The Protein Neddylation Inhibitor MLN4924 Suppresses Patient-Derived Glioblastoma Cells via Inhibition of ERK and AKT Signaling

Protein neddylation and its role in health and diseases

NEDD8 (Neural precursor cell expressed developmentally downregulated protein 8) is an ubiquitin-like protein that is covalently attached to a lysine residue of a protein substrate through a process known as neddylation, catalyzed by the enzyme cascade, namely NEDD8 activating enzyme (E1), NEDD8 conjugating enzyme (E2), and NEDD8 ligase (E3). The substrates of neddylation are categorized into cullins and non-cullin proteins. Neddylation of cullins activates CRLs (cullin RING ligases), the largest family of E3 ligases, whereas neddylation of non-cullin substrates alters their stability and activity, as well as subcellular localization. Significantly, the neddylation pathway and/or many neddylation substrates are abnormally activated or over-expressed in various human diseases, such as metabolic disorders, liver dysfunction, neurodegenerative disorders, and cancers, among others. Thus, targeting neddylation becomes an attractive strategy for the treatment of these diseases. In this review, we first provide a general introduction on the neddylation cascade, its biochemical process and regulation, and the crystal structures of neddylation enzymes in complex with cullin substrates; then discuss how neddylation governs various key biological processes via the modification of cullins and non-cullin substrates. We further review the literature data on dysregulated neddylation in several human diseases, particularly cancer, followed by an outline of current efforts in the discovery of small molecule inhibitors of neddylation as a promising therapeutic approach. Finally, few perspectives were proposed for extensive future investigations.

Emerging trends in post-translational modification: Shedding light on Glioblastoma multiforme

Recent multi-omics studies, including proteomics, transcriptomics, genomics, and metabolomics have revealed the critical role of post-translational modifications (PTMs) in the progression and pathogenesis of Glioblastoma multiforme (GBM). Further, PTMs alter the oncogenic signaling events and offer a novel avenue in GBM therapeutics research through PTM enzymes as potential biomarkers for drug targeting. In addition, PTMs are critical regulators of chromatin architecture, gene expression, and tumor microenvironment (TME), that play a crucial function in tumorigenesis. Moreover, the implementation of artificial intelligence and machine learning algorithms enhances GBM therapeutics research through the identification of novel PTM enzymes and residues. Herein, we briefly explain the mechanism of protein modifications in GBM etiology, and in altering the biologics of GBM cells through chromatin remodeling, modulation of the TME, and signaling pathways. In addition, we highlighted the importance of PTM enzymes as therapeutic biomarkers and the role of artificial intelligence and machine learning in protein PTM prediction.

Targeting cullin neddylation for cancer and fibrotic diseases

Protein neddylation is a post-translational modification, and its best recognized substrates are cullin family proteins, which are the core component of Cullin-RING ligases (CRLs). Given that most neddylation pathway proteins are overactivated in different cancers and fibrotic diseases, targeting neddylation becomes an emerging approach for the treatment of these diseases. To date, numerous neddylation inhibitors have been developed, of which MLN4924 has entered phase I/II/III clinical trials for cancer treatment, such as acute myeloid leukemia, melanoma, lymphoma and solid tumors. Here, we systematically describe the structures and biological functions of the critical enzymes in neddylation, highlight the medicinal chemistry advances in the development of neddylation inhibitors and propose the perspectives concerning targeting neddylation for cancer and fibrotic diseases.

