none

Myeloid-derived suppressor cells (MDSC), emerging during tumor growth or chronic inflammation play a critical role in regulating T cell function. However, mechanisms governing the generation of these cells remain unclear, and need to be further defined. Using a DSS-induced colitis and recovery model, we characterized the dynamic changes within myeloid compartments and the emergence of MDSC during active and resolution phases of inflammation. We show that the immature myeloid compartment expands in bone marrow (BM) specifically at the resolution phase of inflammation during colitis transition to recovery. Additionally, we found enhanced levels of IL-17 in the serum of colitis mice tightly correlates with expansion of the IMC compartment, and is likely the factor responsible for expansion of these cells. Our study also determined that the expanded population of myeloid cells underwent a functional reprogramming event. In particular, two major functional changes occurred when colitic mice were allowed to recover: 1) CD11b+Gr-1+ myeloid cells in bone marrow and spleen acquired T cell suppressive functions, and 2) acquired the ability to enter into circulation from BM, confirming previously reported characteristics of MDSC. Additionally, we determined that acquired migratory capability in the low density myeloid cells isolated from resolution time points was due to enhanced surface expression of chemokine receptor CXCR2. Furthermore, we determined that after mobilization of MDSC from the bone marrow, these cells collected in the T cell-rich spleens, where they effectively functioned to suppress T cell proliferation. Through these acquired functions, our study determines a protective role for MDSC during the recovery phase of post-acute inflammation during persistent DSS-induced colitis.

Sepsis-induced myeloid-derived suppressor cells (MDSCs) contribute to immunosuppression associated with sepsis. We reported that the CCAAT enhancer-binding protein C/EBPβ activates microRNA (miR)-21 and miR-181b expressions, which induce transcription factor NFI-A to support the generation and expansion of MDSCs in the bone marrow and spleens of septic mice. Here, using a conditional knockout mouse model lacking C/EBPβ in the myeloid lineage, we find that without C/EBPβ, myeloid progenitor cells could not express miR-21 or miR-181b, and ectopic expression of C/EBPβ in the C/EBPβ-deficient myeloid progenitors activated the expression of the two miRNAs. Moreover, C/EBPβ-reconstituted myeloid cells expressed IL-10 and reduced T cell proliferation and function, similar to control MDSCs that express C/EBPβ. Exogenous expression of miR-21 and miR-181b in the C/EBPβ-deficient myeloid progenitors from septic mice produced similar results. Notably, NFI-A-dependent transactivation of NF-kB MDSC generating pathway was reversed in the C/EBPβ-deficient myeloid progenitors from septic mice. Together, these results support that decreasing C/EBPβ expression prevents MDSC generation and decreases immunosuppression in septic mice, providing a target for sepsis treatment.

Myeloid-derived suppressor cells (MDSCs) contribute to high mortality rates during sepsis, but how sepsis induces MDSCs is unclear. Previously we reported that microRNA (miR)-21 and miR-181b reprogram MDSCs in septic mice by increasing levels of DNA binding transcription factor, nuclear factor 1 (NFI-A). Here, we provide evidence that miR-21 and miR-181b stabilize NFI-A mRNA and increase NFI-A protein levels by recruiting RNA-binding proteins HuR and Ago1 to its 3′ untranslated region (3′UTR). We also find that the NFI-A GU-rich element (GRE)-binding protein CUGBP1 counters miR-21 and miR-181b dependent NFI-A mRNA stabilization and decreases protein production by replacing 3′UTR bound Ago1 with Ago2. We confirmed the miR-21 and miR-181b dependent reprogramming pathway in MDSCs transfected with a luciferase reporter construct containing an NFI-A 3′UTR fragment with point mutations in the miRNA binding sites. These results suggest that targeting NFI-A in MDSCs during sepsis may enhance resistance to uncontrolled infection.

No description available.

