ABCB1 and neoplasm: Of note, the presence of drug transporters (e.g., P-glycoprotein (ABCB1), breast cancer resistance protein BCRP (ABCG2), multidrug resistance protein 2 (MRP2) (ABCC2), multidrug and toxin extrusion protein 1 (MATE1) (SLC47A1)) at the BTB also influences the delivery of nanoparticles to the tumor (reviewed in [15]).