Single-hit genome editing optimized for maturation in B cells redirects their specificity toward tumor antigens.

T-cell-based adoptive immunotherapy is a new pillar of cancer care. Tumor-redirected B cells could also contribute to therapy if their manipulation to rewire immunoglobulin (Ig) genes is mastered. We designed a single-chain Ig-encoding cassette ("scFull-Ig") that redirects antigen specificity when inserted at a single position of the IgH locus. This design, which places combined IgH and IgL variable genes downstream of a pVH promoter, nevertheless preserves all Ig functional domains and the intrinsic mechanisms that regulate expression from the IgM B cell receptor (BCR) expression to Ig secretion, somatic hypermutation and class switching. This single-locus editing provides an efficient and safe strategy to both disrupt endogenous Ig expression and encode a new Ig paratope. As a proof of concept, the functionality of scFull BCR and/or secreted Ig was validated against two different classical human tumor antigens, HER2 and hCD20. Once validated in cell lines, the strategy was extended to primary B cells, confirming the successful engineering of BCR and Ig expression and the ability of scFull-Ig to undergo further class switching. These results further pave the way for future B cell-based adoptive immunotherapy and strategies to express a therapeutic mAb with a variety of switched H-chains that provide complementary functions.

BHLHE41, a transcriptional repressor involved in physiological processes and tumor development.

BHLHE41 is a nuclear transcriptional repressor that belongs to the basic helix-loop-helix protein superfamily. BHLHE41 expression tends to be restricted to specific tissues and is regulated by environmental cues and biological events. BHLHE41 homodimerizes or heterodimerizes with various partners, influencing its transcription factor function. BHLHE41 is involved in the regulation of many physiological processes implicated in tissue/organ homeostasis, such as myogenesis, adipogenesis, circadian rhythms and DNA repair. At cellular level, BHLHE41 is involved in the regulation of mesenchymal stem cell properties, tissue-specific macrophage functions and lymphoid lineage physiology. In several cancer types, BHLHE41 modulates the expression of different transcriptional programs influencing cell cycle control, apoptosis, invasiveness, epithelial to mesenchymal transition and hypoxia response in the tumor environment. Depending on the cancer cell type, BHLHE41 can act as a tumor suppressor or an oncogene, and could be a target for innovative therapies. This review summarizes the available knowledge on BHLHE41 structure, biological functions, regulation and potential partners, as well as its role in physiological processes, and its implication in major cancer steps.

CD38, CD39, and BCL2 differentiate disseminated forms of high-grade B-cell lymphomas in biological fluids from Burkitt lymphoma and diffuse large B-cell lymphoma.

