The transcription factor PU.1, necessary for B-cell development is expressed in lymphocyte predominance, but not classical Hodgkin's disease

Classic Hodgkin lymphoma in young people

Classic Hodgkin lymphoma (CHL) is a unique form of lymphoid cancer featuring a heterogeneous tumor microenvironment and a relative paucity of malignant Hodgkin and Reed-Sternberg (HRS) cells with characteristic phenotype. Younger individuals (children, adolescents and young adults) are affected as often as the elderly, producing a peculiar bimodal age-incidence profile that has generated immense interest in this disease and its origins. Decades of epidemiological investigations have documented the populations most susceptible and identified multiple risk factors that can be broadly categorized as either biological or environmental in nature. Most risk factors result in overt immunodeficiency or confer more subtle alterations to baseline health, physiology or immune function. Epstein Barr virus, however, is both a risk factor and well-established driver of lymphomagenesis in a significant subset of cases. Epigenetic changes, along with the accumulation of somatic driver mutations and cytogenetic abnormalities are required for the malignant transformation of germinal center-experienced HRS cell precursors. Chromosomal instability and the influence of endogenous mutational processes are critical in this regard, by impacting genes involved in key signaling pathways that promote the survival and proliferation of HRS cells and their escape from immune destruction. Here we review the principal features, known risk factors and lymphomagenic mechanisms relevant to newly diagnosed CHL, with an emphasis on those most applicable to young people.

Immunohistochemical Expression of B Cell Transcription Factors in Hodgkin’s Lymphoma and Their Use in Differential Diagnosis

Aim: Classical Hodgkin lymphoma is common, it is one of the lymphomas whose differential diagnosis can be difficult. It is thought that Hodgkin cell may originate from the germinal center. Our aim in this study was to determine the germinal center transformation markers OCT-2, BOB.1, BCL-6, PAX-5, CD20 and MUM-1 in Classic Hodgkin Lymphoma (CHL), Nodular Lymphocyte Predominant Hodgkin Lymphoma (NLPHL) and Diffuse Large B-cell Lymphoma (DLBCL) to evaluate the expressions of by immunohistochemical method and chromogenic in-situ hybridization (ISH) of EBV early RNAs (EBER). Material and methods: 49 biopsies diagnosed with Hodgkin lymphoma (HL), 5 with NLPHL and 19 with DLBCL were evaluated for CD30, PAX-5, OCT-2, BOB.1, MUM-1, BCL-6, and CD20, and EBER positivity. SPSS 18 was used for statistical analysis. Results: 73 lymphoma cases were included in the study, 61.6% males and 38.4% females. The median age of patients was 50 years. CHL (67.1%) was the most common lymphoma type, and mixed cellular Hodgkin lymphoma (MSHL) was the most common subtype. There was a statistically significant difference in CD30, OCT-2, BOB.1, MUM-1, PAX-5, CD20, BCL-6, EBER expression between CHL and DLBCL cases (p

Maintenance of Lineage Identity: Lessons from a B Cell

The maintenance of B cell identity requires active transcriptional control that enforces a B cell-specific program and suppresses alternative lineage genes. Accordingly, disrupting the B cell identity regulatory network compromises B cell function and induces cell fate plasticity by allowing derepression of alternative lineage-specific transcriptional programs. Although the B lineage is incredibly resistant to most differentiating factors, loss of just a single B lineage-specific transcription factor or the forced expression of individual non-B cell lineage transcription factors can radically disrupt B cell maintenance and allow dedifferentiation or transdifferentiation into entirely distinct lineages. B lymphocytes thereby offer an insightful and useful case study of how a specific cell lineage can maintain a stable identity throughout life and how perturbations of a single master regulator can induce cellular plasticity. In this article, we review the regulatory mechanisms that safeguard B cell identity, and we discuss how dysregulation of the B cell maintenance program can drive malignant transformation and enable therapeutic resistance.

Deregulated miRNAs Contribute to Silencing of B-Cell Specific Transcription Factors and Activation of NF-κB in Classical Hodgkin Lymphoma

Simple Summary

The role of transcriptionally deregulated miRNAs (microRNAs) in classical Hodgkin lymphoma (cHL) is still not fully understood. To address this issue, we have performed global miRNA expression profiling of commonly used cHL cell lines and we present a complete cHL miRNome (microRNome). Within this group, we identify miRNAs recurrently deregulated in cHL cell lines, and compare them to non-Hodgkin lymphoma cell lines and sorted normal CD77⁺ germinal centre B-cells. Moreover, we show that several of the recurrently overexpressed miRNAs in cHL cell lines, and also primary microdissected HRS (Hodgkin and Reed-Sternberg) cells, target known B-cell-related transcription factors and NF-κB inhibitors. These findings provide evidence that deregulated miRNAs contribute to the loss of B-cell phenotype and NF-κB activation observed in this lymphoma.

Abstract

A hallmark of classical Hodgkin lymphoma (cHL) is the attenuation of B-cell transcription factors leading to global transcriptional reprogramming. The role of miRNAs (microRNAs) involved in this process is poorly studied. Therefore, we performed global miRNA expression profiling using RNA-seq on commonly used cHL cell lines, non-Hodgkin lymphoma cell lines and sorted normal CD77⁺ germinal centre B-cells as controls and characterized the cHL miRNome (microRNome). Among the 298 miRNAs expressed in cHL, 56 were significantly overexpressed and 23 downregulated (p < 0.05) compared to the controls. Moreover, we identified five miRNAs (hsa-miR-9-5p, hsa-miR-24-3p, hsa-miR-196a-5p, hsa-miR-21-5p, hsa-miR-155-5p) as especially important in the pathogenesis of this lymphoma. Target genes of the overexpressed miRNAs in cHL were significantly enriched (p < 0.05) in gene ontologies related to transcription factor activity. Therefore, we further focused on selected interactions with the SPI1 and ELF1 transcription factors attenuated in cHL and the NF-ĸB inhibitor TNFAIP3. We confirmed the interactions between hsa-miR-27a-5p:SPI1, hsa-miR-330-3p:ELF-1, hsa-miR-450b-5p:ELF-1 and hsa-miR-23a-3p:TNFAIP3, which suggest that overexpression of these miRNAs contributes to silencing of the respective genes. Moreover, by analyzing microdissected HRS cells, we demonstrated that these miRNAs are also overexpressed in primary tumor cells. Therefore, these miRNAs play a role in silencing the B-cell phenotype in cHL.