A Promising Way to Overcome Temozolomide Resistance through Inhibition of Protein Neddylation in Glioblastoma Cell Lines

There is no effective therapy for the lately increased incidence of glioblastoma multiforme (GBM)-the most common primary brain tumor characterized by a high degree of invasiveness and genetic heterogeneity. Currently, DNA alkylating agent temozolomide (TMZ) is the standard chemotherapy. Nevertheless, TMZ resistance is a major problem in the treatment of GBM due to numerous molecular mechanisms related to DNA damage repair, epigenetic alterations, cellular drug efflux, apoptosis-autophagy, and overactive protein neddylation. Low molecular weight inhibitors of NEDD8-activating enzyme (NAE), such as MLN4924, attenuate protein neddylation and present a promising low-toxicity anticancer agent. The aim of our study was to find an effective combination treatment with TMZ and MLN4924 in our TMZ-resistant GBM cell lines and study the effect of these combination treatments on different protein expressions such as O⁶-methylguanine methyltransferase (MGMT) and p53. The combination treatment successfully decreased cell viability and sensitized TMZ-resistant cells to TMZ, foreshadowing a new treatment strategy for GBM.

Discovery of dual tubulin-NEDDylation inhibitors with antiproliferative activity

Although various dual-target tubulin inhibitors have been designed and synthesised, no dual tubulin-NEDDylation inhibitors as antiproliferative agents were reported so far. In this work, a series of trimethoxyphenyl analogues as potential dual tubulin-NEDDylation inhibitors were synthesised and evaluated for their antiproliferative activity. Among them, compound C11 exhibited the most potent inhibitory activity with IC₅₀ values of 1.17, 2.48, and 1.47 μM against HepG2, PC3, and MCF7 cells, respectively. In addition, it displayed the potent inhibitory activity against tubulin with an IC₅₀ value of 2.40 μM and obviously inhibited tubulin polymerisation in HepG2 cells. Furthermore, C11 inhibited NEDDylation by a ATP-dependent manner. Molecular docking studies revealed that the methoxy group and dithiocarbamate group of C11 could form hydrogen bonds with residues of tubulin and E1 NEDD8-activating enzyme (NAE). These results suggested that compound C11 was a dual tubulin-NEDDylation inhibitor with antiproliferative activity.

Flavokawain A Reduces Tumor-Initiating Properties and Stemness of Prostate Cancer

We have previously demonstrated the in vivo chemopreventive efficacy of flavokawain A (FKA), a novel chalcone from the kava plant, in prostate carcinogenesis models. However, the mechanisms of the anticarcinogenic effects of FKA remain largely unknown. We evaluated the effect of FKA on prostate tumor spheroid formation by prostate cancer stem cells, which were sorted out from CD44+/CD133+ prostate cancer cells 22Rv1 and DU145. FKA treatment significantly decreased both the size and numbers of the tumor spheroids over different generations of spheroid passages. In addition, the dietary feeding of FKA-formulated food to Nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice bearing CD44+/CD133+ 22Rv1 xenograft tumors resulted in a significant reduction of tumor growth compared to those fed with vehicle control food–fed mice. Furthermore, the expression of stem cell markers, such as Nanog, Oct4, and CD44, were markedly downregulated in both tumor spheroids and tumor tissues. We also observed that FKA inhibits Ubc12 neddylation, c-Myc, and keratin-8 expression in both CD44+/CD133+ prostate tumor spheroids and xenograft tumors. Our results suggest that FKA can reduce the tumor-initiating properties and stemness of prostate cancer, which provides a new mechanism for the chemoprevention efficacy of FKA.

Pevonedistat Suppresses Pancreatic Cancer Growth via Inactivation of the Neddylation Pathway

Background

The neddylation pathway is aberrantly overactivated in multiple human cancers and has been indicated as an effective target for anticancer therapy in clinical trials. We aimed to study whether the neddylation pathway is upregulated in pancreatic cancer and whether pevonedistat, a first-in-class anticancer agent specifically targeting this pathway, will suppress cancer tumorigenesis and progression.

Methods

We evaluated the expression pattern of neddylation pathway components in 179 pancreatic adenocarcinoma (PAAD) compared with 171 normal tissues from The Cancer Genome Atlas (TCGA) dataset and further assessed PAAD patient prognosis with high neddylation pathway expression via Gene Expression Profiling Interactive Analysis (GEPIA). We then analyzed malignant cancer phenotypes both in vitro and in vivo, as well as intrinsic molecular mechanisms upon pevonedistat treatment.

