Burkitt lymphoma: pathogenesis and immune evasion

The role of viruses in cancer progression versus cancer treatment: A dual paradigm

Most human malignancies are attributed to exposure to infectious organisms such as viruses. Certain infections that can induce cancer can evade the immune system, leading to persistent inflammation that facilitates uncontrolled cell growth. Moreover, these pathogens can increase the likelihood of oncogenic transformation, leading to cancer development. Despite significant advancements in medicine, oncological research continues to seek innovative treatment techniques in light of the constraints imposed by traditional therapeutic agents. Virus-based therapy is a novel treatment method that has garnered significant interest due to its broad range of applications. Virotherapy employs oncolytic viruses that are genetically modified to target tumor cells specifically, undergo replication inside them and destroy the malignant cells. Additionally, this therapeutic approach elicits an anticancer response by boosting the patient's immune system. In addition, viruses are commonly employed as targeted delivery vectors for the precise transportation of various genes, medicinal compounds and immune-stimulating substances. Furthermore, virotherapy offers more excellent anticancer activity in combination with established treatment modalities such as immune therapy, chemotherapy and radiation therapy. This review presents a concise overview of the roles played by infectious agents, such as viruses in cancer progression. In addition, we have thoroughly summarized the advancements in utilizing viruses for their oncolytic properties in conjunction with established cancer treatment modalities such as chemotherapy, radiation and immunotherapy.

Mechanism and therapeutic implications of pomalidomide-induced immune surface marker upregulation in EBV-positive lymphomas

Epstein-Barr virus (EBV) downregulates immune surface markers to avoid immune recognition. Pomalidomide (Pom) was previously shown to increase immune surface marker expression in EBV-infected tumor cells. We explored the mechanism by which Pom leads to these effects in EBV-infected cells. Pom increased B7-2/CD86 mRNA, protein, and surface expression in EBV-infected cells but this was virtually eliminated in EBV-infected cells made resistant to Pom-induced cytostatic effects. This indicates that Pom initiates the upregulation of these markers by interacting with its target, cereblon. Interestingly, Pom increased the proinflammatory cytokines IP-10 and MIP-1∝/β in EBV infected cells, supporting a possible role for the phosphoinositide 3-kinase (PI3K)/AKT pathway in Pom's effects. Idelalisib, an inhibitor of the delta subunit of PI3 Kinase, blocked AKT-Ser phosphorylation and Pom-induced B7-2 surface expression. PU.1 is a downstream target for AKT that is expressed in EBV-infected cells. Pom treatment led to an increase in PU.1 binding to the B7-2 promoter based on ChIP analysis. Thus, our data indicates Pom acts through cereblon leading to degradation of Ikaros and activation of the PI3K/AKT/PU.1 pathway resulting in upregulation of B7-2 mRNA and protein expression. The increased immune recognition in addition to the increases in proinflammatory cytokines upon Pom treatment suggests Pom may be useful in the treatment of EBV-positive lymphomas.

Epstein‒Barr virus-associated cellular immunotherapy

Epstein‒Barr virus (EBV) is a human herpes virus that is saliva-transmissible and universally asymptomatic. It has been confirmed that more than 90% of the population is latently infected with EBV for life. EBV can cause a variety of related cancers, such as nasopharyngeal carcinoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Currently, many clinical studies have demonstrated that EBV-specific cytotoxic T lymphocytes and other cell therapies can be safely and effectively transfused to prevent and treat some diseases caused by EBV. This review will mainly focus on discussing EBV-specific cytotoxic T lymphocytes and will touch on therapeutic EBV vaccines and chimeric antigen receptor T-cell therapy briefly.

Clinical and Therapeutic Implications of Epstein-Barr Virus in HIV-Related Lymphomas

