Program: Oral and Poster Abstracts
Session: 622. Non-Hodgkin Lymphoma: Biology, excluding Therapy: Poster I
Methods: Whole blood from 56 DLBCL at diagnosis and 45 healthy donors (HD) were analyzed by flow cytometry. Quantitative Real Time PCR were analyzed on Taqman@ array microfluidic cards. Cytokine levels in plasma and culture supernatants were measured by Luminex and Elisa. T-cell proliferation after monocyte depletion or treatment with inhibitors, was analyzed by CFSE assay.
Results: By flow cytometry, we identified an expansion of G-MDSC (LinnegHLA-DRnegCD33posCD11bpos) and M-MDSC (CD14posHLA-DRlow) in DLBCL compared to HD (p<0.001). Interestingly, only M-MDSC number was correlated with the International Prognostic Index (IPI), the event-free survival (EFS), and the number of circulating Treg. Furthermore, T-cell proliferation was restored after monocyte depletion. To identify the mechanism of suppression involved, we evaluated the gene expression of key enzymes (ARG1, IDO1, NOS2, HO-1 and PTGS2) or immunomodulatory molecules (IL10, TGFβ1, CD274/PD-L1, S100A8, S100A9, S100A12) involved in MDSC biology. ARG1, IDO1, IL10, CD274/PD-L1 and S100A12 were significantly up-regulated in DLBCL (p<0.05). At the protein level arginase 1, IL-10 and S100A12 were increased in DLBCL plasma, whereas PD-L1 expression on monocyte was increased in DLBCL compared to HD (p=0.03). Arginase 1 and IDO activities where increased in DLBCL patients. In DLBCL, IL-10 and S100A12 were detected in culture supernatants from stimulated PBMC and these molecules were decreased after CD14pos depletion (p<0.05). Finally, we defined 2 groups of DLBCL depending on M-MDSC content and analyzed the percentage of proliferating T cells after CD3/CD28 stimulation in the presence of various inhibitors or blocking antibodies (L-1MT, nor-NOHA, anti-IL-10, anti-PD-1 and anti-S100A12). In the group of patients with circulating MDSC, neutralizing IL-10, PDL-1 and S100A12 resulted in an increase of CD4 and/or CD8 T-cell proliferation.
Conclusion: In summary, we identified MDSC subsets expanded in DLBCL as well as new mechanisms of immunosuppression in DLBCL. Myeloid-dependent T-cell suppression is attributed to a release of IL-10 and S100A12 and an increase of PD-L1 expression.
Disclosures: Cartron: Roche: Consultancy , Honoraria ; GSK: Honoraria ; Celgene: Honoraria ; Sanofi: Honoraria ; Gilead: Honoraria .
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