FOXP3 Inhibits The Metastasis Of Breast Cancer By Down-regulating The Expression Of MTA1

BackgroundFOXP3,a member of the forkhead/wing helical transcription factor family,has been once considered to be a marker of regulatory T cells(Treg).FOXP3 can regulate the differentiation and development of Treg cells and maintain their cellular function.Recent studies have shown that FOXP3 is also expressed in epithelial cells of breast,ovary,prostate and other tissues.Compared with normal mammary epithelial cells,the expression of FOXP3 in breast cancer is significantly decreased.FOXP3 regulates the expression of tumor-related genes to play a role in inhibiting cancer.FOXP3 inhibits the transcription of the oncogene SKP2 to block cell division in breast cancer,promotes the expression of p21 to regulate cell cycle and inhibit cell proliferation,and negatively regulates the NF-κb signaling pathway to promote apoptosis.However,most studies have focused on the role of FOXP3 in inhibiting the proliferation of breast cancer,but few have focused on the relationship between FOXP3 and breast cancer metastasis.AimsThis study intends to explore new FOXP3 downstream molecules and elucidate the mechanism of FOXP3 in inhibiting breast cancer metastasis through cytological experiments in vitro,animal experiments in vivo and analysis of clinical samples of breast cancer,so as to provide an experimental basis and new ideas for the treatment of breast cancer metastasis.Methods1.MCF7 cells overexpressing FOXP3 were constructed for high-throughput transcriptome sequencing and differential gene expression analysis,so as to screen potential downstream molecules of FOXP3.2.Breast cancer cells overexpressing or silencing FOXP3 were constructed and verified the function of FOXP3 in inhibiting MTA1 expression at m RNA and protein levels by realtime PCR and Western blot experiments.3.Bioinformatics was used to predict the interacting sites of FOXP3 and gene promoter,and the interaction was verified by Ch IP experiment.4.Reporter plasmid containing MTA1 promoter was constructed,and the effect of FOXP3 on the transcriptional activity of MTA1 promoter was analyzed by double luciferase reporter gene experiment.5.After changing the expression levels of FOXP3 and MTA1 in breast cancer cells,Transwell and cell scratch experiments were used to analyze whether the regulation of FOXP3 on MTA1 affected the invasion and migration of breast cancer cells.6.MDA-MB-231 cells stably overexpressing FOXP3 alone as well as FOXP3 and MTA1 simultaneously were constructed,and lung metastasis model was constructed in nude mice by caudal vein injection,so as to verify the function of FOXP3 regulating MTA1 expression in lung metastasis of breast cancer cells in vivo.7.The expression of FOXP3 and MTA1 in 92 cases of breast cancer samples was detected by immunohistochemistry,and the correlation of the expression level of FOXP3 and MTA1 with clinical stage and lymph node metastasis was analyzed.8.The correlation between FOXP3 and MTA1 expression levels was verified in a large number of breast cancer clinical data provided by the public database.Results1.Transcriptome sequencing suggested that MTA1 is a potential downstream molecule of FOXP3.2.After overexpressing FOXP3 in breast cancer cells,the expression level of MTA1 decreased.After interfering with the expression of FOXP3,the expression level of MTA1 increased.3.FOXP3 could bind to the specific sites on the MTA1 promoter.4.FOXP3 inhibited the transcriptional activity of MTA1 promoter.5.FOXP3 could inhibit the invasion and migration of breast cancer cells.6.FOXP3 could inhibit the lung metastasis of breast cancer cells through regulating the expression level of MTA1.7.Clinical specimens showed a negative correlation between the expression levels of FOXP3 and MTA1 in breast cancer.Also,the clinical stage and lymph node metastasis of the tumor were negatively correlated with the expression level of FOXP3 and were positively correlated with the expression level of MTA1.8.Data from the public database showed a negative correlation between FOXP3 and MTA1 expression levels in clinical breast cancer samples.Conclusion1.This study confirmed the inhibitory effect of FOXP3 on MTA1 at m RNA and protein levels.2.FOXP3 could bind to the specific sequences of MTA1 promoter to inhibit the transcriptional activity of MTA1 promoter.3.FOXP3 could inhibit the metastasis of breast cancer cells in vitro and in vivo by regulating the expression level of MTA1.4.There were a negative correlation between the expression levels of FOXP3 and MTA1 in clinical breast cancer samples.