotic effects. In addition, the authors wish to highlight the common procedures, which allowed isolation and/or identification of lymphoma-associated viruses in cell cultures derived from tumors and/or proliferating lymphatic tissues.

Lymphomas differ in their dependence on Epstein-Barr virus

Epstein-Barr virus (EBV) encodes oncogenic information and, oftentimes concomitant with host immunosuppression, gives rise to malignancies in all major categories of lymphoma defined by the World Health Organization. Here, we conditionally evicted the viral extrachromosomal genome from tumor cells in vitro to examine the role of EBV in different lymphomas, including Burkitt lymphoma (BL) and posttransplant lymphoproliferative disorder. Cells derived from 2 canonical BLs were found to have the least dependence on the virus; some required EBV to prevent the inefficient induction of apoptosis. In contrast, cells derived from a subset of BL, Wp-restricted BL, required EBV to block a robust apoptotic program that involves the up-regulation of the proapoptotic protein Bim. Wp-restricted BL cells also relied on the virus to promote efficient proliferation, a distinction that highlights the multiple contributions EBV makes to affect proliferation of its host cells. Like Wp-BL cells, posttransplant lymphoproliferative disorder cells depended on the virus to inhibit apoptosis. They furthermore required the virus to drive them out of G(1)/G(0). Together, these results reveal a graded dependence on EBV among tumor cells that directly correlates with the number of viral genes expressed in the tumor cell.

Viral hit and run-oncogenesis: genetic and epigenetic scenarios

It is well documented that viral genomes either inserted into the cellular DNA or co-replicating with it in episomal form can be lost from neoplastic cells. Therefore, "hit and run"-mechanisms have been a topic of longstanding interest in tumor virology. The basic idea is that the transient acquisition of a complete or incomplete viral genome may be sufficient to induce malignant conversion of host cells in vivo, resulting in neoplastic development. After eliciting a heritable change in the gene expression pattern of the host cell (initiation), the genomes of tumor viruses may be completely lost, i.e. in a hit and run-scenario they are not necessary for the maintenance of the malignant state. The expression of viral oncoproteins and RNAs may interfere not only with regulators of cell proliferation, but also with DNA repair mechanisms. DNA recombinogenic activities induced by tumor viruses or activated by other mechanisms may contribute to the secondary loss of viral genomes from neoplastic cells. Viral oncoproteins can also cause epigenetic dysregulation, thereby reprogramming cellular gene expression in a heritable manner. Thus, we expect that epigenetic scenarios of viral hit and run-tumorigenesis may facilitate new, innovative experiments and clinical studies in spite of the fact that the regular presence of a suspected human tumor virus in an early phase of neoplastic development and its subsequent regular loss have not been demonstrated yet. We propose that virus-specific "epigenetic signatures", i.e. alterations of the host cell epigenome, especially altered DNA methylation patterns, may help to identify viral hit and run-oncogenic events, even after the complete loss of tumor viruses from neoplastic cells.

Genetic and phenotypic analysis of B-cell post-transplant lymphoproliferative disorders provides insights into disease biology

B-cell post-transplant lymphoproliferative disorders (PTLD) are classified as early lesions, polymorphic lymphomas (P-PTLD) and monomorphic lymphomas (M-PTLD). These morphologic categories are thought to reflect a biologic continuum, although supporting genetic data are lacking. To gain better insights into PTLD pathogenesis, we characterized the phenotypes, immunoglobulin (Ig) gene alterations and non-Ig gene (BCL6, RhoH/TTF, c-MYC, PAX5, CIITA, BCL7A, PIM1) mutations of 21 PTLD, including an IM-like lesion, 8 P-PTLD and 12 M-PTLD. Gene expression profile analysis was also performed in 12 cases. All PTLD with clonal Ig rearrangements showed evidence of germinal centre (GC) transit based on the analysis of Ig and BCL6 gene mutations, and 74% had a non-GC phenotype (BCL6 +/- MUM1+). Although surface Ig abnormalities were seen in 6/19 (32%) PTLD, only three showed 'crippling' Ig mutations indicating other etiologies for loss of the B-cell receptor. Aberrant somatic hypermutation (ASHM) was almost exclusively observed in M-PTLD (8/12 vs. 1/8 P-PTLD) and all three recurrent cases analysed showed additional mutations in genes targeted by ASHM. Gene expression analysis showed distinct clustering of PTLD compared to B-cell non-Hodgkin lymphomas (B-NHL) without segregation of P-PTLD from non-GC M-PTLD or EBV+ from EBV- PTLD. The gene expression pattern of PTLD appeared more related to that of memory and activated B-cells. Together, our results suggest that PTLD represent a distinct type of B-NHL deriving from an antigen experienced B-cell, whose evolution is associated with accrual of genetic lesions.