L’oncologie actuelle est encore confrontée à la résistance et à la progression rapide des cancers. Les mécanismes de résistance intrinsèque développés par les cellules tumorales peuvent compromettre l’efficacité des chimiothérapies et des immunothérapies. Il est maintenant admis que l’état de la réponse immunitaire de l’hôte détermine en partie l’issue thérapeutique des patients. L’objectif de notre équipe de recherche est donc de caractériser cette réponse et d’étudier l’impact des thérapies conventionnelles sur celle-ci dans le but d’identifier les mécanismes liés à un échappement futur de la tumeur. Dans ce contexte, nous avons montré qu’une chimiothérapie (5-FU, oxaliplatine, anti-VEGF (« Vascular Endothelium Growth Factor » : FOLFOX-bevacizumab) provoque chez certains patients une chute des gMDSC (cellules myéloïdes immunosuppressives granulocytaires) périphériques qui est associée à une meilleure réponse thérapeutique. Comme chez la souris, cet effet sur les gMDSC provoque néanmoins une élévation des Th17, une population pro-angiogénique, qui limite l’efficacité de la chimiothérapie. La suite de notre travail a eu pour objectif de tester l’effet « anti-Th17 » de l’activation de l’histone désacétylase SIRT1. SIRT1 est une enzyme capable de perturber l’acétylation de STAT3, un facteur essentiel à la différenciation des Th17. Nous avons montré que l’utilisation d’agonistes pharmacologiques de SIRT1 (resvératrol, SRT1720, metformine) inhibe la polarisation des Th17 par la désacétylation de STAT3 et que cet effet permet de limiter la croissance tumorale dans un modèle de cancer colique et de mélanome chez la souris (B16F10, CT26). Nous avons validé ce concept chez l’homme, ce qui suggère qu’il est possible de cibler les Th17 par cette stratégie en complément de la chimiothérapie. Le dernier volet de ce travail est consacré à la comparaison du profil immunologique périphérique de volontaires sains à celui d’une cohorte prospective de cancers bronchiques non à petites cellules. Cette étude nous a permis de mettre en lumière les altérations immunitaires induites par la tumeur et de lier ces altérations à la réponse au nivolumab (anti-PD-1). Un premier modèle prédictif de réponse a pu être généré grâce aux données d’un panel d’analyse des cellules myéloïdes. Ce modèle révèle une fois encore que les cellules gMDSC ont un rôle prédictif défavorable, alors que les populations présentatrices d’antigènes (cellules dendritiques et monocytes) exprimant PD-L1 ont un bon rôle prédictif. Les données présentées dans cette partie sont préliminaires et devront être confirmées avec la cohorte de validation qui est en cours d’inclusion. L’ensemble de ce travail a permis de montrer qu’il est essentiel de cibler spécifiquement les cellules myéloïdes immunosuppressives et les Th17 pour favoriser l’efficacité des chimiothérapies et de l’immunothérapie dans le cancer. / Actual oncology is still facing resistance and rapid progression of cancer. Intrinsic resistance mechanisms developed by tumor cells determine chemotherapy and immunotherapy efficacy. It is now recognized that the host immune response status is in part implicated in the therapeutic outcome of patients. The aim of our research team is to characterize this response and to study the impact of therapies in order to identify the mechanisms associated with future exhaust of the tumor. In this context, we have shown that chemotherapy (5-FU, oxaliplatin, anti-VEGF: FOLFOX-bevacizumab) in some patients causes a drop in devices gMDSC (granulocytic myeloid derived suppressive cells) that is associated with better therapeutic response. Nevertheless, as in mice, this effect on gMDSC causes an elevation of Th17, a pro-angiogenic population, which limits the effectiveness of chemotherapy. The result of our work was aimed to test the effect "anti-Th17" activating SIRT1 deacetylase histone. SIRT1 is an enzyme capable of disrupting the acetylation of STAT3, a key factor in the differentiation of Th17. We have shown that by using pharmacological agonists SIRT1 (resveratrol, SRT1720, metformin) inhibits Th17 polarization by deacetylation of STAT3 and that this effect can limit tumor growth in colorectal and melanoma murine models (B16F10, CT26). We validated this concept in humans, suggesting that it is possible to target Th17 cells by this strategy in addition to chemotherapy. The final component of this work is devoted to the comparison of peripheral immunological profile of healthy volunteers to a prospective cohort of non-small cell lung cancer. This study has allowed us to highlight the immune alterations induced by the tumor and to link these changes in response to nivolumab (anti-PD-1). A first response predictive model could be generated using data from a panel analysis of myeloid cells. This model proves once again that gMDSC have a negative predictive role, while antigen presenting (dendritic cells and monocytes) expressing PD-L1 has a good predictive role. Data presented in this section are preliminary and must be confirmed with the validation cohort that is currently included. All of this work has shown that it is essential to specifically target immunosuppressive myeloid cells and Th17 to promote the efficacy of chemotherapy and immunotherapy in cancer.

