ABCB1 and neoplasm: Tumor accumulation of Paclitaxel from Paclitaxel-C6-ceramide poly (beta-amino ester) nanoparticles was high compared to free drug in sensitive MCF-7 and multidrug resistant MCF-7TR (MDR-1 positive) human breast adenocarcinoma (van Vlerken et al., 2008).