AFP and hepatocellular carcinoma: Consistent with the observation that TGFβ signaling suppresses AFP and DLK1 in rat fetal hepatocytes and HCC cells20,21, TGFBRT204D expression in HepG2 cells indeed decreased the levels of AFP and DLK1 mRNAs; Smad2/3 knockout rescued GREB1 knockdown-induced decrease in AFP expression (Supplementary Fig. 4f–h).