Department of Immunology, Shanghai Medical College, and Biotherapy Research Center, Department of Digestive Diseases, Huashan Hospital, Shanghai, China.
Cancer Res. 2012 Jul 1;72(13):3360-71. doi: 10.1158/0008-5472.CAN-12-0388. Epub 2012 May 4.
Posttranslational neddylation of cullins in the Cullin-Ring E3 ligase (CRL) complexes is needed for proteolytic degradation of CRL substrates, whose accumulation induces cell-cycle arrest, apoptosis, and senescence. The Nedd8-activating enzyme (NAE) is critical for neddylation of CRL complexes and their growth-promoting function. Recently, the anticancer small molecule MLN4924 currently in phase I trials was determined to be an inhibitor of NAE that blocks cullin neddylation and inactivates CRL, triggering an accumulation of CRL substrates that trigger cell-cycle arrest, apoptosis, and senescence in cancer cells. Here, we report that MLN4924 also triggers autophagy in response to CRL inactivation and that this effect is important for the ability of MLN4924 to suppress the outgrowth of liver cancer cells in vitro and in vivo. MLN4924-induced autophagy was attributed partially to inhibition of mTOR activity, due to accumulation of the mTOR inhibitory protein Deptor, as well as to induction of reactive oxygen species stress. Inhibiting autophagy enhanced MLN4924-induced apoptosis, suggesting that autophagy is a survival signal triggered in response to CRL inactivation. In a xenograft model of human liver cancer, MLN4924 was well-tolerated and displayed a significant antitumor effect characterized by CRL inactivation and induction of autophagy and apoptosis in liver cancer cells. Together, our findings support the clinical investigation of MLN4924 for liver cancer treatment and provide a preclinical proof-of-concept for combination therapy with an autophagy inhibitor to enhance therapeutic efficacy.
泛素化的 Cullin 在 Cullin-Ring E3 连接酶（CRL）复合物中的翻译后修饰对于 CRL 底物的蛋白水解降解是必需的，CRL 底物的积累会诱导细胞周期停滞、细胞凋亡和衰老。Nedd8-激活酶（NAE）对于 CRL 复合物的泛素化及其促进生长的功能至关重要。最近，正在进行 I 期临床试验的抗癌小分子 MLN4924 被确定为 NAE 的抑制剂，它可以阻断 Cullin 的泛素化并使 CRL 失活，导致 CRL 底物的积累，从而触发癌细胞的细胞周期停滞、细胞凋亡和衰老。在这里，我们报告 MLN4924 也会触发自噬反应，以响应 CRL 的失活，并且这种效应对于 MLN4924 在体外和体内抑制肝癌细胞生长的能力非常重要。MLN4924 诱导的自噬部分归因于 mTOR 活性的抑制，这是由于 mTOR 抑制蛋白 Deptor 的积累，以及活性氧应激的诱导。抑制自噬增强了 MLN4924 诱导的细胞凋亡，这表明自噬是 CRL 失活后触发的一种生存信号。在人肝癌的异种移植模型中，MLN4924 耐受性良好，并表现出显著的抗肿瘤作用，其特征是 CRL 失活以及自噬和凋亡在肝癌细胞中的诱导。总之，我们的研究结果支持 MLN4924 用于肝癌治疗的临床研究，并为与自噬抑制剂联合治疗以增强治疗效果提供了临床前概念验证。
