Apoptosis of human hepatoma cell lines induced by transforming growth factor beta 1 (TGF-beta1) correlates with p53 and Smad4 activation.

OBJECTIVE

To determine the relationships between apoptosis induced by transforming growth factor beta 1(TGF-beta1) and Smad in human hepatoma cell lines.

METHODS

Three human hepatic carcinoma cell lines, involving different status of the p53 gene respectively, were used in this study. TGF-beta1-induced apoptosis in hepatic carcinoma cell lines was quantitated using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. For identification of the mechanism of apoptosis induced by TGF-beta1, these cell lines were transfected with a TGF-beta1-inducible luciferase reporter plasmid containing Smad binding elements (SBE) and luciferase gene using LF2000, then were treated with TGF-beta1. Relative luciferase activity was assayed respectively.

RESULTS

Among three cell lines studied with TUNEL assay, addition of TGF-beta1 induced apoptosis only in HepG2 cells (wild type p53). In contrast, Huh-7 (mutant p53) and Hep3B (deleted p53) cell lines lacked apoptosis. The detection of luciferase activity indicated that HepG2 cells dramatically increased the response to TGF-beta1 induction, Huh-7 and Hep3B cell lines significantly lowered luciferase expression.

CONCLUSION

HepG2 cells were highly susceptible to TGF-beta1-induced apoptosis compared with Hep3B and Huh-7 cell lines. Smad4 may be a central mediator of the TGF-beta1 signaling transduction pathway.