The NEDD8 activating enzyme inhibitor MLN4924 mitigates doxorubicin-induced cardiotoxicity in mice.

Doxorubicin (DOX) is a widely utilized chemotherapeutic agent in clinical oncology for treating various cancers. However, its clinical use is constrained by its significant side effects. Among these, the development of cardiomyopathy, characterized by cardiac remodeling and eventual heart failure, stands as a major concern following DOX chemotherapy. In our current investigation, we have showcased the efficacy of MLN4924 in mitigating doxorubicin-induced cardiotoxicity through direct inhibition of the NEDD8-activating enzyme, NAE. MLN4924 demonstrated the ability to stabilize mitochondrial function post-doxorubicin treatment, diminish cardiomyocyte apoptosis, alleviate oxidative stress-induced damage in the myocardium, enhance cardiac contractile function, mitigate cardiac fibrosis, and impede cardiac remodeling associated with heart failure. At the mechanistic level, MLN4924 intervened in the neddylation process by inhibiting the NEDD8 activating enzyme, NAE, within the murine cardiac tissue subsequent to doxorubicin treatment. This intervention resulted in the suppression of NEDD8 protein expression, reduction in neddylation activity, and consequential manifestation of cardioprotective effects. Collectively, our findings posit MLN4924 as a potential therapeutic avenue for mitigating doxorubicin-induced cardiotoxicity by attenuating heightened neddylation activity through NAE inhibition, thereby offering a viable and promising treatment modality for afflicted patients.

Pevonedistat, a first-in-class NEDD8-activating enzyme inhibitor, sensitizes cancer cells to VSVΔ51 oncolytic virotherapy.

The clinical efficacy of VSVΔ51 oncolytic virotherapy has been limited by tumor resistance to viral infection, so strategies to transiently repress antiviral defenses are warranted. Pevonedistat is a first-in-class NEDD8-activating enzyme (NAE) inhibitor currently being tested in clinical trials for its antitumor potential. In this study, we demonstrate that pevonedistat sensitizes human and murine cancer cells to increase oncolytic VSVΔ51 infection, increase tumor cell death, and improve therapeutic outcomes in resistant syngeneic murine cancer models. Increased VSVΔ51 infectivity was also observed in clinical human tumor samples. We further identify the mechanism of this effect to operate via blockade of the type 1 interferon (IFN-1) response through neddylation-dependent interferon-stimulated growth factor 3 (ISGF3) repression and neddylation-independent inhibition of NF-κB nuclear translocation. Together, our results identify a role for neddylation in regulating the innate immune response and demonstrate that pevonedistat can improve the therapeutic outcomes of strategies using oncolytic virotherapy.

Pevonedistat, a Nedd8-activating enzyme inhibitor, in combination with ibrutinib in patients with relapsed/refractory B-cell non-Hodgkin lymphoma.

Pevonedistat (TAK924) is a Nedd8-activating enzyme inhibitor with preclinical activity in non-Hodgkin lymphoma (NHL). This open-label, Phase I, multicenter, investigator-sponsored study enrolled patients with relapsed/refractory (R/R) NHL and chronic lymphocytic leukemia (CLL). The primary objective was safety. Pevonedistat was given intravenously on days 1, 3, 5 of a 21-day cycle for 8 cycles at five dose levels (15 to 50 mg/m2); ibrutinib was administered at 420 or 560 mg orally daily continuously. Eighteen patients with NHL were enrolled, including 8 patients with mantle cell lymphoma (MCL) and 4 patients with CLL. One dose-limiting toxicity (mediastinal hemorrhage) occurred at 50 mg/m2 of pevonedistat which is the estimated maximum tolerated dose. Bruising and diarrhea were the most common adverse events (56% and 44%). Atrial fibrillation occurred in 3 patients (17%). Grade ≥3 toxicities included arthralgia, atrial fibrillation, bone pain, diarrhea, hypertension, and mediastinal hemorrhage (one patient each). The overall response rate (ORR) was 65% (100% ORR in MCL). Pevonedistat disposition was not modified by ibrutinib. scRNA-Seq analysis showed that pevonedistat downregulated NFκB signaling in malignant B-cells in vivo. Thus, pevonedistat combined with ibrutinib demonstrated safety and promising early efficacy in NHL and CLL. NAE inhibition downregulated NFκB signaling in vivo.

