Effect Of Estrogen Dependent MICALL2 On The Sensitivity Of ER+ Breast Cancer Cells To Tamoxifen Therapy

ObjectiveTo explore the mechanism of estrogen regulating the expression of MICALL2 in estrogen receptor positive(ER+)breast cancer cells,and the role of MICALL2 in ER+ breast cancer cells’ sensitivity to tamoxifen,and to further study the possible mechanism of MICALL2’s role in this type of breast cancer.Methods(1)Immunohistochemical staining analysis of MICALL2 expression in ER+breast cancer.(2)QRT PCR and Western blot were used to detect the effect of estrogen on MICALL2 expression in ER+ breast cancer cells.At the same time,the effect of estrogen stimulation on the binding of MICALL2 and ESR1 was detected by double luciferase reporter gene experiment.CCK8 proliferation experiment was used to explore the effect of MICALL2 on tamoxifen sensitivity in breast cancer cells.(3)Transcriptome sequencing and gene set enrichment analysis were used to find the signal pathway closely related to MICALL2,and Western blot was used to detect the expression of MICALL2 on related signal pathway molecules.Results(1)Immunohistochemical staining results showed that compared with ER-breast cancer tissue,MICALL2 expression in ER+ breast cancer tissue was increased,which was consistent with the analysis results of breast cancer tumor database;At the same time,the high expression of MICALL2 is closely related to the low survival rate of ER+ breast cancer patients.(2)The results of qRT PCR and Western blot showed that estrogen stimulation significantly increased the mRNA and protein levels of MICALL2 in ER+breast cancer cells in a dose-dependent manner,on the contrary,this phenomenon was not found in ER cells;The results of the double luciferase reporter gene experiment showed that the luciferase activity of the recombinant MICALL2 promoter increased in the estrogen-treated MCF-7and T47 D cells.(3)CCK8 results showed that silencing MICALL2 increased the sensitivity to tamoxifen.(4)RNA seq analysis,gene enrichment analysis and Western blot results showed that In ER+ breast cancer cells,compared with shCtr in the control group,the expression levels of p-AKT,p-mTOR of MICALL2 silenced cells were significantly reduced,indicating that MICALL2 may reduce the sensitivity of breast cancer cells to tamoxifen by activating PI3K/AKT/mTOR signaling pathway,thus exerting its biological function.Conclusions MICALL2,as the estrogen response gene of ER+ breast cancer cells,may reduce the sensitivity to tamoxifen by activating PI3K/AKT/mTOR signaling pathway.