p150 expression and its prognostic value in squamous-cell carcinoma of the esophagus

EIF3B stabilizes PCNA by counteracting SYVN1-mediated ubiquitination to serve as a promotor in cholangiocarcinoma

Cholangiocarcinoma, a prevalent hepatic malignancy, exhibits a progressively rising incidence. While Eukaryotic translation initiation factor 3 subunit B (EIF3B) has been implicated in the occurrence and development of various cancers, its specific roles in cholangiocarcinoma remain unexplored. Immunohistochemical (IHC) analysis was employed to detect EIF3B/PCNA expression in cholangiocarcinoma. Cells were manipulated using short hairpin RNA (shRNA)-mediated lentiviruses or overexpression plasmids. Statistical significance was assessed using the Student's t-test and one-way ANOVA, with P < 0.05 considered statistically significant. EIF3B exhibited robust expression in cholangiocarcinoma, demonstrating a significant correlation with the pathological grade of cholangiocarcinoma patients. Furthermore, modulation of EIF3B expression, either depletion or elevation, demonstrated the ability to inhibit or enhance cholangiocarcinoma cell survival and migration in vitro. Mechanistically, we identified Proliferating Cell Nuclear Antigen (PCNA) as a downstream gene of EIF3B, driving cholangiocarcinoma. EIF3B stabilized PCNA by inhibiting PCNA ubiquitination, a process mediated by E3 ligase SYVN1. Similar to EIF3B, PCNA levels were also abundant in cholangiocarcinoma, and knocking down PCNA impeded cholangiocarcinoma development. Intriguingly, silencing PCNA attenuated the promotion induced by EIF3B overexpression. Furthermore, the elevated P21 protein level in shEIF3B RBE cells was partially attenuated after UC2288 (P21 signaling pathway inhibitor) treatment. Our findings underscored the potential of EIF3B as a therapeutic target for cholangiocarcinoma. Unraveling its functions holds promise for the development of more specific and effective targeted therapy strategies.

Eukaryotic initiation factor 3a promotes the development of diffuse large B-cell lymphoma through regulating cell proliferation

BACKGROUND

One-third of diffuse large B-cell lymphoma (DLBCL) patients suffer relapse after standard treatment. Eukaryotic initiation factor 3a (eIF3a) is a key player in the initial stage of translation, which has been widely reported to be correlated with tumorigenesis and therapeutic response. This study aimed to explore the biological role of eIF3a, evaluate its prognostic and therapeutic potential in DLBCL.

METHODS

RNA-seq datasets from GEO database were utilized to detect the expression and prognostic role of eIF3a in DLBCL patients. Protein level of eIF3a was estimated by western blot and immunohistochemical. Next, DLBCL cells were transfected with lentiviral vector either eIF3a-knockdown or empty to assess the biological role of eIF3a. Then, samples were divided into 2 clusters based on eIF3a expression and differentially expressed genes (DEGs) were identified. Function enrichment and mutation analysis of DEGs were employed to detect potential biological roles. Moreover, we also applied pan-cancer and chemosensitivity analysis for deep exploration.

RESULTS

eIF3a expression was found to be higher in DLBCL than healthy controls, which was associated with worse prognosis. The expression of eIF3a protein was significantly increased in DLBCL cell lines compared with peripheral blood mononuclear cells (PBMCs) from healthy donors. eIF3a knockdown inhibited the proliferation of DLBCL cells and the expression of proliferation-related proteins and increase cell apoptosis rate. Besides, 114 DEGs were identified which had a close linkage to cell cycle and tumor immune. eIF3a and DEGs mutations were found to be correlated to chemosensitivity and vital signal pathways. Pan-cancer analysis demonstrated that high eIF3a expression was associated with worse prognosis in several tumors. Moreover, eIF3a expression was found to be related to chemosensitivity of several anti-tumor drugs in DLBCL, including Vincristine and Wee1 inhibitor.

CONCLUSIONS

We firstly revealed the high expression and prognostic role of eIF3a in DLBCL, and eIF3a might promote the development of DLBCL through regulating cell proliferation and apoptosis. eIF3a expression was related to immune profile and chemosensitivity in DLBCL. These results suggest that eIF3a could serve as a potential prognostic biomarker and therapeutic target in DLBCL.

Translation initiation factor eIF3a regulates glucose metabolism and cell proliferation via promoting small GTPase Rheb synthesis and AMPK activation

Eukaryotic translation initiation factor 3 subunit A (eIF3a), the largest subunit of the eIF3 complex, has been shown to be overexpressed in malignant cancer cells, potentially making it a proto-oncogene. eIF3a overexpression can drive cancer cell proliferation but contributes to better prognosis. While its contribution to prognosis was previously shown to be due to its function in suppressing synthesis of DNA damage repair proteins, it remains unclear how eIF3a regulates cancer cell proliferation. In this study, we show using genetic approaches that eIF3a controls cell proliferation by regulating glucose metabolism via the phosphorylation and activation of AMP-activated protein kinase alpha (AMPKα) at Thr¹⁷² in its kinase activation loop. We demonstrate that eIF3a regulates AMPK activation mainly by controlling synthesis of the small GTPase Rheb, largely independent of the well-known AMPK upstream liver kinase B1 and Ca²⁺/calmodulin-dependent protein kinase kinase 2, and also independent of mammalian target of rapamycin signaling and glucose levels. Our findings suggest that glucose metabolism in and proliferation of cancer cells may be translationally regulated via a novel eIF3a–Rheb–AMPK signaling axis.

eIF3a-PPP2R5A-mediated ATM/ATR dephosphorylation is essential for irinotecan-induced DNA damage response

Objectives

The individual differences and pervasive resistance seriously hinder the optimization of irinotecan‐based therapeutic effectiveness. Eukaryotic translation initiation factor 3a (eIF3a) plays a key role in tumour occurrence, prognosis and therapeutic response. This study focused on the role of eIF3a in irinotecan‐induced DNA damage response.

Materials and Methods

The cck8 cell viability and clone survival analyses were used to test the regulatory role of eIF3a on irinotecan sensitivity in HT29 and CACO2 cell lines in vitro. This regulatory role was also verified in vivo by conducting subcutaneous xenograft model. Irinotecan‐induced DNA damage, cell cycle arrest and apoptosis were tested by flow cytometry analysis, TUNEL staining, western blot and comet assays. The immunofluorescence, co‐IP, luciferase reporter assay, RIP and flow cytometric analyses were carried out to investigate the underline mechanism.

Results

We demonstrated that eIF3a continuously activates ATM/ATR signal by translationally inhibiting PPP2R5A, a phosphatase that directly dephosphorylates and inactivates ATM/ATR after DNA repair complete. Suppression of PPP2R5A resulted in chronic ATM/ATR phosphorylation and activation, impairing DNA repair and enhancing irinotecan sensitivity.

Conclusions

Our study suggested eIF3a with a high potential to influence phenotypic functions, which may contribute substantially to the early identification of susceptible individuals and the provision of personalized medication to irinotecan‐treated patients.

The Downregulation of eIF3a Contributes to Vemurafenib Resistance in Melanoma by Activating ERK via PPP2R1B

Vemurafenib, a BRAF V600E inhibitor, provides therapeutic benefits for patients with melanoma, but the frequent emergence of drug resistance remains a challenge. An understanding of the mechanisms underlying vemurafenib resistance may generate novel therapeutic strategies for patients with melanoma. Here, we showed that eIF3a, a translational regulatory protein, was an important mediator involved in vemurafenib resistance. eIF3a was expressed at significantly lower levels in vemurafenib-resistant A375 melanoma cells (A375R) than in parental A375 cells. Overexpression of eIF3a enhanced the sensitivity to BRAF inhibitors by reducing p-ERK levels. Furthermore, eIF3a controlled ERK activity by regulating the expression of the phosphatase PPP2R1B via a translation mechanism, thus determining the sensitivity of melanoma cells to vemurafenib. In addition, a positive correlation between eIF3a and PPP2R1B expression was also observed in tumor samples from the Human Protein Atlas and TCGA databases. In conclusion, our studies reveal a previously unknown molecular mechanism of BRAF inhibitor resistance, which may provide a new strategy for predicting vemurafenib responses in clinical treatment.