The incidence of lymphomas is increased in people living with HIV (PLWH). Aggressive B-cell non-Hodgkin lymphomas (NHLs) are the most common and are considered an AIDS-defining cancer (ADC). Although Hodgkin lymphoma (HL) is not considered an ADC, its incidence is also increased in PLWH. Among all HIV-related lymphomas (HRL), the prevalence of Epstein-Barr virus (EBV) is high. It has been shown that EBV is involved in different lymphomagenic mechanisms mediated by some of its proteins, contributing to the development of different lymphoma subtypes. Additionally, cooperation between both HIV and EBV can lead to the proliferation of aberrant B-cells, thereby being an additional lymphomagenic mechanism in EBV-associated HRL. Despite the close relationship between EBV and HRL, the impact of EBV on clinical aspects has not been extensively studied. These lymphomas are treated with the same therapeutic regimens as the general population in combination with cART. Nevertheless, new therapeutic strategies targeting EBV are promising for these lymphomas. In this article, the different types of HRL are extensively reviewed, focusing on the influence of EBV on the epidemiology, pathogenesis, clinical presentation, and pathological characteristics of each lymphoma subtype. Moreover, novel therapies targeting EBV and future strategies to treat HRL harboring EBV are discussed.

Nanoemulsomes for Enhanced Oral Bioavailability of the Anticancer Phytochemical Andrographolide: Characterization and Pharmacokinetics

Andrographolide (AG) is an antitumor phytochemical that acts against non-Hodgkin's lymphoma. However, AG shows low oral bioavailability due to extensive first-pass metabolism and P-glycoprotein efflux. Novel biocompatible lipoprotein-simulating nanosystems, emulsomes (EMLs), have gained significant attention due to their composition of natural components, in addition to being lymphotropic. Loading AG on EMLs is believed to mitigate the disadvantage of AG and enhance its lymphatic transport. This study developed a chylomicron-simulating system (EMLs) as a novel tool to overcome the AG oral delivery obstacles. Optimized EML-AG had a promising vesicular size of 281.62 ± 1.73 nm, a zeta potential of - 22.73 ± 0.06 mV, and a high entrapment efficiency of 96.55% ± 0.25%, which favors lymphatic targeting. In vivo pharmacokinetic studies of EML-AG showed significant enhancement (> sixfold increase) in the rate and extent of AG absorption compared with free AG. However, intraperitoneal injection of a cycloheximide inhibitor caused a significant decrease in AG absorption (~ 52%), confirming the lymphatic targeting potential of EMLs. Therefore, EMLs can be a promising novel nanoplatform for circumventing AG oral delivery obstacles and provide targeted delivery to the lymphatic system at a lower dose with fewer side effects.

Immune landscape in Burkitt lymphoma reveals M2-macrophage polarization and correlation between PD-L1 expression and non-canonical EBV latency program

BACKGROUND

The Tumor Microenviroment (TME) is a complex milieu that is increasingly recognized as a key factor in multiple stages of disease progression and responses to therapy as well as escape from immune surveillance. However, the precise contribution of specific immune effector and immune suppressor components of the TME in Burkitt lymphoma (BL) remains poorly understood.

METHODS

In this paper, we applied the computational algorithm CIBERSORT to Gene Expression Profiling (GEP) datasets of 40 BL samples to draw a map of immune and stromal components of TME. Furthermore, by multiple immunohistochemistry (IHC) and multispectral immunofluorescence (IF), we investigated the TME of additional series of 40 BL cases to evaluate the role of the Programmed Death-1 and Programmed Death Ligand-1 (PD-1/PD-L1) immune checkpoint axis.

RESULTS

Our results indicate that M2 polarized macrophages are the most prominent TME component in BL. In addition, we investigated the correlation between PD-L1 and latent membrane protein-2A (LMP2A) expression on tumour cells, highlighting a subgroup of BL cases characterized by a non-canonical latency program of EBV with an activated PD-L1 pathway.

CONCLUSION

In conclusion, our study analysed the TME in BL and identified a tolerogenic immune signature highlighting new potential therapeutic targets.

