Pathogenesis Of Diffuse Large B-cell Lymphoma Research Articles

Understanding the intrinsic biology of diffuse large B-cell lymphoma: recent advances and future prospects.

Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphoid tumor, and accounts for approximately 30-40% of non-Hodgkin lymphomas. Although the prognosis has significantly improved with the advent of rituximab combination chemotherapy in the early 2000s, recurrence still occurs in about 40% of cases. Even though chemotherapy with increased dose-intensity is used in recurrent cases, the prognosis of such patients remains poor. Thus, the development of personalized medicine, including molecular-targeted drugs, is required to improve the prognosis of DLBCL patients, and further understanding of the molecular pathogenesis of DLBCL is essential for this purpose. With recent advances in genetic analysis technology, unknown genetic abnormalities and gene expression patterns have been discovered, and based on these discoveries, progress is being made in elucidating and subdividing molecular pathologies. This article summarizes recent findings regarding molecular pathogenesis in DLBCL using transcriptome and genomics technologies, and outlines the path to personalized medicine.

Abstract P04: Role of glucocorticoid receptor in normal and malignant germinal center B cells

Abstract We have reported that super-enhancers (SEs) are specifically hypermutated by Activation-Induced Deaminase (AID)-induced Aberrant Somatic Hypermutation in >90% of diffuse large B cell lymphoma (DLBCL) cases (Bal et al. Nature 2022). Analysis of 122 primary DLBCL biopsies and cell lines identified more than 80 SEs that are recurrently hypermutated, with an average of 12 hypermutated SE/case. Hypermutated SEs are predominantly linked to genes encoding regulators of B cell development and well-known lymphoma oncogenes, including BCL6, BCL2 and CXCR4. We showed that specific hotspot mutations prevent binding and transcriptional downregulation by transcriptional repressors leading to target gene dysregulation. Among these, hypermutation of the SEs linked to BCL2 and CXCR4 abrogates the binding of the glucocorticoid receptor (GR)/transcription factor encoded by NR3C1. As a result, BCL2 and CXCR4 escape GR-mediated transcriptional repression leading to their de-regulated expression in germinal center (GC) B cells. Together with the observation that the NR3C1 gene is genetically inactivated in a small fraction of DLBCL, and the relevance of glucocorticoid-based therapy in DLBCL, these results prompted a comprehensive analysis of the role of GR in normal and malignant B cells. We report that GR is detectable in the nucleus of the great majority of GC B cells, suggesting that it is active as a transcription factor. Similarly, DLBCL primary cases (including GCB-, ABC- and unclassified DLBCL) display GR nuclear expression. Analysis of a conditional GC-specific Nr3c1 knock-out (KO) mouse model showed that GC B cells form normally in the absence of Nr3c1. However, the transcriptional profile of Nr3c1-KO GC B cells was significantly altered compared to wild-type cells. By integrating the GR binding profile obtained in normal human GC B cells with the transcripts differentially expressed in Nr3c1-KO GC B cells, we identified a set of about 2,000 genes that are directly modulated by GR during the GC reaction. Pathway enrichment analysis showed that GR controls several signaling pathways, suggesting a modulatory role on the BCR and CXCR4 pathways. In addition, GR targets display a significant overlap with the BCL6 transcriptional network, suggesting a cooperative role in GC B cell development. Notably, GR was shown to regulate pathways involved in plasma cell differentiation, while repressing targets associated with memory B cell development. In DLBCL cases, several NR3C1 binding sites are recurrently targeted by mutations, suggesting that genetic impairment of GR activity is heterogeneous and extends beyond CXCR4 and BCL2. Together, these data support a role for the glucocorticoid pathway in GC physiology. Recurrent inactivation of the NR3C1 gene or part of its transcriptional regulatory program may contribute to DLBCL pathogenesis, with implications for presently unknown specific roles of glucocorticoids in the therapeutic regimens for DLBCL. Citation Format: Clarissa Corinaldesi, Antony B Holmes, Elodie Bal, Laura Pasqualucci, Katia Basso, Riccardo Dalla-Favera. Role of glucocorticoid receptor in normal and malignant germinal center B cells [abstract]. In: Proceedings of the Blood Cancer Discovery Symposium; 2024 Mar 4-6; Boston, MA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(2_Suppl):Abstract nr P04.

Still Far to Go With Characterisation of Molecular and Genetic Features of Diffuse Large B-Cell Lymphoma in People Living With HIV: A Scoping Review.

