ABCBl-mediated multidrug resistance (MDR) remains a major obstacle to successful chemotherapy inovarian cancer.Herein,afatinib at nontoxic concentrations significantly reversed ABCBl-mediated MDR inovarian cancer cells in wtro (p<0.05).Combining paclitaxel and afatinib caused tumor regressions and tumornecrosis in A2780T xenografts in vivo. More interestingly,unlike reversible TKIs,afatinib had a distinctivedual-mode action.Afatinib not only inhibited the efflux function of ABCBl,but also attenuated its expression transcriptionally via down-regulation of PI3K/AKT and MAPK/p38-dependent activation of NF-κB.Furthermore,apart from a substrate binding domain,afatinib could also bind to an ATP binding domain of ABCBl throughforming hydrogen bonds with Gly533,Gly534,Lys536 and Ala560 sites.Importantly,mutations in these four binding sites of ABCBl and the tyrosine kinase domain of EGFR were not correlated with the reversal activity of afatinib on MDR.Given that afatinib is a clinically approved drug,our results suggest combining afatinib with chemotherapeutic drugs in ovarian cancer. This study can facilitate the rediscovery of superior MDR reversalagents from molecular targeted drugs to provide a more effective and safer way of resensitizing MDR.
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