转化生长因子β1(TGF-β1)诱导人肝癌细胞系的凋亡与p53及Smad4活化相关

目的:明确转化生长因子β1(TGF-β1)诱导人肝肿瘤细胞系凋亡及其与Smad的关系.方法:选用3种含有不同p53基因状态的人肝肿瘤细胞系,应用脱氧核糖核苷酸末端转移酶介导的dUTP缺口末端标记技术(TUNEL)对TGF-β1诱导的肝肿瘤细胞的凋亡进行了定量检测.为明确凋亡机制,还应用LF2000把含有Smad结合元件和荧光素酶基因的TGF-β1可诱导的荧光素酶报告质粒对细胞进行了转染,后经TGF-β1作用,分别检测其相对荧光素酶活性.结果:在应用TUNEL检测的3个细胞系中,TGF-β1仅能诱导HepG2细胞(野生型p53)凋亡,而Huh-7(突变型p53)和Hep3B细胞(缺失型p53)则凋亡较少.荧光素酶检测显示,HepG2细胞对TGF-β1反应较强,而Huh-7和Hep3B细胞其荧光素酶的表达较低.结论:HepG2细胞系比Huh-7和Hep3B细胞系更易发生TGF-β1诱导的凋亡,Smad4也许是TGF-β1信号转导途径的主要调控因子之一.

Apoptosis of human hepatoma cell lines induced by transforming growth factor beta 1 (TGF-β1) correlates with p53 and Smad4 activation

Objective: To determine the relationships between apoptosis induced by transforming growth factor beta 1 (TGF-β1) 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 deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. For identification of the mechanism of apoptosis induced by TGF-β1, 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: HepG2cells 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-β1 signaling transdution pathway.