TGFB1 and breast cancer: The suppressive function of (i)Tregs induced by BC-derived cells with S1P1 overexpression was sharply stronger than that of (i)Tregs induced by shControl-treated BC-derived cells, whereas the suppressive function of (i)Tregs induced by BC-derived cells following the administration of shS1P1 or TGF-β antibody was weaker than that of (i)Tregs induced by shControl-treated BC-derived cells (Fig. 2d and fig. S1c).