Usefulness of BATF3 Immunohistochemistry in Diagnosing Classical Hodgkin Lymphoma

It is well recognized that the AP-1 transcription factor BATF3 is constitutively expressed in Hodgkin/Reed-Sternberg (HRS) cells, but its potential as a diagnostic marker for classical Hodgkin lymphoma (cHL) has not yet been addressed. In this study, we performed immunohistochemistry and analyzed the BATF3 expression in lymphoma cells on 218 lymphoma samples belonging to 14 different lymphoma entities. We observed varying degrees of BATF3 expression in nearly half of the cases (n = 100) with BATF3 expression being a constitutive feature of cHL (n = 53) and anaplastic large cell lymphoma (ALCL). By scoring BATF3 expression (BATF3-score) we observed constitutively high BATF3-scores in cHL and ALCL and low to moderate BATF3-scores in all other entities examined. Western blot analysis confirmed BATF3 protein expression in cell lysates from cHL cell lines (n = 7). Thus, BATF3 can be considered a useful IHC marker for the diagnosis of cHL as it is highly sensitive and sufficiently specific when analyzed by BATF3-scoring.

Hodgkin lymphoma

Hodgkin lymphoma (HL) is a B cell lymphoma characterized by few malignant cells and numerous immune effector cells in the tumour microenvironment. The incidence of HL is highest in adolescents and young adults, although HL can affect elderly individuals. Diagnosis is based on histological and immunohistochemical analyses of tissue from a lymph node biopsy; the tissue morphology and antigen expression profile enable classification into one of the four types of classic HL (nodular sclerosis, mixed cellularity, lymphocyte-depleted or lymphocyte-rich HL), which account for the majority of cases, or nodular lymphocyte-predominant HL. Although uncommon, HL remains a crucial test case for progress in cancer treatment. HL was among the first systemic neoplasms shown to be curable with radiation therapy and multiagent chemotherapy. The goal of multimodality therapy is to minimize lifelong residual treatment-associated toxicity while maintaining high levels of effectiveness. Recurrent or refractory disease can be effectively treated or cured with high-dose chemotherapy followed by autologous haematopoietic stem cell transplantation, and prospective trials have demonstrated the potency of immunotherapeutic approaches with antibody-drug conjugates and immune checkpoint inhibitors. This Primer explores the wealth of information that has been assembled to understand HL; these updated observations verify that HL investigation and treatment remain at the leading edge of oncological research.

The c-Jun and JunB transcription factors facilitate the transit of classical Hodgkin lymphoma tumour cells through G1

Classical Hodgkin Lymphoma (cHL) is primarily a B cell lymphoid neoplasm and a member of the CD30–positive lymphomas. cHL and the other CD30–positive lymphomas are characterized by the elevated expression and/or constitutive activation of the activator protein-1 (AP-1) family transcription factors, c-Jun and JunB; however, the specific roles they play in the pathobiology of cHL are unclear. In this report we show that reducing either c-Jun or JunB expression with short-hairpin RNAs (shRNAs) reduced the growth of cHL cell lines in vitro and in vivo, primarily through impairing cell cycle transition through G₁. We further investigated the effect of c-Jun and JunB knock-down on proliferation in another CD30–positive lymphoma, anaplastic lymphoma kinase-positive, anaplastic large cell lymphoma (ALK+ ALCL). We found that JunB knock-down in most ALK+ ALCL cell lines examined also resulted in reduced proliferation that was associated with a G₀/G₁ cell cycle defect. In contrast, c-Jun knock-down in multiple ALK+ ALCL cell lines had no effect on proliferation. In summary, this study directly establishes that both c-Jun and JunB play roles in promoting HRS cell proliferation. Furthermore, we demonstrate there are similarities and differences in c-Jun and JunB function between cHL and ALK+ ALCL.

The Histone Demethylase LSD1 Regulates B Cell Proliferation and Plasmablast Differentiation

B cells undergo epigenetic remodeling as they differentiate into Ab-secreting cells (ASC). LSD1 is a histone demethylase known to decommission active enhancers and cooperate with the ASC master regulatory transcription factor Blimp-1. The contribution of LSD1 to ASC formation is poorly understood. In this study, we show that LSD1 is necessary for proliferation and differentiation of mouse naive B cells (nB) into plasmablasts (PB). Following LPS inoculation, LSD1-deficient hosts exhibited a 2-fold reduction of splenic PB and serum IgM. LSD1-deficient PB exhibited derepression and superinduction of genes involved in immune system processes; a subset of these being direct Blimp-1 target-repressed genes. Cell cycle genes were globally downregulated without LSD1, which corresponded to a decrease in the proliferative capacity of LSD1-deficient activated B cells. PB lacking LSD1 displayed increased histone H3 lysine 4 monomethylation and chromatin accessibility at nB active enhancers and the binding sites of transcription factors Blimp-1, PU.1, and IRF4 that mapped to LSD1-repressed genes. Together, these data show that LSD1 is required for normal in vivo PB formation, distinguish LSD1 as a transcriptional rheostat and epigenetic modifier of B cell differentiation, and identify LSD1 as a factor responsible for decommissioning nB active enhancers.

Sjögren's syndrome X-chromosome dose effect: An epigenetic perspective

Sjögren's syndrome (SS) is a chronic autoimmune disease affecting exocrine glands leading to mouth and eyes dryness. The extent to which epigenetic DNA methylation changes are responsible for an X-chromosome dose effect has yet to be determined. Our objectives were to (i) describe how epigenetic DNA methylation changes could explain an X-chromosome dose effect in SS for women with normal 46,XX genotype and (ii) determine the relevant relationships to this dose effect, between X-linked genes, genes controlling X-chromosome inactivation (XCI) and genes encoding associated transcription factors, all of which are differentially expressed and/or differentially methylated in the salivary glands of patients with SS. We identified 58 upregulated X-chromosome genes, including 22 genes previously shown to escape XCI, based on the analysis of SS patient salivary gland GEO2R gene expression datasets. Moreover, we found XIST and its cis regulators RLIM, FTX, and CHIC1, and polycomb repressor genes of the PRC1/2 complexes to be upregulated. Many of the X-chromosome genes implicated in SS pathogenesis can be regulated by transcription factors which we found to be overexpressed and/or differentially methylated in patients with SS. Determination of the mechanisms underlying methylation-dependent gene expression and impaired XCI is needed to further elucidate the etiopathogenesis of SS.

A Case of Chemotherapy-Refractory "THRLBCL like Transformation of NLPHL" Successfully Treated with Lenalidomide

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a subtype of nonclassical Hodgkin lymphoma (HL). It resembles non-Hodgkin lymphoma (NHL), by expressing classic B cell markers such as CD20 and CD79a however lacks definitive HL markers (such as CD15 and CD30). T cell histiocyte-rich large B cell lymphoma (THRLBCL), on the other hand, is a distinct entity classified under NHL and considered a variant of diffuse large B cell lymphoma (DLBCL). NLPHL can look morphologically and immunologically similar to THRLBCL and often poses a diagnostic challenge. Neoplastic cells in both NLPHL and THRLBCL express B cell markers and are typically scattered in a background of reactive cells. The two major differences are the background cell type and the morphologic pattern. Despite having a phenotypic resemblance, they have distinct biologic behavior and clinical course. NLPHL typically has an indolent course, and THRLBCL has an aggressive course. Hence, differentiating these two entities is critical not only for prognosis but for treatment purposes. Of note, NLPHL has a small risk of transformation to an aggressive lymphoma such as THRLBCL.

