Lymphoma- and leukemia-associated chromosomal translocations in healthy individuals

Effect of Diet and Oxidative Stress in the Pathogenesis of Lymphoproliferative Disorders

Lymphomas are a heterogeneous group of pathologies that result from clonal proliferation of lymphocytes. They are classified into Hodgkin lymphoma and non-Hodgkin lymphoma; the latter develops as a result of B, T, or NK cells undergoing malignant transformation. It is believed that diet can modulate cellular redox state and that oxidative stress is implicated in lymphomagenesis by acting on several biological mechanisms; in fact, oxidative stress can generate a state of chronic inflammation through the activation of various transcription factors, thereby increasing the production of proinflammatory cytokines and causing overstimulation of B lymphocytes in the production of antibodies and possible alterations in cellular DNA. The purpose of our work is to investigate the results of in vitro and in vivo studies on the possible interaction between lymphomas, oxidative stress, and diet. A variety of dietary regimens and substances introduced with the diet that may have antioxidant and antiproliferative effects were assessed. The possibility of using nutraceuticals as novel anticancer agents is discussed; although the use of natural substances in lymphoma therapy is an interesting field of study, further studies are needed to define the efficacy of different nutraceuticals before introducing them into clinical practice.

Oxidative Stress and Inflammation in B-Cell Lymphomas

Mature lymphoid neoplasms arise de novo or by the transformation of more indolent lymphomas in a process that relies on the stepwise accumulation of genomic and transcriptomic alterations. The microenvironment and neoplastic precursor cells are heavily influenced by pro-inflammatory signaling, regulated in part by oxidative stress and inflammation. Reactive oxygen species (ROSs) are by-products of cellular metabolism able to modulate cell signaling and fate. Moreover, they play a crucial role in the phagocyte system, which is responsible for antigen presentation and the selection of mature B and T cells under normal conditions. Imbalances in pro-oxidant and antioxidant signaling can lead to physiological dysfunction and disease development by disrupting metabolic processes and cell signaling. This narrative review aims to analyze the impact of reactive oxygen species on lymphomagenesis, specifically examining the regulation of microenvironmental players, as well as the response to therapy for B-cell-derived non-Hodgkin lymphomas. Further research is needed to investigate the involvement of ROS and inflammation in the development of lymphomas, which may unravel disease mechanisms and identify innovative therapeutic targets.

RNA-driven JAZF1-SUZ12 gene fusion in human endometrial stromal cells

Oncogenic fusion genes as the result of chromosomal rearrangements are important for understanding genome instability in cancer cells and developing useful cancer therapies. To date, the mechanisms that create such oncogenic fusion genes are poorly understood. Previously we reported an unappreciated RNA-driven mechanism in human prostate cells in which the expression of chimeric RNA induces specified gene fusions in a sequence-dependent manner. One fundamental question yet to be addressed is whether such RNA-driven gene fusion mechanism is generalizable, or rather, a special case restricted to prostate cells. In this report, we demonstrated that the expression of designed chimeric RNAs in human endometrial stromal cells leads to the formation of JAZF1-SUZ12, a cancer fusion gene commonly found in low-grade endometrial stromal sarcomas. The process is specified by the sequence of chimeric RNA involved and inhibited by estrogen or progesterone. Furthermore, it is the antisense rather than sense chimeric RNAs that effectively drive JAZF1-SUZ12 gene fusion. The induced fusion gene is validated both at the RNA and the genomic DNA level. The ability of designed chimeric RNAs to drive and recapitulate the formation of JAZF1-SUZ12 gene fusion in endometrial cells represents another independent case of RNA-driven gene fusion, suggesting that RNA-driven genomic recombination is a permissible mechanism in mammalian cells. The results could have fundamental implications in the role of RNA in genome stability, and provide important insight in early disease mechanisms related to the formation of cancer fusion genes.

Fusion genes resulting from chromosomal translocations are important for understanding cancer mechanisms and developing anti-cancer therapies. Fusion gene are presumed to occur prior to fusion RNA expression. However, studies have reported the presence of fusion RNAs in individuals who were negative for chromosomal translocations. The observation, that fusion RNA could be present prior to fusion gene formation, raises the provocative hypothesis that fusion RNA, or any cellular RNA with sequence compositions resembling that of fusion RNA, could act as a template to mediate genomic rearrangement which leads to the final gene fusion. In this report, we demonstrated that the expression of designed chimeric RNAs in human endometrial stromal cells leads to the formation of JAZF1-SUZ12, a cancer fusion gene found in endometrial stromal sarcomas. The process is specified by the sequence of chimeric RNA involved and inhibited by estrogen or progesterone. Furthermore, it is the antisense rather than sense chimeric RNAs that effectively drive JAZF1-SUZ12 gene fusion. The results could have fundamental implications in the role of RNA in mammalian genome stability, provide important insight in early disease mechanism, as well as developing gene editing technology via mechanisms native to mammalian cells.

Unexpected suppression of tumorigenesis by c-MYC via TFAP4-dependent restriction of stemness in B lymphocytes

The proliferative burst of B lymphocytes is essential for antigen receptor repertoire diversification during the development and selective expansion of antigen-specific clones during immune responses. High proliferative activity inevitably promotes oncogenesis, the risk of which is further elevated in B lymphocytes by endogenous gene rearrangement and somatic mutations. However, B-cell-derived cancers are rare, perhaps owing to putative intrinsic tumor-suppressive mechanisms. We show that c-MYC facilitates B-cell proliferation as a protumorigenic driver and unexpectedly coengages counteracting tumor suppression through its downstream factor TFAP4. TFAP4 is mutated in human lymphoid malignancies, particularly in >10% of Burkitt lymphomas, and reduced TFAP4 expression was associated with poor survival of patients with MYC-high B-cell acute lymphoblastic leukemia. In mice, insufficient TFAP4 expression accelerated c-MYC-driven transformation of B cells. Mechanistically, c-MYC suppresses the stemness of developing B cells by inducing TFAP4 and restricting self-renewal of proliferating B cells. Thus, the pursuant transcription factor cascade functions as a tumor suppressor module that safeguards against the transformation of developing B cells.

