Interplay between gbm and immune cells in the mouse glioma microenvironment at single-cell resolution

Abstract Glioblastoma (GBM) is the most common primary tumor of the central nervous system in adults. GBM patients have a particularly poor prognosis and extremely short survival time due to lack of effective therapies and rapid tumor relapse. Neoplastic cells should be effectively recognized and destroyed by the immune system, but its antitumor activity is often inhibited by tumor-secreted factors that contribute to the tumor immunosuppressive microenvironment (TME). As TME plays a key role in cancer progression and immune evasion, understanding the interplay between GBM cells and myeloid and lymphoid populations is pivotal in creating new therapeutic strategies for GBM patients. To identify subtypes and functional diversity of immune cells in glioma TME we employed single-cell RNA and protein sequencing (CITEseq, Cellular Indexing of Transcriptomes and Epitopes by Sequencing) and Visium (10XGenomics) spatial transcriptomics. We characterized the populations of myelo- and lymphoid cells, and examined their unique transcription profiles, functional diversity and localization in TME. By combining analysis of CITE-seq with spatial transcriptomics we characterized and described 35 phenotypes of immune cells, which then we localized spatially within TME in GL261 mouse gliomas. Our results indicated that the peripheral monocytes/macrophages (Cd49d) localized in the tumor core, while microglia (Tmem119) accumulated at the invasive edge. Moreover, we observed a ring of activated astrocytes and rare T lymphocytes dispersed around the tumor. Finally, Ligand-Receptor and CellChat analysis of our CITE-seq results revealed the interplay between GBM, myeloid cells and lymphocytes, indicated on potential factors responsible for accumulation and tumor-evoked reprograming of immune cells. Single-cell technologies provide high-resolution insights into cellular and functional heterogeneity of gliomas, the analysis of which, in the future, will provide us with new therapeutic strategies for GBM patients. Studies were supported by NSC grant 2020/39/B/NZ4/02683 (BK) and PACIFIC Call 1 PAS (MG).