Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstr. 3a, 60528 Frankfurt, Germany.
Cell Death Dis. 2013 Nov 28;4(11):e936. doi: 10.1038/cddis.2013.457.
Smac mimetic promotes apoptosis by neutralizing inhibitor of apoptosis (IAP) proteins and is considered as a promising cancer therapeutic. Although an autocrine/paracrine tumor necrosis factor-α (TNFα) loop has been implicated in Smac mimetic-induced cell death, little is yet known about additional factors that determine sensitivity to Smac mimetic. Using genome-wide gene expression analysis, we identify death receptor 5 (DR5) as a novel key mediator of Smac mimetic-induced apoptosis. Although several cell lines that are sensitive to the Smac mimetic BV6 die in a TNFα-dependent manner, A172 glioblastoma cells undergo BV6-induced apoptosis largely independently of TNFα/TNFR1, as the TNFα-blocking antibody Enbrel or TNFR1 knockdown provide little protection. Yet, BV6-stimulated nuclear factor-κB (NF-κB) activation is critically required for apoptosis, as inhibition of NF-κB by overexpression of dominant-negative IκBα superrepressor (IκBα-SR) blocks BV6-induced apoptosis. Unbiased genome-wide gene expression studies in IκBα-SR-overexpressing cells versus vector control cells reveal that BV6 increases DR5 expression in a NF-κB-dependent manner. Importantly, this BV6-stimulated upregulation of DR5 is critically required for apoptosis, as transient or stable knockdown of DR5 significantly inhibits BV6-triggered apoptosis. In addition, DR5 silencing attenuates formation of a RIP1/FADD/caspase-8 cytosolic cell death complex and activation of caspase-8, -3 and -9. By identifying DR5 as a critical mediator of Smac mimetic-induced apoptosis, our findings provide novel insights into the determinants that control susceptibility of cancer cells to Smac mimetic.
模拟 Smac 促进凋亡，通过中和凋亡抑制蛋白（IAP）蛋白，并被认为是一种很有前途的癌症治疗方法。虽然自分泌/旁分泌肿瘤坏死因子-α（TNFα）环已牵连 Smac 模拟诱导细胞死亡，很少有关于其他因素决定对 Smac 模拟敏感性。使用全基因组基因表达分析，我们确定死亡受体 5（DR5）作为 Smac 模拟诱导细胞凋亡的一个新的关键介质。虽然几种对 Smac 模拟敏感的细胞系以 TNFα依赖性方式死亡，A172 胶质母细胞瘤细胞经历 BV6 诱导的凋亡在很大程度上独立于 TNFα/TNFR1，TNFα阻断抗体 Enbrel 或 TNFR1 敲低提供很少的保护。然而，BV6 刺激核因子-κB（NF-κB）激活对于凋亡是至关重要的，因为通过过表达显性失活 IκBα 超阻遏物（IκBα-SR）抑制 NF-κB 阻断 BV6 诱导的凋亡。在 IκBα-SR 过表达细胞与载体对照细胞之间进行的无偏见的全基因组基因表达研究表明，BV6 以 NF-κB 依赖的方式增加 DR5 的表达。重要的是，这种 BV6 刺激的 DR5 上调对于凋亡是至关重要的，因为 DR5 的瞬时或稳定敲低显著抑制 BV6 触发的凋亡。此外，DR5 沉默减弱 RIP1/FADD/caspase-8 细胞质细胞死亡复合物的形成和 caspase-8、-3 和 -9 的激活。通过鉴定 DR5 作为 Smac 模拟诱导细胞凋亡的关键介质，我们的研究结果为控制癌细胞对 Smac 模拟敏感性的决定因素提供了新的见解。
