Germinal Center B-cell Research Articles

Abstract PO-032: A novel strategy to overcome resistance of diffuse large B-cell lymphoma to venetoclax

Abstract Approximatively 40% of diffuse large B-cell lymphoma (DLBCL) patients exhibit primary resistance to standard therapy. Moreover, relapse is a common event in first-line responders. Overexpression of BCL-2 is a major determinant of resistance to chemotherapy in several B-cell neoplasms, including DLBCL. While venetoclax, a specific BCL-2 inhibitor, has dramatically changed the therapeutic landscape of other B-cell malignancies, only 12% of DLBCL patients exhibit a complete response to venetoclax, with a mean progression-free survival of 1 month. In this scenario, new therapeutic strategies are urgently needed. We tested the possibility to overcome the resistance of DLBCL cells to venetoclax by rewiring their reactive oxygen species (ROS) set point, which is higher in cancer cells compared to their healthy counterparts. We employed a panel of 14 DLBCL cell lines of both germinal center B-cell (GCB) and activated B-cell (ABC) derivation. Cell death, ROS accumulation, and NADPH levels were evaluated upon treatment of DLBCL cells with three inhibitors of NADPH production, the central electron donor required to maintain ROS scavengers in their reduced form. The synergism between venetoclax and inhibitors of NADPH production was assessed through isobologram analysis. RNA-Seq, quantitative real-time PCR (qRT-PCR), and western blot techniques were used to dissect the mechanism of cooperation between venetoclax and inhibition of NADPH production. The Zebrafish model was used for in vivo validation of the therapeutic approach. We observed that inhibiting NADPH production dramatically improves the response to venetoclax by more than 500-fold, while no toxic effects were observed in normal B-cells. By generating isogenic cell lines with differing sensitivity to venetoclax, we demonstrated that the resistance to this drug positively correlates with the expression of the anti-apoptotic protein BCL-xL. Moreover, RNA-seq and protein analyses indicated that the increase of ROS levels engages the integrated stress response (ISR). Pharmacological inhibition and gene silencing of key effectors of the ISR rescued DLBCL cells from cell death induced by our therapeutic strategy. We also confirmed the ROS-dependency of BCL-xL downregulation using both ROS scavengers and by pulsing cells with exogenous hydrogen peroxide. Finally, in vivo studies confirmed the sensitization of DLBCL cells to venetoclax upon the inhibition of NADPH production. Taken together, these results provide the first proof-of-principle evidence for a ROS-based strategy to increase the therapeutic window of venetoclax in DLBCL, suggesting a viable therapeutic avenue to treat refractory patients. Citation Format: Francesco Ciccarese, Vittoria Raimondi, Alberto Corradin, Natascia Tiso, Giovanni Risato, Micol Silic-Benussi, Ilaria Cavallari, Donna Mia D'Agostino, Vincenzo Ciminale. A novel strategy to overcome resistance of diffuse large B-cell lymphoma to venetoclax [abstract]. In: Proceedings of the Fourth AACR International Meeting on Advances in Malignant Lymphoma: Maximizing the Basic-Translational Interface for Clinical Application; 2024 Jun 19-22; Philadelphia, PA. Philadelphia (PA): AACR; Blood Cancer Discov 2024;5(3_Suppl):Abstract nr PO-032.

Action of circulating and infiltrating B cells in the immune microenvironment of colorectal cancer by single-cell sequencing analysis.

The complexity of the immune microenvironment has an impact on the treatment of colorectal cancer (CRC), one of the most prevalent malignancies worldwide. In this study, multi-omics and single-cell sequencing techniques were used to investigate the mechanism of action of circulating and infiltrating B cells in CRC. By revealing the heterogeneity and functional differences of B cells in cancer immunity, we aim to deepen our understanding of immune regulation and provide a scientific basis for the development of more effective cancer treatment strategies. To explore the role of circulating and infiltrating B cell subsets in the immune microenvironment of CRC, explore the potential driving mechanism of B cell development, analyze the interaction between B cells and other immune cells in the immune microenvironment and the functions of communication molecules, and search for possible regulatory pathways to promote the anti-tumor effects of B cells. A total of 69 paracancer (normal), tumor and peripheral blood samples were collected from 23 patients with CRC from The Cancer Genome Atlas database (https://portal.gdc.cancer.gov/). After the immune cells were sorted by multicolor flow cytometry, the single cell transcriptome and B cell receptor group library were sequenced using the 10X Genomics platform, and the data were analyzed using bioinformatics tools such as Seurat. The differences in the number and function of B cell infiltration between tumor and normal tissue, the interaction between B cell subsets and T cells and myeloid cell subsets, and the transcription factor regulatory network of B cell subsets were explored and analyzed. Compared with normal tissue, the infiltrating number of CD20+B cell subsets in tumor tissue increased significantly. Among them, germinal center B cells (GCB) played the most prominent role, with positive clone expansion and heavy chain mutation level increasing, and the trend of differentiation into memory B cells increased. However, the number of plasma cells in the tumor microenvironment decreased significantly, and the plasma cells secreting IgA antibodies decreased most obviously. In addition, compared with the immune microenvironment of normal tissues, GCB cells in tumor tissues became more closely connected with other immune cells such as T cells, and communication molecules that positively regulate immune function were significantly enriched. The role of GCB in CRC tumor microenvironment is greatly enhanced, and its affinity to tumor antigen is enhanced by its significantly increased heavy chain mutation level. Meanwhile, GCB has enhanced its association with immune cells in the microenvironment, which plays a positive anti-tumor effect.

