Choi Chulhee, Jeong Eunjoo, Benveniste Etty N
Division of Molecular Life Sciences and Center for Cell Signaling Research, Ewha Womans University, Seoul, Korea.
J Neurooncol. 2004 Mar-Apr;67(1-2):167-76. doi: 10.1023/b:neon.0000021896.52664.9e.
Resistance to Fas-mediated apoptosis contributes to tumor evasion from the host immune system and enables tumors to mediate alternative responses such as inflammation and angiogenesis. In this study, we investigated the molecular mechanisms of the resistance to Fas-mediated apoptosis and sensitization to Fas-induced cell death by IFN-gamma in human astrocytoma cells. To address this, we investigated the expression of thirty-three genes related to the Fas signal transduction pathways using RNase protection assay in five different human astrocytoma cells. Patterns of expression of these genes were similar between different cell lines and did not correlate with sensitivity to Fas-mediated cell death. Treatment with IFN-gamma increased the mRNA expression of caspases-1, -4 and -7 in addition to those of Fas and TRAIL in a time- and dose-dependent manner. Studies using specific caspase inhibitors showed that Fas-induced cell death was mediated by caspases-1, -3 and 8 in the Fas-sensitive human astrocytoma cell lines, CRT-J and U87-MG. We further demonstrated that these caspases were proteolytically cleaved upon Fas ligation in these cells. Interestingly, caspase-1 protein expression but not that of caspase-3 nor -8 was up-regulated by IFN-gamma only in Fas-sensitive CRT-J cells but not in Fas-resistant U373-MG cells. These results collectively suggest that caspase-1, along with caspases-3 and -8, mediate Fas-induced cell death in human astrocytoma cells, and post-transcriptional regulation of caspase-1 may determine the responsiveness to IFN-gamma-induced sensitization to Fas-mediated apoptosis.
对Fas介导的细胞凋亡的抗性有助于肿瘤逃避免疫系统，并使肿瘤能够介导诸如炎症和血管生成等其他反应。在本研究中，我们调查了人星形细胞瘤细胞中对Fas介导的细胞凋亡的抗性以及对IFN-γ诱导的Fas诱导细胞死亡的敏感性的分子机制。为了解决这个问题，我们使用核糖核酸酶保护试验在五种不同的人星形细胞瘤细胞中研究了与Fas信号转导途径相关的33个基因的表达。这些基因在不同细胞系之间的表达模式相似，并且与对Fas介导的细胞死亡的敏感性无关。IFN-γ处理以时间和剂量依赖性方式增加了caspases-1、-4和-7以及Fas和TRAIL的mRNA表达。使用特异性caspase抑制剂的研究表明，在Fas敏感的人星形细胞瘤细胞系CRT-J和U87-MG中，Fas诱导的细胞死亡由caspases-1、-3和8介导。我们进一步证明，在这些细胞中，Fas连接后这些caspases会被蛋白水解切割。有趣的是，仅在Fas敏感的CRT-J细胞中，IFN-γ上调了caspase-1蛋白表达，而在Fas抗性的U373-MG细胞中未上调caspase-3和-8的蛋白表达。这些结果共同表明，caspase-1与caspases-3和-8一起介导人星形细胞瘤细胞中Fas诱导的细胞死亡，并且caspase-1的转录后调节可能决定对IFN-γ诱导的对Fas介导的细胞凋亡的敏感性。