Biology of classical Hodgkin lymphoma: implications for prognosis and novel therapies

Hodgkin lymphoma is considered a prime example of treatment success, with cure rates exceeding 80% using modern combined modality therapies. However, especially in adolescents and young adults, treatment-related toxicity and long-term morbidity still represent persistent challenges. Moreover, outcomes in patients with relapsed or refractory disease remain unfavorable in the era of high-dose chemotherapy and stem-cell transplantation. Hence, there is a high demand for novel and innovative alternative treatment approaches. In recent years, many new therapeutic agents have emerged from preclinical and clinical studies that target molecular hallmarks of Hodgkin lymphoma, including the aberrant phenotype of the tumor cells, deregulated oncogenic pathways, and immune escape. The antibody-drug conjugate brentuximab vedotin and immune checkpoint inhibitors have already shown great success in patients with relapsed/refractory disease, leading to US Food and Drug Administration approval and new trials testing these agents in various clinical settings. The expanding knowledge and understanding of Hodgkin lymphoma biology and disease progression, as well as the development of robust tools for biomarker-driven risk stratification and therapeutic decision making, continue to be fundamentally important for the success of these and other novel agents. We anticipate that the availability and clinical implementation of novel molecular assays will be instrumental in an era of rapid shifts in the treatment landscape of this disease. Here, we review the current knowledge of Hodgkin lymphoma pathobiology, highlighting the related development of novel treatment strategies and prognostic models that hold the promise to continually challenge and change the current standard of care in classical Hodgkin lymphoma.

J chain and myocyte enhancer factor 2B are useful in differentiating classical Hodgkin lymphoma from nodular lymphocyte predominant Hodgkin lymphoma and primary mediastinal large B-cell lymphoma

Although most classical Hodgkin lymphomas (CHLs) are easily distinguished from nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) and primary mediastinal large B-cell lymphoma (PMBL), cases with significant CD20 expression cause diagnostic confusion. Although the absence of OCT-2 and BOB.1 are useful in these circumstances, a variable proportion of CHLs are positive for these antigens. We investigated the utility of J chain and myocyte enhancer factor 2B (MEF2B) in the diagnosis of CHL; NLPHL; PMBL; T-cell/histiocyte-rich large B-cell lymphoma (TCRLBL); and B-cell lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and CHL, compared with OCT-2 and BOB.1. J chain and MEF2B highlighted lymphocyte predominant (LP) cells in 20/20 (100%) NLPHLs and were negative in 43/43 (100%) CHLs. Fourteen of 15 (93%) PMBLs and 4/4 (100%) TCRLBLs were MEF2B positive, whereas 67% of PMBLs and 50% of TCRLBLs were J chain positive. Three of 3 B-cell lymphomas, unclassifiable, with features intermediate between diffuse large B-cell lymphoma and CHL, were negative for J chain and MEF2B. J chain and MEF2B were 100% sensitive and specific for NLPHL versus CHL. MEF2B was 100% sensitive and 98% specific for PMBL versus CHL. Whereas loss of OCT-2 and/or BOB.1 expression had a sensitivity of only 86% and specificity of 100% for CHL versus NLPHL, PMBL, and TCRLBL, lack of both J chain and MEF2B expression was 100% sensitive and 97% specific. J chain and MEF2B are highly sensitive and specific markers of NLPHL versus CHL; are particularly useful in highlighting LP cells; and, with rare exception, are of greater utility than OCT-2 and BOB.1 in differentiating CHL from NLPHL and other large B-cell lymphomas.

Quantifying deleterious effects of regulatory variants

The majority of genome-wide association study (GWAS) risk variants reside in non-coding DNA sequences. Understanding how these sequence modifications lead to transcriptional alterations and cell-to-cell variability can help unraveling genotype-phenotype relationships. Here, we describe a computational method, dubbed CAPE, which calculates the likelihood of a genetic variant deactivating enhancers by disrupting the binding of transcription factors (TFs) in a given cellular context. CAPE learns sequence signatures associated with putative enhancers originating from large-scale sequencing experiments (such as ChIP-seq or DNase-seq) and models the change in enhancer signature upon a single nucleotide substitution. CAPE accurately identifies causative cis-regulatory variation including expression quantitative trait loci (eQTLs) and DNase I sensitivity quantitative trait loci (dsQTLs) in a tissue-specific manner with precision superior to several currently available methods. The presented method can be trained on any tissue-specific dataset of enhancers and known functional variants and applied to prioritize disease-associated variants in the corresponding tissue.

Pharmacological restoration and therapeutic targeting of the B-cell phenotype in classical Hodgkin lymphoma

A pharmacological screening identified compounds that reactivate B-cell–specific gene expression in cHL cell lines. B-cell phenotype-restoring drug combinations render cHL cell lines susceptible to B-NHL–reminiscent targeted therapies.

Mediastinal Gray Zone Lymphoma

Aim. To identify aggressively behaving classical Hodgkin lymphoma (CHL) of mediastinum and primary mediastinal B-cell lymphoma (PMBCL) and to classify them as mediastinal gray zone lymphoma(MGZL) and to define a minimum immunopanel for the diagnosis of MGZL. Materials and Methods. Ninety-two mediastinal B-cell lymphomas were reviewed with a wide immunopanel and were classified as CHL, PMBCL, or MGZL. CHL with an expression of 3 or 4 transcription factors performed worse, and hence the CHL with ≥3 transcription factors were classified as MGZL-CHL. In PMBCL, the cases with a weak or negative CD20 and positive CD15 as well as those cases showing cyclin E positivity with a negative or focal LCA and any one of the transcription factors were classified as MGZL-PMBCL. Results. The MGZL cases expanded from 9 to 28 cases after using an extended immunopanel. CHL and PMBCL had a disease-free survival rate of 86.8% and 69.2% and an overall survival rate of 97.4% and 80.8%, respectively. MGZL-CHL and MGZL-PMBCL had a disease-free survival rate of 33% and 40% and an overall survival rate of 66.7% and 60%, respectively. Conclusion. Thus, the MGZL may be a wider category than we think and hence the use of a wide immunopanel is recommended to identify the aggressively behaving mediastinal B-cell lymphomas.

