TGFB1 and hepatocellular carcinoma: In HepG2 cells, the basal level of BAMBI activation was relatively high, while that of TGF-β1 was low, as previously observed in other HCC cases.10, 16 BAMBI is a transmembrane protein that lacks an intracellular kinase domain but has high sequence similarity to the extracellular domain of TβRI and thus inhibits TGF-β signaling by forming a heterodimer with TβRII.10 However, our data revealed that BAMBI also transcriptionally regulates TGF-β1 expression.