Knockdown of EIF3H inhibits the development and progression of pancreatic cancer by regulating cell proliferation and apoptosis in vitro

Nowadays, pancreatic cancer has been recognized as one of the most fatal malignancies worldwide, the molecular mechanism of which is still not fully understood. In this study, we aimed to uncover the fundamental functions of the eukaryotic translation initiation factor 3H subunit (EIF3H) in the development and progression of pancreatic cancer. Firstly, the results of immunohistochemical (IHC) staining revealed that EIF3H was highly expressed in pancreatic cancer. Moreover, lentiviruses were used to deliver shRNAs into pancreatic cancer cells for silencing EIF3H. Furthermore, the loss-of-function assays demonstrated that knockdown of EIF3H could inhibit the progression of pancreatic cancer cells by reducing proliferation capacity, promoting apoptosis, arresting cell cycle in G2 and suppressing cell migration. In summary, EIF3H may play a critical role in the development and progression of pancreatic cancer, which possesses the potential to act as a therapeutic target for pancreatic cancer treatment.

Temporal control of the integrated stress response by a stochastic molecular switch

Stress granules (SGs) are formed in the cytosol as an acute response to environmental cues and activation of the integrated stress response (ISR), a central signaling pathway controlling protein synthesis. Using chronic virus infection as stress model, we previously uncovered a unique temporal control of the ISR resulting in recurrent phases of SG assembly and disassembly. Here, we elucidate the molecular network generating this fluctuating stress response, by integrating quantitative experiments with mathematical modeling, and find that the ISR operates as a stochastic switch. Key elements controlling this switch are the cooperative activation of the stress-sensing kinase PKR, the ultrasensitive response of SG formation to the phosphorylation of the translation initiation factor eIF2alpha, and negative feedback via GADD34, a stress-induced subunit of protein phosphatase 1. We identify GADD34 mRNA levels as the molecular memory of the ISR that plays a central role in cell adaptation to acute and chronic stress.

Robust T cell activation requires an eIF3-driven burst in T cell receptor translation

Activation of T cells requires a rapid surge in cellular protein synthesis. However, the role of translation initiation in the early induction of specific genes remains unclear. Here we show human translation initiation factor eIF3 interacts with select immune system related mRNAs including those encoding the T cell receptor (TCR) subunits TCRA and TCRB. Binding of eIF3 to the TCRA and TCRB mRNA 3'-untranslated regions (3'-UTRs) depends on CD28 coreceptor signaling and regulates a burst in TCR translation required for robust T cell activation. Use of the TCRA or TCRB 3'-UTRs to control expression of an anti-CD19 chimeric antigen receptor (CAR) improves the ability of CAR-T cells to kill tumor cells in vitro. These results identify a new mechanism of eIF3-mediated translation control that can aid T cell engineering for immunotherapy applications.

Eukaryotic Translation Initiation Factor 3 Subunit B Promotes Head And Neck Cancer Via CEBPB Translation

Background: Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer type worldwide. Deregulation of mRNA translation is a frequent feature of cancer. Eukaryotic Translation Initiation Factor 3 Subunit B (EIF3B) has reported as oncogenes in cancer. However, the role of EIF3B in HNSCC remains unclear. Methods: In this study, the clinical significance of EIF3B expression in TCGA was analyzed. Then the expression of EIF3B was knockdown, and its role in HNSC was revealed. To explore the molecular mechanism of EIF3B, we applied RNA sequencing and proteomics, and deregulated pathways were acquired. RNA immunoprecipitation (RIP) sequencing was conducted to uncover the targeting mRNAs of EIF3B. Potential targets of EIF3B were validated with TCGA datasets.Results: EIF3B serves a hazardous prognostic marker in HNSCC. Besides, EIF3B promotes HNSCC proliferation and progression in vitro and in vivo. EIF3B promotes CEBPB translation and activate MAPK pathway. IL6R and CCNG2 is a target of EIF3B regulated CEBPB translation. Conclusion: In sum, this study reveals EIF3B as a novel oncogene in HNSCC, by promoting CEBPB translation and IL6R expression.

