The most common human leukemia is B-cell chronic lymphocytic leukemia (B-CLL), which is characterized by a progressive accumulation of abnormal B-lymphocytes in blood, bone marrow and secondary lymphoid organs. Typically disease progression is slow, but as the number of leukemic cells increases, they interfere with the production of other important blood cells, causing the patients to be in an immunosuppressive state. To study the basis of this immunoregulation, we used cells from the transgenic Eμ-TCL1 mouse, which spontaneously develop B-CLL due to a B-cell specific expression of the oncogene, TCL1. Previously we showed that Eμ-TCL1 CLL cells constitutively produce an anti-inflammatory cytokine, IL-10. Here we studied the role of IL-10 in CLL cell survival in vitro and the development of CLL in vivo. We found that neutralization of IL-10 using anti-IL-10 antibodies or blocking the IL-10 receptor (IL-10R) using anti-IL-10R antibodies did not affect the survival of CLL cells in vitro. On the other hand, adoptively transferred Eμ-TCL1 cells grew at a slower rate in IL-10R KO mice vs. wild type (WT) mice. There was a significant reduction in CLL cell engraftment in the spleen, bone marrow, peritoneal cavity and liver of the IL-10R KO compared to WT mice. Further studies revealed that IL-10 could be playing a role in the tumor microenvironment possibly by affecting anti-tumor immunity. This was seen by a reduction in the activation of CD8+ T cells as well as a significantly lower production of IFN-γ by CD4+ T cells purified from CLL-injected WT mice compared to those purified from CLL-injected IL-10R KO mice. Also CLL-primed IL-10R null T cells were more effective than those from similarly CLL-primed wild type mice in controlling CLL growth in immunodeficient recipient mice. These studies demonstrate that CLL cells suppress host anti-tumor immunity via IL-10 production. This led us to investigate possible mechanisms by which IL-10 is produced. We found a novel role of B-cell receptor (BCR) signaling pathway in constitutive IL-10 secretion. Inhibition of Src or Syk family kinases reduces the constitutive IL-10 production by Eμ-TCL1 cells in a dose dependent manner. We identified the transcription factor Sp1 as a novel regulator of IL-10 production by CLL cells and that it is regulated by BCR signaling via the Syk/MAPK pathway.

La communication intercellulaire est à la base de l'organisation d'ordre supérieur observée dans les tissus, les organes et l'organisme. Comprendre la communication intercellulaire et ses mécanismes sous-jacents qui sont impliqués dans le cancer est essentiel. Le microenvironnement des tumeurs du sein est composé d'une grande diversité cellulaire, telle que les cellules endothéliales, stromales ou immunitaires, qui peuvent influencer la progression tumorale ainsi que la réponse au traitement. Parmi les différentes populations de cellules immunitaires, les sous-populations de cellules dendritiques (DCs) intègrent les signaux du microenvironnement puis joue un rôle critique en orchestrant le développement d’une réponse immunitaire spécifique par activation des lymphocytes T. Cependant, les différentes fonctions de ces sous-populations et leurs interactions au sein du microenvironnement tumoral restent mal décrites. L’objectif principal de ma thèse a été de comprendre l'impact du microenvironnement tumorale du sein sur les sous-populations de DCs par analyse systémique. Nous avons utilisé le séquençage de l'ARN pour analyser systématiquement les transcriptomes des pré-DC plasmacytoïdes infiltrant les tumeurs (pDC), les populations cellulaires enrichies pour les DC classiques de type 1 (cDC1e), les DC classiques de type 2, les DC CD14+ et les monocytes-macrophages chez des patientes atteintes de cancer primitif du sein luminal et cancer du sein triple négatif. Nous avons constaté que la reprogrammation transcriptionnelle des cellules présentatrices d’antigène infiltrant la tumeur est spécifique à un sous-ensemble. Ces résultats suggèrent une interaction complexe entre l'ontogenèse et l'empreinte tissulaire dans le conditionnement