Multiple pathways for Epstein-Barr virus episome loss from nasopharyngeal carcinoma

Epstein-Barr virus (EBV) is the prototypical example for episomal persistence of genetic information. Yet, little is known about how this viral episome is lost. Episome loss occurs naturally in nasopharyngeal carcinoma (NPC) upon explantation into culture. Using whole-genome profiling, we found evidence for 2 different pathways of episome loss: (i) rapid loss of the entire episome or (ii) successive mutation/deletion of the episome until at least 1 essential cis-element is destroyed. This second phenotype was seen in a clone of HONE-1 NPC cells that maintains the EBV episome for prolonged time in culture. The conceptual insights provided by our quantitative analysis should aid our understanding of mammalian episomes, as well as lead to designs to cure latent viral infection.

Racial/ethnic variation in EBV-positive classical Hodgkin lymphoma in California populations

Epstein-Barr virus (EBV) is detected in the tumor cells of some but not all Hodgkin lymphoma (HL) patients, and evidence indicates that EBV-positive and -negative HL are distinct entities. Racial/ethnic variation in EBV-positive HL in international comparisons suggests etiologic roles for environmental and genetic factors, but these studies used clinical series and evaluated EBV presence by differing protocols. Therefore, we evaluated EBV presence in the tumors of a large (n = 1,032), racially and sociodemographically diverse series of California incident classical HL cases with uniform pathology re-review and EBV detection methods. Tumor EBV-positivity was associated with Hispanic and Asian/Pacific Islander (API) but not black race/ethnicity, irrespective of demographic and clinical factors. Complex race-specific associations were observed between EBV-positive HL and age, sex, histology, stage, neighborhood socioeconomic status (SES), and birth place. In Hispanics, EBV-positive HL was associated not only with young and older age, male sex, and mixed cellularity histology, but also with foreign birth and lower SES in females, suggesting immune function responses to correlates of early childhood experience and later environmental exposures, respectively, as well as of pregnancy. For APIs, a lack of association with birth place may reflect the higher SES of API than Hispanic immigrants. In blacks, EBV-positive HL was associated with later-stage disease, consistent with racial/ethnic variation in certain cytokine polymorphisms. The racial/ethnic variation in our findings suggests that EBV-positive HL results from an intricate interplay of early- and later-life environmental, hormonal, and genetic factors leading to depressed immune function and poorly controlled EBV infection.

Points of recombination in Epstein-Barr virus (EBV) strain P3HR-1-derived heterogeneous DNA as indexes to EBV DNA recombinogenic events in vivo

Deletions and rearrangements in the genome of Epstein-Barr virus (EBV) strain P3HR-1 generate subgenomic infectious particles that, unlike defective interfering particles in other viral systems, enhance rather than restrict EBV replication in vitro. Reports of comparable heterogeneous (het) DNA in EBV-linked human diseases, based on detection of an abnormal juxtaposition of EBV DNA fragments BamHI W and BamHI Z that disrupts viral latency, prompted us to determine at the nucleotide level all remaining recombination joints formed by the four constituent segments of P3HR-1-derived het DNA. Guided by endonuclease restriction maps, we chose PCR primer pairs that approximated and framed junctions creating the unique BamHI M/B1 and E/S fusion fragments. Sequencing of PCR products revealed points of recombination that lacked regions of extensive homology between constituent fragments. Identical recombination junctions were detected by PCR in EBV-positive salivary samples from human immunodeficiency virus-infected donors, although the W/Z rearrangement that induces EBV reactivation was frequently found in the absence of the other two. In vitro infection of lymphoid cells similarly indicated that not all three het DNA rearrangements need to reside on a composite molecule. These results connote a precision in the recombination process that dictates both composition and regulation of gene segments altered by genomic rearrangement. Moreover, the apparent frequency of het DNA at sites of EBV replication in vivo is consistent with a likely contribution to the pathogenesis of EBV reactivation.

