Primary central nervous system lymphomas are derived from germinal-center B cells and show a preferential usage of the V4-34 gene segment

Expression Cloning of Antibodies from Single Human B Cells

The majority of lymphomas originate from B cells at the germinal center stage. Preferential selection of B-cell clones by a limited set of antigens has been suggested to drive lymphoma development. While recent studies in B-cell chronic lymphocytic leukemia (CLL) have shown that self-reactive B-cell receptors (BCR) can generate cell-autonomous signaling and proliferation, our knowledge about the role of BCRs for the development or survival of other lymphomas remains limited. Here, we describe a strategy to characterize the antibody reactivity of human B cells. The approach allows for unbiased characterization of the human antibody repertoire on single-cell level through the generation of recombinant monoclonal antibodies from primary human B cells of defined origin. This protocol offers a detailed description of the method starting from the flow cytometric isolation of single human B cells to the RT-PCR-based amplification of the expressed immunoglobulin (Ig) transcripts (IGH, IGK, and IGL) and their subsequent cloning into expression vectors for the in vitro production of recombinant monoclonal antibodies. The strategy may be used to obtain information about the clonal evolution of B-cell lymphomas by single-cell sequencing of Ig transcripts and on the antibody reactivity of human lymphoma B cells.

Hyper-N-glycosylated SEL1L3 as auto-antigenic B-cell receptor target of primary vitreoretinal lymphomas

Primary vitreoretinal lymphoma (PVRL) is a rare subtype of DLBCL and can progress into primary central nervous system lymphoma (PCNSL). To investigate the role of chronic antigenic stimulation in PVRL, we cloned and expressed B-cell receptors (BCR) from PVRL patients and tested for binding against human auto-antigens. SEL1L3, a protein with multiple glycosylation sites, was identified as the BCR target in 3/20 PVRL cases. SEL1L3 induces proliferation and BCR pathway activation in aggressive lymphoma cell lines. Moreover, SEL1L3 conjugated to a toxin killed exclusively lymphoma cells with respective BCR-reactivity. Western Blot analysis indicates the occurrence of hyper-N-glycosylation of SEL1L3 at aa 527 in PVRL patients with SEL1L3-reactive BCRs. The BCR of a PVRL patient with serum antibodies against SEL1L3 was cloned from a vitreous body biopsy at diagnosis and of a systemic manifestation at relapse. VH4-04*07 was used in both lymphoma manifestations with highly conserved CDR3 regions. Both BCRs showed binding to SEL1L3, suggesting continued dependence of lymphoma cells on antigen stimulation. These results indicate an important role of antigenic stimulation by post-translationally modified auto-antigens in the genesis of PVRL. They also provide the basis for a new treatment approach targeting unique lymphoma BCRs with ultimate specificity.

Diffuse large B-cell lymphoma involving the central nervous system: biologic rationale for targeted therapy

Diffuse large B-cell lymphoma (DLBCL) is an aggressive B-cell lymphoma curable even in advanced stages. DLBCL involving the central nervous system (CNS) is more difficult to cure and fewer treatment options exist. Primary CNS lymphoma (PCNSL) refers to aggressive lymphomas confined to the CNS, and are almost always DLBCL. Standard approaches for PCNSL use high-dose methotrexate-based combinations as induction therapy and younger patients often receive dose-intensive consolidation. However, dose-intensive therapies are not suitable for all patients, and older patients have fewer effective treatment options. Patients with relapsed or chemotherapy-refractory disease have a very poor prognosis. Secondary CNS lymphoma (SCNSL) describes aggressive lymphomas involving the CNS at initial presentation or relapses within the CNS after treatment for systemic DLBCL. Isolated CNS relapse is often managed as PCNSL, but patients with synchronous involvement of DLBCL in both the periphery and the CNS pose a unique clinical challenge. Insights into the molecular circuitry of DLBCL have identified distinct genetic subtypes including cases with a predilection for CNS invasion. PCNSL and subsets of SCNSL are characterized by chronically activated B-cell receptor and NFκB signaling along with genetic evidence of immune evasion which may be exploited therapeutically. Improved mechanistic understanding of targetable pathways underpinning CNS lymphomas has led to numerous clinical trials testing targeted agent combinations and immunotherapy approaches with promising early results. Biologically rational strategies may further improve the cure rate of CNS lymphomas, either by overcoming intrinsic or acquired treatment resistance and/or by being broadly applicable to patients of all ages.

Diagnostic, Pathologic, and Therapeutic Considerations for Primary CNS Lymphoma

Primary CNS lymphoma (PCNSL) is a rare lymphoma representing 3% of CNS malignancies. The diagnosis is complicated by the unique risks associated with brain biopsy, and the treatment is similarly complicated by the restriction of effective therapeutics able to cross the blood-brain barrier. Currently, the majority of individuals diagnosed with this disease are immunocompetent although immune deficiency related to HIV or immunosuppressive therapy remains an important risk factor. Improvements in both frontline therapy and consolidation options, including the use of hematopoietic stem-cell transplantation, have translated to improved survival. Unfortunately, patients experiencing relapsed or refractory disease often fare poorly. Here, we review key clinical, pathologic, and therapeutic aspects of PCNSL and highlight challenging clinical scenarios that may be encountered by the treating oncologist.

Primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a diffuse large B cell lymphoma in which the brain, spinal cord, leptomeninges and/or eyes are exclusive sites of disease. Pathophysiology is incompletely understood, although a central role seems to comprise immunoglobulins binding to self-proteins expressed in the central nervous system (CNS) and alterations of genes involved in B cell receptor, Toll-like receptor and NF-κB signalling. Other factors such as T cells, macrophages or microglia, endothelial cells, chemokines, and interleukins, probably also have important roles. Clinical presentation varies depending on the involved regions of the CNS. Standard of care includes methotrexate-based polychemotherapy followed by age-tailored thiotepa-based conditioned autologous stem cell transplantation and, in patients unsuitable for such treatment, consolidation with whole-brain radiotherapy or single-drug maintenance. Personalized treatment, primary radiotherapy and only supportive care should be considered in unfit, frail patients. Despite available treatments, 15-25% of patients do not respond to chemotherapy and 25-50% relapse after initial response. Relapse rates are higher in older patients, although the prognosis of patients experiencing relapse is poor independent of age. Further research is needed to identify diagnostic biomarkers, treatments with higher efficacy and less neurotoxicity, strategies to improve the penetration of drugs into the CNS, and roles of other therapies such as immunotherapies and adoptive cell therapies.

AMD3100-mediated CXCR4 inhibition impairs development of primary lymphoma of the central nervous system

A hallmark of primary lymphoma of the central nervous system (PCNSL, CNS) is the strong CXCR4 expression of the tumor cells, the function of which is still unknown. In vitro treatment of BAL17^CNS lymphoma cells by AMD3100 which inhibits CXCR4-CXCL12 interactions resulted in the significantly differential expression of 273 genes encoding proteins involved in cell motility, cell-cell signaling and interaction, hematological system development and function, and immunological disease. Among the genes downregulated was the one encoding CD200, a regulator of CNS immunological activity. These data directly translated into the in vivo situation; BAL17^CNS CD200 expression was downregulated by 89% (3% vs. 28% CD200+ lymphoma cells) in AMD3100-treated vs. untreated mice with BAL17^CNS-induced PCNSL. Reduced lymphoma cell CD200 expression may contribute to the markedly increased microglial activation in AMD3100-treated mice. AMD3100 also maintained the structural integrity of blood-brain barrier tight junctions and the outer basal lamina of cerebral blood vessels. Subsequently, lymphoma cell invasion of the brain parenchyma was impaired and maximal parenchymal tumor size was significantly reduced by 82% in the induction phase. Thus, AMD3100 qualified as potentially attractive candidate to be included into the therapeutic concept of PCNSL. Beyond therapy, CXCR4-induced suppression of microglial activity is of general neuroimmunological interest and identifies CD200 expressed by the lymphoma cells as a novel mechanism of immune escape in PCNSL.

