Eukaryotic Elongation Factor-2 Kinase Research Articles

Mouse KL2 is a unique MTSE involved in chromosome-based spindle organization and regulated by multiple kinases during female meiosis.

Microtubule-severing enzymes (MTSEs) play important roles in mitosis and meiosis of the primitive organisms. However, no studies have assessed their roles in mammalian meiosis of females, whose abnormality accounts for over 80% of the cases of gamete-originated human reproductive disease. In the current study, we reported that katanin-like 2 (KL2) was the only MTSE concentrating at chromosomes. Furthermore, the knockdown of KL2 significantly reduced chromosome-based increase in the microtubule (MT) polymer, increased aberrant kinetochore-MT (K-MT) attachment, delayed meiosis, and severely affected normal fertility. Importantly, we demonstrated that the inhibition of aurora B, a key kinase for correcting aberrant K-MT attachment, eliminated KL2 from chromosomes completely. KL2 also interacted with phosphorylated eukaryotic elongation factor-2 kinase; they competed for chromosome binding. We also observed that the phosphorylated KL2 was localized at spindle poles, and that KL2 phosphorylation was regulated by extracellular signal-regulated kinase 1/2. In summary, our study reveals a novel function of MTSEs in mammalian female meiosis and demonstrates that multiple kinases coordinate to regulate the levels of KL2 at chromosomes.

Abstract 461: Dual-kinase targeted miRNA nanotherapy for the treatment of triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) represents 20% of breast cancer (BC) patients (51,000 cases/year in the US). It is associated with a highly aggressive course, early metastasis and relapses, and drug-resistant phenotype. About 40% of the patients die within 5 years despite available therapies. If the disease is metastatic, patients survive only 13 months. Since TNBC does not express targetable receptors such as ER, PR, and HER2, and it is a highly heterogeneous cancer with six genetically defined sub-types, currently, there are no common actionable molecular targets and no effective targeted therapies for TNBC. microRNAs (miRNAs) are 18-20 nt long non-coding RNAs and are often dysregulated in cancer cells. Tumor-suppressive miRNAs specifically silence their protooncogenic target genes (mRNAs) by binding specifically to their 3’-UTRs located in their target mRNAs, leading to inhibition of oncogenes that play critical roles in cell proliferation, cell cycle, migration, invasion, angiogenesis, drug resistance, tumor growth, and progression. We have previously demonstrated that Eukaryotic Elongation factor-2 kinase (eEF2K) and AXL are oncogenic kinases, and their higher expression is associated with poor survival in patients with TNBC. However, currently, there is no FDA-approved eEF2K and AXL-targeted therapeutics. To effectively co-target these kinases, we extensively analyzed miRNA databases using miRNA target prediction algorithms and recently, we discovered that miR-329-3p has a specific binding site at both 3’-UTRs of eEF2K and AXL mRNAs. Analyzing the TCGA TNBC database, we found that low expression of miR-329-3p is correlated with shorter overall survival in TNBC patients, and the expression of miR-329-3p is commonly reduced or lost in TNBC patient tumors. Since the successful clinical application of miRNA-based therapeutics requires safe and effective nano-delivery systems, we have developed magnetic iron-oxide-based nanoparticles (MNPs) for the delivery of miR-329-3p. We showed that miR-329-3p significantly suppresses cell proliferation, invasion, and migration by targeting both eEF2K and AXL and their downstream mediators such as SRC/FAK and Cyclin D1 in TNBC cell lines. In vivo systemic treatment with MNPs-miR-329 completely blocks tumor growth in orthotopic MDA-MB-231 and MDA-MB-436 TNBC xenograft models in mice. Analysis of tumors shows remarkable inhibition in eEF2K and AXL expression, and clinically significant downstream targets including SRC, FAK, and Cyclin D1. We also demonstrated that miR-329 nanotherapy induces apoptosis and inhibits intratumoral proliferation in TNBC tumors in mice. Toxicity markers in mouse blood samples show that miR-329 nanotherapy is safe and not toxic to mice. Taken together, our study suggests that miR-329-3p nanotherapy may be used as a novel potential therapeutic approach in TNBC patients. Citation Format: Goknur Kara, Pinar Atalay Dundar, Nermin Kahraman, Emir Baki Denkbas, Bulent Ozpolat. Dual-kinase targeted miRNA nanotherapy for the treatment of triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 461.