Effect of AVM0703 treatment on the limitations of R-CHOP and survival in a model applicable to ABC subtype DLBCL.

e19060 Background: The current treatment regimen for DLBCL consisting of rituximab-cyclophosphamide-doxorubicin-vincristine-prednisone (RCHOP), is challenged by molecular and prognostic characterization of DLBCL. Activated B-cell (ABC) lymphoma has a significantly worse prognosis (5 yr OS rate: 45% - 56%) than germinal center B-cell (GCB) lymphoma (78% - 80%) after RCHOP treatment. Around 40% of patients ultimately relapse and/or develop primary refractory disease, cardiotoxicity and long-term secondary malignancies. Efforts are being made to improve the RCHOP backbone by including dose intensification and by the addition of new agents to increase the efficacy and reduced toxicity of RCHOP (McKelvey EM Cancer 1976; Wilson WH Blood 2002; Molina TJ JCO 2014; Coiffier B Hematology 2016). AVM0703, an immunomodulatory drug, mobilizes bispecific γδ and inv-TCR double-positive novel T and NKT cells. In a previous study employing an aggressive, immune resistant A20 mouse lymphoma model (Bascuas T J Transl Med. 2016), neoadjuvant AVM0703 was additive/synergistic, when cyclophosphamide/fludarabine (CyFlu) was dosed 3 and 24 hr later, with no additional toxicities. In the present study we combined AVM0703 with RCHOP to evaluate the efficacy in A20 mice model. Methods: 10 week old Balb/c mice were injected with 2x106 murine A20 B-cells in the flank and were randomized (1:1 male: female) into 1) Placebo 2) 3 cycles RCHOP 3) 3 cycles AVM0703 (18mg/kg HED) 4) 3 cycles AVM0703+RCHOP, when tumor size reached ~100 mm3. Mice who achieved complete remission (CR) were re-challenged at 21-25 wks later. Pre and post re-challenge, presence of memory cells was analyzed using flow cytometer. All mice were monitored continuously as per the IACUC protocol. Results: Mice treated with the combination of AVM0703+RCHOP achieved superior CR compared to RCHOP alone, which was not curative in any mice. In first phase of the study, 3 out of 11 AVM0703 +RCHOP treated mice showed CR after only 1-cycle. In second phase, 2 of 12 mice survived in CR for >150 days after 3 cycles, whereas no RCHOP mice survived beyond 2 cycles. AVM0703+RCHOP treated mice in long-term CR, had memory cells (CD44hi-Cd62low) pre- and post re-challenge, and no A20 engraftment, suggesting strong immunological memory induced by AVM0703+RCHOP. Conclusions: AVM+RCHOP demonstrated anti-tumor activity in A20 lymphoma mice, with reduced toxicity, compared to RCHOP. Larger preclinical studies are underway to confirm the activity of AVM0703+RCHOP against RCHOP resistant ABC DLBCL, and the potential to reduce total RCHOP exposure to only 3 cycles while maintaining or improving efficacy. [Table: see text]

Genomic profiling in a subgroup analysis of patients (pts) with diffuse large B-cell lymphoma (DLBCL) and extranodal (EN) sites of involvement in the phase 3 Pola-R-CHP versus R-CHOP (POLARIX) study.

