E2F-1在胃腺癌细胞内质网应激反应中对Mcl-1的调控作用

Regulation of Mcl-1 by E2F-1 in endoplasmic reticulum stress in gastric adenocarcinoma cells

目的探讨Mcl-1在胃腺癌细胞对内质网应激诱导细胞凋亡耐受中的作用,以及内质网应激状态下E2F-1调控Mcl-1的机制。方法采用PI单染法测定细胞凋亡率;Western blot检测GRP78、Mcl-1、Bcl-2、E2F-1蛋白变化;实时荧光定量PCR检测Mcl-1 mRNA水平变化;转染pcDNA-E2F-1-Flag质粒使细胞高表达E2F-1。结果胃腺癌细胞对衣霉素(TM)诱导的内质网应激性凋亡相对不敏感,这与Mcl-1在蛋白水平和mRNA水平的上调有关。Mcl-1的转录抑制因子E2F-1在TM诱导细胞后表达下调。在内质网应激状态下的胃腺癌细胞中高表达E2F-1可以减弱Mcl-1的上调。结论内质网应激反应引起Mcl-1上调可能在胃腺癌细胞对内质网应激诱导的凋亡耐受中起重要作用;转录因子E2F-1下调可能参与调控Mcl-1的表达。

Objective To explore the role of Mcl-1 in resistance of gastric adenocarcinoma cells to endoplasmic reticulum（ER） stress-induced apoptosis and the mechanism of regulation of Mcl-1 by E2F-1 in the cells under ER stress.Methods Apoptosis was measured by flow cytometry using propidium iodide staining.Western blot was used to detect expression levels of various proteins including GRP78,Mcl-1,Bcl-2 and E2F-1.The expression of Mcl-1 at mRNA level was monitored by quantitative RT-PCR.cDNA（pcDNA-E2F-1-Flag）transfection was employed to over-express E2F-1 in cells.Results Gastric adenocarcinoma cells were in general resistant to apoptosis induced by the ER-stress inducer tunicymicin（TM） which was associated with up-regulation of Mcl-1 in protein and mRNA levels.Intriguingly,the transcription factor E2F-1 known to repress transcription of Mcl-1 was decreased by exposure to TM.Over-expression of E2F-1 attenuated up-regulation of Mcl-1 in gastric adenocarcinoma cells under ER stress.Conclusion Up-regulation of Mcl-1 may play a role in resistance of gastric adenocarcinoma cells to ER stress-induced apoptosis.This is,at least in part,due to down-regulation of E2F-1 in the cells upon ER stress.