Abstract 2179 The Role of an Intrinsically Disordered Loop in Regulating the Cellular Activity of Eukaryotic Elongation Factor-2 Kinase

Abstract 2179 The Role of an Intrinsically Disordered Loop in Regulating the Cellular Activity of Eukaryotic Elongation Factor-2 Kinase

Abstract 3786: In vivo miR-449b mimic-based nanotherapy suppresses growth and progression of triple-negative breast cancer

Abstract Triple-negative breast cancer (TNBC) comprises 15-20% of breast cancers and is associated with an aggressive course and the highest mortality rate in all breast cancer subtypes owing to high rates of early metastasis recurrence, and a low response to adjuvant chemotherapy. Currently, there is no effective targeted therapy strategy for TNBC due to significant genetic heterogeneity and a lack of defined molecular targets. Recent evidence from our and other laboratories revealed that non-coding RNAs such as tumor suppressor microRNAs (miRNAs) are dysregulated in cancer cells by regulating the expression of target genes (mRNAs) that are involved in critical cellular processes such as cell cycle, proliferation, differentiation, and migration/invasion, drug resistance, and tumor growth. Analyzing the TCGA-patient database, we recently found that reduced miR-449b expression was associated with significantly shorter survival in TNBC patients (n=56 patients with high expression, n=41 patients with low expression, p=0.0011). Our studies revealed that miR449b expression is reduced in TNBC cell lines and its ectopic expression using commercially available transfection reagent inhibited TNBC cell proliferation, migration, and invasion. Since in vivo delivery of miRNA therapeutics has been challenging, we developed magnetic nanoparticles for miR-449b delivery which inhibited in vitro cell proliferation, invasion, and migration. To elucidate molecular mechanisms underlying miR-449b-induced tumor suppressive effects, we investigated potential targets of miR449b using several target prediction algorithms and found that miR-449b has binding sites in the 3'-UTR of the proto-oncogene, eukaryotic elongation factor-2 kinase (eEF2K) gene. We demonstrated eEF2K expression is highly upregulated in TNBC cell lines and eEF2K expression correlates with shorter overall survival in patients with TNBC. More importantly, eEF2K expression was markedly inhibited after ectopic expression of miR-449b in TNBC cells. TNBC cells were also treated with siRNAs specific for eEF2K which led to reduced cell growth and invasion/migration, recapitulating the effects of miR-449b expression Furthermore, in vivo administration of miR-449b-loaded magnetic nanoparticles (0.6 mg/kg once a week in TNBC orthotopic xenograft models (MDA-MB-231) in mice resulted in significant inhibition of eEF2K and tumor growth. Additionally, magnetic nanoparticles-miR-449b treatment in mice did not cause detectable side effects. These findings suggest that miR-449b functions as a tumor suppressor by targeting eEF2K-mediated oncogenic signaling leading to the tumor growth and progression of TNBC. Taken together, our study suggests that the miR-449 nanotherapy using magnetic nanoparticles may be a promising therapeutic strategy that provides a safe and effective antitumor efficacy against TNBC. Citation Format: Goknur Kara, Bulent Ozpolat. In vivo miR-449b mimic-based nanotherapy suppresses growth and progression of triple-negative breast cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3786.

Identification of oxidative stress-related genes and potential mechanisms in atherosclerosis.

Atherosclerosis (AS) is the main cause of death in individuals with cardiovascular and cerebrovascular diseases. A growing body of evidence suggests that oxidative stress plays an essential role in Atherosclerosis pathology. The aim of this study was to determine genetic mechanisms associated with Atherosclerosis and oxidative stress, as well as to construct a diagnostic model and to investigate its immune microenvironment. Seventeen oxidative stress-related genes were identified. A four-gene diagnostic model was constructed using the least absolute shrinkage and selection operator (LASSO) algorithm based on these 17 genes. The area under the Receiver Operating Characteristic (ROC) curve (AUC) was 0.967. Based on the GO analysis, cell-substrate adherens junction and focal adhesion were the most enriched terms. KEGG analysis revealed that these overlapping genes were enriched in pathways associated with Alzheimer's disease and Parkinson's disease, as well as with prion disease pathways and ribosomes. Immune cell infiltration correlation analysis showed that the immune cells with significant differences were CD4 memory activated T cells and follicular helper T cells in the GSE43292 dataset and CD4 naïve T cells and CD4 memory resting T cells in the GSE57691 dataset. We identified 17 hub genes that were closely associated with oxidative stress in AS and constructed a four-gene (aldehyde dehydrogenase six family member A1 (ALDH6A1), eukaryotic elongation factor 2 kinase (EEF2K), glutaredoxin (GLRX) and l-lactate dehydrogenase B (LDHB)) diagnostic model with good accuracy. The four-gene diagnostic model was also found to have good discriminatory efficacy for the immune cell infiltration microenvironment of AS. Overall, these findings provide valuable information and directions for future research into Atherosclerosis diagnosis and aid in the discovery of biological mechanisms underlying AS with oxidative stress.