Epstein Barr Virus Associated Lymphomas and Epithelia Cancers in Humans

Epstein Barr virus (EBV) is a cosmopolitan oncogenic virus, infecting about 90% of the world's population and it is associated to tumors originating from both epithelia and hematopoietic cells. Transmission of the virus is mainly through oral secretions; however, transmission through organ transplantation and blood transfusion has been reported. In order to evade immune recognition, EBV establishes latent infection in B lymphocytes where it expresses limited sets of proteins called EBV transcription programs (ETPs), including six nuclear antigens (EBNAs), three latent membrane proteins (LMP), and untranslated RNA called EBV encoded RNA (EBER), shown to efficiently transform B cells into lymphoblastic cells. These programs undergo different patterns of expression which determine the occurrence of distinct types of latency in the pathogenesis of a particular tumor. Hematopoietic cell derived tumors include but not limited to Burkitt's lymphoma, Hodgkin lymphoma, post-transplant lymphoproliferative disorders, and natural killer (NK)/T cell lymphoma. EBV undergoes lytic infection in epithelia cells for amplification of the viral particle for transmission where it expresses lytic stage genes. However, for reasons yet to be unveiled, EBV switches from the expression of lytic stage genes to the expression of ETPs in epithelia cells. The expression of the ETPs lead to the transformation of epithelia cells into permanently proliferating cells, resulting in epithelia cell derived malignancies such as nasopharyngeal cancer, gastric cancer, and breast cancer. In this review, we have summarized the current updates on EBV associated epithelial and B cell-derived malignancies, and the role of EBV latency gene products in the pathogenesis of the cancers, and have suggested areas for future studies when considering therapeutic measures.

Immunoglobulin heavy variable (IgHV) gene mutation and micro-RNA expression in Burkitt's lymphoma at Moi Teaching and Referral Hospital in Western Kenya

INTRODUCTION

Burkitt's lymphoma (BL) is a virus associated childhood B-cell cancer common in Eastern Africa. Continued survival of B-cells in germinal centres depend on expression of high affinity immunoglobulins (Ig) to complementary antigens by somatic hypermutation of Ig genes. Cellular microRNAs, non-coding RNAs have been reported to play role in cell cycle regulation. Both viral antigen dependent mutation and micro-RNA expression maybe involved in BL pathogenesis.

OBJECTIVE

To describe immunoglobulin heavy variable (IgHV) rearrangement and micro-RNA expressions in BL tumours.

METHODS

Genomic DNA were extracted and purified from BL tissue blocks at Moi Teaching and Referral Hospital, before amplification using IgHV consensus primers and sequencing. The sequences were then aligned with germline alleles in IMGT/V-QUEST® database. Total RNA extracted from tissue blocks and cell lines were used to determine relative expression of hsamiR-34a and hsa-miR-127.

RESULTS

In all tumours, allele alignment scores and number of mutations range were 89.2-93.2%, 15-24 respectively. The range of IgHV amino acid changes were higher in EBER-1+ (15-25) than EBER-1- (9-15). In MYC+ tumours, the relative expression were: hsa-miR-127(2.09);hsa-miR-34a (2.8) and MYC- hsa-miR-127 (1.2), hsa-miR-34a (1.0).

CONCLUSION

B-cell in BL contained somatic mutated IgHV gene and upregulated cellular microRNAs with possible pathogenetic role(s).

Cytokines associated with Burkitt's lymphoma in western Kenya

Objective

Burkitt’s lymphoma (BL) is a common aggressive non-Hodgkin’s lymphoma in East and Central Africa among children. Persistent infections with Epstein Barr virus or Plasmodium falciparum are associated with immune hyperstimulation. It is hypothesised that inadvertent cytokine responses to infections indirectly or directly influence B cell neoplastic transformation through c-myelocytomatosis (c-myc) gene translocation. We sought to describe cytokines in children and adolescents with BL. Participants were recruited from western Kenya with parental consent, diagnosis confirmed using histology and consensus panel of immunohistochemistry antibodies. T helper1/2/17A and transforming growth factor-β1 (TGF-β1) cytokines were estimated using cytometric bead array in plasma. Complete blood counts (CBC) were determined by Beckman Coulter^®.

Results

Out of 104 enrolled participants, 32% were confirmed BL and 68% grouped as non-BL. Mean (pg/ml) levels of cytokines in BL and non-BL were: interleukin (IL)-6 100.3 and 39.4 p = 0.152; IL-10 11.5 and 12.5 p = 0.363; IL-17A 17.8 and 64.9 p = 0.094 respectively. Expressions of interferon-γ, IL-2 and tumour necrosis factor-α were low and TGF-β1 undetectable in both groups. Mean CBC differed between the two groups before and after chemotherapy, WBC being significantly so. Interleukin-6, IL-17A and IL-10 responses to infections in the study area may be associated with pathogenesis and be potential therapeutic targets.

