Autocrine LTA signaling drives NF-κB and JAK-STAT activity and myeloid gene expression in Hodgkin lymphoma.

Persistent NF-κB activation is a hallmark of the malignant Hodgkin/Reed-Sternberg (HRS) cells in classical Hodgkin lymphoma (cHL). Genomic lesions, Epstein-Barr virus infection, soluble factors, and tumor-microenvironment interactions contribute to this activation. Here, in an unbiased approach to identify the cHL cell-secreted key factors for NF-κB activation, we have dissected the secretome of cultured cHL cells by chromatography and subsequent mass spectrometry. We identified lymphotoxin-α (LTA) as the causative factor for autocrine and paracrine activation of canonical and noncanonical NF-κB in cHL cell lines. In addition to inducing NF-κB, LTA promotes JAK2/STAT6 signaling. LTA and its receptor TNFRSF14 are transcriptionally activated by noncanonical NF-κB, creating a continuous feedback loop. Furthermore, LTA shapes the expression of cytokines, receptors, immune checkpoint ligands and adhesion molecules, including CSF2, CD40, PD-L1/PD-L2, and VCAM1. Comparison with single-cell gene-activity profiles of human hematopoietic cells showed that LTA induces genes restricted to the lymphoid lineage, as well as those largely restricted to the myeloid lineage. Thus, LTA sustains autocrine NF-κB activation, impacts activation of several signaling pathways, and drives expression of genes essential for microenvironmental interactions and lineage ambiguity. These data provide a robust rationale for targeting LTA as a treatment strategy for cHL patients.

Mass cytometry of Hodgkin lymphoma reveals a CD4+ regulatory T-cell-rich and exhausted T-effector microenvironment.

In classical Hodgkin lymphoma (cHL), the host antitumor immune response is ineffective. Hodgkin Reed-Sternberg (HRS) cells have multifaceted mechanisms to evade the immune system, including 9p24.1/CD274(PD-L1)/PDCD1LG2(PD-L2) genetic alterations, overexpression of PD-1 ligands, and associated T-cell exhaustion and additional structural bases of aberrant antigen presentation. The clinical success of PD-1 blockade in cHL suggests that the tumor microenvironment (TME) contains reversibly exhausted T effector cells (Teffs). However, durable responses are observed in patients with ß2-microglobulin/major histocompatibility complex (MHC) class I loss on HRS cells, raising the possibility of non-CD8+ T cell-mediated mechanisms of efficacy of PD-1 blockade. These observations highlight the need for a detailed analysis of the cHL TME. Using a customized time-of-flight mass cytometry panel, we simultaneously assessed cell suspensions from diagnostic cHL biopsies and control reactive lymph node/tonsil (RLNT) samples. Precise phenotyping of immune cell subsets revealed salient differences between cHLs and RLNTs. The TME in cHL is CD4+ T-cell rich, with frequent loss of MHC class I expression on HRS cells. In cHLs, we found concomitant expansion of T helper 1 (Th1)-polarized Teffs and regulatory T cells (Tregs). The cHL Th1 Tregs expressed little or no PD-1, whereas the Th1 Teffs were PD-1+ The differential PD-1 expression and likely functional Th1-polarized CD4+ Tregs and exhausted Teffs may represent complementary mechanisms of immunosuppression in cHL.

Formation of the Immunosuppressive Microenvironment of Classic Hodgkin Lymphoma and Therapeutic Approaches to Counter It.

Classic Hodgkin lymphoma (cHL) is characterized by a few tumor cells surrounded by a protective, immunosuppressive tumor microenvironment composed of normal cells that are an active part of the disease. Hodgkin and Reed-Sternberg (HRS) cells evade the immune system through a variety of different mechanisms. They evade antitumor effector T cells and natural killer cells and promote T cell exhaustion. Using cytokines and extracellular vesicles, they recruit normal cells, induce their proliferation and "educate" (i.e. reprogram) them to become immunosuppressive and protumorigenic. Therefore, alternative treatment strategies are being developed to target not only tumor cells but also the tumor microenvironment. Here we summarize current knowledge on the ability of HRS cells to build their microenvironment and to educate normal cells to become immunosuppressive. We also describe therapeutic strategies to counteract formation of the tumor microenvironment and related processes leading to T cell exhaustion and repolarization of immunosuppressive tumor-associated macrophages.

