Oncogene database

1977

EIF4E

eukaryotic translation initiation factor 4E;EIF4E;eukaryotic translation initiation factor 4E

eIF-4E|eIF-4F 25 kDa subunit|eukaryotic translation initiation factor 4E-like 1|mRNA cap-binding protein

4q23

protein-coding

BACKGROUND: The proto-oncogene eIF4E has been found to be elevated in head and neck squamous cell carcinomas. In an earlier prospective study overexpression of eIF4E, detected by Western blot analysis, in histologically normal surgical margins correlated with an increased local-regional recurrence rate during a 1-year follow-up. OBJECTIVE: To test the reverse hypothesis that absence of overexpression of eIF4E in the surgical margins is a predictor for long-term survival in patients with squamous cell carcinoma of the head and neck. DESIGN: A retrospective analysis was performed on 31 patients who underwent surgery for squamous cell carcinoma of the larynx or hypopharynx. Immunohistochemical analysis was used to detect eIF4E on paraffin embedded sections of the tumor and the histologically negative surgical margins. RESULTS: ALL 31 patients overexpressed eIF4E in the tumors. Thirteen patients had no detectable level of eIF4E in the margins, and only 1 had a local-regional recurrence. The average disease-free interval in this group of patients was 82.08 months. The remaining 18 patients ALL overexpressed eIF4E in the surgical margins (eIF4E score range, 5-80). Twelve (67%) of these patients developed a recurrence; the average disease-free interval was 31.95 months. Cox regression analysis showed that eIF4E in the margin (P= .01), nodes (P= .06), site (P= .02), and age (P= .02) had significant effects on the disease-free interval. The Kaplan-Meier survival curves were significantly different for eIF4E-positive and eIF4E-negative margins (P = .002). CONCLUSIONS: eIF4E in the surgical margins is an independent prognostic factor and its absence in surgical margins may predict long-term survival. Detecting eIF4E in the margins may improve survival by determining which patients would benefit from further resection or adjuvant therapy.

p53 abnormalities constitute the most frequent genetic alterations identified in larynx cancers. p53 overexpression in histologically "tumor-free" surgical margins correlates with a high recurrence rate. However, only 50-60% of tumors overexpress p53. The tumor marker eIF4E is overexpressed in 100% of larynx cancers, and overexpression of eIF4E in histologically "tumor-free" margins predicts a significantly higher recurrence. We undertook this study to correlate the expression of p53 and eIF4E in the tumors and surgical margins of squamous cell cancers of the larynx and to determine their prognostic value. A retrospective analysis was performed on 54 patients who underwent surgery for squamous cell cancers of the larynx. Patient and tumor characteristics were reviewed, and the time to recurrence was noted. Paraffin-embedded sections from the tumors and surgical margins were immunostained with antibodies to eIF4E and p53, and a qualitative analysis was performed. ALL 54 patients (100%) overexpressed eIF4E in the primary tumor, whereas 25 of 53 patients (47%) were p53 positive. Thirty-two of the 54 patients (59%) had eIF4E-positive margins. ALL 6 of 53 patients (11%) with p53-positive margins also overexpressed eIF4E in the margins. There was a significant correlation between p53 and eIF4E being positive in the margins (Spearman s correlation coefficient, P = 0.03). Twenty-one of the 25 patients (84%) that recurred, including the 6 patients with p53-positive margins, had eIF4E-positive margins. Hence, although the univariate analysis showed that nodal status and both eIF4E and p53 expression in the margins were significant predictors of recurrence (P < 0.05), in the multivariate analyses only nodal status (P < 0.001) and eIF4E in the margins (P < 0.001) were significant predictors of recurrence. Kaplan-Meier analysis demonstrated that the disease-free intervals for eIF4E-positive margins were significantly shorter than eIF4E-negative margins (P = 0.0007). There was no additional effect to the combination of positive p53 and eIF4E margins (P = 0.21). The overexpression of eIF4E in the margins appears to be a more sensitive indicator of recurrence and may be an earlier event in the process of tumorigenesis than p53.

