Delhalle Sylvie, Deregowski Valérie, Benoit Valérie, Merville Marie-Paule, Bours Vincent
Laboratory of Medical Chemistry and Human Genetics, Center for Cellular and Molecular Therapy, CHU B35, Sart-Tilman, University of Liège, 4000 Liège, Belgium..
Oncogene. 2002 May 30;21(24):3917-24. doi: 10.1038/sj.onc.1205489.
NF-kappaB is known to exert a cytoprotective action against TNF-alpha-induced apoptosis. To study the role of NF-kappaB in various TNF-alpha-treated epithelial cell lines, we generated stable transfectants overexpressing a mutated unresponsive form of the IkappaBalpha inhibitor (MT cells). As NF-kappaB prevented TNF-alpha-induced apoptosis in various epithelial cancer cell lines, we searched for NF-kappaB target gene products responsible for this difference of sensitivity. We observed an increased Bcl-X(L) expression level in OVCAR-3 cells compared with OVCAR-3 cells expressing a mutated IkappaBalpha inhibitor (MT cells). Induction of the antioxidant enzyme MnSOD was detected only in TNF-alpha-treated OVCAR, MCF7A/Z and HCT116 cells but not in MT cells. Moreover, reactive oxygen species were involved in TNF-alpha-induced apoptosis, as various antioxidants partially protected these cells from apoptosis. At last, transfection of the MnSOD cDNA in MT cells, which do not express this protein after TNF-alpha stimulation, partially restored resistance to TNF-alpha-induced cell death, as observed by clonogenic assays. However, transfection of the Bcl-X(L) cDNA did not induce any protective effect. Therefore, MnSOD expression is induced by NF-kappaB in epithelial cancer cells in response to TNF-alpha, and is at least partially responsible for their resistance to TNF-alpha-induced apoptosis, presumably through the clearance of death-inducing ROS.
已知核因子-κB（NF-κB）对肿瘤坏死因子-α（TNF-α）诱导的细胞凋亡具有细胞保护作用。为了研究NF-κB在多种经TNF-α处理的上皮细胞系中的作用，我们构建了稳定转染细胞系，使其过表达一种突变的无反应形式的核因子-κB抑制蛋白α（IκBα）（MT细胞）。由于NF-κB可防止TNF-α诱导多种上皮癌细胞系发生凋亡，我们寻找了导致这种敏感性差异的NF-κB靶基因产物。我们观察到，与表达突变的IκBα抑制蛋白（MT细胞）的OVCAR-3细胞相比，OVCAR-3细胞中Bcl-X(L)表达水平升高。仅在经TNF-α处理的OVCAR、MCF7A/Z和HCT116细胞中检测到抗氧化酶锰超氧化物歧化酶（MnSOD）的诱导，而在MT细胞中未检测到。此外，活性氧参与了TNF-α诱导的细胞凋亡，因为多种抗氧化剂可部分保护这些细胞免于凋亡。最后，通过克隆形成试验观察到，在TNF-α刺激后不表达该蛋白的MT细胞中转染MnSOD cDNA，可部分恢复对TNF-α诱导的细胞死亡的抗性。然而，转染Bcl-X(L) cDNA未诱导任何保护作用。因此，在上皮癌细胞中，NF-κB可响应TNF-α诱导MnSOD表达，并且至少部分负责其对TNF-α诱导的细胞凋亡的抗性，推测是通过清除诱导死亡的活性氧实现的。
