The Nedd8-activating enzyme inhibitor MLN4924 induces autophagy and apoptosis to suppress liver cancer cell growth

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.     

Targeting protein neddylation with an NEDD8-activating enzyme inhibitor MLN4924 induced apoptosis or senescence in human lymphoma cells

Recent studies indicate that post-translational protein neddylation is required for the maintenance of cell viability in several lymphoma cell lines, while inhibition of the neddylation pathway with an NEDD8-activating enzyme (NAE) inhibitor MLN4924 induces apoptosis in lymphoma cells. However, the mechanism by which neddylation inhibition induces apoptosis in lymphoma cells has not been fully elucidated. Moreover, it is unknown whether neddylation inhibition triggers non-apoptotic cell-killing responses, such as cell senescence, in lymphoma cells. Here, we report that MLN4924 specifically inhibited protein neddylation, inactivated cullin-RING E3 ligase (CRL), the best-known neddylation substrate, and induced the accumulation of tumor-suppressive CRL substrates in lymphoma cells. Moreover, MLN4924 potently suppressed the growth of lymphoma cells by inducing G2 cell-cycle arrest, followed by apoptosis or senescence in a cell line-dependent manner. MLN4924-induced apoptosis was mediated by intrinsic apoptotic signaling with substantial up-regulation of pro-apoptotic Bik and Noxa as well as down-regulation of anti-apoptotic XIAP, c-IAP1 and c-IAP2, while senescence induction upon neddylation inhibition seemed dependent on the expression of tumor suppressor p21/p27. Together, these findings expand our understanding on how lymphoma cells respond to neddylation inhibition and support the development of neddylation inhibitors (e.g. MLN4924) for the treatment of lymphoma.     

Radiosensitization of human pancreatic cancer cells by MLN4924, an investigational NEDD8-activating enzyme inhibitor

Radiotherapy is used in locally advanced pancreatic cancers in which it can improve survival in combination with gemcitabine. However, prognosis is still poor in this setting in which more effective therapies remain needed. MLN4924 is an investigational small molecule currently in phase I clinical trials. MLN4924 inhibits NAE (NEDD8 Activating Enzyme), a pivotal regulator of the E3 ubiquitin ligase SCF (SKP1, Cullins, and F-box protein), that has been implicated recently in DNA damage and repair. In this study, we provide evidence that MLN4924 can be used as an effective radiosensitizer in pancreatic cancer. Specifically, MLN4924 (20-100 nmol/L) effectively inhibited cullin neddylation and sensitized pancreatic cancer cells to ionizing radiation in vitro with a sensitivity enhancement ratio of approximately 1.5. Mechanistically, MLN4924 treatment stimulated an accumulation of several SCF substrates, including CDT1, WEE1, and NOXA, in parallel with an enhancement of radiation-induced DNA damage, aneuploidy, G(2)/M phase cell-cycle arrest, and apoptosis. RNAi-mediated knockdown of CDT1 and WEE1 partially abrogated MLN4924-induced aneuploidy, G(2)/M arrest, and radiosensitization, indicating a causal effect. Furthermore, MLN4924 was an effective radiosensitizer in a mouse xenograft model of human pancreatic cancer. Our findings offer proof-of-concept for use of MLN4924 as a novel class of radiosensitizer for the treatment of pancreatic cancer.     

Induction of p21-Dependent Senescence by an NAE Inhibitor, MLN4924, as a Mechanism of Growth Suppression

Cullin-RING ubiquitin ligase (CRL), with its founding member of SKP1-Cullins-F-box proteins (SCF) E3 ubiquitin ligase, is the largest family of E3 ligases, which requires cullin neddylation for its activation. Recently, an inhibitor of NEDD8 activating enzyme (NAE), MLN4924, was reported to block cullin neddylation and inactivate CRL/SCF E3, resulting in apoptosis induction and tumor suppression both in vitro and in vivo. We report here that apoptosis is not the sole mechanism by which MLN4924 suppresses tumor cell growth because apoptosis is moderately induced by the drug in some cancer cell lines and drug-induced growth suppression is only partially blocked by a pan-caspase inhibitor, z-VAD. MLN4924 treatment induces the characteristics of senescence phenotypes as evidenced by enlarged and flattened cellular morphology and positive staining of senescence-associated β-Gal. MLN4924-induced senescence is associated with cellular response to DNA damage, triggered by accumulation of DNA-licensing proteins CDT1 and ORC1, as a result of inactivation of CRL/SCF E3s. The senescence occurs in the manner independent of pRB/p16 and p53, but dependent on p21, a known substrate of CRL/SCF E3s and a mediator of senescence, which accumulates on CRL/SCF inactivation by MLN4924. Furthermore, MLN4924-induced senescence is irreversible and coupled with persistent accumulation of p21 and sustained activation of DNA damage response. Our study reveals a novel mechanism of MLN4924 action and showed that MLN4924 could be further developed as an effective anticancer agent by inducing apoptosis and irreversible senescence.     

