The Reed-Sternberg cell in classical Hodgkin's disease

A Review of the Flow Cytometric Findings in Classic Hodgkin Lymphoma, Nodular Lymphocyte Predominant Hodgkin Lymphoma and T Cell/Histiocyte-Rich Large B Cell Lymphoma

Classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, and T cell/histiocyte-rich large B cell lymphoma form a unique set of lymphomas with similar morphologic growth patterns (occasional neoplastic cells within a prominent cellular cell background) that are pathobiologically related. Distinguishing these entities has been historically difficult by flow cytometry; however, our laboratory has developed antibody-fluorochrome combinations capable of immunophenotyping these lymphomas. Additionally, characterization of the background reactive lymphocytes can aid in narrowing the differential diagnosis. This review summarizes the immunophenotypic features and insights of the neoplastic and reactive populations found in this unique group of lymphomas.

Machine learning in computational histopathology: Challenges and opportunities

Digital histopathological images, high-resolution images of stained tissue samples, are a vital tool for clinicians to diagnose and stage cancers. The visual analysis of patient state based on these images are an important part of oncology workflow. Although pathology workflows have historically been conducted in laboratories under a microscope, the increasing digitization of histopathological images has led to their analysis on computers in the clinic. The last decade has seen the emergence of machine learning, and deep learning in particular, a powerful set of tools for the analysis of histopathological images. Machine learning models trained on large datasets of digitized histopathology slides have resulted in automated models for prediction and stratification of patient risk. In this review, we provide context for the rise of such models in computational histopathology, highlight the clinical tasks they have found success in automating, discuss the various machine learning techniques that have been applied to this domain, and underscore open problems and opportunities.

A comparison and review of the flow cytometric findings in classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma

The "Hodgkin-like" lymphomas including classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, T cell/histiocyte rich large B cell lymphoma, and primary mediastinal large B cell lymphoma have been shown to be pathobiologically related. With the exception of primary mediastinal large B cell lymphoma, these lymphomas have similar morphologic growth patterns with occasional neoplastic cells within a prominent reactive cell background. Historically, distinguishing these entities was difficult by flow cytometry; however, over the past 15 years, our laboratory has developed antibody-fluorochrome combinations capable of accurately distinguishing these entities by their immunoprofile. Additionally, an algorithmic approach based on characterization of the background reactive B-cell and T-cell populations can aid in narrowing the differential diagnosis. This review summarizes both the morphologic and immunophenotypic features and the current flow cytometric insights of the neoplastic and reactive populations found in this unique subset of lymphomas.

Mediastinal Lymphoproliferative Disorders

Lymphoproliferative disorders comprise 50% to 60% of all mediastinal malignancies in both children and adults. Primary mediastinal involvement is rare (∼5%), whereas secondary mediastinal involvement by systemic disease is more common (10% to 25%). Primary mediastinal disease is defined as involvement by a lymphoproliferative disorder of mediastinal lymph nodes, the thymus, and/or extranodal mediastinal organs without evidence of systemic disease at presentation. In this review, the clinical, radiologic, histopathologic, immunohistochemical, and genetic features of some of the most characteristic mediastinal lymphoproliferative disorders are presented. The entities discussed here include: classic Hodgkin lymphoma with emphasis on nodular sclerosis and mixed cellularity types, and non-Hodgkin lymphomas, including primary mediastinal (thymic) large B-cell lymphoma, mediastinal gray zone lymphoma, mediastinal diffuse large B-cell lymphoma, thymic marginal zone lymphoma, mediastinal plasmacytoma, T-lymphoblastic lymphoma, and anaplastic large cell lymphoma. Although not a malignant process, hyaline vascular Castleman disease is also discussed here as this disorder commonly involves the mediastinum. Despite multiple advances in hematopathology in recent decades, the day-to-day diagnosis of these lesions still requires a morphologic approach and a proper selection of immunohistochemical markers. For this reason, it is crucial for general pathologists to be familiar with these entities and their particular clinicoradiologic presentation.

Hodgkin Reed-Sternberg-Like Cells in Non-Hodgkin Lymphoma

Reed-Sternberg cells (RSCs) are hallmarks of classic Hodgkin lymphoma (cHL). However, cells with a similar morphology and immunophenotype, so-called Reed-Sternberg-like cells (RSLCs), are occasionally seen in both B cell and T cell non-Hodgkin Lymphomas (NHLs). In NHLs, RSLCs are usually present as scattered elements or in small clusters, and the typical background microenviroment of cHL is usually absent. Nevertheless, in NHLs, the phenotype of RSLCs is very similar to typical RSCs, staining positive for CD30 and EBV, and often for B cell lineage markers, and negative for CD45/LCA. Due to different therapeutic approaches and prognostication, it is mandatory to distinguish between cHL and NHLs. Herein, NHL types in which RSLCs can be detected along with clinicopathological correlation are described. Moreover, the main helpful clues in the differential diagnosis with cHL are summarized.