Immunomodulatory effect of NEDD8-activating enzyme inhibition in Multiple Myeloma: upregulation of NKG2D ligands and sensitization to Natural Killer cell recognition.

Multiple Myeloma (MM) is an incurable hematologic malignancy of terminally differentiated plasma cells (PCs), where immune interactions play a key role in the control of cancer cell growth and survival. In particular, MM is characterized by a highly immunosuppressive bone marrow microenvironment where the anticancer/cytotoxic activity of Natural Killer (NK) cells is impaired. This study is focused on understanding whether modulation of neddylation can regulate NK cell-activating ligands expression and sensitize MM to NK cell killing. Neddylation is a post-translational modification that adds a ubiquitin-like protein, NEDD8, to selected substrate proteins, affecting their stability, conformation, subcellular localization, and function. We found that pharmacologic inhibition of neddylation using a small-molecule inhibitor, MLN4924/Pevonedistat, increases the expression of the NK cell-activating receptor NKG2D ligands MICA and MICB on the plasma membrane of different MM cell lines and patient-derived PCs, leading to enhanced NK cell degranulation. Mechanistically, MICA expression is upregulated at mRNA level, and this is the result of an increased promoter activity after the inhibition of IRF4 and IKZF3, two transcriptional repressors of this gene. Differently, MLN4924/Pevonedistat induced accumulation of MICB on the plasma membrane with no change of its mRNA levels, indicating a post-translational regulatory mechanism. Moreover, inhibition of neddylation can cooperate with immunomodulatory drugs (IMiDs) in upregulating MICA surface levels in MM cells due to increased expression of CRBN, the cellular target of these drugs. In summary, MLN4924/Pevonedistat sensitizes MM to NK cell recognition, adding novel information on the anticancer activity of neddylation inhibition.

The Anti-Tumor Activity of the NEDD8 Inhibitor Pevonedistat in Neuroblastoma.

Pevonedistat is a neddylation inhibitor that blocks proteasomal degradation of cullin-RING ligase (CRL) proteins involved in the degradation of short-lived regulatory proteins, including those involved with cell-cycle regulation. We determined the sensitivity and mechanism of action of pevonedistat cytotoxicity in neuroblastoma. Pevonedistat cytotoxicity was assessed using cell viability assays and apoptosis. We examined mechanisms of action using flow cytometry, bromodeoxyuridine (BrDU) and immunoblots. Orthotopic mouse xenografts of human neuroblastoma were generated to assess in vivo anti-tumor activity. Neuroblastoma cell lines were very sensitive to pevonedistat (IC50 136-400 nM). The mechanism of pevonedistat cytotoxicity depended on p53 status. Neuroblastoma cells with mutant (p53MUT) or reduced levels of wild-type p53 (p53si-p53) underwent G2-M cell-cycle arrest with rereplication, whereas p53 wild-type (p53WT) cell lines underwent G0-G1 cell-cycle arrest and apoptosis. In orthotopic neuroblastoma models, pevonedistat decreased tumor weight independent of p53 status. Control mice had an average tumor weight of 1.6 mg + 0.8 mg versus 0.5 mg + 0.4 mg (p < 0.05) in mice treated with pevonedistat. The mechanism of action of pevonedistat in neuroblastoma cell lines in vitro appears p53 dependent. However, in vivo studies using mouse neuroblastoma orthotopic models showed a significant decrease in tumor weight following pevonedistat treatment independent of the p53 status. Novel chemotherapy agents, such as the NEDD8-activating enzyme (NAE) inhibitor pevonedistat, deserve further study in the treatment of neuroblastoma.

