Purpose: The objective of our study was to investigate the effect of single and multiple flavonoids on the accumulation and cytotoxicity of mitoxantrone in BCRP-overexpressing breast cancer cells and on the transport of mitoxantrone in BCRP-expressing normal cells.
Methods: The effect of flavonoids on mitoxantrone accumulation and cytotoxicity was studied in the human breast cancer MCF-7 MX100 cell line. Mitoxantrone transport in the presence of flavonoids was studied in human and murine BCRP-transfected MDCK cell lines, and mitoxantrone concentrations were determined by HPLC.
Results: Our results demonstrated that multiple flavonoid combinations act additively and exhibit strong BCRP inhibition for increasing mitoxantrone accumulation in breast cancer cells. Kaempferide, biochanin A, 5,7-dimethoxyflavone, and 8-methylflavone greatly increased the cytotoxicity of mitoxantrone in BCRP-overexpressing breast cancer cells. Additionally, the basolateral-to-apical membrane-directed transport of mitoxantrone in murine Bcrp1- and human BCRP-expressing MDCK cells, in the presence of 2.5 microM of these flavonoids, was also significantly decreased.
Conclusion: The results indicate that flavonoids are potent BCRP inhibitors and that they exert additive effects when used in combination. Flavonoids demonstrate MDR-reversing effects, but also may influence the disposition of mitoxantrone and cause pharmacokinetic interactions.