Large B-Cell Lymphomas in the 5th Edition of the WHO-Classification of Haematolymphoid Neoplasms-Updated Classification and New Concepts

The family/class of the large B-cell lymphomas (LBCL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) features only a few major changes as compared to the 4th edition. In most entities, there are only subtle changes, many of them only representing some minor modifications in diagnostic terms. Major changes have been made in the diffuse large B-cell lymphomas (DLBCL)/high-grade B-cell lymphomas (HGBL) associated with MYC and BCL2 and/or BCL6 rearrangements. This category now consists of MYC and BCL2 rearranged cases exclusively, while the MYC/BCL6 double hit lymphomas now constitute genetic subtypes of DLBCL, not otherwise specified (NOS) or of HGBL, NOS. Other major changes are the conceptual merger of lymphomas arising in immune-privileged sites and the description of LBCL arising in the setting of immune dysregulation/deficiency. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of the different entities are provided.

The Immunology of DLBCL

Diffuse large B-cell lymphoma (DLBCL) is an aggressive malignancy and is the most common type of malignant lymphoid neoplasm. While some DLBCLs exhibit strong cell-autonomous survival and proliferation activity, others depend on interactions with non-malignant cells for their survival and proliferation. Recent next-generation sequencing studies have linked these interactions with the molecular classification of DLBCL. For example, germinal center B-cell-like DLBCL tends to show strong associations with follicular T cells and epigenetic regulation of immune recognition molecules, whereas activated B-cell-like DLBCL shows frequent genetic aberrations affecting the class I major histocompatibility complex. Single-cell technologies have also provided detailed information about cell-cell interactions and the cell composition of the microenvironment of DLBCL. Aging-related immunological deterioration, i.e., immunosenescence, also plays an important role in DLBCL pathogenesis, especially in Epstein-Barr virus-positive DLBCL. Moreover, DLBCL in "immune-privileged sites"-where multiple immune-modulating mechanisms exist-shows unique biological features, including frequent down-regulation of immune recognition molecules and an immune-tolerogenic tumor microenvironment. These advances in understanding the immunology of DLBCL may contribute to the development of novel therapies targeting immune systems.

Cell of Origin of Brain and Spinal Cord Tumors

A better understanding of cellular and molecular biology of primary central nervous system (CNS) tumors is a critical step toward the design of innovative treatments. In addition to improving knowledge, identification of the cell of origin in tumors allows for sharp and efficient targeting of specific tumor cells promoting and driving oncogenic processes. The World Health Organization identifies approximately 150 primary brain tumor subtypes with various ontogeny and clinical outcomes. Identification of the cell of origin of each tumor type with its lineage and differentiation level is challenging. In the current chapter, we report the suspected cell of origin of various CNS primary tumors including gliomas, glioneuronal tumors, medulloblastoma, meningioma, atypical teratoid rhabdoid tumor, germinomas, and lymphoma. Most of them have been pinpointed through transgenic mouse models and analysis of molecular signatures of tumors. Identification of the cell or cells of origin in primary brain tumors will undoubtedly open new therapeutic avenues, including the reactivation of differentiation programs for therapeutic perspectives.

Lymphomas of Central Nervous System

Central nervous system (CNS) lymphoma consists of primary central nervous system lymphoma (PCNSL) and secondary CNS involvement by systemic lymphoma. This chapter focuses on the former. PCNSL is a relative rare disease, accounting for approximately 2.4-4.9% of all primary CNS tumors. It is an extra-nodal variant of non-Hodgkin's lymphoma (NHL), confined to the brain, leptomeninges, spinal cord, and eyes, with no systemic involvement. Recently, elderly patients (≥ 60 years) are increasing. Histologically, B cell blasts, which originate from late germinal center exit B cell, are growing and homing in CNS. Immunohistochemically, these cells are positive for PAX5, CD19, CD20, CD22, and CD79a. PCNSL shows relatively characteristic appearances on CT, MR imaging, and PET. Treatment first line of PCNSL is HD-MTX-based chemotherapy with or without rituximab and irradiation. Severe side-effect of this treatment is delayed onset neurotoxicity, which cause of cognitive impairment. Therefore, combined chemotherapy alone or chemotherapy with reduced-dose irradiation is more recommended for elderly patients. There is no established standard care for relapse of the PCNSLs. Temsirolimus, lenalidomide, temozolomide, and Bruton's tyrosine kinase (BTK) inhibitor ibrutinib are candidates for refractory patients. The prognosis of PCNSL has significantly improved over the last decades (median OS: 26 months, 5-year survival: 31%). Younger than 60 age and WHO performance status less than < or = 1 are associated with a significantly better overall survival.

Systemic inflammatory biomarkers in primary central nervous system lymphoma versus high-grade glioma: exploratory, comparative and correlative analysis

Aim:

To assess systemic inflammatory biomarkers in non invasive differential diagnosis of primary central nervous system lymphoma (PCNSL) from high-grade glioma (HGG).

Materials & methods:

Patients with similar morphology (PCNSL or HGG) on conventional neuro-imaging were included. Systemic inflammatory indices were calculated from pretreatment complete blood counts and liver function tests and compared against histopathology as reference standard.

Results:

Mean values of absolute lymphocyte count and prognostic nutritional index were significantly different between PCNSL (n = 42) versus HGG (n = 16). Area under receiver operating characteristics curve for absolute lymphocyte count and prognostic nutritional index in the diagnosis of PCNSL was 0.70 and 0.72 respectively suggesting fair and acceptable diagnostic accuracy.

Conclusion:

Systemic inflammatory biomarkers complement established clinico-radiological features and aid in the differential diagnosis of PCNSL from HGG.

There exists a complex interplay between cancer and inflammation that can manifest as increased inflammatory biomarkers in blood. However, utility of systemic inflammatory biomarkers in the non invasive differential diagnosis of primary brain lymphoma from high-grade glioma is generally lacking. Two simple serum biomarkers, absolute lymphocyte count and prognostic nutritional index, easily derived from routine pretreatment blood tests have fair correlation and acceptable diagnostic accuracy in differentiating brain lymphoma from glioma in patients with similar morphology on MRI.

Impact of a Faulty Germinal Center Reaction on the Pathogenesis of Primary Diffuse Large B Cell Lymphoma of the Central Nervous System

Simple Summary

The pathogenetic mechanisms and peculiar tropism of primary CNS lymphoma (PCNSL) of the central nervous system (CNS) have been the subject of debate for decades. Hypothesis-driven targeted molecular studies have revealed that PCNSLs derived from self-/polyreactive B cells that have escaped developmental control mechanisms. The early acquisition of activating mutations targeting the B cell receptor pathway provides a survival advantage. The failure of the germinal center (GC) reaction and its checkpoints increases tumor B cell affinity for the CNS. During this faulty GC reaction, PCNSL tumor cells acquire further oncogenic alterations converging on the Toll-like receptor, B cell receptor, and NF-κB pathway. These activated pathways sustain proliferation. Concomitantly, cells become unable to complete terminal B cell differentiation, becoming trapped within the vicious cycle of the GC reaction as low-affinity IgM+ B cells related to memory cells.