TAS4464, a NEDD8-activating enzyme inhibitor, activates both intrinsic and extrinsic apoptotic pathways via c-Myc-mediated regulation in acute myeloid leukemia.

TAS4464, a potent, selective small molecule NEDD8-activating enzyme (NAE) inhibitor, leads to inactivation of cullin-RING E3 ubiquitin ligases (CRLs) and consequent accumulations of its substrate proteins. Here, we investigated the antitumor properties and action mechanism of TAS4464 in acute myeloid leukemia (AML). TAS4464 induced apoptotic cell death in various AML cell lines. TAS4464 treatments resulted in the activation of both the caspase-9-mediated intrinsic apoptotic pathway and caspase-8-mediated extrinsic apoptotic pathway in AML cells; combined treatment with inhibitors of these caspases markedly diminished TAS4464-induced apoptosis. In each apoptotic pathway, TAS4464 induced the mRNA transcription of the intrinsic proapoptotic factor NOXA and decreased that of the extrinsic antiapoptotic factor c-FLIP. RNA-sequencing analysis showed that the signaling pathway of the CRL substrate c-Myc was enriched after TAS4464 treatment. Chromatin immunoprecipitation (ChIP) assay revealed that TAS4464-induced c-Myc bound to the PMAIP1 (encoding NOXA) and CFLAR (encoding c-FLIP) promoter regions, and siRNA-mediated c-Myc knockdown neutralized both TAS4464-mediated NOXA induction and c-FLIP downregulation. TAS4464 activated both caspase-8 and caspase-9 along with an increase in NOXA and a decrease in c-FLIP, resulting in complete tumor remission in a human AML xenograft model. These findings suggest that NAE inhibition leads to anti-AML activity via a novel c-Myc-dependent apoptosis induction mechanism.

Targeting SUMO Signaling to Wrestle Cancer.

The small ubiquitin-like modifier (SUMO) signaling cascade is critical for gene expression, genome integrity, and cell cycle progression. In this review, we discuss the important role SUMO may play in cancer and how to target SUMO signaling. Recently developed small molecule inhibitors enable therapeutic targeting of the SUMOylation pathway. Blocking SUMOylation not only leads to reduced cancer cell proliferation but also to an increased antitumor immune response by stimulating interferon (IFN) signaling, indicating that SUMOylation inhibitors have a dual mode of action that can be employed in the fight against cancer. The search for tumor types that can be treated with SUMOylation inhibitors is ongoing. Employing SUMO conjugation inhibitory drugs in the years to come has potential as a new therapeutic strategy.

Immunomodulatory effects of pevonedistat, a NEDD8-activating enzyme inhibitor, in chronic lymphocytic leukemia-derived T cells.

Novel targeted agents used in therapy of lymphoid malignancies, such as inhibitors of B-cell receptor-associated kinases, are recognized to have complex immune-mediated effects. NEDD8-activating enzyme (NAE) has been identified as a tractable target in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma. We and others have shown that pevonedistat (TAK-924), a small-molecule inhibitor of NAE, abrogates NF-κB signaling in malignant B cells. However, NF-κB pathway activity is indispensable in immune response, and T-cell function is altered in patients with CLL. Using T cells derived from patients with CLL, we demonstrate that although targeting NAE results in markedly differential expression of NF-κB-regulated genes and downregulation of interleukin (IL)-2 signaling during T-cell activation, T cells evade apoptosis. Meanwhile, NAE inhibition favorably modulates polarization of T cells in vitro, with decreased Treg differentiation and a shift toward TH1 phenotype, accompanied by increased interferon-γ production. These findings were recapitulated in vivo in immunocompetent mouse models. T cells exposed to pevonedistat in washout experiments, informed by its human pharmacokinetic profile, recover NAE activity, and maintain their response to T-cell receptor stimulation and cytotoxic potential. Our data shed light on the potential immune implications of targeting neddylation in CLL and lymphoid malignancies.