de la diversité des DCs et de leur fonction dans le cancer.En second lieu, j'ai cherché à étudier les communications intercellulaires afin de comprendre comment les cellules intègrent les signaux de leur environnement. Nous avons développé ICELLNET, un outil pour reconstruire les réseaux de communication intercellulaires. Cette méthode quantitative originale, intégrant les interactions ligand-récepteur et l'expression génique spécifique à un type cellulaire, peut être appliquée automatiquement à tous profils transcriptomiques de population cellulaire, que ce soit dans divers contextes pathologiques ou d’autres domaines de la biologie. / Cell-to-cell communication is at the basis of the higher order organisation observed in tissues, organs, and organism. Understanding cell-to-cell communication, and its underlying mechanisms that drive the development of cancer is essential. Breast tumor microenvironment (TME) is composed of a great cellular diversity, such as endothelial, stromal or immune cells that can influence tumor progression as well as its response to treatment. Among the different immune cell populations, dendritic cells (DCs) subsets integrate signals from their microenvironment and are subsequently essential in orchestrating specific immune response through T cell activation. However, the differential function of these subsets, and their interactions within the TME remain poorly described. My main thesis objective was to understand the impact of the breast TME on DC subsets using systems-level analysis. We used RNA sequencing to systematically analyze the transcriptomes of tumor-infiltrating plasmacytoid pre-DCs (pDCs), cell populations enriched for type 1 classical DCs (cDC1e), type 2 classical DCs (cDC2s), CD14+DCs, and monocytes-macrophages from human primary luminal breast cancer and triple-negative breast cancer. We found that transcriptional reprogramming of tumor-infiltrating antigen-presenting cells is subset-specific. These results suggest a complex interplay between ontogeny and tissue imprinting in conditioning DC diversity and function in cancer.As a second objective, I aimed at studying the cellular communications in order to understand how cells integrate signals from their environment. I developed ICELLNET, a tool to reconstruct intercellular communication networks. This original quantitative method, integrating ligand-receptor interactions and cell type specific gene expression, can be automatically applied to any cell population level transcriptomic profile opening perspectives of application in several disease contexts and biology fields.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24487号 / 医博第4929号 / 新制||医||1063(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 上野 英樹, 教授 髙折 晃史 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Lectin-saccharide interactions are involved in many biological processes essential for the survival and proper function of multicellular organisms. C-type lectin-like receptors, predominantly expressed by cells of the innate immune system, recognize saccharide structures on microbes and also aberrant glycosylation pattern of cancer cells. The NKR-P1 receptor family was among the first natural killer (NK) receptor families that were identified, however ligands for some of members remain still elusive. Recently, publications describing N-acetylglucosamine-terminated oligosaccharide structures as possible ligands for NKR-P1 receptor have been subjects for correction/retractions after investigation of the Ethical Committee of the Institute of Microbiology, ASCR, v. v. i. and Charles University in Prague. Re-evaluation of glycodendrimer effect, particularly effect of N-acetyl-D-glucosamine octabranched dendrimer on polyamidoamine scaffold (GN8P), revealed mostly indirect role of NK cells on modulation of immune responses. Properly folded soluble recombinant rat NKR-P1A and mouse NKR-P1C lack binding activity to neoglycoproteins modified with GlcNAc-terminated structures. Moreover, new possible target cell populations (NKT cells and macrophages) for saccharide binding were identified.

