Institute for Experimental Cancer Research in Pediatrics, Goethe-University, Komturstrasse 3a, 60528 Frankfurt, Germany.
Institute of Biochemistry I, Goethe-University, Sandhofstraße, 60528 Frankfurt, Germany.
Cell Death Dis. 2014 Dec 11;5(12):e1562. doi: 10.1038/cddis.2014.498.
Smac (second mitochondria-derived activator of caspase) mimetics are considered as promising anticancer therapeutics and used to induce apoptosis by antagonizing inhibitor of apoptosis proteins, which are often abundantly expressed in cancer cells. Here, we identify interferon regulatory factor 1 (IRF1) as a novel critical regulator of Smac mimetic BV6-induced apoptosis and proinflammatory cytokine secretion with impact on the immune response. IRF1 knockdown rescues cells from BV6-induced apoptosis and attenuates BV6-stimulated upregulation of tumor necrosis factor-α (TNFα), indicating that IRF1 mediates BV6-triggered cell death, at least in part, by inducing TNFα. This notion is supported by data showing that exogenous supply of TNFα restores BV6-induced cell death in IRF-knockdown cells. Interestingly, IRF1 selectively controls the induction of nuclear factor-κB (NF-κB) target genes, as IRF1 depletion attenuates BV6-stimulated upregulation of TNFα and interleukin-8 (IL-8) but not p100 and RelB. Concomitant knockdown of IRF1 and p65 cooperate to inhibit BV6-induced cell death, implying a cooperative interaction of IRF1 and NF-κB. In addition, IRF1 silencing hampers TNFα induction by TNFα itself as an another prototypical NF-κB stimulus. Importantly, IRF1 depletion impedes BV6-stimulated secretion of additional proinflammatory cytokines such as granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-8, IL-6 and monocyte chemoattractant protein-1, and migration of primary monocytes to BV6-treated tumor cells. In conclusion, this identification of IRF1 as a dual regulator of BV6-induced apoptosis and inflammatory cytokine secretion provides novel insights into determinants of sensitivity towards Smac mimetic and possible implications of Smac mimetic treatment on tumor microenvironment and immune response.
Smac（第二线粒体衍生的半胱天冬酶激活剂）模拟物被认为是有前途的抗癌治疗药物，通过拮抗凋亡抑制蛋白来诱导细胞凋亡，而凋亡抑制蛋白在癌细胞中常常大量表达。在这里，我们确定干扰素调节因子 1（IRF1）是 Smac 模拟物 BV6 诱导的细胞凋亡和促炎细胞因子分泌的新型关键调节剂，对免疫反应有影响。IRF1 敲低可挽救细胞免受 BV6 诱导的凋亡，并减弱 BV6 刺激的肿瘤坏死因子-α（TNFα）的上调，表明 IRF1 通过诱导 TNFα 介导 BV6 触发的细胞死亡，至少部分如此。这一观点得到了以下数据的支持：外源性提供 TNFα 可恢复 IRF 敲低细胞中 BV6 诱导的细胞死亡。有趣的是，IRF1 选择性地控制核因子-κB（NF-κB）靶基因的诱导，因为 IRF1 耗竭减弱了 BV6 刺激的 TNFα 和白细胞介素-8（IL-8）的上调，但不减弱 p100 和 RelB。IRF1 和 p65 的同时敲低协同抑制 BV6 诱导的细胞死亡，表明 IRF1 和 NF-κB 之间存在合作相互作用。此外，IRF1 沉默抑制 TNFα 自身作为另一种典型的 NF-κB 刺激物诱导的 TNFα 诱导。重要的是，IRF1 耗竭阻止了 BV6 刺激的其他促炎细胞因子如粒细胞-巨噬细胞集落刺激因子（GM-CSF）、IL-8、IL-6 和单核细胞趋化蛋白-1 的分泌，以及初级单核细胞向 BV6 处理的肿瘤细胞的迁移。总之，将 IRF1 鉴定为 BV6 诱导的细胞凋亡和炎症细胞因子分泌的双重调节剂，为 Smac 模拟物的敏感性决定因素以及 Smac 模拟物治疗对肿瘤微环境和免疫反应的可能影响提供了新的见解。