The effect of eIF3a on anthracycline-based chemotherapy resistance by regulating DSB DNA repair

BACKGROUND

Anthracycline are inhibitors of topoisomerase II leading to DNA double strand breaks, and it is widely used for treatment of breast cancer. eIF3a is the largest subunit of eukaryotic translation initiation factor 3 (eIF3) and highly expressed in breast cancer. In this study, we investigated the role of eIF3a in DSB DNA repair and the response of breast cancer patients to anthracycline-based chemotherapy.

METHODS

MTT assay was used to detect anthracycline sensitivity in cell lines. Real-time reverse transcriptase PCR, western blotting and immunofluorescence were performed to assess changes in gene expression levels. Cometassay and end-joining activity assay were conducted to explore the effect of eIF3a in NHEJ repair. Luciferase reporter assay was performed to detect LIG4 5'UTR activity. Immunohistochemistry was used to detect eIF3a, LIG4 and DNA-PKcs expression levels in breast cancer tissues.

RESULTS

The results showed that eIF3a increased cellular response to anthracyclines by regulating DSB repair activity via influencing the expression of LIG4 and DNA-PKcs at translational level. Breast cancer patients with high level of eIF3a or low level of LIG4 or low level of DNA-PKcs had better anthracycline-based chemotherapy prognosis compared. Moreover, Combined expressions of eIF3a, LIG4 and DNA-PKcs could be better to predict PFS in breast cancer patients with anthracycline-based chemotherapy.

CONCLUSION

Our findings suggest that eIF3a effects anthracycline-based chemotherapy response by regulating DSB DNA repair.

Knockdown of eIF3a attenuated cell growth in K1 human thyroid cancer cells

BACKGROUND

In ribosome establishment and the initiation of translation, eukaryotic translation initiation factor (eIF) 3a is a pivotal functional subunit of the eIF3 complex. In various cancer types, abnormal eIF3a expression plays an important role in tumorigenesis.

OBJECTIVE

We aimed to explore the role of eIF3a in human thyroid cancer (TC).

MATERIAL AND METHODS

The expression of eIF3a was determined in TC tissues by qRT-PCR and immunohistochemistry (IHC) assay, respectively. In addition, the expression of eIF3a in K1 and BCPAP cells were detected by qRT-PCR. Cell proliferation, cell cycle, and cell apoptosis were assessed after eIF3a knockdown in K1 in cell line.

RESULTS

The expression of eIF3a mRNA was high in TC tissues and cancer cell lines. Moreover, eIF3a expression in TC tissues indicated that high eIF3a level was associated with tumor grade. In addition, eIF3a knockdown resulted in a significantly decrease in cell proliferation and increased the apoptosis of K1 cells. Cell cycle was arrested in both the S and G2/M phase. The levels of phosphorylated ERK1/2 and surviving were decreased after eIF3a knockdown.

CONCLUSION

Our study suggested that eIF3a contributed to TC cell proliferation. It may be a promising target for gene therapy in human thyroid cancer.

eIF3i regulation of protein synthesis, cell proliferation, cell cycle progression, and tumorigenesis

eIF3i, a 36-kDa protein, is a putative subunit of the eIF3 complex important for translation initiation of mRNAs. It is a WD40 domain-containing protein with seven WD40 repeats that forms a β-propeller structure with an important function in pre-initiation complex formation and mRNA translation initiation. In addition to participating in the eIF3 complex formation for global translational control, eIF3i may bind to specific mRNAs and regulate their translation individually. Furthermore, eIF3i has been shown to bind to TGF-β type II receptor and participate in TGF-β signaling. It may also participate in and regulate other signaling pathways including Wnt/β-catenin pathway via translational regulation of COX-2 synthesis. These multiple canonical and noncanonical functions of eIF3i in translational control and in regulating signal transduction pathways may be responsible for its role in cell differentiation, cell cycle regulation, proliferation, and tumorigenesis. In this review, we will critically evaluate recent progresses and assess future prospects in studying eIF3i.

eIF3a Regulation of NHEJ Repair Protein Synthesis and Cellular Response to Ionizing Radiation

Translation initiation in protein synthesis regulated by eukaryotic initiation factors (eIFs) is a crucial step in controlling gene expression. eIF3a has been shown to regulate protein synthesis and cellular response to treatments by anticancer agents including cisplatin by regulating nucleotide excision repair. In this study, we tested the hypothesis that eIF3a regulates the synthesis of proteins important for the repair of double-strand DNA breaks induced by ionizing radiation (IR). We found that eIF3a upregulation sensitized cellular response to IR while its downregulation caused resistance to IR. eIF3a increases IR-induced DNA damages and decreases non-homologous end joining (NHEJ) activity by suppressing the synthesis of NHEJ repair proteins. Furthermore, analysis of existing patient database shows that eIF3a expression associates with better overall survival of breast, gastric, lung, and ovarian cancer patients. These findings together suggest that eIF3a plays an important role in cellular response to DNA-damaging treatments by regulating the synthesis of DNA repair proteins and, thus, eIIF3a likely contributes to the outcome of cancer patients treated with DNA-damaging strategies including IR.

Circular RNA screening from EIF3a in lung cancer

Eukaryotic initiation factor 3 (EIF3) is one of the largest and most complex translation initiation factors, which consists of 13 subunits named eukaryotic translation initiation factor 3 subunit A (EIF3a) to EIF3m. EIF3a is the largest subunit of EIF3. Previous studies suggested that EIF3a is a housekeeping gene, recent results have found that EIF3a is closely related to the tumorigenesis and drug resistance. Circular RNAs (circRNAs) derived from biologically important gene can play an important role in gene regulation. However, the mechanism underlying circRNAs’ biological functions is not well understood yet. In this work, we screened 31 EIF3a‐derived circRNAs, in which two circEIF3as were identified to be correlated with cisplatin drug sensitivity in lung cancer. Two circEIF3as were found involved in RNA‐binding proteins‐mediated biological processes and may be related to translational regulation according to bioinformatics analyses. CircEIF3as, the transcriptional initiation factor EIF3a transcribed circRNAs, are associated with both drug sensitivity and translation regulation. These findings mean that they may have a functional synergy effect with EIF3a or be valuable therapeutic targets for treatment like EIF3a. This is the first study that exploits circRNAs screening from EIF3a in lung cancer, our findings provide a novel perspective on the function of EIF3a and circEIF3as in lung cancer.

The function and clinical significance of eIF3 in cancer

Abnormal regulation of gene expression is essential for tumorigenesis. Several studies indicate that regulation of oncogene expression and neoplastic transformation are controlled by subunits of eukaryotic translation initiation factors (eIFs). Eukaryotic translation initiation factor 3 (eIF3) is the largest (800 kDa) and the most complex mammalian initiation factor. It is composed of 13 non-identical polypeptides designated as eIF3a-m and plays a pivotal role in protein synthesis that bridges the 43S pre-initiation complex and eIF4F-bound mRNA. However, the functional roles of individual subunits are not yet very clear. This review presents on several of aberrant expressed eIF3 subunits which are detected in various human cancers and the associated mechanisms have been acknowledged or are still not sure. Finally, identifying novel targets and biomarkers for caner is of great importance in early diagnosis and treatment of cancer. eIF3 may be a novel target molecule in drug development for cancer treatment and prevention.

eIF3: a factor for human health and disease

The eukaryotic initiation factor 3 (eIF3) is one of the most complex translation initiation factors in mammalian cells, consisting of several subunits (eIF3a to eIF3m). It is crucial in translation initiation and termination, and in ribosomal recycling. Accordingly, deregulated eIF3 expression is associated with different pathological conditions, including cancer. In this manuscript, we discuss the interactome and function of each subunit of the human eIF3 complex. Furthermore, we review how altered levels of eIF3 subunits correlate with neurodegenerative disorders and cancer onset and development; in addition, we evaluate how such misregulation may also trigger infection cascades. A deep understanding of the molecular mechanisms underlying eIF3 role in human disease is essential to develop new eIF3-targeted therapeutic approaches and thus, overcome such conditions.

eIF3a: A new anticancer drug target in the eIF family

eIF3a is the largest subunit of eIF3, which is a key player in all steps of translation initiation. During the past years, eIF3a is recognized as a proto-oncogene, which is an important discovery in this field. It is widely reported to be correlated with cancer occurrence, metastasis, prognosis, and therapeutic response. Recently, the mechanisms of eIF3a action in the carcinogenesis are unveiled gradually. A number of cellular, physiological, and pathological processes involving eIF3a are identified. Most importantly, it is emerging as a new potential drug target in the eIF family, and some small molecule inhibitors are being developed. Thus, we perform a critical review of recent advances in understanding eIF3a physiological and pathological functions, with specific focus on its role in cancer and anticancer drug targets.

