Sydney Dumont

Glioma contains malignant cells in diverse states. Here, we combine spatial transcriptomics, spatial proteomics, and computational approaches to define glioma cellular states and uncover their organization. We find three prominent modes of organization. First, gliomas are composed of small local environments, each typically enriched with one major cellular state. Second, specific pairs of states preferentially reside in proximity across multiple scales. This pairing of states is consistent across tumors. Third, these pairwise interactions collectively define a global architecture composed of five layers. Hypoxia appears to drive the layers, as it is associated with a long-range organization that includes all cancer cell states. Accordingly, tumor regions distant from any hypoxic/necrotic foci and tumors that lack hypoxia such as low-grade IDH-mutant glioma are less organized. In summary, we provide a conceptual framework for the organization of cellular states in glioma, highlighting hypoxia as a long-range tissue organizer.

Abstract Immunotherapy failures can result from the highly suppressive tumour microenvironment that characterizes aggressive forms of cancer such as recurrent glioblastoma (rGBM) 1,2 . Here we report the results of a first-in-human phase I trial in 41 patients with rGBM who were injected with CAN-3110—an oncolytic herpes virus (oHSV) 3 . In contrast to other clinical oHSVs, CAN-3110 retains the viral neurovirulence ICP34.5 gene transcribed by a nestin promoter; nestin is overexpressed in GBM and other invasive tumours, but not in the adult brain or healthy differentiated tissue 4 . These modifications confer CAN-3110 with preferential tumour replication. No dose-limiting toxicities were encountered. Positive HSV1 serology was significantly associated with both improved survival and clearance of CAN-3110 from injected tumours. Survival after treatment, particularly in individuals seropositive for HSV1, was significantly associated with (1) changes in tumour/PBMC T cell counts and clonal diversity, (2) peripheral expansion/contraction of specific T cell clonotypes; and (3) tumour transcriptomic signatures of immune activation. These results provide human validation that intralesional oHSV treatment enhances anticancer immune responses even in immunosuppressive tumour microenvironments, particularly in individuals with cognate serology to the injected virus. This provides a biological rationale for use of this oncolytic modality in cancers that are otherwise unresponsive to immunotherapy (ClinicalTrials.gov: NCT03152318 ).

Diffusely infiltrating gliomas - including glioblastoma (GBM), isocitrate dehydrogenase (IDH) mutant gliomas, and histone 3 (H3) altered gliomas - are primary brain tumors with an invariably fatal outcome. Despite advances in the understanding of their biology, standard, targeted and immune checkpoint inhibitor immunotherapies have proven ineffective in arresting their inexorable progression and associated morbidity and mortality. Recognizing the unique aspects of the immunogenicity of cancer cells, the last decade has seen the development and evaluation of vaccine-based therapies for the treatment of solid tumors, including gliomas. Here we review the current vaccine strategies for the treatment of GBM, IDH-mutant gliomas and diffuse midline glioma H3 K27M-altered. We discuss potential benefits and challenges of vaccine therapies in these specific patient populations.

Abstract Isocitrate dehydrogenase (IDH)-mutant glioma is the most common primary brain tumor diagnosed in patients younger than 50 years old. While IDH inhibitors have shown promise for patients with low-grade disease, patients with higher-grade tumors still have limited treatment options and face poor clinical outcomes. Chimeric antigen receptor (CAR)-T cell therapies have demonstrated potential in other molecularly-distinct gliomas, but directing this immunotherapeutic strategy towards IDH-mutant glioma remains largely unexplored. Our prior work using single-cell RNA sequencing (scRNAseq) has defined a hierarchical model of transcriptional states in IDH-mutant glioma, including a central ‘stem-like’ population that is enriched for cycling cells and drives overall disease progression. We hypothesize that targeting this stem-like population in IDH-mutant glioma using CAR-T cell therapy will enable effective control of these tumors. To design CAR constructs that target this population, we performed in silico screening of scRNAseq data from IDH-mutant glioma patient samples to identify highly expressed genes associated with the stem-like surfaceome. Candidate targets with publicly available single-chain variable fragments (scFvs) were engineered into tool 2nd generation CARs and screened for antitumor activity against patient-derived IDH-mutant glioma models. Coculture assays demonstrated in vitro cytokine production and antitumor cytotoxicity against these patient-derived models. Additionally, we demonstrate the ability of these CAR-T cells to clear an aggressive patient-derived orthotopic IDH-mutant glioma xenograft model and significantly extend survival. In summary, our findings validate the potential of a cell state-directed strategy to identify CAR-T cell targets in IDH-mutant gliomas that may inform future translational efforts.