Abstract

Primary lymphoma of the central nervous system (PCNSL, CNS) is a specific diffuse large B cell lymphoma (DLBCL) entity confined to the CNS. Key to its pathogenesis is a failure of B cell differentiation and a lack of appropriate control at differentiation stages before entrance and within the germinal center (GC). Self-/polyreactive B cells rescued from apoptosis by MYD88 and/or CD79B mutations accumulate a high load of somatic mutations in their rearranged immunoglobulin (IG) genes, with ongoing somatic hypermutation (SHM). Furthermore, the targeting of oncogenes by aberrant SHM (e.g., PIM1, PAX5, RHOH, MYC, BTG2, KLHL14, SUSD2), translocations of the IG and BCL6 genes, and genomic instability (e.g., gains of 18q21; losses of 9p21, 8q12, 6q21) occur in these cells in the course of their malignant transformation. Activated Toll-like receptor, B cell receptor (BCR), and NF-κB signaling pathways foster lymphoma cell proliferation. Hence, tumor cells are arrested in a late B cell differentiation stage, corresponding to late GC exit B cells, which are genetically related to IgM+ memory cells. Paradoxically, the GC reaction increases self-/polyreactivity, yielding increased tumor BCR reactivity for multiple CNS proteins, which likely contributes to CNS tropism of the lymphoma. The loss of MHC class I antigen expression supports tumor cell immune escape. Thus, specific and unique interactions of the tumor cells with resident CNS cells determine the hallmarks of PCNSL.

Update on Novel Therapeutics for Primary CNS Lymphoma

Simple Summary

Primary central nervous system lymphoma is a rare and aggressive form of non-Hodgkin lymphoma. While it is highly responsive to first-line chemo and radiation treatments, rates of relapse are high, demonstrating the need for improved therapeutic strategies. Recent advancements in the understanding of the pathophysiology of this disease have led to the identification of new potential treatment targets and the development of novel agents. This review aims to discuss different targeted strategies and review some of the data supporting these approaches, and discusses recently completed and ongoing clinical trials using these novel agents.

Abstract

Primary central nervous system lymphoma (PCNSL) is a rare lymphoma isolated to the central nervous system or vitreoretinal space. Standard treatment consists of cytotoxic methotrexate-based chemotherapy, with or without radiation. Despite high rates of response, relapse is common, highlighting the need for novel therapeutic approaches. Recent advances in the understanding of PCNSL have elucidated mechanisms of pathogenesis and resistance including activation of the B-cell receptor and mammalian target of rapamycin pathways. Novel treatment strategies such as the Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib, phosphatidylinositol-3 kinase (PI3K) inhibitors, and immunomodulatory drugs are promising. Increasingly, evidence suggests immune evasion plays a role in PCNSL pathogenesis and several immunotherapeutic strategies including checkpoint inhibition and targeted chimeric antigen receptor T (CAR-T) cells are under investigation. This review provides a discussion on the challenges in development of targeted therapeutic strategies, an update on recent treatment advances, and offers a look toward ongoing clinical studies.

Analysis of Cellular Heterogeneity in Immune Microenvironment of Primary Central Nervous System Lymphoma by Single-Cell Sequencing

Background

Primary central nervous system lymphoma (PCNSL) is characterized by a lack of specificity and poor prognosis. Further understanding of the tumor heterogeneity and molecular phenotype of PCNSL is of great significance for improving the diagnosis and treatment of this disease.

Methods

To explore the distinct phenotypic states of PCNSL, transcriptome-wide single-cell RNA sequencing was performed on 34,851 PCNSL cells from patients. The cell types, heterogeneity, and gene subset enrichment of PCNSL were identified. A comparison of the PCNSL cells with 21,250 normal human fetal brain (nHFB) cells was further analyzed to reveal the differences between PCNSL and normal sample.

Results

Six cell populations were mainly identified in the PCNSL tissue, including four types of immune cells—B cell, T cell, macrophage and dendritic cell—and two types of stromal cells: oligodendrocyte and meningeal cell. There are significant cellular interactions between B cells and several other cells. Three subpopulations of B cells indicating diffident functions were identified, as well as a small number of plasma cells. Different subtypes of T cells and dendritic cells also showed significant heterogeneity. It should be noted that, compared with normal, the gene expression and immune function of macrophages in PCNSL were significantly downregulated, which may be another important feature of PCNSL in addition to B cell lesions and may be a potential target for PCNSL therapy.

Primary vitreoretinal lymphomas display a remarkably restricted immunoglobulin gene repertoire

Primary vitreoretinal lymphoma (PVRL) is a high-grade lymphoma affecting the vitreous and/or the retina. The vast majority of cases are histopathologically classified as diffuse large B-cell lymphoma (DLBCL) and considered a subtype of primary central nervous system lymphoma (PCNSL). To obtain more insight into the ontogenetic relationship between PVRL and PCNSL, we adopted an immunogenetic perspective and explored the respective immunoglobulin gene repertoire profiles from 55 PVRL cases and 48 PCNSL cases. In addition, considering that both entities are predominantly related to activated B-cell (ABC) DLBCL, we compared their repertoire with that of publicly available 262 immunoglobulin heavy variable domain gene rearrangement sequences from systemic ABC-type DLBCLs. PVRL displayed a strikingly biased repertoire, with the IGHV4-34 gene being used in 63.6% of cases, which was significantly higher than in PCNSL (34.7%) or in DLBCL (30.2%). Further repertoire bias was evident by (1) restricted associations of IGHV4-34 expressing heavy chains, with κ light chains utilizing the IGKV3-20/IGKJ1 gene pair, including 5 cases with quasi-identical sequences, and (2) the presence of a subset of stereotyped IGHV3-7 rearrangements. All PVRL IGHV sequences were highly mutated, with evidence of antigen selection and ongoing mutations. Finally, half of PVRL and PCNSL cases carried the MYD88 L265P mutation, which was present in all 4 PVRL cases with stereotyped IGHV3-7 rearrangements. In conclusion, the massive bias in the immunoglobulin gene repertoire of PVRL delineates it from PCNSL and points to antigen selection as a major driving force in their development.

Emerging insights into origin and pathobiology of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is an aggressive cancer typically confined to the brain, eyes, leptomeninges and spinal cord, without evidence of systemic involvement. PCNSL remains a challenge for scientists and clinicians due to insufficient biological knowledge, a lack of appropriate animal models and validated diagnostic biomarkers. We summarize recent findings on genomic, transcriptomic and epigenetic alterations identified in PCNSL. These findings help to define pathobiology of the disease and delineate defects in B cell differentiation. Evidence from genomic and transcriptomic studies helps to separate PCNSL from other hematological malignancies, improves diagnostics and reveals new therapeutic targets for treatment. Discovery of the CNS lymphatic system may be instrumental in better understanding the origin of the disease. We critically assess the attempts to model PCNSL in rodents, and conclude that there is a lack of a genetic/transgenic model that adequately mimics pathogenesis of the disease. Contribution of the tumor microenvironment in tumorigenesis and aggressiveness of PCNSL remains understudied. Assessing heterogeneity of immune infiltrates, cytokine profiling and molecular markers, may improve diagnostics and put forward new therapeutic strategies.