Results

We found that the neddylation pathway was hyperactivated in pancreatic cancer. Patients with high neddylation pathway expression exhibited worse prognoses. Pevonedistat significantly inhibited the cancer cell cycle, cell growth, and proliferation; increased cell apoptosis; and decreased cancer cell xenografts in a mouse model. Mechanistically, pevonedistat treatment and the siRNA knockdown neddylation pathway were able to remarkably induce the accumulation of Wee1, p27, and p21. Further mechanistic studies revealed that pevonedistat mainly impaired the ubiquitination level and delayed the protein degradation of Wee1, p27, and p21.

Conclusions

Our results showed that pevonedistat targeted the overexpression of the neddylation pathway in pancreatic cancer to induce cell growth suppression by inducing the accumulation of the cell cycle regulators Wee1, p27, and p21, which provides sound evidence for the clinical trial of pevonedistat for pancreatic cancer therapy.

The NEDD8-activating enzyme inhibitor MLN4924 reduces ischemic brain injury in mice

Ischemic stroke is a leading cause of death and disability with limited therapies. Neuronal precursor cell-expressed developmentally downregulated protein 8 (NEDD8) is a ubiquitin-like protein that is involved in protein neddylation. The first-in-class anticancer agent called MLN4924 plays a crucial role in suppressing tumorigenesis and attenuating inflammatory responses due to specifically inhibiting NEDD8-activating enzyme. Here, we investigated the potential protective role of MLN4924 after experimental stroke. We showed that the neddylation pathway is overactivated in the brain following cerebral ischemia. Inhibition of neddylation by MLN4924 protects the brain against ischemic injury by attenuating neutrophil extravasation and maintaining blood–brain barrier integrity. Our findings provide insights into the promising treatment with neddylation inhibition for ischemic brain injury.

Blood–brain barrier (BBB) breakdown and inflammation occurring at the BBB have a key, mainly a deleterious role in the pathophysiology of ischemic stroke. Neddylation is a ubiquitylation-like pathway that is critical in various cellular functions by conjugating neuronal precursor cell-expressed developmentally down-regulated protein 8 (NEDD8) to target proteins. However, the roles of neddylation pathway in ischemic stroke remain elusive. Here, we report that NEDD8 conjugation increased during acute phase after ischemic stroke and was present in intravascular and intraparenchymal neutrophils. Inhibition of neddylation by MLN4924, also known as pevonedistat, inactivated cullin-RING E3 ligase (CRL), and reduced brain infarction and improved functional outcomes. MLN4924 treatment induced the accumulation of the CRL substrate neurofibromatosis 1 (NF1). By using virus-mediated NF1 silencing, we show that NF1 knockdown abolished MLN4924-dependent inhibition of neutrophil trafficking. These effects were mediated through activation of endothelial P-selectin and intercellular adhesion molecule-1 (ICAM-1), and blocking antibodies against P-selectin or anti–ICAM-1 antibodies reversed NF1 silencing-induced increase in neutrophil infiltration in MLN4924-treated mice. Furthermore, we found that NF1 silencing blocked MLN4924-afforded BBB protection and neuroprotection through activation of protein kinase C δ (PKCδ), myristoylated alanine-rich C-kinase substrate (MARCKS), and myosin light chain (MLC) in cerebral microvessels after ischemic stroke, and treatment of mice with the PKCδ inhibitor rottlerin reduced this increased BBB permeability. Our study demonstrated that increased neddylation promoted neutrophil trafficking and thus exacerbated injury of the BBB and stroke outcomes. We suggest that the neddylation inhibition may be beneficial in ischemic stroke.

Extracellular vesicles derived from glioblastoma promote proliferation and migration of neural progenitor cells via PI3K-Akt pathway

BACKGROUND

Glioblastomas are lethal brain tumors under the current combinatorial therapeutic strategy that includes surgery, chemo- and radio-therapies. Extensive changes in the tumor microenvironment is a key reason for resistance to chemo- or radio-therapy and frequent tumor recurrences. Understanding the tumor-nontumor cell interaction in TME is critical for developing new therapy. Glioblastomas are known to recruit normal cells in their environs to sustain growth and encroachment into other regions. Neural progenitor cells (NPCs) have been noted to migrate towards the site of glioblastomas, however, the detailed mechanisms underlying glioblastoma-mediated NPCs' alteration remain unkown.

