Numerous Ontogenetic Roads to Mantle Cell Lymphoma

Immunohistochemical analysis of arachidonate 5-lipoxygenase expression in B-cell lymphomas: Implication for B cell differentiation and its analogy with lymphomagenesis

Arachidonate 5-lipoxygenase (ALOX5) is a cardinal enzyme in the synthesis of leukotrienes, which are powerful immune-regulating lipid mediators. We previously reported that ALOX5 is preferentially expressed in B lymphocytes in the mantle zone of human lymphoid tissue. In the context of physiological relevance, the loss of the Alox5 gene in mice significantly impairs the development of follicular B helper T cells and antibody production. However, ALOX5 expression in B-cell lymphomas has not been investigated in detail. In this study, we examined ALOX5 expression in representative B-cell lymphomas and non-neoplastic lymphoid tissues by immunohistochemistry with a commercially available anti-ALOX5 antibody that can be used on formalin-fixed paraffin-embedded specimens. Interestingly, 22/22 cases of mantle cell lymphoma, 7/7 cases of chronic lymphocytic leukemia/small cell lymphoma, and 20/20 cases of follicular lymphoma expressed ALOX5. A small proportion of extranodal marginal zone lymphoma/mucosa-associated lymphoid tissue lymphoma or nodal marginal zone lymphoma cases were positive for ALOX5 (2/13 or 1/3, respectively). In contrast, no cases with diffuse large B-cell lymphoma, regardless of germinal center B cell (GCB) or non-GCB type, expressed ALOX5 (0/25 cases). These findings suggest that ALOX5 may be a novel marker for identifying the cell of origin of B-cell lymphoma. Further investigation is required to clarify the biological significance of ALOX5 expression in lymphoma cells.

The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Lymphoid Neoplasms

We herein present an overview of the upcoming 5^th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4^th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5^th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.

Laying the groundwork for the Biobank of Rare Malignant Neoplasms at the service of the Hellenic Network of Precision Medicine on Cancer

Biobanks constitute an integral part of precision medicine. They provide a repository of biospecimens that may be used to elucidate the pathophysiology, support diagnoses, and guide the treatment of diseases. The pilot biobank of rare malignant neoplasms has been established in the context of the Hellenic Network of Precision Medicine on Cancer and aims to enhance future clinical and/or research studies in Greece by collecting, processing, and storing rare malignant neoplasm samples with associated data. The biobank currently comprises 553 samples; 384 samples of hematopoietic and lymphoid tissue malignancies, 72 samples of pediatric brain tumors and 97 samples of malignant skin neoplasms. In this article, sample collections and their individual significance in clinical research are described in detail along with computational methods developed specifically for this project. A concise review of the Greek biobanking landscape is also delineated, in addition to recommended technologies, methodologies and protocols that were integrated during the creation of the biobank. This project is expected to re‑enforce current clinical and research studies, introduce advances in clinical and genetic research and potentially aid in future targeted drug discovery. It is our belief that the future of medical research is entwined with accessible, effective, and ethical biobanking and that our project will facilitate research planning in the '‑omic' era by contributing high‑quality samples along with their associated data.

Detailed characterization of the transcriptome of single B cells in mantle cell lymphoma suggesting a potential use for SOX4

Mantle cell lymphoma (MCL) is a malignancy arising from naive B lymphocytes with common bone marrow (BM) involvement. Although t(11;14) is a primary event in MCL development, the highly diverse molecular etiology and causal genomic events are still being explored. We investigated the transcriptome of CD19⁺ BM cells from eight MCL patients at single-cell level. The transcriptomes revealed marked heterogeneity across patients, while general homogeneity and clonal continuity was observed within the patients with no clear evidence of subclonal involvement. All patients were SOX11⁺CCND1⁺CD20⁺. Despite monotypic surface immunoglobulin (Ig) κ or λ protein expression in MCL, 10.9% of the SOX11 + malignant cells expressed both light chain transcripts. The early lymphocyte transcription factor SOX4 was expressed in a fraction of SOX11 + cells in two patients and co-expressed with the precursor lymphoblastic marker, FAT1, in a blastoid case, suggesting a potential prognostic role. Additionally, SOX4 was found to identify non-malignant SOX11^– pro-/pre-B cell populations. Altogether, the observed expression of markers such as SOX4, CD27, IgA and IgG in the SOX11⁺ MCL cells, may suggest that the malignant cells are not fixed in the differentiation state of naïve mature B cells, but instead the patients carry B lymphocytes of different differentiation stages.

Repertoire of Rearranged Immunoglobulin Heavy Chain Genes in Russian Patients With B-Cell Lymphoproliferative Diseases

INTRODUCTION

Immunoglobulin heavy chain variable region (IGHV) repertoire narrowing could be an evidence for the involvement of a limited set of antigens in the development of lymphomas. For chronic lymphocytic leukemia (CLL) the existence of more than 200 subgroups of tumor IGHV antigen-binding sites, so called "stereotypical" antigen receptors (SAR) has been shown. For others lymphomas the possibility of SARs is also suggested. The aim of this study is to compare the tumor IGHVs and possible SARs in various B-cell malignancies in Russia and other countries.

