Figure 4

The NSC23925 specifically prevented Pgp overexpression during paclitaxel treatment. (A and B) Expression level of Pgp, BCRP and MRP1 in different U-2OS and Saos cell sublines detected by western blot, respectively. Western blot analysis demonstrated that U-2OS/paclitaxel and Saos/paclitaxel cells eventually expressed significantly higher Pgp. However, no significant change in Pgp expression level was observed in U-2OS/paclitaxel–NSC23925 and Saos/paclitaxel–NSC23925 cells compared with parental cells. Increases in the Pgp level detected in the different cell sublines showed a strong association with the increase in the concentration of paclitaxel tolerated by cells. No significant difference of MRP1 and BCRP levels were observed among the different cell sublines. (C) Relative Pgp expression of western blot from (A and B) were analysed by densitometry. The labels correspond to those given in (A and B). Data are presented as means±s.d. and analysed using Student’s t-test (two tailed, unequal variance). Statistical comparisons between selected and parental cells are presented: *P<0.05, **P<0.005, ***P<0.001. (D) Expression level of Pgp in U-2OS cell sublines analysed by immunofluorescence. The U-2OS/paclitaxel_0.2 cells displayed significantly higher Pgp staining than U-2OS/paclitaxel_0.006–NSC23925 cells.