Immunophenotypic Characterization and Purification of Neoplastic Cells from Lymph Nodes Involved by T-Cell/Histiocyte-rich Large B-cell Lymphoma by Flow Cytometry and Flow Cytometric Cell Sorting

BACKGROUND

T-cell/histiocyte rich large B-cell lymphoma (THRLBCL) is B-cell lymphoma in which rare neoplastic cells are embedded in a reactive infiltrate. We describe the first characterization of the neoplastic cells by flow cytometry (FC).

METHODS

Using FC, we immunophenotyped the neoplastic cells of 11 cases of THRLBCL and 11 cases of DLBCL, NOS (controls). Neoplastic THRLBCL cells were also purified by flow cytometric cell sorting (FCCS).

RESULTS

A neoplastic THRLBCL population was detected by FC in 9 of 11 cases (82%). Neoplastic THRLBCL cells demonstrated an aberrant germinal center B-cell immunophenotype (bright CD20, bright CD40; positive for Bcl-6 and CD75; weakly positive for CD32; negative for IgH). With regard to adhesion molecules, CD54 was overexpressed, CD58 expression varied between cases, and CD50 expression was intermediate. Evaluation of immunomodulatory receptors demonstrated that PD-L2 was weakly expressed and PD-L1 was variably expressed. Finally, FCCS of two cases showed large multi-lobated cells with morphology consistent with neoplastic cells of THRLBCL.

CONCLUSIONS

The immunophenotype identified and the morphology of the FCCS purified cells confirms the FC defined populations are neoplastic cells from THRLBCL. While the cohort is small, neoplastic THRLBCL cells lack surface immunoglobulins. CD40, CD50, and CD54 were overexpressed in THRLBCL relative to DLBCL, NOS, perhaps contributing to the predominance of T cells in THRLBCL. Expression of CD32, PD-L1, and PD-L2 may be useful in distinguishing THRLBCL and NLPHL. Finally, the FC assays will be useful for purifying neoplastic cells of THRLBCL and for diagnostic immunophenotyping of THRLBCL. © 2019 International Clinical Cytometry Society.

Flow Cytometry for Non-Hodgkin and Hodgkin Lymphomas

Multiparametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes a general approach for the identification of abnormal lymphoid populations by flow cytometry, including B, T, NK, and Hodgkin lymphoma cells suitable for the clinical and research environment. Knowledge of the common patterns of antigen expression of normal lymphoid cells is critical to permit identification of abnormal populations at disease presentation and for minimal residual disease assessment. We highlight an overview of procedures for processing and immunophenotyping non-Hodgkin B- and T-cell lymphomas and also describe our strategy for the sensitive and specific diagnosis of classical Hodgkin lymphoma and nodular lymphocyte predominant Hodgkin lymphoma.

Primary Mediastinal Classical Hodgkin Lymphoma

Primary mediastinal Classical Hodgkin lymphoma (CHL) is rare. Nodular sclerosis CHL (NS-CHL) is the most common subtype involving the anterior mediastinum and/or mediastinal lymph nodes. Primary thymic CHL is exceedingly rare. The disease typically affects young women and is asymptomatic in 30% to 50% of patients. Common symptoms include fatigue, chest pain, dyspnea and cough, but vary depending on the location and size of the tumor. B-symptoms develop in 30% of cases. By imaging, primary mediastinal CHL presents as mediastinal widening/mediastinal mass that does not invade adjacent organs but may compress vital structures as bulky disease. Histopathology is the gold standard for diagnosis. Primary mediastinal NS-CHL consists of nodules of polymorphous inflammatory cells surrounded by broad fibrous bands extending from a thickened lymph node capsule. The cellular nodules contain variable numbers of large Hodgkin/Reed-Sternberg cells, required for diagnosis. Primary thymic CHL may exhibit prominent cystic changes. The histopathologic recognition of NS-CHL can be challenging in cases with prominent fibrosis, scant cellularity, artifactual cell distortion, or an exuberant granulomatous reaction. The differential diagnosis includes primary mediastinal non-HLs, mediastinal germ cell tumors, thymoma, and metastatic carcinoma or melanoma to the mediastinum. Distinction from primary mediastinal non-HLs is crucial for adequate therapeutic decisions. Approximately 95% of patients with primary mediastinal CHL will be alive and free of disease at 10 years after treatment with short courses of combined chemoradiotherapy. In this review, we discuss the history, classification, epidemiology, clinicoradiologic features, histopathology, immunohistochemistry, differential diagnosis, and treatment of primary mediastinal CHL.

