Glioblastomas are aggressive primary brain cancers that recur as therapy-resistant tumors. Myeloid cells control glioblastoma malignancy, but their dynamics during disease progression remain poorly understood. Here, we employed single-cell RNA sequencing and CITE-Seq to map the glioblastoma immune landscape in newly diagnosed and recurrent patients and in mouse tumors. This revealed a large and diverse myeloid compartment, with dendritic cell and macrophage populations that were conserved across species and were dynamic across disease stages. Tumor-associated macrophages (TAMs) consisted of microglia-or monocyte-derived populations, with both exhibiting additional heterogeneity, including subsets with conserved lipid and hypoxic signatures. Microglia-and monocytederived TAMs (Mo-TAMs) were self-renewing populations that competed for space and could be depleted via CSF1R blockade. Microglia-derived TAMs were predominant in newly diagnosed tumors but were outnumbered by Mo-TAMs upon recurrence, especially in hypoxic tumor environments. Our results unravel the glioblastoma myeloid landscape and provide a framework for future therapeutic interventions.

Clinically relevant immunological biomarkers that discriminate between diverse hypofunctional states of tumor-associated CD8 + T cells remain disputed. Using multiomics analysis of CD8 + T cell features across multiple patient cohorts and tumor types, we identified tumor niche–dependent exhausted and other types of hypofunctional CD8 + T cell states. CD8 + T cells in “supportive” niches, like melanoma or lung cancer, exhibited features of tumor reactivity–driven exhaustion (CD8 + T EX ). These included a proficient effector memory phenotype, an expanded T cell receptor (TCR) repertoire linked to effector exhaustion signaling, and a cancer-relevant T cell–activating immunopeptidome composed of largely shared cancer antigens or neoantigens. In contrast, “nonsupportive” niches, like glioblastoma, were enriched for features of hypofunctionality distinct from canonical exhaustion. This included immature or insufficiently activated T cell states, high wound healing signatures, nonexpanded TCR repertoires linked to anti-inflammatory signaling, high T cell–recognizable self-epitopes, and an antiproliferative state linked to stress or prodeath responses. In situ spatial mapping of glioblastoma highlighted the prevalence of dysfunctional CD4 + :CD8 + T cell interactions, whereas ex vivo single-cell secretome mapping of glioblastoma CD8 + T cells confirmed negligible effector functionality and a promyeloid, wound healing–like chemokine profile. Within immuno-oncology clinical trials, anti–programmed cell death protein 1 (PD-1) immunotherapy facilitated glioblastoma’s tolerogenic disparities, whereas dendritic cell (DC) vaccines partly corrected them. Accordingly, recipients of a DC vaccine for glioblastoma had high effector memory CD8 + T cells and evidence of antigen-specific immunity. Collectively, we provide an atlas for assessing different CD8 + T cell hypofunctional states in immunogenic versus nonimmunogenic cancers.

Tumoural-CD8+T cells exhibit exhausted or dysfunctional states. Contrary to immunotherapy-responsive exhausted-CD8+T cells, the clinical features of dysfunctional-CD8+T cells are disputed. Hence, we conducted large-scale multi-omics and multi-dimensional mapping of CD8+T cell-states across multiple cancer patient-cohorts. This identified tumour-specific continuum of CD8+T cell-states across 6 human cancers, partly imprinted by organ-specific immuno-modulatory niches. Herein, melanoma and glioblastoma enriched prototypical exhausted (CD8+TEXT) and severely-dysfunctional (CD8+TSDF) states, respectively. Contrary to CD8+TEXT, CD8+TSDF displayed transcriptomic and epigenetic effector/cytolytic dysfunctions, and dysregulated effector/memory single-cell trajectories, culminating into maladaptive prodeath stress and cell-cycle defects. Suboptimal antigen-priming underscored CD8+TSDF, which was distinct from immune-checkpoints “rich” CD8+TEXT, reflecting chronic antigen-stimulation. Continuum variation also existed on tumour spatial-level, with convergent (CD8+TEXT-supportive vascular regions) and divergent features (dysfunctional CD4+T::CD8+TSDFcell-to-cell interactions) between melanoma and glioblastoma. Globally, IFNγ-IL2 disparities, paucity of intra-tumoural CD4+/CD8+T cells, and myeloid TGFβ/wound healing responses, distinguished CD8+TSDF-landscape. Within immuno-oncology clinical-trials, anti-PD1 immunotherapy failed to “reinvigorate” CD8+TSDF-landscape, and instead facilitated effector-dysfunction and TGFβ/wound healing. However, cellular immunotherapies (dendritic cell-vaccines, adoptive T-cell therapy) ameliorated assorted CD8+TSDF-landscape disparities, highlighting a roadmap for anti-glioblastoma multimodal-immunotherapy. Collectively, our study comprehensively expands clinical-knowledge on CD8+T cell-exhaustion and suggests that tumour-specific, pre-existing CD8+TEXT/TSDF-states, determine immunotherapy-responses.

Single-cell omics aim at charting the different types and properties of all cells in the human body in health and disease. Over the past years, myriads of cellular phenotypes have been defined by methods that mostly required cells to be dissociated and removed from their original microenvironment, thus destroying valuable information about their location and interactions. Growing insights, however, are showing that such information is crucial to understand complex disease states. For decades, pathologists have interpreted cells in the context of their tissue using low-plex antibody- and morphology-based methods. Novel technologies for multiplexed immunohistochemistry are now rendering it possible to perform extended single-cell expression profiling using dozens of protein markers in the spatial context of a single tissue section. The combination of these novel technologies with extended data analysis tools allows us now to study cell-cell interactions, define cellular sociology, and describe detailed aberrations in tissue architecture, as such gaining much deeper insights in disease states. In this review, we provide a comprehensive overview of the available technologies for multiplexed immunohistochemistry, their advantages and challenges. We also provide the principles on how to interpret high-dimensional data in a spatial context. Similar to the fact that no one can just “read” a genome, pathological assessments are in dire need of extended digital data repositories to bring diagnostics and tissue interpretation to the next level.

IntroductionDiffuse intrinsic pontine glioma is a rare disease with a high mortality. Our primary aim was to determine the incidence of this disease in Belgium. Secondly, we wanted to compare the treatment approach of Belgian pediatric oncology centres, to investigate possibilities for improvement. MethodsWe retrospectively collected and analysed data on DIPG-patients diagnosed between 1994 and 2018 and recorded in the Belgian Cancer Registry.We included patients ≤ 18 years who were followed in one of the eight Belgian pediatric oncology centres. ResultsWe included 100 patients over a period of 25 years with a median age at diagnosis of 7 years. We observed an increase in diagnoses with an incidence of 3.1 per 1,000,000 persons (aged 0-≤18) per year over the last 5 years compared to an overall incidence of 1.8. Forty-ve patients (51.7%) were biopsied at diagnosis. In ten (22%), this was study-related. H3 K27M-mutation was present in 75% of biopsied patients. Fifty-one patients (59.3%) received chemotherapy, without a signi cant survival bene t. Eleven patients (21.2%) were included in a clinical trial. Biopsy rate and the use of chemotherapy differed widely between centres. Mean OS and PFS were 10.49 and 4.87 months respectively. We observed an improved survival over time. ConclusionsOver the past 25 years, we observed an increase of new DIPG-diagnoses. Outcome in our cohort is comparable with literature ndings. We demonstrate an important heterogeneity in treatment approach between different centres and limited inclusion in clinical trials. Therefore, collaboration between centres and inclusion of patients in clinical trials is much needed.