Small molecular TGF-β type 1 receptor (TKRI) reduce expression of phosphoylated (p)Smad2. pSmad2 expression of MDA-MB-231 cells that were not treated for 5 days post implantation (dpi), and then were treated for 1 h with (A) vehicle or (B) SB-431542. The SB-431542-treated cells were negative for TKRI activation. Data are representative of three independent experiments with at least 50 embryos per group. Scale bar = 100 μm.