SCN5A promotes the growth and lung metastasis of triple-negative breast cancer through EF2-kinase signaling

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer often associated with early metastasis, poor prognosis, and shortened survival. The main causes of its high mortality level are attributed to significant genetic heterogenity, rapid development of chemoresistance, and a limited number of targeted therapeutics. Therefore, as described herein, we investigated the role of the SCN5A gene encoding the voltage-gated sodium ion channel NaV1.5 in vitro and in vivo in TNBC models. Cell proliferation, colony formation, invasion, western blot and in vivo analyzes were performed. We found that SCN5A gene/NaV1.5 and its neonatal spliced isoform nNaV1.5 were markedly upregulated in TNBC cells and that they promoted cell proliferation, colony formation, motility/migration, and invasion. Therapeutic targeting of NaV1.5/nNaV1.5 via systemic injection of specific siRNAs incorporated in single-lipid nanoparticles suppressed tumor growth and lung metastasis in orthotopic TNBC models. We further demonstrated that targeting of NaV1.5/nNaV1.5 expression associated with eukaryotic elongation factor-2 kinase (EF2K) expression. This approach led to the inhibition EF2K's oncogenic signaling and its clinically significant downstream targets, including integrin β1/Src/focal adhesion kinase, c-myc, cyclin D1, phosphoinositide 3-kinase/Akt, p-ERK, p-IF2α and p-PI3K. Targeting of NaV1.5/nNaV1.5 also induced robust apoptosis in TNBCs in vivo. Inhibition of both isoforms of SCN5A in TNBC cells enhanced the effect of first-line chemotherapeutics such as paclitaxel. In conclusion, our results provide the first evidence that expression of SCN5A has an important role in the growth of primary and lung-metastatic TNBCs and that targeting of NaV1.5/nNaV1.5 by systemically administered therapeutics is a potential molecularly targeted strategy to control TNBC progression and may enhance the efficacy of currently used chemotherapeutics.

MiRNA-193b-5p Suppresses Pancreatic Cancer Cell Proliferation, Invasion, Epithelial Mesenchymal Transition, and Tumor Growth by Inhibiting eEF2K.

Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer deaths in the US due to the lack of effective targeted therapeutics and extremely poor prognosis. The study aims to investigate the role of miR-193b and related signaling mechanisms in PDAC cell proliferation, invasion, and tumor growth. Using PDAC cell lines, we performed cell viability, colony formation, in vitro wound healing, and matrigel invasion assays following transfection with miR-193b mimic or control-miR. To identify potential downstream targets of miR-193b, we utilized miRNA-target prediction algorithms and investigated the regulation of eukaryotic elongation factor-2 kinase (eEF2K) and mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling pathways and mediators of epithelial mesenchymal transition (EMT). The role of miR-193b in PDAC tumorigenesis was evaluated in in vivo tumor growth of Panc-1 xenograft model in nude mice. We found that miR-193b is under expressed in PDAC cells compared to corresponding normal pancreatic epithelial cells and demonstrated that ectopic expression of miR-193b reduced cell proliferation, migration, invasion, and EMT through downregulation of eEF2K signaling in PDAC cells. miR-193b expression led to increased expression of E-Cadherin and Claudin-1 while decreasing Snail and TCF8/ZEB1 expressions via eEF2K and MAPK/ERK axis. In vivo systemic injection of miR-193b using lipid-nanoparticles twice a week reduced tumor growth of Panc-1 xenografts and eEF2K expression in nude mice. Our findings suggest that miR-193b expression suppresses PDAC cell proliferation, migration, invasion, and EMT through inhibition of eEF2K/MAPK-ERK oncogenic axis and that miR-193b-based RNA therapy might be an effective therapeutic strategy to control the growth of PDAC.

Targeting Protein Translation in Melanoma by Inhibiting EEF-2 Kinase Regulates Cholesterol Metabolism though SREBP2 to Inhibit Tumour Development.

