Project description:Cross-presentation of tumor antigens by dendritic cells (DCs) is crucial to prime and (re-) stimulate CD8+ T cells. This process is important in initiating and maintaining an anti-tumor response. Here, we show that tumor presence of conventional type 1 DCs (cDC1), a subtype that excels in cross-presentation, correlates with response to neoadjuvant immune checkpoint blockade (ICB) in melanoma. This led us to hypothesize that patients failing to respond to ICB could benefit from enhanced cross-presentation of tumor antigens. We therefore established a cross-presentation assay to screen over 5,500 compounds for enhancers of DC cross-presentation using induced T cell proliferation as readout. We identified 145 enhancers, including AZD5582, an antagonist of inhibitor of apoptosis proteins (IAPs) cIAP1, cIAP2 and XIAP. AZD5582 treatment led to DC activation of the non-canonical nuclear factor kappa B (NF-kB) pathway, enhanced antigen import from endolysosomes into the cytosol and increased expression of genes involved in cross-presentation. Furthermore, it upregulated expression of CD80, CD86, MHC class II, CD70 and secretion of TNF by DCs. This enhanced DC activation and maturation program was observed also in tumor-bearing mice upon AZD5582 treatment, culminating into an increased frequency of systemic tumor antigen-specific CD8+ T cells. Our results merit further exploration of AZD5582 to increase antigen cross-presentation for improving the clinical benefit of ICB in unfavorable patients.
Project description:Cross-presentation of tumor antigens by dendritic cells (DCs) is crucial to prime and (re-) stimulate CD8+ T cells. This process is important in initiating and maintaining an anti-tumor response. Here, we show that tumor presence of conventional type 1 DCs (cDC1), a subtype that excels in cross-presentation, correlates with response to neoadjuvant immune checkpoint blockade (ICB) in melanoma. This led us to hypothesize that patients failing to respond to ICB could benefit from enhanced cross-presentation of tumor antigens. We therefore established a cross-presentation assay to screen over 5,500 compounds for enhancers of DC cross-presentation using induced T cell proliferation as readout. We identified 145 enhancers, including AZD5582, an antagonist of inhibitor of apoptosis proteins (IAPs) cIAP1, cIAP2 and XIAP. AZD5582 treatment led to DC activation of the non-canonical nuclear factor kappa B (NF-kB) pathway, enhanced antigen import from endolysosomes into the cytosol and increased expression of genes involved in cross-presentation. Furthermore, it upregulated expression of CD80, CD86, MHC class II, CD70 and secretion of TNF by DCs. This enhanced DC activation and maturation program was observed also in tumor-bearing mice upon AZD5582 treatment, culminating into an increased frequency of systemic tumor antigen-specific CD8+ T cells. Our results merit further exploration of AZD5582 to increase antigen cross-presentation for improving the clinical benefit of ICB in unfavorable patients.
Project description:Increased antigen cross-presentation but impaired cross-priming after activation of PPARγ is mediated by up-regulation of B7H1 Dendritic cells (DCs) are able to take up exogenous antigens and present antigen-derived peptides on MHC class I molecules, a process termed cross-presentation. The mannose receptor (MR), an endocytic receptor expressed on a variety of antigen-presenting cells (APCs), has been demonstrated to target soluble antigens exclusively towards cross-presentation. In this study, we investigated the role of the murine nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ), a ligand-activated transcription factor with immunomodulatory properties, in MR-mediated endocytosis and cross-presentation of the model antigen ovalbumin (OVA). We could demonstrate both in vitro and in vivo that activation of PPARγ resulted in increased MR expression, which in consequence led to enhanced MR-mediated endocytosis and elevated cross-presentation of soluble OVA. Concomitantly, activation of PPARγ in DCs induced up-regulation of the co-inhibitory molecule B7H1, which, despite enhanced cross-presentation, caused an impaired activation of naive OVA-specific CD8+ T cells and the induction of T cell tolerance. These data provide a mechanistic basis for the immunomodulatory action of PPARγ which might open new possibilities in development of therapeutical approaches aimed at the control of excessive immune responses, e.g. in T cell-mediated autoimmunity. Comparison of murine mannose receptor negative versus mannose receptor positive bone marrow-derived DCs
Project description:Increased antigen cross-presentation but impaired cross-priming after activation of PPARγ is mediated by up-regulation of B7H1 Dendritic cells (DCs) are able to take up exogenous antigens and present antigen-derived peptides on MHC class I molecules, a process termed cross-presentation. The mannose receptor (MR), an endocytic receptor expressed on a variety of antigen-presenting cells (APCs), has been demonstrated to target soluble antigens exclusively towards cross-presentation. In this study, we investigated the role of the murine nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ), a ligand-activated transcription factor with immunomodulatory properties, in MR-mediated endocytosis and cross-presentation of the model antigen ovalbumin (OVA). We could demonstrate both in vitro and in vivo that activation of PPARγ resulted in increased MR expression, which in consequence led to enhanced MR-mediated endocytosis and elevated cross-presentation of soluble OVA. Concomitantly, activation of PPARγ in DCs induced up-regulation of the co-inhibitory molecule B7H1, which, despite enhanced cross-presentation, caused an impaired activation of naive OVA-specific CD8+ T cells and the induction of T cell tolerance. These data provide a mechanistic basis for the immunomodulatory action of PPARγ which might open new possibilities in development of therapeutical approaches aimed at the control of excessive immune responses, e.g. in T cell-mediated autoimmunity.
Project description:Whether the presentation levels of the major histocompatibility complex (MHC, called the human leukocytes antigens, HLA, in humans) is limited by the availability of peptide ligands for loading or by the supply of empty MHC molecules, is a yet unresolved issue. This study aims to tackle this dilemma using large-scale immunopeptidome analyses. First, cultured cells (MCF-7) were treated with interferons, which dramatically increased presentation levels of their HLA-B molecules, much more than HLA-A and HLA-C. The differential increase in the HLA-B molecules with their bound peptides, was driven by elevated HLA synthesis levels and not by supply of peptides, since all three HLA allotypes draw peptides from the same peptide pool, which should have been affected similarly by the interferons treatment. In addition, artificial competition for peptides was created by recombinant high levels expression of soluble HLA-A*02:01 molecules, in the same MCF-7 cells and on top of their endogenous membranal HLA-A*02:01. This high level expression of the soluble HLA did not affect the endogenous membranal HLA-A*02:01 peptidomes or its cell surface presentation levels. We therefore concluded that a surplus supply of peptides is available for loading and that presentation levels are more likely limited by the supply of HLA molecules.
Project description:Assessment of mRNA expression changes in the B-lymphoblastoid cell line Awells after 6 h and 24 h of starvation-induced autophagy Keywords: ordered