Division of Radiation and Cancer Biology, Department of Radiation Oncology, University of Michigan, 4424B MS-1, 1301 Catherine Street, Ann Arbor, MI 48109, USA.
Cell Death Dis. 2012 Sep 6;3(9):e386. doi: 10.1038/cddis.2012.125.
MLN4924, a newly discovered small molecule inhibitor of NEDD8-activating enzyme (NAE), inactivates Cullin-RING E3 ubiquitin Ligases (CRLs) by blocking cullin neddylation. As a result, MLN4924 causes accumulation of several key substrates of CRLs and effectively suppresses tumor cell growth by inducing apoptosis and senescence. However, the role of MLN4924 in induction of autophagy and its biological significance are totally unknown. Here we showed that MLN4924 effectively induces autophagy in both time- and dose-dependent manners in multiple human cancer lines, indicating a general phenomenon. Mechanistically, by inactivating CRLs, MLN4924 causes accumulation of DEPTOR and HIF1α. The siRNA knockdown and gene KO studies showed that DEPTOR and the HIF1-REDD1-TSC1 axis are responsible for MLN4924-induced autophagy via inhibiting mTORC1. Biologically, autophagy is a survival signal to tumor cells, and blockage of autophagy via siRNA knockdown, gene KO and small molecule inhibitor remarkably enhanced MLN4924-induced apoptosis. Our study reveals an uncharacterized mechanism of MLN4924 action and provides the proof-of-concept evidence for strategic drug combination of MLN4924 with an autophagy inhibitor for maximal killing of tumor cells via enhancing apoptosis.
MLN4924 是一种新发现的 NEDD8-激活酶 (NAE) 的小分子抑制剂，通过阻断 Cullin-RING E3 泛素连接酶 (CRLs) 的 Cullin 连接来使 Cullin-RING E3 泛素连接酶 (CRLs) 失活。因此，MLN4924 导致几种关键 CRLs 底物的积累，并通过诱导细胞凋亡和衰老有效抑制肿瘤细胞生长。然而，MLN4924 诱导自噬的作用及其生物学意义尚完全未知。在这里，我们表明 MLN4924 以时间和剂量依赖的方式在多种人类癌细胞系中有效诱导自噬，这表明这是一种普遍现象。从机制上讲，通过使 CRLs 失活，MLN4924 导致 DEPTOR 和 HIF1α 的积累。siRNA 敲低和基因 KO 研究表明，DEPTOR 和 HIF1-REDD1-TSC1 轴通过抑制 mTORC1 负责 MLN4924 诱导的自噬。从生物学上讲，自噬是肿瘤细胞的一种生存信号，通过 siRNA 敲低、基因 KO 和小分子抑制剂阻断自噬可显著增强 MLN4924 诱导的细胞凋亡。我们的研究揭示了 MLN4924 作用的一种未被描述的机制，并为 MLN4924 与自噬抑制剂联合使用提供了概念验证证据，通过增强细胞凋亡，最大程度地杀伤肿瘤细胞。