Decreasing the levels of certain proteins has been shown to be important for controlling cancer but it is currently unknown whether proteins could potentially be targeted by the inhibiting of protein synthesis. Under this circumstance, targeting protein translation could preferentially affect certain pathways, which could then be of therapeutic advantage when treating cancer. In this report, eukaryotic elongation factor-2 kinase (EEF2K), which is involved in protein translation, was shown to regulate cholesterol metabolism. Targeting EEF2K inhibited key parts of the cholesterol pathway in cancer cells, which could be rescued by the addition of exogenous cholesterol, suggesting that it is a potentially important pathway modulated by targeting this process. Specifically, targeting EEF2K significantly suppressed tumour cell growth by blocking mRNA translation of the cholesterol biosynthesis transcription factor, sterol regulatory element-binding protein (SREBP) 2, and the proteins it regulates. The process could be rescued by the addition of LDL cholesterol taken into the cells via non-receptor-mediated-uptake, which negated the need for SREBP2 protein. Thus, the levels of SREBP2 needed for cholesterol metabolism in cancer cells are therapeutically vulnerable by targeting protein translation. This is the first report to suggest that targeting EEF2K can be used to modulate cholesterol metabolism to treat cancer.

Structure prediction of eukaryotic elongation factor-2 kinase and identification of the binding mechanisms of its inhibitors: homology modeling, molecular docking, and molecular dynamics simulation

Protein kinases emerged as one of the most successful families of drug targets due to their increased activity and involvement in mediating critical signal transduction pathways in cancer cells. Recent evidence suggests that eukaryotic elongation factor 2 kinase (eEF-2K) is a potential therapeutic target for treating some highly aggressive solid cancers, including lung, pancreatic and triple-negative breast cancers. Thus, several compounds have been developed for the inhibition of the enzyme activity, but they are not sufficiently specific and potent. Besides, the crystal structure of this kinase remains unknown. Hence, the functional organization and regulation of eEF-2K remain poorly characterized. For this purpose, we constructed a homology model of eEF-2K and then used docking methodology to better understanding the binding mechanism of eEF-2K with 58 compounds that have been proposed as existing inhibitors. The results of this analysis were compared with the experimental results and the compounds effective against eEF-2K were determined against eEF-2K as a result of both studies. And finally, molecular dynamics (MD) simulations were performed for the stability of eEF-2K with these compounds. According to these study defined that the binding mechanism of eEF-2K with inhibitors at the molecular level and elucidated the residues of eEF-2K that play an important role in enzyme selectivity and ligand affinity. This information may lead to new selective and potential drug molecules to be for inhibition of eEF-2K. Communicated by Ramaswamy H. Sarma

Increased eEF2K Promotes Glycolysis and Aggressive Behaviors of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis.

ObjectiveAggressive phenotype and abnormal glycolytic metabolism of fibroblast-like synoviocytes (FLSs) are essential to joint inflammation and damage in rheumatoid arthritis (RA). Eukaryotic elongation factor-2 kinase (eEF2K) is a negative regulator of protein synthesis and has been shown to play an important role in regulating various cellular processes and promoting glycolysis in tumor cells. However, the role of eEF2K in regulating the pathogenic FLS behaviors is unknown.MethodsA specific inhibitor of eEF2K, NH125, and siRNA were used to evaluate the role of eEF2K on RA FLSs in vitro. Collagen-induced arthritis (CIA) mice were used to evaluate the in vivo effect of eEF2K. Cell migration, invasion of RA FLSs were assessed by transwell or wound healing assays. Relative changes of cytokines were analyzed by quantitative real-time PCR, western blot and ELISA.ResultsHerein, we found an increased expression of eEF2K in synovial tissues and FLSs of RA patients. eEF2K knockdown by siRNA or treatment with NH125, an inhibitor of eEF2K, significantly reduced inflammation, migration/invasion, glucose uptake and lactate productions. eEF2K knockdown suppressed TNF-α-induced activation of NF-κB and AKT pathways in RA FLSs. Lactate reversed the inhibitory effect of eEF2K knockdown on inflammation and migration of RA FLSs. Moreover, lactate was also involved in eEF2K-mediated activation of NF-κB and AKT. NH125 treatment attenuated the severity of arthritis in collagen-induced arthritis mice.ConclusioneEF2K inhibition suppressed glycolysis and aggressive behaviors of RA FLS, which indicated that targeting eEF2K may be a new strategy for the treatment of RA.

EEF2K silencing inhibits tumour progression through repressing SPP1 and synergises with BET inhibitors in melanoma.