Computer-aided detection of rare tumor populations in flow cytometry: an example with classic Hodgkin lymphoma

OBJECTIVES

Diagnosing classical Hodgkin lymphoma (cHL) by flow cytometry (FC) relies on an observer gating rare populations of Hodgkin/Reed Sternberg (HRS) cells. Here, we apply machine-learning methods to aid in the detection of rare tumor cell populations using data derived from clinical FC analysis of cHL as a model disease.

METHODS

FC data from 144 clinical cases using a nine-color FC reagent panel were analyzed using Python 2.7 and the "scikit-learn" module.

RESULTS

Seventy-eight 50 × 50 two-dimensional histograms were generated from routine FC data and a reciprocal power function applied to favor rare events. Data were classified by support vector machine (SVM), gradient boosting, and random forest classifiers. All three classifiers showed no statistical difference in performance, with 89%-92% accuracy on cross-validation. Nearly all classifiers misclassified the same set of cases, with more false-positive than false-negative cases. Dimensionality reduction by ensemble methods selected for data points in a CD5+/ CD40+/CD64- region.

CONCLUSIONS

All classifiers provide probabilistic confidences for each result, and diagnostic cutoffs can be chosen to minimize false negatives and serve as a screening tool. Computational exclusion of manually gated HRS cells had little impact on the overall performance of selected support vectors in SVM or dimensionality reduction, suggesting that features of the immune response in cHL may dictate the method accuracy. We hypothesize there are distinct inflammatory cells that suggest cHL.

Non-AIDS-Defining Malignancies in the HIV-Infected Population

With the advent of effective combination antiretroviral therapy, HIV infection has been transformed from a fatal disease to a chronic condition. There is renewed clinical interest in long-term morbidities, including malignancies that occur disproportionately within this population. Non-AIDS-defining cancers (NADCs) are a significant source of morbidity and mortality in the aging HIV-infected population. There are data to suggest that incidence rates are elevated among HIV-infected individuals for many cancer sites, particularly those with a confirmed or suspected infectious etiology. The complex interplay between behavioral risk factors, coexistence of viral infections, immunodeficiency and antiretroviral therapy makes it difficult to analyze why certain cancers develop more frequently in HIV-infected individuals. The challenge to clinicians caring for HIV-infected patients is to develop and implement effective means to screen, treat, and prevent NADCs in the future. This review presents data on whether NADCs are increased in the HIV-Infected population, as well as ongoing research on epidemiology, prevention and pathogenesis of this evolving aspect of the HIV epidemic.

A six-color flow cytometry assay for immunophenotyping classical Hodgkin lymphoma in lymph nodes

OBJECTIVES

We have recently demonstrated that classical Hodgkin lymphoma (CHL) can be immunophenotyped by flow cytometry (FC), thus obviating the need for immunohistochemistry in many cases. The previously described nine-color assay, however, cannot be used by laboratories that do not have access to a nine- or ten-color flow cytometer. Therefore, a six-color FC tube was designed employing the following combination: CD64-FITC/CD30-PE/CD40-PeCy5.5/CD20-PECy7/CD95-APC/CD3-APC-H7.

METHODS

To validate this assay, we analyzed 408 tissue specimens (including 55 CHL cases, 26 of which had been previously cryopreserved). Specimen inclusion criteria included the identification of an abnormal population by FC or (if no abnormal population was identified) greater than 50,000 viable events and specimen age less than 4 days. All FC studies were examined blinded to any clinical, laboratory, or histologic information.

RESULTS

The diagnostic sensitivity and specificity of the six-color FC assay was 85.4% and 99.7%, respectively.

CONCLUSIONS

Taken together, these results suggest that the six-color FC assay has acceptable sensitivity and specificity for clinical use, allowing more FC laboratories to immunophenotype CHL by this method.

Flow cytometry for non-Hodgkin and classical Hodgkin lymphoma

Multiparametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes a general approach for the identification of abnormal lymphoid populations by flow cytometry, including B, T, and Hodgkin lymphoma cells suitable for the clinical and research environment. Knowledge of the common patterns of antigen expression of normal lymphoid cells is critical to permit identification of abnormal populations at disease presentation and for minimal residual disease assessment. We highlight an overview of procedures for processing and immunophenotyping non-Hodgkin B- and T-cell lymphomas and also describe our strategy for the sensitive and specific diagnosis of classical Hodgkin lymphoma.