Eukaryotic translation initiation factors and cancer

Recent technological advancements have shown tremendous mechanistic accomplishments in our understanding of the mechanism of messenger RNA translation in eukaryotic cells. Eukaryotic messenger RNA translation is very complex process that includes four phases (initiation, elongation, termination, and ribosome recycling) and diverse mechanisms involving protein and non-protein molecules. Translation regulation is principally achieved during initiation step of translation, which is organized by multiple eukaryotic translation initiation factors. Eukaryotic translation initiation factor proteins help in stabilizing the formation of the functional ribosome around the start codon and provide regulatory mechanisms in translation initiation. Dysregulated messenger RNA translation is a common feature of tumorigenesis. Various oncogenic and tumor suppressive genes affect/are affected by the translation machinery, making the components of the translation apparatus promising therapeutic targets for the novel anticancer drug. This review provides details on the role of eukaryotic translation initiation factors in messenger RNA translation initiation, their contribution to onset and progression of tumor, and how dysregulated eukaryotic translation initiation factors can be used as a target to treat carcinogenesis.

Silencing of translation initiation factor eIF3b promotes apoptosis in osteosarcoma cells

Objectives

Eukaryotic translation initiation factor 3 (eIF3) is a multi-subunit complex that plays a critical role in translation initiation. Expression levels of eIF3 subunits are elevated or decreased in various cancers, suggesting a role for eIF3 in tumorigenesis. Recent studies have shown that the expression of the eIF3b subunit is elevated in bladder and prostate cancer, and eIF3b silencing inhibited glioblastoma growth and induced cellular apoptosis. In this study, we investigated the role of eIF3b in the survival of osteosarcoma cells.

Methods

To investigate the effect of eIF3b on cell viability and apoptosis in osteosarcoma cells, we first examined the silencing effect of eIF3b in U2OS cells. Cell viability and apoptosis were examined by the Cell Counting Kit-8 (CCK-8) assay and Western blot, respectively. We also performed gene profiling to identify genes affected by eIF3b silencing. Finally, the effect of eIF3b on cell viability and apoptosis was confirmed in multiple osteosarcoma cell lines.

Results

eIF3b silencing decreased cell viability and induced apoptosis in U2OS cells, and by using gene profiling we discovered that eIF3b silencing also resulted in the upregulation of tumour necrosis factor receptor superfamily member 21 (TNFRSF21). We found that TNFRSF21 overexpression induced cell death in U2OS cells, and we confirmed that eIF3b silencing completely suppressed cell growth in multiple osteosarcoma cell lines. However, eIF3b silencing failed to suppress cell growth completely in normal fibroblast cells.

Conclusion

Our data led us to conclude that eIF3b may be required for osteosarcoma cell proliferation by regulating TNFRSF21 expression.

Cite this article: Y. J. Choi, Y. S. Lee, H. W. Lee, D. M. Shim, S. W. Seo. Silencing of translation initiation factor eIF3b promotes apoptosis in osteosarcoma cells. Bone Joint Res 2017;6:186–193. DOI: 10.1302/2046-3758.63.BJR-2016-0151.R2.

MiR-488 inhibits proliferation and cisplatin sensibility in non-small-cell lung cancer (NSCLC) cells by activating the eIF3a-mediated NER signaling pathway

Our previous studied indicated that eukaryotic translation initiation factor 3a (eIF3a) increases the sensitive of platinum-based chemotherapy in lung cancer. MiRNAs play an important role in lung carcinogenesis and drug response. In this study, we aimed to identify potential endogenous miRNAs that inhibit eIF3a expression and determine their influence of this inhibition on cisplatin resistance. Using bioinformatics analysis prediction and confirmation with dual-luciferase reporter assays, we found that miRNA-488 inhibited eIF3a expression by directly binding to the 3’UTR of eIF3a. In addition, the overexpression of miRNA-488 inhibited cell migration and invasion in A549 cells, and also inhibited cell proliferation, cell cycle progression by elevated P27 expression. Compared to the parental cell line, A549/cisplatin (DDP) resistant cells exhibited a higher level of miRNA-488. Moreover, we found that miRNA-488 was associated with cisplatin resistance in three NSCLC cells (A549, H1299 and SK-MES-1). The mechanism of miRNA-488 induced cisplatin resistance was that miRNA-488 activated nucleotide excision repair (NER) by increasing the expression of Replication Protein A (RPA) 14 and Xeroderma pigmentosum group C (XPC). In conclusion, our results demonstrated that miRNA-488 is a tumor suppressor miRNA that acts by targeting eIF3a. Moreover, miRNA-488 also participates in eIF3a mediated cisplatin resistance in NSCLC cells.

eIF3 Regulation of Protein Synthesis, Tumorigenesis, and Therapeutic Response

Translation initiation is the rate-limiting step of protein synthesis and highly regulated. Eukaryotic initiation factor 3 (eIF3) is the largest and most complex initiation factor consisting of 13 putative subunits. A growing number of studies suggest that eIF3 and its subunits may represent a new group of proto-oncogenes and associates with prognosis. They regulate translation of a subset of mRNAs involved in many cellular processes including proliferation, apoptosis, DNA repair, and cell cycle. Therefore, unveiling the mechanisms of eIF3 action in tumorigenesis may help identify attractive targets for cancer therapy. Here, we describe a series of methods used in the study of eIF3 function in regulating protein synthesis, tumorigenesis, and cellular response to therapeutic treatments.

Eukaryotic Translation Initiation Factor 3a (eIF3a) Promotes Cell Proliferation and Motility in Pancreatic Cancer

Identifying a target molecule that is crucially involved in pancreatic tumor growth and metastasis is necessary in developing an effective treatment. The study aimed to investigate the role of the eukaryotic translation initiation factor 3a (eIF3a) in the cell proliferation and motility in pancreatic cancer. Our data showed that the expression of eIF3a was upregulated in pancreatic ductal adenocarcinoma as compared with its expression in normal pancreatic tissues. Knockdown of eIF3a by a specific shRNA caused significant decreases in cell proliferation and clonogenic abilities in pancreatic cancer SW1990 and Capan-1 cells. Consistently, the pancreatic cancer cell growth rates were also impaired in xenotransplanted mice. Moreover, wound-healing assay showed that depletion of eIF3a significantly slowed down the wound recovery processes in SW1990 and Capan-1 cells. Transwell migration and invasion assays further showed that cell migration and invasion abilities were significantly inhibited by knockdown of eIF3a in SW1990 and Capan-1 cells. Statistical analysis of eIF3a expression in 140 cases of pancreatic ductal adenocarcinoma samples revealed that eIF3a expression was significantly associated with tumor metastasis and TNM staging. These analyses suggest that eIF3a contributes to cell proliferation and motility in pancreatic ductal adenocarcinoma.

eIF3a improve cisplatin sensitivity in ovarian cancer by regulating XPC and p27Kip1 translation

The eukaryotic translation initiation factor 3a (eIF3a) is one of the core subunits of the translation initiation complex eIF3, responsible for ribosomal subunit joining and mRNA recruitment to the ribosome. Our previous study identified that it was correlated with platinum response in lung cancer. The current study aims to test the hypothesis that eIF3a may affect the drug response and prognosis of ovarian cancer patients receiving platinum-based chemotherapy by regulating xeroderma pigmentosum complementation group C (XPC) and p27^Kip1. Immunohistochemistry and western blot was used to determine the expression of eIF3a in 126 human ovarian cancer tissues followed by association analysis of eIF3a expression with patient's response and survival. Ectopic over-expression and RNA interference knockdown of eIF3a were carried out in A2780/cisplatin (DDP) and its parental A2780 cells, respectively, to determine the effect of altered eIF3a expression on cellular response to cisplatin by employing MTT assay. Western Blot analyses were also carried out to determine the regulation of eIF3a on XPC and p27^Kip1. eIF3a expression was associated with response of ovarian cancer patients to DDP-based chemotherapy and their survival. Overexpression and knockdown of eIF3a increased and decreased the cellular response to cisplatin in A2780/DDP and A2780 cells, respectively. In addition, XPC and p27^Kip1 were down regulated by eIF3a. eIF3a improves ovarian cancer patients' response to DDP-based chemotherapy via down regulating XPC and p27^Kip1.

