Résumé
Aim To study the mechanism of synergistic antitumor of EBB and doxorubicin in doxorubicin-resistant MCF-7/ADR breast carcinoma cells.Methods The antitumor activity of doxorubiein alone and its combination with EBB were measured by MTT assay in MCF-7/ADR and MCF-7cells. The rate of doxorubicin-induced apoptosis and the protein and mRNA levels of P-glycoprotein(P-gp) were determined in MCF-7/ADR treated with EBB by flow cytometry (FACS), respectively.Laser scanning confocal microscopy was used to detect the intracellular accumulation of drug in EBB-treated MCF-7 and MCF-7/ADR cells.Results EBB had antitumor effects for MCF-7 and MCF-7/ADR.It could potentiate the antitumor effect of dororubicin with CDI of 0.73 and 0.49 for MCF-7 and MCF-7/ADR,respectively.EBB and doxorubicin acted synergistically in elevating apoptosis of MCF-7/ADR and downregulating the expression of P-gp in a dose-dependent manner in MCF-7/ADR.EBB restored the intracellular accumulation of doxorubicin in MCF-7/ADR cells in a dose-dependent manner.After pretreatment with EBB for 24 h and 48 h,the intracellular accumulation of doxorubicin and Rh123 was obviousely restored in MCF-7/ADR cells compared with control in a time-dependent manner.Conclusion EBB is a potential agent which has strong inhibitory effect on both multidrug resistant cells and their parental cells.EBB can significantly potentiate the antitumor effects of dororubicin in MCF-7/ADR cells by blocking the function of P-glycoprotein and inhibiting the expression of P-glycoprotein.
Résumé
Aim To investigate subcellular distribution and accumulation of ADR in the sensitive and multidrug-resistant HL-60 cells and its relation to multidrug resistance.Methods The subcellular distribution and accumulation of ADR were studied by confocal scanning laser microscope and flow cytometry.The effects of verapamil,BSO,brefeldin A and chloroquine on ADR distribution and accumulation in HL-60/ADR cells were also examined.Rhodamine123,NBD-ceramide and neutral red were used as fluorescent probes to stain the mitochondria,Golgi apparatus and lysosomes respectively were used to identify the subcellular compartments where ADR was sequestered.Results In drug-sensitive cell line HL-60,ADR fluorescence distributed evenly in the nucleus and cytoplasm,while in multidrug-resistant cell line HL-60/ADR,ADR fluorescence distributed in a punctated pattern in the cytoplasm and was reduced in the nucleus.The mode of ADR distribution in HL-60/ADR cells is highly similar to that of NBD-ceramide.BSO and brefeldin A,instead of verapamil and chloroquine could reverse the abnormal distribution and accumulation of ADR in HL-60/ADR cells.Conclusions The change of ADR distribution and reduction of ADR accumulation in multidrug-resistant cell line was involved in the mechanism of multidrug resistance.