Apoptosis of human hepatoma cell lines induced by transforming growth factor beta 1 (TGF-β1) correlates with p53 and Smad4 activation
WANG Chun-lei, WAN Yuan-lian , LIU Yu-cun , HUANG Zhi-qiang Department of General Surgery, Peking University First Hospital, Beijing 100034, China Institute of Hepatobiliary Surgery, PLA General Hospital
Objective: To determine the relationships between apoptosis induced by transforming growth factor beta 1 (TGF-Bl ) 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-β1-induced apoptosis in hepatic carcinoma cell lines was quantitated using the terminal deoxynucle-otidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. For identification of the mechanism of apoptosis induced by TGF-Bl , these cell lines were transfected with a TGF-β1-inducible luciferase reporter plasmid containing Smad binding elements ( SBE) and luciferase gene using LF2000, then were treated with TGF-β1. Relative luciferase activity was assayed respectively. Results:Among three cell lines studied with TUNEL assay, addition of TGF-β1 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-β1 induction, Huh-7 and Hep3B cell lines significantly lowered luciferase expression. Conclusion:HepG2 cells were highly susceptible to TGF-β1-induced apoptosis compared with Hep3B and Huh-7 cell lines. Smad4 may be a central mediator of the TGF-Bl signaling transdution pathway.