TNFSF10 and glioblastoma: To test the hypothesis that the combination of TRAIL/Olaparib enhances apoptosis, U251 GBM cells were treated with vehicle, TRAIL, Olaparib or the combination of both and stained with Annexin V and Propidium iodide prior to analysis by flow cytometry, which showed enhanced apoptosis in the combination treatment when compared to the single agent treatments (Fig. 1G and Figure A in S4 Fig.).