The role of PLCγ2 in immunological disorders, cancer, and neurodegeneration

Phosphatidylinositol-specific phospholipase Cγ2 (PLCγ2) is a critical signaling molecule activated downstream from a variety of cell surface receptors that contain an intracellular immunoreceptor tyrosine-based activation motif. These receptors recruit kinases such as Syk, BTK, and BLNK to phosphorylate and activate PLCγ2, which then generates 1D-myo-inositol 1,4,5-trisphosphate and diacylglycerol. These well-known second messengers are required for diverse membrane functionality including cellular proliferation, endocytosis, and calcium flux. As a result, PLCγ2 dysfunction is associated with a variety of diseases including cancer, neurodegeneration, and immune disorders. The diverse pathologies associated with PLCγ2 are exemplified by distinct genetic variants. Inherited mutations at this locus cause PLCγ2-associated antibody deficiency and immune dysregulation, in some cases with autoinflammation. Acquired mutations at this locus, which often arise as a result of BTK inhibition to treat chronic lymphocytic leukemia, result in constitutive downstream signaling and lymphocyte proliferation. Finally, a third group of PLCγ2 variants actually has a protective effect in a variety of neurodegenerative disorders, presumably by increased uptake and degradation of deleterious neurological aggregates. Therefore, manipulating PLCγ2 activity either up or down could have therapeutic benefit; however, we require a better understanding of the signaling pathways propagated by these variants before such clinical utility can be realized. Here, we review the signaling roles of PLCγ2 in hematopoietic cells to help understand the effect of mutations driving immune disorders and cancer and extrapolate from this to roles which may relate to protection against neurodegeneration.

Novel Biological Insights and New Developments in Management of Burkitt Lymphoma and High-Grade B-Cell Lymphoma

OPINION STATEMENT

Burkitt lymphoma (BL) is highly curable, and prompt institution of therapy is critical to achieving optimal outcomes. Although current "standard" approaches are very effective in disease eradication, treatment-related toxicity makes optimal delivery of curative therapy a challenge, especially in older and immunocompromised individuals. Reduced intensity approaches with fewer toxic complications have been the focus of some recent studies. A critical question is if they can replace "standard" approaches by maintaining high curability with improved tolerability. Additionally, new molecular insights in BL biology suggest that in the future, "targeted therapy" approaches may be feasible using small molecule inhibitors and novel strategies. Recently, a new category of aggressive lymphoma named "high-grade B-cell lymphoma (HGBL) with MYC and BCL2 and/or BCL6 translocations" has been recognized. This category overlaps clinically and biologically with BL and has an inferior prognosis compared to most B-cell lymphomas, and the optimal approach to its management remains, as yet, undefined. In this review, we discuss the current landscape of BL treatment including recent results with low-intensity regimens and also consider current approaches to HGBL. We also explore how recently elucidated novel biological insights in BL biology may shape future therapeutic directions including the use of novel cellular therapy approaches.

Non-fusion mutations in endometrial stromal sarcomas: what is the potential impact on tumourigenesis through cell cycle dysregulation?

Targeted next-generation sequencing using the 50-gene Ion AmpliSeq Cancer Hotspot Panel v2 identified two significant point mutations in endometrial stromal sarcomas (ESS). Case 1 is a uterine mass from a quadragenarian woman with a karyotype lacking any known ESS rearrangements but demonstrated to have a CTNNB1-activating mutation (c.133T>C, p.[Ser45Pro]). Analysis of a uterine mass from case 2, a sexagenarian woman, revealed biallelic CDKN2A-inactivating mutations (c.172C>T, p.[Arg58Ter] and a deletion). Break-apart studies to identify YWHAE, JAZF1 and PHF1 rearrangements were negative in both tumours. We propose a model in which these point mutations may affect cell proliferation, converging at Wnt signalling and G1-S checkpoint control, that independently or in concert with a rare gene fusion result in ESS tumour development or progression.

Indolent In Situ B-Cell Neoplasms With MYC Rearrangements Show Somatic Mutations in MYC and TNFRSF14 by Next-generation Sequencing

Systemic high-grade B-cell lymphomas (HGBCLs) with MYC gene rearrangements are clinically aggressive. In situ lesions with indolent behavior have not been described to date. We have identified 2 cases of in situ B-cell neoplasms with MYC rearrangements (IS-BCN, MYC) occurring, and focally confined to ≤4 lymphoid follicles in otherwise healthy individuals and without clinical progression despite minimal intervention (surgical only). Morphologically similar to systemic HGBCLs, the low power view of these lesions showed a starry sky pattern with numerous mitotic figures. High power imaging demonstrated these cells to be medium-large in size with irregular nuclear contours, immature chromatin, and prominent nucleoli. Immunophenotypically these cells were light chain restricted, positive for CD20, CD10, c-Myc, and dim or negative for BCL2 with a Ki67 proliferative index of >95%. By fluorescence in situ hybridization studies, we detected MYC translocations in these cells but no rearrangements in BCL2 or BCL6. Microdissection of neoplastic cells in these patients followed by targeted next-generation sequencing identified a mutation in MYC, D2N, and an indel in TNFRSF14. Mutations in ID3 or TCF3 were not identified. Although rare, these lesions should be separated from HGBCLs involving follicles but with systemic spread which has been previously described. Unlike systemic lymphomas with MYC gene rearrangements, these in situ B-cell neoplasms with MYC rearrangements did not require systemic therapy and no progression has been seen in either patient beyond 1 year (29 and 16 mo). Our work offers pathologic and biologic insight into the early process of B-cell neoplasia.

