TGFB1 and glioblastoma: Using an in vitro BBB model containing primary brain pericytes and microvascular endothelial cells as well as glioma cells or astrocytes, we demonstrate that the treatment of tight endothelial cell/pericyte layers with TGF-β, or co-culture of these layers with TGF-β-secreting GBM cells, resulted in the disruption of this so far intact BBB.