MATERIALS AND METHODS

The study included samples of 1800 CLL patients, 52 patients with mantle cell lymphoma, 48 patients with hairy cell lymphoma and 37 patients with splenic marginal cell lymphoma. The nucleotide sequences of the IGHV genes were determined according to ERIC protocol.

RESULTS

In CLL most common IGHV genes were IGHV1-69, IGHV1-2, IGHV3-30 and IGHV4-34. The most common SARs were CLL#1, CLL#6, CLL#2, CLL#3. In MCL the most common genes were IGHV4-34, IGHV3-21, IGHV3-23. In 5 MCL patients CDR3 sequences were identified matching definitions of a stereotyped. In the half of SMZL patients was identified gene IGHV1-2. Other IGHV genes were much less common. Two pairs of SMZL patients have motives similar to each other. In HCL IGHV repertoire was the most variable, no trends for antigen receptor stereotypy were observed. It was found that SARs are highly disease-specific both at the level of nucleotide and amino acid sequences.

CONCLUSION

Our results suggest that antigens crucial for the pathogenesis of B-cell malignancies could be disease-specific. Further studies on extended samples of non-CLL patients concerning the role of SARs in pathogenesis of these diseases may also contribute to the development of new diagnostic and prognostic markers.

SOX11, CD70 and Treg cells configure the tumor immune microenvironment of aggressive mantle cell lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm with a heterogeneous clinical and biological behavior. SOX11 oncogenic expression contributes to the aggressiveness of these tumors by different mechanisms including tumor and stromal cell interactions. However, the precise composition of the immune cell microenvironment of MCL, its possible relationship to SOX11 expression, and how it may contribute to tumor behavior is not well known. Here, we performed an integrative transcriptome analysis of 730 immune-related genes combined with the immune cell phenotype analysis by immunohistochemistry in SOX11+ and SOX11- primary nodal MCL cases and non-neoplastic reactive lymph nodes (RLN). SOX11+ MCL had a significant lower T-cell intratumoral infiltration compared to negative cases. A reduced expression of MHCI/II-like and T-cell costimulation and signaling activation related transcripts was significantly associated with poor clinical outcome. Moreover, we identified CD70 as a SOX11 direct target gene, whose overexpression was induced in SOX11+ but not SOX11- tumor cells by CD40L in vitro. CD70 was overexpressed in primary SOX11+ MCL and it was associated with an immune unbalance of the tumor microenvironment characterized by increased number of effector Treg cell infiltration, higher proliferation, and aggressive clinical course. CD27 was expressed with moderate to strong intensity in 76% of cases. Overall, our results suggest that SOX11 expression in MCL is associated with an immunosuppressive microenvironment characterized by CD70 overexpression in tumor cells, increased Treg cell infiltration and downmodulation of antigen-processing and -presentation and T-cell activation that could promote MCL progression and represent a potential target for tailored therapies.

Mantle cell lymphoma

MCL is a well-characterized generally aggressive lymphoma with a poor prognosis. However, patients with a more indolent disease have been reported in whom the initiation of therapy can be delayed without any consequence for the survival. In 2017 the World Health Organization updated the classification of MCL describing two main subtypes with specific molecular characteristics and clinical features, classical and indolent leukaemic nonnodal MCL. Recent research results suggested an improving outcome of this neoplasm. The addition of rituximab to conventional chemotherapy has increased overall response rates, but it did not improve overall survival compared to chemotherapy alone. The use of intensive frontline therapies including rituximab and consolidation with autologous stem cell transplantation ameliorated response rate and prolonged progression-free survival in young fit patients, but any impact on survival remains to be proven. Furthermore, the optimal timing, cytoreductive regimen and conditioning regimen, and the clinical implications of achieving a disease remission even at molecular level remain to be elucidated. The development of targeted therapies as the consequence of better understanding of pathogenetic pathways in MCL might improve the outcome of conventional chemotherapy and spare the toxicity of intense therapy in most patients. Cases not eligible for intensive regimens, may be considered for less demanding therapies, such as the combination of rituximab either with CHOP or with purine analogues, or bendamustine. Allogeneic SCT can be an effective option for relapsed disease in patients who are fit enough and have a compatible donor. Maintenance rituximab may be considered after response to immunochemotherapy as the first-line strategy in a wide range of patients. Finally, since the optimal approach to the management of MCL is still evolving, it is critical that these patients are enrolled in clinical trials to identify the better treatment options.