The oncogenic role of EIF3D is associated with increased cell cycle progression and motility in prostate cancer

EIF3 is the largest multi-protein complex, and several studies have revealed the oncogenic roles of its subunits in many human cancers. However, the roles of EIF3D in the development and progression of PCa remain uncovered. In the present study, the expression of EIF3D in prostate cancer and paracarcinoma tissues, as well as PCa cell lines, was examined. In PCa tissues, the expression of EIF3D was up-regulated compared to that in paracarcinoma tissues. In order to investigate whether EIF3D could serve as potential therapeutic target for prostate cancer, EIF3D was knocked down to verify its functional role in prostate cancer cells. After EIF3D knockdown in PC-3 and DU145 cells, cell proliferation, invasion and colony formation were significantly inhibited; meanwhile, cell cycle analysis revealed cell cycle arrest at G2/M phase. EIF3D is associated with PCa, and silencing EIF3D will result in decreased proliferation, and migration, as well as G2/M arrest in DU145 and PC-3 cells. These results suggest that EIF3D plays an oncogenic role in PCa development and progression.

EIF4EBP1 overexpression is associated with poor survival and disease progression in patients with hepatocellular carcinoma

Objective

EIF4EBP1 acts as a crucial effector in mTOR signaling pathway. Studies have suggested that EIF4EBP1 plays a critical role in carcinogenesis. However, the clinical significance and biological role of EIF4EBP1 in hepatocellular carcinoma (HCC) have not been elucidated. Therefore, we aimed to investigate the clinical significance of EIF4EBP1 in HCC.

Methods

Total 128 cases of HCCs were included in this study. EIF4EBP1 expression in HCC tissues was detected by qRT-PCR, Western blot and immunohistochemistry, respectively. Then the relationships between EIF4EBP1 expression and clinical features as well as survival were analyzed.

Results

The expression level of EIF4EBP1 mRNA is significantly higher in 60% (24/40) of fresh HCC tissues than that in the matched adjacent nontumor liver (NCL) tissues (P = 0.044). Similarly, EIF4EBP1 protein is notably upregulated in 8 HCC tissues (randomly selected from the 40 HCCs) measured by Western blot and is significantly increased in another 88 paraffin-embedded HCCs (53%, 47/88) by immunohistochemistry compared with the matched NCLs (P < 0.001). EIF4EBP1 protein expression in HCC tissues is significantly correlated with serum AFP (P = 0.003) and marginally significantly associated with pathological grade (P = 0.085), tumor number (P = 0.084), tumor embolus (P = 0.084) and capsulation (P = 0.073). Patients with higher EIF4EBP1 protein expression have a much worse 5-year overall survival (40.3% vs 73.6%) and 5-year disease-free survival (33.0% vs 49.0%) than those with low expression. Furthermore, Cox regression analysis shows that EIF4EBP1 protein is an independent prognostic factor for overall survival (HR, 2.285; 95% CI, 1.154–4.527; P = 0.018) and disease-free survival (HR, 1.901; 95% CI, 1.067–3.386; P = 0.029) in HCC patients.

Conclusions

Our results demonstrate for the first time that EIF4EBP1 mRNA and protein are markedly up-regulated in HCC tissues, and the protein overexpression is significantly associated with poor survival and progression, which provide a potential new prognostic marker and therapeutic target for HCC patients.

The role of eIF3 and its individual subunits in cancer

Specific individual subunits of eIF3 are elevated or reduced in numerous human tumors, and their ectopic overexpression in immortal cells can result in malignant transformation. The structure and assembly of eIF3 and its role in promoting mRNA and methionyl-tRNAi binding to the ribosome during the initiation phase of protein synthesis are described. Methods employed to detect altered levels of eIF3 subunits in cancers are critically evaluated in order to conclude rigorously that such subunits may cause malignant transformation. Strong evidence is presented that the individual overexpression of eIF3 subunits 3a, 3b, 3c, 3h, 3i and 3m may cause malignant transformation, whereas underexpression of subunits 3e and 3f may cause a similar outcome. Possible mechanisms to explain the malignant phenotypes are examined. The involvement of eIF3 in cancer reinforces the view that translational control plays an important role in the regulation of cell proliferation, and provides new targets for the development of therapeutic agents. This article is part of a Special Issue entitled: Translation and Cancer.

The translation initiation factor eIF3i up-regulates vascular endothelial growth factor A, accelerates cell proliferation, and promotes angiogenesis in embryonic development and tumorigenesis

Vascular endothelial growth factor A (VEGFA) is a critical proangiogenic factor that is activated by hypoxia at both the transcriptional and post-transcriptional levels. In hypoxia conditions, stabilized hypoxia-inducible factor 1α (HIF1A) is the key regulator for transcriptional activation of VEGFA. However, the post-transcriptional control of VEGFA expression remains poorly understood. Here, we report that the eukaryotic translation initiation factor 3i (eIF3i) is required for VEGFA protein expression in both normal embryonic and tumorigenic angiogenesis. eIF3i is dynamically expressed in the early stages of zebrafish embryogenesis and in human hepatocellular carcinoma tissues. eIF3i homozygous mutant zebrafish embryos show severe angiogenesis defects and human hepatocellular cancer cells with depletion of eIF3i to induce less angiogenesis in tumor models. Under hypoxia, the HIF1A protein can interact with its binding sequence in the eIF3i promoter and activate eIF3i transcription. The expression of VEGFA, which should rise in hypoxia, is significantly inhibited by eIF3i siRNA treatment. Moreover, eIF3i knockdown did not cause a general translation repression but specifically reduced the translation efficiency of the VEGFA mRNAs. Taken together, our results suggest that eIF3i is induced by HIF1A under hypoxia and controls normal and tumorigenic angiogenesis through regulating VEGFA protein translation.

eIF3a is over-expressed in urinary bladder cancer and influences its phenotype independent of translation initiation

PURPOSE

The eukaryotic translation initiation factor (eIF) 3a, the largest subunit of the eIF3 complex, is a key functional entity in ribosome establishment and translation initiation. In the past, aberrant eIF3a expression has been linked to the pathology of various cancer types but, so far, its expression has not been investigated in transitional cell carcinomas. Here, we investigated the impact of eIF3 expression on urinary bladder cancer (UBC) cell characteristics and UBC patient survival.

METHODS AND RESULTS

eIF3a expression was reduced through inducible knockdown in the UBC-derived cell lines RT112, T24, 5637 and HT1197. As a consequence of eIF3a down-regulation, UBC cell proliferation, clonogenic potential and motility were found to be decreased and, concordantly, UBC tumour cell growth rates were found to be impaired in xenotransplanted mice. Polysomal profiling revealed that reduced eIF3a levels increased the abundance of 80S ribosomes, rather than impairing translation initiation. Microarray-based gene expression and ontology analyses revealed broad effects of eIF3a knockdown on the transcriptome. Analysis of eIF3a expression in primary formalin-fixed paraffin embedded UBC samples of 198 patients revealed that eIF3a up-regulation corresponds to tumour grade and that high eIF3a expression corresponds to longer overall survival rates of patients with low grade tumours.

CONCLUSIONS

From our results we conclude that eIF3a expression may have a profound effect on the UBC phenotype and, in addition, may serve as a prognostic marker for low grade UBCs.

The prognostic value of altered eIF3a and its association with p27 in non-small cell lung cancers

BACKGROUND

Over-expressed eukaryotic initiation factor 3a (eIF3a) in non-small cell lung cancer (NSCLC) contributed to cisplatin sensitivity. However, the role of eIF3a in oncogenesis was still controversial. This study was designed to investigate the prognostic impact of eIF3a and p27 in radically resected NSCLC patients.