Diffuse large B-cell lymphoma (DLBCL) accounts for half of non-Hodgkin lymphoma cases in people living with human immunodeficiency syndrome (PLWH). The interplay of viremia, immune dysregulation and co-infection with oncogenic viruses play a role in pathogenesis of DLBCL in PLWH (HIV-DLBCL). This scoping review aimed to describe the molecular landscape of HIV-DLBCL, investigate the impact of biomarker on clinical outcomes and describe technologies used to characterise HIV-DLBCL. Thirty-two papers published between 2001 and 2023 were included in this review. Samples of HIV-DLBCL were relatively small (16-110). Cohort effects influenced frequencies of molecular characteristics hence their impact on survival was not clear. Molecular features were distinct from HIV-unrelated DLBCL. The most frequently assessed characteristic was cell of origin (81.3% of studies). Somatic mutations were the least researched (6.3% of studies). Overall, biomarker identification in HIV-DLBCL requires broader richer data from larger or pooled samples using more powerful techniques such as next-generation sequencing.

Abstract C053: Multi-omics guided design of lymphoid organoids to study cooperative cell signaling in lymphomas

Abstract Our collaborative research (Cell1) used 1001 patients of diffuse large B-cell lymphoma (DLBCL) to show that genetic alterations interact with clinical factors to impact overall survival (OS) in DLBCL. B cell receptor (BCR) signaling-driven activated B cell-like (ABC) DLBCL subtypes is the most chemo-resistant subtype to the frontline therapy R-CHOP, with 40% of patients experiencing no response or relapse. We have systematically examined disparities in lymphoma outcomes and identified African-American (AA) patients as a poor-risk population in DLBCL, with a diagnosis age 10 years younger than other racial groups. We found that AA-DLBCL patients experienced inferior 5-year OS compared to non-Hispanic whites (38% vs 46%)2,3. We performed the first-ever characterization of genetic alterations among AA-DLBCL patients and demonstrated distinct mutation patterns across DLBCL arising in AA ancestry groups4. While some of the most frequent genetic mutations in AA-DLBCL are related to chromatin and epigenetics, few studies have investigated racial disparities in patients with aggressive ABC DLBCLs. The mechanisms that determine this racial inequality are unknown but may lie in the particular spectrum of mutations that act in concert with intricate survival signals imparted by the lymph node tumor microenvironment (Ly-TME). The pathogenesis of ABC DLBCLs has been linked to constitutive activation of and cooperation between the BCR and Toll-like receptor (TLR) pathways. These pathways are emerging as novel therapeutic targets, with a particular interest in MALT1 (mucosa-associated lymphoid tissue translocation protein 1). However, the genetic heterogeneity of ABC DLBCLs and the cooperative signaling mediated by the Ly-TME have led to discrepancies in drug responses. As a first step towards understanding Ly-TME in DLBCLs (Nature Materials5), we used DLBCL patient samples from multiple cohorts, covering >1100 samples and imaging analysis to determine immune and ECM cues in the lymphoid TME. These samples were not classified into racial categories. We designed a biomaterials-based modular lymphoma organoid that presents specific integrin ligands at controlled densities to DLBCLs. Human ABC-DLBCLs responded to MALT1 inhibition in an integrin-ligand-dependent manner. TLR activation with TLR agonists rescued cells from MALT1 inhibitors, possibly due to increased MALT1 expression. The inclusion of T-cell signals increased MALT1 expression and rescued cells from MALT1 inhibitor-mediated killing in cell lines and human PDX organoids. Changes in RNA-seq and phosphorylation in the TLR & BCR pathways were used to inform effective combination therapy approaches with MALT1 inhibitors in vitro and in vivo5. Ongoing work is determining the racial disparities in AA lymphomas through complex interactions between Ly-TME and DLBCLs.

Lymphoma-Derived IL-10 Is a Key Immunomodulatory Factor at the Tumor Microenvironment of Activated B-Cell Diffuse Large B-Cell Lymphoma and Influences In Vivo Responses to Immunotherapy