The Role of Reed-Sternberg CD30 Receptor and Lymphocytes in Pathogenesis of Disease and Its Implication for Treatment.

Hodgkin lymphoma is a cancer that can be cured using standard chemotherapy with or without radiation. Although it accounts for only 0.6% of all malignancy worldwide, but it usually affects young adults with median age of 38 years. About 60 to 90% cases can be cured depending on its stage and 5 to 10% cases are refractory to the first-line chemotherapy; while 20 to 30% patients experiencing relapse after receiving the first-line chemotherapy. The relapse causes new problem in treatment. A monoclonal antibody-chemotherapy conjugate, Brentuximab vedotin, was approved by Food Drug Association and European Medicine since 2011 dan was approved by European Medicine Agency since 2012 to treat relapsed classical Hodgkin lymphoma and anaplastic large cell lymphoma (ALCL). Brentuximab vedotin has also been known as anti-CD30.CD30 or Ki-1 or TNFRSF8 is a 120-kD glycoprotein, which is a trans-membrane receptor of Hodgkin lymphoma cells. The glycoprotein was first identified in 1982 using monoclonal antibody against Hodgkin lymphoma-derived cell lines. The glycoprotein was then cloned and recognized as a member of tumor necrosis factor receptor (TNFR) superfamily, which has intracellular, transcellular and extracellular domains. The monoclonal antibody obviously does cause a reaction not only with the Reed-Sternberg (RS) cells of Hodgkin lymphoma, but also with a small number of normal lymphocytes subset, which are located at perifollicular zone as well as lymphoid tumor such as anaplastic large cell lymphoma (ALCL) and other non-lymphoid tumor such as embryonic and pancreas carcinoma, undifferentiated nasopharyngeal carcinoma and malignant melanoma. Therefore, CD30 monoclonal antibody alone to confirm the diagnosis of Hodgkin lymphoma is ineffective as it must be used together with other panel of immunohistochemistry antibodies such as cytokeratins, carcinoma embryonic antigen, melanoma-associated antigen and placental alkaline phosphatide.The expression of CD30 molecules in Reed-Sternberg cells of Hodgkin lymphoma has been demonstrated in over 98% of classical Hodgkin lymphoma cases; however, there is a difference in staining intensity among various cases or even in one case.

Reed-Sternberg cell-derived lymphotoxin-α activates endothelial cells to enhance T-cell recruitment in classical Hodgkin lymphoma.

It is known that cells within the inflammatory background in classical Hodgkin lymphoma (cHL) provide signals essential for the continual survival of the neoplastic Hodgkin and Reed-Sternberg (HRS) cells. However, the mechanisms underlying the recruitment of this inflammatory infiltrate into the involved lymph nodes are less well understood. In this study, we show in vitro that HRS cells secrete lymphotoxin-α (LTα) which acts on endothelial cells to upregulate the expression of adhesion molecules that are important for T cell recruitment. LTα also enhances the expression of hyaluronan which preferentially contributes to the recruitment of CD4(+) CD45RA(+) naïve T cells under in vitro defined flow conditions. Enhanced expression of LTα in HRS cells and tissue stroma; and hyaluronan on endothelial cells are readily detected in involved lymph nodes from cHL patients. Our study also shows that although NF-κB and AP-1 are involved, the cyclooxygenase (COX) pathway is the dominant regulator of LTα production in HRS cells. Using pharmacological inhibitors, our data suggest that activity of COX1, but not of COX2, directly regulates the expression of nuclear c-Fos in HRS cells. Our findings suggest that HRS cell-derived LTα is an important mediator that contributes to T cell recruitment into lesional lymph nodes in cHL.

Pembrolizumab in classical Hodgkin's lymphoma.

Pembrolizumab is a humanized monoclonal antibody directed against programmed cell death protein 1 (PD-1), a key immune-inhibitory molecule expressed on T cells and implicated in CD4+ T-cell exhaustion and tumor immune-escape mechanisms. Classical Hodgkin's lymphoma (cHL) is a unique B-cell malignancy in the sense that malignant Reed-Sternberg (RS) cells represent a small percentage of cells within an extensive immune cell infiltrate. PD-1 ligands are upregulated on RS cells as a consequence of both chromosome 9p24.1 amplification and Epstein-Barr virus infection and by interacting with PD-1 promote an immune-suppressive effect. By augmenting antitumor immune response, pembrolizumab and nivolumab, another monoclonal antibody against PD-1, have shown significant activity in patients with relapsed/refractory cHL as well as an acceptable toxicity profile with immune-related adverse events that are generally manageable. In this review, we explore the rationale for targeting PD-1 in cHL, review the clinical trial results supporting the use of checkpoint inhibitors in this disease, and present future directions for investigation in which this approach may be used.