Management of relapsed or refractory hodgkin lymphoma with second-generation antibody-drug conjugates: focus on brentuximab vedotin

Brentuximab vedotin (Adcetris, Seattle Genetics) is an antibody-drug conjugate (ADC) that joins an anti-CD 30 monoclonal antibody with the anti-tubulin agent monomethyl auristatin E via a dipeptide linker. It has demonstrated significant activity in CD 30-positive lymphomas and is currently approved by the US FDA for treatment of Hodgkin lymphoma that has relapsed following autologous stem-cell transplantation, or after two lines of chemotherapy in non-transplant candidates. Brentuximab vedotin has also been approved for the treatment of relapsed anaplastic large-cell lymphoma after front-line chemotherapy. We briefly review the biology of Hodgkin lymphoma, with a focus on the pathogenic role of CD 30 as well as the development of CD 30-targeted therapy. We also discuss both the current role of brentuximab vedotin in the management of relapsed and refractory Hodgkin lymphoma and the likely future developments for this agent.

Contribution of the Epstein-Barr Virus to the Pathogenesis of Hodgkin Lymphoma

The morphology of the pathognomonic Hodgkin and Reed-Sternberg cells (HRS) of Hodgkin lymphoma was described over a century ago, yet it was only relatively recently that the B-cell origin of these cells was identified. In a proportion of cases, HRS cells harbour monoclonal forms of the B lymphotropic Epstein-Barr virus (EBV). This review summarises current knowledge of the pathogenesis of Hodgkin lymphoma with a particular emphasis on the contribution of EBV.

Epstein-Barr virus and the origin of Hodgkin lymphoma

Although Epstein-Barr virus (EBV) is present in the malignant Hodgkin/Reed-Sternberg (HRS) cells of a proportion of cases of classical Hodgkin lymphoma (cHL), how the virus contributes to the pathogenesis of this disease remains poorly defined. It is clear from the studies of other EBV-associated cancers that the virus is usually not sufficient for tumor development and that other oncogenic co-factors are required. This article reviews what is known about the contribution of EBV to the pathogenesis of cHL and focuses on emerging evidence implicating chronic inflammation as a potential oncogenic co-factor in this malignancy.

CluGene: A Bioinformatics Framework for the Identification of Co-Localized, Co-Expressed and Co-Regulated Genes Aimed at the Investigation of Transcriptional Regulatory Networks from High-Throughput Expression Data

The full understanding of the mechanisms underlying transcriptional regulatory networks requires unravelling of complex causal relationships. Genome high-throughput technologies produce a huge amount of information pertaining gene expression and regulation; however, the complexity of the available data is often overwhelming and tools are needed to extract and organize the relevant information. This work starts from the assumption that the observation of co-occurrent events (in particular co-localization, co-expression and co-regulation) may provide a powerful starting point to begin unravelling transcriptional regulatory networks. Co-expressed genes often imply shared functional pathways; co-expressed and functionally related genes are often co-localized, too; moreover, co-expressed and co-localized genes are also potential targets for co-regulation; finally, co-regulation seems more frequent for genes mapped to proximal chromosome regions. Despite the recognized importance of analysing co-occurrent events, no bioinformatics solution allowing the simultaneous analysis of co-expression, co-localization and co-regulation is currently available. Our work resulted in developing and valuating CluGene, a software providing tools to analyze multiple types of co-occurrences within a single interactive environment allowing the interactive investigation of combined co-expression, co-localization and co-regulation of genes. The use of CluGene will enhance the power of testing hypothesis and experimental approaches aimed at unravelling transcriptional regulatory networks. The software is freely available at http://bioinfolab.unipg.it/.

Hodgkin lymphoma

Hodgkin lymphoma (HL), a B cell-derived cancer, is one of the most common lymphomas. In HL, the tumor cells--Hodgkin and Reed-Sternberg (HRS) cells--are usually very rare in the tissue. Although HRS cells are derived from mature B cells, they have largely lost their B cell phenotype and show a very unusual co-expression of markers of various hematopoietic cell types. HRS cells show deregulated activation of multiple signaling pathways and transcription factors. The activation of these pathways and factors is partly mediated through interactions of HRS cells with various other types of cells in the microenvironment, but also through genetic lesions. The transforming events involved in the pathogenesis of HL are only partly understood, but mutations affecting the NF-κB and JAK/STAT pathways are frequent. The dependency of HRS cells on microenvironmental interactions and deregulated signaling pathways may offer novel strategies for targeted therapies.

Rituximab plus Ifosfamide, Carboplatin and Etoposide for T-Cell/Histiocyte-Rich B-Cell Lymphoma Arising in Nodular Lymphocyte-Predominant Hodgkin's Lymphoma

A small subset of patients with nodular lymphocyte-predominant Hodgkin's lymphoma (NLPHLs) develop a non-Hodgkin lymphoma either concurrently or subsequently, usually T-cell/histiocyte-rich B-cell lymphomas (T/HRBCL), which are subtypes of diffuse large B-cell lymphomas (DLBCL). The standard treatment of DLBCL patients is rituximab-based chemotherapy with cyclophosphamide, adriamycin, vincristine and prednisolone. However, the administration of this chemotherapy regimen to patients with DLBCL arising in NLPHL brings concern about the cardiac toxicity of anthracycline because the majority of these patients had already received anthracycline-based chemotherapy with doxorubicin, bleomycin, vinblastine and dacarbazine at the time of NLPHL. Herein, we report 2 patients with sequential transformation of NLPHL to T/HRBCL. They initially presented with limited-stage NLPHL and subsequently developed T/HRBCL after 16 and 8 months, respectively. At the time of T/HRBCL, they were treated with rituximab, ifosfamide, carboplatin and etoposide, and complete responses were obtained.

T cell/histiocyte-rich large B-cell lymphoma: an update on its biology and classification

T cell/histiocyte-rich large B-cell lymphoma (THRLBCL), originally considered an uncommon variant of Diffuse Large B-Cell Lymphoma (DLBCL), is recognized by the World Health Organisation as a separate clinicopathological entity since 2008. It predominantly affects middle aged men often presenting with advanced stage disease frequently involving spleen, liver and bone marrow at time of diagnosis. According to the WHO, this lymphoma is morphologically characterized by less than 10% of large neoplastic B cells in a background of abundant T cells and frequently histiocytes. Differentiating THRLBCL from other lymphoproliferative disorders such as Nodular Lymphocyte Predominant Hodgkin Lymphoma (NLPHL) and Lymphocyte-Rich classical Hodgkin lymphoma (LRcHL) is important from a clinical point of view and can be achieved in most cases, given adequate biopsy specimens, by careful morphological and immunohistochemical evaluation of both the neoplastic cells as well as the nonneoplastic stromal component. According to this WHO definition, THRLBCL is still considered a clinically heterogeneous entity, though it is noted that especially the cases containing numerous histiocytes behave aggressively and show resistance to current therapies for DLBCL. Gene expression profiling studies of THRLBCL provided evidence for a prominent role for this histiocytic component that is important for a tolerogenic host immune response in which they may assist neoplastic cells in escaping the T cell-mediated immune surveillance. Therefore, reserving the diagnosis of THRLBCL to cases containing a large proportion of histiocytes might be relevant, as modulating their activity could provide new therapeutic options.