Rapid onset proptosis and vision loss as the initial presentation of Burkitt lymphoma

Burkitt lymphoma is a rapidly growing, high-grade non-Hodgkin lymphoma occurring in three distinct clinical subtypes: endemic, sporadic, and human immunodeficiency associated. The sporadic subtype typically presents as an abdominal mass. Orbital involvement has rarely been reported. The authors report a case of Burkitt lymphoma presenting as rapidly progressive proptosis and loss of vision. Given the tumor's rapid growth rate, potential for vision loss, and good response to chemotherapy, clinicians should be aware of this rare presentation.

Contribution of the Epstein Barr virus to the molecular pathogenesis of Hodgkin lymphoma

Although the morphology of the pathognomonic Reed-Sternberg cells of Hodgkin lymphoma (HL) was described over a century ago, it was not until recently that their origin from B lymphocytes was recognised. The demonstration that a proportion of cases of HL harbour the Epstein-Barr virus (EBV) and that its genome is monoclonal in these tumours suggests that the virus contributes to the development of HL in some cases. This review summarises current knowledge of the pathogenesis of HL with particular emphasis on the association with EBV.

The critical role of histology in an era of genomics and proteomics: a commentary and reflection

The role of histologic examination in lymphoma diagnosis has been called into question by proponents of new technologies, such as genomics and proteomics. We review the history and salient features of morphologic evaluation in lymphoid diseases, and discuss the general and specific limitations of mature ancillary techniques, such as immunohistochemistry, flow cytometry, and molecular studies. We then speculate on the future relationship between morphology and the new genomic and proteomic technologies as they become integrated into clinical practice.

Epstein-Barr Virus Negative Clonal Plasma Cell Proliferations and Lymphomas in Peripheral T-cell Lymphomas

Clonal B-cell populations have been described in peripheral T-cell lymphomas (PTCL) as secondary Epstein-Barr virus (EBV) driven B-cell expansions that may evolve to an overt B-cell lymphoma. EBV-negative B-cell proliferations associated with T-cell lymphomas are uncommon and not well characterized. We studied 15 patients who developed an EBV-negative B-cell proliferation or malignant lymphoma associated with PTCL. The T-cell tumors were 8 PTCL, not otherwise specified, 4 angioimmunoblastic T-cell lymphomas, and 3 cutaneous PTCL. The B-cell component was intermingled with the PTCL in all patients and it was classified as clonal/monotypic plasma cell proliferation in 8 lesions, clonal/monotypic large B-cell proliferation in 4 patients, and B-cell lymphoma with plasmacytic/plasmablastic differentiation in 3 patients. Two patients had 2 clonally unrelated plasma cell proliferations associated with the same PTCL. All cases showed cytoplasmic Ig light chain restriction. Clonal IgH and T-cell receptor rearrangements were detected in 11/12 and 11/13 cases examined, respectively. EBV, cytomegalovirus, and HHV-8 were not observed in any of the examined cases. Sequential samples in 7 patients showed persistence of the PTCL and the B-cell component in 4, the PTCL without the B-cell lymphoma in 2, and progression of the B-cell neoplasm in 1. Patients followed an aggressive clinical course similar to conventional PTCL. In conclusion, EBV-negative clonal or mononotypic B-cell proliferations in patients with PTCL present with a spectrum of lesions ranging from plasma cell proliferations to overt lymphomas with plasmacytic/plasmablastic features. The distinctive features of these patients suggest that these lesions represent a specific phenomenon in PTCL.

Epstein-Barr virus integrates frequently into chromosome 4q, 2q, 1q and 7q of Burkitt's lymphoma cell line (Raji)