BCR: a promiscuous fusion partner in hematopoietic disorders

Considerable advances have been made in our understanding of the molecular basis of hematopoietic cancers. The discovery of the BCR-ABL fusion protein over 50 years ago has brought about a new era of therapeutic progress and overall improvement in patient care, mainly due to the development and use of personalized medicine and tyrosine kinase inhibitors (TKIs). However, since the detection of BCR-ABL, BCR has been identified as a commonly occurring fusion partner in hematopoietic disorders. BCR has been discovered fused to additional tyrosine kinases, including: Fibroblast Growth Factor Receptor 1 (FGFR1), Platelet-derived Growth Factor Receptor Alpha (PDGFRA), Ret Proto-Oncogene (RET), and Janus Kinase 2 (JAK2). While BCR translocations are infrequent in hematopoietic malignancies, clinical evidence suggests that patients who harbor these mutations benefit from TKIs and additional personalized therapies. The improvement of further methodologies for characterization of these fusions is crucial to determine a patient’s treatment regimen, and optimal outcome. However, potential relapse and drug resistance among patients’ highlights the need for additional treatment options and further understanding of these oncogenic fusion proteins. This review explores the mechanisms behind cancer progression of these BCR oncogenic fusion proteins, comparing their similarities and differences, examining the significance of BCR as a partner gene, and discussing current treatment options for these translocation-induced hematopoietic malignancies.

RNA-mediated gene fusion in mammalian cells

One of the hallmarks of cancer is the formation of oncogenic fusion genes as a result of chromosomal translocations. Fusion genes are presumed to form before fusion RNA expression. However, studies have reported the presence of fusion RNAs in individuals who were negative for chromosomal translocations. These observations give rise to "the cart before the horse" hypothesis, in which the genesis of a fusion RNA precedes the fusion gene. The fusion RNA then guides the genomic rearrangements that ultimately result in a gene fusion. However, RNA-mediated genomic rearrangements in mammalian cells have never been demonstrated. Here we provide evidence that expression of a chimeric RNA drives formation of a specified gene fusion via genomic rearrangement in mammalian cells. The process is: (i) specified by the sequence of chimeric RNA involved, (ii) facilitated by physiological hormone levels, (iii) permissible regardless of intrachromosomal (TMPRSS2-ERG) or interchromosomal (TMPRSS2-ETV1) fusion, and (iv) can occur in normal cells before malignant transformation. We demonstrate that, contrary to "the cart before the horse" model, it is the antisense rather than sense chimeric RNAs that effectively drive gene fusion, and that this disparity can be explained by transcriptional conflict. Furthermore, we identified an endogenous RNA AZI1 that functions as the "initiator" RNA to induce TMPRSS2-ERG fusion. RNA-driven gene fusion demonstrated in this report provides important insight in early disease mechanisms, and could have fundamental implications in the biology of mammalian genome stability, as well as gene-editing technology via mechanisms native to mammalian cells.

Global stability analysis and optimal control therapy of blood cell production process (hematopoiesis) in acute myeloid leukemia

In this paper we analyze the global stability of a coupled model for Acute Myeloid Leukemia and propose a therapy approach based on an optimal control strategy. Firstly, based on the positivity of the model, stability of trivial solutions for healthy and cancerous cell subsystems is assessed. To this end we use new Lyapunov functionals and take into account the interconnection between cell populations. Secondly, stability conditions for healthy situation in interconnected model are established by using Nyquist criterion. And thirdly, we design an optimal control based therapy that aims to eradicate cancerous cells and minimize the side effects of the treatment on healthy ones. After showing the existence of an optimal control, this one is determined by using Pontriagyn's principal. We assess the effect of interconnection between healthy and cancerous cells on their dynamics and on the stability conditions for different cases. The behavior of the system in open loop and with application of the optimal control therapy is illustrated by simulation and results are biologically explained and motivated.

Study of cohabitation and interconnection effects on normal and leukaemic stem cells dynamics in acute myeloid leukaemia

On the basis of recent studies, understanding the intimate relationship between normal and leukaemic stem cells is very important in leukaemia treatment. The authors' aim in this work is to clarify and assess the effect of coexistence and interconnection phenomenon on the healthy and cancerous stem cell dynamics. To this end, they perform the analysis of two time-delayed stem cell models in acute myeloid leukaemia. The first model is based on decoupled healthy and cancerous stem cell populations (i.e. there is no interaction between cell dynamics) and the second model includes interconnection between both population's dynamics. By using the positivity of both systems, they build new linear functions that permit to derive global stability conditions for each model. Moreover, knowing that most common types of haematological diseases are characterised by the existence of oscillations, they give conditions for the existence of a limit cycle (oscillations) in a particularly interesting healthy situation based on Poincare-Bendixson theorem. The obtained results are simulated and interpreted to be significant in understanding the effect of interconnection and would lead to an improvement in leukaemia treatment.

Comprehensive Transcriptome and Mutational Profiling of Endemic Burkitt Lymphoma Reveals EBV Type-Specific Differences

Endemic Burkitt lymphoma (eBL) is the most common pediatric cancer in malaria-endemic equatorial Africa and nearly always contains Epstein-Barr virus (EBV), unlike sporadic Burkitt lymphoma (sBL) that occurs with a lower incidence in developed countries. Given these differences and the variable clinical presentation and outcomes, we sought to further understand pathogenesis by investigating transcriptomes using RNA sequencing (RNAseq) from multiple primary eBL tumors compared with sBL tumors. Within eBL tumors, minimal expression differences were found based on: anatomical presentation site, in-hospital survival rates, and EBV genome type, suggesting that eBL tumors are homogeneous without marked subtypes. The outstanding difference detected using surrogate variable analysis was the significantly decreased expression of key genes in the immunoproteasome complex (PSMB9/β1i, PSMB10/β2i, PSMB8/β5i, and PSME2/PA28β) in eBL tumors carrying type 2 EBV compared with type 1 EBV. Second, in comparison with previously published pediatric sBL specimens, the majority of the expression and pathway differences was related to the PTEN/PI3K/mTOR signaling pathway and was correlated most strongly with EBV status rather than geographic designation. Third, common mutations were observed significantly less frequently in eBL tumors harboring EBV type 1, with mutation frequencies similar between tumors with EBV type 2 and without EBV. In addition to the previously reported genes, a set of new genes mutated in BL, including TFAP4, MSH6, PRRC2C, BCL7A, FOXO1, PLCG2, PRKDC, RAD50, and RPRD2, were identified. Overall, these data establish that EBV, particularly EBV type 1, supports BL oncogenesis, alleviating the need for certain driver mutations in the human genome.

