eIF-4E expression is associated with histopathologic grades in cervical neoplasia

eIF4E orchestrates mRNA processing, RNA export and translation to modify specific protein production

The eukaryotic translation initiation factor eIF4E acts as a multifunctional factor that simultaneously influences mRNA processing, export, and translation in many organisms. Its multifactorial effects are derived from its capacity to bind to the methyl-7-guanosine cap on the 5'end of mRNAs and thus can act as a cap chaperone for transcripts in the nucleus and cytoplasm. In this review, we describe the multifactorial roles of eIF4E in major mRNA-processing events including capping, splicing, cleavage and polyadenylation, nuclear export and translation. We discuss the evidence that eIF4E acts at two levels to generate widescale changes to processing, export and ultimately the protein produced. First, eIF4E alters the production of components of the mRNA processing machinery, supporting a widescale reprogramming of multiple mRNA processing events. In this way, eIF4E can modulate mRNA processing without physically interacting with target transcripts. Second, eIF4E also physically interacts with both capped mRNAs and components of the RNA processing or translation machineries. Further, specific mRNAs are sensitive to eIF4E only in particular mRNA processing events. This selectivity is governed by the presence of cis-acting elements within mRNAs known as USER codes that recruit relevant co-factors engaging the appropriate machinery. In all, we describe the molecular bases for eIF4E's multifactorial function and relevant regulatory pathways, discuss the basis for selectivity, present a compendium of ~80 eIF4E-interacting factors which play roles in these activities and provide an overview of the relevance of its functions to its oncogenic potential. Finally, we summarize early-stage clinical studies targeting eIF4E in cancer.

Enhancement of Chemotherapy Efficacy in Cervical Cancer via MAPK Pathway Inhibition by Osimertinib

Addressing recurrent cervical cancer poses a substantial challenge. Osimertinib, an FDA-approved EGFR inhibitor, has emerged as a promising option. Our study examined its potential to enhance paclitaxel's efficacy against cervical cancer. Osimertinib effectively hindered cancer cell growth and induced apoptosis across multiple cell lines. Combined with paclitaxel, it exhibited synergy in suppressing cervical cancer cells. Importantly, osimertinib's inhibitory effect was EGFR-independent; it targeted Mnk phosphorylation, reducing eIF4E activity. In mice, the combined osimertinib-paclitaxel treatment surpassed individual drugs in inhibiting cancer growth. These preclinical findings suggest osimertinib's repurposing as a means to improve paclitaxel's effectiveness in cervical cancer treatment.

eIF5B regulates the expression of PD-L1 in prostate cancer cells by interacting with Wig1

BACKGROUND

Eukaryotic translation initiation factors (eIFs) are the key factors to synthesize translation initiation complexes during the synthesis of eukaryotic proteins. Besides, eIFs are especially important in regulating the immune function of tumor cells. However, the effect mechanism of eIFs in prostate cancer remains to be studied, which is precisely the purpose of this study.

METHODS

In this study, three groups of prostate cancer cells were investigated. One group had its eIF5B gene knocked down; another group had its Programmed death 1 (PD-L1) overexpressed; the final group had its Wild-type p53-induced gene 1 (Wig1) overexpressed. Genetic alterations of the cancer cells were performed by plasmid transfection. The expression of PD-L1 mRNA was detected by quantitative real-time PCR (qRT-PCR), and the expressions of PD-L1 and eIF5B proteins were observed by western blot assays. Cell Counting Kit-8 (CCK-8), flow cytometry, Transwell and Transwell martrigel were used to investigated cell proliferation, apoptosis, migration and invasion, respectively. The effect of peripheral blood mononuclear cells (PBMCs) on tumor cells was observed, and the interaction between eIF5B and Wig1 was revealed by co-immunoprecipitation (CoIP) assay. Finally, the effects of interference with eIF5B expression on the growth, morphology, and immunity of the tumor, as well as PD-L1 expression in the tumor, were verified by tumor xenograft assays in vivo.

RESULTS

Compared with normal prostate epithelial cells, prostate cancer cells revealed higher expressions of eIF5B and PD-L1 interference with eIF-5B expression can inhibit the proliferation, migration, invasion and PD-L1 expression of prostate cancer cells. Meanwhile, the cancer cell group with interference with eIF5B expression also demonstrated greater, apoptosis and higher vulnerability to PBMCs. CoIP assays showed that Wig1 could bind to eIF5B in prostate cancer cells, and its overexpression can inhibit the proliferation, migration, invasion and PD-L1 expression of cancer cells while promoting apoptosis. Moreover, interference with eIF5B expression can inhibit tumor growth, destroy tumor morphology, and suppress the proliferation of tumor cells.