Strategies for immunophenotyping and purifying classical Hodgkin lymphoma cells from lymph nodes by flow cytometry and flow cytometric cell sorting

Flow cytometry is an established technique to immunophenotype hematopoietic neoplasms. While the diagnosis of classical Hodgkin lymphoma (CHL) has commonly been made using paraffin sections, we have recently demonstrated that the neoplastic Hodgkin and Reed-Sternberg (HRS) cells of CHL can be identified by flow cytometry. Using 6- and 9-color flow cytometric assays, CHL can be immunophenotyped with 85-90% sensitivity and nearly 100% specificity. Analysis of this data requires using established gating strategies to help in the identification of putative HRS cell populations. Interestingly, HRS cells bind to reactive T cells (HRS-T cell rosetting) and this phenomenon can be identified and utilized diagnostically by flow cytometry. In addition, the reactive T cells of CHL show characteristic immunophenotypic changes by flow cytometry and these changes can suggest a diagnosis of CHL. Finally, these principles can be employed to rapidly purify HRS cells using flow cytometric cell sorting. This manuscript provides experimental protocols for immunophenotyping CHL by flow cytometry as well as purifying the HRS cells via flow cytometric cell sorting.

Multi-drug resistance 1 genetic polymorphism and prediction of chemotherapy response in Hodgkin's Lymphoma

Background

The human multi-drug resistance gene (MDR1), which encodes the major trans-membrane transporter P-glycoprotein (P-gp), was found to be associated with susceptibility to cancer and response to chemotherapy. The C3435T Polymorphism of MDR1 gene was correlated with expression levels and functions of P-gp. Here, we studied the association between MDR1 C3435T polymorphism and susceptibility to Hodgkin lymphoma (HL) and patient's response to ABVD chemotherapy regimen.

Methods

a total of 130 paraffin embedded tissue samples collected from HL patients were analyzed to identify the C3435T polymorphism. As a control group, 120 healthy subjects were enrolled in the study. The C3435T Polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) method. Data analysis was carried out using the statistical package SPSS version 17 to compute all descriptive statistics. Chi-square and Fisher exact tests were used to evaluate the genotype distribution and allele frequencies of the studied polymorphism.

Results

these studies revealed that the frequency of T allele was significantly higher in HL patients compared to the controls (P < 0.05). In addition, the frequency of CT and TT genotypes were also significantly higher in HL patients compared to the controls (P < 0.05). No association between C3435T polymorphism and response to ABVD was detected among HL patients (P > 0.05).

Conclusions

these results suggest that MDR1 C3435T polymorphism might play a role in HL occurrence; however this polymorphism is not correlated with the clinical response to ABVD.

Involvement of human herpesvirus-6 variant B in classic Hodgkin's lymphoma via DR7 oncoprotein

PURPOSE

Hodgkin's lymphoma (HL) is associated with the presence of EBV in Reed-Sternberg (RS) cells in ∼40% of cases. Here, we studied the presence of human herpesvirus type 6 (HHV-6) variant B in RS cells of HL patients and correlated results with clinical parameters. We then examined the implication of HHV-6 DR7B protein in cell deregulation.

EXPERIMENTAL DESIGN

HHV-6 DR7B protein was produced in a Semliki Forest virus system. Polyclonal antibodies were then generated and used for immunochemical HHV-6 localization in HL biopsies. Binding between DR7B and p53 was studied using a double-hybrid system. Transactivation of NFκB was observed after transient transfection using reporter gene assays. We looked for Id2 factor expression after stable transfection of the BJAB cell line by reverse transcription-PCR and Western blot analysis.

RESULTS

HHV-6 was more common in nodular sclerosis subtype HL, and DR7B oncoprotein was detected in RS cells for 73.7% of EBV-negative patients. Colocalization of EBV and HHV-6 was observed in RS cells of doubly infected patients. DR7B protein bound to human p53 protein. p105-p50/p65 mRNA expression and activation of the NFκB complex were increased when DR7B was expressed. Stable expression of DR7B exhibited a strong and uniform expression of Id2. A slightly higher percentage of remission was observed in patients with RS cells testing positive for DR7B than in those testing negative.

CONCLUSIONS

Collectively, these data provide evidence for the implication of a novel agent, HHV-6, in cases of nodular sclerosis HL.

