Project description:Chronic viral infections and tumours are associated with CD8+ T cell exhaustion, which is characterized by high expression of inhibitory receptors such as programmed cell death protein 1 (PD-1) and impaired effector function. Understanding the molecular regulation of T cell exhaustion is critical for the development of new immunotherapies. Chronically activated T cells are maintained by precursors of exhausted T (TPEX) cells that express the transcription factor TCF1, self-renew and give rise to TCF-1– exhausted effector T (TEX) cells; this process is currently, however, poorly understood. Here, we reveal that TPEX cells are heterogenous and contain a population of CD62L+ stem-like exhausted T cells that selectively preserve long-term self-renewal capacity and multipotency of antigen-specific T cells during chronic infection. Furthermore, we show that the transcription factor c-Myb is essential for the development of CD62L+ TPEX cells, self-renewal of TPEX cells and the induction of key features of T cell exhaustion. Consequently, Myb-deficient CD8+ T cells show uninhibited cytokine production resulting in fatal immunopathology in response to chronic but not acute LCMV infection and fail to be maintained long-term. Finally, we show that c-Myb-dependent CD62L+ TPEX cells exclusively mediate T cell proliferation during PD-1 checkpoint inhibition and show enhanced antiviral properties, making them attractive targets for new immunotherapeutic strategies. Thus, our findings identify CD62L+ TPEX cells as central to the maintenance of exhausted T cell responses and reveal c-Myb as a key transcriptional orchestrator that combines two central aspects of T cell exhaustion, limitation of T cell function and long-term maintenance during chronic infection.
Project description:CD8+ T cells that respond to chronic viral infections or cancer are characterized by the expression of inhibitory receptors such as programmed cell death protein 1 (PD-1) and by the impaired production of cytokines. This state of restrained functionality-which is referred to as T cell exhaustion1,2-is maintained by precursors of exhausted T (TPEX) cells that express the transcription factor T cell factor 1 (TCF1), self-renew and give rise to TCF1- exhausted effector T cells3-6. Here we show that the long-term proliferative potential, multipotency and repopulation capacity of exhausted T cells during chronic infection are selectively preserved in a small population of transcriptionally distinct CD62L+ TPEX cells. The transcription factor MYB is not only essential for the development of CD62L+ TPEX cells and maintenance of the antiviral CD8+ T cell response, but also induces functional exhaustion and thereby prevents lethal immunopathology. Furthermore, the proliferative burst in response to PD-1 checkpoint inhibition originates exclusively from CD62L+ TPEX cells and depends on MYB. Our findings identify CD62L+ TPEX cells as a stem-like population that is central to the maintenance of long-term antiviral immunity and responsiveness to immunotherapy. Moreover, they show that MYB is a transcriptional orchestrator of two fundamental aspects of exhausted T cell responses: the downregulation of effector function and the long-term preservation of self-renewal capacity.
Project description:Chronic viral infections and tumours are associated with CD8+ T cell exhaustion, which is characterized by high expression of inhibitory receptors such as programmed cell death protein 1 (PD-1) and impaired effector function. Understanding the molecular regulation of T cell exhaustion is critical for the development of new immunotherapies. Chronically activated T cells are maintained by precursors of exhausted T (TPEX) cells that express the transcription factor TCF1, self-renew and give rise to TCF-1– exhausted effector T (TEX) cells; this process is currently, however, poorly understood. Here, we reveal that TPEX cells are heterogenous and contain a population of CD62L+ stem-like exhausted T cells that selectively preserve long-term self-renewal capacity and multipotency of antigen-specific T cells during chronic infection. Furthermore, we show that the transcription factor c-Myb is essential for the development of CD62L+ TPEX cells, self-renewal of TPEX cells and the induction of key features of T cell exhaustion. Consequently, Myb-deficient CD8+ T cells show uninhibited cytokine production resulting in fatal immunopathology in response to chronic but not acute LCMV infection and fail to be maintained long-term. Finally, we show that c-Myb-dependent CD62L+ TPEX cells exclusively mediate T cell proliferation during PD-1 checkpoint inhibition and show enhanced antiviral properties, making them attractive targets for new immunotherapeutic strategies. Thus, our findings identify CD62L+ TPEX cells as central to the maintenance of exhausted T cell responses and reveal c-Myb as a key transcriptional orchestrator that combines two central aspects of T cell exhaustion, limitation of T cell function and long-term maintenance during chronic infection.
