Search Results (11)

The bi- or multinucleated Reed–Sternberg cell (RS) is the diagnostic cornerstone of Epstein–Barr Virus (EBV)-positive and EBV-negative classical Hodgkin lymphoma (cHL). cHL is a germinal center (GC)-derived B-cell disease. Hodgkin cells (H) are the mononuclear precursors of RS. An experimental model has to fulfill three conditions to qualify as common pathogenic denominator: (i) to be of GC-derived B-cell origin, (ii) to be EBV-negative to avoid EBV latency III expression and (iii) to support permanent EBV-encoded oncogenic latent membrane protein (LMP1) expression upon induction. These conditions are unified in the EBV-, diffuse large B-Cell lymphoma (DLBCL) cell line BJAB-tTA-LMP1. 3D reconstructive nanotechnology revealed spatial, quantitative and qualitative disturbance of telomere/shelterin interactions in mononuclear H-like cells, with further progression during transition to RS-like cells, including progressive complexity of the karyotype with every mitotic cycle, due to BBF (breakage/bridge/fusion) events. The findings of this model were confirmed in diagnostic patient samples and correlate with clinical outcomes. Moreover, in vitro, significant disturbance of the lamin AC/telomere interaction progressively occurred. In summary, our research over the past three decades identified cHL as the first lymphoid malignancy driven by a disturbed telomere/shelterin/lamin AC interaction, generating the diagnostic RS. Our findings may act as trailblazer for tailored therapies in refractory cHL. Full article

BOB1, a mammalian lymphocyte-specific transcriptional coactivator of the transcription factors OCT1 and OCT2 (OCT1/2), plays important roles in normal immune responses, autoimmunity, and hematologic malignancies. The issue of a DNA sequence preference change imposed by BOB1 was raised more than two decades ago but remains unresolved. In this paper, using the EMSA–SELEX–Seq approach, we have reassessed the intrinsic ability of BOB1 to modulate the specificity of DNA recognition by OCT1 and OCT2. Our results have reaffirmed previous conclusions regarding BOB1 selectivity towards the dimer configuration of OCT1/2. However, they suggest that the monomeric configuration of these factors, assembled on the classical octamer ATGCAAAT and related motifs, are the primary targets of BOB1. Our data further specify the DNA sequence preference imposed by BOB1 and predict the probability of ternary complex formation. These results provide an additional insight into the action of BOB1—an essential immune regulator and a promising molecular target for the treatment of autoimmune diseases and hematologic malignancies. Full article

CD30-positive germinal center (GC)-derived B cell lymphomas are frequently linked to Epstein–Barr Virus (EBV) infection. However, a suitable animal model for the investigation of the interplay between γ-herpesvirus and host cells in B cell pathogenesis is currently lacking. Here, we present a novel in vivo model enabling the analysis of genetically modified viruses in combination with genetically modified GC B cells. As a murine γ-herpesvirus, we used MHV-68 closely mirroring the biology of EBV. Our key finding was that Cre-mediated recombination can be successfully induced by an MHV-68 infection in GC B cells from Cγ1-Cre mice allowing for deletion or activation of loxP-flanked cellular genes. The implementation of PrimeFlow RNA assay for MHV-68 demonstrated the enrichment of MHV-68 in GC and isotype-switched B cells. As illustrations of virus and cellular modifications, we inserted the EBV gene LMP2A into the MHV-68 genome and induced constitutively active CD30-signaling in GC B cells through MHV-68 infections, respectively. While the LMP2A-expressing MHV-68 behaved similarly to wildtype MHV-68, virally induced constitutively active CD30-signaling in GC B cells led to the expansion of a pre-plasmablastic population. The findings underscore the potential of our novel tools to address crucial questions about the interaction between herpesviral infections and deregulated cellular gene-expression in future studies. Full article

Kaposi’s sarcoma-associated herpesvirus (KSHV) is associated with vascular endothelial cell tumor, Kaposi’s sarcoma (KS) and lymphoproliferative disorder, multicentric Castleman’s disease (MCD), primary effusion lymphoma (PEL) and KSHV inflammatory cytokine syndrome (KICS). Dysregulation of proinflammatory cytokines is found in most KSHV associated diseases. However, little is known about the role of host microenvironment in the regulation of KSHV establishment in B cells. In the present study, we demonstrated that IFN-γ has a strong inhibitory effect on KSHV infection but only in a subset of tonsil-derived lymphocyte samples that are intrinsically more susceptible to infection, contain higher proportions of naïve B cells, and display increased levels of IRF1 and STAT1-pY701. The effect of IFN-γ in responsive samples was associated with increased frequencies of germinal center B cells (GCB) and decreased infection of plasma cells, suggesting that IFN-γ-mediated modulation of viral dynamics in GC can inhibit the establishment of KSHV infection. Full article