Review of NEDDylation inhibition activity detection methods.

NEDDylation is a post-translational modification of a protein, which transfers Ubiquitin like protein NEDD8 (Neuronal Precursor Cell-expressed Developmentally Down-regulated Protein 8) to the lysine residue of the product through a three-stage enzymatic reaction, and widely regulates many biological processes, such as cell cycle signal transduction and immune recognition. In the past ten years, we have witnessed tremendous progress in the study of protein ubiquitination modification, from modification mechanisms to drug development. Which suggests that inhibition of NEDDylation is an effective way to inhibit tumor. A variety of biological detection methods have been developed during the development of the inhibitor. In this review, we briefly introduced the modification process and substrates of NEDDylation, and discussed detection methods of NEDDylation activity in detail. This review will provide an up-to-date and comprehensive review of the methods for detecting NEDDylation activity that will contribute to NEDDylation inhibitor development.

Phase I study assessing the mass balance, pharmacokinetics, and excretion of [14C]-pevonedistat, a NEDD8-activating enzyme inhibitor in patients with advanced solid tumors.

Pevonedistat (TAK-924/MLN4924) is an investigational small-molecule inhibitor of the NEDD8-activating enzyme that has demonstrated preclinical and clinical activity across solid tumors and hematological malignancies. Here we report the results of a phase I trial characterizing the mass balance, pharmacokinetics, and clearance pathways of [14C]-pevonedistat in patients with advanced solid tumors (NCT03057366). In part A (n = 8), patients received a single 1-h intravenous infusion of [14C]-pevonedistat 25 mg/m2. In part B (n = 7), patients received pevonedistat 25 or 20 mg/m2 on days 1, 3, and 5 in combination with, respectively, docetaxel 75 mg/m2 or carboplatin AUC5 plus paclitaxel 175 mg/m2 on day 1 every 3 weeks. Following the single dose of [14C]-pevonedistat 25 mg/m2 in part A, there was a parallel log-linear decline in plasma and whole blood pevonedistat concentration, with systemic exposure of unchanged pevonedistat representing 41% of drug-related material (i.e., unchanged pevonedistat and its metabolites). The mean terminal half-life of pevonedistat and drug-related material in plasma was 8.4 and 15.6 h, respectively. Pevonedistat distributed preferentially in whole blood with a mean whole-blood-to-plasma ratio for pevonedistat AUC∞ of 40.8. By 1 week post dose, the mean recovery of administered radioactivity was 94% (41% in urine and 53% in feces). The pevonedistat safety profile during both study parts was consistent with previous clinical experience, with no new safety signals observed. In part B, pevonedistat in combination with docetaxel or carboplatin plus paclitaxel was generally well tolerated. ClinicalTrials.gov identifier: NCT03057366 .

NEDDylation negatively regulates ERRß expression to promote breast cancer tumorigenesis and progression.

Estrogen-related receptor beta (ERRß) is downregulated in breast cancer cells and its overexpression in breast cancer patients is positively correlated with an improved prognosis and prolonged relapse-free survival. Here, we unravelled a molecular mechanism for ERRß downregulation in breast cancer. We found that ERRß is a key substrate of the SCF complex and that NEDDylation can activate the Cullin subunits of the SCF complex to target ERRß for degradation in breast cancer. Consistently, using in vitro and in vivo models, we demonstrated that MLN4924, a specific small molecule inhibitor of NEDDylation, can restore ERRß expression and culminate in a reduction in cell proliferation and migration of breast cancer cells. We also showed that increased ERRß expression promotes the upregulation of its target genes, including the tumour suppressors p21Cip1/Waf1 and E-cadherin, involved in cell proliferation and migration arrest at the gene promoter level. Interestingly, this tumour suppressive role of ERRß does not depend on the expression of ERα in breast cancer. Moreover, our data revealed that the ERRß recruits the transcription co-activator p300 to its targeted gene promoters to upregulate their expression. Collectively, our work revealed that restoration of ERRß expression using the NEDDylation inhibitor MLN4924 can be a novel and effective strategy for breast cancer treatment.

