Intra-tumor heterogeneity of glioblastoma residual disease at single-nucleus and spatial resolution

The treatment of the most aggressive primary brain tumor in adults, glioblastoma (GBM), is challenging due to its heterogeneous nature, invasive potential, and poor response to chemo and radiotherapy. As a result, GBM inevitably recurs, and only approximately 7% of patients survive 5 years post-diagnosis. GBM is characterized by extensive phenotypic and genetic heterogeneity, which creates a diversified genetic landscape and a network of biological interactions promoting tumor growth and therapeutic resistance. This includes spatial and temporal changes in the tumor microenvironment, which influence cellular behaviors and therapeutic responses.
Over the past several years, we have developed a fluorescence-guided multiple sampling scheme, allowing the objective identification of tumor areas in GBM patients. Using this scheme, we identified areas of residual disease in the sub-ventricular zone (SVZ) of the lateral ventricles and the infiltrative margin, which represents the interface between the tumor mass and the normal brain parenchyma.
This presentation will focus on our single-nucleus and spatial transcriptomic dataset of the SVZ microenvironment using tissue samples collected from 15 GBM patients. We comprehensively compared tumor mass samples isolated from the same patients and used two histologically normal SVZ samples as controls. We found that in GBM patients, the SVZ microenvironment is characterized by a ZEB1-centered mesenchymal signature and tumor-supportive microglia, which spatially coexist and establish cross-talks with tumor cells. Moreover, differential gene expression analyses, predictions of ligand–receptor, and incoming/outgoing interactions revealed that microglia interact with tumor cells through the IL-1β/IL-1RAcP and Wnt-5a/Frizzled-3 pathways. Lastly, in vitro targeting of these pathways significantly reduces the ability of SVZ-derived tumor cells to proliferate and migrate. Altogether, our data provide insights into the biology of the SVZ in GBM patients and identify potential targets of this microenvironment.