Editor's choice: Suppression of glioblastoma by targeting the overactivated protein neddylation pathway

Background

The neddylation pathway has been recently identified as an attractive anticancer target, and MLN4924, a specific NEDD8-activating enzyme inhibitor, has been developed as a first-in-class anticancer agent. However, neither the status of the neddylation pathway in glioblastoma (GBM) nor the effect of MLN4924 against GBM has been systematically investigated yet.

Methods

To measure the activation state of the neddylation pathway in GBM, expression of the NEDD8-activating enzyme (E1), NEDD8-conjugating enzyme (E2), and global protein neddylation in GBM tumor tissues versus adjacent tissues were examined by immunoblotting analysis and immunohistochemistry staining. To assess the therapeutic efficacy of neddylation inhibition in GBM, cell proliferation in vitro and tumor growth in vivo were determined upon neddylation inhibition by MLN4924, an investigational NEDD8-activating enzyme inhibitor.

Results

The neddylation pathway was overactivated in a majority of GBM tumor tissues when compared with adjacent normal tissues. The upregulation of this pathway in GBM tissues was positively correlated with high-grade disease and postoperative recurrence but was negatively associated with patient overall survival. MLN4924 treatment inhibited cullin neddylation, inactivated cullin-RING E3 ligase, and led to the accumulation of tumor-suppressive cullin-RING E3 ligase substrates to trigger cell-cycle arrest and senescence or apoptosis in a cell-line dependent manner. Moreover, inhibition of neddylation by MLN4924 significantly suppressed tumor growth in an orthotopic xenograft model of human GBM.

Conclusion

Our study indicates that an overactivated neddylation pathway may be involved in GBM progression and that inhibition of this oncogenic pathway is a potentially new therapeutic approach for GBM.     

NEDD8-targeting drug MLN4924 elicits DNA rereplication by stabilizing Cdt1 in S phase, triggering checkpoint activation, apoptosis, and senescence in cancer cells

MLN4924 is a first-in-class experimental cancer drug that inhibits the NEDD8-activating enzyme, thereby inhibiting cullin-RING E3 ubiquitin ligases and stabilizing many cullin substrates. The mechanism by which MLN4924 inhibits cancer cell proliferation has not been defined, although it is accompanied by DNA rereplication and attendant DNA damage. Here we show that stabilization of the DNA replication factor Cdt1, a substrate of cullins 1 and 4, is critical for MLN4924 to trigger DNA rereplication and inhibit cell proliferation. Even only 1 hour of exposure to MLN4924, which was sufficient to elevate Cdt1 for 4-5 hours, was found to be sufficient to induce DNA rereplication and to activate apoptosis and senescence pathways. Cells in S phase were most susceptible, suggesting that MLN4924 will be most toxic on highly proliferating cancers. Although MLN4924-induced cell senescence seems to be dependent on induction of p53 and its downstream effector p21(Waf1), we found that p53(-/-) and p21(-/-) cells were even more susceptible than wild-type cells to MLN4924. Our results suggested that apoptosis, not senescence, might be more important for the antiproliferative effect of MLN4924. Furthermore, our findings show that transient exposure to this new investigational drug should be useful for controlling p53-negative cancer cells, which often pose significant clinical challenge.     

