SMAD4 and hepatocellular carcinoma: In the course of ferroptosis in hepatocellular carcinoma cells, TGFβ1 restricts the expression of SLC7A11; therefore, it drives the vulnerability of hepatocellular carcinoma cells to ferroptosis, which can be prevented by Smad3, but not by Smad2 or Smad4, revealing the involvement of the TGFβ1-Smad3 signaling pathway in ferroptosis (Kim et al., 2020).