The process of somatic hypermutation increases polyreactivity for central nervous system antigens in primary central nervous system lymphoma

The immunoglobulin (Ig) heavy and light chain variable gene mutational pattern of the B-cell receptor (BCR) in primary central nervous system lymphoma (PCNSL) cells suggests antigenic selection to drive pathogenesis and confinement to the central nervous system (CNS). This hypothesis is supported by the observation that the tumor B-cell receptor (tBCR) of PCNSL is polyreactive and may be stimulated by CNS proteins. To obtain further insight into the role of the germinal center (GC) reaction on BCR reactivity, we constructed recombinant antibodies (recAb) with Ig heavy and light chain sequences of the corresponding naïve BCR (nBCR) by reverting tBCR somatic mutations in ten PCNSL. Analysis of nBCR-derived recAb reactivity by a protein microarray and immunoprecipitation demonstrated auto- and polyreactivity in all cases. Self- /polyreactivity was not lost during the GC reaction; surprisingly, tBCR significantly increased self-/polyreactivity. In addition to proteins recognized by both the nBCR and tBCR, tBCR gained self-/polyreactivity particularly for proteins expressed in the CNS including proteins of oligodendrocytes/ myelin, the S100 protein family, and splicing factors. Thus, in PCNSL pathogenesis, a faulty GC reaction may increase self-/polyreactivity, hereby facilitating BCR signaling via multiple CNS antigens, and may ultimately foster tumor cell survival in the CNS.

Primary Central Nervous System Lymphomas: A Diagnostic Overview of Key Histomorphologic, Immunophenotypic, and Genetic Features

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal non-Hodgkin lymphoma that primarily arises in the brain, spinal cord, leptomeninges, and vitreoretinal compartment of the eye. The term is sometimes used interchangeably with primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) because DLBCL comprises a great majority (90–95%) of PCNSL. Although rare, other types of lymphomas can be seen in the central nervous system (CNS), and familiarity with these entities will help their recognition and further workup in order to establish the diagnosis. The latter is especially important in the case of PCNSL where procurement of diagnostic specimen is often challenging and yields scant tissue. In this review, we will discuss the most common types of primary lymphomas that can be seen in the CNS with emphasis on the diagnostic histomorphologic, immunophenotypic, and molecular genetic features. The differential diagnostic approach to these cases and potential pitfalls will also be discussed.

Role of Specific B-Cell Receptor Antigens in Lymphomagenesis

The B-cell receptor (BCR) signaling pathway is a crucial pathway of B cells, both for their survival and for antigen-mediated activation, proliferation and differentiation. Its activation is also critical for the genesis of many lymphoma types. BCR-mediated lymphoma proliferation may be caused by activating BCR-pathway mutations and/or by active or tonic stimulation of the BCR. BCRs of lymphomas have frequently been described as polyreactive. In this review, the role of specific target antigens of the BCRs of lymphomas is highlighted. These antigens have been found to be restricted to specific lymphoma entities. The antigens can be of infectious origin, such as H. pylori in gastric MALT lymphoma or RpoC of M. catarrhalis in nodular lymphocyte predominant Hodgkin lymphoma, or they are autoantigens. Examples of such autoantigens are the BCR itself in chronic lymphocytic leukemia, LRPAP1 in mantle cell lymphoma, hyper-N-glycosylated SAMD14/neurabin-I in primary central nervous system lymphoma, hypo-phosphorylated ARS2 in diffuse large B-cell lymphoma, and hyper-phosphorylated SLP2, sumoylated HSP90 or saposin C in plasma cell dyscrasia. Notably, atypical posttranslational modifications are often responsible for the immunogenicity of many autoantigens. Possible therapeutic approaches evolving from these specific antigens are discussed.

Integration of the B-Cell Receptor Antigen Neurabin-I/SAMD14 Into an Antibody Format as New Therapeutic Approach for the Treatment of Primary CNS Lymphoma

Recently, neurabin-I and SAMD14 have been described as the autoantigenic target of approximately 66% of B-cell receptors (BCRs) of primary central nervous system lymphomas (PCNSL). Neurabin-I and SAMD14 share a highly homologous SAM domain that becomes immunogenic after atypical hyper-N-glycosylation (SAMD14 at ASN339 and neurabin-I at ASN1277). This post-translational modification of neurabin-I and SAMD14 seems to lead to a chronic immune reaction with B-cell receptor activation contributing to lymphoma genesis of PCNSLs. The selective tropism of PCNSL to the CNS corresponds well to the neurabin-I and SAMD14 protein expression pattern. When conjugated to Pseudomonas Exotoxin A (ETA´), the PCNSL reactive epitope exerts cytotoxic effects on lymphoma cells expressing a SAMD14/neurabin-I reactive BCR. Thus, the reactive epitopes of SAMD14/neurabin-I might be useful to establish additional therapeutic strategies against PCNSL. To test this possibility, we integrated the PCNSL-reactive epitope of SAMD14/neurabin-I into a heavy-chain-only Fab antibody format in substitution of the variable region. Specific binding of the prokaryotically produced SAMD14/neurabin-I Fab-antibody to lymphoma cells and their internalization were determined by flow cytometry. Since no established EBV-negative PCNSL cell line exists, we used the ABC-DLBCL cell lines OCI-Ly3 and U2932, which were transfected to express a SAMD14/neurabin-I reactive BCR. The SAMD14/neurabin-I Fab antibody bound specifically to DLBCL cells expressing a BCR with reactivity to SAMD14/neurabin-I and not to unmanipulated DLBCL cell lines. Eukaryotically produced full-length IgG antibodies are well established as immunotherapy format. Therefore, the PCNSL-reactive epitope of SAMD14/neurabin-I was cloned into a full-length IgG1 format replacing the variable domains of the light and heavy chains. The IgG1-format SAMD14/neurabin-I construct was found to specifically bind to target lymphoma cells expressing a SAMD14/neurabin-I reactive B cell receptor. In addition, it induced dose-dependent relative cytotoxicity against these lymphoma cells when incubated with PBMCs. Control DLBCL cells are not affected at any tested concentration. When integrated into the Fab-format and IgG1-format, the PCNSL-reactive epitope of SAMD14/neurabin-I functions as B-cell receptor Antigen for Reverse targeting (BAR). In particular, the IgG1-format BAR-body approach represents a very attractive therapeutic format for the treatment of PCNSLs, considering its specificity against SAMD14/neurabin-I reactive BCRs and the well-known pharmacodynamic properties of IgG antibodies.

Analysis of Driver Mutational Hot Spots in Blood-Derived Cell-Free DNA of Patients with Primary Central Nervous System Lymphoma Obtained before Intracerebral Biopsy

In newly diagnosed systemic diffuse large B-cell lymphoma, next-generation sequencing of plasma-derived cell-free DNA (cfDNA) detects somatic mutations as accurate as genotyping of the tumor biopsy. A distinct diffuse large B-cell lymphoma entity confined to the central nervous system is primary central nervous system lymphoma (PCNSL), which requires intracerebral biopsy and neuropathologic analysis to establish the diagnosis. So far, a biomarker for diagnosis and follow-up of PCNSL that can be investigated in blood has not been identified. This article addresses the question whether somatic mutations of the CD79B and MYD88 driver genes of PCNSL can be detected in cfDNA at disease diagnosis. Stereotactic biopsies and cfDNA of 27 PCNSL patients were analyzed for CD79B and MYD88 mutations. As control, cfDNA derived from six healthy volunteers was used. CD79B and MYD88 hot spot mutations were identified in 16 of 27 (59%) and 23 of 27 (85%) PCNSL biopsies, respectively, but only in 0 of 27 (0%) and 1 of 27 (4%) corresponding cfDNA samples, respectively. In cfDNA of one of four patients with Waldenstrom disease, as a further control, the MYD88 L265P mutation was readily detected, despite complete clinical remission. These data suggest that in PCNSL even if they carry such mutations, alterations of CD79B and MYD88 cannot be reliably detected in blood-derived cfDNA obtained before intracerebral biopsy.