IMPLICATIONS

Genomic and mutational analyses of Burkitt lymphoma tumors identify key differences based on viral content and clinical outcomes suggesting new avenues for the development of prognostic molecular biomarkers and therapeutic interventions.

Shikonin exerts antitumor activity in Burkitt's lymphoma by inhibiting C-MYC and PI3K/AKT/mTOR pathway and acts synergistically with doxorubicin

Burkitt's lymphoma (BL) is a highly aggressive malignancy molecularly characterized by deregulation of the C-MYC proto-oncogene. Recently, it has been confirmed that phosphatidylinositol-3-kinase (PI3K) pathway activation is a crucial element in the malignant transformation of the B cells in BL. Despite the better outcome of adults with BL treated with high-intensity chemotherapy regimens, the overall survival rate for patients older than 60 years remains dismal. Shikonin, a natural naphthoquinone derived from Chinese herbal medicine plant, has the potential to induce cell death in a series of human cancer. In the present study, we investigated the effect and molecular mechanisms of Shikonin in treatment with BL. Shikonin suppressed cellular proliferation and induced caspase-dependent apoptosis in BL cells. Inhibition of C-MYC and suppression of PI3K/AKT/mTOR pathway played critical roles in SHK-induced apoptosis in BL both in vitro and in vivo. Besides, Shikonin potentiated doxorubicin-induced growth inhibition and apoptosis in vitro. Furthermore, the growth of a subcutaneous xenograft tumor model of BL was significantly inhibited by shikonin. Importantly, we did not find the effect of shikonin on liver function in mice. In summary, these data suggest that shikonin may be an encouraging chemotherapeutic agent in the clinical treatment of BL.

Feature analysis of cell nuclear chromatin distribution in support of cervical cytology

Cytology, a method of estimating cancer or cellular atypia from microscopic images of scraped specimens, is used according to the pathologist’s experience to diagnose cases based on the degree of structural changes and atypia. Several methods of cell feature quantification, including nuclear size, nuclear shape, cytoplasm size, and chromatin texture, have been studied. We focus on chromatin distribution in the cell nucleus and propose new feature values that indicate the chromatin complexity, spreading, and bias, including convex hull ratio on multiple binary images, intensity distribution from the gravity center, and tangential component intensity and texture biases. The characteristics and cellular classification accuracies of the proposed features were verified through experiments using cervical smear samples, for which clear nuclear morphologic diagnostic criteria are available. In this experiment, we also used a stepwise support vector machine to create a machine learning model and a cross-validation algorithm with which to derive identification accuracy. Our results demonstrate the effectiveness of our proposed feature values.

It Is Imperative to Establish a Pellucid Definition of Chimeric RNA and to Clear Up a Lot of Confusion in the Relevant Research

There have been tens of thousands of RNAs deposited in different databases that contain sequences of two genes and are coined chimeric RNAs, or chimeras. However, "chimeric RNA" has never been lucidly defined, partly because "gene" itself is still ill-defined and because the means of production for many RNAs is unclear. Since the number of putative chimeras is soaring, it is imperative to establish a pellucid definition for it, in order to differentiate chimeras from regular RNAs. Otherwise, not only will chimeric RNA studies be misled but also characterization of fusion genes and unannotated genes will be hindered. We propose that only those RNAs that are formed by joining two RNA transcripts together without a fusion gene as a genomic basis should be regarded as authentic chimeras, whereas those RNAs transcribed as, and cis-spliced from, single transcripts should not be deemed as chimeras. Many RNAs containing sequences of two neighboring genes may be transcribed via a readthrough mechanism, and thus are actually RNAs of unannotated genes or RNA variants of known genes, but not chimeras. In today's chimeric RNA research, there are still several key flaws, technical constraints and understudied tasks, which are also described in this perspective essay.

Absence of t(14;18) chromosome translocation in agricultural workers after short-term exposure to pesticides

Exposure to pesticides represents a potential health risk for the general population and for agricultural workers in particular. Some researchers observed that occupational exposure to pesticides is associated with risk of non‑Hodgkin's lymphoma (NHL). The chromosomal translocation t(14;18)(q32;q21) is one of the most common chromosomal abnormalities in NHL. The aim of this study was to detect the effects of pesticides on t(14;18) chromosome translocation in agricultural workers after short-term exposure. Fifty-two workers occupationally exposed to pesticides (fungicides and insecticides) and 52 non-exposed were recruited. The farm workers were on average exposed to pesticides for ~3.7 h a day for 5 years. The frequency of BCL2-IGH t(14;18) translocation in workers occupationally exposed to pesticides was 10% (5 of 52) vs. 8% (4 of 52) in the control group. Overall, these data suggest that no significant association between occupational exposure to pesticides and an increased frequency of the chromosomal translocation BCL2-IGH t(14;18) in farmers was observed. However, further studies with a higher number of subjects exposed to pesticides are necessary to confirm this observation.

Speculations on the clinical significance of asymptomatic viral infections

A detailed understanding of asymptomatic chronic viral infections is critical to analyse their pathogenesis, assess the severity and burden of disease and, where required, optimize public health control measures. Recent studies on herpesviruses showed that the host-virus interactions are modulated by co-infections, emphasizing the relevance of co-infections in determining the clinical expression (from asymptomatic to symptomatic infections) and the severity of herpesvirus-associated diseases (either neoplastic or infectious diseases). To demonstrate causality between viruses (virome) and diseases, Koch's postulates should be adapted adding new knowledge on host-microbe relationship and microbial interactions. In the present review we aim to provide an update on asymptomatic chronic infections and criteria for causality and on the virological, immunological and host-virus interactions in asymptomatic chronic infections in human hosts, focusing on herpetic infections.