METHODS

The expression levels of subcellular eIF3a and p27 were evaluated immunohistochemically in 537 radically resected NSCLC samples, and another cohort of 210 stage II NSCLC patients. Disease specific survival (DSS) and disease free survival (DFS) were analyzed by Kaplan-Meier method and Cox regression model.

RESULTS

The subcellular expression of eIF3a was strongly correlated with status of p27 (Spearman rank coefficient correlation for cytoplasmic eIF3a and p27=0.653, for nuclear staining=0.716). Moreover, survival analysis revealed favorable prognostic impact of nuclear eIF3a, p27, and the combination high nuclear staining on NSCLC (Hazards Ratio=0.360, 95%CI=0.109-0.782, P=0.028). In addition, interaction research between biomarkers and chemotherapy status disclosed cisplatin-based regimen trend to prolong DSS of stage II NSCLC patients with high eIF3a-C (P=0.036)and low p27-N (P=0.031).

CONCLUSIONS

Our findings suggested altered eIF3a expression closely correlated with p27 status, and the association was of prognostic value for resected NSCLC. Altered expression of eIF3a and p27 predicted prognosis of NSCLC independently.

Microarray gene expression analysis of tumorigenesis and regional lymph node metastasis in laryngeal squamous cell carcinoma

BACKGROUND

Laryngeal squamous cell carcinoma (LSCC) is the most common type in head and neck squamous cell carcinoma (HNSCC), and the development and progression of LSCC are multistep processes accompanied by changes of molecular biology.

OBJECTIVE

The purpose of this study was to investigate the molecular basis of tumorigenesis and regional lymph node metastasis in LSCC, and provide a set of genes that may be useful for the development of novel diagnostic markers and/or more effective therapeutic strategies.

METHODS

A total number of 10 patients who underwent surgery for primary laryngeal squamous cell carcinoma were recruited for microarray analysis. LSCC tissues compared with corresponding adjacent non-neoplastic tissues were analysed by Illumina mRNA microarrays, and LSCC tissues with regional lymph node metastasis and LSCC tissues without regional lymph node metastasis were analyzed in the same manner. The most frequently differently expressed genes screened by microarrays were also validated by qRT-PCR in another 42 patients diagnosed for LSCC.

RESULTS

Analysed by Illumina mRNA microarrays, there were 361 genes significantly related to tumorigenesis while 246 genes significantly related to regional lymph node metastasis in LSCC. We found that the six genes (CDK1, CDK2, CDK4, MCM2, MCM3, MCM4) were most frequently differently expressed functional genes related to tumorigenesis while eIF3a and RPN2 were most frequently differently expressed functional genes related to regional lymph node metastasis in LSCC. The expressions of these genes were also validated by qRT-PCR.

CONCLUSIONS

The research revealed a gene expression signature of tumorigenesis and regional lymph node metastasis in laryngeal squamous cell carcinoma. Of the total, the deregulation of several genes (CDK1, CDK2, CDK4, MCM2, MCM3, MCM4, EIF3a and RPN2) were potentially associated with disease development and progression. The result will contribute to the understanding of the molecular basis of LSCC and help to improve diagnosis and treatment.

Synthesis, pharmacophores, and mechanism study of pyridin-2(1H)-one derivatives as regulators of translation initiation factor 3A

Twenty-seven 1,5-disubstituted-pyridin-2(1H)-one derivatives were synthesized and evaluated for their anti-cancer and anti-fibrosis activity by A549 and NIH3T3 cell viability assays, respectively. To study the selectivity between the cancer and fibrosis cell lines, pharmacophore models (F1-F4) were built in advance for compounds with pyridin-2(1H)-one scaffold, which revealed the relationship between the occupation of the aromatic sub-site F4 and potent anti-cancer activity. The relationship between structure and anti-cancer activity for all target compounds is also reported herein: 1-Phenyl-5-((m-tolylamino)methyl)pyridine-2(1H)-one (22) displayed both potency and selectivity (IC50=0.13 mM) toward the A549 cell line through the inhibition of translation initiation, especially by eIF3a suppression, and can be treated as a lead for the design of novel eIF3a regulators and anti-lung cancer agents.

N-myc downstream regulated 1 (NDRG1) is regulated by eukaryotic initiation factor 3a (eIF3a) during cellular stress caused by iron depletion

Iron is critical for cellular proliferation and its depletion leads to a suppression of both DNA synthesis and global translation. These observations suggest that iron depletion may trigger a cellular “stress response”. A canonical response of cells to stress is the formation of stress granules, which are dynamic cytoplasmic aggregates containing stalled pre-initiation complexes that function as mRNA triage centers. By differentially prioritizing mRNA translation, stress granules allow for the continued and selective translation of stress response proteins. Although the multi-subunit eukaryotic initiation factor 3 (eIF3) is required for translation initiation, its largest subunit, eIF3a, may not be essential for this activity. Instead, eIF3a is a vital constituent of stress granules and appears to act, in part, by differentially regulating specific mRNAs during iron depletion. Considering this, we investigated eIF3a’s role in modulating iron-regulated genes/proteins that are critically involved in proliferation and metastasis. In this study, eIF3a was down-regulated and recruited into stress granules by iron depletion as well as by the classical stress-inducers, hypoxia and tunicamycin. Iron depletion also increased expression of the metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), and a known downstream repressed target of eIF3a, namely the cyclin-dependent kinase inhibitor, p27^kip1. To determine if eIF3a regulates NDRG1 expression, eIF3a was inducibly over-expressed or ablated. Importantly, eIF3a positively regulated NDRG1 expression and negatively regulated p27^kip1 expression during iron depletion. This activity of eIF3a could be due to its recruitment to stress granules and/or its ability to differentially regulate mRNA translation during cellular stress. Additionally, eIF3a positively regulated proliferation, but negatively regulated cell motility and invasion, which may be due to the eIF3a-dependent changes in expression of NDRG1 and p27^kip1 observed under these conditions.

Translational regulation of RPA2 via internal ribosomal entry site and by eIF3a

RPA2 is a subunit of a trimeric replication protein A (RPA) complex important for DNA repair and replication. Although it is known that RPA activity is regulated by post-translational modification, whether RPA expression is regulated and the mechanism therein is currently unknown. eIF3a, the largest subunit of eIF3, is an important player in translational control and has been suggested to regulate translation of a subset of messenger RNAs important for tumorigenesis, metastasis, cell cycle progression, drug response and DNA repair. In the present study, we show that RPA2 expression is regulated at translational level via internal ribosome entry site (IRES)-mediated initiation in response to DNA damage. We also found that eIF3a suppresses RPA2 synthesis and inhibits its cellular IRES activity by directly binding to the IRES element of RPA2 located at -50 to -150 bases upstream of the translation start site. Taken together, we conclude that RPA2 expression is translationally regulated via IRES and by eIF3a and that this regulation is partly accountable for cellular response to DNA damage and survival.

A systematic analysis of miRNA transcriptome in Marek's disease virus-induced lymphoma reveals novel and differentially expressed miRNAs

Marek's disease is a lymphoproliferative neoplastic disease of the chicken, which poses a serious threat to poultry health. Marek's disease virus (MDV)-induced T-cell lymphoma is also an excellent biomedical model for neoplasia research. Recently, miRNAs have been demonstrated to play crucial roles in mediating neoplastic transformation. To investigate host miRNA expression profiles in the tumor transformation phase of MDV infection, we performed deep sequencing in two MDV-infected samples (tumorous spleen and MD lymphoma from liver), and two non-infected controls (non-infected spleen and lymphocytes). In total, 187 and 16 known miRNAs were identified in chicken and MDV, respectively, and 17 novel chicken miRNAs were further confirmed by qPCR. We identified 28 down-regulated miRNAs and 11 up-regulated miRNAs in MDV-infected samples by bioinformatic analysis. Of nine further tested by qPCR, seven were verified. The gga-miR-181a, gga-miR-26a, gga-miR-221, gga-miR-222, gga-miR-199*, and gga-miR-140* were down-regulated, and gga-miR-146c was up-regulated in MDV-infected tumorous spleens and MD lymphomas. In addition, 189 putative target genes for seven differentially expressed miRNAs were predicted. The luciferase reporter gene assay showed interactions of gga-miR-181a with MYBL1, gga-miR-181a with IGF2BP3, and gga-miR-26a with EIF3A. Differential expression of miRNAs and the predicted targets strongly suggest that they contribute to MDV-induced lymphomagenesis.

