To evaluate the effect of FOXP3 on the expression of MTA1 and on breast cancer metastasis in vivo, a lentiviral infection strategy was used to generate MDA-MB-231 cells overexpressing FOXP3 (MDA-MB-231-LUC2-FOXP3), MDA-MB-231 cells stably overexpressing FOXP3 and MTA1 (MDA-MB-LUC2-FOXP3-MTA1) and the corresponding negative control cells (MDA-MB-231-LUC2-Vector). This evidence concerns the gene FOXP3 and breast cancer.