P02.32.A SINGLE CELL RNA-SEQUENCING OF SUPRAMARGINAL GLIOBLASTOMA RESECTIONS REVEAL THAT THE MESENCHYMAL SIGNATURE IS CONFINED TO THE TUMOR BULK AND IS SHARED ACROSS MALIGNANT AND NON-MALIGNANT CELL TYPES

Abstract BACKGROUND There are four established tumor cell states in glioblastoma including astrocyte-like, oligodendrocyte precursor cell-like, neural progenitor cell-like, and mesenchymal-like states. Single-cell RNA sequencing has showed that they are all present with varying distribution between patients. However, since surgery of glioblastoma follows the principle of maximal safe resection, studies have been mainly limited to the necrotic core and contrast-enhancing zone. MATERIAL AND METHODS Here, we investigated the cellular organization of the transcriptional states within and outside of the contrast-enhancing zone. This was achieved through a unique set of supramarginal resected glioblastoma samples using large-scale single-cell RNA sequencing of fresh tissue by systematic multi-region sampling from a large number of spatial locations based on 5-ALA fluorescence. RESULTS We discovered that the mesenchymal state is region-specific, highest in the core, at the center of the tumor, shows a gradual decrease with distance from the core and is absent in the low-fluorescent zone and in the periphery, regardless of direction. More importantly, the mesenchymal signature is not only present in tumor cells but also in various other cell types including microglia, macrophages, oligodendrocytes and astrocytes. CONCLUSION Altogether, this argues that the mesenchymal state is extrinsic, driven by the macro environment, can be induced in completely different cell types and its regional distribution suggests wound-healing and hypoxia to be the main drivers.