La ténascine-C (TNC), protéine de la matrice extracellulaire, favorise la progression tumorale et la métastase par des mécanismes pas totalement élucidés. J’ai utilisé un nouveau modèle de progression tumorale de la glande mammaire basé sur une approche de greffe de cellules tumorales orthotopiques syngéniques et j’ai ainsi identifié la TNC comme un régulateur important de la croissance tumorale. L’expression concomitante de la TNC par les cellules de l’hôte et les cellules tumorales induit une régression de la tumeur en induisant une signature de présentation d’antigène. Cette signature a été corrélée avec une meilleure survie des patientes atteintes de cancer du sein. D’autre part, la TNC exprimée par les cellules tumorales induit également l’expression de CXCL12 au sein de la tumeur, piégeant les lymphocytes CD8+ dans des travées de matrice enrichies avec le CXCL12 lié à la TNC. L’inhibition du récepteur de CXCL12, le CXCR4 provoque une régression tumorale qui s’accompagne d’un afflux important de lymphocytes T CD8+ et d’une augmentation de la mort cellulaire au sein du lit tumorale. La séquestration des lymphocytes T cytotoxiques par la TNC dans les travées de matrice peut avoir une implication importante dans le développement et l’utilisation des nouvelles immunothérapies ciblant l’activité des cellules effectrices du système immunitaire. / The extracellular matrix molecule tenascin-C (TNC) promotes tumor progression and metastasis by poorly understood mechanisms. I used a novel breast progression model based on a syngeneic orthotopic tumor cell grafting approach and identified TNC as an important regulator of tumor growth. I document that TNC promotes the battle between tumor regression and growth, where combined expression of tumor cell- and host-derived TNC induces tumor cell rejection. Tumor cell-derived TNC may elicit regression by induction of an antigen presenting signature (APS) expressed by the host, which correlates with better breast cancer patient survival. Tumor-cell derived TNC also triggers CXCL12 expression, thereby causing trapping of CD8+ T cells in the surrounding TNC matrix tracks. TNC binds CXCL12, and combined TNC/CXCL12 attracts and immobilizes CD8+ T cells. Inhibition of the CXCL12 receptor CXCR4 causes tumor regression that is accompanied by massive infiltration of CD8+ T cells and cell death inside the tumor cell nests. Altogether,TNC-triggered CXCL12 signaling may dampen CD8+ T cell function where physical trapping of CD8+ T cells in the TNC matrix may have implications for immune cell therapies. Our results and new tumor model, offer novel opportunities for preclinical cancer research and cancer patient therapy, by triggering the “good” and blocking the “bad” actions of TNC. In particular, overcoming the immune suppressive action of TNC, through inhibition of CXCR4, could be a useful approach.

Les syndromes neurologiques paranéoplasiques (SNP) sont des maladies neurologiques rares, associés à une réponse immunitaire efficace contre un cancer sous-jacent exprimant un antigène également exprimé par des cellules du système nerveux central (SNC). Le cancer déclenche alors une réponse auto-immune secondaire qui provoque la destruction des cellules du SNC. Certains travaux récents suggèrent que l'immunité à médiation cellulaire associée à des auto-anticorps reconnaissant des antigènes intracellulaires pourrait jouer un rôle majeur, bien qu'encore mal compris, dans la physiopathologie des SNP. Les exemples de SNP les plus représentatifs sont le syndrome Hu, qui conduit à la perte de diverses populations de neurones du SNC et l'ataxie cérébelleuse subaiguë (PCD en anglais, pour Paraneoplastic Cerebellar Degeneration), caractérisée par la perte sélective des cellules de Purkinje du cervelet. Alors que le syndrome Hu se développe en général chez des patients présentant des tumeurs du poumon à petites cellules qui expriment l'antigène HuD spécifique des neurones, la majorité des patients souffrant de PCD présente un cancer gynécologique qui exprime la protéine CDR2, également exprimée dans les cellules de Purkinje. Afin de mieux cerner la physiopathologie des SNP et de tester l'implication de l'immunité cellulaire, notamment des lymphocytes T, nous avons durant ma thèse développé et analysé deux modèles murins, l'un pour le syndrome Hu et l'autre pour la PCD. Ces modèles reposent sur l'utilisation de souches de souris génétiquement modifiées : la souris CamK-HA, qui exprime l'hémagglutinine (HA) du virus de la