ESR1 and breast cancer: The immune suppressive function of FOXP3 + T cells in ER + breast cancers was further shown in the meta-analysis study, in which high tumor-infiltrating FOXP3 + T cells had shorter OS in the ER + (HR 0.86; 95% CI 0.77 − 0.96; p = 0.009), but not in the ER− (HR, 1.09; 95% CI 0.82−1.45; p = 0.569) breast cancers [20].