It has previously been reported that PI3K inhibition sensitizes tumor cells to extrinsic TRAIL-induced apoptosis as well as apoptosis induced by DNA damaging agents [40–44, 58] while another study suggests that PI3K inhibition in GBM stem cells and differentiated primary cells only leads to poor or negative chemosensitization [45]. This evidence concerns the gene TNFSF10 and glioblastoma.