Occupational exposure to pesticides and occurrence of the chromosomal translocation t(14;18) among farmers in Jordan

BACKGROUND

An increased incidence of non-Hodgkin's lymphoma (NHL) has been reported in farmers and other occupational groups working with pesticides. In these individuals, an increased prevalence of the chromosomal translocation t(14;18)(q32;q21), one of the most common chromosomal abnormalities in NHL, has been detected in peripheral blood lymphocytes. This translocation juxtaposes the antiapoptotic BCL2 protein to the immunoglobulin heavy chain gene locus (IGH) leading to overexpression of BCL2. This causes an increase in cell survival, paving the way for malignant transformation.

AIM OF THE STUDY

The present study aimed to evaluate the association between the occurrence of the chromosomal translocation t(14;18) and occupational exposure to pesticides among a group of Jordanian farmers.

METHODS

A total of 192 male subjects including 96 agricultural workers and 96 control subjects participated in this study. BCL2-IGH t(14;18) fusions were detected by a nested polymerase chain reaction (PCR) assay targeting the major breakpoint region (MBR).

RESULTS

We found that occupational exposure to pesticides in open-field farming and insecticide used on animals increased the frequency of the chromosomal translocation t(14;18). Farmers occupationally exposed to pesticides and insecticide were 13.5 times more likely to harbor t(14;18). 63.5% (61 of 96) of farmers compared to 11.5% (11 of 96) of controls carried the translocation (odds ratio: 13.5; 95% confidence interval (CI) = 6.3-28.6). We ruled out the influence of possible confounding factors such as age, duration of sun exposure, alcohol intake, smoking, and use of personal protective equipment.

CONCLUSION

Our results indicate that pesticides increased the frequency of chromosomal translocation in the 14q32 region. Accordingly, the presented data agrees with previous suggestions from the literature that pesticides might be involved in the development of NHL through the t(14;18) pathway.

Plasmablastic Lymphoma: A Review of Current Knowledge and Future Directions

Plasmablastic lymphoma (PBL) is an aggressive subtype of non-Hodgkin's lymphoma (NHL), which frequently arises in the oral cavity of human immunodeficiency virus (HIV) infected patients. PBL shows diffuse proliferation of large neoplastic cells resembling B-immunoblasts/plasmablasts, or with plasmacytic features and an immunophenotype of plasma cells. PBL remains a diagnostic challenge due to its peculiar morphology and an immunohistochemical profile similar to plasma cell myeloma (PCM). PBL is also a therapeutic challenge with a clinical course characterized by a high rate of relapse and death. There is no standard chemotherapy protocol for treatment of PBL. Cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP-like regimens have been the backbone while more intensive regimens such as cyclophosphamide, vincristine, doxorubicin, high-dose methotrexate/ifosfamide, etoposide, high-dose cytarabine (CODOX-M/IVAC), or dose-adjusted etoposide, prednisone, vincristine, cyclophosphamide, and doxorubicin (DA-EPOCH) are possible options. Recently, a few studies have reported the potential value of the proteasome inhibitor bortezomib and thalidomide in PBL patients. The introduction of genes encoding artificial receptors called chimeric antigen receptors (CARs) and CAR-modified T cells targeted to the B cell-specific CD19 antigen have demonstrated promising results in multiple early clinical trials. The aim of this paper is to review the recent advances in epidemiology; pathophysiology; clinical, pathologic, and molecular characteristics; therapy; and outcome in patients with PBL.

Plasmodium Infection Promotes Genomic Instability and AID-Dependent B Cell Lymphoma

Chronic infection with Plasmodium falciparum was epidemiologically associated with endemic Burkitt's lymphoma, a mature B cell cancer characterized by chromosome translocation between the c-myc oncogene and Igh, over 50 years ago. Whether infection promotes B cell lymphoma, and if so by which mechanism, remains unknown. To investigate the relationship between parasitic disease and lymphomagenesis, we used Plasmodium chabaudi (Pc) to produce chronic malaria infection in mice. Pc induces prolonged expansion of germinal centers (GCs), unique compartments in which B cells undergo rapid clonal expansion and express activation-induced cytidine deaminase (AID), a DNA mutator. GC B cells elicited during Pc infection suffer widespread DNA damage, leading to chromosome translocations. Although infection does not change the overall rate, it modifies lymphomagenesis to favor mature B cell lymphomas that are AID dependent and show chromosome translocations. Thus, malaria infection favors mature B cell cancers by eliciting protracted AID expression in GC B cells. PAPERCLIP.

Hypothesis: Artifacts, Including Spurious Chimeric RNAs with a Short Homologous Sequence, Caused by Consecutive Reverse Transcriptions and Endogenous Random Primers

Recent RNA-sequencing technology and associated bioinformatics have led to identification of tens of thousands of putative human chimeric RNAs, i.e. RNAs containing sequences from two different genes, most of which are derived from neighboring genes on the same chromosome. In this essay, we redefine "two neighboring genes" as those producing individual transcripts, and point out two known mechanisms for chimeric RNA formation, i.e. transcription from a fusion gene or trans-splicing of two RNAs. By our definition, most putative RNA chimeras derived from canonically-defined neighboring genes may either be technical artifacts or be cis-splicing products of 5'- or 3'-extended RNA of either partner that is redefined herein as an unannotated gene, whereas trans-splicing events are rare in human cells. Therefore, most authentic chimeric RNAs result from fusion genes, about 1,000 of which have been identified hitherto. We propose a hypothesis of "consecutive reverse transcriptions (RTs)", i.e. another RT reaction following the previous one, for how most spurious chimeric RNAs, especially those containing a short homologous sequence, may be generated during RT, especially in RNA-sequencing wherein RNAs are fragmented. We also point out that RNA samples contain numerous RNA and DNA shreds that can serve as endogenous random primers for RT and ensuing polymerase chain reactions (PCR), creating artifacts in RT-PCR.