Stabilization of LKB1 and Akt by neddylation regulates energy metabolism in liver cancer

The current view of cancer progression highlights that cancer cells must undergo through a post-translational regulation and metabolic reprogramming to progress in an unfriendly environment. In here, the importance of neddylation modification in liver cancer was investigated. We found that hepatic neddylation was specifically enriched in liver cancer patients with bad prognosis. In addition, the treatment with the neddylation inhibitor MLN4924 in Phb1-KO mice, an animal model of hepatocellular carcinoma showing elevated neddylation, reverted the malignant phenotype. Tumor cell death in vivo translating into liver tumor regression was associated with augmented phosphatidylcholine synthesis by the PEMT pathway, known as a liver-specific tumor suppressor, and restored mitochondrial function and TCA cycle flux. Otherwise, in protumoral hepatocytes, neddylation inhibition resulted in metabolic reprogramming rendering a decrease in oxidative phosphorylation and concomitant tumor cell apoptosis. Moreover, Akt and LKB1, hallmarks of proliferative metabolism, were altered in liver cancer being new targets of neddylation. Importantly, we show that neddylation-induced metabolic reprogramming and apoptosis were dependent on LKB1 and Akt stabilization. Overall, our results implicate neddylation/signaling/metabolism, partly mediated by LKB1 and Akt, in the development of liver cancer, paving the way for novel therapeutic approaches targeting neddylation in hepatocellular carcinoma.     

MLN4924, a Novel NEDD8-activating enzyme inhibitor,exhibits antitumor activity and enhances cisplatin-induced cytotoxicity in human cervical carcinoma: in vitro and in vivo study

MLN4924, an inhibitor of NEDD8 activating enzyme (NAE), has been reported to have activity against various malignancies. Here, we investigated the antitumor properties of MLN4924 and MLN4924 in combination with cisplatin on human cervical carcinoma (CC) in vitro and in vivo. Two human CC cell lines, ME-180 and HeLa, were used in this study. The cytotoxic effects of MLN4924 and/or cisplatin were measured by cell viability (MTT), proliferation (BrdU incorporation), apoptosis (flow cytometry with annexin V-FITC labeling), and the expression of cell apoptosis-related proteins (Western blotting). In vivo efficacy was determined in Nu/Nu nude mice with ME-180 and HeLa xenografts. The results showed that MLN4924 elicited viability inhibition, anti-proliferation and apoptosis in human CC cells, accompanied by activations of apoptosis-related molecules and Bid, Bcl-2 phosphorylation interruption, and interference with cell cycle regulators. Moreover, MLN4924 caused an endoplasmic reticulum stress response (caspase-4, ATF-4 and CHOP activations) and expression of other cellular stress molecules (JNK and c-Jun activations). Additionally, MLN4924 suppressed growth of CC xenografts in nude mice. Furthermore, we demonstrated that MLN4924 potentiated cisplatin-induced cytotoxicity in CC cells with activation of caspases. Consistently with this, MLN4924 significantly enhanced cisplatin-induced growth inhibition of CC xenografts. Together, these findings suggest that MLN4924 alone or in combination with cisplatin is of value in treating human CCs.     

MLN4924 therapy as a novel approach in cancer treatment modalities

MLN4924 is an investigational and a newly discovered small molecule that is a potent and selective inhibitor of the NEDD8 (Neural precursor cell-Expressed Developmentally down-regulated 8) Activating Enzyme (NAE), a pivotal regulator of the Cullin Ring Ligases E3 (CRL), which has been implicated recently in DNA damage. MLN4924 effectively inhibits tumour cell growth by inducing all three common types of death, namely apoptosis, autophagy and senescence and it was also reported that the formation of capillary vessels was significantly suppressed by MLN4924.In this review, we are going to highlight the molecular mechanism of MLN4924 in cancer therapy and its pros and cons in cancer therapy.     

MLN4924对紫杉醇耐药的前列腺癌细胞增殖和凋亡的影响

目的:研究MLN4924对紫杉醇耐药的前列腺癌细胞增殖和凋亡的影响,从而为紫杉醇耐药前列腺癌的临床治疗提供新的理论依据。方法:不同浓度的MLN4924作用紫杉醇耐药的前列腺癌细胞PC3-TxR和DU145-TxR 48和72小时后,采用MTS检测细胞活力。Western blot检测凋亡相关蛋白Caspase-3、CDT1、p27以及EMT标志物水平。结果:MLN4924能够显著抑制PC3-TxR和DU145-TxR细胞的增殖,并且具有时间和浓度的依懒性。Western blot结果显示MLN4924作用后显著增加细胞内凋亡相关蛋白Caspase-3、CDT1和p27的表达。结论:MLN4924能够显著抑制紫杉醇耐药的前列腺癌细胞增殖、促进细胞凋亡,其相关机制为MLN4924可通过上调p27蛋白表达促进紫杉醇耐药的前列腺癌细胞凋亡。     

Neddylation pathway is up-regulated in human intrahepatic cholangiocarcinoma and serves as a potential therapeutic target