Molecular Subtypes and Genomic Profile of Primary Central Nervous System Lymphoma

Primary central nervous system lymphomas (PCNSL) are aggressive non-Hodgkin lymphomas affecting the central nervous system (CNS). Although immunophenotyping studies suggested an uniform activated B-cell (ABC) origin, more recently a spectrum of ABC and germinal center B-cell (GC) cases has been proposed, with the molecular subtypes of PCNSL still being a matter of debate. With the emergence of novel therapies demonstrating different efficacy between the ABC and GC patient groups, precise assignment of molecular subtype is becoming indispensable. To determine the molecular subtype of 77 PCNSL and 17 secondary CNS lymphoma patients, we used the NanoString Lymphoma Subtyping Test (LST), a gene expression-based assay representing a more accurate technique of subtyping compared with standard immunohistochemical (IHC) algorithms. Mutational landscapes of 14 target genes were determined using ultra-deep next-generation sequencing. Using the LST-assay, a significantly lower proportion (80% vs 95%) of PCNSL cases displayed ABC phenotype compared with the IHC-based characterization. The most frequently mutated genes included MYD88, PIM1, and KMT2D. In summary, we successfully applied the LST-assay for molecular classification of PCNSL, reporting higher proportion of cases with GC phenotype compared with IHC analyses, leading to a more precise patient stratification potentially applicable in the diagnostic algorithm of PCNSL.

The Neutrophil to Lymphocyte and Lymphocyte to Monocyte Ratios as New Prognostic Factors in Hematological Malignancies - A Narrative Review

Despite the presence of many hematological prognostic indexes, clinical course and overall survival are often highly variable even within the same patient subgroup. Recent studies suggest that simple, cost-effective, low-risk tests such as neutrophil to lymphocyte ratio (NLR) and lymphocyte to monocyte ratio (LMR) may be used to evaluate the prognosis. Their role has been well confirmed in diffuse large B-cell lymphoma (DLBCL), Hodgkin lymphoma (HL) and multiple myeloma (MM), but until now the prognostic significance of NLR and LMR in leukemias has not been widely reported. In this article, we analyze the literature data on prognostic value of NLR and LMR in haematological malignancies in the context of classic prognostic factors and clinical course.

Expression Cloning of Antibodies from Single Human B Cells

The majority of lymphomas originate from B cells at the germinal center stage. Preferential selection of B-cell clones by a limited set of antigens has been suggested to drive lymphoma development. While recent studies in chronic lymphocytic leukemia have shown that self-reactive B-cell receptors (BCR) can generate cell-autonomous signaling and proliferation, our knowledge about the role of BCRs for the development or survival of other lymphomas remains limited. Here, we describe a strategy to characterize the antibody reactivity of human B cells. The approach allows the unbiased characterization of the human antibody repertoire at single-cell level through the generation of recombinant monoclonal antibodies from single primary human B cells of defined origin. This protocol offers a detailed description of the method starting from the flow-cytometric isolation of single human B cells to the reverse transcription-polymerase chain reaction (RT-PCR)-based amplification of the expressed immunoglobulin (Ig) transcripts (IGH, IGK, and IGL) and their subsequent cloning into expression vectors for the in vitro production of recombinant monoclonal antibodies. The strategy may be used to obtain information on the clonal evolution of B-cell lymphomas by single-cell sequencing of Ig transcripts and on the antibody reactivity of human lymphoma B cells.

Genetic evidence implies that primary and relapsed tumors arise from common precursor cells in primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare subtype of lymphoma that arises within the brain or the eyes. PCNSL recurs within the central nervous system (CNS) in most relapsed cases, whereas extra‐CNS relapse is experienced in rare cases. The present study aimed at identifying the presence of common precursor cells (CPC) for primary intra‐ and relapsed extra‐CNS tumors, and further assessing the initiating events in bone marrow (BM). Targeted deep sequencing was carried out for five paired primary intra‐ and relapsed extra‐CNS tumors of PCNSL. Two to five mutations were shared by each pair of intra‐ and extra‐CNS tumors. In particular, MYD88 mutations, L265P in three and P258L in one, were shared by four pairs. Unique somatic mutations were observed in all five intra‐CNS tumors and in four out of five extra‐CNS tumors. Remarkably, IgH clones in the intra‐ and the extra‐CNS tumors in two pairs were distinct from each other, whereas one pair of tumors shared identical monoclonal IgH rearrangement. In a cohort of 23 PCNSL patients, L265P MYD88 mutations were examined in tumor‐free BM mononuclear cells (MNC) in which the PCNSL tumors had L265P MYD88 mutations. L265P MYD88 mutations were detected by a droplet digital PCR method in nine out of 23 bone marrow mononuclear cells. These results suggest that intra‐ and extra‐tumors are derived from CPC with MYD88 mutations in most PCNSL, arising either before or after IgH rearrangement. The initiating MYD88 mutations may occur during B‐cell differentiation in BM.

Hyper-N-glycosylated SAMD14 and neurabin-I as driver autoantigens of primary central nervous system lymphoma

To address the role of chronic antigenic stimulation in primary central nervous system lymphoma (PCNSL), we searched for autoantigens and identified sterile α-motif domain containing protein 14 (SAMD14) and neural tissue-specific F-actin binding protein I (neurabin-I) as autoantigenic targets of the B-cell receptors (BCRs) from 8/12 PCNSLs. In the respective cases, SAMD14 and neurabin-I were atypically hyper-N-glycosylated (SAMD14 at ASN339 and neurabin-I at ASN1277), explaining their autoimmunogenicity. SAMD14 and neurabin-I induced BCR pathway activation and proliferation of aggressive lymphoma cell lines transfected with SAMD14- and neurabin-I-reactive BCRs. Moreover, the BCR binding epitope of neurabin-I conjugated to truncated Pseudomonas exotoxin-killed lymphoma cells expressing the respective BCRs. These results support the role of chronic antigenic stimulation by posttranslationally modified central nervous system (CNS) driver autoantigens in the pathogenesis of PCNSL, serve as an explanation for their CNS tropism, and provide the basis for a novel specific treatment approach.

Identification of novel recurrent ETV6-IgH fusions in primary central nervous system lymphoma

Background

Primary central nervous system lymphoma (PCNSL) represents a particular entity within non-Hodgkin lymphomas and is associated with poor outcome. The present study addresses the potential clinical relevance of chimeric transcripts in PCNSL discovered by using RNA sequencing (RNA-seq).

Methods

Seventy-two immunocompetent and newly diagnosed PCNSL cases were included in the present study. Among them, 6 were analyzed by RNA-seq to detect new potential fusion transcripts. We confirmed the results in the remaining 66 PCNSL. The gene fusion was validated by fluorescence in situ hybridization (FISH) using formalin-fixed paraffin-embedded (FFPE) samples. We assessed the biological and clinical impact of one new gene fusion.

Results

We identified a novel recurrent gene fusion, E26 transformation-specific translocation variant 6-immunoglobulin heavy chain (ETV6-IgH). Overall, ETV6-IgH was found in 13 out of 72 PCNSL (18%). No fusion conserved an intact functional domain of ETV6, and ETV6 was significantly underexpressed at gene level, suggesting an ETV6 haploinsufficiency mechanism. The presence of the gene fusion was also validated by FISH in FFPE samples. Finally, PCNSL samples harboring ETV6-IgH showed a better prognosis in multivariate analysis, P = 0.03, hazard ratio = 0.33, 95% CI = 0.12-0.88. The overall survival at 5 years was 69% for PCNSL harboring ETV6-IgH versus 29% for samples without this gene fusion.