Early lymphoid lesions: conceptual, diagnostic and clinical challenges

There are no "benign lymphomas", a fact due to the nature of lymphoid cells to circulate and home as part of their normal function. Thus, benign clonal expansions of lymphocytes are only rarely recognized when localized. Recent studies have identified a number of lymphoid proliferations that lie at the interface between benign and malignant. Some of these are clonal proliferations that carry many of the molecular hallmarks of their malignant counterparts, such as BCL2/IGH and CCND1/IGH translocations associated with the in situ forms of follicular lymphoma and mantle cell lymphoma, respectively. There are other clonal B-cell proliferations with low risk of progression; these include the pediatric variants of follicular lymphoma and marginal zone lymphoma. Historically, early or incipient forms of T/NK-cell neoplasia also have been identified, such as lymphomatoid papulosis and refractory celiac disease. More recently an indolent form of T-cell lymphoproliferative disease affecting the gastrointestinal tract has been described. Usually, CD8(+), the clonal cells are confined to the mucosa. The clinical course is chronic, but non-progressive. NK-cell enteropathy is a clinically similar condition, composed of cytologically atypical NK-cells that may involve the stomach, small bowel or colon. Breast implant-associated anaplastic large cell lymphoma is a cytologically alarming lesion that is self-limited if confined to the seroma cavity. Atypical lymphoid proliferations that lie at the border of benign and malignant can serve as instructive models of lymphomagenesis. It is also critical that they be correctly diagnosed to avoid unnecessary and potentially harmful therapy.

Homology and enzymatic requirements of microhomology-dependent alternative end joining

Nonhomologous DNA end joining (NHEJ) is one of the major double-strand break (DSB) repair pathways in higher eukaryotes. Recently, it has been shown that alternative NHEJ (A-NHEJ) occurs in the absence of classical NHEJ and is implicated in chromosomal translocations leading to cancer. In the present study, we have developed a novel biochemical assay system utilizing DSBs flanked by varying lengths of microhomology to study microhomology-mediated alternative end joining (MMEJ). We show that MMEJ can operate in normal cells, when microhomology is present, irrespective of occurrence of robust classical NHEJ. Length of the microhomology determines the efficiency of MMEJ, 5 nt being obligatory. Using this biochemical approach, we show that products obtained are due to MMEJ, which is dependent on MRE11, NBS1, LIGASE III, XRCC1, FEN1 and PARP1. Thus, we define the enzymatic machinery and microhomology requirements of alternative NHEJ using a well-defined biochemical system.

Risk of follicular lymphoma associated with BCL2 translocations in peripheral blood

Many adults have circulating lymphocytes with the BCL2 gene translocation characteristic of follicular lymphoma. We therefore conducted a nested case-control study of incident lymphomas with peripheral blood obtained a median 4.9 years pre-diagnosis from the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. Overall, 13 of 26 cases of lymphoma and 14 of 47 controls had BCL2 major breakpoint region (MBR) translocations in pre-diagnosis blood (odds ratio [OR] = 2.8). Nine cases had BCL2-MBR-positive tumors; eight of these nine had BCL2-MBR translocations in paired blood versus five of the 17 with BCL2-MBR-negative tumors (p = 0.01). Comparing both tumor types to controls, blood BCL2-MBR translocations had a strong, statistically significant association with BCL2-MBR-positive tumors (OR = 26), but not with BCL2-MBR-negative tumors (OR = 0.9). All eight BCL2-MBR-positive tumors with pre-diagnosis BCL2 translocations were clonally related to these circulating cells, based on similarity of recombination sequences. These data indicate that blood BCL2-MBR translocations represent lymphoma precursor clones with malignant potential.

Influence of reproductive history and exogenous hormone use on prevalence and frequency of circulating t(14;18)-positive cells in a population-based cross-sectional study

Purpose

The t(14;18) translocation might represent an intermediate step in the pathogenesis of follicular lymphoma (FL), one of the most common subtypes of non-Hodgkin lymphoma. Circulating t(14;18)-positive cells can also be detected in 30–60 % of healthy individuals at low frequencies. Some studies found a negative association between reproductive factors or use of menopausal hormone therapy (MHT) with FL. The objective of this study was to evaluate whether there is an association between number of frequencies, oral contraceptive (OC) use, menopausal status and MHT, and t(14;18) prevalence and frequency in a representative population analysis based on an epidemiologic study in the northeastern part of Germany.

Methods

The analysis is based on results of buffy coat samples from 1,981 women of the Study of Health in Pomerania (SHIP-0) and data obtained in standardized face-to-face interviews. For prevalence, odds ratios (OR) and 95 % confidence intervals (CI) were calculated using unconditional logistic regression. Frequency data were analyzed using negative binomial regression. The multivariable models included age, number of pregnancies, menopausal status (premenopausal, natural, medical/surgical menopause), OC use and MHT as a measure for exogenous hormone exposure use.

Results

We found no association between reproductive history and combined exogenous hormone use on the prevalence of circulating t(14;18)-positive cells. Modeling MHT and OC use separately in a sensitivity analysis, the MHT parameter yielded statistical significance [OR 1.37 (95 % CI 1.04;1.81)]. t(14;18) frequency was associated with use of OC [incidence rate ratio (IRR) for ever use 3.18 (95 % CI 1.54;6.54)], current use [IRR 3.86 (1.56;9.54)], >10 years use [IRR 3.93 (1.67;9.23)] and MHT [restricted to postmenopausal women; IRR 2.63 (95 % CI 1.01;6.85)] in bivariate age-adjusted analyses. In the multivariable model, medical/surgical menopause [IRR 2.46 (1.11;5.44)] and the category ever use of OC and MHT were statistically significant [IRR 2.41 (1.09;5.33)].

Conclusions

Exogenous hormone use might be a risk factor for t(14;18) frequency rather than for t(14;18) prevalence. Further research on healthy individuals carrying a t(14;18) translocation and possible risk factors for malignant lymphoma is necessary to determine the additional molecular or immunological events that have to occur to develop FL.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-015-0525-4) contains supplementary material, which is available to authorized users.