Therapeutic intervention in neddylation pathway is an emerging area for cancer treatment. Herein, we evaluated the clinical relevance and therapeutic potential of targeting this pathway in intrahepatic cholangiocarcinoma (ICC). Immunohistochemistry of neddylation pathway components in a cohort of 322 cases showed that E1 (NAE1 and UBA3) and E2 (UBC12) enzymes, as well as global NEDD8 conjugation, were upregulated in over 2/3 of human ICC. Notably, NAE1 was identified as an independent prognosticator for postoperative recurrence (P=0.009) and a combination of NEDD8 and NAE1 provided a better power for predicting patient clinical outcomes. In vitro treatment with MLN4924, a small-molecule NEDD8-activating enzyme inhibitor, led to a dose-dependent decrease of viability in both established and primary cholangiocarcinoma cell lines. Additionally, MLN4924 exhibited at least additive effect when combined with cisplatin. By blocking cullins neddylation, MLN4924 inactivated Cullin-Ring ligase (CRL) and caused the accumulation of CRL substrates that triggered cell cycle arrest, senescence or apoptosis. Meanwhile, MLN4924 was well-tolerated and significantly inhibited tumor growth in xenograft model of cholangiocarcinoma. Taken together, our findings indicated that upregulated neddylation pathway was involved in ICC progression and interference in this pathway could be a promising target for ICC therapy.     

Induction of autophagy-dependent apoptosis by the survivin suppressant YM155 in prostate cancer cells

In this study, we demonstrated that YM155, a novel survivin suppressant, induced both apoptosis, and autophagy that was shown by conversion of cytosolic-associated protein light chain 3 (LC3I) into autophagosome-associated form (LC3II) and a punctate fluorescence pattern of an ectopic GFP-LC3 protein. The lysosomal inhibitor chloroquine further accumulated YM155-induced LC3II, indicating an increase of autophagic flux. Ectopic expression of survivin significantly attenuated YM155-induced apoptosis and autophagy, whereas survivin siRNA induced autophagy. Furthermore, inhibition of either early or late events of autophagy attenuated YM155-induced apoptosis, demonstrating that induction of autophagy proceeds apoptosis. In conclusion, suppression of survivin by YM155 induces autophagy-dependent apoptosis, and YM155-induced autophagy plays a pro-apoptotic role thereby unveiling a novel mechanism of YM155 in prostate cancer cells.     

MLN4924抗肿瘤作用机制

MLN4924可通过诱导肿瘤细胞凋亡、衰老、细胞自噬抑制肿瘤细胞的增殖、浸润、转移,其可抑制肿瘤血管生成并能增强肿瘤对放疗、化疗的敏感性,发挥良好的抗肿瘤效应.     

MLN4924促进人肺腺癌细胞株A549凋亡的机制研究

  目的  观察MLN4924对人肺腺癌A549细胞增殖、凋亡的影响,探讨MLN4924促进凋亡的作用机制。  方法  不同浓度的MLN4924作用细胞不同时间后,采用CCK-8检测细胞增殖抑制率;Hoechst33342荧光染色、流式细胞仪检测细胞凋亡率及细胞周期;Western blot检测凋亡相关蛋白Caspase-3、NF-κB p65及CDT1相对表达量。  结果  MLN4924能够明显抑制A549细胞的增殖,并且具有浓度和时间依赖性。流式细胞仪检测结果显示药物作用后,细胞被阻滞在S期。Western blot结果显示药物作用后细胞内Caspase-3、CDT1蛋白的表达量增加,而NF-κB p65的表达量减少。  结论  MLN4924能够明显抑制A549细胞增殖、促进细胞凋亡,其相关机制为MLN4924可阻滞细胞于S期,增加Caspase-3蛋白表达,抑制NF-κB通路的激活。      

High Efficiency Apoptosis Induction in Breast Cancer Cell Lines by MLN4924/2DG Co-Treatment

