Effects Of GPER-mediated Remodeling Of Glutamine Metabolism On Tamoxifen Resistance In Breast Cancer

Objective:To investigate the effect of G protein-coupled estrogen receptor（GPER）-mediated glutamine metabolism on the resistance of tamoxifen（TAM）for ER⁺breast cancer and its mechanisms.Methods:qRT-PCR and Western Blot were used to detect the expression of glutaminase（GLS1）in ER+breast cancer cells MCF-7 and TAM-resistant cells MCF-7R.TAM、GPER inhibitor G36+TAM and GPER agonist G1 were added to treat MCF-7R,Western Blot was used to detect the activation of PI3K/Akt signaling pathway and the expression of GLS1.The PI3k/AKT pathway inhibitor LY294002 was added to MCF-7R,and the expression of GLS1 was detected by Western Blot.MCF-7R cells were transfected with shGPER lentivirus to establish a MCF-7R/shGPER model of breast cancer TAM-tolerant cells targeting GPER expression.The expression of GLS1 and p-Akt after GPER gene interference was detected by qRT-PCR and Western Blot.The glutamine and Mito-tracker green were used to detect glutamine metabolism and mitochondrial activity in MCF-7R/shCtrl and MCF-7R/sh GPER cells treated with GPER modulators,respectively.MCF-7R were treated with TAM and BPTES+TAM,and cell apoptosis was measured by CCK-8 kit and IC₅₀0 was calculated.Results:1.qRT-PCR and Western Blot verify that TAM and G1induce the activation of GPER,activate the PI3K/Akt signaling pathway and regulate the downstream GLS1 expression;G36,LY294002 and shGPER inhibit the expression of GLS1 gene induced by TAM and G1.2.Treated with TAM,glutamine uptake and?-ketoglutarate production and mitochondrial activity was increased in MCF-7R;and treated with BPTES+TAM,glutamine uptake and?-ketoglutarate production and mitochondrial activity was decreased,apoptosis increased,and the sensitivity to TAM recovered in MCF-7R.Conclusion:TAM as an agonist of GPER in ER+breast cancer cells,activating the PI3K/Akt signaling pathway,promoting GLS1 expression,enhancing glutamine metabolism and the activity of mitochondrial,promotes TAM risistance in breast cancer cells.Inhibits GPER expression or PI3K/Akt pathway can down-regulate GLS1 expression,attenuating glutamine metabolism and mitochondrial activity,and promote recovery the sensitivity to TAM.GPER-mediated changes in glutamine metabolism play an important role in drug resistance.