CONCLUSION

eIF5B can promote the expression of PD-L1 by interacting with Wig1. Besides, interference with eIF5B expression can inhibit the proliferation, migration, invasion and immunosuppressive response of prostate cancer cells. This study proposes a new target, eIF5B, for immunotherapy of prostate cancer.

Role of RONS and eIFs in Cancer Progression

Various research works have piled up conflicting evidence questioning the effect of oxidative stress in cancer. Reactive oxygen and nitrogen species (RONS) are the reactive radicals and nonradical derivatives of oxygen and nitrogen. RONS can act as a double-edged weapon. On the one hand, RONS can promote cancer initiation through activating certain signal transduction pathways that direct proliferation, survival, and stress resistance. On the other hand, they can mitigate cancer progression via their resultant oxidative stress that causes many cancer cells to die, as some recent studies have proposed that high RONS levels can limit the survival of cancer cells during certain phases of cancer development. Similarly, eukaryotic translation initiation factors are key players in the process of cellular transformation and tumorigenesis. Dysregulation of such translation initiation factors in the form of overexpression, downregulation, or phosphorylation is associated with cancer cell's altering capability of survival, metastasis, and angiogenesis. Nonetheless, eIFs can affect tumor age-related features. Data shows that alternating the eukaryotic translation initiation apparatus can impact many downstream cellular signaling pathways that directly affect cancer development. Hence, researchers have been conducting various experiments towards a new trajectory to find novel therapeutic molecular targets to improve the efficacy of anticancer drugs as well as reduce their side effects, with a special focus on oxidative stress and initiation of translation to harness their effect in cancer development. An increasing body of scientific evidence recently links oxidative stress and translation initiation factors to cancer-related signaling pathways. Therefore, in this review, we present and summarize the recent findings in this field linking certain signaling pathways related to tumorigeneses such as MAPK and PI3K, with either RONS or eIFs.

The high-risk HPV E6 proteins modify the activity of the eIF4E protein via the MEK/ERK and AKT/PKB pathways

Previous studies have proposed that the human papillomavirus (HPV) E6 oncoproteins modify the transcriptional activity of eIF4E through mechanisms dependent on p53 degradation. However, the effect of these oncoproteins on pathways regulating the activity of the eIF4E protein remains poorly understood. Hence, we investigated the mechanisms whereby E6 proteins regulate the activity of the eIF4E protein and its effect on target genes. Overexpression of E6 constructs (HPV-6, HPV-16, HPV-18, and HPV52) showed that E6 oncoproteins increased phosphorylation of the eIF4E protein (Serine-209). This result was mainly mediated by phosphorylation of the 4EBP1 protein via the PI3K/AKT pathway. Additionally, the pharmacological inhibition of eIF4E phosphorylation in cervical cancer cell lines substantially reduced the protein levels of CCND1 and ODC1, indicating that E6 of the high-risk genotypes may modify protein synthesis of the eIF4E target genes by increasing the activity of the AKT and ERK pathways.

The Prognostic Significance of Eukaryotic Translation Initiation Factors (eIFs) in Endometrial Cancer

Whilst the role of eukaryotic translation initiation factors (eIFs) has already been investigated in several human cancers, their role in endometrial cancer (EC) is relatively unknown. In the present retrospective study, 279 patients with EC (1180 samples) were included (mean age: 63.0 years, mean follow-up: 6.1 years). Samples were analysed for expression of 7 eIFs subunits (eIF2α, eIF3c, eIF3h, eIF4e, eIF4g, eIF5, eIF6) through immunohistochemistry and western blotting. Fifteen samples of healthy endometrium served as controls. Density and intensity were assessed and mean combined scores (CS) calculated for each patient. Upon immunohistochemistry, median eIF5 CS were significantly higher in EC as compared with non-neoplastic tissue (NNT, p < 0.001), whilst median eIF6 CS were significantly lower in EC (p < 0.001). Moreover, eIF5 (p = 0.002), eIF6 (p = 0.032) and eIF4g CS (p = 0.014) were significantly different when comparing NNT with EC grading types. Median eIF4g CS was higher in type II EC (p = 0.034). Upon western blot analysis, eIF4g (p < 0.001), peIF2α (p < 0.001) and eIF3h (p < 0.05) were significantly overexpressed in EC, while expression of eIF3c was significantly reduced in EC as compared with NNT (p < 0.001). The remaining eIFs were non-significant. Besides tumour stage (p < 0.001) and patient's age (p < 0.001), high eIF4g CS-levels were independently associated with poor prognosis (HR: 1.604, 95%CI: 1.037-2.483, p = 0.034). The other eIFs had no prognostic significance. Notably, the independent prognostic significance of eIF4g was lost when adding tumour type. Considering the difficulties in differentiating EC type I and II, eIF4g may serve as a novel prognostic marker indicating patient outcome.

