Exosomes and Resistance to Immunotherapy in Aggressive Non-Hodgkin B-cell Lymphomas (B-NHL)

Diffuse large B-cell lymphomas (DLBCL) are highly aggressive and heterogeneous B-cell lymphoma that would imminently be fatal without treatment. Monoclonal anti-CD20 antibody, rituximab, in combination of CHOP chemotherapy (R-CHOP) is widely used with favourable results. Although more than half of patients achieve long-term remission, many are not cured with this immunotherapy. Decreased CD20 expression has been postulated to be one of the most important contributing to rituximab resistance. Moreover, R-CHOP therapies are sometimes ineffective, and new treatment strategies based notably on host immune responses modulation are being explored. Among them, programmed cell death ligand 1 (PD-L1) protein was identified as a potent predicting biomarker in DLBCL. Exosomes are small membrane vesicles secreted by several cell types during exocytic fusion of multivesicular bodies with the plasma membrane. Many cancer cells have been shown to secrete exosomes in greater amounts than normal cells. Exosome secretion may contribute to drug resistance. Indeed, exosome release from B-cell Non-Hodgkin Lymphoma (B-NHL), by the expression of CD20, has been suggest to act as decoy targets upon rituximab exposure, allowing lymphoma cells to escape from humoral immunotherapy. Finally, as exosome composition seems to be cell and tissue specific, they are highly suitable to serve as diagnostic markers.

Our hypothesis is that high expression of the immunotherapeutic targets (CD20, PD-L1) on exosomes derived from aggressive or resistant B-NHL may allow tumor cells to escape therapeutic antibodies, and thus contribute in vivo to therapeutic resistance. For this objective, we will used exosomes derived from DLBCL human cells and exosomes isolated from plasma of DLBCL patients. We will analyze, on these microvesicles, CD20 and PDL-1 expression in function of DLBCL sub-types and outcome of patients. Moreover, exosome capacity to interfere with immunotherapy will be also studied from in vitro and in vivo (xenografts) models.