Abstract. The eukaryotic initiation factor (eIF)4E-binding proteins (4E-BPs) regulate cap-dependent protein translation and control the assembly of the eIF4F complex. In the present study, a phosphorylation‐deficient truncated 4E‐BP2 (eIF4FD) was constructed into the eukaryotic expression vector pSe

The eukaryotic initiation factor (eIF)4E-binding proteins (4E-BPs) regulate cap-dependent protein translation and control the assembly of the eIF4F complex. In the present study, a phosphorylation‐deficient truncated 4E‐BP2 (eIF4FD) was constructed into the eukaryotic expression vector pSecTag2, and the in vitro and in vivo effects on malignant glioma survival were determined through inhibiting eIF4F complex assembly. Cell cycle distribution analysis and TUNEL staining show that overexpression of eIF4FD suppressed cell proliferation and induced apoptosis in U251 cells. Western blotting showed that the cell cycle‐related genes cyclin D1 and C-myc, and anti-apoptotic genes B-cell lymphoma 2 (Bcl-2), Bcl-extra large and survivin were reduced following the overexpression of eIF4FD. Furthermore, eIF4FD suppressed glioma vascularization via reductions in the expression of β-catenin and vascular endothelial growth factor. In the orthotopic xenograft model, the stable expression of eIF4FD in U251 cells attenuated cell growth and increased the rate of apoptosis. Accordingly, pSecTag2‐PTD‐eIF4FD injection via the tail vein of mice also lead to cell growth inhibition and the induction of apoptosis. Therefore, the study showed that phosphorylation‐deficient truncated 4E‐BP2 efficiently inhibited eIF4E and prevented the formation of the eIF4F complex, which further contributed to the inhibition of cell proliferation and vascularization, and the induction of apoptosis. Therefore, the 4E‐BP2‐based phosphorylation‐deficient truncation designed in the present study may represent a novel approach for the targeted therapy of human malignant glioma though inhibition of the translation initiation complex. Introduction Glioma is one the most common and aggressive types of brain cancer in humans, which is characterized by rapid proliferation, high invasion and genetic alterations, and is associated with a poor prognosis in patients (1,2). Despite the significant advance in cancer treatments, the mortality rate remains high in malignant glioma (3). Therefore, it is important to investigate novel interventions or techniques for the treatment of malignant glioma. Eukaryotic initiation factors (eIFs) are well known as key mediators of protein translation initiation in eukaryotic cells. Among them, eIF4E has been recognized as being key in the initiation and development of malignant tumors (4-6). eIF4E can be combined with the scaffolding protein eIF4G and the ATP-dependent RNA helicase eIF4A to form the eIF4F complex (7), which is the rate-limiting factor in a variety of cancer-related behaviors, including cell proliferation (4), apoptosis (8,9) and angiogenesis (10,11). Importantly, the deregulation of eIF4F activity is associated with the elevation of Myc in the prelymphomatous stage of Eμ-Myc lymphoma, whereas the inhibition of eIF4F causes the decrease in cycling pre-B/B cells and tumor onset delay (12). In addition, the inhibition of eIF4F complex formation either by inhibiting the eIF4E-eIF4G interaction or by targeting eIF4A, may lead to the death of cancer cells (13). These lines of evidence suggest that the eIF4F complex may be a promising molecular target for the treatment of malignant glioma. The eIF4E binding proteins (4E-BPs) are a series of regulatory molecules involved in controlling eIF4F complex assembly. Following phosphorylation, 4E-BPs inhibit the activity of translation factor eIF4E through direct interactions (14-16). Among them, 4E-BP2 is one of the predominant 4E-BPs expressed in the brain (17), however, the associated functions remain to be fully elucidated. A previous study demonstrated that the interaction between eIF4E and 4E-BP2 inhibited eIF4F complex assembly and cap-dependent translation initiation (18). Therefore, 4E-BP2 may be a potential target for controlling cancer cell proliferation via affecting eIF4F complex assembly. In the present study, based on the evidence that 4E-BPs bind to the dorsal side of eIF4E to prevent formation of the eIF4F complex, phosphorylation-deficient truncated 4E‐BP2 (eIF4FD) was generated and constructed into the eukaryotic expression vector pSecTag2, and fused with the Inhibition of eIF4F complex loading inhibits the survival of malignant glioma QIU‐FENG DONG*, ZHI-FENG YAN*, PENG-QI LI*, XIN YANG, JUN-LI HUO and HAI-NING ZHEN Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China Received November 27, 2017; Accepted June 8, 2018 DOI: 10.3892/or.2018.6587 Correspondence to: Dr Hai‐Ning Zhen, Department of Neurosurgery, Xijing Hospital, Fourth Military Medical University, 127 Changle West Road, Xi'an, Shaanxi 710032, P.R. China E-mail: zhenhn@fmmu.edu.cn *Contributed equally