Clinical Significance of Eukaryotic Initiation Factor 4E (eIF4E) Level among Cases Suffering Basal Cell Carcinoma of Skin

BACKGROUND Eukaryotic initiation factor 4E (eIF4E) has been reported to act as a prognostic biomarker in various cancers, but its actual effect on basal cell cancer (BCC) of the skin is rarely reported. Our research measured eIF4E levels and discussed its consequence in BCC of the skin. MATERIAL AND METHODS Semi-quantitative real-time polymerase chain reaction (RT-PCR) and western blotting analysis were used to detect relative expression level of eIF4E in specimens at both mRNA and protein levels. The relationship of eIF4E level with clinical profiles was analyzed via chi-square test. Additionally, prognostic value of eIF4E was analyzed via Kaplan-Meier and cox regression analysis. RESULTS We found that eIF4E was over-expressed in tumor tissues, in comparison to bordering cancer-free tissue samples. Besides, elevated eIF4E level exhibited a strong relation to metastasis, TNM stage, and differentiation. Kaplan-Meier analysis revealed cases harboring high eIF4E levels faced shortened overall survival compared to cases of low levels (log rank test, P=0.018). Moreover, eIF4E could act as an independent biomarker for the prognosis of BCC of the skin, according to Cox regression analysis. CONCLUSIONS The level of eIF4E was upregulated and significantly correlated with the development of BCC of the skin. Thus, it might be a promising prognostic biomarker and therapy target for BCC of the skin.

Expression of 4E-BP1 and phospho-4E-BP1 correlates with the prognosis of patients with clear cell renal carcinoma

Background

Eukaryotic translation initiation factor 4E (eIF4E) is a key regulator of protein synthesis. Changes in eIF4E activity disproportionally affect the translation of a subset of oncogenic mRNAs in some cancers.

Materials and methods

We have assessed the expression levels of vascular endothelial growth factor C (VEGFC), eIF4E, eIF4E-binding proteins (4E-BPs) and phospho-4E-BP1 in clear cell renal carcinoma (ccRCC; n=101) using immunohistochemistry and analyzed the relevant mRNA levels and survival using online databases.

Results

The protein levels of VEGFC, an eIF4E-regulated gene, were upregulated in ccRCC tissues compared with adjacent normal renal tissues, indicating an enhanced eIF4E activity in ccRCC. The expression of eIF4E had no significant changes in ccRCC tissues. However, 4E-BP1 and phospho-4E-BP1 were found to be overexpressed in ccRCC tissues (P<0.05), and the high mRNA and protein levels of 4E-BP1 and phospho-4E-BP1 correlated with an unfavorable clinical outcome in ccRCC patients. Meanwhile, the mRNA expression of PIK3CD and PIK3CG were enhanced in ccRCC.

Conclusion

From these results, we could infer that the increase in eIF4E activity may be caused by the increased phospho-4E-BP1 level, which was probably due to the activation of phosphoinositide 3-kinase (PI3K) pathway.

