ABCB1 and glioblastoma: Consistent with in vitro results, in vivo findings obtained using subcutaneous murine glioblastoma xenografts highlighted that rucaparib could potentially act synergistically with temozolomide, while the lack of the same effect in orthotopic glioblastoma mouse models confirmed that MDR1 and BCRP1 significantly limit the potential utility of PARP inhibitors in clinical use [26].