Epstein-Barr virus (EBV) integration into a Burkitt's lymphoma (BL) cell line (Raji) was investigated, using polymerase chain reaction (PCR), Southern hybridization, genomic library screening and fluorescence in situ hybridization (FISH). BaMHIW fragments of the EBV genome and DNA sequences of the viral latent membrane protein (LMP)1 and LMP2 genes were detected in Raji cells. BaMHI-digested high-molecular weight DNA from Raji cells generated 4 and 10 kb, 23 kb fragments that hybridized to Probe-1 (EBV genome 13232-16189) and Probe-2 (EBV genome 5-3271). Genomic library for Raji cells was constructed. Plaques (1 x 10(5)) were screened with Probe-2, and four positive clones were obtained. Chromosomal integration of EBV DNA was detected in the Raji cell. The viral integration sites included 1p, 1q, 2q, 3p, 3q, 4q, 5q, 6q, 7p, 7q, 9q, 11p, 14q and 15q. Despite this multiplicity of integration sites, integration showed high frequency only at the sites 4q, 2q, 1q and 7q; 64% of the total signals were found in these four chromosomal bands. No viral integration occurred in chromosomes 16-22 or the sex chromosomes (X, Y). This study is the first comprehensive FISH analysis of EBV integration into the chromosomes of the Raji cell line. The findings support the notion that EBV integrates into the Raji cell genome non-randomly.

Analysis of immunoglobulin heavy and light chain variable genes in post-transplant lymphoproliferative disorders

Post-transplant lymphoproliferative disorders (PTLD) derive from antigen-experienced B-cells and represent a major complication of solid organ transplantation. We characterized usage, mutation frequency and mutation pattern of immunoglobulin variable (IGV) gene rearrangements in 50 PTLD (polymorphic PTLD, n=10; diffuse large B-cell lymphoma, n=35; and Burkitt/Burkitt-like lymphoma, n=5). Among PTLD yielding clonal IGV amplimers, a functional IGV heavy chain (IGHV) rearrangement was found in 40/50 (80.0%) cases, whereas a potentially functional IGV light chain rearrangement was identified in 36/46 (78.3%) PTLD. By combining IGHV and IGV light chain rearrangements, 10/50 (20.0%) PTLD carried crippling mutations, precluding expression of a functional B-cell receptor (BCR). Immunohistochemistry showed detectable expression of IG light chains in only 18/43 (41.9%) PTLD. Failure to detect a functional IGV rearrangement associated with lack of IGV expression. Our data suggest that a large fraction of PTLD arise from germinal centre (GC)-experienced B-cells that display impaired BCR. Since a functional BCR is required for normal B-cell survival during GC transit, PTLD development may implicate rescue from apoptosis and expansion of B-cells that have failed the GC reaction. The high frequency of IGV loci inactivation appears to be a peculiar feature of PTLD among immunodeficiency-associated lymphoproliferations.

Reactive oxygen signaling and MAPK activation distinguish Epstein-Barr Virus (EBV)-positive versus EBV-negative Burkitt's lymphoma

Burkitt's lymphoma (BL) is an aggressive B cell neoplasm, which is one of the most common neoplasms of childhood. It is highly widespread in East Africa, where it appears in endemic form associated with Epstein-Barr virus (EBV) infection, and around the world in a sporadic form in which EBV infection is much less common. In addition to being the first human neoplasm to be associated with EBV, BL is associated with a characteristic translocation, in which the Ig promoter is translocated to constitutively activate the c-myc oncogene. Although many BLs respond well to chemotherapy, a significant fraction fails to respond to therapy, leading to death. In this article, we demonstrate that EBV-positive BL expresses high levels of activated mitogen-activated protein kinase and reactive oxygen species (ROS), and that ROS directly regulate NF-kappaB activation. EBV-negative BLs exhibit activation of phosphoinositol 3-kinase, but do not have elevated levels of ROS. Elevated reactive oxygen may play a role in diverse forms of viral carcinogenesis in humans, including cancers caused by EBV, hepatitis B, C, and human T cell lymphotropic virus. Our findings imply that inhibition of ROS may be useful in the treatment of EBV-induced neoplasia.

A 30 kb region of the Epstein-Barr virus genome is colinear with the rearranged human immunoglobulin gene loci: implications for a "ping-pong evolution" model for persisting viruses and their hosts. A review

The left part of the Epstein-Barr virus (EBV) genome exhibits a strong colinearity of structural and functional elements with the immunoglobulin (Ig) gene loci which is only partially reflected in nucleotide sequence homologies. We propose that this colinearity may be the result of an inter-dependent co-evolution of the immunoglobulin loci together with EBV. Our observation could help elucidating the mechanisms of somatic hypermutation, explaining the ability of EBV to accidentally cause tumors, and shedding more light on the general mechanisms of viral and organismal evolution. We suggest that persisting viruses served as a complement for the organismal germline like in a ping-pong game and outline The Ping-Pong Evolution Hypothesis.