Signaling pathways involved in pancreatic stellate cells activity and interaction with pancreatic cancer cells

Background. The activation, proliferation and migration capabilities of stellate pancreatocytes are guaranteed by a number of signaling molecular mechanisms that support the interaction of tumor cells with the PSC and determine the neoplastic process. Objective The review is a continuation of aт articles series devoted to the modern understanding of the role and functions of stellate pancreatocytes, namely, their involvement in interaction with cancer cells and signaling molecular pathways that provide synergism of the stellate pancreatocyte-cancer cell system. Methods. Data processing was carried out by the method of complex material analysis. Results. The Нedgehog signaling pathway provides interaction between PSC and tumor cells, which involves the leading mediator of this pathway - sHH (sonic hedgehog), the overexpression of which is recorded in the tumor tissue of the pancreas and ensures the formation of the tumor stroma. Stellate pancreatocytes also trigger the HGF / c-Met / survivin signaling pathway for invasion and metastasis. The activation of the PSCs themselves may be mediated by serotonin via the RhoA / ROCK signaling pathway. While the proliferation and migration of these cells, activated by alcohol, HNE (human neutrophil elastase), PDGF, IL-33 PSC are regulated by the MAP kinase and PI3K pathways. The Wnt signaling pathway promotes collagen accumulation. Through the AMPK / mTOR pathway, factor FTY720 induces apoptosis and inhibits the autophagy of stellate pancreatocytes. The interaction of PSC and tumor cells is also mediated through Notch and TGF-β, and through the Hippo signaling pathway with the participation of YAP / TAZ factors, it is possible to suppress the fibrotic activity of PSC. The interaction of stellate pancreatocytes and tumor cells is reflected in a direct correlation between a decrease in autophagy and apoptosis of stellate pancreatocytes and suppression of invasion and migration of tumor cells. This interaction can be mediated by ERK1 / 2 kinase. Among the factors secreted by tumor cells and causing PSC activation are: growth factor β1 (TGF-β1), PAI-1 protein, translation initiation factor 4E (eIF4E), sHH (involving PSC in pain deployment), Exo-Pan and Exo-Mia exosomes (engaging PSCs in carcinogenesis). Deactivation is mediated by colony stimulating factor 1 (CSF1R, cytokine). In turn, stellate pancreatocytes secrete the chemokine CXCL1, which stimulates the migration and invasion of tumor cells, exosomes with multiple miRNAs, which stimulate the proliferation and migration of cancer cells. Сonclusion. The activation of stellate pancreatocytes, which is necessary for the implementation of their fibrotic functions, is mediated through the RhoA / ROCK signaling pathway via serotonin. The Hippo pathway (activation) and AMPK / mTOR (suppression of autophagy and activation of apoptosis) are also involved in the regulation of the activity of stellate pancreatocytes. The interaction between the tumor cell and stellate pancreatocyte occurs through the Hedgehog, Notch, and TGF-β signaling pathways; regulation of invasion and metastasis of cancer cells provides the HGF / c-Met / survivin signaling pathway.

Eukaryotic translation initiation factor eIF4E-5 is required for spermiogenesis in Drosophila melanogaster

Drosophila sperm development is characterized by extensive post-transcriptional regulation whereby thousands of transcripts are preserved for translation during later stages. A key step in translation initiation is the binding of eukaryotic initiation factor 4E (eIF4E) to the 5' mRNA cap. Drosophila has multiple paralogs of eIF4E, including four (eIF4E-3, -4, -5, and -7) that are highly expressed in the testis. Other than eIF4E-3, none of these has been characterized genetically. Here, using CRISPR/Cas9 mutagenesis, we determined that eIF4E-5 is essential for male fertility. eIF4E-5 mutants exhibit defects during post-meiotic stages, including a fully penetrant defect in individualization, resulting in failure to produce mature sperm. eIF4E-5 protein localizes to the distal ends of elongated spermatid cysts, where it regulates non-apoptotic caspase activity during individualization by promoting local accumulation of the E3 ubiquitin ligase inhibitor Soti. eIF4E-5 mutants also have mild defects in spermatid cyst polarization, similar to mutants affecting the cytoplasmic polyadenylation-element binding protein Orb2 and atypical protein kinase C (aPKC). Our results further extend the diversity of non-canonical eIF4Es that carry out distinct spatiotemporal roles during spermatogenesis.