B Cell Receptor Immunogenetics in B Cell Lymphomas: Immunoglobulin Genes as Key to Ontogeny and Clinical Decision Making

The clonotypic B cell receptor immunoglobulin (BcR IG) plays a seminal role in B cell lymphoma development and evolution. From a clinical perspective, this view is supported by the remarkable therapeutic efficacy of BcR signaling inhibitors, even among heavily pre-treated, relapsed/refractory patients. This clinical development complements immunogenetic evidence for antigen drive in the natural history of these tumors. Indeed, BcR IG gene repertoire biases have been documented in different B cell lymphoma subtypes, alluding to selection of B cell progenitors that express particular BcR IG. Moreover, distinct entities display imprints of somatic hypermutation within the clonotypic BcR IG gene following patterns that strengthen the argument for antigen selection. Of note, at least in certain B cell lymphomas, the BcR IG genes are intraclonally diversified, likely in a context of ongoing interactions with antigen(s). Moreover, BcR IG gene repertoire profiling suggests that unique immune pathways lead to distinct B cell lymphomas through targeting cells at different stages in the B cell differentiation trajectory (e.g., germinal center B cells in follicular lymphoma, FL). Regarding the implicated antigens, although their precise nature remains to be fully elucidated, immunogenetic analysis has offered important hints by revealing similarities between the BcR IG of particular lymphomas and B cell clones with known antigenic specificity: this has paved the way to functional studies that identified relevant antigenic determinants of classes of structurally similar epitopes. Finally, in certain tumors, most notably chronic lymphocytic leukemia (CLL), immunogenetic analysis has also proven instrumental in accurate patient risk stratification since cases with differing BcR IG gene sequence features follow distinct disease courses and respond differently to particular treatment modalities. Overall, delving into the BcR IG gene sequences emerges as key to understanding B cell lymphoma pathophysiology, refining prognostication and assisting in making educated treatment choices.

Stereotyped B Cell Receptor Immunoglobulins in B Cell Lymphomas

Comprehensive analysis of the clonotypic B cell receptor immunoglobulin (BcR IG) gene rearrangement sequences in patients with mature B cell neoplasms has led to the identification of significant repertoire restrictions, culminating in the discovery of subsets of patients expressing highly similar, stereotyped BcR IG. This finding strongly supports selection by common epitopes or classes of structurally similar epitopes in the ontogeny of these tumors. BcR IG stereotypy was initially described in chronic lymphocytic leukemia (CLL), where the stereotyped fraction of the disease accounts for a remarkable one-third of patients. However, subsequent studies showed that stereotyped BcR IG are also present in other neoplasms of mature B cells, including mantle cell lymphoma (MCL) and splenic marginal zone lymphoma (SMZL). Subsequent cross-entity comparisons led to the conclusion that stereotyped IG are mostly "disease-specific," implicating distinct immunopathogenetic processes. Interestingly, mounting evidence suggests that a molecular subclassification of lymphomas based on BcR IG stereotypy is biologically and clinically relevant. Indeed, particularly in CLL, patients assigned to the same subset due to expressing a particular stereotyped BcR IG display remarkably consistent biological background and clinical course, at least for major and well-studied subsets. Thus, the robust assignment to stereotyped subsets may assist in the identification of mechanisms underlying disease onset and progression, while also refining risk stratification. In this book chapter, we provide an overview of the recent BcR IG stereotypy studies in mature B cell malignancies and outline previous and current methodological approaches used for the identification of stereotyped IG.

Chronic lymphocytic leukemia and mantle cell lymphoma: crossroads of genetic and microenvironment interactions

Chronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) are 2 well-defined entities that diverge in their basic pathogenic mechanisms and clinical evolution but they share epidemiological characteristics, cells of origin, molecular alterations, and clinical features that differ from other lymphoid neoplasms. CLL and MCL are classically considered indolent and aggressive neoplasms, respectively. However, the clinical evolution of both tumors is very heterogeneous, with subsets of patients having stable disease for a long time whereas others require immediate intervention. Both CLL and MCL include 2 major molecular subtypes that seem to derive from antigen-experienced CD5⁺ B cells that retain a naive or memory-like epigenetic signature and carry a variable load of immunoglobulin heavy-chain variable region somatic mutations from truly unmutated to highly mutated, respectively. These 2 subtypes of tumors differ in their molecular pathways, genomic alterations, and clinical behavior, being more aggressive in naive-like than memory-like-derived tumors in both CLL and MCL. The pathogenesis of the 2 entities integrates the relevant influence of B-cell receptor signaling, tumor cell microenvironment interactions, genomic alterations, and epigenome modifications that configure the evolution of the tumors and offer new possibilities for therapeutic intervention. This review will focus on the similarities and differences of these 2 tumors based on recent studies that are enhancing the understanding of their pathogenesis and creating solid bases for new management strategies.

The role of B cell antigen receptors in mantle cell lymphoma

Mantle cell lymphoma (MCL) is characterized by an aggressive clinical course and secondary resistance to currently available therapies in most cases. Therefore, despite recent advances in the treatment of this disease, it is still considered to be incurable in the majority of cases. MCL B cells retain their B cell antigen receptor (BCR) expression during and after neoplastic transformation. BCRs in MCL show distinct patterns of antigen selection and ongoing BCR signaling. However, little is known about the involved antigens and the mechanisms leading to lymphomagenesis and lymphoma progression in MCL. Recent preclinical and clinical studies have established a crucial role of the BCR and the potential of inhibiting its signaling in this disease. This has established the B cell antigen receptor signaling cascade as a very promising therapeutic target to improve outcome in MCL alone or in combination with chemo-immunotherapy in recent years.