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of aggressive non-Hodgkin's lymphoma with ~40% of patients experiencing refractory or relapsed disease to R-CHOP immunochemotherapy. These higher risk patients often exhibit gene expression profiles that resemble a late germinal center-derived activated B-cell (ABC) phenotype, where diverse specific mutations in genes along BCR and TLR signaling pathways converge into constitutive activation of the NF-κB pathway. Identification of factors that contribute to the survival of malignant ABC-DLBCL cells is crucial for designing specific interventions. In this setting, previous in vitro studies in DLBCL cell lines have evidenced that IL-10 is a direct target of NF-κB signaling that sustains lymphoma cell survival by an auto-stimulatory loop via STAT3 signaling. However, the action of IL-10 could be more complex within the lymphoma microenvironment, as IL-10 can have both stimulatory and inhibitory effects depending on the cellular source of IL-10, the timing of its secretion, and the type of immune cells that receives signals via IL-10 receptor (IL-10R). To explore in vivo the relevance of lymphoma-derived IL-10, we have generated a novel quintuple transgenic mouse model that we call pBIC10, after crossing our previous ABC-DLBCL-like pBIC mice carrying constitutive NF-κB signaling (Pascual et al., Blood 2019) to mice with a floxed Il10 gene for conditional knock-out of IL-10 specifically in malignant ABC-DLBCL cells. As expected, increased intracellular IL-10 signaling was detected in primary murine DLBCL cells from pBIC mice but not in IL-10 deficient pBIC10 mice, which promoted lymphoma cell survival ex vivo as revealed by perturbation studies of the IL-10/JAK1/STAT3 autocrine loop with blocking monoclonal antibodies or selected inhibitors. However, in vivo genetic deletion of lymphoma-derived IL-10 did not offer improved overall survival but, on the contrary, notably accelerated DLBCL progression in pBIC10 mice (Figure 1A, left). A comprehensive integration of multiparametric flow cytometry and transcriptomic analyses using bulk and single-cell RNA-seq of lymphoma cells and the tumor microenvironment coupled with BCR- and TCR-seq, identified lymphoma-derived IL-10 as a key immunomodulator of the DLBCL microenvironment, including unexpected protective paracrine functions in the progression of DLBCL. By comparing IL-10-proficient (pBIC) and -deficient (pBIC10) murine DLBCL models, we observed a multifaceted role of IL-10 produced by DLBCL cells, enabling immune-effector processes (facilitating immune chemotaxis, antigen presentation, and IFNγ responses) that yielded higher percentages of long-lived stem-like CD8 +TCF-1 +PD-1 lo/int T cells and dendritic cells, while restraining PD-1/LAG3-driven T-cell exhaustion and reducing immunosuppression by CD4 +CD25 +FOXP3 + regulatory T (Treg) cells. Thus, depletion of lymphoma-derived IL-10 decreased T-cell cytotoxicity and increased Treg-driven immunosuppression, which collectively accelerated lymphoma development. Consequently, T-cell targeted immune-checkpoint therapy (with anti-PD-1 antibodies) was effective only in IL-10-proficient DLBCL but not in IL-10-deficient pBIC10 mice (Figure 1A, right). Further comparative studies between pBIC and pBIC10 mice showed that tumor vascularization and expression of B-cell calcium channels, which have been previously associated with sensitivity to rituximab, were counteracted by lymphoma-derived IL-10. Accordingly, anti-CD20-based targeting of lymphoma cells (with rituximab surrogate antibodies) showed best in vivo responses in IL-10-deficient DLBCL mice with respect to pBIC mice (Figure 1A, right). Consistent with this preclinical data, analyses of transcriptional IL-10-associated hallmarks to stratify DLBCL patients (Schmitz et al., NEJM 2018) identified better clinical responses to R-CHOP in patients with pBIC10-like DLBCL phenotype (Figure 1B). Collectively, our study provides new functional and mechanistic insights into the role of lymphoma-derived IL-10 in the pathogenesis of DLBCL and the restraint of an immunosuppressed tumor microenvironment, which holds predictive potential as a biomarker for immunotherapy responses in DLBCL.

Molecular complexity of diffuse large B-cell lymphoma: a molecular perspective and therapeutic implications.

Diffuse large B-cell lymphoma (DLBCL) stands as a formidable challenge in the landscape of non-Hodgkin's lymphomas. This review illuminates the remarkable strides made in comprehending DLBCL's molecular intricacies and devising targeted treatments. DLBCL, the most prevalent non-Hodgkin's lymphoma, has seen transformative progress in its characterization. Genetic investigations, led by high-throughput sequencing, have unveiled recurrent mutations in genes such as MYC, BCL2, and BCL6, casting light on the underlying genetic chaos propelling DLBCL's aggressiveness. A pivotal facet of this understanding centers on cell signaling pathways. Dysregulation of B-cell receptor (BCR) signaling, NF-κB, PI3K/Akt/mTOR, JAK/STAT, Wnt/β-Catenin, and Toll-like receptor pathways plays a critical role in DLBCL pathogenesis, offering potential therapeutic targets. DLBCL's complex tumor microenvironment (TME) cannot be overlooked. The dynamic interplay among tumor cells, immune cells, stromal components, and the extracellular matrix profoundly influences DLBCL's course and response to therapies. Epigenetic modifications, including DNA methylation and histone changes, add another layer of intricacy. Aberrant epigenetic regulation plays a significant role in lymphomagenesis, offering prospects for epigenetic-based therapies. Promisingly, these molecular insights have spurred the development of personalized treatments. Targeted therapies and immunotherapies, guided by genomic profiling and molecular classification, are emerging as game-changers in DLBCL management. In conclusion, this review underscores the remarkable strides in understanding DLBCL's molecular underpinnings, spanning genetics, cell signaling, the tumor microenvironment, and epigenetics. These advances pave the way for more effective, personalized treatments, renewing hope for DLBCL patients.