7061 Background: The prognosis and survival outcomes of pts with EN involvement remain a challenge for DLBCL management. In the Phase 3 POLARIX study (NCT03274492), Pola-R-CHP demonstrated significantly improved progression-free survival (PFS) compared with R-CHOP in previously untreated DLBCL (Tilly et al. 2022). This retrospective analysis assessed clinical outcomes and genomic patterns of pts with DLBCL and EN disease. Methods: POLARIX methods were previously described (Tilly et al. 2022). Using a data cutoff of June 15, 2022, this analysis assessed pts with EN involvement as determined by investigators. Additional outcomes and genomics analyses were performed on pts whose EN status was confirmed from documented radiographic lesions or bone marrow biopsy with denotation of EN disease sites. Hazard ratios (HRs) for investigator-assessed PFS were adjusted for age (≤60 vs >60) and sex. Cell of origin (COO) by NanoString, mutation analysis by whole exome sequencing, and global gene expression profiling by RNAseq were performed centrally. Results: In POLARIX, 616/879 pts (70%) had identified EN involvement. After a median follow-up of 39.7 months, pts showed improved PFS with Pola-R-CHP vs R-CHOP (HR 0.72, 95% confidence interval [CI]: 0.55–0.96), with a 2-year PFS of 75% vs 66%. A total of 556 pts (Pola-R-CHP, n=279; R-CHOP, n=277) had confirmed sites of EN involvement, defined as pts with EN radiographic lesions or bone marrow disease. In these pts, PFS favored Pola-R-CHP vs R-CHOP but the difference was not statistically significant (HR 0.84, 95% CI: 0.63–1.13). Of pts with confirmed EN disease, 429 had COO results (activated B-cell, 145 [34%]; germinal center B-cell, 223 [52%]; unclassified DLBCL, 61 [14%]). Mutation data and frequencies of select clinically relevant mutations (Ptashkin, 2023) across EN sites were available for 364 pts (Table). Gene expression data were available for 418 pts; genes involved in proliferation (E2F or PI3K signaling targets and checkpoint genes) and regulated by IRF4, OCT2 and XBP1, were commonly upregulated in pts with EN disease. Conclusions: Results in pts with DLBCL with EN involvement suggest superior PFS with Pola-R-CHP vs R-CHOP. Ongoing analyses will further assess the independent impact of EN status on outcome. POLARIX represents the largest cohort of pts with annotated EN disease and systematic genomic analysis, providing new insights into the genomics of these pts. Clinical trial information: NCT03274492 . [Table: see text]

Total Alkaloids of Sophora alopecuroides Linn. Attenuates Rheumatoid Arthritis Through Regulating Follicular Helper T Cells.

Rheumatoid arthritis (RA) is a chronic autoimmune disease with abnormal differentiation of follicular helper T (Tfh) cells, Total alkaloids of Sophora alopecuroides Linn. (Leguminosae) (TASA) have potential effects on collagen-induced arthritis (CIA) mice, while the mechanism needs further elucidation. The purpose of this study is to explore the regulation of TASA on rheumatoid arthritis and related mechanism. The proportion of Tfh and B lymphocytes in peripheral blood lymphocytes of RA patients was examined by flow cytometry. We constructed the collagen induced arthritis DBA/1J mice model. Between days 15 and 45 following the first immunization, the mice were treated intraperitoneally with saline, TASA (100, 50, and 25 mg/kg), and dexamethasone (DXM) for 30 days. Molecular biological techniques such as FCM, PCR, ELISA, and Western-blotting were used to examine Tfh cells and associated signal pathways. Our results indicated that the follicular helper T cells and B lymphocytes in rheumatoid arthritis patients were significantly increased compared with the healthy control. The percentage of Tfh cells are correlated with RA related inflammatory factors. Total alkaloids of Sophora alopecuroides Linn. could significantly attenuate joint swelling. Meanwhile, it reduced the frequencies of spleen Tfh, B lymphocytes and the expression of TLR2, TLR9, p-NF-κBp65, CXCR5, Bcl-6, ICOS of ankle joints in CIA mice. Total alkaloids of Sophora alopecuroides Linn. may down-regulate the frequency and function of Tfh cells and inhibit GCB cells via TLRs/NF-κB signal pathway to relieve the immune-pathological progression of CIA mice.

Novel highly immunogenic DNA vaccine regimen potently activates lymph nodes in macaques.

Abstract Background We evaluated a novel DNA vaccine delivery by LION™ nanoparticles for its ability to induce innate and adaptive immune responses in Rhesus macaques. Methods CoV-2 Spike or HIV Env DNA were formulated with a cationic nanocarrier (Lipid InOrganic Nanoparticle; LION™) administered via the IM route. Chemokine/cytokine and vaccine-specific responses were monitored in blood and lymph nodes (LN) by proteomics, flow, antibody assays. Results DNA/LION™ induced strong cellular and higher humoral responses than DNA/Electroporation and induced rapid (4-24hr) transient innate responses. Flow analysis showed activation of T, B, myeloid incl. dendritic cells in blood and their trafficking to LN with a strong increase of Tfh, Germinal Center Tfh CD4 and CD8 cells. Cell subsets were activated by cytokine networks incl. CXCL11, IL-7 and IL-15. GC-B cell activation directly correlated with increase of FLT3L and CXCL12 and importantly with antibody levels. Conclusion DNA/LION™ led to robust induction of cellular and humoral responses against different immunogens, serving as promising platform of effective nucleic acid vaccine delivery. Transient cytokine responses, incl. IL-15, resulted in strong activation of draining lymph nodes, and contributed to shaping adaptive (cellular and humoral) immunity. Our data showed rapid and coordinated cytokine responses to the vaccine and highlight the important role of innate responses to vaccination in modulating adaptive immunity.

Phosphatidic Acid Promoting the Generation of Interleukin-17A Producing Double-Negative T Cells by Enhancing mTORC1 Signaling in Lupus.