Epigenetic and transcriptional control of the 15-lipoxygenase-1 gene in a Hodgkin lymphoma cell line

Lipoxygenases oxidatively metabolize polyunsaturated fatty acids to a rich spectrum of biologically active metabolites. The present study aimed at delineating the transcriptional and epigenetic mechanisms leading to 15-lipoxygenase-1 (15-LOX-1) expression in the Hodgkin lymphoma (HL) cell line L1236. Examination of the 15-LOX-1 5' promoter region demonstrated three putative binding sites for signal transducer and activator of transcription (STAT6) within the proximal 1200 base pairs relative to the start codon. Analysis by serial promoter deletions and STAT6 binding site mutations indicated that all three STAT6 binding sites are required for full activation of the 15-LOX-1 promoter. Chromatin immunoprecipitation assay demonstrated that these regions were occupied by STAT6 in L1236 (15-LOX-1 positive) but not in L428 (15-LOX-1 negative) cultured HL cells. Furthermore, DNA hypomethylation and histone hyperacetylation were detectable within the core promoter region of 15-LOX-1 only in L1236 cells but not L428 cells. Taken together, our data indicate that STAT6 activation and chromatin remodeling by DNA demethylation and histone acetylation are crucial for transcriptional activation of 15-LOX-1 in cultured HL cells. These prerequisites are fulfilled in the L1236 cell line, but not in the L428 cell line.

Heterogeneous expression of Src tyrosine kinases Lyn, Fyn and Syk in classical Hodgkin lymphoma: prognostic implications

The aim of this study was to determine the prognostic significance of the expression of Lyn, Fyn and Syk in Hodgkin lymphoma and its correlation with Epstein-Barr virus (EBV) infection. With this in mind, 96 patients with classical Hodgkin lymphoma were immunohistochemically evaluated for Lyn, Fyn and Syk expression in Hodgkin and Reed-Sternberg cells, and the results were correlated with the presence of EBV and patient outcomes. These three kinases were heterogeneously expressed in classical Hodgkin lymphoma cases. As there are no cut-offs established for these antibodies, they were introduced as continuous variables in the model. Statistical analysis showed that the expression of Syk and Fyn was significantly associated with shorter failure-free survival. Syk and Fyn may be useful to predict at diagnosis the treatment response of patients with classical Hodgkin lymphoma. There was a significant association between EBV infection and Lyn expression (p < 0.05). Overexpression of Syk and the availability of Syk inhibitors suggest that this molecule might be a therapeutic strategy worthy of development for cases expressing this molecule.

Transformation to Aggressive Lymphoma in Nodular Lymphocyte-Predominant Hodgkin's Lymphoma

Purpose

Prior observations suggest a higher risk of transformation of nodular lymphocyte-predominant Hodgkin's lymphoma (NLPHL) to aggressive lymphoma, most commonly diffuse large B-cell lymphoma (DLBCL), than in classical Hodgkin's lymphoma. We evaluated the frequency of transformation in all patients diagnosed with NLPHL at the British Columbia Cancer Agency with long-term follow-up.

Patients and Methods

The Lymphoid Cancer Database of the British Columbia Cancer Agency was searched to identify all patients diagnosed with NLPHL between 1965 and 2006. After pathologic review, 95 patients with NLPHL were confirmed.

Results

Patients with NLPHL had the following characteristics at diagnosis: median age of 37 years, 73% male, and 68% stage I or II disease. With a median follow-up time for living patients of 6.5 years (range, 2.5 to 33 years), 13 patients (14%) experienced transformation to aggressive lymphoma (median time to transformation, 8.1 years; range, 0.35 to 20.3 years). The actuarial risk of transformation to aggressive lymphoma was 7% and 30% at 10 and 20 years, respectively. Transformation was more likely in patients with initial splenic involvement (P = .006) at the time of diagnosis of NLPHL. The 10-year progression-free and overall survival rates in patients with transformed lymphoma were 52% and 62%, respectively.

Conclusion

The risk of transformation in patients with NLPHL to DLBCL is substantial and underappreciated. Because transformation can occur years after the primary diagnosis of NLPHL, long-term follow-up of these individuals is necessary to accurately estimate the risk of development of secondary DLBCL.

EBV in Hodgkin Lymphoma

Up to 40% of Hodgkin lymphoma (HL) cases are associated with the Epstein-Barr virus (EBV). Clonal viral genomes can be found in the HL tumor cells, the Hodgkin Reed-Sternberg cells (HRS). The latent infection results in expression of the viral oncogenes LMP1 and LMP2A which contribute to generate the particular phenotype of the HRS cells. EBV does not only undergo epigenetic changes of its genome during latency, but also induces epigenetic changes in the host genome. The presence of EBV may alter the composition and activity of the immune cells surrounding the HRS cells. EBV favours a Th1 reaction, but this attempt at a cell mediated immune response appears to be ineffective. The presence of EBV in HL is associated with several clinicopathological characteristics: It is more frequent in cases with mixed cellular histology, in males, in children and older adults, and in developing countries, while the young-adult onset HL of nodular sclerosis type in industrialized countries is typically EBV-negative. Countries in the Mediterranean area often show an intermediate epidemiological pattern. Recent studies suggest a genetic predisposition to develop EBV-associated HL. Circulating EBV-DNA may serve as a biomarker to monitor response to therapy, and eventually, EBV will become a target for therapeutic intervention also in HL.

Hodgkin lymphoma: an update on its biology with new insights into classification

In the past few years, there has been a greater understanding of the spectrum and biology of Hodgkin lymphoma (HL). In standard texts, HL is classified as 2 distinct entities, namely nodular lymphocyte-predominant HL and classical HL (CHL). However, recent evidence suggests that CHL is not a single disease. Although the mixed cellularity and lymphocyte-depleted subtypes might be part of a biologic continuum, the nodular sclerosis subtype has a distinct epidemiology, clinical presentation, and histology. Nodular sclerosis HL might also be related to primary mediastinal B-cell lymphoma and mediastinal gray-zone lymphomas. We present an update on the pathobiology of HL and discuss these biologic and clinical differences in this review.

