We wanted to find out whether the sensitization effect is limited to ABCB1-overexpressing cancer cells with acquired MDR (maybe only to MCF-7/KCR breast cancer cells) or whether it is a general feature that is exhibited on other MDR cell lines with a different anatomical origin, or a different ABC transporter profile (maybe cells with inherent MDR) as well. This evidence concerns the gene ABCB1 and cancer.