Effect of a synthetic inhibitor of urokinase plasminogen activator on the migration and invasion of human cervical cancer cells in vitro

As a notable feature of malignant tumors, invasion and metastasis are important events in the process of tumor progression. Amiloride, a synthetic inhibitor of urokinase plasminogen activator (uPA), is involved in these events. To evaluate the therapeutic value of amiloride in cervical cancer, HeLa cells were used as in vitro cellular models. The migration and invasion abilities of HeLa cells, in addition to the mRNA expression of matriptase, uPA, uPA receptor and 72 kDa type IV collagenase (MMP-2), were detected using scratch assays, Transwell chamber assays and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results of RT-qPCR demonstrated that the mRNA expression of uPA and MMP-2 in HeLa cells was downregulated significantly in a dose-dependent manner when incubated with various concentrations of amiloride for 24 h. The migration distance of HeLa cells was significantly shorter at 6, 12 and 24 h following incubation with amiloride (P<0.01), and there was a positive correlation between cell migratory ability and cellular uPA protein expression level (r=0.955, P<0.01). The number of HeLa cells that penetrated the Matrigel following incubation for 24 h with different concentrations of amiloride decreased significantly compared with the control group, indicating that cell invasiveness was positively correlated with the protein expression level of uPA in the cells (r=0.993, P<0.01). The present study demonstrated that amiloride was able to specifically inhibit the mRNA expression levels of uPA in HeLa cells, and sequentially downregulate the mRNA expression of downstream MMP-2 in the uPA system, thereby suppressing the migratory and invasive ability of HeLa cells. Therefore, amiloride may be a promising therapeutic target for the treatment of cervical cancer.

Phase I study of induction chemotherapy with afatinib, ribavirin, and weekly carboplatin and paclitaxel for stage IVA/IVB human papillomavirus-associated oropharyngeal squamous cell cancer

BACKGROUND

The human papillomavirus (HPV) E6 oncoprotein enhances the oncogenic potential of ErbB proteins in HPV-related malignancies. This phase I study evaluates the addition of afatinib, an ErbB family inhibitor, and ribavirin to paclitaxel and carboplatin induction chemotherapy in HPV-associated, locally advanced oropharyngeal squamous cell carcinoma (SCC).

METHODS

This dose escalation study included 2 doses of oral afatinib: 30 and 40 mg daily. Ribavirin dosing was weight based. Paclitaxel (80 mg/m² ) and carboplatin (area under the curve [AUC] 1.5) were administered on days 1 and 8 of each 21-day cycle. After 3 cycles, patients were removed from protocol to receive definitive treatment.

RESULTS

Among 10 patients, there were no dose-limiting toxicities. Six patients (67%) had unconfirmed objective partial responses. The 2-year progression-free survival rate was 75%.

CONCLUSION

Afatinib, ribavirin, paclitaxel, and carboplatin induction chemotherapy is safe and well tolerated. The phase II recommended dose of afatinib is 40 mg oral daily in this combination regimen.

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.

Eukaryotic translation initiation factor 3 subunit D overexpression is associated with the occurrence and development of ovarian cancer

Ovarian cancer is the most common cause of gynaecological cancer-associated death; thus, promising biomarkers and new therapeutic targets for ovarian cancer must be explored. Here, we report that eukaryotic translation initiation factor 3 subunit D (EIF3D), a member of the EIF3 family, was overexpressed in ovarian cancer clinical tissues. Furthermore, the expression of EIF3D was correlated with the International Federation of Gynecology and Obstetrics stage and pathological differentiation stage. 3-(4,5-dimethylthylthiazol-2-yl)-2 (MTT) and colony formation assays revealed that the lentivirus-mediated knockdown of EIF3D suppresses cell proliferation in the ovarian tumour cell lines CAOV-3 and SKOV-3. Flow cytometry revealed that cells were arrested at the G2/M phase of the cell cycle and that cyclin-dependent kinase 1 was also altered after EIF3D silencing. The results presented here demonstrate that EIF3D may play an important role in the occurrence and development of ovarian cancer.

Decreased expression of EIF4A1 after preoperative brachytherapy predicts better tumor-specific survival in cervical cancer

OBJECTIVE

The aim of this study is to investigate whether EIF4A1, EIF4E, and EIF4G1 can serve as prognostic markers for patients with cervical cancer receiving preoperative brachytherapy.

MATERIALS AND METHODS

Tissue microarrays composed of 35 normal cervix samples, 87 cervical cancers treated without preoperative therapy, and 50 pairs of cervical cancer tissues collected before and after preoperative brachytherapy were constructed and evaluated for the expression of EIF4A1, EIF4E, and EIF4G using immunohistochemistry. Immunohistochemical staining was scored by the staining intensity and the percentages of tumor cells. The χ test was used to analyze the association between the immunohistochemistry results and clinicopathologic variables. The Kaplan-Meier method was applied to analyze the disease-specific survival.