Hodgkin-like anaplastic large cell lymphoma (previously designated in the REAL classification) has same immunophenotypic features to classical Hodgkin lymphoma

In the WHO classification, the majority of Hodgkin-like ALCL cases as defined by the REAL classification are considered to be CHL. However, establishing a histological diagnosis for the gray zone between CHL and ALCL is often confusing. In this study, we re-evaluated such cases by performing immunohistochemistry with antibodies against PAX-5/BSAP, Oct.2, and BOB.1/OBF.1. Expression of PAX-5/BSAP was observed in 88% (76/87) of CHL specimens and none (0/11) of ALK-positive ALCL specimens. Among specimens of Hodgkin-like ALCL and ALK-negative ALCL, expression of PAX-5/BSAP was observed in 77% (20/26) and 18% (3/17), respectively. Most of the PAX-5/BSAP-positive specimens were negative for Oct.2 and/or BOB.1/OBF.1 except for four CHL specimens. Our results may support the WHO classification in which most cases of Hodgkin-like ALCL are classified as CHL. However, the patients with Hodgkin-like ALCL with CHL-immunophenotype (PAX-5/BSAP-positive and negative for Oct.2 and/or BOB.1) did not have a favorable outcome, with a 5-year OS rate of 58%.

Pathogenesis of classical and lymphocyte-predominant Hodgkin lymphoma

Hodgkin and Reed-Sternberg (HRS) cells in classical Hodgkin lymphoma (HL) and lymphocytic and histiocytic (L&H) cells in nodular lymphocyte-predominant HL (NLPHL) are derived from germinal-center B cells. HRS cells have, however, largely lost their B cell phenotype and aberrantly express markers and transcriptional regulators of other hematolymphoid cell types. Deregulation of multiple signaling pathways and downstream transcription factors, including receptor tyrosine kinases, nuclear factor-kappa B (NF-kappaB), and Janus kinase/signal transducer and activator of transcription (JAK/STAT), is a further hallmark of HRS cells. These cells harbor genetic lesions that contribute to or cause increases in the activity of transcription factors of the NF-kappaB and STAT families. HRS cells are found within a mixed reactive cellular infiltrate and interact with these nonmalignant cells in a complex fashion that appears to be essential for HRS cell survival and proliferation. Less is known about the pathogenesis of L&H cells in NLPHL, but increases in the activity of receptor tyrosine kinases, NF-kappaB, and JAK/STAT have also been detected.

Epigenetic dysregulation of the host cell genome in Epstein-Barr virus-associated neoplasia

Epstein-Barr virus (EBV), a human herpesvirus, is associated with a wide variety of malignant tumors. The expression of the latent viral RNAs is under strict, host-cell dependent transcriptional control. This results in an almost complete transcriptional silencing of the EBV genome in memory B-cells. In tumor cells, germinal center B-cells and lymphoblastoid cells, distinct viral latency promoters are active. Epigenetic mechanisms contribute to this strict control. In EBV-infected cells, epigenetic mechanisms also alter the expression of cellular genes, including tumor suppressor genes. In Nasopharyngeal Carcinoma, the hypermethylation of certain cellular promoters is attributed to the upregulation of DNA methyltransferases by the viral oncoprotein LMP1 (latent membrane protein 1) via JNK/AP1-signaling. The role of other viral latency products in the epigenetic dysregulation of the cellular genome remains to be established. Analysis of epigenetic alterations in EBV-associated neoplasms may result in a better understanding of their pathogenesis and may facilitate the development of new therapies.

Molecular biology of Hodgkin lymphoma

Hodgkin lymphoma (HL) is derived from mature B cells and subdivided into classical HL and nodular lymphocyte predominant HL (NLPHL). HL is unique among human B cell lymphomas because of the rarity of the lymphoma cells, the Hodgkin and Reed-Sternberg (HRS) cells in classical HL and the lymphocyte-predominant (LP) cells in NLPHL, which usually account for 0.1% to 10% of the cells in the affected tissues. Moreover, HRS cells are unique in the extent to which they have lost their B cell-typical gene expression pattern. Deregulation of transcription factor networks plays a key role in this reprogramming process. HRS cells show strong constitutive activity of the transcription factor NF-kappaB. Multiple mechanisms likely contribute to this deregulated activation, including signaling through particular receptors and genetic lesions. Inactivating mutations in the TNFAIP3 tumor suppressor gene, encoding a negative regulator of NF-kappaB activity, were recently identified in about 40% of patients with classical HL. HRS cells are latently infected by Epstein-Barr virus in about 40% of patients, and an important role of this virus in HL pathogenesis-in particular for cases in which HRS cells had lost the capacity to express a B-cell receptor due to destructive somatic mutation-was recently substantiated.

The biology of Hodgkin's lymphoma

Hodgkin's lymphoma was first described in 1832. The aetiology of this lymphoma, however, remained enigmatic for a long time. Only within the past 10 years has the B-cell nature of the pathognomonic Hodgkin and Reed-Sternberg (HRS) cells been revealed, along with several recurrent genetic lesions. The pathogenetic role for Epstein-Barr virus infection has also been substantiated. HRS cells in classical Hodgkin's lymphoma have several characteristics that are unusual for lymphoid tumour cells, and the Hodgkin's lymphoma microenvironment is dominated by an extensive mixed, potentially inflammatory cellular infiltrate. Understanding the contribution of all of these changes to the pathogenesis of this disease is essential for the development of novel therapies.

Proteomic characterization of primary diffuse large B-cell lymphomas in the central nervous system

OBJECT

The lack of primary lymphoid tissue within the central nervous system (CNS) confounds our understanding of the pathogenesis of primary CNS lymphomas (PCNSLs). Comparing the protein expression of PCNSLs and sporadic systemic lymphomas (SSLs) provides a useful strategy for identifying a molecular signature that characterizes disease-associated features and provides information regarding tumor initiation and progression.

METHODS

Seven diffuse large B-cell PCNSLs were selected to undergo 2D gel electrophoresis, and profiled proteomes from these PCNSLs were compared with those from 7 diffuse large B-cell SSLs. Distinguishing proteins were sequenced using mass spectrometry.

RESULTS

Two-dimensional gel electrophoresis identified an average of 706 proteins from each specimen. Computerized gel analysis and manual reconfirmation revealed a 96% similarity in the proteomes of PCNSLs and SSLs. Comparative analysis identified 9 proteins significantly overexpressed (p < 0.05) and 16 proteins downregulated in PCNSLs. The proteomic findings were further validated using Western blot and immunohistochemical staining.

CONCLUSIONS

The similarities in proteomic patterns between PCNSLs and SSLs suggest that these tumor types share structural similarities, acquired during differentiation. The ultimate fate of lymphomatous cells (CNS vs systemic) may be related to differentially expressed proteins, which function in homing and host processing. Elucidating the roles of these differentially expressed proteins will prove valuable in understanding the pathogenesis of PCNSL.