The biology and treatment of plasmablastic lymphoma

Plasmablastic lymphoma (PBL) is an aggressive lymphoma commonly associated with HIV infection. However, PBL can also be seen in patients with other immunodeficiencies as well as in immunocompetent individuals. Because of its distinct clinical and pathological features, such as lack of expression of CD20, plasmablastic morphology, and clinical course characterized by early relapses and subsequent chemotherapy resistance, PBL can represent a diagnostic and therapeutic challenge for pathologists and clinicians alike. Despite the recent advances in the therapy of HIV-associated and aggressive lymphomas, patients with PBL for the most part have poor outcomes. The objectives of this review are to summarize the current knowledge on the epidemiology, biology, clinical and pathological characteristics, differential diagnosis, therapy, prognostic factors, outcomes, and potential novel therapeutic approaches in patients with PBL and also to increase the awareness toward PBL in the medical community.

Methylation of the nonhomologous end joining repair pathway genes does not explain the increase of translocations with aging

Chromosome translocations are especially frequent in human lymphomas and leukemias but are insufficient to drive carcinogenesis. Indeed, several of the so-called tumor specific translocations have been detected in peripheral blood of healthy individuals, finding a higher frequency of some of them with aging. The inappropriate repair of DNA double strand breaks by the nonhomologous end joining (NHEJ) pathway is one of the reasons for a translocation to occur. Moreover, fidelity of this pathway has been shown to decline with age. Although the mechanism underlying this inefficacy is unknown, other repair pathways are inactivated by methylation with aging. In this study, we analyzed the implication of NHEJ genes methylation in the increase of translocations with the age. To this aim, we determined the relationship between translocations and aging in 565 Spanish healthy individuals and correlated these data with the methylation status of 11 NHEJ genes. We found higher frequency of BCL2-JH and BCR-ABL (major) translocations with aging. In addition, we detected that two NHEJ genes (LIG4 and XRCC6) presented age-dependent promoter methylation changes. However, we did not observe a correlation between the increase of translocations and methylation, indicating that other molecular mechanisms are involved in the loss of NHEJ fidelity with aging.

Disease-specific mutations in mature lymphoid neoplasms: recent advances

Mature lymphoid neoplasms (MLN) are clinically and pathologically more complex than precursor lymphoid neoplasms. Until recently, molecular characterization of MLN was mainly based on cytogenetics/fluorescence in situ hybridization, allele copy number, and mRNA expression, approaches that yielded scanty gene mutation information. Use of massive parallel sequencing technologies has changed this outcome, and now many gene mutations have been discovered. Some of these are considerably frequent in, and substantially specific to, distinct MLN subtypes, and occur at single or several hotspots. They include the V600E BRAF mutation in hairy cell leukemia, the L265P MYD88 mutation in Waldenström macroglobulinemia, the G17V RHOA mutation in angioimmunoblastic T-cell lymphoma and peripheral T-cell lymphoma, not otherwise specified, and the Y640F//D661Y/V/H/I//N647I STAT3 mutations in T-cell large granular lymphocytic leukemia. Detecting these mutations is highly valuable in diagnosing MLN subtypes. Defining these mutations also sheds light on the molecular pathogenesis of MLN, furthering development of molecular targeting therapies. In this review, we focus on the disease-specific gene mutations in MLN discovered by recent massive sequencing technologies.

Burkitt lymphoma and MYC: what else is new?

Burkitt lymphoma (BL) is the most common non-Hodgkin lymphoma in children and adolescents, but at least 30% of cases occur in patients older than 60 years, and the absolute number of BL cases in adults exceeds those in childhood. BL is described as a monomorphic proliferation of medium-sized transformed B cells with round nuclei, clumped chromatin, basophilic cytoplasm, and squared-off cell borders, cytoplasmic vacuoles, medium-sized paracentral nucleoli, and a starry sky pattern. Translocation involving MYC is characteristic but not specific for BL. No single parameter is the gold standard for diagnosis; morphology, cytogenetics, immunophenotype, and gene expression profiles all may contribute to the diagnosis. Although neither EBV nor MYC are sufficient to cause BL there is increasing information from techniques such as complete RNA sequencing that identify essential pathways that are activated in the pathogenesis of BL. These findings suggest novel opportunities for improved therapeutic intervention.

Clonal B-cell lymphocytosis exhibiting immunophenotypic features consistent with a marginal-zone origin: is this a distinct entity?

Clonal B-cell lymphocytosis of potential marginal-zone origin (CBL-MZ) rarely progresses to a well-recognized lymphoma. CBL-MZ does not require treatment in the absence of progressive disease.

Incidence of bcr‑abl fusion transcripts in healthy individuals

Bcr‑abl fusion transcripts, resulting from translocation t(9;22), are hallmarks of Philadelphia chromosome positive (Ph+) leukemias. This translocation is detected in >90% of patients with chronic myelogenous leukemia and ~20% of acute lymphoblastic leukemia patients, which predominantly express the p210 and p190 proteins, respectively. Although the occurrence of t(9;22) in healthy individuals has been previously demonstrated, the number of studies is limited and the results are inconsistent. The present study screened for the presence of bcr‑abl transcripts in the blood of a group of healthy individuals using a sensitive‑nested reverse transcription polymerase chain reaction (RT‑PCR) assay. Samples were collected from 189 healthy volunteers (145 adults and 44 children). RNA was reverse transcribed and amplified by two rounds of PCR, amplifying the two common variants of bcr‑abl transcripts, p190 and p210. While the bcr‑abl p190 transcript was not detected, the p210 transcript was detected in ~10% of samples. Notably, the incidence of p210 translocation was higher in males (12.2%) compared with females (7.7%) and males were 2.4 times more likely to have the translocation. A significant incidence was also observed in adults compared with children, where adults were 6 times more likely to have the translocation. The presence of bcr‑abl transcripts in the blood of a significant proportion of healthy individuals should be considered in long‑term investigations to establish its exact association with the risk of developing leukemia. Furthermore, the current assays should be revised to consider the proportion of normal samples carrying the p210 transcripts when making a differential diagnosis.