grippe dans la plupart de ses neurones du SNC et la souris L7-HA dans laquelle la protéine HA est exprimée exclusivement par les cellules de Purkinje du cervelet. Dans ces souris, une réponse anti-tumorale est provoquée par l'injection de cellules tumorales 4T1 exprimant HA (4T1-HA). Afin le faciliter le suivi des réponses cellulaires contre l'antigène HA, nous avons injecté des lymphocutes T CD4+ et/ou T CD8+ naïfs isolées à partir de souris transgéniques pour des récepteurs de lymphocytes T spécifiques de HA. Nos résultats montrent que seul le transfert in vivo des cellules tumorales 4T1-HA, et non celui des cellules 4T1 témoins, peut conduire à l'activation, la prolifération et la différentiation des deux types de lymphocytes T spécifiques pour l'antigène HA. De plus, nous avons observé que les populations de lymphocytes T CD4+ et CD8+ sont toutes deux requises, non seulement pour une réponse anti-tumorale efficace, mais aussi pour le déclenchement d'une réaction auto-immune collatérale chez la souris CamK-HA. Enfin, nous avons montré qu'il était nécessaire d'injecter en parallèle des anticorps contre le récepteur inhibiteur CTLA-4 chez la souris L7-HA, afin de permettre la migration des lymphocytes T spécifiques de HA dans le cervelet. Chez ces souris L7-HA, nous avons en outre démontré que les lymphocytes T CD8+ cytotoxiques sont les effecteurs principaux de la maladie. Ces nouveaux modèles murins représentent donc des outils précieux pour une meilleure compréhension des mécanismes moléculaires responsables du développement des SNP. De plus, ils pourraient permettre de tester et de valider de nouvelles approches thérapeutiques visant à bloquer la pénétration dans le SNC d'effecteurs immunitaires potentiellement pathogènes, tout en préservant l'efficacité de la réponse anti-tumorale en périphérie. / Paraneoplastic neurological disorders (PNDs) are rare human autoimmune diseases that mostly affect the central nervous system (CNS). They are triggered by an efficient immune response against a neural self-antigen that is ectopically expressed in neoplastic tumor cells and naturally expressed in CNS cells. Due to this shared antigenic expression, the immune system reacts not only to tumor cells but also to neural cells resulting in neurological damage. Growing data point to a major role of cell-mediated immunity in PNDs associated to autoantibodies against intracellular proteins. However, its precise contribution in the pathogenesis remains unclear. Two illustrative examples of possibly cell-mediated PNDs are the Hu-syndrome, characterized by inflammation and widespread los of neurons, and paraneoplastic cerebellar degeneration (PCD), characterized by the selective loss of Purkinje cells. PCD develops mostly in patients with gynecologic carcinomas that express the Purkinje neuron-specific CDR2 protein whereas most patients with the Hu-syndrome harbor small cell lung cancer expressing the neuron-specific protein HuD. In this context, our study aimed to investigate the impact of anti-tumor cellular immune responses in the development of these PNDs. To this end, we developed two animal models mimicking the Hu-syndrome and PCD. We used a tumor cell line expressing the hemagglutinin (HA) of influenza virus to induce an anti-tumor response in CamK-HA mice, which express HA in CNS neurons and L7-HA mice, which express HA only in cerebellar Purkinje neurons. To promote and track the T cell response against the HA antigen, naïve HA-specific CD8+ and/or CD4+ T cells, originating from TCR-transgenic animals, were transferred into these mice. We demonstrate that HA-expressing tumors, but not control tumors, induce in vivo activation, proliferation and differentiation of naïve HA-specific CD4+ and CD8+ T cells into effector cells. Moreover, the collaboration between these two T cell subsets was needed to control tumor growth and induce CNS inflammation in CamK-HA mice. In L7-HA mice the additional injection of the antibody against the inhibitory receptor CTLA-4 was necessary to allow T cells to enter the cerebellum to cause inflammation and the subsequent destruction of Purkinje neurons. Furthermore, in L7-HA mice we demonstrate that cytotoxic CD8+ T cells are the main effectors driving the disease. Thus, these two new mouse models provide further insights into the cellular mechanisms of PND whereby a potent anti-tumor immunity triggers a cancer-associated autoimmune disease, and may therefore help to develop new therapeutic strategies against PND.