Functional roles of HIV-1 Tat protein in the nucleus

Human immunodeficiency virus-1 (HIV-1) Tat protein is one of the most important regulatory proteins for viral gene expression in the host cell and can modulate different cellular processes. In addition, Tat is secreted by the infected cell and can be internalized by neighboring cells; therefore, it affects both infected and uninfected cells. Tat can modulate cellular processes by interacting with different cellular structures and signaling pathways. In the nucleus, Tat might be localized either in the nucleoplasm or the nucleolus depending on its concentration. Here we review the distinct functions of Tat in the nucleoplasm and the nucleolus in connection with viral infection and HIV-induced oncogenesis.

Marsdenia tenacssima extract and its functional components inhibits proliferation and induces apoptosis of human Burkitt leukemia/lymphoma cells in vitro and in vivo

Burkitt lymphoma is a fast growing non-Hodgkin lymphoma that occurs primarily in young males. The causes of Burkitt lymphoma include chromosome rearrangement and virus infection, but accurate and complete reasons remain to be discovered. The available treatment for Burkitt lymphoma is chemotherapy and radiation therapy. It is a highly aggressive B-cell neoplasm with not all patients cured, in spite of current therapies. This study evaluated the effects of traditional Chinese medicine Marsdenia tenacssima (MTE) and its component compound Tenacigenoside A (TGTA) and 11α-O-benzoyl-12β-O-acetyltenacigenin B (TGTB) on human Burkitt lymphoma growth. It was observed that MTE, TGTA or TGTB inhibited cell growth and induced apoptosis of Burkitt lymphoma cells in culture. In lymphoma bearing NOD/SCID nude mice, both TGTA and TGTB inhibited tumor growth and improved animal survival. TGTA and TGTB significantly increased tumor cell apoptosis on lymphoma bearing mice, primarily through down-regulation of BCL2 and BCL-XL and up-regulation of BID.

MicroRNA and pediatric tumors: Future perspectives

A better understanding of pediatric tumor biology is needed to allow the development of less toxic and more efficient therapies, as well as to provide novel reliable biomarkers for diagnosis and risk stratification. The emerging role of microRNAs in controlling key pathways implicated in tumorigenesis makes their use in diagnostics a powerful novel tool for the early detection, risk assessment and prognosis, as well as for the development of innovative anticancer therapies. This perspective would be more urgent for the clinical management of pediatric cancer. In this review, we focus on the involvement of microRNAs in the biology of the main childhood tumors, describe their clinical significance and discuss their potential use as novel therapeutic tools and targets.

[Effect of ERK1/2 inhibitor AZD8330 on human Burkitt's lymphoma cell line Raji cells and its mechanism]

目的

探讨细胞外信号调节激酶1/2（ERK1/2）抑制剂AZD8330对Burkitt淋巴瘤细胞株Raji细胞的作用及其机制。

方法

Raji细胞用不同浓度的AZD8330进行处理；采用CCK-8检测细胞存活率；流式细胞术检测细胞凋亡情况；实时定量PCR法检测Bcl-2、Bcl-xl、caspase-3和血管内皮生长因子(VEGF）mRNA表达；Western blot法检测Bcl-2、Bcl-xl、caspase-3、磷酸化(p)-ERK1/2蛋白表达。

结果

1.00 µmol/L的AZD8330处理24、48和72 h后细胞存活率分别为(62.09±0.86）%、(50.06±1.33）%和(39.13±2.34）%，差异有统计学意义（P值均<0.05）；0.10、1.00、10.00 µmol/L的AZD8330分别处理Raji细胞24、48和72 h，Raji细胞发生凋亡，凋亡率呈时间和剂量依赖性，差异有统计学意义（P值均<0.05）；随着浓度增加和时间延长，Bcl-2、Bcl-xl、VEGF mRNA表达降低，caspase-3 mRNA表达升高，差异有统计学意义（P值均<0.05）；同时，Bcl-2、Bcl-xl、p-ERK1/2蛋白表达明显受抑制，而caspase-3蛋白表达增强。

结论

AZD8330可能通过抑制ERK1/2通路相关基因和蛋白的表达而诱导Burkitt淋巴瘤Raji细胞凋亡，抑制其增殖。

Inhibition of methyltransferases accelerates degradation of cFLIP and sensitizes B-cell lymphoma cells to TRAIL-induced apoptosis