Copanlisib in Combination with Nivolumab in Subjects with Relapsed/Refractory Diffuse Large B-Cell Lymphoma and Primary Mediastinal Large B-Cell Lymphoma: A Phase II Study

Introduction: Diffuse Large B-cell Lymphoma (DLBCL) are aggressive B-cell non-Hodgkin lymphomas (NHL). One particular subtype, Primary Mediastinal B-cell Lymphoma (PMBCL), is often grouped with DLBCL, but it possesses distinct biological and clinical characteristics. While initial therapy successfully cures approximately two-thirds of patients (pts), those who do not respond or experience progression within the first two years have a poor prognosis despite novel cellular therapies and bispecifics and ultimately succumb to their disease. There is a pressing need for more effective therapeutic approaches in this patient population. Recent advances in the understanding of DLBCL pathogenesis have led to the targeting of various signaling pathways, including the PI3K-AKT-mTOR pathway. One such drug, copanlisib (C), a pan-PI3K inhibitor with potent PI3K-α/PI3K-δ inhibition, exhibited activity in both indolent and aggressive NHL. In preclinical studies using a DLBCL mouse model, treatment with C effectively reduced the immunosuppressive tumor-infiltrating T-regulatory cells (Tregs). Moreover, when combined with a surrogate anti-mouse programmed death -1 (PD-1) blocker, C demonstrated significant in vivo responses (75%) compared to the monotherapy groups (0%). These findings support the rationale for exploring the combination of nivolumab, a PD-1 blocker, and copanlisib (C-N) in DLBCL. Thus, a phase 2 prospective study has been developed, focusing on two relapsed/refractory (RR) cohorts (DLBCL and PMBCL), treated with the combination of C-N. A prespecified interim analysis was planned upon enrollment of 14 pts. Herein, we report outcomes of the 12 enrolled pts, as the study was halted prematurely due to a safety signal deemed possibly related to the combination. Study design: C 60 mg was given intravenously on days 1, 8, and 15 during cycles 1-8, and on days 1 and 15 in subsequent cycles. N 240 mg IV was given on days 1 and 15 during cycles 1-8, and 480 mg on day 1 on subsequent cycles. Each treatment cycle is 28 days. Therapy was given for up to 2 years, as long as there is no disease progression or unacceptable side effects. The primary objective of the study is to determine the ORR, which includes complete and partial responses (CR+PR). Secondary objectives include evaluating the safety of the combination, as well as assessing progression-free survival (PFS), duration of response (DOR), CR, and overall survival (OS). The study plan was to enroll a maximum of 106 pts, including a safety cohort of 6 pts. The study received funding from Bayer and conducted through NCI-CTEP (NCI Protocol #10193; NCT03484819). Results: Twelve pts who received at least one cycle of C-N were included in this analysis. Pt characteristics are illustrated in table 1. All enrolled pts had DLBCL histology. Only one patient received a prior autologous stem cell transplant. Interestingly 4/12 received prior chimeric antigen receptor T-cell therapy (CART). Of the 12 enrolled pts, seven were evaluated for response. The ORR was 25% (3/12) (95% CI: 5 - 57%), all CR. The median number of cycles received was 2.5 (range 1-24) with two pts receiving 23 and 24 cycles. Observed grade 3 and higher adverse events (AEs) were as follows: non-hematologic AEs in 10/12 (83.3%), while hematologic AEs were seen in 5/12 (41.7%) pts. A relatively higher incidence of cardiac events (4/12) were noted including one cardiac arrest after one cycle of therapy, and four atrial fibrillation events, all grade 3, but only two were deemed possibly attributed to therapy. The cardiac arrest was deemed unrelated to therapy. Conclusions: C-N combination had modest clinical activity in pts with R/R DLBCL with some prolonged responses. However, due to the relatively high number of cardiac events and the changing therapeutic landscape with recent approvals, a decision was made to halt the study. These findings likely reflect possibly older and sicker patient population. Biomarker studies for predictors of response are under consideration.

Leukemic presentation and progressive genomic alterations of MCD/C5 diffuse large B-cell lymphoma (DLBCL).

Diffuse large B-cell lymphoma (DLBCL) is a heterogenous group of lymphoid malignancies. Based on gene expression profiling, it has been subdivided into germinal center (GC)-derived and activated B-cell (ABC) types. Advances in molecular methodologies have further refined the subclassification of DLBCL, based on recurrent genetic abnormalities. Here, we describe a distinct case of DLBCL that presented in leukemic form. DNA sequencing targeting 275 genes revealed pathogenically relevant mutations of CD79B, MyD88, TP53, TBL1XR1, and PIM1 genes, indicating that this lymphoma would be best classified as MCD/C5 DLBCL, an ABC subtype. Despite an initial good clinical response to BTK inhibitor ibrutinib, anti-CD20 antibody rituxan, alkylating agent bendamustine, and hematopoietic stem-cell transplant, the lymphoma relapsed, accompanied by morphologic and molecular evidence of disease progression. Specifically, the recurrent tumor developed loss of TP53 heterozygosity (LOH) and additional chromosomal changes central to ABC DLBCL pathogenesis, such as PRDM1 loss. Acquired resistance to ibrutinib and rituxan was indicated by the emergence of BTK and FOXO1 mutations, respectively, as well as apparent activation of alternative cell-activation pathways, through copy-number alterations (CNAs), detected by high-resolution chromosomal microarrays. In vitro, studies of relapsed lymphoma cells confirmed resistance to standard BTK inhibitors but sensitivity to vecabrutinib, a noncovalent inhibitor active against both wild-type as well as mutated BTK. In summary, we provide in-depth molecular characterization of a de novo leukemic DLBCL and discuss mechanisms that may have contributed to the lymphoma establishment, progression, and development of drug resistance.