The A/G allele of eIF3a rs3740556 predicts platinum-based chemotherapy resistance in lung cancer patients

eIF3a is the largest subunit of eukaryotic translation initiation factor 3, which has been suggested to affect tumor progression and activity of nucleotide excision repair pathway contributing to platinum resistance. The purpose of this study was to investigate possible mutations in promoter and exon regions of eIF3a gene and to assess whether eIF3a mutation status have prognostic and predictive significance in platinum-based chemotherapeutic lung cancer patients. 771 lung cancer patients were enrolled and followed up. These patients were newly diagnosed with incident lung cancer, which was confirmed histologically or cytologically, and accepted platinum-based chemotherapy for at least two cycles. Three novel mutations of eIF3a were found, including 11279G>A in intron 6, Arg438Lys in exon 9, 29671G>A in intron 15, with minor allele frequency of 0.16, 0.18, 0.16, respectively. A-carrier patients of rs3740556 conferred a significantly better platinum-based chemotherapy response (p < 0.05) and seemed to live longer. eIF3a genetic polymorphisms can be considered as predictive tools for pretreatment evaluation of platinum-based chemotherapy. Lung cancer patients carrying rs3740556 A allele tended to have a favorable prognosis after treatment with platinum-based chemotherapy.

Overexpression of eIF3a in Squamous Cell Carcinoma of the Oral Cavity and Its Putative Relation to Chemotherapy Response

The eukaryotic translation initiation factor eIF3a is one of the core subunits of the translation initiation complex eIF3, responsible for ribosomal subunit joining and mRNA recruitment to the ribosome. It is known to play an important role in general translation initiation as well as in the specific translational regulation of various gene products, among which many influence tumour development, progression, and the therapeutically important pathways of DNA damage repair. Therefore, beyond its role in protein synthesis, eIF3a is emerging as regulator in tumour pathogenesis and therapy response and, therefore, a potential tumor marker. By means of a tissue microarray (TMA) for histopathological and statistical assessment, we here show eIF3a expression in 103 cases of squamous cell carcinoma of the oral cavity (OSCC), representing tissues from 103 independent patients. A subset of the study cohort was treated with platinum based therapy. Our results show that the 170 kDa protein is upregulated in OSCC and correlates with good overall survival. Overexpressing tumors respond better to platinum-based chemotherapy, suggesting eIF3a as a putative predictive as well as prognostic tumor marker in OSCC.

Translational control gone awry: a new mechanism of tumorigenesis and novel targets of cancer treatments

Translational control is one of primary regulation mechanisms of gene expression. Eukaryotic translational control mainly occurs at the initiation step, the speed-limiting step, which involves more than ten translation initiation factors [eIFs (eukaryotic initiation factors)]. Changing the level or function of these eIFs results in abnormal translation of specific mRNAs and consequently abnormal growth of cells that leads to human diseases, including cancer. Accumulating evidence from recent studies showed that the expression of many eIFs was associated with malignant transformation, cancer prognosis, as well as gene expression regulation. In the present paper, we perform a critical review of recent advances in understanding the role and mechanism of eIF action in translational control and cancer as well as the possibility of targeting eIFs for therapeutic development.

Role of eIF3a in regulating cisplatin sensitivity and in translational control of nucleotide excision repair of nasopharyngeal carcinoma

Translational control at the initiation step has been recognized as a major and important regulatory mechanism of gene expression. eIF3a, a putative subunit of eIF3 complex, has recently been shown to play an important role in regulating translation of a subset of mRNAs and found to correlate with prognosis of cancers. In this study, using nasopharyngeal carcinoma (NPC) cells as a model system we tested the hypothesis that eIF3a negatively regulates synthesis of nucleotide excision repair (NER) proteins and, thus, NER activities and cellular response to treatments with DNA damaging agents such as cisplatin. We found that a cisplatin-sensitive subclone S16 isolated from a NPC cell line CNE2 via limited dilution has increased eIF3a expression. Knocking down its expression in S16 cells increased cellular resistance to cisplatin, NER activity, and synthesis of NER proteins XPA, XPC, RAD23B, and RPA32. Altering eIF3a expression also changed cellular response to cisplatin and UV treatment in other NPC cell lines. Taken together, we conclude that eIF3a plays an important role in cisplatin response and NER activity of nasopharyngeal carcinomas by suppressing synthesis of NER proteins.

Effect of eIF3a on response of lung cancer patients to platinum-based chemotherapy by regulating DNA repair

PURPOSE

The purpose of this study is to test the hypothesis that eIF3a may regulate the expression of DNA repair proteins which, in turn, affects response of lung cancer patients to treatments by DNA-damaging anticancer drugs.

EXPERIMENTAL DESIGN

Immunohistochemistry was used to determine the expression of eIF3a in 211 human lung cancer tissues followed by association analysis of eIF3a expression with patient's response to platinum-based chemotherapy. Ectopic overexpression and RNA interference knockdown of eIF3a were carried out in NIH3T3 and H1299 cell lines, respectively, to determine the effect of altered eIF3a expression on cellular response to cisplatin, doxorubicine, etoposide (VP-16), vincristine, and vinblastine by using MTT assay. The DNA repair capacity of these cells was evaluated by using host-cell reactivation assay. Real-time reverse transcriptase PCR and Western Blot analyses were carried out to determine the effect of eIF3a on the DNA repair genes by using cells with altered eIF3a expression.

RESULTS

eIF3a expression associates with response of lung cancer patients to platinum-based chemotherapy. eIF3a knockdown or overexpression, respectively, increased and decreased the cellular resistance to cisplatin and anthrocycline anticancer drugs, DNA repair activity, and expression of DNA repair proteins.

CONCLUSIONS

eIF3a plays an important role in regulating the expression of DNA repair proteins which, in turn, contributes to cellular response to DNA-damaging anticancer drugs and patients' response to platinum-based chemotherapy.

The translational regulator eIF3a: the tricky eIF3 subunit!

Regulation of gene expression is a fundamental step in cellular physiology as abnormalities in this process may lead to de-regulated growth and cancer. Translation of mRNA is mainly regulated at the rate-limiting initiation step, where many eukaryotic initiation factors (eIFs) are involved. The largest and most complex initiation factor is eIF3 which plays a role in translational regulation, cell growth and cancer. The largest subunit of eIF3 is eIF3a, although it is not required for the general function of eIF3 in translation initiation. However, eIF3a may play a role as a regulator of a subset of mRNAs and has been demonstrated to regulate the expression of p27(kip1), tyrosinated α-tubulin and ribonucleotide reductase M2 subunit. These molecules have a pivotal role in the regulation of the cell cycle. Moreover, the eIF3a mRNA is ubiquitously expressed in all tissues at different levels and is found elevated in a number of cancer types. eIF3a can modulate the cell cycle and may be a translational regulator for proteins important for entrance into S phase. The expression of eIF3a is decreased in differentiated cells in culture and the suppression of eIF3a expression can reverse the malignant phenotype and change the sensitivity of cells to cell cycle modulators. However, the role of eIF3a in cancer is still unclear. In fact, some studies have identified eIF3a to be involved in cancer development, while other results indicate that it could provide protection against evolution into higher malignancy. Together, these findings highlight the "tricky" and interesting nature of eIF3a.

Translational control in cancer

Remarkable progress has been made in defining a new understanding of the role of mRNA translation and protein synthesis in human cancer. Translational control is a crucial component of cancer development and progression, directing both global control of protein synthesis and selective translation of specific mRNAs that promote tumour cell survival, angiogenesis, transformation, invasion and metastasis. Translational control of cancer is multifaceted, involving alterations in translation factor levels and activities unique to different types of cancers, disease stages and the tumour microenvironment. Several clinical efforts are underway to target specific components of the translation apparatus or unique mRNA translation elements for cancer therapeutics.