The goal was to investigate the role and intracellular regulatory mechanisms of double-negative T (DNT) cells in the pathogenesis of systemic lupus erythematosus (SLE). DNT cells were assessed in murine models, patients with SLE, and controls using flow cytometry (FCM). DNT cells from either resiquimod (R848) or vehicle-treated C57BL/6 (B6) mice were cultured with B cells from R848-treated mice to explore functions. Differential mechanistic target of rapamycin (mTOR) pathway signaling in DNT cells measured using FCM and quantitative polymerase chain reaction was validated by rapamycin inhibition. Candidate lipid metabolites detected using liquid chromatography with electrospray ionization mass spectrometry/mass spectrometry were functionally assessed in DNT cell cultures. DNT cells were markedly increased in both spontaneous and induced mouse lupus models and in patients with SLE. Expanded DNT cells from R848-treated B6 mice produced elevated interleukin (IL)-17A and IgG with increased germinal center B (GCB) cells. Expansion of DNT cells associated with activation of mTORC1 pathway that both IL-17A levels and the number of DNT cells exhibited dose-dependent reduction with rapamycin treatment. Lipidomics studies revealed differential patterns of lipid metabolites in T cells of R848-treated mice. Among candidate metabolites, elevated phosphatidic acid (PA) that was partially controlled by phospholipase D2 increased the expression of the mTORC1 downstream target p-S6 and positively expanded IL-17A-producing DNT cells. Similarly, elevated proportions of circulating DNT cells in patients with SLE correlated with disease activity and proteinuria, and IL-17A secretion was elevated after in vitro PA stimulation. The accumulation of PA in T cells could activate the mTORC1 pathway, promoting DNT cell expansion and IL-17A secretion, resulting in GCB cell abnormalities in lupus.

A computational approach for deciphering the interactions between proximal and distal gene regulators in GC B-cell response.

Delineating the intricate interplay between promoter-proximal and -distal regulators is crucial for understanding the function of transcriptional mediator complexes implicated in the regulation of gene expression. The present study aimed to develop a computational method for accurately modeling the spatial proximal and distal regulatory interactions. Our method combined regression-based models to identify key regulators through gene expression prediction and a graph-embedding approach to detect coregulated genes. This approach enabled a detailed investigation of the gene regulatory mechanisms for germinal center B cells, accompanied by dramatic rearrangements of the genome structure. We found that while the promoter-proximal regulatory elements were the principal regulators of gene expression, the distal regulators fine-tuned transcription. Moreover, our approach unveiled the presence of modular regulators, such as cofactors and proximal/distal transcription factors, which were co-expressed with their target genes. Some of these modules exhibited abnormal expression patterns in lymphoma. These findings suggest that the dysregulation of interactions between transcriptional and architectural factors is associated with chromatin reorganization failure, which may increase the risk of malignancy. Therefore,our computational approachhelps decipherthe transcriptional cis-regulatory code spatially interacting.

Abstract 6549: Mechanistic models of tumor and patient heterogeneity explain and predict clinical outcomes of large B-cell lymphoma (LBCL) treatment

Abstract Introduction: Heterogeneity between patients and within tumors poses challenges to effective cancer treatment. Drug combinations can overcome heterogeneity by increasing the probability that a patient will have response to one or more drugs. This approach is successful in numerous disease settings, but technological advances have led to new approach to addressing heterogeneity: precision approaches to stratify patients into subpopulations with more uniform, stronger responses to specific drugs. These strategies can be implemented together to improve patient outcomes. We have developed computational mechanistic models of cancer treatment in the context of both sources of heterogeneity which explain and predict clinical outcomes of treatment of LBCL with combination therapy and CAR T-cell therapy. Combination therapy: Our novel population tumor kinetics (pop-TK) model simulates clinical combination therapy outcomes by implementing multidrug dose response functions in heterogeneous populations of tumor cells, within heterogeneous cohorts of patients. Informed by the outcomes of novel drugs in phase 2 trials in relapsed/refractory (r/r) patients, the pop-TK model accurately predicted of outcomes of seven first-line phase 3 trials of novel combinations. Most notably, informed by treatment of r/r LBCL with polatuzumab-vedotin (pola), the pop-TK predicted the success of modifying the standard treatment regimen (RCHOP) with pola before the clinical trial results were published. The pola combination improves overall survival (OS) and PFS in Activated B-Cell (ABC) LBCL (hazard ratio (HR): OS 0.3, PFS 0.4), but reduces OS (HR: 1.6) and does not improve PFS (HR: 1.0) in Germinal Center B-Cell (GCB) LBCL. The subtype specific difference in PFS was also predictable based on subtype results of r/r trials (predicted HR: ABC 0.3, GCB 0.9). CAR T-cell therapy: We used a population pharmacokinetic/pharmacodynamic (pop-PK/PD) model of CAR T-cell therapy to reproduce the PFS distribution and the distribution CAR T-cell abundance for CAR T therapy in r/r LBCL patients. The impact of tumor size on patient outcome in our model and in clinical studies led us to computationally explore the impact treating smaller tumors with CAR T-cell therapy on treatment outcomes. We found that using detectable circulating tumor DNA (ctDNA) as a biomarker for administering CAR T-cell therapy immediately after RCHOP increased the proportion of simulated patients without a second disease progression event by 30% (HR: 0.43 [0.34, 0.55]). Conclusions: The pop-TK model supports LBCL subtype biomarker for pola performance, and the pop-PK/PD model demonstrates that detectable ctDNA is a potential biomarker for early CAR T-cell administration. These examples of model-driven precision trial design have the potential to improve outcomes using readily-available biomarkers and existing therapies. Citation Format: Amy E. Pomeroy, Adam C. Palmer. Mechanistic models of tumor and patient heterogeneity explain and predict clinical outcomes of large B-cell lymphoma (LBCL) treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6549.