Checkpoint inhibitors in Hodgkin's lymphoma.

Hodgkin's lymphoma is unusual among cancers in that it consists of a small number of malignant Hodgkin/Reed-Sternberg cells in a sea of immune system cells, including T cells. Most of these T cells are reversibly inactivated in different ways and their reactivation may induce a very strong immune response to cancer cells. One way of reactivation of T cells is with antibodies blocking the CTLA-4 and especially with antibodies directed against PD-1 or the PD-L1 ligand thereby reversing the tumor-induced downregulation of T-cell function and augmenting antitumor immune activity at the priming (CTLA-4) or tissue effector (PD-1) phase. Immune checkpoint inhibitors have been evidenced as an additional treatment option with substantial effectiveness and acceptable toxicity in heavily pretreated patients with Hodgkin's lymphoma. Particularly, PD-1 blockade with nivolumab and pembrolizumab has demonstrated significant single-agent activity in this select population.

[Clinical features and prognosis of CD20-positive classical Hodgkin lymphoma].

OBJECTIVE: To explore the clinical characteristics and prognosis of CD20-positive classical Hodgkin lymphoma (CHL). METHODS: Data from CHL patients with CD20 immunohistochemical staining result who were treated in Cancer Hospital of Chinese Academy of Medical Sciences between September 2007 and March 2014 were reviewed. The relationship of CD20 expression in Reed-Sternberg(R-S)cells with CHL subtypes, clinical characteristics, and prognosis were analyzed. Fisher test was used to analyze the differences between groups and Kaplan-Meier for survival analysis. RESULTS: A total of 263 patients were included in this study. Among the 263 patients, 74 (28.1%) were CD20-postitive. CD20-positive cases showed significantly higher proportions of Epstein-Barr virus (EBV) infection-related, mixed cellularity, and lymphocyte-rich CHL subtypes compared with CD20-negeative patients [52.8% (28/53) vs 19.0% (22/116), 37.9% (25/66) vs 31.6% (54/171), 22.7% (15/66) vs 3.5% (6/171), all P<0.05]. Univariate analysis identified EBV infection, age (≥ 40 years, especially ≥ 60 years), and Ⅲ-Ⅳ stage were correlated with reduced 3-year progression-free survival (PFS) and overall survival (OS) (PFS: 70.3 vs 87.7%, 79.2% vs 89.8%, 56.8% vs 91.5%, 70.4% vs 93.2%; OS: 81.0% vs 100%, 92.1% vs 99.4%, 75.4% vs 99.2%, 90.3% vs 100%; all P<0.05); and CD20-positive and not receiving local radiotherapy were associated with reduced PFS (79.7% vs 90.6%, 68.8% vs 90.6%, both P<0.05), not with OS (92.4% vs 98.3%, 94.0% vs 99.4%, both P>0.05). Patients positive in both CD20 expression and EBV-encoded small RNAs (EBER) showed low PFS. CONCLUSIONS: CD20 expression in R-S cells in CHL may be closed related with EBV infection. EBV infection is associated with unfavorable prognosis. The effect of CD20-postitive on prognosis may be mediated by the prognostic effect of EBV infection.

Protrusion-guided extracellular vesicles mediate CD30 trans-signalling in the microenvironment of Hodgkin's lymphoma.