BackgroundDespite the remarkable breakthroughs achieved in the management of metastatic melanoma using immunotherapy and targeted therapies, long‐term clinical efficacy is often compromised due to dose‐limiting toxicity and innate or acquired resistance. Therefore, it is of vital importance to further explore the molecular mechanisms underlying melanoma progression and identify new targeted therapeutic approaches.MethodsThe function of eukaryotic elongation factor‐2 kinase (EEF2K) in melanoma were investigated in vitro and in vivo. RNA‐seq and chromatin immunoprecipitation (ChIP) assay were undertaken to explore the mechanisms. The antitumor effect of bromodomain and extra terminal domain (BET) inhibitors combined with cytarabine were assessed in melanoma both in vitro and in vivo.ResultsEEF2K silencing markedly attenuated the malignant phenotypes of melanoma cells, including proliferation, migration, invasion and metastasis. In contrast, EEF2K overexpression promoted melanoma cell proliferation, migration and invasion. Mechanistically, we demonstrated that EEF2K upregulates the phosphorylation of STAT3 (p‐STAT3) at Tyr705, which binds to the promoter region of SPP1 and enhances its transcription, thus facilitating melanoma progression. Transfection‐induced re‐expression of SPP1 partly negated the inhibitory effect of EEF2K silencing on melanoma, whereas inhibition of SPP1 or STAT3 significantly abolished the efficacy of EEF2K on melanoma cells. Intriguingly, EEF2K silencing combined with BET inhibitor treatment further inhibited cell proliferation and promoted apoptosis in melanoma. We further screened the US FDA‐approved antitumour drug library and identified cytarabine as a potential clinically applicable EEF2K inhibitor that could synergise with BET inhibitors in melanoma treatment.ConclusionEEF2K/p‐STAT3/SPP1 may be a novel oncogenic pathway in melanoma progression, which could be a target for novel combination therapy for melanoma.

Eukaryotic elongation factor 2 kinase regulates foam cell formation via translation of CD36.

Eukaryotic elongation factor 2kinase (eEF2K) is an atypical protein kinase that controls protein synthesis in cells under stress. Although well studied in cancer, less is known about its roles in chronic inflammatory diseases. Here, we examined its regulation of macrophage cholesterol handling in the context of atherosclerosis. eEF2K mRNA expression and protein activity were upregulated in murine bone marrow-derived macrophages (BMDMs) exposed to oxidized low-density lipoprotein cholesterol (oxLDL). When incubated with oxLDL, BMDMs from eEF2K knockout (Eef2k-/- ) mice formed fewer Oil Red O+ foam cells than Eef2k+/+ BMDMs (12.5%±2.3% vs. 32.3%±2.0%, p<.01). Treatment with a selective eEF2K inhibitor, JAN-384, also decreased foam cell formation for C57BL/6J BMDMs and human monocyte-derived macrophages. Disabling eEF2K selectively decreased protein expression of the CD36 cholesterol uptake receptor, mediated by a reduction in the proportion of translationally active Cd36mRNA. Eef2k-/- mice bred onto the Ldlr-/- background developed aortic sinus atherosclerotic plaques that were 30% smaller than Eef2k+/+ -Ldlr-/- mice after 16weeks of high cholesterol diet (p<.05). Although accompanied by a reduction in plaque CD36+ staining (p<.05) and lower CD36 expression in circulating monocytes (p<.01), this was not associated with reduced lipid content in plaques as measured by oil red O staining. Finally, EEF2K and CD36mRNA levels were higher in blood mononuclear cells from patients with coronary artery disease and recent myocardial infarction compared to healthy controls without coronary artery disease. These results reveal a new role for eEF2K in translationally regulating CD36 expression and foam cell formation in macrophages. Further studies are required to explore therapeutic targeting of eEF2K in atherosclerosis.

Insights Into the Pathologic Roles and Regulation of Eukaryotic Elongation Factor-2 Kinase.

Eukaryotic Elongation Factor-2 Kinase (eEF2K) acts as a negative regulator of protein synthesis, translation, and cell growth. As a structurally unique member of the alpha-kinase family, eEF2K is essential to cell survival under stressful conditions, as it contributes to both cell viability and proliferation. Known as the modulator of the global rate of protein translation, eEF2K inhibits eEF2 (eukaryotic Elongation Factor 2) and decreases translation elongation when active. eEF2K is regulated by various mechanisms, including phosphorylation through residues and autophosphorylation. Specifically, this protein kinase is downregulated through the phosphorylation of multiple sites via mTOR signaling and upregulated via the AMPK pathway. eEF2K plays important roles in numerous biological systems, including neurology, cardiology, myology, and immunology. This review provides further insights into the current roles of eEF2K and its potential to be explored as a therapeutic target for drug development.

Integrative proteomics reveals the role of E3 ubiquitin ligase SYVN1 in hepatocellular carcinoma metastasis.