High-grade B-cell lymphomas (HGBCL) represent a heterogeneous group of very rare mature B-cell lymphomas. The 4th revised edition of the WHO Classification of Tumors of Hematopoietic and Lymphoid Tissues (WHO-HAEM) previously defined two categories of HGBCL: the so-called double-hit (DHL) and triple-hit (THL) lymphomas, which were related to forms harboring MYC and BCL2 and/or BCL6 rearrangements, and HGBCL, NOS (not otherwise specified), corresponding to entities with intermediate characteristics between diffuse large B-cell lymphoma (DLBCL) and Burkitt lymphoma (BL), without rearrangement of the MYC and BCL2, and/or BCL6 genes. In the 5th edition of the WHO-HAEM, DHL with MYC and BCL2 rearrangements or THL were reassigned as DLBCL/HGBCL with MYC and BCL2 rearrangements (DLBCL/HGBL-MYC/BCL2), whereas the category HGBCL, NOS remains unchanged. Characterized by an aggressive clinical presentation and a poor prognosis, HGBCL is often diagnosed at an advanced, widespread stage, leading to potential disseminated forms with a leukemic presentation, or spreading to the bone marrow (BM) or other biological fluids. Flow cytometric immunophenotypic study of these disseminated cells can provide a rapid method to identify HGBCL. However, due to the scarcity of cases, only limited data about the immunophenotypic features of HGBCL by multiparametric flow cytometry are available. In addition, identification of HGBCL cells by this technique may be challenging due to clinical, pathological, and biological features that can overlap with other distinct lymphoid malignancies, including Burkitt lymphoma (BL), diffuse large B-cell lymphoma (DLBCL), and even B acute lymphoblastic leukemia (B-ALL). In this study, we aimed to characterize the detailed immunophenotypic portrait of HGBCL, evaluating by multiparametric flow cytometry (MFC) the expression of 26 markers on biological samples obtained from a cohort of 10 newly-diagnosed cases and comparing their level of expression with normal peripheral blood (PB) B lymphocytes (n = 10 samples), tumoral cells from patients diagnosed with B-ALL (n = 30), BL (n = 13), or DLBCL (n = 22). We then proposed a new and simple approach to rapidly distinguish disseminated forms of HGBCL, BL, and DLBCL, using the combination of MFC data for CD38, BCL2, and CD39, the three most discriminative markers explored in this study. We finally confirmed the utility of the scoring system previously proposed by Khanlari to distinguish HGBCL cells from B lymphoblasts of B-ALL. In conclusion, we described a distinct immunophenotypic portrait of HGBCL cells and proposed a strategy to differentiate these cells from other aggressive B lymphoma entities in biological samples.

FCGR3A F158V alleles frequency differs in multiple myeloma patients from healthy population.

FCGR3A presents a single nucleotide polymorphism at location 158 (V/F), which affects its binding to the fragment crystallizable (Fc) of antibodies (Abs). FcγRIIIa-158 V allotype has the highest affinity and is associated with a better clinical response to IgG1 monoclonal Abs (mAb) treatment. We compared the allele frequency of FCGR3A-F158V polymorphism in cohorts of patients with B-cell lymphoproliferative disorders, including multiple myeloma (MM), monoclonal gammopathy of undetermined significance (MGUS), non-Hodgkin lymphoma (NHL), and B-cell chronic leukemia (B-CLL). FCGR3A-158F homozygous were enriched and tended to be in MM and MGUS patients, respectively; but neither in B-CLL nor in NHL patients. We identified a significantly lower concentration of CD8 T-cells and resting memory CD4 T-cells in MM patients bone marrow with the F/F genotype, associated with an increase in the macrophage percentage. In contrast, natural killer cells increased in V/V homozygous patients. This suggests a deregulation of the immune microenvironment in FCGR3A-F/F homozygous patients. However, we did not observe difference in response following treatment combining chemotherapy associated or not with daratumumab, an IgG1 mAb direct against CD38. Our findings suggest that FCGR3A F158V polymorphism can regulate the immune environment and affect the development of tumor plasma cells.

Quantitative Integrative Survival Prediction in Multiple Myeloma Patients Treated With Bortezomib-Based Induction, High-Dose Therapy and Autologous Stem Cell Transplantation.

PURPOSE: Given the high heterogeneity in survival for patients with multiple myeloma, it would be clinically useful to quantitatively predict the individual survival instead of attributing patients to two to four risk groups as in current models, for example, revised International Staging System (R-ISS), R2-ISS, or Mayo-2022-score. PATIENTS AND METHODS: Our aim was to develop a quantitative prediction tool for individual patient's 3-/5-year overall survival (OS) probability. We integrated established clinical and molecular risk factors into a comprehensive prognostic model and evaluated and validated its risk discrimination capabilities versus R-ISS, R2-ISS, and Mayo-2022-score. RESULTS: A nomogram for estimating OS probabilities was built on the basis of a Cox regression model. It allows one to translate the individual risk profile of a patient into 3-/5-year OS probabilities by attributing points to each prognostic factor and summing up all points. The nomogram was externally validated regarding discrimination and calibration. There was no obvious bias or overfitting of the prognostic index on the validation cohort. Resampling-based and external evaluation showed good calibration. The c-index of the model was similar on the training (0.76) and validation cohort (0.75) and significantly higher than for the R-ISS (P < .001) or R2-ISS (P < .01). CONCLUSION: In summary, we developed and validated individual quantitative nomogram-based OS prediction. Continuous risk assessment integrating molecular prognostic factors is superior to R-ISS, R2-ISS, or Mayo-2022-score alone.