Abstract 7586: TOX loss-of-function(TOXLOF)results in BCR hyperactivation andenhanced responses to BCR-targeting in diffuse large B cell lymphomas (DLBCL)

Abstract DLBCL originate from germinal center B cells (GCB). The ABC-DLBCL subtype, characterized by activation of B-cell receptor (BCR) signaling and downstream NF-kB pathway, carries a poor outcome. Up to 30% of ABC-DLBCL present TOXLOF mutations, suggesting that TOX function as a tumor suppressor. Our analysis of TOX expression along the germinal center B-cell differentiation program (naïve → GCB → plasma cells) showed that TOX expression paralleled NF-kB activity with highest levels in plasma cells (P<0.001, vs. either naïve and GCB). We thus propose that TOX acts as a transcriptional gatekeeper in GCB cells to prevent early activation of NF-kB thus enabling differentiation into plasma cells while restraining lymphomagenesis. We generated a conditional GCB TOX KO mouse model, induced the GC reaction with a T-cell antigen and found that TOX KO (vs. TOX WT, 10 mice per condition) had impaired differentiation of plasma cells (p<0.001) and hyperproliferative Ki67+ GCB cells (p<0.05). We then generated (by CRISPR) an isogenic TOXLOF ABC-DLBCL cell line (TMD8) and found upregulation of genes in the NF-kB pathway (q-value <0.05, vs. TMD8). Furthermore, TMD8-TOXLOF cells showed increased secretion of autocrine cytokines IL6 and IL10, and higher STAT3 phosphorylation (p<0.05 for all comparisons, vs. TMD8-TOXWT cells) all compatible with NF-kB activation. Tumor microenvironmental cues can hyperactivate BCR and downstream NF-kB in ABC-DLBCL. We thus implanted isogenic TMD8 cells in mice (n = 10) and determined pathway activation by phospho-flow. We found massive activation of SYK, BTK, PLCG2 (from the BCR) and p65 (from NF-kB) in TMD8-TOXLOF vs. TMD8-TOXWT tumors (all p<0.01), and vs. these cell lines cultured in vitro (all p<0.01). To determine whether these features can be therapeutically exploited, we conducted a viability screening using a panel of 20 clinical-phase targeted therapies relevant to ABC-DLBCL. We found that BTK inhibitor acalabrutinib (BCR pathway) and MALT1 inhibitor JNJ67690246 (NF-kB pathway) were 2-3 fold more active in TMD8-TOXLOF vs. TMD8-TOXWT cells (all p<0.05). We then xenografted isogenic TMD8 cells (n = 10 mice per condition) and, when tumors reached 150 mm3, we randomized mice to vehicle vs. acalabrutinib 30 mg/kg/day by oral gavage (human dose equivalent). Acalabrutinib was significantly more active in TMD8-TOXLOF tumors (vs. TMD8-TOXWT, p=0.0008), which translated into significantly prolonged survival (p<0.05). This acalabrutinib effect was accompanied by significant reduction of BTK, SYK and PLCG2 phosphorylation in TMD8-TOXLOF tumors (p<0.0001, all comparisons). Thus, TOXLOF leads to hyperactivation of the BCR and NF-kB signaling pathways in ABC-DLBCL cells, rendering them hypersensitive to BCR-targeted therapies, delineating a potential mechanism-based therapeutic approach for ABC-DLBCL TOXLOF patients. Citation Format: Eloisi Caldas Lopes, Maria Revuelta, Rossella Marullo, Leandro Cerchietti. TOX loss-of-function(TOXLOF)results in BCR hyperactivation andenhanced responses to BCR-targeting in diffuse large B cell lymphomas (DLBCL) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7586.

