CNSC-30. IN VIVO DYNAMICS OF ASTROCYTE-GLIOBLASTOMA TUMOR NETWORKS

Abstract

Abstract As one of the most aggressive incurable primary brain tumors, glioblastomas show a high invasivity and therapeutic resistance caused by their cellular and molecular heterogeneity. In previous studies, we showed that glioma cells interconnect using membrane protrusions called tumor microtubes to form a therapy-resistant malignant network. Here, we extend the concept of tumor networks to heterogeneous connectivity with the glial microenvironment. Using high-resolution light microscopy, ultrastructural tissue imaging, patch-clamp electrophysiology, intravital structural and functional microscopy, we characterize tumor-astrocyte connectivity. First, we used high-resolution light microscopy with immunohistochemistry and ultrastructural imaging to discover and characterize gap junctional connections between tumor cells and astrocytes. Next, we probed functional, heterotypic connections using dye filling with patch-clamp electrophysiology. Employing calcium imaging, we could demonstrate bidirectional communication patterns between tumor cells and astrocytes. We further characterized the stability of these astrocyte-glioma networks by using longitudinal imaging of single cells over several weeks in patient-derived xenograft models. For this, we used sulforhodamine 101 (SR101) as a marker for astrocyte-glioma connectivity to simultaneously visualize tumor cells and their glial microenvironment. The percentage of SR101 uptake in glioma cells increases over time, showing an increasing integration of tumor cells into the tumor-and astrocyte network during tumor evolution. Tumor cells, which are unconnected to other tumor cells or astrocytes, are the main drivers of invasion while a subgroup of glioma cells with stable astrocyte connectivity stay in place over several weeks. Lastly, we showed how these functional, heterotypic connections contribute to therapeutic resistance in the context of radiotherapy. In conclusion, we investigated multicellular networks between glioblastoma cells and astrocytes, their plasticity and role for therapeutic resistance.