Abstract
Children diagnosed for brain tumors are facing variant prognoses depending mostly on the histological subtypes and their molecular characteristics. Nevertheless, more and more evidence is accumulating on the diffuse infiltrative growth pattern of the tumor, playing its own role in tumor development and progression. This infiltration is reflecting the interaction with tumor microenvironment, which seems to have a profound influence on the functional properties of tumor cells. Accordingly, substantial effort must be devoted to move to three-dimensional like systems that more faithfully recapitulate the hypoxic and in vivo tumor microenvironment. Therefore, we developed PDCL initiated from several pediatric malignant brain tumors (high grade gliomas, medulloblastomas and ependymomas). After establishing stably those PDCLs and exploring their characteristics, we developed spheroid migration assays on fibronectin in hypoxic conditions to recreate both physiological hypoxia of normal brain and tumor hypoxia. In parallel, with these PDCLs, we developed mouse orthotopic xenotransplantations. We were able in all cell lines to perform those spheroid migration assays. The quantification of cells evading from the spheroid and their distance of migration were heterogeneous, not linked to the histological subtypes, but to the in vivo progression of the patient. The cells were preserving mostly their stem-like properties. Surprisingly, we were not able to reproduce the same correlations in the mouse models. Our results present an optimized invasion assay that closely reflects in vivo invasion and might be used as a predictive model for the patient, as well as a new approach to test treatments blocking this brain infiltration.