METHODS

We collected EVs in the culture medium of three classic glioblastoma cell lines, U87 and A172 (male cell lines), and LN229 (female cell line). U87, A172, and LN229 were co-cultured with their corresponding EVs, respectively. Mouse NPCs (mNPCs) were co-cultured with glioblastoma-derived EVs. The proliferation and migration of tumor cells and mNPCs after EVs treatment were examined. Proteomic analysis and western blotting were utilized to identify the underlying mechanisms of glioblastoma-derived EVs-induced alterations in mNPCs.

RESULTS

We first show that glioblastoma cell lines U87-, A172-, and LN229-derived EVs were essential for glioblastoma cell prolifeartion and migration. We then demonstrated that glioblastoma-derived EVs dramatically promoted NPC proliferation and migration. Mechanistic studies identify that glioblastoma-derived EVs achieve their functions via activating PI3K-Akt-mTOR pathway in mNPCs. Inhibiting PI3K-Akt pathway reversed the elevated prolfieration and migration of glioblastoma-derived EVs-treated mNPCs.

CONCLUSION

Our findings demonstrate that EVs play a key role in intercellular communication in tumor microenvironment. Inhibition of the tumorgenic EVs-mediated PI3K-Akt-mTOR pathway activation might be a novel strategy to shed light on glioblastoma therapy. Video Abstract.

Research progress in hepatitis B virus covalently closed circular DNA

Hepatitis B virus (HBV) infections are a global public health issue. HBV covalently closed circular DNA (cccDNA), the template for the transcription of viral RNAs, is a key factor in the HBV replication cycle. Notably, many host factors involved in HBV cccDNA epigenetic modulation promote the development of hepatocellular carcinoma (HCC). The HBV cccDNA minichromosome is a clinical obstacle that cannot be efficiently eliminated. In this review, we provide an update on the advances in research on HBV cccDNA and further discuss factors affecting the modulation of HBV cccDNA. Hepatitis B virus X protein (HBx) contributes to HBV cccDNA transcription and the development of hepatocarcinogenesis through modulating host epigenetic regulatory factors, thus linking the cccDNA to hepatocarcinogenesis. The measurable serological biomarkers of continued transcription of cccDNA, the effects of anti-HBV drugs on cccDNA, and potential therapeutic strategies targeting cccDNA are discussed in detail. Thus, this review describes new insights into HBV cccDNA mechanisms and therapeutic strategies for cleaning cccDNA, which will benefit patients with liver diseases.

Insights into the post-translational modification and its emerging role in shaping the tumor microenvironment

More and more in-depth studies have revealed that the occurrence and development of tumors depend on gene mutation and tumor heterogeneity. The most important manifestation of tumor heterogeneity is the dynamic change of tumor microenvironment (TME) heterogeneity. This depends not only on the tumor cells themselves in the microenvironment where the infiltrating immune cells and matrix together forming an antitumor and/or pro-tumor network. TME has resulted in novel therapeutic interventions as a place beyond tumor beds. The malignant cancer cells, tumor infiltrate immune cells, angiogenic vascular cells, lymphatic endothelial cells, cancer-associated fibroblastic cells, and the released factors including intracellular metabolites, hormonal signals and inflammatory mediators all contribute actively to cancer progression. Protein post-translational modification (PTM) is often regarded as a degradative mechanism in protein destruction or turnover to maintain physiological homeostasis. Advances in quantitative transcriptomics, proteomics, and nuclease-based gene editing are now paving the global ways for exploring PTMs. In this review, we focus on recent developments in the PTM area and speculate on their importance as a critical functional readout for the regulation of TME. A wealth of information has been emerging to prove useful in the search for conventional therapies and the development of global therapeutic strategies.