RESULTS

Overexpression of EIF4A1, EIF4E, and EIF4G1 were detected in 83.9%, 84.7%, and 80.3% of cervical cancers, respectively, all of which were significantly related to advanced International Federation of Gynecology and Obstetrics stage, squamous cell histology, lymph node metastasis, and deep stromal invasion (P < 0.05). The altered expression pattern of EIF4A1 and EIF4E after preoperative brachytherapy was significantly correlated with the cervical cancer response to brachytherapy (P = 0.029 and 0.012, respectively). The decreased expression of EIF4A1 predicted better tumor-specific survival (P = 0.02). The alteration of EIF4A1 was an independent predictor for tumor-specific survival (P = 0.047; hazards ratio, 0.272; 95% confidence interval, 0.076-0.982).

CONCLUSIONS

Overexpression of EIF4A1, EIF4E, and EIF4G1 were acquired malignant phenotypic features of cervical cancer. EIF4A1 might function as a novel prognostic indicator and a potential therapeutic target for cervical cancer.

Role of the eIF4E binding protein 4E-BP1 in regulation of the sensitivity of human pancreatic cancer cells to TRAIL and celastrol-induced apoptosis

BACKGROUND INFORMATION

Tumour cells can be induced to undergo apoptosis after treatment with the tumour necrosis factor α-related death-inducing ligand (TRAIL). Although human pancreatic cancer cells show varying degrees of response they can be sensitised to the pro-apoptotic effects of TRAIL in the presence of celastrol, a natural compound extracted from the plant Tripterygium wilfordii Hook F. One important aspect of the cellular response to TRAIL is the control of protein synthesis, a key regulator of which is the eukaryotic initiation factor 4E-binding protein, 4E-BP1.

RESULTS

We examined the effects of celastrol and TRAIL in several pancreatic cancer cell lines. In cells that are normally resistant to TRAIL, synergistic effects of TRAIL plus celastrol on commitment to apoptosis and inhibition of protein synthesis were observed. These were associated with a strong up-regulation and dephosphorylation of 4E-BP1. The enhancement of 4E-BP1 expression, which correlated with a threefold increase in the level of the 4E-BP1 transcript, was blocked by inhibitors of reactive oxygen species and the JNK protein kinase. When the expression of 4E-BP1 was reduced by an inducible micro-RNA, TRAIL-mediated apoptosis was inhibited.

CONCLUSION

These results suggest that 4E-BP1 plays a critical role in the mechanism by which TRAIL and celastrol together cause apoptotic cell death in human pancreatic tumour cells.

Treatment of breast and lung cancer cells with a N-7 benzyl guanosine monophosphate tryptamine phosphoramidate pronucleotide (4Ei-1) results in chemosensitization to gemcitabine and induced eIF4E proteasomal degradation

The development of cancer and fibrotic diseases has been shown to be highly dependent on disregulation of cap-dependent translation. Binding protein eIF4E to N(7)-methylated guanosine capped mRNA has been found to be the rate-limiting step governing translation initiation, and therefore represents an attractive target for drug discovery. Our group has found that 7-benzyl guanosine monophosphate (7Bn-GMP) is a potent antagonist of eIF4E cap binding (K(d) = 0.8 μM). Recent X-ray crystallographic studies have revealed that the cap-dependent pocket undergoes a unique structural change in order to accommodate the benzyl group. Unfortunately, 7Bn-GMP is not cell permeable. Recently, we have prepared a tryptamine phosphoramidate prodrug of 7Bn-GMP, 4Ei-1, and shown that it is a substrate for human histidine triad nucleotide binding protein (hHINT1) and inhibits eIF4E initiated epithelial-mesenchymal transition (EMT) by Zebra fish embryo cells. To assess the intracellular uptake of 4Ei-1 and conversion to 7Bn-GMP by cancer cells, we developed a sensitive assay using LC-ESI-MS/MS for the intracellular quantitation of 4Ei-1 and 7Bn-GMP. When incubated with the breast cancer cell line MDA-231 or lung cancer cell lines H460, H383 and H2009, 4Ei-1 was found to be rapidly internalized and converted to 7Bn-GMP. Since oncogenic mRNAs are predicted to have the highest eIF4E requirement for translation, we carried out chemosensitization studies with 4Ei-1. The prodrug was found to chemosensitize both breast and lung cancer cells to nontoxic levels of gemcitabine. Further mechanistic studies revealed that the expressed levels of eIF4E were substantially reduced in cells treated with 4Ei-1 in a dose-dependent manner. The levels of eI4E could be restored by treatment with the proteasome inhibitor MG-132. Taken together, our results demonstrate that 4Ei-1 is likely to inhibit translation initiation by eIF4E cap binding by both antagonizing eIF4E cap binding and initiating eIF4E proteasomal degradation.

