Figure 1.
Structure of tariquidar (XR9576).
Figure 2.
Effect of tariquidar on the sensitivity of HEK/pcDNA and HEK/MRP7 cells to anticancer drugs.
HEK/pcDNA cells and HEK/MRP7 cells were cultured for 24 h before tariquidar was added. After 1 h incubation, paclitaxel (A), docetaxel (B), vincristine (C), vinorelbine (D), vinblastine (E), or cisplatin (F) was added, and the cultures were incubated for 72 h. Cell viability was measured by the MTT assay. Results were representative of 3 independent experiments.
Table 1.
Effect of tariquidar and cepharanthine on the cytotoxicity of paclitaxel, docetaxel, vincristine, vinblastine, vinorelbine and cisplatin in MRP7-transfected cells.
Figure 3.
Effect of tariquidar treatment on protein and mRNA expression of MRP7 in HEK/pcDNA and HEK/MRP7 cells.
(A) The effect of 0.3 µM tariquidar treatment on the protein expression of MRP7 in HEK/pcDNA and HEK/MRP7 cells at 0, 4, 12, 24, 48 and 72 h. (B) The effect of 72 h tariquidar treatment at difference concentrations on the protein expression of MRP7 in HEK/pcDNA and HEK/MRP7 cells. (C) mRNA levels of MRP7 in HEK/pcDNA and HEK/MRP7 cells treated with 0.3 µM tariquidar at different time points. GAPDH was used as a loading control. The protein or mRNA levels of MDR7 were normalized to those of GAPDH and shown on the right. Results are represented as mean ± SD. P values were obtained using analysis of variance by comparing the relative amounts of protein or mRNA in cells treated with tariquidar with those in untreated control cells. Results representative of 3 independent experiments are shown. *: P<0.05; **: P<0.01.
Figure 4.
Effect of tariquidar treatment on the subcellular localization of MRP7.
HEK/MRP7 cells were treated with 0.3 µM tariquidar for different periods of time. The subcellular localization of MRP7 was analyzed by immunofluorescence. MRP7 staining is shown in green. DAPI (blue) counterstains the nuclei.
Figure 5.
Effect of tariquidar on the accumulation of paclitaxel in HEK/pcDNA and HEK/MRP7 cells.
The accumulation of [3H]-paclitaxel was measured after preincubation in the presence or absence of tariquidar at 0.1 µM and 0.3 µM for 2 h (A) or 70 h (B) at 37°C, followed by incubation with 0.1 µM [3H]-paclitaxel with or without of the reversal agents for another 2 h at 37°C. Then, the cells were collected and the intracellular level of [3H]-paclitaxel was detected by scintillation counting. Experiments were done in triplicates, and results were expressed as mean ± SD. *P<0.05, versus the respectively untreated controls. Flow cytemetric detection of the amount of intracellular BODIPY-paclitaxel inside HEK/MRP7 cells after treatment with tariquidar for 4 h and 72 h. The histograms represent the fluorescence signal of intracellular BODIPY-paclitaxel in the presence (dashed line) or absence (shaded histogram) of 4 h (C) or 72 h (D) treatment with 0.3 µM tariquidar.
Figure 6.
Effect of tariquidar on the efflux of paclitaxel in HEK/pcDNA and HEK/MRP7 cells.
The efflux assay was performed as described in Materials and Methods. The values at 0 min were set as 100%. Each data point represents the mean ± SD of three independent experiments, each performed in triplicates. *P<0.05, versus HEK/MRP7 cells without tariquidar treatment.