Cancer remains the second most common cause of death worldwide affecting around 10 million patients every year. Among the therapeutic options, chemotherapeutic drugs are widely used but often associated with side effects. In addition, toxicity against immune cells may hamper anti-tumor immune responses. Some chemotherapeutic drugs, however, preserve immune functions and some can even stimulate anti-tumor immune responses through the induction of immunogenic cell death (ICD) rather than apoptosis. ICD stimulates the immune system by several mechanisms including the release of damage-associated molecular patterns (DAMPs) from dying cells. In this review, we will discuss the consequences of inducing two recently characterized forms of ICD, i.e., pyroptosis and necroptosis, in the tumor microenvironment (TME) and the perspectives they may offer to increase the immunogenicity of the so-called cold tumors and to stimulate effective anti-tumor immune responses.

Glioblastoma (GBM) is the most common and deadliest of the malignant primary brain tumors in humans, with a reported 5-year survival rate of only 6.8% despite years of extensive research. Failure to improve local tumor control rates and overall patient outcome is attributed to GBM's inherent therapeutic resistance. Marked heterogeneity, extensive local invasion within the brain parenchyma, and profound immunosuppression within the tumor microenvironment (TME) are some of the unique features that drive GBM therapeutic resistance. Furthermore, tumor cells are sequestered behind the blood-brain barrier (BBB), limiting delivery of effective therapeutics and immune cell infiltration into the local tumor. Electroporation-based therapies, such as irreversible electroporation (IRE) and second generation, high-frequency IRE (H-FIRE) represent attractive alternative approaches to standard GBM therapy given their ability to induce transient BBB disruption (BBBD), achieve non-thermal tumor cell ablation and stimulate local and systemic anti-tumor immune responses without significant morbidity. The following work explores the use of H-FIRE to overcome GBM-induced therapeutic resistance and improve treatment success. Chapter 1 opens with an overview of GBM and known barriers to treatment success. Here, we emphasize the utility of spontaneous canine gliomas as an ideal translational model for investigations into novel treatment approaches. Chapter 2 introduces novel ablation methods (i.e. IRE/H-FIRE) capable of targeting treatment-resistant cancer stem cells. The focus of Chapter 3 is to highlight IRE applications in a variety of spontaneous tumor types. In Chapter 4, we investigate the feasibility and local immunologic response of percutaneous H-FIRE for treatment of primary liver tumors using a spontaneous canine hepatocellular carcinoma (HCC) model. In chapter 5, we characterize the mechanisms of H-FIRE-mediated BBBD in an in vivo healthy rodent model. In Chapter 6, we characterize the local and systemic immune responses to intracranial H-FIRE in rodent and canine glioma models to enhance the translational value of our work. Collectively, our work demonstrates the potential for H-FIRE to overcome therapeutic resistance in GBM, thereby supporting its use as a novel, alternative treatment approach to standard therapy. / Doctor of Philosophy / Glioblastoma (GBM) is the most common and deadliest form of primary brain cancer in humans, with only 6.8% of people surviving 5-years after their diagnosis. GBM is characterized by a number of unique features that make it resistant to standard treatments, such as surgery, radiation and chemotherapy. Examples include: (1) extensive invasion of tumor cells into the brain, making complete removal via surgery very difficult; (2) tumor cells are protected by a structure called the blood-brain barrier (BBB), which restricts the entry of most drugs (i.e. chemotherapy) and many immune cells, into the brain, thereby preventing them from reaching tumor cells; (3) tumor cells produce substances that block the immune system from being able to detect the tumor itself, which allows it to continue to grow undetected. High-frequency irreversible electroporation (H-FIRE) represents a new approach for the treatment of GBM. H-FIRE uses electric pulses to temporarily or permanently injure cell membranes without the use of heat, which allows for very precise treatment. The following work explores the ways in which H-FIRE can interfere with specific GBM features that drive its resistance to treatment. Here, we demonstrate that H-FIRE is capable of temporarily disrupting the BBB and characterize the mechanisms by which this occurs. This allows for drugs and immune cells within the blood to enter the brain and access the tumor cells, particularly those extending beyond the visible tumor mass and invading the brain. We also illustrate the potential for H-FIRE treatment within the brain to stimulate local and systemic immune responses by causing the release of proteins from injured cells. Similar to a vaccine, these proteins are recognized by the immune system, which becomes primed to help fight off cancer cells within the body. The end result is an anti-tumor immune response. Collectively, this work supports the use of H-FIRE as an alternative treatment approach to standard therapy for GBM given its potential to overcome certain causes of treatment resistance.