The oncogene eIF4E: using biochemical insights to target cancer

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.

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.

Ribavirin as an anti-cancer therapy: acute myeloid leukemia and beyond?

Ribavirin was discovered nearly 40 years ago as a broad-spectrum antiviral drug. Recent data suggest that ribavirin may also be an effective cancer therapy. In this case, ribavirin targets an oncogene, the eukaryotic translation initiation factor eIF4E, elevated in approximately 30% of cancers including many leukemias and lymphomas. Specifically, ribavirin impedes eIF4E mediated oncogenic transformation by acting as an inhibitor of eIF4E. In a phase II clinical trial, ribavirin treatment led to substantial clinical benefit in patients with poor-prognosis acute myeloid leukemia (AML). Here molecular targeting of eIF4E correlated with clinical response. Ribavirin also targets a key enzyme in the guanosine biosynthetic pathway, inosine monophosphate dehydrogenase (IMPDH), and also modulates immunity. Parallels with known antiviral mechanisms could be informative; however, after 40 years, these are not entirely clear. The antiviral effects of ribavirin appear cell-type specific. This variation likely arises for many reasons, including cell specific variations in ribavirin metabolism as well as virus specific factors. Thus, it seems that the mechanisms for ribavirin action in cancer therapy may also vary in terms of the cancer/tissue under study. Here we review the anticancer activities of ribavirin and discuss the possible utility of incorporating ribavirin into diverse cancer therapeutic regimens.

Prognostic significance and therapeutic potential of eukaryotic translation initiation factor 5A (eIF5A) in hepatocellular carcinoma

Using comparative proteomic and genomic approaches, the authors identified eukaryotic translation initiation factor 5A (eIF5A) as an oncofetal molecule highly abundant in mouse embryonic livers and human hepatocellular carcinoma (HCC) cell lines. To evaluate the oncogenic role and prognostic significance of eIF5A in HCC, we investigate the expression patterns of the two isoforms (eIF5A1 and eIF5A2) in a cohort of 258 HCC cases by cDNA microarray. Both eIF5A isoforms were expressed in the tumors, and clinically correlated eIF5A1 with more numbers of tumor nodules and eIF5A2 with tumor venous infiltration in HCC. In a separate cohort of 50 HCCs, high level of eIF5A2, but not eIF5A1, was associated with elevated levels of deoxyhypusine synthase and deoxyhypusine hydroxylase that catalyze post-translational hypusination of eIF5A protein. Interestingly, N1-guanyl-1,7-diaminoheptane (GC7), which is an inhibitor for the first step of eIF5A hypusination, was shown to significantly impair the cell proliferation and invasion of primary HCC cells (HepG2 and Hep3B). To further demonstrate the tumorigenic role associated with eIF5A, a drastic reduction of cell proliferation was associated with suppression of eIF5A2 by transfecting Hep3B, H2-P and H2-M HCC cells expressing high level of this isoform using small interfering RNA (siRNA) against eIF5A2. For these assays, a milder response was usually observed in normal hepatocyte cell line. Therefore, these findings suggest that eIF5A plays an important role in HCC tumorigenesis and metastasis, and targeting eIF5A hypusination by GC7 inhibitor or eIF5A2 by RNA interference (RNAi) may offer new therapeutic alternatives to HCC patients.