Synthetic Lethality Screening Highlights Colorectal Cancer Vulnerability to Concomitant Blockade of NEDD8 and EGFR Pathways

Simple Summary

Identification of effective therapies for clinically aggressive, treatment-resistant colorectal cancer (CRC) remains an unmet clinical need. Targeted therapies against the epidermal growth factor receptor (EGFR) signaling axis lead to clinical benefits only in a small fraction of patients due to primary and acquired resistance. We previously showed that the NEDD8 pathway inhibitor pevonedistat induced tumor stabilization in preclinical models of aggressive CRC. Here, through synthetic lethality screenings, we found that pevonedistat could be successfully combined with EGFR pathway-targeted treatments in BRAF-mutant and RAS-RAF wild-type CRCs originally resistant to BRAF and EGFR blockade. We found that combined blockade of NEDD8 and EGFR pathways reverted compensatory feedback loops that reduced the efficacy of single treatments. Our results provide preclinical validation of a promising therapeutic strategy for clinically aggressive CRC resistant to EGFR and BRAF-targeted treatments.

Abstract

Colorectal cancer (CRC) is a heterogeneous disease showing significant variability in clinical aggressiveness. Primary and acquired resistance limits the efficacy of available treatments, and identification of effective drug combinations is needed to further improve patients’ outcomes. We previously found that the NEDD8-activating enzyme inhibitor pevonedistat induced tumor stabilization in preclinical models of poorly differentiated, clinically aggressive CRC resistant to available therapies. To identify drugs that can be effectively combined with pevonedistat, we performed a “drop-out” loss-of-function synthetic lethality screening with an shRNA library covering 200 drug-target genes in four different CRC cell lines. Multiple screening hits were found to be involved in the EGFR signaling pathway, suggesting that, rather than inhibition of a specific gene, interference with the EGFR pathway at any level could be effectively leveraged for combination therapies based on pevonedistat. Exploiting both BRAF-mutant and RAS/RAF wild-type CRC models, we validated the therapeutic relevance of our findings by showing that combined blockade of NEDD8 and EGFR pathways led to increased growth arrest and apoptosis both in vitro and in vivo. Pathway modulation analysis showed that compensatory feedback loops induced by single treatments were blunted by the combinations. These results unveil possible therapeutic opportunities in specific CRC clinical settings.

Small molecule-mediated modulation of ubiquitination and neddylation improves HSC function ex vivo

Hematopoietic stem cells (HSCs) are particularly characterized by their quiescence and self-renewal. Cell cycle regulators tightly control quiescence and self-renewal capacity. Studies suggest that modulation of ubiquitination and neddylation could contribute to HSC function via cyclin-dependent kinase inhibitors (CDKIs). S-phase kinase-associated protein 2 (SKP2) is responsible for ubiquitin-mediated proteolysis of CDKIs. Here, we modulated overall neddylation and SKP2-associated ubiquitination in HSCs by using SKP2-C25, an SKP2 inhibitor, and MLN4924 (Pevonedistat) as an inhibitor of the NEDD8 system. Treatments of SKP2-C25 and MLN4924 increased both murine and human stem and progenitor cell (HSPC) compartments. This is associated with the improved quiescence of murine HSC by upregulation of p27 and p57 CDKIs. A colony-forming unit assay showed an enhanced in vitro self-renewal potential post inhibition of ubiquitination and neddylation. In addition, MLN4924 triggered the mobilization of bone marrow HSPCs to peripheral blood. Intriguingly, MLN4924 treatment could decrease the proliferation of murine bone marrow mesenchymal stem cells or endothelial cells. These findings shed light on the contribution of SKP2, and associated ubiquitination and neddylation in HSC maintenance, self-renewal, and expansion.