The regulation of protein synthesis in cancer

Translational control of cancer is a multifaceted process, involving alterations in translation factor levels and activities that are unique to the different types of cancers and the different stages of disease. Translational alterations in cancer include adaptations of the tumor itself, of the tumor microenvironment, an integral component in disease, and adaptations that occur as cancer progresses from development to local disease and ultimately to metastatic disease. Adaptations include the overexpression and increased activity of specific translation factors, the physical or functional loss of translation regulatory components, increased production of ribosomes, selective mRNA translation, and alteration of signal transduction pathways to permit unfettered activation of protein synthesis. There is intense clinical interest to capitalize on the emerging new understanding of translational control in cancer by targeting specific components of the translation apparatus that are altered in disease for the development of specific cancer therapeutics. Clinical trial data are nascent but encouraging, suggesting that translational control constitutes an important new area for drug development in human cancer.

RNA aptamers to translational components

Potential applications for functional RNAs are rapidly expanding, not only to address functions based on primary nucleotide sequences, but also by RNA aptamers, which can suppress the activity of any target molecule. Aptamers are short DNA or RNA folded molecules that can be selected in vitro on the basis of their high affinity for a target molecule. Here, we summarize RNA aptamers selected against human translation initiation factors, and their superior potentials to recognize and inhibit their target proteins. Importantly, the high affinity of RNA aptamers to proteins without RNA recognition motifs or intrinsic, strong affinity to RNA is achieved through the capture of the protein's global conformation. In other words, RNA has a high potential to form a vast set of tertiary structures, which we would like to refer to as 'RNA plasticity'. This provides us with a solid and promising basis to take steps to create novel RNA molecules of therapeutic potential with distinct structures, which should be equivalent or superior to antibodies.

Anti- and pro-tumor functions of autophagy

Autophagy constitutes one of the major responses to stress in eukaryotic cells, and is regulated by a complex network of signaling cascades. Not surprisingly, autophagy is implicated in multiple pathological processes, including infection by pathogens, inflammatory bowel disease, neurodegeneration and cancer. Both oncogenesis and tumor survival are influenced by perturbations of the molecular machinery that controls autophagy. Numerous oncoproteins, including phosphatidylinositol 3-kinase, Akt1 and anti-apoptotic members of the Bcl-2 family suppress autophagy. Conversely, several tumor suppressor proteins (e.g., Atg4c; beclin 1; Bif-1; BH3-only proteins; death-associated protein kinase 1; LKB1/STK11; PTEN; UVRAG) promote the autophagic pathway. This does not entirely apply to p53, one of the most important tumor suppressor proteins, which regulates autophagy in an ambiguous fashion, depending on its subcellular localization. Irrespective of the controversial role of p53, basal levels of autophagy appear to inhibit tumor development. On the contrary, chemotherapy- and metabolic stress-induced activation of the autophagic pathway reportedly contribute to the survival of formed tumors, thereby favoring resistance. In this context, autophagy inhibition would represent a major therapeutic target for chemosensitization. Here, we will review the current knowledge on the dual role of autophagy as an anti- and pro-tumor mechanism.

The let-7 microRNA interfaces extensively with the translation machinery to regulate cell differentiation

MicroRNAs (miRNAs) are noncoding RNAs that regulate numerous target genes through a posttranscriptional mechanism and thus control major developmental pathways. The phylogenetically conserved let-7 miRNA regulates cell proliferation and differentiation, thus functioning as a key regulator of developmental timing in C. elegans and a tumor suppressor gene in humans. Using a reverse genetic screen, we have identified genetic interaction partners of C. elegans let-7, including known and novel potential target genes. Initial identification of several translation initiation factors as suppressors of a let-7 mutation led us to systematically examine genetic interaction between let-7 and the translational machinery, which we found to be widespread. In the presence of wild-type let-7, depletion of the translation initiation factor eIF3 resulted in precocious cell differentiation, suggesting that developmental timing is translationally regulated, possibly by let-7. As overexpression of eIF3 in humans promotes translation of mRNAs that are also targets of let-7-mediated repression, we suggest that eIF3 may directly or indirectly oppose let-7 activity. This might provide an explanation for the opposite functions of let-7 and eIF3 in regulating tumorigenesis.

Role of eIF3a (eIF3 p170) in intestinal cell differentiation and its association with early development

Eukaryotic initiation factor 3a (eIF3a) has been suggested to play a regulatory role in mRNA translation. Decreased eIF3a expression has been observed in differentiated cells while higher levels have been observed in cancer cells. However, whether eIF3a plays any role in differentiation and development is currently unknown. Here, we investigated eIF3a expression during mouse development and its role in differentiation of colon epithelial cells. We found that eIF3a expression was higher in fetal tissues compared with postnatal ones. Its expression in intestine, stomach, and lung abruptly stopped on the 18th day in gestation but persisted in liver, kidney, and heart throughout the postnatal stage at decreased levels. Similarly, eIF3a expression in colon cancer cell lines, HT-29 and Caco-2, drastically decreased prior to differentiation. Enforced eIF3a expression inhibited while knocking it down using small interference RNA promoted Caco-2 differentiation. Thus, eIF3a may play some roles in development and differentiation and that the decreased eIF3a expression may be a pre-requisite of intestinal epithelial cell differentiation.

Individual overexpression of five subunits of human translation initiation factor eIF3 promotes malignant transformation of immortal fibroblast cells

Transcriptional and post-transcriptional regulatory mechanisms are commonly accepted paradigms of tumorigenesis. The view is emerging that deregulation of translation contributes importantly to cancer development, a role not generally appreciated before. Eukaryotic initiation factor eIF3 contains at least thirteen non-identical subunits, named from eIF3a to eIF3m, and plays an essential role in the rate-limiting initiation phase of translation. Increased mRNA and protein levels of the eIF3a, -3b, -3c, -3h, and -3i subunits have been detected in a wide variety of human tumors and are frequently identified as prognostic biomarkers for poor clinical outcome. However, it remains to be established whether up-regulation of eIF3 subunits is a consequence or a cause of the malignant phenotypes. Here we report that ectopic expression of eIF3a, -3b, -3c, -3h, or -3i in stably transfected NIH3T3 cells leads to a number of oncogenic properties: decreased doubling times, increased clonogenicity and viability, facilitated S-phase entry, attenuation of apoptosis, formation of transformed foci, and anchorage-independent growth. Only overexpression of the transforming subunits results in a stimulation of initiation and global protein synthesis rates and enhanced translation of poorly translated mRNAs that encode growth-regulating proteins, including cyclinD1, c-Myc, fibroblast growth factor-2, and ornithine decarboxylase, which may be responsible for oncogenic malignancy in the transformed cell lines. Based on these results, we hypothesize that eIF3 contributes to hyperactivation of the translation initiation machinery and thereby may play an important role in neoplasia. Cancer cells appear to require an aberrantly activated translational state to survive, suggesting that the initiation factors may be promising therapeutic targets for treating cancer.

Initiation factor eIF3 and regulation of mRNA translation, cell growth, and cancer

One important regulation of gene expression in eukaryotes occurs at the level of mRNA translation, specifically at the step of translational initiation. Deregulation at this step will cause abnormal gene expression, leading to altered cell growth and possibly cancer. Translational initiation is controlled by multiple eIFs and one of these, eIF3, is the most complex and important factor for regulation of translation. Various subunits of eIF3 have recently been implicated to play important roles in regulating translation of specific mRNAs encoding proteins important for cell growth control. The expression of these eIF3 subunits has also been found altered in various human tumors and their altered expression may cause cancer and/or affect prognosis. Although the importance of translational regulation in cell growth control and oncogenesis is being slowly recognized, more vigorous studies on the role of eIFs in oncogenesis and cancer will likely benefit diagnosis, prognosis, and treatment of human cancers.

p150 overexpression in gastric carcinoma: the association with p53, apoptosis and cell proliferation

To clarify the significance of p150 expression, 102 gastric carcinomas were immunohistochemically investigated and 14 fresh samples of the cancer were analyzed with the immunoblot method. Tumor cell apoptosis was assessed by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling (TUNEL). Both Ki-67 antigen and p53 expression were analyzed immunohistochemically. Eighty-six out of 102 (85%) gastric cancers stained positively for p150. All 14 tumors analyzed by Western blotting overexpressed p150. Statistical analysis revealed a close association between p150 overexpression and the clinicopathologic parameters of gastric cancer. All well-differentiated cancers showed high p150 expression (p < 0.005). Furthermore, high p150 expression was more frequently seen in tumors at early invasive stages (p < 0.005), in tumors without metastases (both local and distant, p < 0.005) and in early TNM stages (p < 0.005) in general. As we have found for cervix and esophagus carcinoma, when tumors progress to high malignancy and metastasis, p150 begins to regress and then breaks down. A good correlation of p150 expression, but not p53 expression, with tumor cell apoptosis could be demonstrated (p < 0.01). The Ki-67 labeling index, i.e., the index for a proliferative marker, showed no correlation with either p150 or p53 expression. The results suggest that p150 may be a new early tumor marker for gastric carcinoma similar to that for esophagus and cervix carcinoma.