The goal of this body of research was to elucidate the mechanism by which CD4+ T cells provide help for CD8+ cytotoxic T lymphocyte (CTL) responses in different immunization types. The establishment of diseases, such as chronic infections and cancers, is attributed to severe loss of or dysfunctions of CD4+ T cells. Even in acute infections, CD4+ T cell deficiency leads to poor memory responses. While the role of CD4+ T cells is being increasingly appreciated in these diseases, the timing and nature of CD4+ T help and associated molecular mechanisms are not completely understood. Growing evidence suggests that, depending on the type of infections or immunizations, the requirements of CD4+ T cells can vary for optimal CD8+ CTL responses. In order to understand the modulatory effects of CD4+ T cells for optimal CD8+ CTL responses, two distinct immunization types were chosen. These include: 1) non-inflammatory dendritic cell (DC) immunization, which fails to provide inflammatory/danger signals; and 2) inflammatory adenovirus (AdV) immunization, which provides profound inflammatory/danger signals. This allowed us to study CD4+ T cell’s participation under different inflammatory conditions. The studies described in Chapters 2 and 3 of this thesis were performed to further understand the concept of how CD4+ T cells mediate optimal CD8+ CTL responses. This has been called the “new dynamic model of CD4+ T helper – antigen (Ag)-presenting cells (Th-APCs),” proposed in 2005 by our laboratory. The study described in Chapter 2 shows that Th-APCs participate not only in augmenting CTL-mediated immune responses, perhaps during early phase, but also in regulating cellular immunity, perhaps during a later phase. Through enhanced IL-2, CD80 and CD40L singnaling, and weaker peptideMHC I (pMHC) signaling, Th-APCs stimulated naïve CD8+ T cells to differentiate into effector CTLs, capable of developing into, central memory CTLs. Th-APC-stimulated CD4+ T cells behaved like Th cells in function, augmenting the overall magnitude of CTL responses. In contrast, Th-APCs were able to kill DCs and other Th-APCs, predominantly through perforin-mediated pathway. The experiments described in Chapter 3 revealed a novel co-operative role of cognate Th-CTL interactions, contrary to previously known immune-regulatory mechanisms among Th-Th or CTL-CTL interactions. In our experiments, Th cells, via CD40L, IL-2, and acquired pMHC-I signaling, enhanced CTL survival and transition into functional memory CTLs. Moreover, RT-PCR, flow cytometry and western blot analysis demonstrate that increased survival of Th cell-helped CTLs is matched with enhanced Akt1/NF-κB activation, down-regulation of FasL and TRAIL, and altered expression profiles with up-regulation of prosurvival (Bcl-2) and down-regulation of proapoptotic (NFATc1, Bcl-10, Casp-3, Casp-4, Casp-7) genes/ molecules. Finally, helped CTLs were also able to induce protection against highly metastasizing tumor challenge, explaining why memory CTLs generated under cognate Th1’s help show survival and recall advantages. The studies in Chapter 4 showed how the precursor frequency (PF) of CD8+ T cells impacts CD4+ T helper requirements for functional CTL responses. At endogenous PF, CD4+ T helper signals were necessary for both primary and memory CTL responses. At increased PF, CD4+ T help, and its CD40L but not IL-2 signal became dispensable for primary CTL responses. In contrast, memory CTL responses required CD4+ T cell signals, largely in the form of IL-2 and CD40L. Thus, these results could impact the development of novel immunotherapy against cancers, since their efficacy would be determined in part by CD4+ T help and CD8+ T cell PF. Finally, the study showed the importance of CD4+ T cells for multiple phases of AdV transgene product-specific CTL responses. These include: a) cognate CD4+ T