Conclusions

ETV6-IgH is a new potential surrogate marker of PCNSL with favorable prognosis with ETV6 haploinsufficiency as a possible mechanism. The potential clinical impact of ETV6-IgH should be validated in larger prospective studies.

Prognostic role of the neutrophil-to-lymphocyte ratio in patients with primary central nervous system lymphoma

Neutrophil-to-lymphocyte ratio (NLR) is one of the parameters of a complete blood cell count (CBC) test and has been reported to be an easily accessible prognostic marker in aggressive cancer, including non-Hodgkin lymphoma (NHL). Primary central nervous system lymphoma (PCNSL) is an extranodal NHL with highly aggressive features. However, the importance of the NLR has never been assessed in PCNSL. This retrospective study enrolled 62 biopsy-proven patients whose baseline NLR was available, and reviewed their medical records to compare both high (≥2.0) and low NLR (<2.0) groups, in terms of clinical characteristics and outcomes. The low NLR group showed significantly better response rates to induction chemotherapy compared to the high NLR group (p=0.041). At a median follow-up of 41.5 months, the high NLR group revealed a significantly worse 3-year overall survival (OS) (42.5 vs. 71.2%; p=0.031) and a worse 3-year progression-free survival (PFS) (37.3 vs. 60.1%; p=0.028). Univariable Cox analysis results showed that a high NLR at diagnosis was a poor prognostic factor for both 3-year OS (HR 2.64, 95% CI 1.06-6.60; p=0.038) and 3-year PFS (HR 2.41, 95% CI 1.07-5.42; p=0.034). However, multivariable analyses adjusting for International Extranodal Lymphoma Study Group (IELSG) score and induction chemotherapy regimen with rituximab, which were strongly prognostic in this study, showed no statistical significance even with the high NLR group's tendency towards a worse 3-year OS (HR 2.36, 95% CI 0.84-6.62, p=0.102) and a worse 3-year PFS (HR 2.28, 95% CI 0.93-5.63, p=0.073). In conclusion, given that NLR is simple and easily obtainable, it might play a potentially prognostic role in PCNSL from early disease onset.

Patterns of relapse in primary central nervous system lymphoma: inferences regarding the role of the neuro-vascular unit and monoclonal antibodies in treating occult CNS disease

Background and purpose

The radiologic features and patterns of primary central nervous system lymphoma (PCNSL) at initial presentation are well described. High response rates can be achieved with first-line high-dose methotrexate (HD-MTX) based regimens, yet many relapse within 2 years of diagnosis. We describe the pattern of relapse and review the potential mechanisms involved in relapse.

Methods

We identified 78 consecutive patients who attained complete radiographic response (CR) during or after first-line treatment for newly diagnosed PCNSL (CD20+, diffuse large B cell type). Patients were treated with HD-MTX based regimen in conjunction with blood–brain barrier disruption (HD-MTX/BBBD); 44 subsequently relapsed. Images and medical records of these 44 consecutive patients were retrospectively reviewed. The anatomical location of enhancing lesions at initial diagnosis and at the time of relapse were identified and compared.

Results

37/44 patients fulfilled inclusion criteria and had new measureable enhancing lesions at relapse; the pattern and location of relapse of these 37 patients were identified. At relapse, the new enhancement was at a spatially distinct site in 30 of 37 patients. Local relapse was found only in seven patients.

Discussion

Unlike gliomas, the majority of PCNSL had radiographic relapse at spatially distinct anatomical locations within the brain behind a previously intact neurovascular unit (NVU), and in few cases outside, the central nervous system (CNS). This may suggest either (1) reactivation of occult reservoirs behind an intact NVU in the CNS (or ocular) or (2) seeding from bone marrow or other extra CNS sites.

Conclusion

Recognizing patterns of relapse is key for early detection and may provide insight into potential mechanisms of relapse as well as help develop strategies to extend duration of complete response.

The Challenge of Primary Central Nervous System Lymphoma

Primary central nervous system (CNS) lymphoma is a challenging subtypes of aggressive non-Hodgkin lymphoma. Emerging clinical data suggest that optimized outcomes are achieved with dose-intensive CNS-penetrant chemotherapy and avoiding whole brain radiotherapy. Anti-CD20 antibody-based immunotherapy as a component of high-dose methotrexate-based induction programs may contribute to improved outcomes. An accumulation of insights into the molecular and cellular basis of disease pathogenesis is providing a foundation for the generation of molecular tools to facilitate diagnosis as well as a roadmap for integration of targeted therapy within the developing therapeutic armamentarium for this challenging brain tumor.

Neural Tumors of the Orbit -- What Is New?

Primary neural tumors of the orbit account for approximately 10% of all orbital tumors. Different tumor entities include meningiomas, optic nerve gliomas, neurofibromas, schwannomas, malignant peripheral nerve sheath tumors, and granular cell tumors. This review summarizes current concepts regarding epidemiology, clinical presentation, diagnosis, pathology, immunohistochemistry, prognosis, and treatment for neural tumors of the orbit based on the available literature.

Primary Vitreoretinal Lymphoma -- A Review

Primary vitreoretinal lymphoma (PVRL) is the most common intraocular lymphoma occurring in the eye. It is a high-grade typically B-cell malignancy, arising in the retina, and is often associated with central nervous system (CNS) disease and thereby a poor prognosis. It needs to be distinguished from choroidal low-grade B-cell lymphomas, which do not disseminate to the brain and have a good prognosis. Because of the rarity of PVRL, information is lacking regarding its true incidence, its geographical or ethnic variation, and underlying risk factors apart from immunosuppression associated with human immunodeficiency virus (HIV) and Epstein Barr virus. PVRL often presents masquerading as other intraocular diseases and is therefore often associated with diagnostic delays. This is compounded by the fragility of the neoplastic B cells, which hampers vitrectomy yields and pathological work-up. The latter includes cytomorphology and immunoprofiling, with adjunctive tests such as cytokine analysis, polymerase chain reaction for clonality, MYD88 mutational testing, and possibly bespoke next generation sequencing. Recent examinations of PVRL and CNS lymphoma (CNSL) using whole genome sequencing confirm that these tumors arise from activated postgerminal center cells, reflecting their aggressive course in most cases. The treatment of PVRL varies between centers and is dependent on presence or absence of concomitant CNS disease. The prognosis remains poor, and yet progress is steadily being made through international collaborative clinical trials.

How we diagnose and treat vitreoretinal lymphoma

The eye is a rare site for the development of malignant lymphoma. Based on cell type and involved intraocular structures, which as a whole represent an immune-privileged site, several subtypes of primary intraocular lymphoma need to be discerned. Primary vitreoretinal lymphoma (PVRL), the most common form, is an aggressive B-cell malignancy and considered a subtype of primary central nervous system (CNS) lymphoma. Ocular symptoms are non-specific and often mimic uveitis, frequently resulting in delayed diagnosis. Bilateral ocular involvement and dissemination/relapse in the CNS are common. Diagnosis of PVRL is usually based on the analysis of vitreous biopsy material. In addition to cytological and immunocytochemical examination, measurements of cytokine levels and molecular determination of B-cell clonality and recurrent mutations increase the diagnostic yield. Both systemic chemotherapy and exclusively local treatment, including ocular radiotherapy and intravitreal chemotherapy, are successful approaches for the management of PVRL, although it is currently not predictable which patients require systemic treatment in order to avoid cerebral dissemination, a complication associated with a considerably worse prognosis.