Understanding and Targeting the Eukaryotic Translation Initiation Factor eIF4E in Head and Neck Cancer

The eukaryotic translation initiation factor eIF4E is elevated in about 30% of human malignancies including HNSCC where its levels correlate with poor prognosis. Here, we discuss the biochemical and molecular underpinnings of the oncogenic potential of eIF4E. Studies in human leukemia specimens, and later in a mouse model of prostate cancer, strongly suggest that cells with elevated eIF4E develop an oncogene dependency to it, making them more sensitive to targeting eIF4E than normal cells. We describe several strategies that have been suggested for eIF4E targeting in the clinic: the use of a small molecule antagonist of eIF4E (ribavirin), siRNA or antisense oligonucleotide strategies, suicide gene therapy, and the use of a tissue-targeting 4EBP fusion peptide. The first clinical trial targeting eIF4E indicates that ribavirin effectively targets eIF4E in poor prognosis leukemia patients and more importantly leads to striking clinical responses including complete and partial remissions. Finally, we discuss the relevance of these findings to HNSCC.

Combined analysis of eIF4E and 4E-binding protein expression predicts breast cancer survival and estimates eIF4E activity

Increased eukaryotic translation initiation factor 4E (eIF4E) expression occurs in many cancers, and makes fundamental contributions to carcinogenesis by stimulating the expression of cancer-related genes at post-transcriptional levels. This key role is highlighted by the facts that eIF4E levels can predict prognosis, and that eIF4E is an established therapeutic target. However, eIF4E activity is a complex function of expression levels and phosphorylation statuses of eIF4E and eIF4E-binding proteins (4E-BPs). Our hypothesis was that the combined analyses of these pathway components would allow insights into eIF4E activity and its influence on cancer. We have determined expression levels of eIF4E, 4E-BP1, 4E-BP2 and phosphorylated 4E-BP1 within 424 breast tumours, and have carried out analyses to combine these and relate the product to patient survival, in order to estimate eIF4E activity. We show that this analysis gives greater prognostic insights than that of eIF4E alone. We show that eIF4E and 4E-BP expression are positively associated, and that 4E-BP2 has a stronger influence on cancer behaviour than 4E-BP1. Finally, we examine eIF4E, estimated eIF4E activity, and phosphorylated 4E-BP1 as potential predictive biomarkers for eIF4E-targeted therapies, and show that each determines selection of different patient groups. We conclude that eIF4E's influence on cancer survival is modulated substantially by 4E-BPs, and that combined pathway analyses can estimate functional eIF4E.

Overexpression of eukaryotic initiation factor 4E (eIF4E) and its clinical significance in lung adenocarcinoma

BACKGROUND

Eukaryotic initiation factor 4E (eIF4E), an important regulator of translation, plays important roles in tumor transformation, progression and metastasis. However, the clinical significance of eIF4E expression in lung adenocarcinoma (AdC) remains unclear. The aim of this study was to explore the expression of eIF4E gene in lung adenocarcinoma cell lines and tissues, and to investigate its relationship with clinical characteristics and prognosis of patients with lung adenocarcinoma in combination with p53 status.

METHODS

Semi-quantitative RT-PCR and Western blotting assays were performed to detect the expression of eIF4E mRNA and protein in normal human lung epithelial cell line, immortalized lung epithelial cell line and lung adenocarcinoma cell lines. Additionally, the expression of eIF4E gene was also detected in 32 cases of lung adenocarcinoma tissues, tumor adjacent tissues and tumor surrounding normal tissues by the same methods. Moreover, expression of eIF4E and the status of p53 in specimens from 76 patients with lung adenocarcinoma were examined by immunohistochemical staining. Correlations between eIF4E expression and clinicopathological features, and the effect of eIF4E on prognosis of patients with lung adenocarcinoma were evaluated by statistical analysis.

RESULTS

The levels of eIF4E mRNA and protein expression were higher in lung adenocarcinoma cell lines and in telomerase-immortalized lung epithelial cell line than in the normal lung epithelial cell line. The expression of eIF4E gene showed statistical difference between tumor tissues, tumor adjacent tissues and tumor surrounding normal tissues (P<0.05). Moreover, the higher levels of eIF4E expression were correlated with poorer differentiation (P=0.012), higher pathological stage (P<0.0001) and clinical stage (P=0.002), a higher incidence of hematogenous metastasis (P=0.007) and cancer-related death (P=0.036). The 5-year survival rate of patients with higher eIF4E expression was significantly lower than that of patients with lower eIF4E expression (P=0.0045). Furthermore, in a multivariate analysis by Cox regression model, high eIF4E expression was confirmed to be an independent prognostic factor (HR: 2.258; unfavorable, P=0.0056), while lymph node (HR: 2.033; unfavorable, P=0.0440) and hematogenous metastasis (HR: 3.489; unfavorable, P<0.0001) were also significant prognostic factors.