Ubiquitin, SUMO, and Nedd8 as Therapeutic Targets in Cancer.

Ubiquitin defines a family of approximately 20 peptidic posttranslational modifiers collectively called the Ubiquitin-like (UbLs). They are conjugated to thousands of proteins, modifying their function and fate in many ways. Dysregulation of these modifications has been implicated in a variety of pathologies, in particular cancer. Ubiquitin, SUMO (-1 to -3), and Nedd8 are the best-characterized UbLs. They have been involved in the regulation of the activity and/or the stability of diverse components of various oncogenic or tumor suppressor pathways. Moreover, the dysregulation of enzymes responsible for their conjugation/deconjugation has also been associated with tumorigenesis and cancer resistance to therapies. The UbL system therefore constitutes an attractive target for developing novel anticancer therapeutic strategies. Here, we review the roles and dysregulations of Ubiquitin, SUMO, and Nedd8 pathways in tumorigenesis, as well as recent advances in the identification of small molecules targeting their conjugating machineries for potential application in the fight against cancer.

A masked initiation region in retinoblastoma protein regulates its proteasomal degradation.

Retinoblastoma protein (Rb) is a tumor suppressor that binds and represses E2F transcription factors. In cervical cancer cells, human papilloma virus (HPV) protein E7 binds to Rb, releasing it from E2F to promote cell cycle progression, and inducing ubiquitination of Rb. E7-mediated proteasomal degradation of Rb requires action by another protease, calpain, which cleaves Rb after Lys 810. However, it is not clear why cleavage is required for Rb degradation. Here, we report that the proteasome cannot initiate degradation efficiently on full-length Rb. Calpain cleavage exposes a region that is recognized by the proteasome, leading to rapid proteolysis of Rb. These findings identify a mechanism for regulating protein stability by controlling initiation and provide a better understanding of the molecular mechanism underlying transformation by HPV.

Abnormal Cullin1 neddylation-mediated p21 accumulation participates in the pathogenesis of recurrent spontaneous abortion by regulating trophoblast cell proliferation and differentiation.

The study explores the role of neddylation in early trophoblast development and its alteration during the pathogenesis of recurrent spontaneous abortion (RSA). Immunofluorescence and western blot were conducted to evaluate the expression pattern of NEDD8 protein in the first-trimester placentas of healthy control and RSA patients. Neddylated-cullins, especially neddylated-cullin1, were downregulated and their substrate, p21, was accumulated in RSA samples. NEDD8 cytoplasmic recruitment was observed in extravillous trophoblast (EVT) progenitors of RSA placentas. Consistent with the results of clinical samples, neddylation inhibition using MLN4924 in trophoblast cell lines caused obvious p21 accumulation and free NEDD8 cytoplasmic recruitment. Further in vitro study demonstrated neddylation inhibition attenuated proliferation of Jeg-3 cells via p21 accumulation. Moreover, when trophoblast stem (TS) cells derived from first-trimester placentas were cultured for differentiation analyses. MLN4924 impaired the differentiation of TS cells towards EVTs by downregulating HLA-G and GATA3. p21 knockdown could partly rescue MLN4924-suppressed HLA-G and GATA3 expression. In conclusion, cullin1 neddylation-mediated p21 degradation is required for trophoblast proliferation and can affect trophoblast plasticity by affecting HLA-G and GATA3 expression. The results provide insights into the pathological mechanism of RSA and the biological regulation of trophoblast development.

Proteome Instability Is a Therapeutic Vulnerability in Mismatch Repair-Deficient Cancer.

