Tamoxifen(TAM)is the first-line endocrine therapy for estrogen receptor-positive(ER+)breast cancer(BC).However,acquired resistance occurs in∼50%cases.Meanwhile,although the PI3K/AKT/mTOR pathway is a viable target fo...Tamoxifen(TAM)is the first-line endocrine therapy for estrogen receptor-positive(ER+)breast cancer(BC).However,acquired resistance occurs in∼50%cases.Meanwhile,although the PI3K/AKT/mTOR pathway is a viable target for treatment of endocrine therapy-refractory patients,complex signaling feedback loops exist,which can counter the effectiveness of inhibitors of this pathway.Here,we analyzed signaling pathways and metabolism in ER+MCF7 BC cell line and their TAM-resistant derivatives that are co-resistant to endoxifen using immunoblotting,quantitative polymerase chain reaction,and the Agilent Seahorse XF Analyzer.We found that activation of AKT and the energy-sensing kinase AMPK was increased in TAM and endoxifen-resistant cells.Furthermore,ERRα/PGC-1βand their target genes MCAD and CPT-1 were increased and regulated by AMPK,which coincided with increased fatty acid oxidation(FAO)and autophagy in TAM-resistant cells.Inhibition of AKT feedback-activates AMPK and ERRα/PGC-1β-MCAD/CPT-1 with a consequent increase in FAO and autophagy that counters the therapeutic effect of endoxifen and AKT inhibitors.Therefore,our results indicate increased activation of AKT and AMPK with metabolic reprogramming and increased autophagy in TAM-resistant cells.Simultaneous inhibition of AKT and FAO/autophagy is necessary to fully sensitize resistant cells to endoxifen.展开更多
基金This work was supported in part by a grant from the National Cancer Institute(R01CA200232-05)a DoD breast cancer grant(11895064)to C.G.M.and by grants from National Heart,Lung,and Blood Institute(HL-057832,HL-132871,and HL-13A781)to LAB.
文摘Tamoxifen(TAM)is the first-line endocrine therapy for estrogen receptor-positive(ER+)breast cancer(BC).However,acquired resistance occurs in∼50%cases.Meanwhile,although the PI3K/AKT/mTOR pathway is a viable target for treatment of endocrine therapy-refractory patients,complex signaling feedback loops exist,which can counter the effectiveness of inhibitors of this pathway.Here,we analyzed signaling pathways and metabolism in ER+MCF7 BC cell line and their TAM-resistant derivatives that are co-resistant to endoxifen using immunoblotting,quantitative polymerase chain reaction,and the Agilent Seahorse XF Analyzer.We found that activation of AKT and the energy-sensing kinase AMPK was increased in TAM and endoxifen-resistant cells.Furthermore,ERRα/PGC-1βand their target genes MCAD and CPT-1 were increased and regulated by AMPK,which coincided with increased fatty acid oxidation(FAO)and autophagy in TAM-resistant cells.Inhibition of AKT feedback-activates AMPK and ERRα/PGC-1β-MCAD/CPT-1 with a consequent increase in FAO and autophagy that counters the therapeutic effect of endoxifen and AKT inhibitors.Therefore,our results indicate increased activation of AKT and AMPK with metabolic reprogramming and increased autophagy in TAM-resistant cells.Simultaneous inhibition of AKT and FAO/autophagy is necessary to fully sensitize resistant cells to endoxifen.
