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Multiregional sampling of primary glioblastoma specimens

ABSTRACT: Glioblastoma (GBM), the most common malignant tumor originating in the brain remains incurable with few treatment advances despite decades of investigation. Treatment failure is often attributed to intratumoral heterogeneity, which fosters tumor evolution and selection of resistant clones. However, intratumoral heterogeneity and tumor evolution remain poorly understood in GBM as studies are typically based on single tissue biopsies and lack spatial context. Here, we have utilized pre-operative MRI scans and intra-operative 3-D surgical neuronavigation for 10 primary IDH-WT GBM patients to acquire 103 tissue samples that represent maximal tumor diversity and are mapped by 3-D spatial coordinates. We combine insights from deconvolution of GBM transcriptomes and chromatin landscapes with single-cell analysis to assess intratumoral heterogeneity of each program at the cellular level and to distinguish neuronal, glial, and immune programs aberrantly active in tumor cells from their counterparts in normal cells. Collectively, these data provide unprecedented insight into GBM intratumoral heterogeneity and evolution from single-cell to whole-tumor 3D spatial resolution, redefining current understanding and providing a rich resource of targets for therapeutic investigation.

ORGANISM(S): Homo sapiens

PROVIDER: GSE226726 | GEO | 2024/01/18

REPOSITORIES: GEO

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Project description:G protein-coupled receptor 56 (GPR56/ADGRG1) is an adhesion GPCR with an essential role in brain development and cancer. Elevated expression of GPR56 was observed in the clinical specimens of Glioblastoma (GBM), a highly invasive primary brain tumor. However, we found the expression to be variable across the specimens, presumably due to the intratumor heterogeneity of GBM. Therefore, we re-examined GPR56 expression in public domain spatial gene expression data and single-cell expression data for GBM, which revealed that GPR56 expression was high in cellular tumors, infiltrating tumor cells, and proliferating cells, low in microvascular proliferation and peri-necrotic areas of the tumor, especially in hypoxic mesenchymal-like cells. To gain a better understanding of the consequences of GPR56 downregulation in tumor cells and other molecular changes associated with it, we generated a sh-RNA-mediated GPR56 knockdown in the GBM cell line U373 and performed transcriptomics, proteomics, and phospho-proteomics analysis. Our analysis revealed enrichment of gene signatures, pathways, and phosphorylation of proteins potentially associated with mesenchymal (MES) transition in the tumor and concurrent increase in cell invasion and migration behavior of the GPR56 knockdown GBM cells. Interestingly, our analysis also showed elevated expression of Transglutaminase 2 (TG2) - a known interactor of GPR56, in the knockdown cells. The inverse expression of GPR56 and TG2 was also observed in intratumoral, spatial gene expression data for GBM and in GBM cell lines cultured in vitro under hypoxic conditions. Integrating all these observations, we infer a functional link between the inverse expression of the two proteins, the hypoxic niche, and the mesenchymal status in the tumor. Hypoxia-induced downregulation of GPR56 and activation of TG2 may result in a network of molecular events that contribute to the mesenchymal transition of GBM cells, and we propose a putative model to explain this functional and regulatory relationship of the two proteins.

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Multiregional sampling of primary glioblastoma specimens

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