SMAD3 and cancer: In addition, the phosphorylated Smad3 (Ser423/425)), a key factor in TGF-β1 signaling, significantly increased at 8 h after TGF-β1 treatment and disappeared after 48 h (Figure 2A,C), suggesting that the early activation of Smad signaling is essential for TGF-β1-induced EMT in this cancer cell as shown previously [8,10,14].