Deficient DNA mismatch repair (dMMR) induces a hypermutator phenotype that can lead to tumorigenesis; however, the functional impact of the high mutation burden resulting from this phenotype remains poorly explored. Here, we demonstrate that dMMR-induced destabilizing mutations lead to proteome instability in dMMR tumors, resulting in an abundance of misfolded protein aggregates. To compensate, dMMR cells utilize a Nedd8-mediated degradation pathway to facilitate clearance of misfolded proteins. Blockade of this Nedd8 clearance pathway with MLN4924 causes accumulation of misfolded protein aggregates, ultimately inducing immunogenic cell death in dMMR cancer cells. To leverage this immunogenic cell death, we combined MLN4924 treatment with PD1 inhibition and found the combination was synergistic, significantly improving efficacy over either treatment alone.

Targeting Protein Neddylation for Cancer Therapy.

Neddylation is a posttranslational modification that conjugates a ubiquitin-like protein NEDD8 to substrate proteins. The best-characterized substrates of neddylation are the cullin subunits of cullin-RING E3 ubiquitin ligase complexes (CRLs). CRLs as the largest family of E3 ubiquitin ligases control many important biological processes, including tumorigenesis, through promoting ubiquitylation and subsequent degradation of a variety of key regulatory proteins. The process of protein neddylation is overactivated in multiple types of human cancers, providing a sound rationale as an attractive anticancer therapeutic strategy, evidenced by the development of the NEDD8-activating enzyme (NAE) inhibitor MLN4924 (also known as pevonedistat). Recently, increasing evidence strongly indicates that neddylation inhibition by MLN4924 exerts anticancer effects mainly by triggering cell apoptosis, senescence, and autophagy and causing angiogenesis suppression, inflammatory responses, and chemo-/radiosensitization in a context-dependent manner. Here, we briefly summarize the latest progresses in this field, focusing on the preclinical studies to validate neddylation modification as a promising anticancer target.

Design, Synthesis, and Biological Evaluation of 4-amino Substituted 2Hchromen- 2-one Derivatives as an NEDD8 Activating Enzyme Inhibitor in Pancreatic Cancer Cells.

BACKGROUND: NEDD8 activating enzyme (NAE) plays a critical role in various cellular functions in carcinomas. The selective inhibition of NAE could mediate the rate of ubiquitination and the subsequent degradation of proteins associated with cancer so as to achieve the purpose of treatment. OBJECTIVE: In this article, we decided to study the synthesis and screening of 4-amino substituted 2H-chromen-2-one derivatives against cancer cell lines, specifically the human pancreatic cancer cell line BxPC-3. METHODS: After synthesis of twenty targeted compounds, we evaluated their anti-proliferative activity against six cancer cell lines, cytotoxicity against three normal cell lines through MTT assay, and hemolysis to screen out the candidate compound, which was further conducted drug-like physical property measurement, target confirmation by enzyme-based experiment, cell apoptosis, and synergistic effect research. RESULTS: Starting from intermediates 4 and 5, several new 4-amino substituted 2H-chromen-2-one derivatives (9-28) were synthesized and evaluated for their cell activities using six cancer cell lines. We performed tests of cytotoxicity, hemolysis, ATP-dependent NAE inhibition in the enzyme- based system, apoptosis, and synergistic effect in BxPC-3 cells against the best candidate compound 21. CONCLUSION: Based on these results, we found that compound 21 inhibited NAE activity in an ATP-dependent manner in the enzyme-based system, induced apoptosis in BxPC-3 cells, and synergized with bortezomib on BxPC-3 cell growth inhibition. Additionally, it had low toxicity with reasonable Log P-value and water solubility.

Gartanin is a novel NEDDylation inhibitor for induction of Skp2 degradation, FBXW2 expression, and autophagy.

