Tumor and microenvironment reprogramming during radiochemotherapy in glioma using a combined diagnostic imaging and single-cell RNA sequencing approach

Glioblastoma (GBM) is the most common primary brain tumor in adults with a median survival of 11-12 months. Standard therapy consists of radiotherapy (RT) plus chemotherapy with Temozolomide (TMZ), and no alternative treatment is available. We assessed changes in tumor microenvironment (TME) after RT associated with TMZ and metformin (MET) in a syngenic murine GBM model using single-cell RNA-sequencing (scRNA-seq). RT induced an enrichment of GO annotation related with cell cycle, translation and ribosome biogenesis in all tumor clusters, except the radio resistant one where an increase in the inflammatory phenotype was observed. Resident GAM were reduced after RT alone and differentially modulated by RT-drug combinations. After RT alone, we detected an increase in GAM markers and a downregulation of glycolytic metabolism in both microglial and peripheral macrophage subclusters. Association of TMZ increased the pro-inflammatory phenotype of some GAM clusters in comparison to RT. A different signature was observed for the TMZ-MET association but limited to peripheral infiltrating GAM.