B cells under influence: transformation of B cells by Epstein-Barr virus

Epstein-Barr virus (EBV) is an extremely successful virus, infecting more than 90% of the human population worldwide. After primary infection, the virus persists for the life of the host, usually as a harmless passenger residing in B cells. However, EBV can transform B cells, which can result in the development of malignant lymphomas. Intriguingly, the three main types of EBV-associated B-cell lymphoma - that is, Burkitt lymphoma, Hodgkin lymphoma and post-transplant lymphomas - seem to derive from germinal-centre B cells or atypical survivors of the germinal-centre reaction in most, if not all, cases, indicating that EBV-infected germinal-centre B cells are at particular risk for malignant transformation.

Epstein-Barr virus and oncogenesis: from latent genes to tumours

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumours. As a common virus infection, EBV appears to have evolved to exploit the process of B cell development to persist as a life-long asymptomatic infection. However, the virus can contribute to oncogenesis as evidenced by its frequent detection in certain tumours, namely Burkitt's lymphoma (BL), post-transplant B cell lymphomas, Hodgkin's disease (HD) and nasopharyngeal carcinoma (NPC), and by its unique ability to efficiently transform resting B cells in vitro into permanently growing lymphoblastoid cell lines (LCLs). These transforming effects are associated with the restricted expression of EBV genes such that only a subset of so-called latent virus proteins are expressed in virus infected tumours and in LCLs. Distinct forms of EBV latency are manifest in the different tumours and these appear to be a vestige of the pattern of latent gene expression used by the virus during the establishment of persistent infection within the B cell pool. This review summarises our current knowledge of EBV latent gene function and how this relates to the role of the virus in the aetiology of different tumours.

Hodgkin lymphoma and Epstein-Barr virus (EBV): no evidence to support hit-and-run mechanism in cases classified as non-EBV-associated

The Epstein-Barr virus (EBV) is associated with a proportion of Hodgkin lymphoma (HL) cases, and this association is believed to be causal. The aetiology of cases lacking EBV in the tumour cells (EBV HRS-ve), which make up the majority of cases in western countries, is obscure. It has been suggested that EBV may also cause these tumours by using a hit-and-run mechanism. Support for this idea comes from the finding that most young adult patients, who are likely to have a good immune response to EBV, have EBV HRS-ve HL. We investigated this possibility using a combined serologic and molecular approach. Analysis of EBV seroprevalence rates in an epidemiologic study of young adult HL revealed that cases with EBV HRS-ve HL were more likely to be EBV-seronegative than controls. Furthermore, additional studies clearly showed that some HL patients have never been infected by EBV. Quantitative PCR was used to look for the presence of deleted EBV genomes in a series of adult cases with both EBV HRS+ve and HRS-ve HL. Subgenomic fragments were detected in equimolar proportions. This study, therefore, found no evidence to support the idea that a hit-and-run mechanism involving EBV plays a role in the pathogenesis of HL.

Evolution of classic Hodgkin lymphoma in correlation to changes in the lymphoid organ structure of vertebrates

In order to integrate evolutionary concepts into lymphoma research we mapped features of classic Hodgkin lymphoma (a disease which has been recently described to be derived from germinal center B-cells) onto a phylogenetic tree of vertebrates. Secondly, we matched the phylogenetic occurrence of classic Hodgkin lymphoma to the changes in the lymphoid organ structure during vertebrate evolution. According to our analysis, classic Hodgkin lymphoma evolved exclusively at the developmental stage of mammals. Interestingly the appearance of Hodgkin lymphoma is correlated to the evolution of germinal centers in mammals. This lends some credit to the hypothesis that genes specific to the germinal center reaction are involved in the pathogenesis of Hodgkin lymphoma. However, as evolution did not stop at the developmental stage of the mammalian stem-species, to a certain extent species with specific differences of classic Hodgkin lymphoma can be expected. One such difference is that classic Hodgkin lymphoma occurs with a significantly higher frequency in humans than in all other mammals. This could be partially due to Epstein-Barr virus (EBV) infection in approximately 40%-50% of Hodgkin disease cases, that is associated with an expression of the EBV-encoded oncogen LMP-1. In conclusion we propose that the mapping of lymphoma related characteristics onto a phylogenetic tree is a valuable new tool in lymphoma research.