Follicular lymphoma (FL), a generally indolent disease that derives from germinal center (GC) B cells, represents around 20–25% of all new lymphomas diagnosed in Western countries. The characteristic t(14;18)(q32;q21) translocation that places the BCL2 oncogene under control of the immunoglobulin heavy-chain enhancer occurs in pro- or pre-B cells. However, additional secondary alterations are required for the development of overt FL, which mainly affects genes involved in epigenetic and transcriptional regulation, signaling and B cell differentiation, the BCR/NF-κB pathway, and proliferation/apoptosis. On the other hand, new insights into the FL pathogenesis suggest that FL lacking the BCL2 translocation might be a distinct biological entity with genomic features different from the classical FL. Although FL is considered an indolent disease, around 10–20% of cases eventually transform to an aggressive lymphoma, usually a diffuse large B cell lymphoma, generally by a divergent evolution process from a common altered precursor cell acquiring genomic alterations involved in the cell cycle and DNA damage responses. Importantly, FL tumor cells require interaction with the microenvironment, which sustains cell survival and proliferation. Although the use of rituximab has improved the outlook of most FL patients, further genomic studies are needed to identify those of high risk who can benefit from innovative therapies. This review provides an updated synopsis of FL, including the molecular and cellular pathogenesis, key events of transformation, and targeted treatments. Full article

Chemokine receptors and their ligands have been identified as playing an important role in the development of diffuse large B-cell lymphoma (DLBCL), follicular lymphoma, and Richter syndrome (RS). Our aim was to investigate the different expression profiles in de novo DLBCL, transformed follicular lymphoma (tFL), and RS. Here, we profiled the mRNA expression levels of 18 chemokine receptors (CCR1–CCR9, CXCR1–CXCR7, CX3CR1 and XCR1) using RQ-PCR, as well as immunohistochemistry of seven chemokine receptors (CCR1, CCR4–CCR8 and CXCR2) in RS, de novo DLBCL, and tFL biopsy-derived tissues. Tonsil-derived germinal center B-cells (GC-B) served as non-neoplastic controls. The chemokine receptor expression profiles of de novo DLBCL and tFL substantially differed from those of GC-B, with at least 5-fold higher expression of 15 out of the 18 investigated chemokine receptors (CCR1–CCR9, CXCR1, CXCR2, CXCR6, CXCR7, CX3CR1 and XCR1) in these lymphoma subtypes. Interestingly, the de novo DLBCL and tFL exhibited at least 22-fold higher expression of CCR1, CCR5, CCR8, and CXCR6 compared with RS, whereas no significant difference in chemokine receptor expression profile was detected when comparing de novo DLBCL with tFL. Furthermore, in de novo DLBCL and tFLs, a high expression of CCR7 was associated with a poor overall survival in our study cohort, as well as in an independent patient cohort. Our data indicate that the chemokine receptor expression profile of RS differs substantially from that of de novo DLBCL and tFL. Thus, these multiple dysregulated chemokine receptors could represent novel clinical markers as diagnostic and prognostic tools. Moreover, this study highlights the relevance of chemokine signaling crosstalk in the tumor microenvironment of aggressive lymphomas. Full article

Classification of lymphoid neoplasms is based mainly on histologic, immunologic, and (rarer) genetic features. It has been supplemented by gene expression profiling (GEP) in the last decade. Despite the considerable success, particularly in associating lymphoma subtypes with specific transcriptional programs and classifier signatures of up- or downregulated genes, competing molecular classifiers were often proposed in the literature by different groups for the same classification tasks to distinguish, e.g., BL versus DLBCL or different DLBCL subtypes. Moreover, rarer sub-entities such as MYC and BCL2 “double hit lymphomas” (DHL), IRF4-rearranged large cell lymphoma (IRF4-LCL), and Burkitt-like lymphomas with 11q aberration pattern (mnBLL-11q) attracted interest while their relatedness regarding the major classes is still unclear in many respects. We explored the transcriptional landscape of 873 lymphomas referring to a wide spectrum of subtypes by applying self-organizing maps (SOM) machine learning. The landscape reveals a continuum of transcriptional states activated in the different subtypes without clear-cut borderlines between them and preventing their unambiguous classification. These states show striking parallels with single cell gene expression of the active germinal center (GC), which is characterized by the cyclic progression of B-cells. The expression patterns along the GC trajectory are discriminative for distinguishing different lymphoma subtypes. We show that the rare subtypes take intermediate positions between BL, DLBCL, and FL as considered by the 5th edition of the WHO classification of haemato-lymphoid tumors in 2022. Classifier gene signatures extracted from these states as modules of coregulated genes are competitive with literature classifiers. They provide functional-defined classifiers with the option of consenting redundant classifiers from the literature. We discuss alternative classification schemes of different granularity and functional impact as possible avenues toward personalization and improved diagnostics of GC-derived lymphomas. Full article