The promyelocytic leukemia protein PML is organized into nuclear bodies which mediate suppression of oncogenic transformation and of growth. The biochemical functions of PML bodies are unknown, despite their involvement in several human disorders. We demonstrate that eukaryotic initiation factor 4E (eIF4E) directly binds the PML RING, a domain required for association with bodies and for suppression of transformation. Nuclear eIF4E functions in nucleocytoplasmic transport of a subset of transcripts including Cyclin D1. Present studies indicate that some PML requires the evolutionarily older eIF4E protein for association with nuclear bodies. Further more, PML RING modulates eIF4E activity by drastically reducing its affinity for its substrate, 5 m(7)G cap of mRNA. We demonstrate that eIF4E requires cap binding for transport of Cyclin D1 mRNA and subsequent transformation activity. Additionally, PML reduces the affinity of eIF4E for m(7)G mRNA cap, causing a reduction in Cyclin D1 protein levels and consequent transformation inhibition. PML is the first factor shown to modulate nuclear eIF4E function. These findings provide the first biochemical framework for understanding the transformation suppression activity of PML.

OBJECTIVE: eIF4E (4E) is elevated in 100% of head and neck squamous cell carcinoma (HNSCC) and in premalignant lesions of the larynx. However, it is not elevated in normal mucosa. In this study, we hypothesize that 4E is not significantly elevated in inflammation unlike its expression in premalignant lesions of the oral cavity. STUDY DESIGN: Biopsies from the oral cavity were divided into 5 groups: (1) normal mucosa, (2) chronic inflammation, (3) mild dysplasia from leukoplakic lesions, (4) mild dysplasia in surgical margins of patients with HNSCC, and (5) HNSCC. Immunohistochemical qualitative analysis was then performed. RESULTS: None of the 15 specimens in group 1 and 100% of the 15 specimens in group 5 expressed 4E. Of the 29 specimens in group 2 only 4/29 (13%) overexpressed 4E compared with 10/31 (32%) in group 3 and 9/21 (42%) in group 4. There was a significant difference between groups 2 and 3 and groups 2 and 4 (P < 0.0001 and P < 0.003 respectively) but no significant difference between groups 1 and 2 (P = 0.13) and between groups 3 and 4 (P = 0.30). CONCLUSION: 4E is not significantly elevated in inflammation of the oral cavity thus fulfilling one of the criteria that biomarkers require to be useful in a clinical setting.

OBJECTIVES/HYPOTHESIS: The translation initiation factor eukaryotic initiation factor 4E (eIF4E) binds to the cap of messenger RNA in the first step of messenger RNA recruitment. Overexpression of eIF4E results in the upregulation of specific angiogenic factor basic fibroblast growth factor (bFGF). The study aims to demonstrate that the overexpression of eIF4E could facilitate recognizing initiation start sites for the translation of bFGF and play an important role in the tumorigenesis of laryngeal squamous cell carcinoma. STUDY DESIGN: Retrospective. METHODS: Paraffin-embedded sections of 37 samples of laryngeal squamous cell carcinoma, 10 samples of vocal cords polyps, and 20 fresh samples of laryngeal squamous cell carcinoma were analyzed using immunohistochemical streptavidin peroxidase technique, Western blot analysis, and reverse transcriptase-polymerase chain reaction. RESULTS: The overexpression of eIF4E was observed in ALL 37 paraffin-embedded samples of laryngeal squamous cell carcinoma, whereas no staining was noticed in vocal cords polyps samples. There were significant correlations between the overexpression of protein eIF4E and TN stages, histological grades, local recurrence, and the states of metastasis (P <.01). Moreover, the overexpressions of both bFGF protein and bFGF messenger RNA correlated with the histological grades and the states of metastasis (P <.01), but the overexpression of eIF4E and bFGF did not correlate with age, sex, and tumor sites (P >.05). CONCLUSIONS: Eukaryotic initiation factor 4E can enhance the expression of bFGF at translation level. The eIF4E and bFGF collaborate in tumorigenesis, development, invasion, and metastasis of laryngeal squamous cell carcinoma, in view of which the former can be considered as a tumor molecular marker and an independent prognostic molecular marker of laryngeal squamous cell carcinoma.