Efficacy and safety of zanubrutinib plus R-CHOP in treatment of non-GCB DLBCL with extranodal involvement.

Treatment with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) shows poor response rates in non-germinal center B cell-like (non-GCB) diffuse large B-cell lymphoma (DLBCL) patients with multiple extranodal involvement. This study aims to evaluate anti-tumor activity and safety of zanubrutinib with R-CHOP (ZR-CHOP) in treatment naïve non-GCB DLBCL with extranodal involvement. In this single-arm, phase 2, prospective, single-center study, patients with newly diagnosed non-GCB DLBCL with extranodal involvement enrolled between October 2020 to March 2022 received ZR-CHOP for 6 cycles followed by 2 cycles of maintenance treatment with rituximab and zanubrutinib. The primary endpoint included progression-free survival (PFS) in the intent-to-treat (ITT) population whereas the secondary endpoints included overall response rate (ORR), complete response (CR), and duration of response. Further, next-generation sequencing (NGS) was used for detection of different oncogenic mutations closely related to DLBCL pathogenesis. From October 2020 to March 2022, 26 patients were enrolled, and 23 of them were evaluated for efficacy after receiving 3 cycles of ZR-CHOP treatment. 1-year PFS and OS were 80.8% and 88.5% respectively while expected PFS and OS for 2-years are 74.0% and 88.5% respectively with median follow-up of 16.7 months and ORR was 91.3% (CR: 82.61%; PR: 8.70%). Oncogenic mutations closely related to DLBCL pathogenesis were assessed in 20 patients using NGS. B-cell receptor and NF-κB pathway gene mutations were detected in 10 patients, which occurred in MYD88 (7/19), CD79B (4/19), CARD11 (5/19), and TNFAIP3 (2/19). Hematological adverse events (AEs) ≥ grade 3 included neutropenia (50%), thrombocytopenia (23.1%), and anemia (7.7%) whereas non-hematological AEs ≥ grade 3 included pulmonary infection (19.2%). ZR-CHOP is safe and effective for treating treatment naïve non-GCB DLBCL patients with extranodal involvement. Clinicaltrials.gov, NCT04835870.

MicroRNA sequencing for biomarker detection in the diagnosis, classification and prognosis of Diffuse Large B Cell Lymphoma

Despite being considered a single disease, Diffuse Large B Cell Lymphoma (DLBCL) presents with variable backgrounds, which results in heterogeneous outcomes among patients, with 40% of them still having primary refractory disease or relapse. Thus, novel biomarkers are needed. In addition, multiple factors regarding its pathogenesis remain unclear. In this context, recent investigations point to the relevance of microRNAs (miRNAs) in cancer. However, regarding DLBCL, there is inconsistency in the data reported. Therefore, in this work, the main goals were to determine a miRNA set with utility as biomarkers for DLBCL diagnosis, classification, prognosis and treatment response, as well as to decipher the mechanism of action of deregulated miRNAs in the origin of the disease. We analyzed miRNA expression in a cohort of 78 DLBCL patients and 17 controls using small RNA sequencing and performed a miRNA-mRNA interaction network analysis. This way, we were able to define new miRNA expression signatures for diagnosis, classification, treatment response and prognosis, and we identified plausible mechanisms of action by which deregulated miRNAs could be involved in DLBCL pathogenesis. In summary, our study remarks that miRNAs could play an important role in DLBCL.

Identification of the shared gene signatures and molecular pathways in systemic lupus erythematosus and diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) incidence is higher in systemic lupus erythematosus (SLE) patients than the general population, but the molecular mechanisms behind this link remain ambiguous. The aim of this study was to investigate shared gene signatures and molecular pathways between SLE and DLBCL. We procured expression profiles of SLE and DLBCL from public databases and identified common differentially expressed genes (DEGs). Functional pathway enrichment and protein-protein interaction (PPI) analyses were performed on these shared genes. The molecular complex detection technology (MCODE) and eXtreme Gradient Boosting (XGBoost) machine learning algorithm were used to select core shared genes, followed by Gene Set Enrichment Analysis (GSEA) and immune infiltration analysis. We identified 54 DEGs as shared genes, among which CD177, CEACAM1, GPR84 and IFIT3 were identified as core shared genes. These genes showed strong associations with inflammatory and immune response pathways. We found a significant positive correlation between GPR84 and IFIT3 expression levels and the immune microenvironment. Decreased expression levels of GPR84 and IFIT3 were linked to enhanced immune therapy sensitivity, potentially due to lower dysregulation scores during low expression. We also discovered that TP53 mutations might elevate CD177 and GPR84 expression and that reduced expression levels of GPR84 and IFIT3 were linked with better overall survival and progression-free survival in DLBCL patients. Our study provides valuable insights into the shared molecular mechanisms underpinning the pathogenesis of SLE and DLBCL. These findings could potentially offer new biomarkers and therapeutic targets for SLE and DLBCL.

