The role of translation in neoplastic transformation from a pathologist's point of view

Overexpression of heat shock protein 47 is associated with increased proliferation and metastasis in gastric cancer

Here, we investigated that the heat shock protein 47 (HSP47) plays a crucial role in the progression of gastric cancer (GC). We analyzed HSP47 gene expression in GC cell lines and patient tissues. The HSP47 mRNA and protein expression levels were significantly higher in GC cell lines and tumor tissues compared to normal gastric mucosa. Using siRNA to silence the expression of HSP47 in GC cells resulted in a significant reduction in their proliferation, wound healing, migration, and invasion capacities. Additionally, we also showed that the mRNA expression of matrix metallopeptidase-7 (MMP-7), a metastasis-promoting gene, was significantly reduced in HSP47 siRNA-transfected GC cells. We confirmed that the HSP47 promoter region was methylated in the SNU-216 GC cell line expressing low levels of HSP47 and in most non-cancerous gastric tissues. It means that the expression of HSP47 is regulated by epigenetic regulatory mechanisms. These findings suggest that targeting HSP47, potentially through its promoter methylation, could be a useful new therapeutic strategy for treating GC.

Upstream open reading frames: new players in the landscape of cancer gene regulation

The translation of RNA by ribosomes represents a central biological process and one of the most dysregulated processes in cancer. While translation is traditionally thought to occur exclusively in the protein-coding regions of messenger RNAs (mRNAs), recent transcriptome-wide approaches have shown abundant ribosome activity across diverse stretches of RNA transcripts. The most common type of this kind of ribosome activity occurs in gene leader sequences, also known as 5' untranslated regions (UTRs) of the mRNA, that precede the main coding sequence. Translation of these upstream open reading frames (uORFs) is now known to occur in upwards of 25% of all protein-coding genes. With diverse functions from RNA regulation to microprotein generation, uORFs are rapidly igniting a new arena of cancer biology, where they are linked to cancer genetics, cancer signaling, and tumor-immune interactions. This review focuses on the contributions of uORFs and their associated 5'UTR sequences to cancer biology.

Discrete Mechanistic Target of Rapamycin Signaling Pathways, Stem Cells, and Therapeutic Targets

The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that functions via its discrete binding partners to form two multiprotein complexes, mTOR complex 1 and 2 (mTORC1 and mTORC2). Rapamycin-sensitive mTORC1, which regulates protein synthesis and cell growth, is tightly controlled by PI3K/Akt and is nutrient-/growth factor-sensitive. In the brain, mTORC1 is also sensitive to neurotransmitter signaling. mTORC2, which is modulated by growth factor signaling, is associated with ribosomes and is insensitive to rapamycin. mTOR regulates stem cell and cancer stem cell characteristics. Aberrant Akt/mTOR activation is involved in multistep tumorigenesis in a variety of cancers, thereby suggesting that the inhibition of mTOR may have therapeutic potential. Rapamycin and its analogues, known as rapalogues, suppress mTOR activity through an allosteric mechanism that only suppresses mTORC1, albeit incompletely. ATP-catalytic binding site inhibitors are designed to inhibit both complexes. This review describes the regulation of mTOR and the targeting of its complexes in the treatment of cancers, such as glioblastoma, and their stem cells.

eIF3i promotes colorectal cancer cell survival via augmenting PHGDH translation

Translational regulation is one of the decisive steps in gene expression, and its dysregulation is closely related to tumorigenesis. Eukaryotic translation initiation factor 3 subunit i (eIF3i) promotes tumor growth by selectively regulating gene translation, but the underlying mechanisms are largely unknown. Here, we show that eIF3i is significantly increased in colorectal cancer (CRC) and reinforces the proliferation of CRC cells. Using ribosome profiling and proteomics analysis, several genes regulated by eIF3i at the translation level were identified, including D-3-phosphoglycerate dehydrogenase (PHGDH), a rate-limiting enzyme in the de novo serine synthesis pathway that participates in metabolic reprogramming of tumor cells. PHGDH knockdown significantly represses CRC cell proliferation and partially attenuates the excessive growth induced by eIF3i overexpression. Mechanistically, METTL3-mediated N6-methyladenosine modification on PHGDH mRNA promotes its binding with eIF3i, ultimately leading to a higher translational rate. In addition, knocking down eIF3i and PHGDH impedes tumor growth in vivo. Collectively, this study not only uncovered a novel regulatory mechanism for PHGDH translation but also demonstrated that eIF3i is a critical metabolic regulator in human cancer.

eIF3a sustains non-small cell lung cancer stem cell-like properties by promoting YY1-mediated transcriptional activation of β-catenin