Overexpression of the translation initiation factor eIF4E results in transformation of normal fibroblasts as a single-hit oncogene. This implies that eIF4E must affect several pathways leading to transformation. The oncogenic potential of eIF4E is probably realized by elevating the translational efficiency of some oncogene and growth-promotion transcripts that are normally repressed by their 5 UTR (untranslated region). To address this possibility, we have cloned mRNAs whose polysomal representation increases upon overexpression of eIF4E. Among these mRNAs, we now report the isolation of a clone corresponding to the src-like kinase yes. The yes mRNA contains a long 5 UTR with characteristic features of a typical translationally repressed transcript. This was confirmed by analysis of the distribution of yes mRNA after sedimentation in sucrose gradients. Increased utilization of yes mRNA resulted in elevated expression of the protein product in cells transformed with eIF4E, and suggested that overexpression of Yes could contribute to eIF4E-mediated transformation. To test this, we monitored the malignant properties of MM3MG-4E cells after treatment with PP2, a specific inhibitor of src kinases. Growth in soft agar and saturation densities were significantly reduced after treatment with PP2, but treatment of mice harboring MM3MG-4E tumors with PP2 did not affect tumor growth. However, transformation of yes-null fibroblasts by eIF4E was significantly impaired.

OBJECTIVE: To investigate the expression of the proto-oncogene eIF4E in laryngeal squamous cell carcinoma and its relationship with clinical pathology. METHOD: Sections of 37 samples of laryngeal squamous cell carcinoma (LSCC) and 10 samples of vocal cords polyp were analyzed with anti-eIF4E polyclonal antibody utilizing SP (Streptavidin Peroxidase) immunohistochemical technique. RESULT: ALL 37 LSCC samples overexpressed eIF4E in the tumors (eIF4E score: 30 approximately 210), whereas no staining was observed in 10 samples of vocal cords polyp (eIF4E score: 0). There was a significant correlation between overexpression of protein eIF4E with T stage, N stage, histological grade, recurrence and the states of metastases (P < 0.01). It did not correlate with age, sex, and site of tumor (P > 0.05). CONCLUSION: The eIF4E plays an important role on tumorgenesis, development, invasion and metastases of laryngeal squamous cell carcinoma. There was a correlation between the overexpression of protein eIF4E with TNM stage, histological grade, recurrence and metastases. eIF4E in the laryngeal squamous cell carcinoma can be considered as an independent prognostic factor and tumour molecular marker.

The eukaryotic translation initiation factor eIF4E is deregulated in many human cancers, and its overexpression in cells leads to malignant transformation. Oncogenic properties of eIF4E are directly linked to its ability to bind 7-methyl guanosine of the 5 mRNA. Here, we observe that the antiviral guanosine analogue ribavirin binds to eIF4E with micromolar affinity at the functional site used by 7-methyl guanosine mRNA cap, competes with eIF4E:mRNA binding, and, at low micromolar concentrations, selectively disrupts eIF4E subcellular organization and transport and translation of mRNAs posttranscriptionally regulated by eIF4E, thereby reducing levels of oncogenes such as cyclin D1. Ribavirin potently suppresses eIF4E-mediated oncogenic transformation of murine cells in vitro, of tumor growth of a mouse model of eIF4E-dependent human squamous cell carcinoma in vivo, and of colony formation of eIF4E-dependent acute myelogenous leukemia cells derived from human patients. These findings describe a specific, potent, and unforeseen mechanism of action of ribavirin. Quantum mechanical and NMR structural studies offer directions for the development of derivatives with improved cytostatic and antiviral properties. In all, ribavirin s association with eIF4E may provide a pharmacologic means for the interruption of posttranscriptional networks of oncogenes that maintain and enhance neoplasia and malignancy in human cancer.