Flow cytometric analysis of CD123 is useful for immunophenotyping classical Hodgkin lymphoma

Although the diagnosis of classical Hodgkin lymphoma (CHL) is traditionally made morphologically in tissue sections, it is now possible to diagnose CHL by flow cytometry (FC). In an effort to identify additional antigens on Hodgkin and Reed-Sternberg (HRS) cells that might be useful for immunophenotyping this lymphoma by FC, we examined the expression of CD123 (α chain of the IL-3R) on HRS cells and compared this with the expression of CD123 in other lymph node samples (372 tissue specimens, including 98 reactive and 274 neoplastic cases), using a nine-color FC reagent combination including anti-CD123. CD123 was found to be expressed on the majority of HRS cell populations (59% of 59 CHL lymph nodes examined), rarely on B-cell non-Hodgkin lymphomas (NHLs) (3 of 3 hairy cell leukemia cases, 3 of 29 chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) cases, 1 of 55 large B-cell lymphoma cases, but not on 95 other B-cell NHL examined), and in none of the 16 T-cell NHL cases examined. In reactive lymph nodes, CD123 expression was largely limited to plasmacytoid dendritic cells and rare histiocyte populations that can readily be distinguished from HRS populations. As the expression of this antigen is shown to be relatively limited in B- and T-NHL and in reactive lymph node populations, assessment of CD123 expression is useful for supporting the FC diagnosis of CHL.

Antigen-specific cytotoxic T lymphocytes can target chemoresistant side-population tumor cells in Hodgkin lymphoma

Side-population (SP) analysis has been used to identify progenitor cells from normal and malignant tissues as well as revealing tumor cells with increased resistance to radiation and chemotherapy. Despite enhanced chemoresistance, tumor SP cells may still express tumor-associated antigens (TAAs), which may render them susceptible to elimination by the immune system. In this study, we show that both Hodgkin lymphoma (HL) cell lines and primary HL tumor samples contain a distinct SP phenotype. Importantly, while these cells showed increased resistance to gemcitabine, a commonly used drug for the treatment of refractory HL, HL SP cells also expressed higher levels of the TAAs MAGEA4, SSX2, survivin, and NY-ESO-1, which allowed them to be specifically recognized and killed by TAA-specific cytotoxic T lymphocytes. This study suggests that chemoresistant HL SP cells can be targeted by the immune system, providing a rationale for combined chemotherapy and immunotherapy for the treatment of 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.

Flow cytometry can diagnose classical hodgkin lymphoma in lymph nodes with high sensitivity and specificity

The diagnosis of classical Hodgkin lymphoma (CHL) has been made in tissue sections as attempts to identify neoplastic Hodgkin and Reed Sternberg (HRS) cells in lymph nodes by flow cytometry (FC) have been unsuccessful. However, we have recently demonstrated that HRS cells can be identified by FC, often present as T-cell-HRS-cell rosettes. In this study, we examined the usefulness of a novel 9-color (CD95-Pacific blue/CD64-fluorescein isothiocyanate/CD30-phycoerythrin [PE]/CD45-PE-Texas red/CD40-PE cyanine [Cy]5.5/CD20-PECy7/CD15-allophycocyanin [APC]/CD71-APC-AlexaFluor A700/CD5-APC-Cy7), single tube FC assay to diagnose CHL in lymph nodes. We used the FC assay to determine diagnostic sensitivity and specificity in 279 blindly identified and 141 selected (for specimen type or cytopreparation morphologic features suggesting CHL) tissues. Of the 53 morphologically defined CHL cases identified (10 in the unselected group; 43 in the selected group), the FC assay diagnostic sensitivity and specificity were 88.7% and 100%, respectively. With the current availability of 8 (or more) color clinical flow cytometers, this assay can now be applied to routinely immunophenotype and confirm a diagnosis of CHL or as an adjunct to immunohistochemical analysis.

Serum chemokine levels in Hodgkin lymphoma patients: highly increased levels of CCL17 and CCL22

Hodgkin lymphoma (HL) is characterized by a minority of neoplastic Hodgkin-Reed Sternberg (HRS) cells surrounded by a non-neoplastic reactive infiltrate. As immunological mechanisms appear to be crucial in classical HL pathogenesis, altered serum chemokine levels might be related to disease activity. Serum levels of nine chemokines were examined in 163 untreated HL patients and 334 controls. We investigated single nucleotide polymorphisms (SNPs) for association with serum CCL17 (thymus and activation-regulated chemokine, TARC) levels and HL susceptibility. Serum CCL17 and CCL22 (macrophage-derived chemokine, MDC) levels were significantly increased in 82% and 57% of the HL patients. Nodular sclerosis cases showed increased serum CCL17 and CCL22 levels (P < 0.001) and serum levels were correlated with Ann Arbor stage. Of nine patients with pre- and post-treatment serum samples, the majority showed decreased CCL17 and CCL22 levels after treatment. HRS cells expressed CCL17 and CCL22 in 77% and 75% of 74 cases. Three SNPs showed a trend of increased serum CCL17 levels with minor alleles in controls, but were not associated with HL susceptibility. CCL17 and CCL22 were the only chemokines with increased serum levels in the vast majority of HL patients, which provides further insight into the molecular mechanism(s) leading to infiltrations of reactive lymphocytes in HL.