BackgroundTumor metastasis is a major factor for poor prognosis of hepatocellular carcinoma (HCC), but the relationship between ubiquitination and metastasis need to be studied more systematically. We analyzed the ubiquitinome of HCC in this study to have a more comprehensive insight into human HCC metastasis.MethodsThe protein ubiquitination levels in 15 HCC specimens with vascular invasion and 15 without vascular invasion were detected by ubiquitinome. Proteins with significantly different ubiquitination levels between HCCs with and without vascular invasion were used to predict E3 ubiquitin ligases associated with tumor metastasis. The topological network of protein substrates and corresponding E3 ubiquitin ligases was constructed to identify the key E3 ubiquitin ligase. Besides, the growth, migration and invasion ability of LM3 and HUH7 hepatoma cell lines with and without SYVN1 expression interference were measured by cell proliferation assay, subcutaneous tumor assay, umphal vein endothelium tube formation assay, transwell migration and invasion assays. Finally, the interacting proteins of SYVN1 were screened and verified by protein interaction omics, immunofluorescence, and immunoprecipitation. Ubiquitin levels of related protein substrates in LM3 and HUH7 cells were compared in negative control, SYVN1 knockdown, and SYVN1 overexpression groups.ResultsIn this study, our whole‐cell proteomic dataset and ubiquitinomic dataset contained approximately 5600 proteins and 12,000 ubiquitinated sites. We discovered increased ubiquitinated sites with shorter ubiquitin chains during the progression of HCC metastasis. In addition, proteomic and ubiquitinomic analyses revealed that high expression of E3 ubiquitin‐protein ligase SYVN1 is related with tumor metastasis. Furthermore, we found that SYVN1 interacted with heat shock protein 90 (HSP90) and impacted the ubiquitination of eukaryotic elongation factor 2 kinase (EEF2K).ConclusionsThe ubiquitination profiles of HCC with and without vascular invasion were significantly different. SYVN1 was the most important E3 ubiquitin‐protein ligase responsible for this phenomenon, and it was related with tumor metastasis and growth. Therefore, SYVN1 might be a potential therapeutic target for HCC.

EMBR-20. ELONGATION CONTROL OF MRNA TRANSLATION DRIVES GROUP 3 MEDULLOBLASTOMA

Medulloblastoma (MB) is the most common pediatric intracranial tumor and leading cause of childhood related cancer deaths. Group 3 affiliation and genetic amplifications of the MYC oncogene are predictors of adverse outcome in MB, underscoring a dire need for novel and more effective therapeutic approaches. The let-7 family of small non-coding RNAs (miRNAs) is known to inhibit tumor progression and regulate metabolism by targeting and degrading several cellular mRNAs, including MYC. Indeed, let-7 miRNAs are frequently repressed in several cancer types, including in MYC-driven MB. We previously reported that the mRNA translation elongation regulator eukaryotic Elongation Factor-2 Kinase (eEF2K) is a pivotal mediator of cancer cell adaptation to nutrient deprivation. In the current work, we identified a potential binding site for let-7 miRNAs on the eEF2K 3’ untranslated region (UTR). In addition, eEF2K mRNA and let-7 miRNA expressions negatively correlate in MB, suggesting a potential regulation of the former by the latter. Let-7 miRNAs transfection decreases eEF2K mRNA and protein levels (by ~40–50%). Down-regulation of luciferase activity by let-7 miRNAs is impaired upon mutation of the let-7 binding site on the eEF2K 3’UTR. Inhibition of eEF2K significantly reduces survival of MYC-amplified MB cell lines under nutrient deprivation, altering their mRNA translation rates. Knockout of eEF2K increases survival of MYC-amplified MB xenografts when mice are kept under calorie restricted diets. We conclude that let-7 miRNAs degrade the eEF2K mRNA by binding to its 3’UTR, indicating that let-7 repression in MYC-driven MB is partially responsible for increased eEF2K levels. Moreover, the let-7-eEF2K axis constitutes a critical mechanism for MYC-driven MB adaptation to acute metabolic stress, representing a promising therapeutic target. Future therapeutic studies will aim to combine eEF2K inhibition with caloric restriction mimetic drugs, as eEF2K activity appears critical under metabolic stress conditions.