2-deoxy-D-Glucose (2DG) causes cytotoxicity in cancer cells by disrupting thiol metabolism. It is an effectivecomponent in therapeutic strategies. It targets the metabolism of cancer cells with glycolysis inhibitory activity.On the other hand, MLN4924, a newly discovered investigational small molecule inhibitor of NAE (NEDD8activating enzyme), inactivates SCF E3 ligase and causes accumulation of its substrates which triggers apoptosis.Combination of these components might provide a more efficient approach to treatment. In this research,2DG and MLN4924 were co-applied to breast cancer cells (MCF-7 and SKBR-3) and cytotoxic and apoptoticactivity were evaluated the by Micro culture tetrazolium test (MTT), TUNEL and ELISA methods. Caspase3and Bcl2 genes expression were evaluated by real time Q-PCR methods. The results showed that MLN4924 andMLN4924/2DG dose-dependently suppressed the proliferation of MCF7 and SKBR-3 cells. Cell survival of breastcancer cells exposed to the combination of 2DG/MLN4924 was decreased significantly compared to controls(p<0.05), while 2DG and MLN4924 alone had less pronounced effects on the cells. The obtained results suggestthat 2DG/MLN4924 is much more efficient in breast cancer cell lines with enhanced cytotoxicity via inducing aapoptosis cell signaling gene, caspase-3.     

Autophagy Inhibition Sensitizes Cisplatin Cytotoxicity in Human Gastric Cancer Cell Line Sgc7901

We aimed to investigate the mechanism and effects of autophagy on cisplatin (DDP)-induced apoptosis inhuman gastric cancer cell line SGC7901. After SGC7901 cells were treated with DDP and/or chloroquine, cellproliferation was measured using MTT assay; cell apoptosis was determined by flow cytometry; autophagy andapotosis-related proteins expression were detected by Western blot; and quantitative analysis of autophagy aftermonodansylcadaverine (MDC) staining was performed using fluorescence microscopy. We found after treatmentwith 5 mg/L DDP for 24 h, the rates of cell apoptosis were (21.07±2.12)%. Autophagy, characterized by an increasein the number of autophagic vesicles and the level of LC3-II protein was observed in cells treated with DDP.After inhibition of autophagy by chloroquine, the rates of cell apoptosis were increased to (30.16±3.54)%, andthe level of Caspase-3 and P53 protein were increased, and Bcl-2 protein was decreased. Therefore, autophagyprotects human gastric cancer cell line SGC7901 against DDP-induced apoptosis, inhibition of autophagy canpromote apoptosis, and combination therapy with DDP and chloroquine may be a promising therapeutic strategyfor gastric cancer.     

Inhibition of autophagy enhances cisplatin cytotoxicity through endoplasmic reticulum stress in human cervical cancer cells

The function of autophagy in cisplatin-treated cancer cells is not fully understood. Cisplatin treatment induced degradation of ubiquitinated proteins by autophagy, which reduced apoptosis induced by endoplasmic reticulum (ER) stress and downregulated the mitochondrial pathway of apoptosis. Inhibition of autophagy using 3-methyladenine (3-MA) or chloroquine (CQ) increased the levels of intracellular misfolded proteins, which enhanced cellular apoptosis. We found that tunicamycin, an ER stress inducer, augmented cisplatin cytotoxicity by upregulating ER stress-mediated apoptosis. Our data indicates that autophagy plays an important role in preventing cisplatin-induced apoptosis in HeLa cells, thus inhibition of autophagy may improve cisplatin chemotherapy.     

靶向肝癌细胞自噬提高大黄素的毒性杀伤作用

背景与目的:大黄素处理肝癌细胞后能够诱导内质网应激和凋亡.鉴于内质网应激与自噬之间的关联及后者作为细胞对抗应激环境的一种自我防御机制,该研究拟探讨通过抑制肝癌细胞自噬信号通路的策略提高大黄素对肿瘤细胞的毒性杀伤作用.方法:大黄素处理肝癌细胞后,应用CYTO-ID自噬检测试剂盒和蛋白[质]印迹法(Western blot)分别检测大黄素诱发细胞自噬情况;利用细胞自噬抑制剂(氯喹)预先抑制肝癌细胞自噬的产生,然后用大黄素处理肝癌细胞,最后通过ATPlite试验和细胞克隆形成实验检测肿瘤细胞存活;通过流式细胞术检测氯喹和大黄素联合处理诱导肝癌细胞发生凋亡的凋亡率,采用Western blot检测凋亡效应蛋白caspase-3活化断裂后产生活性片段的水平.结果:大黄素处理肝癌细胞后能够诱导肝癌细胞自噬;利用氯喹抑制肝癌细胞自噬能够显著能够提高大黄素对肝癌细胞克隆存活的抑制作用;氯喹和大黄素联合处理肝癌细胞能够显著提高细胞周期sub-G1期和活化caspase-3蛋白的表达水平.结论:靶向肝癌细胞自噬能够提高大黄素的毒性杀伤作用.