Viruses and Hodgkin's lymphoma

Hodgkin's lymphoma (HL) is unusual among human malignancies in that the epidemiology suggests an infectious aetiology. The Epstein-Barr virus (EBV) is associated with a proportion of cases and this association is believed to be causal. In these cases the Hodgkin and Reed-Sternberg (HRS) cells express the EBV-encoded proteins LMP1 and LMP2, which can mimic CD40 and the B cell receptor, respectively, and therefore may play a critical role in facilitating the survival of HRS cells. EBV-associated and non-EBV-associated HL cases have different epidemiological features and recent data suggest that delayed exposure to EBV is a risk factor for the development of EBV-associated HL in young adults. We suggest that HL can be divided into four entities on the basis of EBV status and age at presentation, with three groups of EBV-associated cases and a single group of EBV-negative cases. The aetiology of the latter cases is obscure although involvement of an infectious agent(s) is suspected.

Molecular biology of Hodgkin's lymphoma

Hodgkin's lymphoma (HL) is characterized by typical mononucleated Hodgkin and multinucleated Reed-Sternberg cells, which occur at low frequency in a mixed cellular infiltrate in the tumor tissue. Because of the rarity of these cells and their unusual immunophenotype, which is strikingly different from those of all normal hematopoietic cell types, the origin of these cells and their clonality have long been unclear. Single-cell studies of rearranged immunoglobulin genes showed that Hodgkin and Reed-Sternberg (HRS) cells represent clonal tumor-cell populations derived from germinal center B cells. In classical HL, the detection of obviously crippling immunoglobulin gene mutations in a fraction of the cases suggests that HRS cells may derive from germinal center B cells that have lost the capacity to be positively selected by antigen and that normally would have undergone apoptosis. In rare cases, HRS cells represent transformed T lymphocytes. The transforming events involved in malignant transformation of HRS cells are still largely unknown. Constitutive activation of the transcription factor NFkappaB, which can, for example, be induced through Epstein-Barr virus transformation of HRS cells or destructive somatic mutations of the inhibitor of NFkappaB, is likely to be a key event in HL pathogenesis. Significant progress has been made in our understanding of the cellular interactions in HL tissues, which are mainly mediated by a large variety of cytokines and chemokines.

Promiscuous expression of Epstein-Barr virus genes in Burkitt's lymphoma from the central African country Malawi

Primary BL in Malawian children has a very high frequency association, approaching 100%, with the human herpesvirus EBV. A detailed study carried out on viral gene expression in these tumours, using both fresh material and methanol-fixed FNAs, showed, contrary to prediction, that most belong to a variant "class II" latency category, with lytic cycle-related genes also expressed. That is, in addition to EBNA1 expression, membrane proteins (LMP1/2A), immediate early (BZLF1) and early (IR2 and IR4) genes, a putative viral oncogene (BARF1), CST (BART) antisense transcripts and the viral bcl-2 homologue are expressed in a high proportion of the BLs. Most, but not all, express the small viral (EBER) RNAs. Two other significant observations were made: (i) in addition to expression of cellular cytokine (IL-10) transcripts in all tumours investigated, the normally silent viral IL-10 homologue was expressed in some tumours; (ii) whereas EBNA1 expression from its restricted Qp promoter was generally observed, the nonrestricted Cp/Wp promoter was also active in some tumours. Viral gene expression in the Malawian [endemic (e)] BLs appears to be more promiscuous than predicted from other studies, but expression accords with the cytopathologic picture of eBLs as a rapidly proliferating cell population accompanied by considerable necrosis, and a clinically diverse disease. A small-scale study of relapse Malawian BLs revealed a different picture of viral association, more akin to systemic BL than eBL, where EBV appears to be absent or present only at very low levels. The significance of these findings is considered.