Decreased KLHL3 expression is involved in the activation of WNK-OSR1/SPAK-NCC cascade in type 1 diabetic mice

Familial hyperkalemic hypertension (FHHt; also called pseudohypoaldosteronism type II) is a hereditary hypertensive disease which can be caused by mutations in four genes: WNK1 [with no lysine (K) 1], WNK4, Kelch-like3 (KLHL3), and cullin3 (CUL3). Decreased KLHL3 expression was identified as being involved in the pathogenesis of FHHt caused by cullin 3 disease mutations. Recent studies have revealed an increased WNK4 and hence Na-Cl cotransporter (NCC) activity in the db/db mice, resulting from PKC-mediated KLHL3 phosphorylation, which impairs the degradation of its substrate, WNK4. However, whether WNK4 and NCC were activated in type 1 diabetes still remains unclear. We created streptozotocin-induced type 1 diabetic mice and revealed that renal WNK-oxidative stress response kinase-1/STE20/SPS1-related proline alanine-rich kinase (OSR1/SPAK)-NCC cascade was activated, whereas KLHL3 expression was markedly decreased and CUL3 was heavily neddylated. Moreover, decreased KLHL3 was reversed and WNK1 and WNK4 abundance increased by MLN4924, a neddylation inhibitor. In vitro, our study also showed decreased KLHL3 abundance without any significant change in phosphorylated KLHL3 under high glucose exposure. These results indicate that decreased KLHL3 likely plays a role in the pathogenesis of renal sodium reabsorption in hyperglycemic conditions.

High-Content Analysis-Based Sensitivity Prediction and Novel Therapeutics Screening for c-Met-Addicted Glioblastoma

Simple Summary

Real-time ex vivo drug testing tailors individual therapeutics based on predicted drug responses. Most technologies to date rely on conventional drug screening that provides low confidence data. Here, we present high-content analysis-based drug testing of glioblastoma patients to identify the right glioblastoma patients for a given drug. This generates multi-parameter biomarker and phenotype readouts providing a better reliability of the assay. Additionally, we showed a high-content drug repurposing screen and defined a new c-Met-inhibiting function of the CDK4/6 inhibitor Abemaciclib. Large-scale high throughput screening results demonstrate that Abemaciclib sensitivity in glioblastoma patients is highly correlated with the c-Met inhibitors sensitivity, further supporting the accuracy of the platform and important new clinical implications regarding multiple functions of Abemaciclib.

Abstract

(1) Background: Recent advances in precision oncology research rely on indicating specific genetic alterations associated with treatment sensitivity. Developing ex vivo systems to identify cancer patients who will respond to a specific drug remains important. (2) Methods: cells from 12 patients with glioblastoma were isolated, cultured, and subjected to high-content screening. Multi-parameter analyses assessed the c-Met level, cell viability, apoptosis, cell motility, and migration. A drug repurposing screen and large-scale drug sensitivity screening data across 59 cancer cell lines and patient-derived cells were obtained from 125 glioblastoma samples. (3) Results: High-content analysis of patient-derived cells provided robust and accurate drug responses to c-Met-targeted agents. Only the cells of one glioblastoma patient (PDC6) showed elevated c-Met level and high susceptibility to the c-Met inhibitors. Multi-parameter image analysis also reflected a decreased c-Met expression and reduced cell growth and motility by a c-Met-targeting antibody. In addition, a drug repurposing screen identified Abemaciclib as a distinct CDK4/6 inhibitor with a potent c-Met-inhibitory function. Consistent with this, we present large-scale drug sensitivity screening data showing that the Abemaciclib response correlates with the response to c-Met inhibitors. (4) Conclusions: Our study provides a new insight into high-content screening platforms supporting drug sensitivity prediction and novel therapeutics screening.

