PGP and glioblastoma: Analyses of biopsies and GBM cell lines, T98G and G44, revealed that the Multiple drug Resistance-associated Protein-1 (MRP1) is the predominant ABC transporter in GBM, compared to other transporters with roles in other types of cancer such as ABCG2 (also known as BCRP or Breast Cancer Resistance Protein) and P-glycoprotein (P-gp) [8].