The human leukocyte antigen class I region is associated with EBV-positive Hodgkin's lymphoma: HLA-A and HLA complex group 9 are putative candidate genes

Various studies have indicated that the human leukocyte antigen (HLA) region is associated with Hodgkin's lymphoma. We recently showed a specific association of the HLA class I region with EBV-positive Hodgkin's lymphoma cases. One haplotype of two consecutive microsatellite markers (D6S265 and D6S510) was overrepresented in the patient group, whereas another haplotype was underrepresented. Here, we did fine mapping of this region of approximately 400 kb as a next step to find the causative single-nucleotide polymorphism(s) (SNP). To select candidate SNPs for screening the total study population, several known SNPs were determined by sequencing two individuals homozygous for either of the above-mentioned associated haplotypes. Seven SNPs displayed different alleles in these two individuals and were therefore analyzed in the total study population, including 238 Hodgkin's lymphoma patients and 365 family-based controls. All seven SNPs showed significant association with the EBV-positive patient group. Two of these SNPs were analyzed in a Scottish Hodgkin's lymphoma population and revealed significant associations as well. The associated SNPs are located nearby two putative candidate genes: HLA-A and HLA complex group 9. HLA-A represents the most interesting target because of its consistent expression in EBV-positive Hodgkin's lymphoma cases and its ability to present EBV-derived peptides to cytotoxic T cells.

Hodgkin lymphoma and immunodeficiency in persons with HIV/AIDS

In persons with HIV/AIDS (PWHAs), Hodgkin lymphoma (HL) risk is increased. However, HL incidence in PWHAs has unexpectedly increased since highly active antiretroviral therapy (HAART) was introduced. We linked nationwide HIV/AIDS and cancer registry data from 1980 through 2002. Immunity was assessed by CD4 T-lymphocyte counts at AIDS onset. Annual HL incidence rates were calculated for 4 through 27 months after AIDS onset. During 477 368 person years (py's) of follow-up in 317 428 persons with AIDS (PWAs), 173 HL cases occurred (36.2 per 10(5) py's). Incidence was significantly higher in 1996 to 2002 than earlier. Incidence in PWAs with 150 to 199 CD4 cells/muL was 53.7 per 10(5) py's, whereas in PWAs with fewer than 50 CD4 cells/muL, it was 20.7 per 10(5) py's (P(trend) = .002). For each HL subtype, incidence decreased with declining CD4 counts, but nodular sclerosing decreased more precipitously than mixed cellularity, thereby increasing the proportion of mixed cellularity HL seen in PWAs. We conclude that HL incidence is lower with severe immunosuppression than with moderate immunosuppression, and HAART-related improvements in CD4 counts likely explain the increasing HL incidence in PWHAS observed since 1996. With more severe immunosuppression, nodular sclerosing HL becomes infrequent, explaining the higher proportion of mixed cellularity HL found in PWAs. Pathogenesis implications are discussed.

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.

Alterations of loci encoding PU.1, BOB1, and OCT2 transcription regulators do not correlate with their suppressed expression in Hodgkin lymphoma

Neoplastic cells of Hodgkin lymphoma (HL) originating from germinal or postgerminal center B cells lose their capacity to transcribe and to express surface immunoglobulins (Ig). This defect correlates with the absence of expression of B-cell-specific transcription regulators, including PU.1, BOB1, and OCT2. These findings suggest that Ig impairment in HL is caused by the defective transcription machinery. The mechanism or mechanisms underlying failure of Hodgkin cells to express PU.1, BOB1, and OCT2 remain unclear. The genes encoding for these three respective transcription factors have been mapped at 11p11.2 (SPI1), 11q23.1 (POU2AF1), and 19q13.2 (POU2F2); these are chromosomes recurrently affected in HL. To check the genomic status of PU.1, BOB1, and OCT2 in HL, we performed metaphase fluorescence in situ hybridization (FISH) analysis of 10 HL cases using locus-specific bacterial artificial chromosome clones. FISH signal pattern was correlated with the ploidy level of each analyzed cell and showed recurrent imbalances of the studied loci. The underrepresentation of one or two analyzed regions was detected in five cases; the remaining five cases showed either random losses, a ploidy-equivalent FISH pattern, or overrepresented signals. Neither a constant loss nor genomic aberration of at least one of these genes could be observed in studied cases. These findings indicate that genomic imbalances or rearrangements are not a cause of PU.1, BOB1, and OCT2 deficiency in cHL and argue for another mechanism underlying this phenomenon.

