Perivascular signals alter global genomic profile of glioblastoma and response to temozolomide in a gelatin hydrogel

Glioblastoma (GBM) is the most common primary malignant brain tumor, with patients exhibiting poor survival (median survival time: 15 months). Difficulties in treating GBM include not only the inability to resect the diffusively-invading tumor cells but also therapeutic resistance. The perivascular niche within the GBM tumor microenvironment contributes significantly to tumor cell invasion, cancer stem cell maintenance, and has been shown to protect tumor cells from radiation and chemotherapy. In this study, we describe the development of an in vitro artificial perivascular niche (PVN), culturing endothelial and stromal cells along with GBM cells within a methacrylamide-functionalized gelatin hydrogel, in order to examine how the presence of the PVN alters global genomic expression profiles. Using RNA-seq, we demonstrate that the inclusion of perivascular niche cells with GBM cells upregulates genes related to angiogenesis and remodeling, while downregulated genes are related to cell cycle and DNA damage repair. Signaling pathways and genes commonly implicated in GBM malignancy, such as MGMT, EGFR, PI3K-Akt signaling, and Ras/MAPK signaling are also upregulated in the presence of perivascular niche cells. We describe the kinetics of gene expression within the PVN hydrogels over a course of 14 days, observing the patterns associated with previously-observed GBM-mediated endothelial network co-option and regression that are altered in the presence of covalently-bound hyaluronic acid. We finally examine the effect of PVN culture on GBM cell responsiveness to temozolomide, a frontline chemotherapy used clinically against GBM. Notably, the presence of a PVN leads to significantly increased TMZ resistance compared to hydrogels containing only GBM cells. Overall, these results demonstrate that inclusion of cellular and matrix-associated elements of the PVN within in vitro models of GBM provide critical signals to regulate the phenotype and therapeutic responsiveness of GBM cells.