Primary Central Nervous System (CNS) Lymphoma B Cell Receptors Recognize CNS Proteins

Primary lymphoma of the CNS (PCNSL) is a diffuse large B cell lymphoma confined to the CNS. To elucidate its peculiar organ tropism, we generated recombinant Abs (recAbs) identical to the BCR of 23 PCNSLs from immunocompetent patients. Although none of the recAbs showed self-reactivity upon testing with common autoantigens, they recognized 1547 proteins present on a large-scale protein microarray, indicating polyreactivity. Interestingly, proteins (GRINL1A, centaurin-α, BAIAP2) recognized by the recAbs are physiologically expressed by CNS neurons. Furthermore, 87% (20/23) of the recAbs, including all Abs derived from IGHV4-34 using PCNSL, recognized galectin-3, which was upregulated on microglia/macrophages, astrocytes, and cerebral endothelial cells upon CNS invasion by PCNSL. Thus, PCNSL Ig may recognize CNS proteins as self-Ags. Their interaction may contribute to BCR signaling with sustained NF-κB activation and, ultimately, may foster tumor cell proliferation and survival. These data may also explain, at least in part, the affinity of PCNSL cells for the CNS.

Intraocular Lymphoma Models

Primary vitreoretinal lymphoma (PVRL) is a subtype of primary central nervous system lymphoma (PCNSL), a high-grade, extranodal, non-Hodgkin's lymphoma, predominantly of B-cell origin. PVRL is an aggressive disease with a poor prognosis. Human studies are not ideally suited for the study of intraocular lymphoma pathogenesis or treatment strategies due to the rare nature of the disease, its variable presentation, limited volume of available ocular fluids, and fragility of sampled lymphoma cells. Animal models have been critical in making progress in understanding intraocular lymphoma pathogenesis and investigating potential therapeutic strategies. Early murine models for intraocular lymphoma used intraperitoneal injection of mouse T-cell lymphomas. This was followed by intravitreal T-cell murine models. More recent murine models have used B-cell lymphomas to more closely mimic human disease. The most current B-cell lymphoma models employ a combined approach of inoculating both the mouse vitreous cavity and brain. The challenge in murine models for intraocular lymphoma lies in recreating the clinical features, disease behavior, molecular profile, systemic immunity, and the microenvironment observed in human disease. In the future, animal models will continue to be central to furthering our understanding of the disease and in the investigation of potential treatment targets.

Modern cerebrospinal fluid analyses for the diagnosis of diffuse large B-cell lymphoma of the CNS

CNS lymphomas represent rare and aggressive variants of extranodal non-Hodgkin's lymphomas, which may present with diverse neurological symptoms and are often diagnostically challenging. Primary CNS lymphomas develop within the CNS and characteristically involve the brain, leptomeninges, eyes and, in rare cases, spinal cord. Secondary CNS lymphomas are characterized by expansion of systemic lymphomas to the CNS. Multimodal investigation of cerebrospinal fluid (CSF) comprises an important component of the diagnostic work-up for patients with suspected CNS lymphomas. Cytopathological examination of the CSF is still regarded as the 'gold standard' for the diagnosis of leptomeningeal malignant disease. However, cytopathology has only a low sensitivity in detecting leptomeningeal lymphoma involvement. Modern technologies including proteochemical and immunophenotypic studies by flow cytometry, and molecular genetic analyses of CSF may increase sensitivity and specificity, therefore, facilitating the diagnosis of CNS lymphomas. This review gives an overview and discussion of the current aspects of CSF analyses in CNS lymphomas.

The mutational pattern of primary lymphoma of the central nervous system determined by whole-exome sequencing

To decipher the mutational pattern of primary CNS lymphoma (PCNSL), we performed whole-exome sequencing to a median coverage of 103 × followed by mutation verification in 9 PCNSL and validation using Sanger sequencing in 22 PCNSL. We identified a median of 202 (range: 139-251) potentially somatic single nucleotide variants (SNV) and 14 small indels (range: 7-22) with potentially protein-changing features per PCNSL. Mutations affected the B-cell receptor, toll-like receptor, and NF-κB and genes involved in chromatin structure and modifications, cell-cycle regulation, and immune recognition. A median of 22.2% (range: 20.0-24.7%) of somatic SNVs in 9 PCNSL overlaps with the RGYW motif targeted by somatic hypermutation (SHM); a median of 7.9% (range: 6.2-12.6%) affects its hotspot position suggesting a major impact of SHM on PCNSL pathogenesis. In addition to the well-known targets of aberrant SHM (aSHM) (PIM1), our data suggest new targets of aSHM (KLHL14, OSBPL10, and SUSD2). Among the four most frequently mutated genes was ODZ4 showing protein-changing mutations in 4/9 PCNSL. Together with mutations affecting CSMD2, CSMD3, and PTPRD, these findings may suggest that alterations in genes having a role in CNS development may facilitate diffuse large B-cell lymphoma manifestation in the CNS. This may point to intriguing mechanisms of CNS tropism in PCNSL.

[Differential diagnosis of lymphoid infiltrates in the central nervous system: experience of the Network Lymphomas and Lymphomatoid Lesions in the Nervous System]

The differential diagnosis of lymphoid lesions in the central nervous system covers a broad spectrum of neoplastic and inflammatory disorders. Complex cases benefit from the combined expertise in the fields of hematopoietic and neuroepithelial tumors as well as neuroimmunology. The Network Lymphomas and Lymphomatoid Lesions in the Nervous System (NLLLN) recommends performing a biopsy prior to any therapeutic intervention as a precise diagnosis was impossible in approximately 50 % of patients pretreated with corticosteroids. This is based on the analysis of approximately 1,000 cases in the past 4 years. In addition to total NLLLN experiences the characteristics, pathogenesis and differential diagnosis of primary lymphoma of the central nervous system are discussed.

LMO2 and BCL6 are associated with improved survival in primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is an aggressive sub-variant of non-Hodgkin lymphoma (NHL) with morphological similarities to diffuse large B-cell lymphoma (DLBCL). While methotrexate (MTX)-based therapies have improved patient survival, the disease remains incurable in most cases and its pathogenesis is poorly understood. We evaluated 69 cases of PCNSL for the expression of HGAL (also known as GCSAM), LMO2 and BCL6 - genes associated with DLBCL prognosis and pathobiology, and analysed their correlation to survival in 49 PCNSL patients receiving MTX-based therapy. We demonstrate that PCNSL expresses LMO2, HGAL(also known as GCSAM) and BCL6 proteins in 52%, 65% and 56% of tumours, respectively. BCL6 protein expression was associated with longer progression-free survival (P = 0·006) and overall survival (OS, P = 0·05), while expression of LMO2 protein was associated with longer OS (P = 0·027). Further research is needed to elucidate the function of BCL6 and LMO2 in PCNSL.