Besides a recognized role of PD-1/PD-L1 checkpoint in anti-tumour immune evasion, there is accumulating evidence that PD-1/PD-L1 interactions between B and T cells also play an important role in normal germinal center (GC) reactions. Even when smaller in number, T follicular helper cells (T_FH) and regulatory T (T_FR) or B (Breg) cells are involved in positive selection of GC B cells and may result critical in the lymphoma microenvironment. Here, we discuss a role of PD-1/PD-L1 during tumour evolution in diffuse large B cell lymphoma (DLBCL), a paradigm of GC-derived lymphomagenesis. We depict a progression model, in two phases, where malignant B cells take advantage of positive selection signals derived from correct antigen-presentation and PD-1/PD-L1 inter-cellular crosstalks to survive and initiate tumour expansion. Later, a constant pressure for the accumulation of genetic/epigenetic alterations facilitates that DLBCL cells exhibit higher PD-L1 levels and capacity to secrete IL-10, resembling Breg-like features. As a result, a complex immunosuppressive microenvironment is established where DLBCL cells sustain proliferation and survival by impairing regulatory control of T_FR cells and limiting IL-21-mediated anti-tumour functions of T_FH cells and maximize the use of PD-1/PD-L1 signaling to escape from CD8⁺ cytotoxic activity. Integration of these molecular and cellular addictions into a framework may contribute to the better understanding of the lymphoma microenvironment and contribute to the rationale for novel PD-1/PD-L1-based combinational immunotherapies in DLBCL. Full article

Follicular lymphoma (FL), the most frequent indolent non-Hodgkin’s B cell lymphoma, is considered as a prototypical centrocyte-derived lymphoma, dependent on a specific microenvironment mimicking the normal germinal center (GC). In agreement, several FL genetic alterations affect the crosstalk between malignant B cells and surrounding cells, including stromal cells and follicular helper T cells (Tfh). In our study, we sought to deconvolute this complex FL supportive synapse by comparing the transcriptomic profiles of GC B cells, Tfh, and stromal cells, isolated from normal versus FL tissues, in order to identify tumor-specific pathways. In particular, we highlighted a high expression of IL-6 and IL-7 in FL B cells that could favor the activation of FL Tfh overexpressing IFNG, able in turn to stimulate FL B cells without triggering MHC (major histocompatibility) class II expression. Moreover, the glycoprotein clusterin was found up-regulated in FL stromal cells and could promote FL B cell adhesion. Finally, besides its expression on Tfh, CD200 was found overexpressed on tumor B cells and could contribute to the induction of the immunosuppressive enzyme indoleamine-2,3 dioxygenase by CD200R-expressing dendritic cells. Altogether our findings led us to outline the contribution of major signals provided by the FL microenvironment and their interactions with malignant FL B cells. Full article

Germinal centers (GCs) are specialized compartments within the secondary lymphoid organs where B cells proliferate, differentiate, and mutate their antibody genes in response to the presence of foreign antigens. Through the GC lifespan, interclonal competition between B cells leads to increased affinity of the B cell receptors for antigens accompanied by a loss of clonal diversity, although the mechanisms underlying clonal dynamics are not completely understood. We present here a multi-scale quantitative model of the GC reaction that integrates an intracellular component, accounting for the genetic events that shape B cell differentiation, and an extracellular stochastic component, which accounts for the random cellular interactions within the GC. In addition, B cell receptors are represented as sequences of nucleotides that mature and diversify through somatic hypermutations. We exploit extensive experimental characterizations of the GC dynamics to parameterize our model, and visualize affinity maturation by means of evolutionary phylogenetic trees. Our explicit modeling of B cell maturation enables us to characterise the evolutionary processes and competition at the heart of the GC dynamics, and explains the emergence of clonal dominance as a result of initially small stochastic advantages in the affinity to antigen. Interestingly, a subset of the GC undergoes massive expansion of higher-affinity B cell variants (clonal bursts), leading to a loss of clonal diversity at a significantly faster rate than in GCs that do not exhibit clonal dominance. Our work contributes towards an in silico vaccine design, and has implications for the better understanding of the mechanisms underlying autoimmune disease and GC-derived lymphomas. Full article

In Argentina, Epstein-Barr virus (EBV) presence is associated with Hodgkin lymphoma (HL) in patients younger than 10 years, suggesting a relationship between low age of EBV infection and HL. Given that HL is derived from germinal centers (GC), our aim was to compare EBV protein expression and microenvironment markers between pediatric HL patients and EBV+GC in children. Methods: EBV presence and immune cell markers were assessed by in situ hybridization and immunohistochemistry (IHC). Results: Viral latency II pattern was proved in all HL patients and in 81.8% of EBV+ tonsillar GCs. LMP1 and LMP2 co-expression were proved in 45.7% HL cases, but only in 7.7% EBV+ GC in pediatric tonsils. An increase in CD4+, IL10, and CD68+ cells was observed in EBV+ GC. In pediatric HL patients, only the mean of IL10+ cells was statistically higher in EBV+ HL. Conclusions: Our findings point us out to suggest that LMP1 expression may be sufficient to drive neoplastic transformation, that an immune regulatory milieu counteracts cytotoxic environment in EBV-associated Hodgkin lymphoma, and that CD4+ and CD68+ cells may be recruited to act in a local collaborative way to restrict, at least in part, viral-mediated lymphomagenesis in tonsillar GC. Full article