MRE11 and TREX1 control senescence by coordinating replication stress and interferon signaling.

Oncogene-induced senescence (OIS) arrests cell proliferation in response to replication stress (RS) induced by oncogenes. OIS depends on the DNA damage response (DDR), but also on the cGAS-STING pathway, which detects cytosolic DNA and induces type I interferons (IFNs). Whether and how RS and IFN responses cooperate to promote OIS remains unknown. Here, we show that the induction of OIS by the H-RASV12 oncogene in immortalized human fibroblasts depends on the MRE11 nuclease. Indeed, treatment with the MRE11 inhibitor Mirin prevented RS, micronuclei formation and IFN response induced by RASV12. Overexpression of the cytosolic nuclease TREX1 also prevented OIS. Conversely, overexpression of a dominant negative mutant of TREX1 or treatment with IFN-ß was sufficient to induce RS and DNA damage, independent of RASV12 induction. These data suggest that the IFN response acts as a positive feedback loop to amplify DDR in OIS through a process regulated by MRE11 and TREX1.

Integrative single-cell chromatin and transcriptome analysis of human plasma cell differentiation.

ABSTRACT: Plasma cells (PCs) are highly specialized cells representing the end stage of B-cell differentiation. We have shown that PC differentiation can be reproduced in vitro using elaborate culture systems. The molecular changes occurring during PC differentiation are recapitulated in this in vitro differentiation model. However, a major challenge exists to decipher the spatiotemporal epigenetic and transcriptional programs that drive the early stages of PC differentiation. We combined single cell (sc) RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin with high throughput sequencing (scATAC-seq) to decipher the trajectories involved in PC differentiation. ScRNA-seq experiments revealed a strong heterogeneity of the preplasmablastic and plasmablastic stages. Among genes that were commonly identified using scATAC-seq and scRNA-seq, we identified several transcription factors with significant stage specific potential importance in PC differentiation. Interestingly, differentially accessible peaks characterizing the preplasmablastic stage were enriched in motifs of BATF3, FOS and BATF, belonging to activating protein 1 (AP-1) transcription factor family that may represent key transcriptional nodes involved in PC differentiation. Integration of transcriptomic and epigenetic data at the single cell level revealed that a population of preplasmablasts had already undergone epigenetic remodeling related to PC profile together with unfolded protein response activation and are committed to differentiate in PC. These results and the supporting data generated with our in vitro PC differentiation model provide a unique resource for the identification of molecular circuits that are crucial for early and mature PC maturation and biological functions. These data thus provide critical insights into epigenetic- and transcription-mediated reprogramming events that sustain PC differentiation.

An atlas of cells in the human tonsil.

Palatine tonsils are secondary lymphoid organs (SLOs) representing the first line of immunological defense against inhaled or ingested pathogens. We generated an atlas of the human tonsil composed of >556,000 cells profiled across five different data modalities, including single-cell transcriptome, epigenome, proteome, and immune repertoire sequencing, as well as spatial transcriptomics. This census identified 121 cell types and states, defined developmental trajectories, and enabled an understanding of the functional units of the tonsil. Exemplarily, we stratified myeloid slan-like subtypes, established a BCL6 enhancer as locally active in follicle-associated T and B cells, and identified SIX5 as putative transcriptional regulator of plasma cell maturation. Analyses of a validation cohort confirmed the presence, annotation, and markers of tonsillar cell types and provided evidence of age-related compositional shifts. We demonstrate the value of this resource by annotating cells from B cell-derived mantle cell lymphomas, linking transcriptional heterogeneity to normal B cell differentiation states of the human tonsil.