Figure 1

MCF-7/Adr cells show the mdr phenotype. a: Wild-type MCF-7 cells exposed to IC90 of adriamycin show expected growth inhibition, whereas MCF-7/Adr cells are resistant to adriamycin as evaluated by the MTT assay; b: RT-PCR analysis of the mdr1 gene demonstrates that MCF-7/Adr cells over-express the mdr1 transcript; c: Flow cytometric analysis of adriamycin-treated cells for 1 h show that wild-type MCF-7 cells retain the majority of adriamycin inside the cell (M1); however, MCF-7/Adr cells have essentially no drug accumulation, indicative of the presence of a functional mdr1 protein, and d: MCF-7/adr cells demonstrate cross-resistance to paclitaxel but not to 5-fluorouracil and cisplatin.