Project description:Intratumoral microglia and MΦ constitute up to 70% of the tumor mass of high-grade gliomas (HGG) with profound impact on hallmarks of malignancy such as angiogenesis and immunosuppression. The dynamics and functional states of intratumoral myeloid cells during tumor progression and the molecular mechanisms controlling them are poorly understood. Here we define homeostatic and antigen-presenting myeloid cellular states in experimental and human HGG by longitudinal single-cell RNA-sequencing and combined transcriptome and proteome profiling. During glioma progression, myeloid cells gradually shift from a homeostatic to a tumor-associated effector state. We show that these dynamics are under strict control by early changes in resident microglia and the tumor genotype: In gliomas with mutations in isocitrate dehydrogenase (IDH), a disease-defining driver mutation, differentiation of invaded myeloid cells was blocked resulting in an immature, immunosuppressive phenotype. In late-stage IDH-mutant gliomas, monocyte-derived MΦ drive a tolerogenic remodeling of the glioma microenvironment thus preventing T-cell response. We define the molecular mechanism responsible for the tumor genotype-dependent education of infiltrating MΦ to be causally related to an enzymatically enhanced tryptophan catabolism via TDO2, resulting in the production of kynurenine, an endogenous ligand of the aryl hydrocarbon receptor (AHR). TDO2 activation further induces an amino acid starvation response triggering the import of exogenous tryptophan by intratumoral MΦ via LAT1-CD98. We here provide evidence that paracrine R-2-HG and tryptophan are critically involved in the differentiation and activation of monocyte-derived MΦ and that the previously observed altered amino acid metabolism in IDHmut gliomas is also responsible for shaping an immunosuppressive tumor microenvironment through maintenance of this complex metabolic axis. We further show that this regulatory metabolic network is particularly active in infiltrating MΦ because of their distinct expression profile that constitutes an immune subset-specific metabolic vulnerability. Consequently, the immunosuppressive phenotype in IDH-mutant glioma models was reversed by pharmacological inhibition of LAT1-CD98 or AHR. Thus, we provide evidence for a tumor genotype-dependent, dynamic network of resident and recruited intratumoral myeloid cells that shape the immune microenvironment of IDH-mutant HGG through pleiotropic interaction with the tumor metabolome and identify tryptophan metabolism as a viable therapeutic target for the immunotherapy of IDH-mutant tumors.

Project description:Recent single-cell transcriptomic studies report that IDH-mutant gliomas share a common hierarchy of cellular phenotypes, independent of genetic subtype. However, the genetic differences between IDH-mutant glioma subtypes are prognostic, predictive of response to chemotherapy, and correlate with distinct tumor microenvironments. To reconcile these findings, we profiled 22 human IDH-mutant gliomas via single-cell assay for transposase-accessible chromatin (scATAC-seq). We determined the cell-type specific differences in transcription-factor expression and associated regulatory grammars between IDH-mutant glioma subtypes. We find that while IDH-mutant gliomas do share a common distribution of cell types, there are significant differences in the expression and targeting of transcription factors that regulate glial identity and cytokine elaboration. We knocked out the chromatin-remodeler ATRX, which suffers loss-of-function alterations in most IDH-mutant astrocytomas, in an IDH-mutant immunocompetent intracranial murine model. We find that both human ATRX-mutant gliomas and murine ATRX-knockout gliomas are more heavily infiltrated by immunosuppressive monocytic-lineage cells derived from circulation than ATRX-intact gliomas, in an IDH-mutant background. ATRX knockout in murine glioma recapitulates gene expression and open-chromatin signatures that are specific to human ATRX-mutant astrocytomas, including drivers of astrocytic lineage and immune-cell chemotaxis. ATRX knockout in murine glioma recapitulates gene expression and open chromatin signatures that are specific to human ATRX-mutant astrocytomas, including drivers of astrocytic lineage and immune-cell chemotaxis. Through single-cell cleavage under targets and tagmentation assays and meta-analysis of public data, we show that ATRX loss leads to a global depletion in CCCTC-binding factor association with DNA, gene dysregulation along associated chromatin loops, and protection from therapy-induced senescence.

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Tryptophan metabolism drives dynamic immunosuppressive myeloid states in IDH-mutant gliomas [CEL-Seq2]

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