PGP and malignant peripheral nerve sheath tumor: Similarly, prior studies in MPNST confirmed the presence of drug resistant sarcoma stem cells [67, 68] and the P-gp and BCRP efflux pumps [47, 50, 69, 70], while drug trials in MPNST patients have not improved outcomes [50, 71] Our findings provide a rationale to further study the hypothesis that endothelial BCRP expression may be part of the reason why drug therapy of PNST often fails [47].