Tunicamycin sensitizes human melanoma cells to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by up-regulation of TRAIL-R2 via the unfolded protein response
Tunicamycin sensitizes human melanoma cells to tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis by up-regulation of TRAIL-R2 via the unfolded protein response
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DOI：
10.1158/0008-5472.can-07-0213
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发表时间：
2007-06-15
期刊：
影响因子：
11.2
通讯作者：
Hersey, Peter
中科院分区：
文献类型：
--
作者：
Jiang, Chen Chen;Chen, Li Hua;Hersey, Peter
我们以前曾报道过肿瘤坏死因子（TNF）相关的凋亡诱导配体（TRAIL）的死亡受体在新鲜的分离株和组织切片的黑色素瘤的低表达。这似乎与新鲜分离的黑色素瘤细胞对TRAIL诱导的细胞凋亡的相对抗性相关。我们在这项研究中表明，内质网（ER）应激诱导剂，衣霉素，选择性上调TRAIL-R2的细胞表面表达，但不是其他成员的TNF受体家族，并增强TRAIL诱导的细胞凋亡在培养的黑色素瘤细胞和新鲜的黑色素瘤分离株。衣霉素介导的黑色素瘤细胞对TRAIL诱导的细胞凋亡的敏感性与caspase级联反应的激活增加和线粒体膜电位的降低相关，并被重组TRAIL-R2/Fc嵌合蛋白抑制。TRAIL-R2在黑色素瘤细胞表面的上调与TRAIL-R2的转录及其总蛋白水平的增加相关。内质网应激诱导的未折叠蛋白反应的两个信号通路介导的肌醇需要的跨膜激酶和核酸内切酶1 α（IRE1 α）和转录因子6（ATF 6）的激活，分别参与。在一个黑色素瘤细胞系中，有明确的证据表明IRE1 α通路被激活，并且IRE1 α的小干扰RNA（siRNA）敲低显著降低了TRAIL-R2的上调。类似地，有证据表明ATF6通路的激活，并且ATF6的siRNA敲低对一种而不是另一种黑素瘤细胞系中的TRAIL-112表达具有延迟效应。此外，转录因子CCAAT/增强子结合蛋白同源蛋白似乎参与了衣霉素对TRAIL-112的上调，但其作用在不同的黑色素瘤细胞系之间存在差异。总之，我们的结果表明，诱导ER应激的药物可能会增强TRAIL-R2的表达，并增加对黑色素瘤中TRAIL的治疗反应。
We have reported previously low expression of death receptors for tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) in fresh isolates and tissue sections of melanoma. This seemed to correlate with relative resistance of freshly isolated melanoma cells to TRAIL-induced apoptosis. We show in this study that the endoplasmic reticulum (ER) stress inducer, tunicamycin, selectively up-regulated the cell surface expression of TRAIL-R2, but not other members of the TNF receptor family, and enhanced TRAIL-induced apoptosis in cultured melanoma cells and fresh melanoma isolates. Tunicamycin-mediated sensitization of melanoma cells to TRAIL-induced apoptosis was associated with increased activation of the caspase cascade and reduction in mitochondrial membrane potential and was inhibited by a recombinant TRAIL-R2/Fc chimeric protein. Up-regulation of TRAIL-R2 on the melanoma cell surface was associated with increased transcription of TRAIL-R2 and its total protein levels. Two signaling pathways of the ER stress-induced unfolded protein response mediated by inositol-requiring transmembrane kinase and endonuclease 1 alpha (IRE1 alpha) and activation of transcription factor 6 (ATF6), respectively, seemed to be involved. In one melanoma line, there was clear evidence of activation of the IRE1 alpha pathway, and small interfering RNA (siRNA) knockdown of IRE1 alpha substantially reduced the up-regulation of TRAIL-R2. Similarly, there was evidence for the activation of the ATF6 pathway, and siRNA knockdown of ATF6 had a delayed effect on TRAIL-112 expression in one but not another melanoma cell line. Moreover, the transcription factor CCAAT/enhancer-binding protein homologous protein seemed to be involved in the up-regulation of TRAIL-112 by tunicamycin, but its role varied between different melanoma lines. Taken together, our results suggest that agents that induce ER stress may enhance TRAIL-R2 expression and increase the therapeutic response to TRAIL in melanoma.