Aberrant expression of cell cycle regulators in Hodgkin and Reed-Sternberg cells of classical Hodgkin's lymphoma

The characteristic Hodgkin and Reed-Sternberg cells of classical Hodgkin's lymphoma, although highly positive for proliferation markers, do not accumulate to excessive cell numbers. These cells are characterized by abortive mitotic cycles, leading to multinucleation or cell death in mitosis. We have previously described high expression of G1-phase cyclins in classical Hodgkin's lymphoma, which could explain the high percentage of cells staining for proliferation markers. To further our understanding of proliferation control in classical Hodgkin's lymphoma, we extended our immunohistochemical analysis to the main S-phase cyclin, cyclin A, and its regulators p21CIP1 and p27KIP1. Expression of proliferating cell nuclear antigen (PCNA) was used as an additional marker for cells being in either S- or G2-phase. In 47% (112/239) of classical Hodgkin's lymphoma cases p21CIP1 was detected within a mean frequency of 15% positive Hodgkin's and Reed-Sternberg cells per case. Similarly, 47% (116/249) of the cases stained positively for p27KIP1 with a mean frequency of expression in Hodgkin's and Reed-Sternberg cells of 12%. In contrast, 90% of the cells in all 246 evaluable classical Hodgkin's lymphoma cases were positive for PCNA. In addition, 98% of Hodgkin's and Reed-Sternberg cells in 99% (250/253) of the cases stained strongly positive for cyclin A. These findings further corroborate the hypothesis that Hodgkin and Reed-Sternberg cells exhibit a disturbed cell cycle with an abnormally short or even absent G1-phase. In contrast to other tumors, expression of PCNA or cyclin A had no prognostic value for patient survival.

Development of CD30+ lymphoproliferative disease in mice lacking interferon regulatory factor-1

Human lymphomas continue to represent a major challenge in oncology, and in particular occur at very high frequencies in AIDS patients. We report here the development of a CD30+ lymphoproliferative disease in mice lacking the proapoptotic transcription factor, interferon regulatory factor-1. These mice most closely represent a model of human anaplastic large-cell lymphoma (ALCL). This mouse model of lymphoma will likely be useful in understanding the development of ALCL and in understanding the development of other closely related CD30+ forms of lymphoma, such as CD30+ Hodgkin's disease and CD30+ cutaneous T-cell lymphoma. This mouse model will also be useful in testing therapies for different forms of CD30+ lymphoma, in particular anti-CD30-based therapies.

Disruption of the B-cell specific transcriptional program in HHV-8 associated primary effusion lymphoma cell lines

Primary effusion lymphoma (PEL) is a lymphoproliferative disease of B-cell origin that is associated with HHV-8 infection. PEL cells harbor a non-B, non-T phenotype and lack significant surface immunoglobulin (Ig) expression, a characteristic that has not been fully explained. In the present study, we demonstrate that PEL cells constitutively express interferon regulatory factor (IRF)-4, a transcription factor that regulates the activity of the immunoglobulin light-chain enhancer elements lambdaB and kappaE3' through binding to a composite Ets-IRF site. IRF-4 activity requires its physical interaction with PU.1, an Ets family member involved in the activation of genes essential for B-cell development. However, in PEL-derived B-cell lines, PU.1 expression was completely abrogated; expression of the B cell specific transcription factor Oct-2, which is known to regulate PU.1 expression, was also abolished. Moreover, the B-cell-specific coactivator of octamer factors, BOB-1/OcaB, was expressed at very decreased levels in PEL cells. Ectopic expression of Oct-2 was able to fully restore PU.1 promoter activity in the PEL cell line BCBL-1, while PU.1 expression also reconstituted the activity of the lambdaB Ets-IRF site. In addition, protein levels of BSAP/Pax-5 and IRF-8/ICSBP were undetectable in PEL cells. The pattern of transcription factor ablation observed in PEL was found to be comparable to that observed in classical Hodgkin's disease-derived cell lines, which also lack B-cell-specific surface markers. These observations indicate that disruption of the B-cell-specific transcriptional program is likely to contribute to the incomplete B-cell phenotype characteristic of PEL cells.