Classical Hodgkin's lymphoma (cHL)-affected lymphoid tissue contains only a few malignant Hodgkin and Reed-Sternberg (HRS) cells, which are disseminated within a massive infiltrate of reactive cells. In particular, the innate immune infiltrate is deemed to support tumour growth by direct cell-cell interaction. Since they are rarely found in close proximity to the malignant cells in situ, we investigated whether cHL-derived extracellular vesicles might substitute for a direct cell-cell contact. We studied the crosstalk of the transmembrane proteins CD30 and CD30 ligand (CD30L) because they are selectively expressed on HRS and innate immune cells, respectively. Here, we showed that HRS cells released both the ectodomain as a soluble molecule (sCD30) and the entire receptor on the surface of extracellular vesicles. The vesicle diameter was 40-800 nm, as determined by cryo- and immune electron microscopy. In addition to CD30, typical extracellular vesicle markers were detected by mass spectrometry and flow cytometry, including tetraspanins, flotillins, heat shock proteins and adhesion molecules. In contrast to sCD30, vesicles caused a CD30-dependent release of interleukin-8 in CD30L(+) eosinophil-like EoL-1 cells and primary granulocytes from healthy donors, underscoring the functionality of CD30 on vesicles. In extracellular matrix (ECM)-embedded culture of HRS cells, a network of actin and tubulin-based protrusions guided CD30(+) vesicles into the micro-environment. This network targeted CD30(+) vesicles towards distant immune cells and caused a robust polarization of CD30L. Confocal laser scanning microscopy of 30 µm sections showed a CD30 vesicle-containing network also in cHL-affected lymphoid tissue of both mixed-cellularity and nodular sclerosing subtypes. This network might facilitate the communication between distant cell types in cHL tissue and allow a functional CD30-CD30L interaction in trans. The tubulin backbone of the network may provide a target for the therapy of cHL with antitubulin-based CD30 antibody constructs.

High ERp5/ADAM10 expression in lymph node microenvironment and impaired NKG2D ligands recognition in Hodgkin lymphomas.

Herein we describe that in classic Hodgkin lymphomas (cHL, n = 25) the lymph node (LN) stroma displayed in situ high levels of transcription and expression of the disulfide-isomerase ERp5 and of the disintegrin-metalloproteinase ADAM10, able to shed the ligands for NKG2D (NKG2D-L) from the cell membrane. These enzymes were detected both in LN mesenchymal stromal cells (MSCs) and in Reed-Sternberg (RS) cells; in addition, MIC-A and ULBP3 were present in culture supernatants of LN MSCs or RS cells. NKG2D-L-negative RS cells could not be killed by CD8(+)αßT or γδT cells; tumor cell killing was partially restored by treating RS cells with valproic acid, which enhanced NKG2D-L surface expression. Upon coculture with LN MSCs, CD8(+)αßT and γδT cells strongly reduced their cytolytic activity against NKG2D-L(+) targets; this seems to be the result of TGF-ß, present at the tumor site, produced in vitro by LN MSCs and able to down-regulate the expression of NKG2D on T lymphocytes. In addition, CD8(+)αßT and γδT cells from the lymph nodes of cHL patients, cocultured in vitro with LN MSCs, underwent TGF-ß-mediated down regulation of NKG2D. Thus, in cHL the tumor microenvironment is prone to inhibit the development of an efficient antitumor response.

Epstein-Barr virus (EBV) positive classical Hodgkin lymphoma of Iraqi children: an immunophenotypic and molecular characterization of Hodgkin/Reed-Sternberg cells.

BACKGROUND: Classical Hodgkin lymphoma (cHL) in children is often associated with EBV infection, more commonly in developing countries. PROCEDURE: Here we describe the histological, immunohistochemical, and molecular features of 57 cases of HL affecting Iraqi children under 14 years of age. RESULTS: Histologically, 51 cases were classified as cHL of Mixed Cellularity and Nodular Sclerosis subtypes (MC = 69%; NS = 31%), and 6 cases as Nodular Lymphocyte Predominant HL (NLP-HL). EBV infection of H/RS cells was demonstrated in 44 of 51 cases of cHL (86%), and was more common in MC than in NS (97% vs. 63%; P = 0.0025). The immunophenotypic profile of H/RS cells was similar in MC and NS, and was not influenced by EBV infection; H/RS cells were consistently positive for PAX-5 and to a lesser degree for other B cell markers including CD20/CD79a, OCT-2, and BOB-1. Clonal IGH rearrangements were detected in 14 of 38 cHL (37%), with no significant difference between MC and NS cases, and with no association with the EBV status. Oligoclonal/monoclonal TCRγ rearrangements were present in 28 of 38 cases (74%), suggestive of restricted T cell responses. CONCLUSIONS: Our findings indicate that cHL occurring in Iraqi children is characterized by immunohistochemical and molecular features undistinguishable from those present in cHL occurring elsewhere in the world. Moreover, the high incidence of EBV-infected H/RS cells and frequent occurrence of restricted T cell responses might be indicative of a defective local immune response perhaps related to the very young age of the children.