Non-Hodgkin lymphomas (NHLs) are characterized by specific abnormalities that alter cell cycle regulation, DNA damage response, and apoptotic signaling. It is believed that cancer cells are particularly sensitive to cell death induced by tumor necrosis factor α–related apoptosis-inducing ligand (TRAIL). However, many cancer cells show blocked TRAIL signaling due to up-regulated expression of anti-apoptotic factors, such as cFLIP. This hurdle to TRAIL’s tumor cytotoxicity might be overcome by combining TRAIL-based therapy with drugs that reverse blockages of its apoptotic signaling. In this study, we investigated the impact of a pan-methyltransferase inhibitor (3-deazaneplanocin A, or DZNep) on TRAIL-induced apoptosis in aggressive B-cell NHLs: mantle cell, Burkitt, and diffuse large B-cell lymphomas. We characterized TRAIL apoptosis regulation and caspase activation in several NHL-derived cell lines pre-treated with DZNep. We found that DZNep increased cancer cell sensitivity to TRAIL signaling by promoting caspase-8 processing through accelerated cFLIP degradation. No change in cFLIP mRNA level indicated independence of promoter methylation alterations in methyltransferase activity induced by DZNep profoundly affected cFLIP mRNA stability and protein stability. This appears to be in part through increased levels of cFLIP-targeting microRNAs (miR-512-3p and miR-346). However, additional microRNAs and cFLIP-regulating mechanisms appear to be involved in DZNep-mediated enhanced response to extrinsic apoptotic stimuli. The capacity of DZNep to target cFLIP expression on multiple levels underscores DZNep’s potential in TRAIL-based therapies for B-cell NHLs.

Disruption of HLA class II antigen presentation in Burkitt lymphoma: implication of a 47,000 MW acid labile protein in CD4+ T-cell recognition

While Burkitt lymphoma (BL) has a well-known defect in HLA class I-mediated antigen presentation, the exact role of BL-associated HLA class II in generating a poor CD4(+) T-cell response remains unresolved. Here, we found that BL cells are deficient in their ability to optimally stimulate CD4(+) T cells via the HLA class II pathway. This defect in CD4(+) T-cell recognition was not associated with low levels of co-stimulatory molecules on BL cells, as addition of external co-stimulation failed to elicit CD4(+) T-cell activation by BL. Further, the defect was not caused by faulty antigen/class II interaction, because antigenic peptides bound with measurable affinity to BL-associated class II molecules. Interestingly, functional class II-peptide complexes were formed at acidic pH 5·5, which restored immune recognition. Acidic buffer (pH 5·5) eluate from BL cells contained molecules that impaired class II-mediated antigen presentation and CD4(+) T-cell recognition. Biochemical analysis showed that these molecules were greater than 30,000 molecular weight in size, and proteinaceous in nature. In addition, BL was found to have decreased expression of a 47,000 molecular weight enolase-like molecule that enhances class II-mediated antigen presentation in B cells, macrophages and dendritic cells, but not in BL cells. These findings demonstrate that BL likely has multiple defects in HLA class II-mediated antigen presentation and immune recognition, which may be exploited for future immunotherapies.

Epstein-Barr virus (EBV) association and latency profile in pediatric Burkitt's lymphoma: experience of a single institution in Argentina

The aim of this study is to characterize EBV expression and latency pattern in pediatric Burkitt's lymphoma in a single institution in Argentina. EBV-encoded RNA or protein was analyzed in 27 patients. EBERs was expressed in 37% of patients (29% of immunocompetent and 100% of immunosuppressed patients). EBV-positive cases were observed exclusively in patients younger than 5 years old. EBV association with immunocompetent patients exhibits the sporadic pattern in region under study, while its presence in patients infected with HIV was higher than described previously. EBV latency I profile was present in most of the patients, except for two immunosuppressed patients who displayed LMP1 expression.

Burkitt's Lymphoma in a Pregnant Woman: Case Report and Review of the Literature

Burkitt's lymphoma (BL) is an aggressive B-cell malignancy with very high proliferation rate, more common in males than females. Here, we describe a case of Burkitt's lymphoma in a 24-week pregnant woman with cervical and abdominal involvement. The common genetic event of virtually all BL is a reciprocal chromosomal translocation involving the proto-oncogene MYC and one of the Ig gene heavy or light chain loci. Supportive treatment was administered until early delivery, after which the patient was treated according to protocol LMB96. Pregnancy and tumorogenesis share some important events such as immunologic tolerance, angiogenesis, and editing the host immune response. Little is known about the relationship between these events in pregnancy and in tumorogenesis.