NF-kappaB activation in cancer: a challenge for ubiquitination- and proteasome-based therapeutic approach

Nuclear factor-kappa B (NF-kappaB) activation relies primarily on ubiquitin-mediated degradation of its inhibitor IkappaB. NF-kappaB plays an important role in many aspects of tumor development, progression, and therapy. Some types of cancer are characterized by constitutive NF-kappaB activity, whereas in others such activity is induced following chemotherapy. NF-kappaB-harboring tumors are generally resistant to chemotherapy and their eradication requires NF-kappaB inhibition. Here we describe the mechanisms of NF-kappaB activation in normal and tumor cells, review prevalent notions regarding the factor's contribution to tumorigenicity and discuss present and future options for NF-kappaB inhibition in cancer. The ubiquitination-mediated activation of NF-kappaB is intersected by another cancer-associated protein, beta-catenin. We, therefore, compare the related activation pathways and discuss the possibility of differential targeting of the involved ubiquitination machinery.

Biology of Hodgkin's lymphoma

Significant progress has been made in recent years in our understanding of the cellular origin of Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's lymphoma (HL). It is now clear that in most instances HRS cells represent clonal populations of transformed germinal centre (GC) B cells. While the tumour cells in the lymphocyte predominant type of the disease resemble mutating and antigen-selected GC B cells, there is evidence that HRS cells in classical HL originate from pre-apoptotic GC B cells. HRS cells of the recently defined novel subtype lymphocyte-rich classical HL moleculary resemble HRS cells of the other types of classical HL, but there appear to be phenotypic differences. In rare cases, HRS cells derive from T cells. In contrast to previous speculations, cell fusion apparently does not play a role in the generation of the tumour clone. By gene expression profiling of HL cell lines, it became evident that HRS cells have lost most of the B cell-typical gene expression program, which may explain why these cells can persist without B cell receptor expression and which suggests that at least one of the transforming events involved in HL pathogenesis affects a master regulator of cell lineage identity.

Molecular biology of Hodgkin's lymphoma

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

Loss of B cell identity correlates with loss of B cell-specific transcription factors in Hodgkin/Reed-Sternberg cells of classical Hodgkin lymphoma

In classical Hodgkin lymphoma the malignant Hodgkin/Reed-Sternberg (HRS) cells characteristically constitute only a small minority of the tumour load. Their origin has been debated for decades, but on the basis of rearrangement and somatic hypermutations of their immunoglubulin (Ig) genes, HRS cells are now ascribed to the B-cell lineage. Nevertheless, phenotypically HRS cells have lost their B cell identity: they usually lack common B cell-specific surface markers such as CD19 and CD79a as well as Ig gene transcripts. Here we demonstrate that Ig promoters as well as both intronic and 3' enhancer sequences are transcriptionally inactive in HRS cell lines. This inactivity correlates with either reduced levels or even a complete lack of several B cell-specific transcription factors required for their expression: Oct-2, OBF-1, PU.1, E47/E12, PAX-5 and EBF. Moreover, we demonstrate that PU.1 and PAX-5 are significantly down-regulated in HRS cells in pathological specimens from primary tumour tissues. However, forced expression of these transcription factors can activate regulatory sequences of silenced B cell marker genes, and in one instance also transcription from a silenced endogenous locus. Thus, HRS cells are dedifferentiated B cells with global down-regulation of B cell-specific genes.

Gene expression profiling defines molecular subtypes of classical Hodgkin's disease

Although the prognosis of Hodgkin's disease is relatively good, around 20% of patients do not benefit from current therapies and succumb to their disease. A large-scale molecular characterization of disease might help improve HD management. Using cDNA arrays, we studied the mRNA expression levels of approximately 1000 selected genes in 34 benign and malignant lymphoid samples including 21 classical Hodgkin's disease (HD) tissue samples. Hierarchical clustering identified three main molecular groups of HD tumours relevant with respect to histology and clinical outcome (response to therapy and survival). Samples from all bad outcome HD (BOHD) patients clustered in one group whereas the two other groups contained most good outcome HD (GOHD) cases. The nodular sclerosis GOHD samples overexpressed genes involved in apoptotic induction and cell signalling, including cytokines, while the BOHD samples were characterized by the upregulation of genes involved in fibroblast activation, angiogenesis, extracellular matrix remodelling, cell proliferation, and the downregulation of tumour suppressor genes. Our results establish a molecular taxonomy of HD correlating with response to therapy and clinical outcome, thereby suggesting the possibility of improving the current prognostic classification.