Role of eIF3 p170 in controlling synthesis of ribonucleotide reductase M2 and cell growth

Translation initiation in eukaryotes is a rate-limiting step in protein synthesis. It is a complicated process that involves many eukaryotic initiation factors (eIFs). Altering the expression level or the function of eIFs may influence the synthesis of some proteins and consequently cause abnormal cell growth and malignant transformation. P170, the largest putative subunit of eIF3, has been found elevated in human breast, cervical, esophageal, and lung cancers, suggesting that p170 may have a potential role in malignant transformation and/or cell growth control. Our recent studies suggested that p170 is likely a translational regulator and it may mediate the effect of mimosine on the translation of a subset mRNAs. Mimosine, a plant nonprotein amino acid, inhibits mammalian DNA synthesis, an essential event of cell growth. The rate-limiting step in DNA synthesis is the conversion of the ribonucleotides to their corresponding deoxyribonucleotides catalysed by ribonucleotide reductase of which the activity is regulated by the level of its M2 subunit. It has been reported that inhibiting the activity of M2 also inhibits cell growth. To understand the relationship between protein and DNA synthesis and between p170 and cell growth control, we investigated in this study whether p170 regulates the synthesis of M2 and, thus, cell growth. We found that altering the expression level of p170 changes the synthesis rate of both M2 and DNA. Decreasing p170 expression in human lung cancer cell line H1299 and breast cancer cell line MCF7 significantly reversed their malignant growth phenotype. However, the overall [35S]methionine incorporation following dramatic decrease in p170 expression was only approximately 25% less than the control cells. These observations, together with our previous findings, suggest that p170 may regulate the translation of a subset mRNAs and its elevated expression level may be important for cancer cell growth and for maintaining their malignant phenotype.

Chromosomal aberrations in esophageal squamous cell carcinoma among Chinese: gain of 12p predicts poor prognosis after surgery

Sixty primary esophageal squamous cell carcinomas (ESCCs) were evaluated for cytogenetic changes by comparative genomic hybridization (CGH). Recurrent chromosomal aberrations were correlated with stage and clinical outcome after esophagectomy to identify cytogenetic changes that are of prognostic significance. Chromosomal aberrations were found in 52 (86.7%) cases. The most frequently detected chromosomal gains involved 3q (67.3%), 8q (57.7%), 5p (51.9%), 7q (28.8%), 15q (28.8%), 20p (21.2%), 20q (28.8%), 1q (26.9%), 7p (26.9%), 2p (23.1%), and 12p (23.1%). Chromosome 12p was most frequently involved in high-level amplification. Six of the 12 cases with gain in 12p showed high-level amplification and the minimum overlapping region localized to 12pter-p13. The most frequently detected chromosomal loss involved 3p (46.2%), 4q (26.9%), 4p (23.1%), 3q (19.2%), 9p (17.3%), 19p (17.3%), and whole 13 (15.4%). No significant correlation was found between the recurrent chromosomal aberrations and pathological stage of ESCC. Univariate analysis demonstrated that late pathological stage (III and IV), gain in 12p, and loss in 3p are associated with poor relapse-free survival. Multivariate analysis confirmed gain in 12p as independent prognosticator for relapse-free survival after esophagectomy besides pathological stage. We conclude that chromosomal aberrations are common in ESCC. Gain in 12p is indicative of poor prognosis after esophagectomy, and combined modality therapy would be indicated in these patients.

Up-regulation of Wnt-1 and ?-catenin production in patients with advanced metastatic prostate carcinoma

BACKGROUND

Wnt-1 and beta-catenin expression levels play an important role in several malignancies. The authors determined the level of production of Wnt-1 and beta-catenin in normal and malignant human prostate carcinoma cell lines. Surgical pathology specimens from primary prostatic adenocarcinoma, lymph node metastases, and skeletal metastases were used to establish a correlation between the level of Wnt-1/beta-catenin expression, Gleason score, serum prostate-specific antigen (PSA) status, and androgen receptor (AR) status.

METHODS

Immunohistochemical analysis was used to investigate the expression of Wnt-1 and beta-catenin in human prostate carcinoma cell lines and in paraffin embedded sections of archival samples from 67 patients with prostate carcinoma. Comparison was made with the expression of tumoral AR and lymph node and skeletal metastases. These results were used to establish a correlation with the clinicopathologic status of patients with prostate carcinoma.

RESULTS

Levels of both Wnt-1 and beta-catenin were low in normal prostate cells and were expressed highly in human prostate carcinoma cell lines. Wnt-1 and cytoplasmic/nuclear beta-catenin expression was observed in 52% and 34%, respectively, of primary prostate carcinoma specimens. High levels of expression of Wnt-1 and beta-catenin were seen in 77% of lymph node metastases and in 85% of skeletal metastases. These increased levels of expression were related directly to the Gleason score and to serum PSA levels in these patients. Maximum levels of Wnt-1 and beta-catenin production were observed in skeletal metastases, whereas normal prostatic tissue failed to exhibit any detectable nuclear staining for beta-catenin.

CONCLUSIONS

High levels of Wnt-1 and beta-catenin expression were associated with advanced, metastatic, hormone-refractory prostate carcinoma, in which they can serve as markers of disease progression.

EIF3 p170, a mediator of mimosine effect on protein synthesis and cell cycle progression

l-Mimosine, a plant amino acid, can reversibly block mammalian cells at late G1 phase and has been suggested to affect translation of mRNAs such as p27, the CDK inhibitor. However, the mechanism of this effect is not known. Regulation of translation generally occurs at the initiation step that, in mammalian cells, is a complex process that requires multiple eukaryotic initiation factors (eIFs) and ribosome. The effects of mimosine on initiation factors or regulators consequently will influence translation initiation. P170, a putative subunit of eIF3, has been suggested to be nonessential for eIF3 function to form preinitiation complexes and it may function as a regulator for translation of a subset of mRNAs. In this article, we tested this hypothesis and investigated whether eIF3 p170 mediates mimosine effect on mRNA translation. We found that p170 translation was dramatically reduced by mimosine due to its iron-chelating function. The decreased expression of p170 by mimosine caused diminished de novo synthesis of tyrosinated alpha-tubulin and elevated translation of p27 before cell cycle arrest. These observations suggest that p170 is likely an early response gene to mimosine treatment and a mediator for mimosine effect on mRNA translation. The effect of p170 on the synthesis of tyrosinated alpha-tubulin and p27 in a reciprocal manner also suggests that p170 functions as a regulator for mRNA translation.

Two subcellular localizations of eIF3 p170 and its interaction with membrane-bound microfilaments: implications for alternative functions of p170

We previously identified a 170-kDa protein (p170) highly expressed in lung cancers as the major subunit of the eukaryotic translation initiation factor 3 (eIF3). p170 was recently cloned and little is known concerning its characteristics and subcellular localization. In this paper, we report our surprising findings that about 20% of p170 is associated with membranes while the remaining portion is located in the cytoplasm presumably in the eIF3 complex. We also find that p170 interacts with both endoplasmic reticulum and plasma membranes. The binding of p170 to membranes is through actin filaments, consistent with the fact that p170 contains a spectrin repeat motif that may be involved in actin binding. Furthermore, the cytoplasmic p170 is phosphorylated at serine and threonine residues and the phosphorylation is stimulated by serum. However, the membrane-actin-bound p170 is not phosphorylated. The results obtained in this study suggest that p170 may have other functions in addition to participating in translation initiation. Phosphorylation may play an important regulatory role in the function of p170 in translation initiation and other alternative functions.