Project description:Chronic viral infections and tumours are associated with CD8+ T cell exhaustion, which is characterized by high expression of inhibitory receptors such as programmed cell death protein 1 (PD-1) and impaired effector function. Understanding the molecular regulation of T cell exhaustion is critical for the development of new immunotherapies. Chronically activated T cells are maintained by precursors of exhausted T (TPEX) cells that express the transcription factor TCF1, self-renew and give rise to TCF-1– exhausted effector T (TEX) cells; this process is currently, however, poorly understood. Here, we reveal that TPEX cells are heterogenous and contain a population of CD62L+ stem-like exhausted T cells that selectively preserve long-term self-renewal capacity and multipotency of antigen-specific T cells during chronic infection. Furthermore, we show that the transcription factor c-Myb is essential for the development of CD62L+ TPEX cells, self-renewal of TPEX cells and the induction of key features of T cell exhaustion. Consequently, Myb-deficient CD8+ T cells show uninhibited cytokine production resulting in fatal immunopathology in response to chronic but not acute LCMV infection and fail to be maintained long-term. Finally, we show that c-Myb-dependent CD62L+ TPEX cells exclusively mediate T cell proliferation during PD-1 checkpoint inhibition and show enhanced antiviral properties, making them attractive targets for new immunotherapeutic strategies. Thus, our findings identify CD62L+ TPEX cells as central to the maintenance of exhausted T cell responses and reveal c-Myb as a key transcriptional orchestrator that combines two central aspects of T cell exhaustion, limitation of T cell function and long-term maintenance during chronic infection.
Project description:Earlier we have shown important roles of MYB in pancreatic tumor pathobiology. To better understand the role of MYB in the tumor microenvironment and identify MYB-associated secreted biomarker proteins, we conducted mass spectrometry analysis of the secretome from MYB-modulated and control pancreatic cancer cell lines. We also performed in silico analyses to determine MYB-associated biofunctions, gene networks and altered biological pathways. We further investigated the secreted proteins for their potential biomarker properties.
Project description:Most E2F-binding sites repress transcription through the recruitment of Retinoblasoma (RB) family members until the end of the G1 cell-cycle phase. Although the MYB promoter contains an E2F-binding site, its transcription is activated shortly after the exit from quiescence, before RB family members inactivation, by unknown mechanisms. We had previously uncovered a nuclear factor distinct from E2F, Myb-sp, whose DNA-binding site overlapped the E2F element and had hypothesized that this factor might overcome the transcriptional repression of MYB by E2F-RB family members. We have purified Myb-sp and discovered that Myc-associated zinc finger proteins (MAZ) are major components. We show that various MAZ isoforms are present in Myb-sp and activate transcription via the MYB-E2F element. Moreover, while forced RB or p130 expression repressed the activity of a luciferase reporter driven by the MYB-E2F element, co-expression of MAZ proteins not only reverted repression, but also activated transcription. Finally, we show that MAZ binds the MYB promoter in vivo, that its binding site is critical for MYB transactivation, and that MAZ knockdown inhibits MYB expression during the exit from quiescence. Together, these data indicate that MAZ is essential to bypass MYB promoter repression by RB family members and to induce MYB expression.