Application of Immunohistochemistry in the Diagnosis of Non-Hodgkin and Hodgkin Lymphoma

Context.—Beginning with the immunologic classifications of Lukes and Collins and Kiel and culminating in the Revised European-American Lymphoma and World Health Organization classifications, the diagnosis of lymphoid tumors relies heavily on the determination of cell lineage, maturation, and function, based on antigen expression in addition to morphology and clinical features. Technologic advances in immunology, antibody production, genetic analysis, cloning, and the identification of new genes and proteins by microarray and proteomics have provided pathologists with many antibodies to use in routine diagnosis.

Objective.—To provide guidance to the practicing pathologist in the appropriate selection of an antibody panel for the diagnosis of lymphoma based on morphology and relevant clinical data and to avoid pitfalls in the interpretation of immunohistochemical data. Attention is given to some of the newer antibodies, particularly against transcription factors, that are diagnostically and prognostically useful.

Data Sources.—The information presented in this article is based on review of the literature using the OVID database (Ovid MEDLINE 1950 to present with daily update) and 20 years of experience in diagnostic hematopathology.

Conclusions.—Immunophenotyping is required for the diagnosis and classification of lymphoid malignancies. Many paraffin-reactive antibodies are available to the pathologist but most are not specific. To avoid diagnostic pitfalls, interpretation of marker studies must be based on a panel and knowledge of a particular antigen's expression in normal, reactive, and neoplastic conditions.

Nodular lymphocyte-predominant hodgkin lymphoma or T-cell/histiocyte rich large B-cell lymphoma: the problem in "grey zone" lymphomas

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) is a rare indolent B-cell lymphoma. However, its morphology can resemble T-cell/histiocyte rich large B-cell lymphoma (T/HRBCL), a subtype of more aggressive diffuse large B-cell lymphoma. More and more studies suggest that these two entities are closely related. In this report, a 59-year-old man with nodal NLPHL and concomitant T/HRBCL in the bone marrow is presented, the current progress in our understanding of these two closely related B-cell lymphomas reviewed and the problems in the diagnosis and differentiation of NLPHL and T/HRBCL discussed.

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.

Bob-1 is expressed in classic Hodgkin lymphoma

Background

Almost all researchers agree on the lack of Bob-1 expression in Hodgkin/Reed-Sternberg (H/RS) cells in classic Hodgkin lymphoma (CHL), and utilize this marker as a diagnostic tool in conjunction with other markers to differentiate between lymphocyte predominance Hodgkin lymphoma (LPHL) and CHL.

Aim

To study the immunohistochemical (IHC) expression of Bob-1 in Egyptian CHL and to correlate this expression with Epstein-Barr virus (EBV) viral load.

Materials and methods

Paraffin sections of randomly selected 18 CHL cases were included: 2 lymphocyte rich (LR), 4 mixed cellularity (MC), 10 nodular sclerosis (NS) and 2 lymphocyte depletion (LD). All cases were immunostained for Bob-1. EBV was evaluated by EBV early RNA transcripts in situ hybridization (EBER ISH) and immunostaining for EBV latent membrane protein-1 (LMP-1).

Results

Sixty seven percent of cases (12/18) were positive for EBV by ISH and/or immunostaining for LMP-1. Moderate to strong nuclear Bob-1 was observed in 94% of cases. The positivity ranged between 25–100%. Bob-1 immunoreactivity was strongly associated with EBV positivity (p < 0.001).

Conclusion

This study proves nuclear IHC expression of Bob-1 on H/RS in CHL implying the difficulties in applying this marker to differentiate between LPHL and CHL. Does this difference between Western and Egyptian CHL reflect genetic and/or environmental factors, or simply no difference exists as most researchers are concentrated on the Western population and no comparative studies have been done. Studies from other countries might answer this question.

Epidemiology and pathologic features of Hodgkin lymphoma

Hodgkin lymphoma (HL) has unique epidemiologic characteristics. The variation in incidence according to age, sex, race, socioeconomic status, and histologic subtype suggests an etiologic heterogeneity for this tumor. Epidemiologic studies have shown that both genetic and environmental factors play a role in the pathogenesis of HL. HL is one of the Epstein-Barr virus-associated lymphomas, but the oncogenetic mechanism of HL remains to be elucidated. Recent advances in molecular biology have revealed the peculiar nature of the nodular lymphocyte predominant subtype, and as a result this disease is separated from classic types of HL in the new World Health Organization classification. Reed-Sternberg (RS) cells and lymphocytic and/or histiocytic (L&H) cells originate from germinal center B-cells. Loss of the B-cell phenotype due to down-regulation of several B-cell-specific transcription factors is characteristic of RS cells in classic HL.

B-cell posttransplant lymphoproliferative disorders in heart and/or lungs recipients: clinical and molecular-histogenetic study of 17 cases from a single institution

BACKGROUND

Posttransplantation lymphoproliferative disorders (PTLDs) are heterogeneous lymphoid proliferations representing a major complication of solid organ transplant. This study details the clinicopathological and molecular features of 17 B-cell PTLDs observed in a single center series of 988 heart and/or lung transplant recipients.

METHODS

Cases were classified according to World Health Organization lymphoma classification and tested for Epstein-Barr Virus (EBV), clonality, histogenetic phenotypic (CD10, Bcl-6, MUM1, CD138), and genotypic (immunoglobulin and BCL-6 genes somatic hypermutation) markers.

RESULTS

This series of 17 PTLDs included: two B-cell monoclonal polymorphic PTLDs and 15 B-cell monomorphic PTLDs (13 diffuse large B-cell lymphomas [DLBCL] and 2 Burkitt lymphomas [BL]). EBV was detected in 9/17 cases. A monoclonal immunoglobulin variable (IGV) genes rearrangement was documented in 17/17 cases; IGV somatic hypermutation was found in 88% of cases, indicating a prevalent origin from germinal center (GC)-experienced B cells. Using immunophenotypic markers, three histogenetic profiles were identified: a) CD10/bcl-6/MUM1/CD138, mimicking GC B-cells; b) CD10-/bcl-6+/MUM1+/CD138-, reminiscent of B-cells at the latest phases of GC reaction; and c) CD10-/bcl-6-/MUM1+/CD138+/-, consistent with preterminally differentiated B-cells.

CONCLUSIONS

Correlation between morphology, histogenesis, and EBV status demonstrated a high degree of homogeneity in the two GC-related groups, mostly including EBV-negative cases with BL and DLBCL-centroblastic features; the third group, consisting of post GC EBV-positive cases, was histologically less homogeneous, as it included polymorphic PTLDs and DLBCL with immunoblastic and anaplastic features. The EBV-negative cases with GC histogenetic phenotype showed a slightly better outcome; however, such less aggressive prognostic trend was not confirmed by statistical analysis.