Presence of EBV antigens detected by a sensitive method in pediatric and adult Diffuse Large B-cell lymphomas.

In 2017, the World Health Organization (WHO) confirmed a new entity, Epstein Barr virus (EBV) + Diffuse large B cell lymphoma (DLBCL), not otherwise specified (NOS). Traces of EBV transcripts were described in lymphomas, including DLBCL, that were diagnosed as EBV negative by conventional methods. The aim of this study was to detect viral genome by qPCR, as well as LMP1 and EBNA2 transcripts, with a more sensitive method in DLBCL cases from Argentina. Fourteen cases originally considered as EBV negative expressed LMP1 and/or EBNA2 transcripts. In addition, LMP1 and/or EBNA2 transcripts were also observed in bystander cells. However, EBERs+ cells cases by conventional ISH showed higher numbers of cells with LMP1 transcripts and LMP1 protein. In the cases that were EBERS- in tumor cells but with expression of LMP1 and/or EBNA2 transcripts, the viral load was below the limit of detection. This study provides further evidence that EBV could be detected in tumor cells by more sensitive methods. However, higher expression of the most important oncogenic protein, LMP1, as well as increased viral load, are only observed in cases with EBERs+ cells by conventional ISH, suggesting that traces of EBV might not display a key role in DLBCL pathogenesis.

BTG2 SUPER‐ENHANCER MUTATIONS DISRUPT TFAP4 BINDING AND DYSREGULATE BTG2 EXPRESSION IN DIFFUSE LARGE B‐CELL LYMPHOMA

Introduction: Diffuse large B-cell lymphoma (DLBCL), the most common lymphoid malignancy, remains incurable in ∼40% of patients. Coding-genome sequencing efforts identified several genes/pathways altered in this disease, as well as genetic subgroups of potential clinical relevance. However, the large non-coding portion of the genome remained largely unexplored. We recently identified a pervasive hypermutation mechanism targeting active super-enhancers (SEs) in >90% of DLBCL and leading to dysregulation of multiple genes, including well-known lymphoma oncogenes (Bal et al., Nature 2022). As evidence of oncogenic relevance, we demonstrated that mutational hotspots in the BCL6, BCL2 and CXCR4 SEs impair the binding of specific transcriptional repressors, preventing the gene negative regulation and creating oncogenic dependencies in DLBCL cells. Here we aimed to define the pathogenic role of mutations targeting the intragenic SE (iSE) of the BTG2 gene, the second most commonly mutated in DLBCL. BTG2 encodes a member of the B-cell translocation gene (BTG)/TOB family involved in transcriptional co-activation and modulation of mRNA abundance. BTG2 is also a recurrent target of somatic missense mutations (6%–11% of DLBCL), suggesting a major role in the pathogenesis of this disease. Methods: We screened 243 DLBCL cases for the presence of mutational hotspots within the BTG2-iSE, and combined in silico prediction, DNA-binding assays (Reverse-ChIP, electromobility-shift assay, ChIP-qPCR), RNA-seq and CRISPR/Cas9 editing approaches in isogenic BTG2 mutant versus WT DLBCL cell lines to identify transcription factors bound to the SE and disrupted by the mutation. Results: We identified a recurrent mutational cluster affecting the BTG2-iSE in 52/243 (21%) DLBCLs, with preferential enrichment in ST2 subgroup. CRISPR-Cas9 mediated correction of the mutation in 3 DLBCL cell lines led to counter selection and reduced BTG2 expression, consistent with oncogenic addiction. In silico motif prediction and in vitro DNA-binding assays, followed by validation in multiple isogenic DLBCL cell lines, identified TFAP4 as a major transcription factor that binds to the WT, but not to the mutated site. TFAP4 is an important regulator of B-cell proliferation and cell fate decisions, which can function as a transcriptional activator or repressor in germinal center B-cells, and acts downstream of/in parallel with c-MYC. Of note, introduction of SE hotspot mutations in WT DLBCL cells was associated with increased BTG2 expression, confirming a direct link between SE mutations and deregulated gene expression through escape from TFAP4-mediated suppression. Conclusions: These findings suggest a major role for BTG2 deregulation by SE aberrant somatic hypermutation in the pathogenesis and heterogeneity of DLBCL, with implications for precision classification and potential therapeutic targeting of DLBCL. Keywords: aggressive B-cell non-Hodgkin lymphoma, tumor biology and heterogeneity No conflicts of interests pertinent to the abstract.

