Objective To determine whether transforming growth factor betal (TGF-β1)/Smad signaling pathway mediates p53-dependent apoptosis in hepatoma cell lines.Methods Three human hepatic carcinoma cell lines, HepG2, Huh-7, and Hep3B, were used in this study.TGF-β1-induced apoptosis in hepatic carcinoma cell lines was analyzed using TUNEL assay.For identifying the mechanism of apoptosis induced by TGF-β1, cell lines were transfected with a TGF-β1-inducible luciferase reportor plasmid containing Smad4 binding elements.After transfection, cells were treated with TGF-β1, then assayed for luciferase activity.Results The apoptosis rate of HepG2 cell lines (48.51%± 8.21%) was significantly higher than control ( 12.72%±2.18%, P<0.05).But TGF-β1 was not able to induce apoptosis of Huh-7 and Hep3B cell lines.The relative luciferase activity of TGF-β1-treated HepG2 cell lines (4.38) was significantly higher than control (1.00, P< 0.05).But the relative luciferase activity of TGF-β1-treated Huh-7 and Hep3B cell lines less increased compared with control.Conclusions HepG2 cells seem to be highly susceptible to TGF-β1-induced apoptosis compared with Hep3B and Huh-7 cell lines.Smad4 is a central mediator of TGF-β1 signaling transdution pathway.TGF-β1/Smad signaling pathway might mediate p53-dependent apoptosis in hepatoma cell lines. Objective To determine whether transforming growth factor betal (TGF-β1) / Smad signaling pathway mediates p53-dependent apoptosis in hepatoma cell lines. Methods Three human hepatic carcinoma cell lines, HepG2, Huh-7, and Hep3B, were used in this study. TGF-β1-induced apoptosis in hepatic carcinoma cell lines was analyzed using TUNEL assay. The mechanism of apoptosis induced by TGF-β1, cell lines were transfected with a TGF-β1-inducible luciferase reporter containing plasmid containing Smad4 binding elements. After transfection , cells were treated with TGF-β1 and then assayed for luciferase activity. Results The apoptosis rate of HepG2 cell lines (48.51% ± 8.21%) was significantly higher than control (12.72 ± 2.18%, P <0.05) β1 was not able to induce apoptosis of Huh-7 and Hep3B cell lines. The relative luciferase activity of TGF-β1-treated HepG2 cell lines (4.38) was significantly higher than control (1.00, P <0.05) .But the relative luciferase activity of TGF-β1-treated Huh -7 and Hep3B cell lines less increased compared with control. Conclusions HepG2 cells seem to be highly susceptible to TGF-β1-induced apoptosis compared with Hep3B and Huh-7 cell lines. Smad4 is a central mediator of TGF-β1 signaling transduction pathway. TGF-β1 / Smad signaling pathway might mediate p53-dependent apoptosis in hepatoma cell lines.