Eukaryotic cap-dependent mRNA translation is mediated by the initiation factor eIF4E, which binds mRNAs and stimulates efficient translation initiation. eIF4E is often overexpressed in human cancers. To elucidate the molecular signature of eIF4E target mRNAs, we analyzed sequence and structural properties of two independently derived polyribosome recruited mRNA datasets. These datasets originate from studies of mRNAs that are actively being translated in response to cells over-expressing eIF4E or cells with an activated oncogenic AKT: eIF4E signaling pathway, respectively. Comparison of eIF4E target mRNAs to mRNAs insensitive to eIF4E-regulation has revealed surprising features in mRNA secondary structure, length and microRNA-binding properties. Fold-changes (the relative change in recruitment of an mRNA to actively translating polyribosomal complexes in response to eIF4E overexpression or AKT upregulation) are positively correlated with mRNA G+C content and negatively correlated with total and 3 UTR length of the mRNAs. A machine learning approach for predicting the fold change was created. Interesting tendencies of secondary structure stability are found near the start codon and at the beginning of the 3 UTR region. Highly upregulated mRNAs show negative selection (site avoidance) for binding sites of several microRNAs. These results are consistent with the emerging model of regulation of mRNA translation through a dynamic balance between translation initiation at the 5 UTR and microRNA binding at the 3 UTR.

The initiation of mRNA translation is regulated by the reversible phosphorylation of several initiation factors. We report here that tumor necrosis factor-alpha (TNF) rapidly stimulates phosphorylation of one such factor, an mRNA cap binding protein, in several cell types which are important in vitro models of TNF action. This protein has been purified, sequenced, and identified as the proto-oncogene product eukaryotic initiation factor 4E. These data show that phosphorylation of a key component of the cellular translational machinery is a common early event in the various actions of TNF in diverse cell types.

The eIF4E-binding proteins (4E-BPs) are inhibitors of protein synthesis that sequester the mRNA cap-binding protein eIF4E and consequently block cell growth and proliferation. In most tumors however, their inhibitory function is compromised by major oncogenic signaling pathways. Recently, thanks to the generation of mouse genetic models, considerable progress has been made in elucidating the involvement of 4E-BPs and their unique target, eIF4E, in the process of carcinogenesis. Increasing evidence indicates that an addiction to protein synthesis emerges in cancer cells, highlighting the potential that 4E-BPs have as targets for therapeutics. In this review, we summarize the biochemical function, regulation and anti-oncogenic activity of the 4E-BPs.

The eukaryotic translation initiation factor eIF4E is a potent oncogene that promotes the nuclear export and translation of specific transcripts. Here, we have discovered that eIF4E alters the cytoplasmic face of the nuclear pore complex (NPC), which leads to enhanced mRNA export of eIF4E target mRNAs. Specifically, eIF4E substantially reduces the major component of the cytoplasmic fibrils of the NPC, RanBP2, relocalizes an associated nucleoporin, Nup214, and elevates RanBP1 and the RNA export factors, Gle1 and DDX19. Genetic or pharmacological inhibition of eIF4E impedes these effects. RanBP2 overexpression specifically inhibits the eIF4E mRNA export pathway and impairs oncogenic transformation by eIF4E. The RanBP2 cytoplasmic fibrils most likely slow the release and/or recycling of critical export factors to the nucleus. eIF4E overcomes this inhibitory mechanism by indirectly reducing levels of RanBP2. More generally, these results suggest that reprogramming the NPC is a means by which oncogenes can harness the proliferative capacity of the cell.

The eukaryotic translation initiation factor eIF4E is overexpressed in many human malignancies where it is typically a harbinger of poor prognosis. eIF4E is positioned as a nexus in post-transcriptional gene expression. To carry out these functions, eIF4E needs to bind the m(7)G cap moiety on mRNAs. It plays critical roles in mRNA translation, mRNA export, and most likely in mRNA stability as well. Through these activities, eIF4E coordinately modulates the expression of many transcripts involved in proliferation and survival. eIF4E function is controlled by interactions with protein cofactors in concert with many signaling pathways, including Ras, Mnk, Erk, MAPK, PI3K, mTOR, and Akt. This review describes the eIF4E activity and provides several examples of cellular control mechanisms. Further, we describe some therapeutic strategies in preclinical and clinical development.

