Figure 1

Establishment of MCF-7/BCRP cells and effects of PI3K inhibitors on anticancer drug resistance. (A) BCRP expression in MCF-7/BCRP cells. Protein sample (20 μg) was loaded in each lane and BCRP was detected by western blot analysis with the anti-BCRP antibody, BXP-21. (B) Effects of LY294002 on anticancer drug resistances of MCF-7/BCRP cells. Cells (3 x 10⁴/well) were seeded into 12-well plates, and cultured in the absence or presence of various concentrations of anticancer drugs with or without LY294002 for 4 days. Cell numbers were determined, and presented as percentages relative to those of control cells cultured in the absence of anticancer agents. Open symbols, MCF-7 cells. Closed symbols, MCF-7/BCRP cells. Square, without LY294002. Lozenge, 1 μM of LY294002. Circle, 2 μM of LY294002. (C) LY294002 resistance of MCF-7/BCRP cells. Cells (3 x 10⁴/well) were seeded into 12-well plates, and cultured in the absence or presence of various concentrations of LY294002 for 4 days. Cell numbers were determined, and presented as percentages relative to those of control cells cultured without LY294002. Open bars, MCF-7 cells. Dotted bars, the MCF-7/BCRP cells. (D) Effects of wortmannin or PI-103 on SN-38 resistances of MCF-7/BCRP cells. Experiment was performed in the same way as in the legend of (B). Open symbols, MCF-7 cells. Closed symbols, MCF-7/BCRP cells. Square, without wortmannin or PI-103. Lozenge, 1 μM of wortmannin or 50 nM of PI-103. Circle, 2 μM of wortmannin or 100 nM of PI-103. Partially reproduced by permission from Spandidos Publications. Inc. Imai Y, et al. (19).