The eukaryotic translation initiation factor eIF4E reprogrammes the splicing machinery and drives alternative splicing

Aberrant RNA splicing contributes to the pathogenesis of many malignancies including Acute Myeloid Leukemia (AML). While mutation is the best described mechanism underpinning aberrant splicing, recent studies show that predictions based on mutations alone likely underestimate the extent of this dysregulation1 . Here, we show that elevation of the eukaryotic translation initiation factor eIF4E reprogrammes splicing of nearly a thousand RNAs in model cell lines. In AML patient specimens which did not harbour known splice factor mutations, ~4000 transcripts were differentially spliced based on eIF4E levels and this was associated with poor prognosis. Inhibition of eIF4E in cell lines reverted the eIF4E-dependent splice events examined. Splicing targets of eIF4E act in biological processes consistent with its role in malignancy. This altered splicing program likely arose from eIF4E-dependnet increases in the production of many components of the spliceosome including SF3B1 and U2AF1 which are frequently mutated in AML. Notably, eIF4E did not drive mutation of these factors, only their production. eIF4E also physically associated with many splice factors including SF3B1, U2AF1, and UsnRNAs. Importantly, many eIF4E-dependent splice events differed from those arising from SF3B1 mutation, and were more extensive highlighting that these splicing profiles arise from distinct mechanisms. In all, our studies provide a paradigm for how dysregulation of a single factor, eIF4E, can alter splicing.

EIF4EBP1 is transcriptionally upregulated by MYCN and associates with poor prognosis in neuroblastoma

Background: Neuroblastoma (NB) accounts for 15% of cancer-related deaths in childhood despite considerable therapeutic improvements. While several risk factors, including MYCN amplification and alterations in RAS and p53 pathway genes, have been defined in NB, the clinical outcome is very variable and difficult to predict. Since genes of the mTOR pathway are up-regulated in MYCN-amplified NB, we aimed to define the predictive value of the mTOR substrate-encoding gene eukaryotic translation initiation factor 4E-binding protein 1 (EIF4EBP1) expression in NB patients. Methods: Several independent NB patient cohorts with corresponding mRNA expression data were analyzed for EIF4EBP1 expression. An institutional NB cohort consisting of 69 prospectively collected tumors was employed to immunohistochemically analyze expression of EIF4EBP1-encoded protein (4EBP1). In addition, we performed an in vitro luciferase reporter gene assay with an episomal EIF4EBP1 promoter and genetically modulated MYCN expression in NB cells. Findings: EIF4EBP1 mRNA expression was positively correlated with MYCN expression and elevated in stage 4 and high-risk NB patients. High EIF4EBP1 mRNA expression was associated with reduced overall and event-free survival in the entire group of NB patients in three cohorts, as well as in stage 4 and high-risk patients. High levels of 4EBP1 were significantly associated with prognostically unfavorable NB histology. Functional analyses in vitro revealed that EIF4EBP1 expression is transcriptionally controlled by MYCN binding to the EIF4EBP1 promoter. Interpretation: High EIF4EBP1 expression is associated with poor prognosis in NB patients and may serve to stratify patients with high-risk NB.

The Cap-Binding Complex CBC and the Eukaryotic Translation Factor eIF4E: Co-Conspirators in Cap-Dependent RNA Maturation and Translation

The translation of RNA into protein is a dynamic process which is heavily regulated during normal cell physiology and can be dysregulated in human malignancies. Its dysregulation can impact selected groups of RNAs, modifying protein levels independently of transcription. Integral to their suitability for translation, RNAs undergo a series of maturation steps including the addition of the m7G cap on the 5′ end of RNAs, splicing, as well as cleavage and polyadenylation (CPA). Importantly, each of these steps can be coopted to modify the transcript signal. Factors that bind the m7G cap escort these RNAs through different steps of maturation and thus govern the physical nature of the final transcript product presented to the translation machinery. Here, we describe these steps and how the major m7G cap-binding factors in mammalian cells, the cap binding complex (CBC) and the eukaryotic translation initiation factor eIF4E, are positioned to chaperone transcripts through RNA maturation, nuclear export, and translation in a transcript-specific manner. To conceptualize a framework for the flow and integration of this genetic information, we discuss RNA maturation models and how these integrate with translation. Finally, we discuss how these processes can be coopted by cancer cells and means to target these in malignancy.