Gartanin, a 4-prenylated xanthone, has been identified from the purple mangosteen fruit as a potent growth inhibitor of various cancer cell lines, including prostate cancer. However, much of Gartanin's anticancer mechanism remains unknown. We have discovered that Gartanin docked onto the regulatory subunit of the precursor cell-expressed developmentally downregulated 8 (NEDD8)-activating enzyme (NAE) complex and next to the NEDD8 binding complex, which leads to inhibit NEDD8 conjugations to both Cullin1 and Ubc12 in prostate cancer cell lines and Ubc12 NEDDylation in an in vitro assay. The S phase kinase-associated protein (Skp2) and F-box and WD-repeat domain-containing 2 (FBXW2), the NEDD8 family members of E3 ubiqutin ligases, were also downregulated and upregulated by Gartainin, respectively. Knock-down of NEDD8 expression by short harpin (Sh) RNAs blocked or attenuated these effects of Gartainin. Finally, Gartanin demonstrated its ability to inhibit growth of prostate cancer lines via autophagy initiation. Our data support that Gartanin is a naturally occurring NEDDylation inhibitor and deserves further investigation for prostate cancer prevention and treatment.

Activity of TAS4464, a novel NEDD8 activating enzyme E1 inhibitor, against multiple myeloma via inactivation of nuclear factor κB pathways.

The ubiquitin proteasome pathway is essential for the proliferation and survival of multiple myeloma (MM) cells. TAS4464, a novel highly potent inhibitor of NEDD8 activating enzyme, selectively inactivates cullin-RING ubiquitin E3 ligases, resulting in accumulation of their substrates. Here, we examined 14 MM cell lines treated with TAS4464. TAS4464 induced growth arrest and cell death in the MM cell lines even in the presence of bone marrow stromal cells. It also induced the accumulation of phospho-inhibitor of κBα and phospho-p100, impaired the activities of nuclear factor κB (NF-κB) transcription factors p65 and RelB, and decreased the expression of NF-κB target genes, suggesting that TAS4464 inhibits both the canonical and non-canonical NF-κB pathways. TAS4464 had similar effects in an in vivo human-MM xenograft mouse model in which it was also observed to have strong antitumor effects. TAS4464 synergistically enhanced the antitumor activities of the standard MM chemotherapies bortezomib, lenalidomide/dexamethasone, daratumumab and elotuzumab. Together, these results suggest that the anti-MM activity of TAS4464 occurs via inhibition of the NF-κB pathways, and that treatment with TAS4464 is a potential approach for treating MM by single and combination therapies.

Knockdown of Nedd8­conjugating enzyme UBE2M suppresses the proliferation and induces the apoptosis of intrahepatic cholangiocarcinoma cells.

As an important regulator of neddylation, neural precursor cell expressed developmentally downregulated 8 (Nedd8)­conjugating enzyme E2M (UBE2M) mediates cullin neddylation. Upregulation of the neddylation pathway is associated with tumor progression in intrahepatic cholangiocarcinoma (ICC). The present study was designed to assess the effects of Nedd8­conjugating enzyme UBE2M knockdown on intrahepatic cholangiocarcinoma cells, and to determine the potential underlying mechanisms. UBE2M and associated protein expression levels were determined via immunohistochemistry and western blotting. ICC cells were transfected with short hairpin RNA to knockdown UBE2M expression. Cell Counting Kit­8 and colony formation assays, and xenograft experiments were used to examine cell viability and colony survival in vitro, and tumor formation in vivo. Survival was evaluated using Kaplan­Meier analysis and log­rank tests. Patients with ICC presenting high expression of UBE2M exhibited worse accumulative recurrence and overall survival compared with patients with low expression. Knockdown of UBE2M expression led to a decrease in the viability and clonogenic survival of QBC939 and HUCCT1 cells, and suppressed tumor formation in vivo. UBE2M silencing caused accumulation of cullin­RING ligase substrates (chromatin­licensing and DNA replication factor 1 and origin recognition complex subunit 1), inducing DNA damage responses and apoptosis. The present findings suggested that UBE2M serves an important role in ICC progression and may present as a novel target for the treatment of ICC.