Our team studies the molecular and cellular mechanisms that lead, after contact with an antigen, to the transformation of a naive or memory B lymphocyte to a plasma cell, an effector cell producing antibodies.
Implementation of an in vitro differentiation model and integrated strategy
In order to understand the processes involved, we have implemented an in vitro differentiation model from B lymphocytes extracted from blood samples provided by the French Blood Agency (EFS) in Rennes. This model is used for
- determinating the role of interleukin 2 (IL-2) and more generally of the signals produced by the micro-environmental cells, in particular the Tfh cells,
- decomposing the differentiation steps, and isolating the progenitor cells that can become plasma cells,
- understanding why memory B lymphocytes have increased differentiation capability compared to naive B lymphocytes,
- identifying the crucial molecules involved in the functional modifications of these cells,
- applying the results obtained for normal differentiation to the study of tumor diseases derived from germinal center cells (follicular lymphoma, DLBCL), from cells during differentiation (Waldenström disease), or from plasma cells (multiple myeloma).
To perform these investigations, we use an integrated strategy based on sorting specific cell populations, characterizing these cells properties (by cytometry and confocal microscopy), their gene expressions (transcriptomics by microarray or RNA-seq) and regulations (mapping of the histone marks, of methylation or hydroxy-methylation, 5hmC, of DNA and of microRNA profiles).
Our recent results have shown that:
- IL-2 is required at a very early stage during cell stimulation, and determines the future ability of the cells to differentiate into plasma cells (Le Gallou et al., JI, 2012);
- The cell differentiation into a plasma cell is linked to its ability to divide, then to repress the IL-4/STAT6 and TGFb signaling pathways, finally, during the ultimate division, to favor the expression of genes specific to the plasma cell identity by adding 5hmC close by or at their loci (Caron et al., Cell Rep, 2015);
- The fast response to IL-2 actively involves the transcription factor BACH2, the main switch of the plasma cell differentiation (Hipp et al., Nat Comm, 2017).
Differentiation of tumor B lymphocytes
The team also studies the genetic and epigenetic modifications of tumor B cells in follicular lymphoma (FL) and diffuse large B-cell lymphoma (DLBCL). In FL, we identified a phospho-STAT3 (pSTAT3) hyper-signaling correlated with an increase of IL-21 secretion by Tfh and with the expression of some target genes of pSTAT3. However the key gene of the B cell differentiation into plasma cell, PRDM1, a pSTAT3 target gene of, has a weak expression in FL, highlighting the existence of genetic and epigenetic abnormalities related to the disease. We aim to understand these deregulations, in particular by showing the importance of the acetylation properties in the B differentiation and in the control of the PRDM1 gene expression. Our work supports clinicians in their choice to use new therapeutics targeting the epigenome, such as the histone acetyltransferase inhibitors (HDACi), in treating FL patients.
As for the technology employed, we implemented a gene capture technique (using Agilent SureSelect) for detecting variants in coding and non-coding regions, followed by high throughput sequencing on an Illumina NGS platform (the BIOSIT/Biogenouest GEH core facility in Rennes), the bioanalysis being performed with the Agilent software, SureCall.
Deregulation during lymphomagenesis
In order to reinforce our analysis of the normal and tumor B lymphocyte differentiation, we aim at identifying the microRNAs involved in the epigenetic control of this process. By integrating miR-seq and transcriptome analyses of highly purified cells, we are able to identify a miRNA expression signature involved in the transitions between the different stages of the B lymphocyte maturation / differentiation, and to look for modifications that may exist in FL tumor cells for instance.
A translational axis is carried out to complement fundamental research, through the investigation of cohorts of patients diagnosed with lymphoma. We aim at identifying novel blood biomarkers having a diagnostic or prognostic value for the patient. We explore blood cells, plasma proteins, circulating free DNA as well as total RNAs and microRNAs in blood.
Our recent results have shown that:
- Plasma soluble PD-L1 is a prognostic factor in diffuse large B-cell lymphoma (Rossille et al., Leukemia, 2014 & 2017);
- Specific blood mononuclear cells are suppressors of the antitumor response in diffuse large B-cell lymphoma (Azzaoui et al., Blood, 2016).
Azzaoui et al., Blood, 2016
T-cell defect in diffuse large B-cell lymphomas involves expansion of myeloid-derived suppressor cells. Azzaoui I, Uhel F, Rossille D, Pangault C, Dulong J, Le Priol J, Lamy T, Houot R, Le Gouill S, Cartron G, Godmer P, Bouabdallah K, Milpied N, Damaj G, Tarte K, Fest T, Roussel M. Blood. 2016 Aug 25;128(8):1081-92. PMID: 27338100
Caron et al., Cell Rep, 2015
Cell-Cycle-Dependent Reconfiguration of the DNA Methylome during Terminal Differentiation of Human B Cells into Plasma Cells. Caron G, Hussein M, Kulis M, Delaloy C, Chatonnet F, Pignarre A, Avner S, Lemarié M, Mahé EA, Verdaguer-Dot N, Queirós AC, Tarte K, Martín-Subero JI, Salbert G, Fest T. Cell Rep. 2015 Nov 3;13(5):1059-71. PMID: 26565917
Hipp et al., Nat Comm, 2017
IL-2 imprints human naive B cell fate towards plasma cell through ERK/ELK1-mediated BACH2 repression. Hipp N, Symington H, Pastoret C, Caron G, Monvoisin C, Tarte K, Fest T, Delaloy C.
Nat Commun. 2017 Nov 13;8(1):1443. PMID: 29129929
Le Gallou et al., JI, 2012
IL-2 requirement for human plasma cell generation: coupling differentiation and proliferation by enhancing MAPK-ERK signaling. Le Gallou S, Caron G, Delaloy C, Rossille D, Tarte K, Fest T. J Immunol. 2012 Jul 1;189(1):161-73. PMID: 22634617
Rossille et al., Leukemia, 2014
High level of soluble programmed cell death ligand 1 in blood impacts overall survival in aggressive diffuse large B-Cell lymphoma: results from a French multicenter clinical trial. Rossille D, Gressier M, Damotte D, Maucort-Boulch D, Pangault C, Semana G, Le Gouill S, Haioun C, Tarte K, Lamy T, Milpied N, Fest T; Groupe Ouest-Est des Leucémies et Autres Maladies du Sang; Groupe Ouest-Est des Leucémies et Autres Maladies du Sang. Leukemia. 2014 Dec;28(12):2367-75. PMID: 24732592
Rossille et al., Leukemia, 2017
Soluble programmed death-ligand 1 as a prognostic biomarker for overall survival in patients with diffuse large B-cell lymphoma: a replication study and combined analysis of 508 patients. Rossille D, Azzaoui I, Feldman AL, Maurer MJ, Labouré G, Parrens M, Pangault C, Habermann TM, Ansell SM, Link BK, Tarte K, Witzig TE, Lamy T, Slager SL, Roussel M, Milpied N, Cerhan JR, Fest T. Leukemia. 2017 Apr;31(4):988-991. PMID: 28035137