Human brain microvascular ECs (ScienCell and PromoCell, isolated from adult or fetal human brains) and GBM-derived ECs were maintained as previously described13 (link),14 (link). In brief, cells were cultured in Endothelial Cell Medium (ScienCell, supplemented with vascular endothelial growth factor A) at 37°C with 5% CO2. All cells were used between passages two and five. Cells were treated with KPT9274 or PF3758309 (Selleckchem).