Abstract 1912: Targeting Trop-2 with sacituzumab govitecan (IMMU-132) suppresses the tumor growth in diffuse large B cell lymphoma

Abstract Introduction: Sacituzumab govitecan (SG), also termed IMMU-132, is an antibody-drug conjugate, linking an anti-Trop-2 antibody and the topoisomerase I inhibitor, SN-38. Clinically, SG has shown promising therapeutic effects in patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer. However, the efficacy of SG in diffuse large B-cell lymphoma (DLBCL) remains unexplored. In this study, we sought to determine whether SG can efficiently inhibit cell proliferation and tumor growth of DLBCL by using both in vitro and in vivo models. Methods: We examined the cytotoxicity of SG in the activated B-cell like (ABC)-subtype-DLBCL cell lines, Riva (Ri-1), HBL-1, and SU-DHL-2, and the germinal center B-cell (GCB)-subtype-DLBCL cell lines, SU-DHL-4, SU-DHL-5, and SU-DHL-6 by MTT assay. We assessed the distributions of cell cycle phase and apoptosis in the aforementioned DLBCL cell lines treated with SG for 24 h or 48 h using flow cytometry and Annexin V staining. We confirmed apoptosis (cleavage of poly ADP-ribose polymerase [PARP] and caspase-3) and detected DNA damage (γH2AX and 53BP1)-related protein expression in SU-DHL-2 and SU-DHL-6 cell lines treated with SG at various concentrations for 48 h using western blotting, compared to untreated cells. To examine the anti-tumor effect of SG in vivo, NOD-SCID nude mice of Riva-xenograft mouse models were randomized into a control group and an SG-treated group. Results: Flow cytometry and western blotting revealed overexpression of Trop-2 on the surface of untreated ABC-DLBCL and GCB-DLBCL cell lines. In this study, we showed that SG treatment reduced cell viability in all six DLBCL cell lines with nanomolar IC50 values. Exposing SG to DLBCL cells significantly increased cell cycle arrest at the G2/M and sub-G1 phases of all six DLBCL cell lines. Annexin V staining revealed that SG induced apoptosis in all six DLBCL cell lines. Western blotting confirmed apoptosis induction by showing a dose-dependent upregulation of cleaved PARP and cleaved caspases-3 by SG treatment, along with decreased expression of survivin in both SU-DHL-2 and SU-DHL-6 cells. SG also upregulated the expression of γH2AX and 53BP1 in both SU-DHL-2 and SU-DHL-6 cells. Furthermore, we found that tumor growth of Riva cells in vivo was significantly reduced by treatment with SG when compared with untreated control. Conclusion: SG suppresses tumor growth of ABC-DLBCL and GCB-DLBCL cells in both in vitro and in vivo models by inducing cell cycle arrest, apoptosis, and DNA damage. These findings provide a rationale for transitioning SG to clinical trials for treating patients with relapsed or refractory DLBCL. Citation Format: Jakie Ting, Ming-Feng Wei, Hsiao-Wei Lee, Keng-Hsueh Lan, Ann-Lii Cheng, Sung-Hsin Kuo. Targeting Trop-2 with sacituzumab govitecan (IMMU-132) suppresses the tumor growth in diffuse large B cell lymphoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1912.

Nodal Low-Grade B-Cell Lymphoma Co-Expressing CD5 and CD10 but Not CD23, IRTA1, or Cyclin D1: The Diagnostic Challenge of a Splenic Marginal Zone Lymphoma.

The diagnosis of lymphoma is based on histopathological and immunophenotypical features. CD5 and CD10 are traditionally considered a T-cell antigen and a germinal center B-cell antigen, respectively. It is very unusual for a low-grade B-cell lymphoma (BCL) to co-express CD5 and CD10. Although the biologic basis or clinical significance of such co-expression is unclear, this rare event may pose a significant diagnostic challenge. Here, we report a case of a 63-year-old male presenting with bilateral cervical lymphadenopathy and lymphocytosis. Histologically, the nodal tumor was largely diffuse with neoplastic small atypical lymphocytes co-expressing CD5, CD10, and CD20, but not CD23 or cyclin D1. The leukemic cells in the peripheral blood exhibited hairy projections. Taking together the marked splenomegaly, involvement of lymph nodes, bone marrow, and peripheral blood, a final diagnosis of splenic marginal zone lymphoma (SMZL) was reached. The patient was alive with partial response for 10 months after immunochemotherapy. The dual expression of CD5 and CD10 is extremely unusual for low-grade BCL and may lead to an erroneous diagnosis. Integrating the findings into peripheral blood smear tests, flow cytometry, histopathology, imaging, and clinical features is mandatory to exclude other lymphoma types and to reach a correct diagnosis, particularly for a case with nodal presentation.

Notch2 controls developmental fate choices between germinal center and marginal zone B cells upon immunization

Sustained Notch2 signals induce trans-differentiation of Follicular B (FoB) cells into Marginal Zone B (MZB) cells in mice, but the physiology underlying this differentiation pathway is still elusive. Here, we demonstrate that most B cells receive a basal Notch signal, which is intensified in pre-MZB and MZB cells. Ablation or constitutive activation of Notch2 upon T-cell-dependent immunization reveals an interplay between antigen-induced activation and Notch2 signaling, in which FoB cells that turn off Notch2 signaling enter germinal centers (GC), while high Notch2 signaling leads to generation of MZB cells or to initiation of plasmablast differentiation. Notch2 signaling is dispensable for GC dynamics but appears to be re-induced in some centrocytes to govern expansion of IgG1+ GCB cells. Mathematical modelling suggests that antigen-activated FoB cells make a Notch2 dependent binary fate-decision to differentiate into either GCB or MZB cells. This bifurcation might serve as a mechanism to archive antigen-specific clones into functionally and spatially diverse B cell states to generate robust antibody and memory responses.