EXPRESSION OF HUMAN LEUKOCYTE ANTIGENS GENETIC POLYMORPHISMS IN PATIENTS WITH DIFFUSE LARGE B‐CELL LYMPHOMA

Introduction: Diffuse Large B- cell Lymphoma (DLBCL) is characterized by genetic and clinical heterogeneity. Different loci within the human leukocyte antigen (HLA) region have been implicated in susceptibility and disease control of DLBCL. Methods: HLA typing was performed using Sequence-Specific Oligonucleotide (SSO) and Sequence-Specific Primer (SSP) in 60 DLBCL patients and 250 healthy adult donors from local Bone Marrow registry. Statistical analysis was conducted with version 29.0 of IBM SPSS. The phenotypic frequencies of HLA-A, HLA-B, HLA-C, HLA-DRB1 and HLA-DQB1 between patients and controls were compared with the 2-sided Fisher’s exact test. Results with p-value < 0.05 were considered statistically significant. Odds Ratios (OR) with 95% Confidence Intervals were calculated to further strength the results. Additionally, a follow-up analysis was performed by calculating Bonferroni-adjusted p-values (pc). Thereafter HLA polymorphisms that showed statistically significant difference were included in univariate and multivariate survival analysis together with the patients clinical-biological characteristics (age, stage, LDH, R-IPI). The R programming language, version 4.2.2 and specifically the “survivalAnalysis” package version 0.3.0. were used to investigate the associations of each factor with the Overall Survival (OS) and the Progression Free Survival (PFS). Results: DLBCL patients displayed a lower frequency of HLA-C*12 (6.7% vs. 34.7%, p = 0.001, pc = 0.00001, OR = 0.13, 95% CI [0.05, 0.38]), HLA-DRB1*16 (15% vs. 29.7%, p = 0.02, pc = 0.04, OR = 0.42, 95% CI [0.19, 0.89]) and HLA-DRB1*03 (58.3% vs. 77.5%, p = 0.02, pc = 0.01, OR = 0.40, 95% CI [0.22, 0.74]) compared to healthy individuals. In univariate analysis only advanced stage, high LDH and low versus high R-IPI had statistically significant impact on OS (p values 0.007, 0.003 and 0.002 respectively) and PFS (p-values 0.001, 0.002 and <0.001 respectively). Interestingly the Cox regression analysis used to evaluate the impact of LDH together with the HLA-DQB1*03 polymorphism on OS showed that although normal LDH is a good prognostic factor with HR = 0.33 95% CI [0.17 – 0.65] p-value = 0.001), the combination of normal LDH with DQB1*03 with HR 2.07 95% CI [1.06–4.07] indicates a significantly increased risk of death (p-value = 0.034). Regarding PFS the LDH- DQB1*03 model displayed also statistical significancy (p = 0.001) in a similar way with DQB1*03 increasing the risk of death while keeping LDH within normal ranges. Conclusions: Our results suggest that DLBCL patients express certain genetic types of HLA in lower frequency compared to healthy individuals. Antigens represented less frequently may act protectively in the development of the DLBCL. However, the presence of rarely represented HLA types failed to prove any positive impact on OS and PFS indicating the complexity of DLBCL pathogenesis. Keywords: aggressive B-cell non-Hodgkin lymphoma, diagnostic and prognostic biomarkers No conflicts of interests pertinent to the abstract.

ADAR1-mediated RNA editing promotes B cell lymphomagenesis

Diffuse large B cell lymphoma (DLBCL) is one of the most common types of aggressive lymphoid malignancies. Here, we explore the contribution of RNA editing to DLBCL pathogenesis. We observed that DNA mutations and RNA editing events are often mutually exclusive, suggesting that tumors can modulate pathway outcomes by altering sequences at either the genomic or the transcriptomic level. RNA editing targets transcripts within known disease-driving pathways such as apoptosis, p53 and NF-κB signaling, as well as the RIG-I-like pathway. In this context, we show that ADAR1-mediated editing within MAVS transcript positively correlates with MAVS protein expression levels, associating with increased interferon/NF-κB signaling and Tcell exhaustion. Finally, using targeted RNA base editing tools to restore editing within MAVS 3'UTR in ADAR1-deficient cells, we demonstrate that editing is likely to be causal to an increase in downstream signaling in the absence of activation by canonical nucleic acid receptorsensing.