2,3-Dihydro-5-methyl-3-([morpholinyl]methyl)pyrollo(1,2,3-de)-1,4-benzoxazinyl]-[ 1-naphthaleny]methanone [WIN 55,212-2, (WIN)] is a synthetic cannabinoid that inhibits RKO, HT-29, and SW480 cell growth, induced apoptosis, and downregulated expression of survivin, cyclin D1, EGF receptor (EGFR), VEGF, and its receptor (VEGFR1). WIN also decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, and this is consistent with the observed downregulation of the aforementioned Sp-regulated genes. In addition, we also observed by RNA interference (RNAi) that the oncogenic cap protein eIF4E was an Sp-regulated gene also downregulated by WIN in colon cancer cells. WIN-mediated repression of Sp proteins was not affected by cannabinoid receptor antagonists or by knockdown of the receptor but was attenuated by the phosphatase inhibitor sodium orthovanadate or by knockdown of protein phosphatase 2A (PP2A). WIN-mediated repression of Sp1, Sp3, and Sp4 was due to PP2A-dependent downregulation of microRNA-27a (miR-27a) and induction of miR-27a-regulated ZBTB10, which has previously been characterized as an "Sp repressor." The results show that the anticancer activity of WIN is due, in part, to PP2A-dependent disruption of miR-27a:ZBTB10 and ZBTB10-mediated repression of Sp transcription factors and Sp-regulated genes, including eIF4E.

High activation of the PI3K-AKT-mTOR pathway is characteristic for T-cell acute lymphoblastic leukemia (T-ALL). The activity of the master regulator of this pathway, PTEN, is often impaired in T-ALL. However, experimental evidence suggests that input from receptor tyrosine kinases (RTKs) is required for sustained mTOR activation, even in the absence of PTEN. We previously reported the expression of Neurotrophin receptor tyrosine kinases (TRKs) and their respective ligands in primary human leukemia samples. In the present study we aimed to dissect the downstream signaling cascades of TRK-induced T-ALL in a murine model and show that T-ALLs induced by deregulated receptor tyrosine kinase signaling acquire activating mutations in Notch1 and lose PTEN during clonal evolution. Some clones additionally lost one allele of the homeodomain transcription factor Cux1. ALL events independently led to a gradual hyperactivation of both mTORC1 and mTORC2 signaling. We dissected the role of the individual mTOR complexes by shRNA knockdown and found that the separate depletion of mTORC1 or mTORC2 reduced the growth of T-ALL blasts, but was not sufficient to induce apoptosis. In contrast, knockdown of the mTOR downstream effector eIF4E caused a striking cytotoxic effect, demonstrating a critical addiction to cap-dependent mRNA-translation. Although high mTORC2-AKT activation is commonly associated with drug-resistance, we demonstrate that T-ALL displaying a strong mTORC2-AKT activation were specifically susceptible to 4EGI-1, an inhibitor of the eIF4E-eIF4G interaction. To decipher the mechanism of 4EGI-1, we performed a genome-wide analysis of mRNAs that are translationally regulated by 4EGI-1 in T-ALL. 4EGI-1 effectively reduced the ribosomal occupancy of mRNAs that were strongly upregulated in T-ALL blasts compared with normal thymocytes including transcripts important for translation, mitochondria and cell cycle progression, such as cyclins and ribosomal proteins. These data suggest that disrupting the eIF4E-eIF4G interaction constitutes a promising therapy strategy in mTOR-deregulated T-cell leukemia.

Targeting protein-protein interacting sites for potential therapeutic applications is a challenge in the development of inhibitors, and this becomes more difficult when these interfaces are relatively planar, as in the eukaryotic translation initiation factor 4E (eIF4E) protein. eIF4E is an oncogene that is overexpressed in numerous forms of cancer, making it a prime target as a therapeutic molecule. We report here the presence of a cryptic pocket at the protein-binding interface of eIF4E, which opens transiently during molecular dynamics simulations of the protein in solvent water and is observed to be stable when solvent water is mixed with benzene molecules. This pocket can also be seen in the ensemble of structures available from the solution-state conformations of eIF4E. The accessibility of the pocket is gated by the side-chain transitions of an evolutionarily conserved tryptophan residue. It is found to be feasible for accommodating clusters of benzene molecules, which signify the plasticity and ligandability of the pocket. We also observe that the newly formed cavity provides a favorable binding environment for interaction of a well-recognized small molecule inhibitor of eIF4E. The occurrence of this transiently accessible cavity highlights the existence of a more pronounced binding groove in a region that has traditionally been considered to be planar. Together, the data suggest that an alternate binding cavity exists on eIF4E and could be exploited for the rational design and development of a new class of lead compounds against the protein.