Mechanisms of aberrant GATA3 expression in classical Hodgkin lymphoma and its consequences for the cytokine profile of Hodgkin and Reed/Sternberg cells.

The transcription factor network in Hodgkin lymphoma (HL) represents a unique composition of proteins found in no other hematopoietic cell. Among these factors, an aberrant expression of the T-cell transcription factor GATA3 is observed in B cell-derived Hodgkin and Reed/Sternberg (HRS) tumor cells. Herein, we elucidate the regulation and function of this factor in HL. We demonstrate binding of NFκB and Notch-1, 2 factors with deregulated activity in HL to GATA3 promoter elements. Interference with NFκB and Notch-1 activity led to decreased GATA3 expression, indicating a dependency of deregulated GATA3 expression on these transcription factors. Down-regulation of GATA3 in HL cell lines demonstrated its role in the regulation of IL-5, IL-13, STAT4, and other genes. A correlation between GATA3 and IL-13 expression was confirmed for HRS cells in HL tissues. Thus, GATA3 shapes the cytokine expression and signaling that is typical of HL. Conclusively, aberrant GATA3 expression in HRS cells is stimulated by the deregulated constitutive activity of NFκB and Notch-1, indicating a complex network of deregulated transcription factors in these cells. GATA3 activity significantly contributes to the typical cytokine secretion of and signaling in HRS cells, which presumably plays an essential role in HL pathogenesis.

Role of immune escape mechanisms in Hodgkin's lymphoma development and progression: a whole new world with therapeutic implications.

Hodgkin's lymphoma represents one of the most frequent lymphoproliferative syndromes, especially in young population. Although HL is considered one of the most curable tumors, a sizeable fraction of patients recur after successful upfront treatment or, less commonly, are primarily resistant. This work tries to summarize the data on clinical, histological, pathological, and biological factors in HL, with special emphasis on the improvement of prognosis and their impact on therapeutical strategies. The recent advances in our understanding of HL biology and immunology show that infiltrated immune cells and cytokines in the tumoral microenvironment may play different functions that seem tightly related with clinical outcomes. Strategies aimed at interfering with the crosstalk between tumoral Reed-Sternberg cells and their cellular partners have been taken into account in the development of new immunotherapies that target different cell components of HL microenvironment. This new knowledge will probably translate into a change in the antineoplastic treatments in HL in the next future and hopefully will increase the curability rates of this disease.

FOXP3(+) regulatory and TIA-1(+) cytotoxic T lymphocytes in HIV-associated Hodgkin lymphoma.

Human immunodeficiency virus (HIV) infects CD4(+) lymphocytes, leading to a development of malignant lymphomas, such as HIV-associated Hodgkin Lymphoma (HIV-HL). This study aimed to assess the differences in cellular composition of the inflammatory reactive background of HIV-HLs. We examined infiltrating T lymphocytes, specifically regulatory T cells, cytotoxic cells, Epstein-Barr virus (EBV) related antigens and HIV-receptor CCR5. In all HIV-HL cases, Hodgkin and Reed-Sternberg (HRS) cells showed EBER1 expression, LMP-1 staining positivity and EBNA-2 staining negativity, except for one case which showed LMP-1 staining negativity. Our histological findings indicate the percentage of CD8(+) , TIA-1(+) lymphocytes was significantly higher in HIV-HL than in non-HIV-HL cases (P < 0.05). On the other hand, the percentage of CD4(+) , FOXP3(+) lymphocytes was significantly lower in HIV-HL than in non-HIV-HL cases (P < 0.05) but present. The percentage of CCR5(+) lymphocytes was significantly lower in HIV-HL than in non-HIV-HL cases (P < 0.05). Usually, CD4(+) and CCR5(+) lymphocytes are reported to be rarely detected in HIV-associated non-Hodgkin lymphomas, but the presence of CD4(+) and/or FOXP3(+) lymphocytes may be implicated in the pathogenesis of HL. In addition, although additional CD8(+) lymphocytes are probably not EBV-LMP specific cytotoxic T-cells, these lymphocytes may also well be involved in the pathogenesis of HIV-HL.

