Kim Eun Hee, Yoon Mi Jin, Kim Seung U, Kwon Taeg Kyu, Sohn Seonghyang, Choi Kyeong Sook
Department of Molecular Science and Technology, Institute for Medical Sciences, Ajou University School of Medicine, Suwon, Korea.
Cancer Res. 2008 Jan 1;68(1):266-75. doi: 10.1158/0008-5472.CAN-07-2444.
The current study shows that treatment of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistant glioma cells with a combination of TRAIL and subtoxic doses of arsenic trioxide (As(2)O(3)) induces rapid apoptosis. Whereas TRAIL-mediated proteolytic processing of procaspase-3 was partially blocked in glioma cells, treatment with As(2)O(3) efficiently recovered TRAIL-induced activation of caspases. We also found that As(2)O(3) treatment of glioma cells significantly up-regulated DR5, a death receptor of TRAIL. Furthermore, suppression of DR5 expression by small interfering RNA (siRNA) inhibited As(2)O(3)/TRAIL-induced apoptosis of U87MG glioma cells, suggesting that DR5 up-regulation is critical for As(2)O(3)-induced sensitization of glioma cells to TRAIL-mediated apoptosis. Our results also indicate that an increase in CCAAT/enhancer binding protein homologous protein (CHOP) protein levels precedes As(2)O(3)-induced DR5 up-regulation. The involvement of CHOP in this process was confirmed by siRNA-mediated CHOP suppression, which not only attenuated As(2)O(3)-induced DR5 up-regulation but also inhibited the As(2)O(3)-stimulated TRAIL-induced apoptosis. These results therefore suggest that the CHOP-mediated DR5 up-regulation, brought about by As(2)O(3), stimulates the TRAIL-mediated signaling pathway. This in turn leads to complete proteolytic processing of caspase-3, which is partially primed by TRAIL in glioma cells. In contrast to human glioma cells, astrocytes were very resistant to the combined administration of As(2)O(3) and TRAIL, demonstrating the safety of this treatment. In addition, As(2)O(3)-mediated up-regulation of CHOP and DR5, as well as partial proteolytic processing of procaspase-3 by TRAIL, was not induced in astrocytes. Taken together, the present results suggest that the combined treatment of glioma cells with As(2)O(3) plus TRAIL may provide an effective and selective therapeutic strategy.
当前研究表明，用肿瘤坏死因子相关凋亡诱导配体（TRAIL）和亚毒性剂量的三氧化二砷（As₂O₃）联合处理对TRAIL耐药的胶质瘤细胞可诱导快速凋亡。虽然在胶质瘤细胞中TRAIL介导的procaspase-3蛋白水解加工被部分阻断，但用As₂O₃处理可有效恢复TRAIL诱导的半胱天冬酶激活。我们还发现，用As₂O₃处理胶质瘤细胞可显著上调TRAIL的死亡受体DR5。此外，小干扰RNA（siRNA）抑制DR5表达可抑制As₂O₃/TRAIL诱导的U87MG胶质瘤细胞凋亡，这表明DR5上调对于As₂O₃诱导胶质瘤细胞对TRAIL介导的凋亡敏感至关重要。我们的结果还表明，CCAAT/增强子结合蛋白同源蛋白（CHOP）蛋白水平升高先于As₂O₃诱导的DR5上调。siRNA介导的CHOP抑制证实了CHOP参与这一过程，这不仅减弱了As₂O₃诱导的DR5上调，还抑制了As₂O₃刺激的TRAIL诱导的凋亡。因此，这些结果表明，As₂O₃引起的CHOP介导的DR5上调刺激了TRAIL介导的信号通路。这进而导致caspase-3的完全蛋白水解加工，而在胶质瘤细胞中TRAIL可部分启动这一过程。与人类胶质瘤细胞相反，星形胶质细胞对As₂O₃和TRAIL联合给药具有很强的抗性，这证明了这种治疗方法的安全性。此外，在星形胶质细胞中未诱导出As₂O₃介导的CHOP和DR5上调，以及TRAIL对procaspase-3的部分蛋白水解加工。综上所述，目前的结果表明，用As₂O₃加TRAIL联合治疗胶质瘤细胞可能提供一种有效且选择性的治疗策略。