Abstract P35: High-grade B-cell lymphomas with 11q aberrations show a dark zone expression profile similar to Burkitt lymphoma but with additional extension towards intermediate germinal center B-cells

Abstract P35: High-grade B-cell lymphomas with 11q aberrations show a dark zone expression profile similar to Burkitt lymphoma but with additional extension towards intermediate germinal center B-cells

Crossprotection induced by virus-like particles containing influenza dual-hemagglutinin and M2 ectodomain.

Aims: To develop an effective universal vaccine against antigenically different influenza viruses. Materials & methods: We generated influenza virus-like particles (VLPs) expressing the H1 and H3 antigens with or without M2e5x. VLP-induced immune responses and crossprotection against H1N1, H3N2 or H5N1 viruses were assessed to evaluate their protective efficacy. Results: H1H3M2e5x immunization elicited higher crossreactive IgG antibodies than H1H3 VLPs. Upon challenge, both VLPs enhanced lung IgG, IgA and germinal center B-cell responses compared with control. While these VLPs conferred protection, H1H3M2e5x showed greater lung viral load reduction than H1H3 VLPs with minimal body weight loss. Conclusion: Utilizing VLPs containing dual-hemagglutinin, along with M2e5x, can be a vaccination strategy for inducing crossprotection against influenza A viruses.

Sinonasal DLBCL: molecular profiling identifies subtypes with distinctive prognosis and targetable genetic features

AbstractPrimary sinonasal diffuse large B-cell lymphoma (PSDLBCL) is a rare lymphoma with a variable prognosis and a unique relapse/dissemination pattern involving the central nervous system and skin. The underlying molecular mechanisms leading to this heterogeneity and progression pattern remain uncharted, hampering patient-tailored treatment. To investigate associated mechanisms, we analyzed clinical data and used immunohistochemistry, gene-expression profiling, cytogenetics, and next-generation sequencing in a cohort of 117 patients with PSDLBCL. The distribution in cell-of-origin (COO) was 68 (58%) activated B-cell (ABC), 44 (38%) germinal center B-cell (GCB), and 5 (4%) unclassifiable. COO was significantly associated with progression-free survival (PFS) and lymphoma-specific mortality (LSM) in both the overall cohort (5-year PFS: ABC, 43% vs GCB, 73%; LSM: ABC, 45% vs GCB, 14%) and in the subgroup of patients receiving immunochemotherapy (5-year PFS: ABC, 55% vs GCB, 85%; LSM: ABC, 28% vs GCB, 0%). ABC lymphomas were mainly MCD class, showing a high prevalence of MYD88 (74%) and CD79B (35%) mutations compared with GCB lymphomas (MYD88 23%; CD79B 10%) (P < .01). The ABC subtype frequently displayed cMYC/BCL2 coexpression (76% vs 18% GCB; P < .001) and HLA-II loss (48% vs 10% GCB; P < .001). PD-L1 expression and copy-number alterations were rare. All lymphomas were Epstein-Barr virus-negative. Our data suggest molecular profiling as a potent tool for detecting prognostic subgroups in PSDLBCL, exposing links to known relapse/dissemination sites. The ABC subgroup’s MCD genetic features, shared with lymphomas at other nonprofessional lymphoid sites, make them potential candidates for targeted B-cell and toll-like receptor signaling therapy.

BMP-ACVR1 Axis is Critical for Efficacy of PRC2 Inhibitors in B-Cell Lymphoma.

EZH2 is the catalytic subunit of the histone methyltransferase Polycomb Repressive Complex 2 (PRC2), and its somatic activating mutations drive lymphoma, particularly the germinal center B-cell type. Although PRC2 inhibitors, such as tazemetostat, have demonstrated anti-lymphoma activity in patients, the clinical efficacy is not limited to EZH2-mutant lymphoma. In this study, Activin A Receptor Type 1 (ACVR1), a type I Bone Morphogenetic Protein (BMP)receptor, is identified as critical for the anti-lymphoma efficacy of PRC2 inhibitors through a whole-genome CRISPR screen. BMP6, BMP7, and ACVR1 are repressed by PRC2-mediated H3K27me3, and PRC2 inhibition upregulates their expression and signaling in cell and patient-derived xenograft models. Through BMP-ACVR1 signaling, PRC2 inhibitors robustly induced cell cycle arrest and B cell lineage differentiation in vivo. Remarkably, blocking ACVR1 signaling using an inhibitor or genetic depletion significantly compromised the in vitro and in vivo efficacy of PRC2 inhibitors. Furthermore, high levels of BMP6 and BMP7, along with ACVR1, are associated with longer survival in lymphoma patients, underscoring the clinical relevance of this study. Altogether, BMP-ACVR1 exhibits anti-lymphoma function and represents a critical PRC2-repressed pathway contributing to the efficacy of PRC2 inhibitors.