Targeting macrophages in classical Hodgkin's lymphoma may seem rational, but is it safe?

A few reports have linked increased numbers of tissue macrophages with treatment failure and reduced lifespan in classical Hodgkin's lymphoma (HL) patients. Some investigators even suggested to target the macrophages in HL with biologic therapy, thus eliminating them from the tumor microenvironment. This review explores the risk: benefit equation of such approach as well as what the author believes is the driving force behind the 'great' migration of macrophages in HL. This article unravels the inflammatory pathways and immune alterations in classical HL that lead to a complex network consisting of T-cells, numerous cytokines, macrophages, and other cells. Macrophages are thought to play a crucial role in tumor antigen processing and presentation tasks, Reed-Sternberg (RS) cell phagocytosis, and antibody-dependent cellular cytotoxicity, therefore their extinction may be hazardous. The author believes RS cells should be targeted by the biologics, not the macrophages, and links his hopes with the existing investigational anti-CD30 therapies in relapsed/refractory classical HL.

Epstein-Barr virus latent membrane protein 2A exploits Notch1 to alter B-cell identity in vivo.

Expression of latent membrane protein 2 (LMP2A) during B-cell development leads to global alterations in gene transcription similar to those seen in Hodgkin Reed-Sternberg cells of Hodgkin lymphoma (HL). Along with the consistent detection of LMP2A in Epstein-Barr virus-associated HL, this implicates a role for LMP2A in the pathogenesis of HL. We have shown that LMP2A constitutively activates the Notch1 pathway to autoregulate the LMP2A promoter. To determine whether constitutive activation of the Notch pathway is important for LMP2A-mediated alterations in B-cell development in vivo, TgE-LMP2A-transgenic mice were intercrossed with mice expressing loxP-flanked Notch1 genes and Cre recombinase. B cells from TgE Notch1(lox/lox)-CD19(+/Cre) mice have an increase in immunoglobulin M and CD43 and a decrease in CD5 expression in the bone marrow compared with TgE Notch1(lox/lox) mice, indicating the LMP2A signal for developmental aberrations is impaired in the absence of Notch1. Real-time reverse-transcribed polymerase chain reaction analysis reveals that LMP2A requires the Notch1 pathway to alter levels of B cell-specific transcription factors, E2A and EBF. Interestingly, Notch1 appears to be important for LMP2A-mediated survival in low interleukin-7. We propose that LMP2A and the Notch1 pathway may cooperate to induce the alterations in B-cell identity seen in Hodgkin Reed-Sternberg cells.

The molecular pathogenesis of Hodgkin lymphoma.

Hodgkin lymphoma (HL) is an unusual malignancy in that the tumour cells, the Hodgkin and Reed-Sternberg (HRS) cells, are a minor component of the tumour mass, the bulk of which is a mixed cellular infiltrate. There is compelling evidence that HRS cells are clonal B cells that have lost their B cell phenotype. Mature B cells lacking B cell receptors would normally die by apoptosis, and therefore HRS cells must have developed mechanisms to facilitate survival. The escape from apoptosis and transcriptional reprogramming of HRS cells are interlinked and appear central to disease pathogenesis. Epstein-Barr virus (EBV) is present in the HRS cells of a proportion of cases and expresses genes with a plausible oncogenic function. It is likely that EBV plays a role in reprogramming and survival through dysregulation of several signalling networks and transcription factors, including nuclear factor (NF)-κB. Activation of NF-κB is a feature of all HRS cells and gene mutations affecting this pathway appear common in EBV-negative HL. The HRS cell furthers its own survival by attracting a supportive microenvironment of immune and stromal cells, and suppressing local immune responsiveness. Although many questions remain unanswered, the last two decades have witnessed a considerable increase in our knowledge of this complex disease.

The classical Hodgkin's lymphoma microenvironment and its role in promoting tumour growth and immune escape.