Inhibition of eEF2K synergizes with glutaminase inhibitors or 4EBP1 depletion to suppress growth of triple-negative breast cancer cells

The eukaryotic elongation factor-2 kinase, eEF2K, which restricts protein translation elongation, has been identified as a potential therapeutic target for diverse types of malignancies including triple negative breast cancer (TNBC). However, the contexts in which eEF2K inhibition is essential in TNBC and its consequences on the proteome are largely unknown. Here we show that genetic or pharmacological inhibition of eEF2K cooperated with glutamine (Gln) starvation, and synergized with glutaminase (GLS1) inhibitors to suppress growth of diverse TNBC cell lines. eEF2K inhibition also synergized with depletion of eukaryotic translation initiation factor 4E-binding protein 1 (eIF4EBP1; 4EBP1), a suppressor of eukaryotic protein translation initiation factor 4E (eIF4E), to induce c-MYC and Cyclin D1 expression, yet attenuate growth of TNBC cells. Proteomic analysis revealed that whereas eEF2K depletion alone uniquely induced Cyclin Dependent Kinase 1 (CDK1) and 6 (CDK6), combined depletion of eEF2K and 4EBP1 resulted in overlapping effects on the proteome, with the highest impact on the ‘Collagen containing extracellular matrix’ pathway (e.g. COL1A1), as well as the amino-acid transporter, SLC7A5/LAT1, suggesting a regulatory loop via mTORC1. In addition, combined depletion of eEF2K and 4EBP1 indirectly reduced the levels of IFN-dependent innate immune response-related factors. Thus, eEF2K inhibition triggers cell cycle arrest/death under unfavourable metabolic conditions such as Gln-starvation/GLS1 inhibition or 4EBP1 depletion, uncovering new therapeutic avenues for TNBC and underscoring a pressing need for clinically relevant eEF2K inhibitors.

Targeting eukaryotic elongation factor-2 kinase suppresses the growth and peritoneal metastasis of ovarian cancer

Ovarian cancer (OC) is the deadliest gynecological cancer and is currently incurable with standard treatment regimens. Early invasion, intraperitoneal metastasis, and an aggressive course are the hallmarks of OC. The major reason for poor prognosis is a lack of molecular targets and highly effective targeted therapies. Therefore, identification of novel molecular targets and therapeutic strategies is urgently needed to improve OC survival. Herein we report that eukaryotic elongation factor-2 kinase (EF2K) is highly upregulated in primary and drug-resistant OC cells and its expresssion associated with progression free survival TCGA database) and promotes cell proliferation, survival, and invasion. Downregulation of EF2K reduced expression of integrin β1 and cyclin D1 and the activity of the Src, phosphoinositide 3-kinase/AKT, and nuclear factor-κB signaling pathways. Also, in vivo, therapeutic targeting of EF2K by using single-lipid nanoparticles containing siRNA led to substantial inhibition of ovarian tumor growth and peritoneal metastasis in nude mouse models. Furthermore, EF2K inhibition led to robust apoptosis and markedly reduced intratumoral proliferation in vivo in ovarian tumor xenografts and intraperitoneal metastatic models. Collectively, our data suggest for the first time that EF2K plays an important role in OC growth, metastasis, and progression and may serve as a novel therapeutic target in OCs.

Abstract 5985: MiR-329 mimic based nano-therapy inhibits growth and progression of triple negative breast cancer

Abstract Triple-negative breast cancer (TNBC) is an incurable disease with the highest mortality rates among all breast cancer subtypes. Currently, there is no FDA-approved targeted therapies for TNBC. Significant genetic heterogeneity with six genetically defined sub-groups is considered the major reason for treatment failures and high mortality rates in TNBC patients and has been the major limitation in the identification of common molecular targets and development of targeted therapies for this cancer. Recently, interest in the development of non-coding miRNA based therapeutics has increased significantly. miRNA molecules are short, non-coding RNAs that have emerged as critical regulators of gene expression, affecting a multitude of biological processes, including cell proliferation, survival, motility, and tumorigenesis, by acting as oncogenes or tumor suppressors. Recently, first in human miRNA-targeted therapeutics were found safe and well tolerated in phase I clinical trials, suggesting that miRNA based therapeutic interventions may provide novel therapeutic options, especially for TNBC patients. However, successful clinical application of miRNA-based therapeutics requires development of safe and effective nano-delivery systems. To identify potential molecular targets we extensively analyzed miRNA databases and recently discovered that miR-329 expression is associated with significantly longer survival in patients with TNBC. More important, we found that miR-329 expression is lost or significantly reduced in the majority of TNBC cell lines. We demonstrated that in vitro expression of miR-329 significantly suppressed cell proliferation, invasion and migration. To identify molecular mechanism of miR-329 based therapy we utilized 5 different target prediction algorithms and identified that miR-329 has a binding site at 3'-UTR of EF2K gene which encodes Eukaryotic Elongation factor-2 kinase (EF2K). We found that EF2K is significantly upregulated in TNBC patients and is associated with shorter overall survival in TNBC patients. Remarkably, silencing of EF2K by siRNA recapitulated the effects of ectopic expression of miR-329 mimic and successfully suppressed growth and invasion of various TNBC cells. Furthermore, in vivo therapeutic delivery of miR-329 mimic incorporated albumin-based nanoparticles led to significant tumor suppressive effects in multiple TNBC xenograft models (MDA-MB-231 and MDA-MB-436) in mice. Importantly, albumin-based miR-329 nano-therapy in mice did not lead to any detectable side effects during the therapy, suggesting that miR-329 based therapy is safe and clinically feasible approach. Currently, we are conducting luciferase-based gene reporter assay to demonstrate that miR-329 specifically binds to 3'-UTR of EF2K mRNA and inhibits EF2K expression. We are also analyzing the tumors collected after albumin based nanoparticles-miR-329 treatment for miR-329 expression and EF2K downregulation as well as intra-tumoral proliferation markers (Ki67) and apoptosis by TUNEL. Based on clinical significance and our preliminary data, we conclude that miR-329 acts as a tumor suppressor in TNBC, and its reduced expression leads to expression of EF2K signaling. In addition, miR-329-based nano-therapy provides a safe and significant anti-tumor efficacy and may be a potential therapy for TNBC. Citation Format: Goknur Kara, Nermin Kahraman, Emir Baki Denkbas, George Calin, Bulent Ozpolat. MiR-329 mimic based nano-therapy inhibits growth and progression of triple negative breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5985.