Burkitt lymphoma arising from lymphoplasmacytic lymphoma following acquisition of MYC translocation and loss of the ETV6 tumor suppressor gene

Lymphoplasmacytic lymphoma is a mature B-cell lymphoma with variable plasmacytic differentiation that displays an indolent clinical course. Its transformation to a high-grade B-cell lymphoma may occur uncommonly. Although acquisition of a MYC translocation could result in transformation of a low-grade lymphoma into diffuse large B-cell lymphoma, Burkitt lymphoma, or B-lymphoblastic leukemia, to our knowledge the latter 2 transformations have not been well documented in lymphoplasmacytic lymphoma. We report the case of a 70-year-old woman with a 9-year history of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia who presented with rapid enlargement of a left neck mass and pancytopenia, which was diagnosed as Burkitt lymphoma with extensive bone marrow involvement. A series of histopathologic, molecular, and cytogenetic evaluations proved a cytogenetic evolution including t(8;14)(q24;q32)/MYC-IgH and identical clonal B-cell gene rearrangements from the 2 distinct lymphomas, confirming stage 4 aggressive Burkitt lymphoma arising from lymphoplasmacytic lymphoma.

EBV primary infection in childhood and its relation to B-cell lymphoma development: a mini-review from a developing region

In most underdeveloped countries, the initial contact with Epstein Barr virus (EBV) usually happens in the first decade of life and results in an asymptomatic infection, whereas in developed areas, primary infection in adolescence or adulthood is accompanied by infectious mononucleosis in 50% cases. Although it is generally a harmless passenger, in some individuals, it is associated with B-cell lymphoma. In Argentina, EBV primary infection shows the classical pattern observed in developing populations, given that nearly 70% of patients are seropositive by the age of 2 years. However, EBV association with pediatric Hodgkin and Burkitt lymphoma resembles that observed in developed regions. Concerning diffuse large B-cell lymphoma, our series demonstrated higher EBV association than other adult ones from either developed or underdeveloped countries. Interestingly, the early EBV primary infection observed, characteristic of an underdeveloped population, together with the statistically significant EBV association with patients ≤ 10 years old demonstrated in all types of lymphoma studied, suggest a relationship between low age of EBV seroconversion and B-cell lymphoma development risk.

Down-regulation of the PI3K/Akt signaling pathway and induction of apoptosis in CA46 Burkitt lymphoma cells by baicalin

Background

Baicalin, a flavone present in Scutellaria baicalensis Georgi, inhibits the growth of human leukemia and myeloma cells through induction of apoptosis.

Methods

The present study was undertaken to ascertain whether cultured Burkitt lymphoma cells undergo apoptosis when treated with baicalin. Growth rates were measured using MTT and colony formation assays, and induction of apoptosis was quantified using Annexin V and DNA fragmentation assays. Mechanisms underlying observed growth suppression were examined using Western blotting.

Results

Treatment of CA46 Burkitt lymphoma cells with baicalin for 48 h markedly decreased the rate of cell proliferation; an IC₅₀ value of 10 μM was obtained. Colony formation was almost fully suppressed at 10 μM baicalin. CA46 cells underwent apoptosis in response to baicalin treatment as evidenced by an increase in the percentage of cells stainable with Annexin V, by increased DNA fragmentation, and by activation of the intrinsic (mitochondrial) pathway for cell death as characterized by increased expression of the cleaved forms of caspase-9, caspase-3, and poly (ADP-ribose) polymerase. Additionally, baicalin was found to down-regulate anti-apoptotic and up-regulate apoptotic components of the phosphatidylinositide-3-kinase (PI3K)/serine/threonine kinase (Akt) signaling pathway.

Conclusions

The concentrations at which baicalin altered expression of components of the PI3K/Akt pathway in CA46 cells were comparable to those that suppressed growth and induced apoptosis, supporting the hypothesis that the observed growth-inhibitory and apoptosis-inducing actions of baicalin in these cells are mediated by down-regulation of this pathway.