Bioinformatics analysis of the pathogenic link between Epstein-Barr virus infection, systemic lupus erythematosus and diffuse large B cell lymphoma

Epstein-Barr virus (EBV) is a risk factor for diffuse large B-cell lymphoma (DLBCL) and systemic lupus erythematosus (SLE). While prior research has suggested a potential correlation between SLE and DLBCL, the molecular mechanisms remain unclear. The present study aimed to explore the contribution of EBV infection to the pathogenesis of DLBCL in the individuals with SLE using bioinformatics approaches. The Gene Expression Omnibus database was used to compile the gene expression profiles of EBV-infected B cells (GSE49628), SLE (GSE61635), and DLBCL (GSE32018). Altogether, 72 shared common differentially expressed genes (DEGs) were extracted and enrichment analysis of the shared genes showed that p53 signaling pathway was a common feature of the pathophysiology. Six hub genes were selected using protein–protein interaction (PPI) network analysis, including CDK1, KIF23, NEK2, TOP2A, NEIL3 and DEPDC1, which showed preferable diagnostic values for SLE and DLBCL and involved in immune cell infiltration and immune responses regulation. Finally, TF-gene and miRNA-gene regulatory networks and 10 potential drugs molecule were predicted. Our study revealed the potential molecular mechanisms by which EBV infection contribute to the susceptibility of DLBCL in SLE patients for the first time and identified future biomarkers and therapeutic targets for SLE and DLBCL.

Lymphocyte to monocyte ratio predicts survival and is epigenetically linked to miR-222-3p and miR-26b-5p in diffuse large B cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma. 10–20% of the patients present with bone marrow (BM) involvement which predicts a worse survival. This study aimed to determine the prognostic significance of serum miR-222-3p, miR-26b-5p, EBV-miR-BHRF1-2-5p, and EBV-miR-BHRF1-2-3p and correlate their levels to clinical and haematological markers in DLBCL with special emphasis on the lymphocyte-monocyte ratio (LMR) and neutrophil-monocyte ratio. We also studied the role of BM BMI1 and PIM2 proteins in predicting BM infiltration. Serum miRNAs were studied on 40 DLBCL and 18 normal individuals using qRT-PCR. BMI1 and PIM2 proteins were studied on BM biopsies by immunohistochemistry. The results were correlated with clinical and follow-up data. All the studied miRNAs were dysregulated in DLBCL serum samples. BMI1 and PIM2 were expressed in 67% and 77.5% of BM samples, respectively. LMR was significantly associated with disease-free survival (DFS) (P = 0.022), miR-222-3P (P = 0.043), and miR-26b-5p (P = 0.043). EBV-miR-BHRF1-2-3p was significantly correlated to haemoglobin level (P = 0.027). MiR-222-3p, miR-26b-5p, and EBV-miR-BHRF1-2-5p expressions were significantly correlated to each other (P = 0.001). There was no significant correlation between the studied markers and follow-up data. LMR is a simple method for predicting survival in DLBCL. MiR-222-3p and miR-26b-5p may be implicated in an immunological mechanism affecting patients’ immunity and accordingly influence LMR. The correlation between miR-222-3p, miR-26b-5p, and EBV-miR-BHRF1-2-5p may indicate a common mechanism among the 3 miRNAs that may explain DLBCL pathogenesis.

In Silico Identification and Functional Characterization of Genetic Variations across DLBCL Cell Lines.

Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphoma and frequently develops through the accumulation of several genetic variations. With the advancement in high-throughput techniques, in addition to mutations and copy number variations, structural variations have gained importance for their role in genome instability leading to tumorigenesis. In this study, in order to understand the genetics of DLBCL pathogenesis, we carried out a whole-genome mutation profile analysis of eleven human cell lines from germinal-center B-cell-like (GCB-7) and activated B-cell-like (ABC-4) subtypes of DLBCL. Analysis of genetic variations including small sequence variants and large structural variations across the cell lines revealed distinct variation profiles indicating the heterogeneous nature of DLBCL and the need for novel patient stratification methods to design potential intervention strategies. Validation and prognostic significance of the variants was assessed using annotations provided for DLBCL samples in cBioPortal for Cancer Genomics. Combining genetic variations revealed new subgroups between the subtypes and associated enriched pathways, viz., PI3K-AKT signaling, cell cycle, TGF-beta signaling, and WNT signaling. Mutation landscape analysis also revealed drug-variant associations and possible effectiveness of known and novel DLBCL treatments. From the whole-genome-based mutation analysis, our findings suggest putative molecular genetics of DLBCL lymphomagenesis and potential genomics-driven precision treatments.

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.

Biclonal Diffuse Large B-cell Lymphoma Commonly Characterized by Partial Trisomy 18q Involving MALT1 and BCL2.

A 68-year-old man was admitted because of a left shoulder mass and swollen right testis. Pathological examinations indicated a diagnosis of diffuse large B-cell lymphoma (DLBCL) with the CD20+BCL6+MUM1+BCL2+CD10-MYC- phenotype in both lesions. G-banding of soft tissue showed 47,XY,+18, whereas testicular cells showed 47,X,+X,-Y,der (4) t (4;18) (p15;?),del (5) (q?),+13. Fluorescence in situ hybridization detected additional MALT1 and BCL2 signals in both lesions. Southern blot demonstrated different IGH rearrangements between the soft tissue and testis. The patient was diagnosed with biclonal DLBCL with different karyotypes but similar immunophenotypes. Partial trisomy 18q involving MALT1 and BCL2 may be commonly involved in the pathogenesis of this biclonal DLBCL.