Eukaryotic elongation factor-2 kinase (eEF2K) signaling in tumor and microenvironment as a novel molecular target

Eukaryotic elongation factor-2 kinase (eEF2K), an atypical member of alpha-kinase family, is highly overexpressed in breast, pancreatic, brain, and lung cancers, and associated with poor survival in patients. eEF2K promotes cell proliferation, survival, and aggressive tumor characteristics, leading to tumor growth and progression. While initial studies indicated that eEF2K acts as a negative regulator of protein synthesis by suppressing peptide elongation phase, later studies demonstrated that it has multiple functions and promotes cell cycle, angiogenesis, migration, and invasion as well as induction of epithelial-mesenchymal transition through induction of integrin β1, SRC/FAK, PI3K/AKT, cyclin D1, VEGF, ZEB1, Snail, and MMP-2. Under stress conditions such as hypoxia and metabolic distress, eEF2K is activated by several signaling pathways and slows down protein synthesis and helping cells to save energy and survive. In vivo therapeutic targeting of eEF2K by genetic methods inhibits tumor growth in various tumor models, validating it as a potential molecular target. Recent studies suggest that eEF2K plays a role in tumor microenvironment cells by monocyte chemoattractant protein-1 (MCP-1) and accumulation of tumor-associated macrophages. Due to its clinical significance and the pivotal role in tumorigenesis and progression, eEF2K is considered as an important therapeutic target in solid tumors. However, currently, there is no specific and potent inhibitor for translation into clinical studies. Here, we aim to systematically review current knowledge regarding eEF2K in tumor biology, microenvironment, and development of eEF2K targeted inhibitors and therapeutics.

Direct Medial Entorhinal Cortex Input to Hippocampal CA3 Is Crucial for eEF2K Inhibitor-Induced Neuronal Oscillations in the Mouse Hippocampus.

The hippocampal formation plays a vital role in memory formation and takes part in the control of the default neuronal network activity of the brain. It also represents an important structure to analyze drug-induced effects on subregion-specific synchronization of neuronal activity. However, the consequences of an altered functional state of synapses for subregion-specific synchronization of neuronal microcircuits remain to be fully understood. Therefore, we analyzed the direct interaction of neuronal microcircuits utilizing a genetically encoded calcium sensor (GCaMP6s) and local field potential (LFP) recording in acute hippocampal–entorhinal brain slices in response to a modulator of synaptic transmission. We observed that application of the eukaryotic elongation factor-2 kinase (eEF2K) inhibitor A484954, induced a large-scale synchronization of neuronal activity within different regions of the hippocampal formation. This effect was confirmed by the recording of extracellular LFPs. Further, in order to understand if the synchronized activity depended on interconnected hippocampal areas, we lesioned adjacent regions from each other. These experiments identified the origin of A484954-induced synchronized activity in the hippocampal CA3 subfield localized near the hilus of the dentate gyrus. Remarkably, the synchronization of neuronal activity in the hippocampus required an intact connection with the medial entorhinal cortex (MEC). In line with this observation, we detected an increase in neuronal activity in the MEC area after application of A484954. In summary, inhibition of eEF2K alters the intrinsic activity of interconnected neuronal microcircuits dominated by the MEC–CA3 afferents.