Epstein-Barr virus (EBV)-positive pyothorax-associated lymphoma (PAL): chromosomal integration of EBV in a novel CD2-positive PAL B-cell line

Pyothorax-associated lymphoma (PAL) is a clinico-pathological entity arising in the pleural cavity of patients with long-standing inflammatory pyothorax. PAL is closely associated with Epstein-Barr virus (EBV), but how this virus contributes to the development of the lymphoma is unknown. We have successfully obtained a novel EBV-infected PAL cell line, designated Pal-1. The cell line and its source coexpressed CD2 and CD20 molecules, but other representative B- and T-cell markers such as CD1, CD3, CD5, CD7, CD10 and CD19 were not found. The B-cell origin of Pal-1 cells was proven by rearrangement of the immunoglobulin heavy- and light-chain genes without rearranged T-cell receptor genes. Both the cell line and primary tumour cells carried monoclonal EBV genome. Although EBV genome is known to be maintained as circular extrachromosomal DNA, neither circular nor linear extrachromosomal EBV DNA was detectable in Pal-1 cells by in situ lysis gel analysis. Fluorescence in situ hybridization demonstrated viral integration at a marker chromosome mostly consisting of the centromere region of chromosome 1. The viral integration event may enhance a chromosomal instability at the insertion site. This cell line represents the first example of EBV integration in PAL and could enable the study of the potential role of integrated viral infection in the development of PAL as well as mechanism of the aberrant phenotype expression.

Role of Epstein-Barr virus and cytomegalovirus in the etiology of benign parotid tumors

BACKGROUND

Pleomorphic adenomas and Warthin's tumors are the two most common benign parotid tumors. Previous studies investigating the role of viruses in tumorigenesis of these neoplasms have been conflicting. The aim of this study was to determine whether Epstein-Barr virus (EBV) or cytomegalovirus (CMV) might play a role in the pathogenesis of pleomorphic adenomas and Warthin's tumors.

METHODS

Paraffin-embedded surgical specimens of 24 pleomorphic adenomas, 10 Warthin's tumors, and 13 normal parotid tissues were obtained from the University of California-San Francisco Pathology Department. Genomic DNA was extracted from the specimens, and primers for connexin 26, a gap junction protein, were used to confirm the integrity of this DNA. The presence or absence of EBV and CMV DNA within the samples was determined with PCR-based assays, in which radiolabeled primers were used for maximal sensitivity of detection.

RESULTS

PCR analysis of serially diluted control DNA revealed that using radiolabeled primers, five copies of viral DNA could be detected. By use of this method, we showed that none of the 24 pleomorphic adenomas, 10 Warthin's tumors, or 13 normal parotid samples contained EBV DNA or CMV DNA.

CONCLUSIONS

These results do not support CMV or EBV as etiologic factors in pleomorphic adenomas or Warthin's tumors. In addition, normal parotid seems not to harbor either of these viruses. Future studies with larger numbers of specimens are needed to confirm these findings.

A defective, rearranged Epstein-Barr virus genome in EBER-negative and EBER-positive Hodgkin's disease

A ubiquitous herpesvirus that establishes life-long infection, the Epstein-Barr virus (EBV) has yielded little insight into how a single agent in general accord with its host can produce diverse pathologies ranging from oral hairy leukoplakia to nasopharyngeal carcinoma, from infectious mononucleosis to Hodgkin's disease (HD) and Burkitt's lymphoma. Its pathogenesis is further confounded by the less than total association of virus with histologically similar tumors. In other viral systems, defective (interfering) viral genomes are known to modulate outcome of infection, with either ameliorating or intensifying effects on disease processes initiated by prototype strains. To ascertain whether defective EBV genomes are present in HD, we examined paraffin-embedded tissue from 56 HD cases whose EBV status was first determined by cytohybridization for nonpolyadenylated EBV RNAs (EBERs). Using both standard polymerase chain reaction (PCR) and PCR in situ hybridization, we successfully amplified sequences that span abnormally juxtaposed BamHI W and Z fragments characteristic of defective heterogeneous (het) EBV DNA from 10 of 32 (31%) EBER-positive tumors. Of 24 EBER-negative HD, 8 yielded PCR products indicating presence of het EBV DNA. Two of these contained defective EBV in the apparent absence of the prototype virus. Of the 42 tumors analyzed for defective EBV by both PCR techniques, there was concordance of results in 38 (90%). Detection of defective EBV genomes with the potential to disrupt viral gene regulation suggests one mechanism for pathogenic diversity that may also account for loss of prototypic EBV from individual tumor cells.