TGFB1 and breast cancer: TGFBR1 expression plasmids were co-transfected into TGFBR1-null mouse embryonic fibroblasts30 and TGFBR2 expression plasmids were co-transfected into TGFBR2-null T47D breast cancer cells, in addition to the TGFβ-responsive reporter construct SMAD7-Promoter Luciferase31 (Fig. 4a and b, respectively).