Selon une étude précédente, une limitation à l'efficacité anticancéreuse du 5-Fluorouracile (5-FU) repose sur la sécrétion d'IL-1β par des cellules myéloïdes immunosuppressives (MDSC). La libération d'IL-1β mature provient de l'activation de NLRP3 induite par le 5- FU et de l’augmentation de l’activité de la caspase-1 dans les MDSC, qui favorise la reprise de la croissance tumorale chez des souris traitées avec 5-FU. L'acide docosahexaénoïque (DHA) appartient à la famille des acides gras oméga-3 et possède des propriétés anticancéreuses et anti-inflammatoires qui pourraient améliorer la chimiothérapie à base de 5-FU. Dans ces travaux, nous démontrons que le DHA inhibe la sécrétion d'IL 1β induite par le 5 FU dans une lignée cellulaire de MDSC (MSC-2). Chez des souris porteuses de tumeurs traitées par 5 FU, nous avons montré qu'un régime alimentaire enrichi en DHA réduit la concentration d'IL 1β circulante et la récidive tumorale après une injection de 5 FU. Le traitement par 5 FU conduit à l'activation de JNK dans les MDSC et l'inhibiteur de JNK SP600125 diminue la sécrétion d’IL-1β. De plus, le DHA est capable de contrecarrer l'activation de JNK induite par 5-FU dans les MDSC, entraînant la chute de la libération de l’IL 1β. De plus, nous avons montré que la supplémentation en DHA dans les MDSC exposées au 5 FU diminuait l’activité de la caspase-1 ainsi que la modification des interactions entre NLRP3 et la caspase-1, ASC ou β-arrestine-2. De manière inattendue, la régulation de l'activité de la caspase-1 par le DHA était indépendante de JNK, ce qui suggère que le DHA pourrait contrôler la sécrétion de l’IL 1β par le biais de l'inflammasome NLRP3 et de la voie JNK. Enfin, nous avons trouvé une corrélation négative entre la teneur en DHA dans le plasma et l'induction du niveau d'IL 1β ou de la caspase-1 dans le sang de patients traités par chimiothérapie à base de 5-FU.L’ensemble de ces données fournissent de nouvelles informations sur la régulation de la sécrétion de l’IL-1β par le DHA et son bénéfice potentiel dans la chimiothérapie à base de 5-FU. / A limitation to 5-Fluorouracil (5-FU) anti-cancer efficacy relies on the secretion of IL-1β by myeloid-derived suppressor cells (MDSC) according to a previous pre-clinical report. The release of mature IL-1β originates from 5 FU mediated NLRP3 activation with increased caspase-1 activity in MDSC and sustains tumor growth recovery in 5 FU treated mice. Docosahexaenoic acid (DHA) belongs to omega-3 fatty acid family and harbors both anti cancer and anti inflammatory properties which might could improve 5 FU chemotherapy. Here, we demonstrate that DHA inhibits 5 FU induced IL 1β secretion produced by a MDSC cell line (MSC-2). In tumor-bearing mice treated with 5 FU, we showed that a DHA enriched diet reduces circulating IL 1β concentration and tumor recurrence after 5 FU injection. 5 FU treatment led to JNK activation in MDSC and JNK inhibitor SP600125 decreased IL 1β secretion. Moreover, DHA was able to counteract 5 FU mediated JNK activation in MDSC leading to the drop of IL 1β release. In addition, we showed that DHA supplementation in 5 FU exposed MDSC decreases caspase-1 activity along with a modification of the interactions between NLRP3 and caspase-1, ASC or β arrestin-2. Unexpectedly, the regulation of caspase-1 activity by DHA was independent of JNK which suggests that DHA could control IL 1β secretion through both NLRP3 inflammasome and JNK pathway. Interestingly, we found a negative correlation between DHA content in plasma and the induction of circulating IL 1β level or caspase-1 activity in patients treated with 5 FU based chemotherapy.Together, these data provide new insights on the regulation of IL 1β secretion by DHA and its potential benefit in 5-FU based chemotherapy.

