Extracellular vesicles shed by follicular lymphoma B cells promote the polarization of bone marrow stromal cell niche

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Dumontet, Erwan | Pangault, Céline | Roulois, David | Desoteux, Matthis | Léonard, Simon | Marchand, Tony | Latour, Maelle | Legoix, Patricia | Loew, Damarys | Dingli, Florent | Dulong, Joëlle | Flecher, Erwan | Coulouarn, Cédric | Cartron, Guillaume | Fest, Thierry | Tarte, Karin

Edité par CCSD ; American Society of Hematology -

International audience. Follicular Lymphoma (FL) originates in the lymph nodes (LN) and infiltrates bone marrow (BM) early in the course of the disease. BM FL B cells are characterized by a lower cytological grade, a decreased proliferation, and a specific phenotypic and subclonal profile. Mesenchymal stromal cells (MSC) obtained from FL BM display a specific gene expression profile (GEP), including enrichment for a lymphoid-stromal cell signature, and an increased capacity to sustain FL B-cell growth. However, the mechanisms triggering the formation of the medullar FL permissive stromal niche have not been yet identified. In the current work, we demonstrated that FL B cells produced extracellular vesicles (EVs) that could be internalized by BM-MSC, making them more efficient to support FL B-cell survival and quiescence. Accordingly, EVs purified from FL BM plasma activated TGF-b dependent and independent pathways in BM-MSC, modified their GEP, triggering an upregulation of factors classically associated with hematopoietic stem cell niche, including CXCL12 or angiopoietin-1. Moreover, we provided the first characterization of BM FL B-cell GEP, allowing the definition of the landscape of molecular interactions they could engage with EV-primed BM-MSC. This work identified FL-derived EVs as putative mediators of BM stroma polarization and supported further investigation of their clinical interest for targeting the crosstalk between BM-MSC and malignant B cells.

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