RNA-binding proteins (RBPs) have important roles in tumorigenesis. Although IGF2BP3, an evolutionally conserved RBP, has been reported as a useful diagnostic marker for various cancers and has been considered a regulator of tumorigenesis, little is known of the function of IGF2BP3 because of lack of information regarding IGF2BP3 target mRNAs. Here, we report the identification of IGF2BP3 target mRNAs and IGF2BP3 function in cancer proliferation. We identified mRNAs with altered expression in IGF2BP3-depleted cells by massive sequencing analysis and IGF2BP3-binding RNAs by immunoprecipitation of IGF2BP3 followed by massive sequencing analysis, resulting in the identification of 110 candidates that are negatively regulated by IGF2BP3. We found that IGF2BP3 destabilized EIF4E-BP2 and MEIS3 mRNAs. Co-immunoprecipitation analysis revealed the interaction between IGF2BP3 and ribonucleases such as XRN2 and exosome component. The retarded proliferation of IGF2BP3-depleted cells was partially rescued by the depletion of EIF4E-BP2, which negatively regulates eukaryotic translation initiation factor 4E (eIF4E), an activator of translation and a well-known proto-oncogene. Consistent with this observation, IGF2BP3 depletion reduced phosphorylated eIF4E, the active form, and translational efficiency of eIF4E target transcripts. Reduction of phosphorylated eIF4E by IGF2BP3 depletion was rescued by EIF4E-BP2 depletion. At last, we found an inverse correlation between the expression level of IGF2BP3 and EIF4E-BP2 in human lung adenocarcinoma tissues. Together, these results suggest that IGF2BP3 promotes eIF4E-mediated translational activation through the reduction of EIF4E-BP2 via mRNA degradation, leading to enhanced cell proliferation. This is the first report demonstrating that IGF2BP3 is an RNA-destabilizing factor. Notably, here we provide the first evidence for the functional linkage between two previously well-known cancer biomarkers, IGF2BP3 and eIF4E.Oncogene advance online publication, 2 November 2015; doi:10.1038/onc.2015.410.

The eukaryotic translation initiation factor eIF-4E binds to the cap structure of mRNAs as one component of the eIF-4 translation initiation complex, which mediates the recruitment of mRNA to the ribosomes. Overexpression of eIF-4E can result in oncogenic transformation and uncontrolled growth of mammalian cells, presumably by facilitating the expression of growth-control gene products which are normally translationally repressed. Whereas the mechanism of eIF-4E-mediated transformation is being actively pursued, clinical investigations into the expression of eIF-4E in prevalent human cancers are lacking. We have recently initiated a screen of breast carcinomas by probing with eIF-4E antiserum. Using Western blots, we have analyzed the level of eIF-4E in 38 carcinomas, 7 normal samples and 3 fibroadenomas. We found that eIF-4E was elevated 3- to 10-fold in virtually ALL the carcinomas we analyzed, but not in fibroadenomas. This analysis was also confirmed by immunohistological staining in situ, showing that overexpression of eIF-4E can be readily identified at the single-cell level. Our results suggest that an elevation of eIF-4E may be an essential component in the development of breast cancer.

Head and neck squamous cell cancers (HNSCC) have a high local recurrence rate due to incomplete tumor resection. The use of molecular markers to establish surgical margins may decrease local recurrence. Surgical margins are determined by histopathologic analysis on frozen sections. We postulate that genetic and molecular changes precede gross histologic alterations. tumor markers may improve the reliability of pathology examination, but those evaluated to date lack the sensitivity needed for routine clinical use. Western blot analysis showed elevated eIF4E in ALL 26 HNSCC in contrast to its low expression in benign lesions. Surgical margins were analysed for eIF4E in 23 patients. Twelve patients showed elevated eIF4E in histologically negative margins. cancer has recurred in 5 of the 12 patients as opposed to none of the 11 patients with eIF4E negative margins (P= 0.02, Log rank test). This is the first report of eIF4E in HNSCC, as a sensitive and specific marker for HNSCC, with potential for defining clear resection margins. The correlation between elevated levels of eIF4E at the margins and recurrence highlights its ability to detect malignant cells prior to clear-cut alterations in morphology. The accuracy and simplicity of these assays underscore the usefulness of eIF4E in managing HNSCC.