Project description:Upon antigen stimulation, the bioenergetic demands of T cells increase dramatically over the resting state. Although a role for the metabolic switch to glycolysis has been suggested to support increased anabolic activities and facilitate T cell growth and proliferation, whether cellular metabolism controls T cell lineage choices remains poorly understood. Here we report that the glycolytic pathway is actively regulated during the differentiation of inflammatory TH17 and Foxp3-expressing regulatory T cells (Treg), and controls cell fate determination. TH17 but not Treg-inducing conditions resulted in strong upregulation of the glycolytic activity and induction of glycolytic enzymes. Blocking glycolysis inhibited TH17 development while promoting Treg cell generation. Moreover, the transcription factor hypoxia-inducible factor 1a (HIF1a) was selectively expressed in TH17 cells and its induction required signaling through mTOR, a central regulator of cellular metabolism. HIF1a-dependent transcriptional program was important for mediating glycolytic activity, thereby contributing to the lineage choices between TH17 and Treg cells. Lack of HIF1a resulted in diminished TH17 development but enhanced Treg differentiation, and protected mice from autoimmune CNS inflammation. Our studies demonstrate that HIF1a-dependent glycolytic pathway orchestrates a metabolic checkpoint for the differentiation of TH17 and Treg cells. Naïve CD4 T cells from wild-type and HIF1a-deficient mice (in triplicates each group) were differentiated under TH17 conditions for 2.5 days, and RNA was analyzed by microarrays.
Project description:The MYB-NFIB gene is a driver-mutation in the majority of adenoid cystic carcinomas (ACCs) and believed to control a large number of genes involved in tumorigenesis. This experiment investigates the effects on gene expression after siRNA knock-down of MYB-NFIB and/or inhibition of IGF1R/INSR signaling in ACC cells.
Project description:Background:
* Immune-based approaches in colorectal cancer have unfortunately with the notable exception of immune checkpoint inhibition in microsatellite instable (MSI-hi) disease been largely unsuccessful. The reasons for this are unclear but no doubt relate to the fact that in advanced disease colorectal cancer appears to be less immunogenic, as evidenced by the lack of infiltrating lymphocytes with advancing T stage
* Pexa-Vec (JX-594) is a thymidine kinase gene-inactivated oncolytic vaccinia virus engineered for the expression of transgenes encoding human granulocyte- macrophage colony-stimulating factor (GM-CSF) and beta-galactosidase. Apart from the direct oncolytic activity, oncolytic viruses such as Pexa-Vec have been shown to mediate tumor cell death via the induction of innate and adaptive immune responses
* Tremelimumab is a fully human monoclonal antibody that binds to cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expressed on the surface of activated T lymphocytes and causes inhibition of B7-CTLA-4-mediated downregulation of T-cell activation. Durvalumab is a human monoclonal antibody directed against programmed death-ligand 1 (PD-L1).
* The aim of the study is to evaluate whether the anti-tumor immunity induced by Pexa-Vec oncolytic viral therapy can be enhanced by immune checkpoint inhibition.
Objective:
-To determine the safety, tolerability and feasibility of Pexa-Vec oncolytic virus in combination with immune checkpoint inhibition in patients with refractory metastatic colorectal cancer.
Eligibility:
* Histologically confirmed metastatic colorectal cancer.
* Patients must have progressed on, been intolerant of or refused prior oxaliplatin- and irinotecan-containing, fluorouracil-based, chemotherapeutic regimen and have disease that is not amenable to potentially curative resection. Patients who have a known Kirsten rat sarcoma viral oncogene homolog (KRAS) wild type tumor must have progressed, been intolerant of or refused cetuximab or panitumumab based chemotherapy.
* Patients tumors must be documented to be microsatellite-stable (MSS) either by genetic analysis or immunohistochemistry OR microsatellite-high with documented disease progression following anti-programmed cell death protein 1 (PD1)/Programmed death-ligand 1 (PDL1) therapy.
* Patients must have at least one focus of metastatic disease that is amenable to pre- and on-treatment biopsy.
* Willingness to undergo mandatory tumor biopsy.
Design:
-The proposed study is Phase I/II study of Pexa-Vec oncolytic virus at two dose levels in combination with immune checkpoint inhibition in patients with metastatic colorectal cancer.