Cancer-associated mutations in healthy individuals: assessing the risk of carcinogenesis

Mutations associated with hematopoietic malignancies have been repeatedly identified in healthy individuals. For certain cases, such as the t(14;18) translocation and monoclonal B-cell lymphocytosis, no clear link between the presence of aberrant cells and the later development of cancer has been established. Intriguingly, longitudinal studies suggest that these abnormalities persist for long periods of time in some individuals, but in others are transient in which they disappear completely. Here, we present a mathematical model, based on cellular replication limits, that provides a possible explanation for these seemingly contradictory findings. It proposes that the transient and persistent nature of the phenotypes depends on the stage in the differentiation pathway of a given lineage in which the mutation originates. Our work suggests that cellular replication limits may not only prevent cancer by aborting clonal expansion of cells, but also by influencing the fate of altered but nonneoplastic cells in healthy tissue.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.

A study for evaluation of different diagnostic approaches in acute leukemia in Egypt

Cytomorphology, cytochemistry, immunophenotyping, in addition to cytogenetic and molecular analyses have specific roles in the diagnosis and management of acute leukemias. This work was designed as a comparative study of different available methods for diagnosis of acute leukemia. The study comprised 47 cases with acute leukemia (21 cases with ALL and 26 cases with AML). Peripheral blood and bone marrow samples were subjected to through morphological examination of Leishman-stained smears, cytochemical analysis, immunophenotyping, conventional cytogenetic banding analysis, fluorescence in situ hybridization (FISH) for selected cases, and RT-PCR for detection of BCR-ABL rearrangement. The results of the study revealed that careful examination of Romanowsky-stained peripheral blood and BM films is fundamental in the diagnosis of acute leukemias, and when considered together with clinical and hematological features, indicates which of the more specialized techniques are most likely to be useful. The major role of cytochemistry was in the diagnosis of AML, while the major role of immunophenotyping was in the diagnosis of acute leukemia, which is not obviously myeloid. Apart from identification of chromosomal abnormalities unique to specific subtypes of leukemia, cytogenetic analysis had a salient impact on anticipating the prognosis and treatment outcome in acute leukemias. We could conclude that the techniques used in this study are considered complementary rather than alternatives and that stepwise employment of strategies is more cost effective than doing all the tests simultaneously.

Chromosomal translocations among the healthy human population: implications in oncogenesis

Chromosomal translocations are characteristic features of many cancers, especially lymphoma and leukemia. However, recent reports suggest that many chromosomal translocations can be found in healthy individuals, although the significance of this observation is still not clear. In this review, we summarize recent studies on chromosomal translocations in healthy individuals carried out in different geographical areas of the world and discuss the relevance of the observation with respect to oncogenesis.

High levels of bcl-2 protein expression do not correlate with genetic abnormalities but predict worse prognosis in patients with lymphoblastic lymphoma

We aimed to investigate bcl-2, bcl-6, and c-myc rearrangements in patients with lymphoblastic lymphoma (LBL), especially focus on the correlation of protein expression with genetic abnormalities. Moreover, their prognostic significance was further analyzed in LBL. Protein expression and genetic abnormalities of bcl-2, bcl-6, and c-myc were investigated in microarrayed tumors from 33 cases of T cell LBL and eight cases of B cell lineage. Immunohistochemical (IHC) staining was performed to evaluate protein expression, including bcl-2, bcl-6, c-myc, TdT, CD1α, CD34, Ki-67, PAX-5, CD2, CD3, CD4, CD8, and CD20. Genetic abnormalities of bcl-2, bcl-6, and c-myc were detected by dual color fluorescence in situ hybridization (FISH). Bcl-2 protein was positive in 51.2 % (21/41) of the patients, bcl-6 protein in 7.3 % (three out of 41), and c-myc protein in 78.0 % (32/41). Bcl-2 breakpoint was found in two cases by FISH analysis. There was no evidence of bcl-6 or c-myc rearrangement in patients with LBL. However, both gene gain and loss events occurred in bcl-2, bcl-6, and c-myc. A univariate analysis showed that stage III or IV, elevated lactate dehydrogenase (LDH), and positivity for bcl-2 protein were associated with shorter survival (p<0.05). Enhanced protein expression and detectable genetic abnormalities of bcl-2, bcl-6, and c-myc were observed in patients with LBL. No statistical correlation was found between IHC results and cytogenetic findings. Stage III or IV, elevated LDH, and positivity for bcl-2 protein were identified as adverse prognostic factors. The patients with more adverse factors would have increasingly worse prognosis.

A Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment

Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown.

New pathogenic mechanisms in Burkitt lymphoma

Two studies in this issue identify the landscape of somatic mutations in Burkitt lymphoma and highlight the pathogenic and clinical relevance of inactivating mutations of ID3, an inhibitor of the TCF3 transcription factor.

Understanding MYC-driven aggressive B-cell lymphomas: pathogenesis and classification

MYC is a potent oncogene initially identified as the target of the t(8;14)(q24;q32) chromosome translocation in Burkitt lymphoma. MYC gene alterations have been identified in other mature B-cell neoplasms that are usually associated with an aggressive clinical behavior. Most of these tumors originate in cells that do not normally express MYC protein. The oncogenic events leading to MYC up-regulation seem to overcome the inhibitory effect of physiological repressors such as BCL6 or BLIMP1. Aggressive lymphomas frequently carry additional oncogenic alterations that cooperate with MYC dysregulation, likely counteracting its proapoptotic function. The development of FISH probes and new reliable antibodies have facilitated the study of MYC gene alterations and protein expression in large series of patients, providing new clinical and biological perspectives regarding MYC dysregulation in aggressive lymphomas. MYC gene alterations in large B-cell lymphomas are frequently associated with BCL2 or BCL6 translocations conferring a very aggressive behavior. Conversely, MYC protein up-regulation may occur in tumors without apparent gene alterations, and its association with BCL2 overexpression also confers a poor prognosis. In this review, we integrate all of this new information and discuss perspectives, challenges, and open questions for the diagnosis and management of patients with MYC-driven aggressive B-cell lymphomas.