Pathobiology of Classical Hodgkin Lymphoma

The World Health Organization has acknowledged the malignant nature of classical Hodgkin lymphoma (cHL), which encompasses four histological subtypes. The diagnosis of cHL is based on the detection of malignant Hodgkin and Reed-Sternberg cells (HRSC) confirmed by immunophenotyping and the detection of growth patterns specific to each histological subtype. The pathologic HRSC arise from germinal center or immediate postgerminal cells that lack detectable immunoglobulin/B-cell antigen receptor expression, with a consequent loss of B-cell identity; very few cHL cases are of T-cell origin. To escape apoptosis, which normally occurs in B cells with nonfunctioning antigen receptor machinery, HRSC develop concurrent antiapoptotic mechanisms by activation of nuclear factor-kappaB or are rescued by Epstein-Barr virus infection. HRSC are characterized by a variable and inconstant immunophenotype, with a remarkable loss of lineage-specific cell antigens and expression of antigens of other cell lineages. The master plan of B-cell identity in HRSC is disturbed not only at the immunoglobulin expression level, but also at the transcriptional factor level. HRSC are further characterized by profound cell cycle deregulation with futile replication, multinucleation and poly- and aneuploidy. Here, we review pathobiological aspects of cHL with respect to lymphomagenesis and routine diagnostics.

Leukotriene A4 hydrolase expression in PEL cells is regulated at the transcriptional level and leads to increased leukotriene B4 production

Primary effusion lymphoma (PEL) is a herpesvirus-8-associated lymphoproliferative disease characterized by migration of tumor cells to serous body cavities. PEL cells originate from postgerminal center B cells and share a remarkable alteration in B cell transcription factor expression and/or activation with classical Hodgkin's disease cells. Comparative analysis of gene expression by cDNA microarray of BCBL-1 cells (PEL), L-428 (classical Hodgkin's disease), and BJAB cells revealed a subset of genes that were differentially expressed in BCBL-1 cells. Among these, four genes involved in cell migration and chemotaxis were strongly up-regulated in PEL cells: leukotriene A4 (LTA4) hydrolase (LTA4H), IL-16, thrombospondin-1 (TSP-1), and selectin-P ligand (PSGL-1). Up-regulation of LTA4H was investigated at the transcriptional level. Full-length LTA4H promoter exhibited 50% higher activity in BCBL-1 cells than in BJAB or L-428 cells. Deletion analysis of the LTA4H promoter revealed a positive cis-regulatory element active only in BCBL-1 cells in the promoter proximal region located between -76 and -40 bp. Formation of a specific DNA-protein complex in this region was confirmed by EMSA. Coculture of ionophore-stimulated primary neutrophils with BCBL-1 cells leads to an increased production of LTB4 compared with coculture with BJAB and L-428 cells as measured by enzyme immunoassay, demonstrating the functional significance of LTA4H up-regulation.

Expression profiling of transcription factors Pax-5, Oct-1, Oct-2, BOB.1, and PU.1 in Hodgkin's and non-Hodgkin's lymphomas: a comparative study using high throughput tissue microarrays

Analysis of B-cell-specific transcription factors is useful in understanding of the differentiation-linked phenotype in Hodgkin's as well as in non-Hodgkin's lymphomas. We analyzed the expression profiling of transcription factors Pax-5, Oct-1, Oct-2, BOB.1, and PU.1 in 109 cases, including non-Hodgkin's lymphomas of B- and T-lineage, classical Hodgkin's lymphomas, and nodular lymphocyte predominant Hodgkin's lymphomas. Our study revealed that all transcription factors were universally expressed in all cases of nodular lymphocyte predominant Hodgkin's and variably expressed in non-Hodgkin's lymphomas of B-lineage. Cases of classical Hodgkin's lymphoma variably expressed the Pax-5, Oct-1, Oct-2, and BOB.1. However, in contrast to nodular lymphocyte predominant Hodgkin's lymphoma, the transcription factor PU.1 was consistently absent in all cases of classical Hodgkin's lymphoma. Transcription factors Pax-5, BOB.1, and PU.1 were not detectable in cases of anaplastic large cell lymphoma. However, the Oct-1 was detected in all anaplastic large cells lymphoma cases, indicating that expression of this transcription factor was not restricted to B-lineage lymphoid malignancies. Our findings suggest that inclusion of the PU.1 antibody may prove useful in separating classical Hodgkin's lymphomas from nodular lymphocyte predominant Hodgkin's lymphomas in problematic cases.

IgD Positive L&H Cells Identify a Unique Subset of Nodular Lymphocyte Predominant Hodgkin Lymphoma

Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is a rare B-cell lymphoma considered to be of germinal center (GC) derivation. Studies on immunoglobulin expression have been few, and post-switch immunoglobulin (IgG) has been identified in the majority of cases examined thus far. We reviewed 180 cases of NLPHL and observed the unexpected expression of IgD in 27% of cases. IgD is usually coexpressed with IgM in naive B cells but can also be seen as IgD-only in centroblasts (CD38-positive) or memory B cells (CD27-positive). We asked whether IgD-positive NLPHL differed from cases of NLPHL negative for IgD. Clinically, the IgD-positive cases presented at a younger median age (21 vs. 44 years) and had a striking male predominance (male-to-female ratio, 23:1 vs. 1.5:1). Cervical lymph nodes were more frequently involved (56% vs. 18.2%). L&H cells were localized in a predominantly extrafollicular distribution in the majority of IgD-positive cases (69%). The IgD-positive cases did not coexpress IgM or CD27 (a marker associated with memory B cells), and nearly all (93%) were weakly positive for CD38, supporting a GC derivation. The expression of Bcl-6, BOB.1, Oct2, and SWAP-70 was similar in the two groups. However, PU.1 expression was seen in 60% of the IgD-positive cases in contrast to 86% of the IgD-negative cases. The absence of PU.1 staining correlated with more L&H cells in an extrafollicular distribution, weakening the use of this marker in the differential diagnosis with T-cell rich/histiocyte rich B-cell lymphomas. To study IgD expression in "de-novo" T-cell rich/histiocyte rich B-cell lymphomas, we analyzed 20 cases and all but one were negative. In conclusion, cases of IgD-positive NLPHL do not differ from IgD-negative cases regarding cellular derivation and most other immunophenotypic characteristics. However, IgD-positive NLPHL exhibits distinctive clinical features, and more often involves the interfollicular region in a background relatively rich in T cells. IgD positivity may represent an additional useful marker in the diagnosis of NLPHL.