Deep sequencing of MYC DNA-binding sites in Burkitt lymphoma

Background

MYC is a key transcription factor involved in central cellular processes such as regulation of the cell cycle, histone acetylation and ribosomal biogenesis. It is overexpressed in the majority of human tumors including aggressive B-cell lymphoma. Especially Burkitt lymphoma (BL) is a highlight example for MYC overexpression due to a chromosomal translocation involving the c-MYC gene. However, no genome-wide analysis of MYC-binding sites by chromatin immunoprecipitation (ChIP) followed by next generation sequencing (ChIP-Seq) has been conducted in BL so far.

Methodology/Principal Findings

ChIP-Seq was performed on 5 BL cell lines with a MYC-specific antibody giving rise to 7,054 MYC-binding sites after bioinformatics analysis of a total of approx. 19 million sequence reads. In line with previous findings, binding sites accumulate in gene sets known to be involved in the cell cycle, ribosomal biogenesis, histone acetyltransferase and methyltransferase complexes demonstrating a regulatory role of MYC in these processes. Unexpectedly, MYC-binding sites also accumulate in many B-cell relevant genes. To assess the functional consequences of MYC binding, the ChIP-Seq data were supplemented with siRNA- mediated knock-downs of MYC in BL cell lines followed by gene expression profiling. Interestingly, amongst others, genes involved in the B-cell function were up-regulated in response to MYC silencing.

Conclusion/Significance

The 7,054 MYC-binding sites identified by our ChIP-Seq approach greatly extend the knowledge regarding MYC binding in BL and shed further light on the enormous complexity of the MYC regulatory network. Especially our observations that (i) many B-cell relevant genes are targeted by MYC and (ii) that MYC down-regulation leads to an up-regulation of B-cell genes highlight an interesting aspect of BL biology.

Mechanisms regulating enhanced human leukocyte antigen class II-mediated CD4 + T cell recognition of human B-cell lymphoma by resveratrol

Malignant B-cells express measurable levels of human leukocyte antigen (HLA) class II proteins, but often escape immune recognition by CD4 + T cells. Resveratrol (Resv) has been the focus of numerous investigations due to its potential chemopreventive and anti-cancer effects, but it has never been tested in the regulation of immune components in B-cell tumors. Here, we show for the first time that Resv treatment enhances HLA class II-mediated immune detection of B-cell lymphomas by altering immune components and class II presentation in tumor cells. Resv treatment induced an up-regulation of both classical and non-classical HLA class II proteins (DR and DM) in B-lymphoma cells. Resv also altered endolysosomal cathepsins (Cat S, B and D) and a thiol reductase (GILT), increasing HLA class II-mediated antigen (Ag) processing in B-cell lymphomas and their subsequent recognition by CD4 + T cells. Mechanistic study demonstrated that Resv treatment activated the recycling class II pathway of Ag presentation through up-regulation of Rab 4B protein expression in B-lymphoma cells. These findings suggest that HLA class II-mediated immune recognition of malignant B-cells can be improved by Resv treatment, thus encouraging its potential use in chemoimmunotherapy of B-cell lymphoma.

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.

Sporadic Burkitt lymphoma in southern China: 12 years' experience in a single institution in Guangzhou

Aim

To analyse the clinicopathological features of sporadic Burkitt lymphoma (sBL).

Methods

In a review of 1682 cases of non-Hodgkin lymphoma diagnosed in the First Affiliated Hospital and Zhongshan School of Medicine, from 1998 to 2010, 20 cases (1.2%) of sBL were identified. Histopathological examination, immunohistochemistry and in situ hybridisation were used to analyse the clinicopathological features of these cases.

Results

Of the 20 cases of sBL, 18 patients were male and two were female. The mean age was 18 years (range 2–67 years). Extranodal presentation was more common than nodal presentation (55% vs 15%). Histopathologically, 18 cases (90%) showed monotonous medium-sized tumour cells, and two cases showed cells that were slightly pleomorphic in nuclear size and shape. Immunophenotypically, MUM1 was positive in three of 17 cases (17.6%). EBER expression was shown in five of 17 cases (29.4%), and all EBER-positive sBLs were Bcl-6+/MUM1−.

Conclusion

sBL is rare and mainly affects male children, with predominantly extranodal presentation. MUM1 expression was found in some sBLs. EBER expression was found in 29.4% of sBLs from southern China, an area with a well-known high incidence of nasopharyngeal carcinoma, which is closely associated with Epstein–Barr virus infection.