cells enhanced CTL responses via IL-2 and CD40L signaling during primary, maintenance and memory phases; b) polyclonal CD4+ T environment enhanced the survival of AdV-specific CTL survival, partially explaining protracted CTL contraction phase; and c) during the recall phase, the CD4+ T environment, particularly memory CD4+ T cells, considerably enhanced not only helped, but also unhelped, memory CTL expansion. Thus, these results suggest the participation of both cognate and polyclonal CD4+ T cells for multiple phases of AdV-specific CTLs. Taken together, the current work delineated the critical roles of CD4+ T cells in different stages of CTL responses and in the development of anti-tumor immunity. The results presented here will significantly advance our current understanding of immunity to cancers, autoimmunity and chronic infections, since pathogenesis of these diseases is largely determined by CD4+ T helper functions. As most immunization procedures use the principle that is based on functions of memory cells, the knowledge gained from this work will also have a major impact on designing vaccines against intractable diseases, including cancers and chronic infections. Moreover, in advanced tumors, vaccines developed using this knowledge may act synergistically with other cancer treatments such as irradiation, chemotherapy and microsurgery, minimizing their side effects and prolonging the lives of patients.

Serous epithelial ovarian cancer (EOC) is a potent suppressor of the immune defense. Here, we studied interactions between EOC and the immune system that lead to escape from tumor immune surveillance. We explored: 1) tumor escape from cytotoxicity by exosome-mediated modulation of the NK-cell receptors NKG2D and DNAM-1; 2) cytokine mRNA profiles in the EOC microenvironment and peripheral blood and their role in the suppression of the anti-tumor immune responses; 3) expression of long non-coding (lnc) RNAs in EOC tumors and exosomes. We found that EOC-secreted exosomes carried MICA/B and ULBP1-3, ligands of NKG2D, and could downregulate the NKG2D receptor and impair NKG2D-mediated cytotoxicity. In contrast, the DNAM-1 receptor ligands PVR and nectin-2 were seldom found in exosomes and were not associated with the exosomal membrane leaving the DNAM-1 receptor-mediated cytotoxicity intact. We compared cytokine mRNA expression in the tumor microenvironment and in immune cells of peripheral blood in EOC patients and patients with benign ovarian conditions. EOC patients were unable to mount an IFN-gamma mRNA response needed for tumor cell elimination. Instead, there was a significant up-regulation of inflammation and immune suppression i.e. responses promoting tumorigenesis and T-regulatory cell priming that suppress anti-tumor immunity. In addition, we studied lncRNAs in tissues and sera exosomes from EOC and benign ovarian conditions aiming to assess the lncRNA(s) expression profile and look for lncRNA(s) as possible marker(s) for early diagnosis. We found a deregulated lncRNAs expression in EOC tissues that correlated well with the lncRNAs expression in exosomes. Candidate lncRNAs with the highest expression and abundance were suggested for evaluation as EOC diagnostic markers in a future large cohort study. Our studies of EOC tissue and EOC exosomes highlight the immunosuppressive tumor microenvironment and the complex tumor exosome-mediated network of immunosuppressive mechanisms, and provide a mechanistic explanation of the observation that NKG2D-mediated cytotoxicity does not function in EOC patients and is partially replaced by the accessory DNAM-1 dependent cytotoxic pathway. The deregulated lncRNAs expression in EOC tissues and exosomes might serve for diagnostic purposes but could also be a potential risk of spreading tumor-derived lncRNAs in EOC exosomes to recipient cells throughout the body.