LRPAP1 and glioblastoma: Third, ANG1005 was transported into U87 human glioblastoma cells via a saturable receptor-mediated process that was inhibited by adding RAP, a known LRP1 ligand that competitively inhibits uptake of Angiopep-2 in brain capillary cells (Demeule et al, 2008a), or by reducing LRP1 expression using siRNA.