Identification of a cullin5-RING E3 ligase transcriptome signature in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the deadliest type of brain tumor. The median survival time for patients with GBM is only 15 months, even following maximal surgical resection and chemotherapy and radiation therapy. A genetic biomarker could enable a paradigm shift in precise diagnosis, personalized therapeutics and prognosis. In this study, we employed the Chinese Glioma Genome Atlas, The Cancer Genome Atlas, and the Ivy Glioblastoma Atlas Project databases for RNA sequencing (RNA-seq) analysis and clinicopathological studies. We demonstrated that elevated expression of the RNF7, TCEB1, SOCS1 and SOCS3 genes, which encode components of cullin5-RING E3 ligase (CRL5), predict unfavorable GBM prognoses. In GBM and glioma cases carrying IDH1 mutations, SOCS1 and SOCS3 methylation was increased and their expression was downregulated. This study has thus identified a simple transcriptome signature for GBM prognosis.

Role of Ubiquitination in PTEN Cellular Homeostasis and Its Implications in GB Drug Resistance

Glioblastoma (GB) is the most common and aggressive brain malignancy, characterized by heterogeneity and drug resistance. PTEN, a crucial tumor suppressor, exhibits phosphatase-dependent (PI3K-AKT-mTOR pathway)/independent (nucleus stability) activities to maintain the homeostatic regulation of numerous physiological processes. Premature and absolute loss of PTEN activity usually tends to cellular senescence. However, monoallelic loss of PTEN is frequently observed at tumor inception, and absolute loss of PTEN activity also occurs at the late stage of gliomagenesis. Consequently, aberrant PTEN homeostasis, mainly regulated at the post-translational level, renders cells susceptible to tumorigenesis and drug resistance. Ubiquitination-mediated degradation or deregulated intracellular localization of PTEN hijacks cell growth rheostat control for neoplastic remodeling. Functional inactivation of PTEN mediated by the overexpression of ubiquitin ligases (E3s) renders GB cells adaptive to PTEN loss, which confers resistance to EGFR tyrosine kinase inhibitors and immunotherapies. In this review, we discuss how glioma cells develop oncogenic addiction to the E3s-PTEN axis, promoting their growth and proliferation. Antitumor strategies involving PTEN-targeting E3 ligase inhibitors can restore the tumor-suppressive environment. E3 inhibitors collectively reactivate PTEN and may represent next-generation treatment against deadly malignancies such as GB.

MLN4924 inhibits hedgehog signaling pathway and activates autophagy to alleviate mouse laser-induced choroidal neovascularization lesion

Neovascular age-related macular degeneration (nAMD), featured as choroidal neovascularization (CNV), can cause blindness in the elderly population. MLN4924, a highly selective small-molecule inhibitor of NEDD8 (neuronal precursor cell-expressed developmentally down-regulated protein 8)-activating enzyme (NAE), inhibits the proliferation, angiogenesis and inflammation of multiple cancers via up-regulating hedgehog pathway-regulated autophagy. MLN4924 intraperitoneal injection mitigated the leakage, area and volume of mouse laser-induced CNV lesion. Additionally, compared to CNV 7 d group, MLN4924 treated mouse retina-retinal pigment epithelium (RPE)-choroid complex showed decreased expression of hedgehog pathway-associated molecules patched 1 (PTCH1), smoothened (SMO), GLI family zinc finger 1 (GLI1) and GLI family zinc finger 2 (GLI2) with increased expression of autophagy-associated molecules sequestosome 1 (p62) and LC microtubule-associated protein 1 light chain 3 (LC3). Meanwhile, human choroidal endothelial cells (HCECs) exposed to hypoxia condition also showed decreased expression of hedgehog pathway-associated molecules and increased expression of autophagy-associated molecules. Compared to hypoxia + MLN4924 group, SMO agonist SAG up-regulated hedgehog pathway and down-regulated autophagy, whereas autophagy inhibitor PIK-III inhibited autophagy with no effect on hedgehog pathway, indicating that MLN4924 facilitated autophagy of HCECs via hindering hedgehog pathway under hypoxia condition. Finally, MLN4924 inhibited proliferation, migration and tube formation of HCECs via boosting hedgehog pathway-regulated autophagy. In summary, MLN4924 relieved the formation of mouse laser-induced CNV lesion might via up-regulating hedgehog pathway-regulated autophagy. The results provide a potential interfering strategy for nAMD targeting the autophagy of choroidal endothelial cells.