It has become clear that cancer is not merely a growth of autonomously proliferating cells, but that other non-malignant cell types are a functional part of the disease. Immune cells, fibroblasts, specialized mesenchymal cells and microvasculature together make up the tumour microenvironment and have functional interactions with tumour cells. Classical Hodgkin's lymphoma (cHL) is characterized by only a few malignant cells and an abundance of inflammatory cells. Hodgkin and Reed-Sternberg (HRS) cells are surrounded by T and B cells admixed with plasma cells, macrophages, eosinophils and mast cells. A constitutive activity of NF-kappaB and an altered JAK-STAT signalling pathway are part of the biological background associated with the increased expression of cytokines and cytokine receptors seen in HRS cells. Over-expression of the members of the TNF receptor family, especially CD30 and CD40, is a hallmark of HRS cells. cHL is a tumour where aberrant cytokine production contributes not only to the proliferation of HRS cells but also to the maintenance of an appropriate environment for the tumour cells. In addition, several chemokines contribute to the composition of the inflammatory background in cHL. This review summarizes updated information on the complex interactions between the HRS cells and their tissue microenvironment and highlights the development of newer therapeutic strategies aimed at targeting the non-malignant inflammatory/immune cellular components of HL that are involved in cancer cell growth and/or immune escape.

The circuitry of the tumor microenvironment in adult and pediatric Hodgkin lymphoma: cellular composition, cytokine profile, EBV, and exosomes.

BACKGROUND: Classical Hodgkin lymphoma (cHL) is a unique lymphoid malignancy with a tumor microenvironment (TME) consisting of a small number of neoplastic-Hodgkin and Reed-Sternberg (H-RS) cells (<1%), surrounded by a large number of nonneoplastic infiltrating immune cells (>90%). The TME of cHL critically depends on immune cells to support tumor growth as H-RS cells cannot survive and proliferate in isolation. RECENT FINDINGS: Programmed cell death protein 1 (PD-1) ligand expressed on H-RS cells inhibits the clearance of tumor by causing T-cell exhaustion. Nivolumab and pembrolizumab, PD-1 inhibitors, have been proven to be effective in treating adult and pediatric patients with R/R cHL. Tumor-associated macrophages (TAMs) are a central component of TME and are known to cause poor prognosis in adult HL. However, the prognostic impact of CD68+ TAMs in pediatric HL remains ambiguous. EBV modulates the tumor milieu of HL and plays a strategic role in immune escape by enrichment of the TME with Treg cells and associated immunosuppressive cytokines in adult HL. In contrast, EBV+ pediatric patients have increased infiltration of CD8+ T-cells and show a better therapeutic response suggesting viral-related TME is distinct in childhood HL. The role of CASP3 in apoptosis of H-RS cells and its correlation with response prediction in adult and pediatric HL suggest it may serve as a potential biomarker. In cHL, CD30, EBV, and NF-κB signaling employ exosomes for cell-cell communication that triggers the migration capacity of fibroblasts, stimulate to produce proinflammatory cytokines, and help to create a tumor-supportive microenvironment. CONCLUSION: The cHL microenvironment is distinct in adult and pediatric HL. Future studies are required to understand the role of interplay between H-RS cells and EBV-associated microenvironment and their clinical outcome. They may present novel therapeutic targets for the development of antilymphoma therapy.

Rare occurrence of classical Hodgkin's disease as a T cell lymphoma.

Recent work identified Hodgkin and Reed-Sternberg (H/RS) cells in classical Hodgkin's disease (cHD) as clonal progeny of mature B cells. Therefore, it is generally assumed that cHD homogenously represents a B cell lymphoma. In a subset of cHD, however, H/RS cells expressing T cell-associated proteins may be candidates for alternative lineage derivation. Single H/RS cells with cytotoxic T cell phenotype were micromanipulated from three cases of cHD and analyzed by single cell polymerase chain reaction for immunoglobulin heavy (IgH) and light chain (IgL) gene rearrangements, T cell receptor (TCR)-beta gene rearrangements, and germline configuration of the IgH and TCR-beta loci. H/RS cells from two cases of cHD harbored clonal, somatically mutated Ig gene rearrangements, whereas TCR-beta loci were in germline configuration. In contrast, H/RS cells from an additional case harbored clonal TCR-beta variable/diversity/joining (VDJ) and DJ gene rearrangements, whereas the IgH locus was in germline configuration on both alleles. Thus, in two cases of cHD with H/RS cells expressing cytotoxic T cell molecules, the tumor cells are derived from mature B cells that aberrantly express T cell markers. In a third case, however, H/RS cells were derived from a T cell, demonstrating that cHD can also occur as a T cell lymphoma.