CONCLUSION

High eIF4E expression was correlated with poorer overall survival in lung adenocarcinoma patients. eIF4E might be a better clinical marker predicting the prognosis for lung adenocarcinoma patients in combination with p53 status.

A prospective trial on initiation factor 4E (eIF4E) overexpression and cancer recurrence in node-negative breast cancer

BACKGROUND

Eukaryotic Initiation Factor 4E (eIF4E) plays a crucial role in translation control. High eIF4E increase in tumor specimens independently predicted recurrence by multivariate analysis. This prospective trial of node-negative only breast cancer patients was initiated to test the hypothesis that high eIF4E increase predicts cancer recurrence and death, independent of nodal status.

METHODS

The trial was powered to detect a 2.4-fold increase in relative risk for cancer recurrence in 240 node-negative patients on the basis of high versus low eIF4E increase in tumor specimens (type I error = .05, statistical power = .08). eIF4E level was quantified by using Western blot test. Treatment and surveillance regimens were standardized. Primary endpoints were cancer recurrence and cancer-related death.

RESULTS

Of the 242 patients accrued, 112 were in the low eIF4E group (<7.5-fold), 82 were in the intermediate eIF4E group (7.5- to 15-fold), and 48 were in the high eIF4E group (>15-fold). Patients in the high eIF4E group had a statistically significant higher rate of cancer recurrence and cancer-related death (P = .0001 and P < or = .0001, log rank test). The relative risk for cancer recurrence was 2.2-fold higher in the high eIF4E group (P = .001, Cox model), and 3.7-fold higher for cancer-related death (P = .0009).

CONCLUSIONS

In node-negative breast cancer, high eIF4E increase predicted a higher rate of cancer recurrence and death. High eIF4E patients had a >2-fold increase in relative risk for cancer recurrence and nearly a 4-fold increase in relative risk for death. This supports our hypothesis that high eIF4E is an independent predictor for breast cancer outcome independent of nodal status.

Activation of p53 stimulates proteasome-dependent truncation of eIF4E-binding protein 1 (4E-BP1)

BACKGROUND INFORMATION

The translational inhibitor protein 4E-BP1 [eIF4E (eukaryotic initiation factor 4E)-binding protein 1] regulates the availability of polypeptide chain initiation factor eIF4E for protein synthesis. Initiation factor eIF4E binds the 5' cap structure present on all cellular mRNAs. Its ability to associate with initiation factors eIF4G and eIF4A, forming the eIF4F complex, brings the mRNA to the 43S complex during the initiation of translation. Binding of eIF4E to eIF4G is inhibited in a competitive manner by 4E-BP1. Phosphorylation of 4E-BP1 decreases the affinity of this protein for eIF4E, thus favouring the binding of eIF4G and enhancing translation. We have previously shown that induction or activation of the tumour suppressor protein p53 rapidly leads to 4E-BP1 dephosphorylation, resulting in sequestration of eIF4E, decreased formation of the eIF4F complex and inhibition of protein synthesis.

RESULTS

We now report that activation of p53 also results in modification of 4E-BP1 to a truncated form. Unlike full-length 4E-BP1, which is reversibly phosphorylated at multiple sites, the truncated protein is almost completely unphosphorylated. Moreover, the latter interacts with eIF4E in preference to full-length 4E-BP1. Inhibitor studies indicate that the p53-induced cleavage of 4E-BP1 is mediated by the proteasome and is blocked by conditions that inhibit the dephosphorylation of full-length 4E-BP1. Measurements of the turnover of 4E-BP1 indicate that the truncated form is much more stable than the full-length protein.

CONCLUSIONS

The results suggest a model in which proteasome activity gives rise to a stable, hypophosphorylated and truncated form of 4E-BP1, which may exert a long-term inhibitory effect on the availability of eIF4E, thus contributing to the inhibition of protein synthesis and the growth-inhibitory and pro-apoptotic effects of p53.

Translational control: a target for cancer therapy

Cap-mediated translation is the default mechanism for the synthesis of proteins in eukaryotic cells. Increasingly, malignant cells have been found to have deregulation of this process. Return of normal translational control is associated with loss of tumorigenic potential in pre-clinical models. Currently, a variety of novel therapeutics are in development targeting this mechanism as a treatment for cancer.