Systems biology of primary CNS lymphoma: from genetic aberrations to modeling in mice

Primary lymphoma of the central nervous system (CNS, PCNSL) is a specific diffuse large B cell lymphoma entity arising in and confined to the CNS. Despite extensive research since many decades, the pathogenetic mechanisms underlying the remarkable tropism of this peculiar malignant hematopoietic tumor remain still to be elucidated. In the present review, we summarize the present knowledge on the genotypic and phenotypic characteristics of the tumor cells of PCNSL, give an overview over deregulated molecular pathways in PCNSL and present recent progress in the field of preclinical modeling of PCNSL in mice. With regard to the phenotype, PCNSL cells resemble late germinal center exit IgM+IgD+ B cells with blocked terminal B cell differentiation. They show continued BCL6 activity in line with ongoing activity of the germinal center program. This together with the pathways deregulated by genetic alterations may foster B cell activation and brisk proliferation, which correlated with the simultaneous MYC and BCL2 overexpression characteristic for PCNSL. On the genetic level, PCNSL are characterized by ongoing aberrant somatic hypermutation that, besides the IG locus, targets the PAX5, TTF, MYC, and PIM1 genes. Moreover, PCNSL cells show impaired IG class switch due to sμ region deletions, and PRDM1 mutations. Several important pathways, i.e., the B cell receptor (BCR), the toll-like receptor, and the nuclear factor-κB pathway, are activated frequently due to genetic changes affecting genes like CD79B, SHIP, CBL, BLNK, CARD11, MALT1, BCL2, and MYD88. These changes likely foster tumor cell survival. Nevertheless, many of these features are also present in subsets of systemic DLBLC and might not be the only reasons for the peculiar tropism of PCNSL. Here, preclinical animal models that closely mimic the clinical course and neuropathology of human PCNSL may provide further insight and we discuss recent advances in this field. Such models enable us to understand the pathogenetic interaction between the malignant B cells, resident cell populations of the CNS, and the associated inflammatory infiltrate. Indeed, the immunophenotype of the CNS as well as tumor cell characteristics and intracerebral interactions may create a micromilieu particularly conducive to PCNSL that may foster aggressiveness of tumor cells and accelerate the fatal course of disease. Suitable animal models may also serve as a well-defined preclinical system and may provide a useful tool for developing new specific therapeutic strategies.

How I treat CNS lymphomas

The pathogenesis of primary and secondary central nervous system (CNS) lymphoma poses a unique set of diagnostic, prognostic, and therapeutic challenges. During the past 10 years, there has been significant progress in the elucidation of the molecular properties of CNS lymphomas and their microenvironment, as well as evolution in the development of novel treatment strategies. Although a CNS lymphoma diagnosis was once assumed to be uniformly associated with a dismal prognosis, it is now reasonable to anticipate long-term survival, and possibly a cure, for a significant fraction of CNS lymphoma patients. The pathogenesis of CNS lymphomas affects multiple compartments within the neuroaxis, and proper treatment of the CNS lymphoma patient requires a multidisciplinary team with expertise not only in hematology/oncology but also in neurology, neuroradiology, neurosurgery, clinical neuropsychology, ophthalmology, pathology, and radiation oncology. Given the evolving principles of management and the evidence for improvements in survival, our goal is to provide an overview of current knowledge regarding the pathogenesis of CNS lymphomas and to highlight promising strategies that we believe to be most effective in establishing diagnosis, staging, and therapeutic management.

Primary lymphoma of the central nervous system--a diagnostic challenge

Primary lymphoma of the central nervous system is a distinct diffuse large B-cell lymphoma confined to the nervous system. Whereas classical cases can be classified easily, differential diagnosis can be a challenge in particular in patients who had received treatment prior to biopsy. In the differential diagnosis, other tumours and inflammatory diseases of autoimmune and infectious aetiology need to be considered.

Mechanisms of intracerebral lymphoma growth delineated in a syngeneic mouse model of central nervous system lymphoma

Primary lymphoma of the central nervous system (PCNSL) is defined as lymphoma of the diffuse large B-cell type confined to the CNS. To understand the effects of the CNS microenvironment on the malignant B cells and their interactions with the cells of the target organ, we analyzed a syngeneic mouse model. Transplantation of BAL17 cells into the frontal white matter of syngeneic BALB/c mice induced lymphomas with major clinical and neuropathologic features that parallel those of human PCNSL, including an angiocentric growth pattern in the brain parenchyma and tropism for the inner and outer ventricular system. Seven cycles of repeated isolation of lymphoma cells from the CNS and their intracerebral reimplantation induced genotypic and phenotypic alterations in resulting BAL17VII cells; the affected genes regulate apoptosis and are of the JAK/STAT pathway. Because lymphoma growth of BAL17VII cells was significantly accelerated, that is, shortening the time to death of the mice, these data indicate that prolonged stay of the lymphoma cells in the CNS was associated with worse outcome. These findings suggest that the CNS microenvironment fosters aggressiveness of lymphoma cells, thereby accelerating the lethal course of PCNSL.

Biased immunoglobulin light chain use in the Chlamydophila psittaci negative ocular adnexal marginal zone lymphomas

Ocular adnexal mucosa associated lymphoid tissue lymphomas (OAMALTL) are the most common lymphomas of the eye. The potential roles for specific antigens in these lymphomas are still controversial. Previously we examined IGHV usage and mutations in Chlamydophila (C) psittaci-negative OAMALTL, demonstrating biased use of the IGHV4 family and IGHV4-34 gene and evidence for antigen selection. Herein, we examined the IGKV/IGLV gene usage and mutations in 34 C. psittaci-negative OAMALTL originating from the orbit (15), conjunctivae (14), and lacrimal gland (5). Clonal potentially functional IGKV/IGLV gene sequences were identified in 30 tumors (18 kappa and 12 lambda). An overrepresentation of the IGKV4 family (P < 0.01) was observed. The IGKV3-20*01 allele was used at a greater frequency than in normal peripheral blood B-lymphocytes (P = 0.02) and commonly paired with the IGHV4-34 allele. Twenty-seven of the 30 unique light chain sequences displayed mutations from germline and evidence for antigen selection. Overall our findings demonstrate that in C. psittaci-negative OAMALTL there is a biased usage of IGKV families and genes, which harbor somatic mutations. These findings and the specific paring between the IGKV3-20*01 and IGHV4-34 alleles suggest that specific antigens could play an important role in the pathogenesis of these lymphomas.

Intensive chemotherapy and immunotherapy in patients with newly diagnosed primary CNS lymphoma: CALGB 50202 (Alliance 50202)

PURPOSE

Concerns regarding neurocognitive toxicity of whole-brain radiotherapy (WBRT) have motivated development of alternative, dose-intensive chemotherapeutic strategies as consolidation in primary CNS lymphoma (PCNSL). We performed a multicenter study of high-dose consolidation, without WBRT, in PCNSL. Objectives were to determine: one, rate of complete response (CR) after remission induction therapy with methotrexate, temozolomide, and rituximab (MT-R); two, feasibility of a two-step approach using high-dose consolidation with etoposide plus cytarabine (EA); three, progression-free survival (PFS); and four, correlation between clinical and molecular prognostic factors and outcome.

PATIENTS AND METHODS

Forty-four patients with newly diagnosed PCNSL were treated with induction MT-R, and patients who achieved CR received EA consolidation. We performed a prospective analysis of molecular prognostic biomarkers in PCNSL in the setting of a clinical trial.

RESULTS

The rate of CR to MT-R was 66%. The overall 2-year PFS was 0.57, with median follow-up of 4.9 years. The 2-year time to progression was 0.59, and for patients who completed consolidation, it was 0.77. Patients age > 60 years did as well as younger patients, and the most significant clinical prognostic variable was treatment delay. High BCL6 expression correlated with shorter survival.

CONCLUSION

CALGB 50202 demonstrates for the first time to our knowledge that dose-intensive consolidation for PCNSL is feasible in the multicenter setting and yields rates of PFS and OS at least comparable to those of regimens involving WBRT. On the basis of these encouraging results, an intergroup study has been activated comparing EA consolidation with myeloablative chemotherapy in this randomized trial in PCNSL, in which neither arm involves WBRT.