Le système immunitaire joue un double rôle dans le cancer : il peut non seulement supprimer la croissance tumorale en détruisant les cellules cancéreuses, mais aussi promouvoir la progression de la tumeur en sélectionnant les cellules tumorales ou en créant un microenvironnement tumoral immunosuppresseur. Notre idée principale est de développer des stratégies pour mieux comprendre l’immunologie du cancer colique.Au cours de ma thèse, je me suis tout d’abord intéressée à une population du système immunitaire : les MDSC (Myeloïd Derived Suppressor Cells). Nous avons exploré des stratégies pour réduire le nombre de ces cellules au cours de la croissance tumorale. Nous avons pu découvrir que de petites doses de 5 fluorouracil sont capables d’induire spécifiquement une mort par apoptose des cellules myéloïdes suppressives. Nous avons ainsi caractérisé un effet immunologique positif nouveau du 5-fluorouracil. Cet effet immunologique contribue à l’effet antitumoral du 5-fluorouracil chez la souris. Dans une deuxième partie nous avons étudié le rôle pronostic des infiltrats immunitaires dans une série de patients présentant un cancer du côlon avec des métastases hépatiques. Nous avons étudié le rôle pronostic des infiltrats en cellules CD8, CD45R0 et Foxp3. Nous avons mis en évidence que la présence d’un fort infiltrat en cellules CD45RO et Foxp3 est un facteur de bon pronostic. L’association des 2 marqueurs permet de définir 3 groupes pronostics et ainsi d’individualiser un groupe de mauvais pronostic ne bénéficiant probablement pas de la chirurgie hépatique. / Immune system plays a dual role in cancer: it can not only suppress tumor growth by destroying cancer cells, but also promote tumor progression by selecting immunoresistant tumor cells or by establishing an immunosuppressive microenvironment. Our main objective is to foster on the context of immune response in colon cancer settingDuring my thesis, I focused on one population of the immunosuppressive cells immune system: MDSC (myeloid derived suppressor cells). In this work, we explored strategies to reduce the number of these cells during tumor growth. We have discovered that small doses of 5 Fluorouracil are able to specifically induce apoptotic death of MDSC. We have characterized a novel positive immunological effect of 5-fluororuracil. This immunological effect contributes to the antitumor effect of 5-fluorouracil in mice. In the second part we investigated the prognostic role of immune infiltrates in a series of colon cancers with liver metastases. We investigated the prognostic role of tumor infiltrates, by CD8, CD45R0 and Foxp3 cells. We found that the presence of a strong infiltrate of tumors by CD45RO and Foxp3 cells is a factor of good prognosis. The combination of the two markers could be used to define three prognostic groups and underline a poor prognosis group which may not benefit of liver surgery.

Mast cells respond to a variety of signals, are associated with both increased inflammation and regulation of the immune response, and are able to interact with a variety of hematopoietic and non-hematopoietic cells. The majority of the work that highlights mast cell pleiotropic abilities has been completed in murine models. Though these models have significantly advanced our understanding of what mast cells can do, they cannot inform us as to what mast cells actually do in human beings. The goal of this dissertation is to assess fully mature, primary human mast cell function beyond the well-defined type 1 hypersensitivity function and place mature human mast cells in the context of interactions with other immune cells. The first project addresses the ability of IFNγ, a historically Th1 associated cytokine, to dramatically alter mast cell phenotype. In particular, IFNγ stimulation allows mast cells to act as antigen presenting cells to CD4+ T cells. The second project describes and addresses the T cell suppressive function of myeloid derived suppressor cells in Mastocytosis, a disease of clonal mast cells.

Mounting evidence supports that sepsis-associated immunosuppression increases mortality. As potential contributors to poor sepsis outcomes, myeloid-derived suppressor cells, which are Gr1+ CD11b+ innate-immune cell progenitors unable to differentiate and possess suppressive activities, expand dramatically in septic mice by a process requiring increased microRNA-21 and microRNA-181b expression. The inhibition of these microRNAs in vivo in septic mice restores Gr1+ CD11b+ cell differentiation and maturation and improves survival. Here, we show that during sepsis-induced generation of myeloid-derived suppressor cells, transcription factor nuclear factor 1 A type represses cyclin-dependent kinase inhibitor p21 to arrest differentiation of Gr1+ CD11b+ cells. Our findings include the following: 1) Gr1+ CD11b+ myeloid cells from late septic mice genetically lacking nuclear factor 1 A type cannot suppress CD4+ T cell proliferation and activation; 2) the reconstitution of nuclear factor 1 A type in microRNA-21 and microRNA-181b-depleted Gr1+ CD11b+ myeloidderived suppressor cells inhibits cyclin-dependent kinase inhibitor p21 and restores the immunesuppressor phenotype; 3) ex vivo nuclear factor 1 A type knockdown in Gr1+ CD11b+ myeloid-derived suppressor cells from late septic mice restores cyclindependent kinase inhibitor p21 expression and promotes monocyte and dendritic cell differentiation; and 4) ectopic nuclear factor 1 A type expression in normal Gr1+ CD11b+ cells generates an immunosuppressive phenotype. We suggest that therapeutically targeting nuclear factor 1 A type during late sepsis might improve survival.