Memory B cell subsets have divergent developmental origins that are coupled to distinct imprinted epigenetic states.

Memory B cells (MBCs) are phenotypically and functionally diverse, but their developmental origins remain undefined. Murine MBCs can be divided into subsets by expression of CD80 and PD-L2. Upon re-immunization, CD80/PD-L2 double-negative (DN) MBCs spawn germinal center B cells (GCBCs), whereas CD80/PD-L2 double-positive (DP) MBCs generate plasmablasts but not GCBCs. Using multiple approaches, including generation of an inducible GCBC-lineage reporter mouse, we demonstrate in a T cell-dependent response that DN cells formed independently of the germinal center (GC), whereas DP cells exhibited either extrafollicular (DPEX) or GCBC (DPGC) origins. Chromatin and transcriptional profiling revealed similarity of DN cells with an early memory precursor. Reciprocally, GCBC-derived DP cells shared distinct genomic features with GCBCs, while DPEX cells had hybrid features. Upon restimulation, DPEX cells were more prone to divide, while DPGC cells differentiated toward IgG1+ plasmablasts. Thus, MBC functional diversity is generated through distinct developmental histories, which imprint characteristic epigenetic patterns onto their progeny, thereby programming them for divergent functional responses.

Non-IG::MYC in diffuse large B-cell lymphoma confers variable genomic configurations and MYC transactivation potential

MYC translocation occurs in 8–14% of diffuse large B-cell lymphoma (DLBCL), and may concur with BCL2 and/or BCL6 translocation, known as double-hit (DH) or triple-hit (TH). DLBCL-MYC/BCL2-DH/TH are largely germinal centre B-cell like subtype, but show variable clinical outcome, with IG::MYC fusion significantly associated with inferior survival. While DLBCL-MYC/BCL6-DH are variable in their cell-of-origin subtypes and clinical outcome. Intriguingly, only 40-50% of DLBCL with MYC translocation show high MYC protein expression (>70%). We studied 186 DLBCLs with MYC translocation including 32 MYC/BCL2/BCL6-TH, 75 MYC/BCL2-DH and 26 MYC/BCL6-DH. FISH revealed a MYC/BCL6 fusion in 59% of DLBCL-MYC/BCL2/BCL6-TH and 27% of DLBCL-MYC/BCL6-DH. Targeted NGS showed a similar mutation profile and LymphGen genetic subtype between DLBCL-MYC/BCL2/BCL6-TH and DLBCL-MYC/BCL2-DH, but variable LymphGen subtypes among DLBCL-MYC/BCL6-DH. MYC protein expression is uniformly high in DLBCL with IG::MYC, but variable in those with non-IG::MYC including MYC/BCL6-fusion. Translocation breakpoint analyses of 8 cases by TLC-based NGS showed no obvious genomic configuration that enables MYC transactivation in 3 of the 4 cases with non-IG::MYC, while a typical promoter substitution or IGH super enhancer juxtaposition in the remaining cases. The findings potentially explain variable MYC expression in DLBCL with MYC translocation, and also bear practical implications in its routine assessment.

Diffuse Large B Cell Lymphoma: Immunohistochemical Classification According to Hans Algorithm and Association With Outcome in A Moroccan Institution.

The most prevalent subtype of non-Hodgkin lymphoma is diffuse large B-cell lymphoma (DLBCL). Germinal center B-cell (GCB) and non-germinal center B-cell (non GCB) are the two main biologically different molecular subtypes identified utilizing an immunohistochemistry-based approach. Our objective in this study is to analyze the impact of immunohistochemical subtypes of DLBCL (GCB or non GCB) on demographic and clinicopathological parameters, response to chemotherapy and survival outcomes. This is a retrospective study including 106 cases of DLBCL collected in the department of pathology, Hassan II university hospital, Fez (Morocco), over a period of 12 years (January 2010-September 2022). The subtypes of DLBCLs were defined according to Hans algorithm, using immunohistochemistry by three biomarkers (CD10, BCL6, MUM1). Independent t tests and analyses of variance were used for the comparison of mean values. We employed the SPSS 26.0 program to achieve this. A statistically significant value was set at P < .05. Seventy-five patients (71%) were non-GCB subtype, while thirty-one patients (29%) had the GCB immunosubtype. We have found a significant (P < .05) correlations between DLBCL immunosubtypes and treatment responses on one hand and survival in the other hand. In the GCB subtype, the response rate and survival were significantly improved. A significant association was found between Ki 67 expression and survival on univariate analysis. On multivariate analysis, we note a correlation between Ki 67 expression, DLBCL immunohistochemical subtypes and survival outcome. Non GCB subtype is associated with poor response to treatment and inferior survival outcome compared to GCB subtype in Moroccan context, especially when combined with high expression of Ki 67 marker.