Baillat Gilbert, Garrouste Francoise, Remacle-Bonnet Maryse, Marvaldi Jacques, Pommier Gilbert
ISPDCT (IPHM), FRE CNRS 2737, Université de la Méditerranée, Faculté de Pharmacie, 27 Bd. Jean Moulin, 13385 Marseille Cedex 5, France.
Biochim Biophys Acta. 2005 Aug 15;1745(1):101-10. doi: 10.1016/j.bbamcr.2004.12.005. Epub 2005 Jan 11.
Apoptosis is a crucial mechanism to eliminate harmful cells in which growth factors and cytokines are key regulators. In HT29-D4 cells, a model of human colon carcinoma, IFNgamma presensitization is essential to induce an apoptotic response to TNFalpha whereas it only slightly enhances TRAIL-induced apoptosis. To compare the transcriptional profiles induced by TNFalpha and TRAIL and their regulation by IFNgamma, we optimized a cDNA array analysis on targeted signaling pathways and confirmed the gene expression modulations by comparative RT-PCR. Although the two TNFSF ligands induced a same strong up-expression of pro-apoptotic Bax gene, the expression of anti-apoptotic Bcl-xL gene was more strongly up-regulated in TNFalpha- than in TRAIL-stimulated cells. Thus, TRAIL but not TNFalpha induced apoptotic mitochondrial cascade as highlighted by cytochrome c release into cytosol. IFNgamma presensitization of TRAIL-stimulated cells did not induce any change in cytochrome c release, suggesting that the increase of IFNgamma/TRAIL-induced apoptosis is independent of this pathway. In contrast, IFNgamma pretreatment prevented Bcl-xL gene up-expression in TNFalpha-stimulated cells and allowed cytochrome c release. Thus, we hypothesize that the Bcl-xL/Bax ratio can block the apoptotic response in TNFalpha-stimulated cells but allows cell death initiation when it is altered by a crosstalk between IFNgamma presensitization and TNFalpha induced signalings.
细胞凋亡是消除有害细胞的关键机制，其中生长因子和细胞因子是关键调节因子。在人结肠癌模型HT29-D4细胞中，γ干扰素预致敏对于诱导对肿瘤坏死因子α的凋亡反应至关重要，而它仅略微增强肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导的凋亡。为了比较肿瘤坏死因子α和TRAIL诱导的转录谱及其受γ干扰素的调节，我们优化了针对靶向信号通路的cDNA阵列分析，并通过比较逆转录聚合酶链反应（RT-PCR）证实了基因表达的调节。尽管这两种肿瘤坏死因子超家族（TNFSF）配体均诱导促凋亡的Bax基因强烈上调表达，但在肿瘤坏死因子α刺激的细胞中，抗凋亡的Bcl-xL基因的表达上调比TRAIL刺激的细胞中更强。因此，如细胞色素c释放到细胞质中所突出显示的，TRAIL而非肿瘤坏死因子α诱导凋亡线粒体级联反应。TRAIL刺激细胞的γ干扰素预致敏并未诱导细胞色素c释放的任何变化，这表明γ干扰素/TRAIL诱导的凋亡增加与该途径无关。相反，γ干扰素预处理可防止肿瘤坏死因子α刺激的细胞中Bcl-xL基因上调表达，并允许细胞色素c释放。因此，我们推测Bcl-xL/Bax比率可阻断肿瘤坏死因子α刺激的细胞中的凋亡反应，但当它因γ干扰素预致敏和肿瘤坏死因子α诱导的信号之间的串扰而改变时，则允许细胞死亡启动。