Cancer stem cells (CSCs) are the leading cause of recurrence and poor prognosis in non-small cell lung cancer (NSCLC). Eukaryotic translation initiation factor 3a (eIF3a) participates in many tumor development processes, such as metastasis, therapy resistance, and glycolysis, all of which are closely associated with the presence of CSCs. However, whether eIF3a maintains NSCLC-CSC-like properties remains to be elucidated. In this study, eIF3a was highly expressed in lung cancer tissues and was linked to poor prognosis. eIF3a was also highly expressed in CSC-enriched spheres compared with adherent monolayer cells. Moreover, eIF3a is required for NSCLC stem cell-like traits maintenance in vitro and in vivo. Mechanistically, eIF3a activates the Wnt/β-catenin signaling pathway, promoting the transcription of cancer stem cell markers. Specifically, eIF3a promotes the transcriptional activation of β-catenin and mediates its nuclear accumulation to form a complex with T cell factor 4 (TCF4). However, eIF3a has no significant effect on protein stability and translation. Proteomics analysis revealed that the candidate transcription factor, Yin Yang 1 (YY1), mediates the activated effect of eIF3a on β-catenin. Overall, the findings of this study implied that eIF3a contributes to the maintenance of NSCLC stem cell-like characteristics through the Wnt/β-catenin pathway. eIF3a is a potential target for the treatment and prognosis of NSCLC.

Identification of specific role of SNX family in gastric cancer prognosis evaluation

We here perform a systematic bioinformatic analysis to uncover the role of sorting nexin (SNX) family in clinical outcome of gastric cancer (GC). Comprehensive bioinformatic analysis were realized with online tools such as TCGA, GEO, String, Timer, cBioportal and Kaplan-Meier Plotter. Statistical analysis was conducted with R language or Perl, and artificial neural network (ANN) model was established using Python. Our analysis demonstrated that SNX4/5/6/7/8/10/13/14/15/16/20/22/25/27/30 were higher expressed in GC, whereas SNX1/17/21/24/33 were in the opposite expression profiles. GSE66229 was employed as verification of the differential expression analysis based on TCGA. Clustering results gave the relative transcriptional levels of 30 SNXs in tumor, and it was totally consistent to the inner relevance of SNXs at mRNA level. Protein-Protein Interaction map showed closely and complex connection among 33 SNXs. Tumor immune infiltration analysis asserted that SNX1/3/9/18/19/21/29/33, SNX1/17/18/20/21/29/31/33, SNX1/2/3/6/10/18/29/33, and SNX1/2/6/10/17/18/20/29 were strongly correlated with four kinds of survival related tumor-infiltrating immune cells, including cancer associated fibroblast, endothelial cells, macrophages and Tregs. Kaplan-Meier survival analysis based on GEO presented more satisfactory results than that based on TCGA-STAD did, and all the 29 SNXs were statistically significant, SNX23/26/28 excluded. SNXs alteration contributed to microsatellite instability (MSI) or higher level of MSI-H (hyper-mutated MSI or high level of MSI), and other malignancy encompassing mutation of TP53 and ARID1A, as well as methylation of MLH1.The multivariate cox model, visualized as a nomogram, performed excellently in patients risk classification, for those with higher risk-score suffered from shorter overall survival (OS). Compared to previous researches, our ANN models showed a predictive power at a middle-upper level, with AUC of 0.87/0.72, 0.84/0.72, 0.90/0.71 (GSE84437), 0.98/0.66, 0.86/0.70, 0.98/0.71 (GSE66229), 0.94/0.66, 0.83/0.71, 0.88/0.72 (GSE26253) corresponding to one-, three- and five-year OS and recurrence free survival (RFS) estimation, especially ANN model built with GSE66229 including exclusively SNXs as input data. The SNX family shows great value in postoperative survival evaluation of GC, and ANN models constructed using SNXs transcriptional data manifesting excellent predictive power in both OS and RFS prediction works as convincing verification to that.

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.

Targeting cancer via ribosome biogenesis: the cachexia perspective

Cancer cachexia afflicts many advanced cancer patients with many progressing to death. While there have been many advancements in understanding the molecular mechanisms that contribute to the development of cancer cachexia, substantial gaps still exist. Chemotherapy drugs often target ribosome biogenesis to slow or blunt tumor cell growth and proliferation. Some of the most frequent side-effects of chemotherapy are loss of skeletal muscle mass, muscular strength and an increase in fatigue. Given that ribosome biogenesis has emerged as a main mechanism regulating muscle hypertrophy, and more recently, also implicated in muscle atrophy, we propose that some chemotherapy drugs can cause further muscle wasting via its effect on skeletal muscle cells. Many chemotherapy drugs, including the most prescribed drugs such as doxorubicin and cisplatin, affect ribosomal DNA transcription, or other pathways related to ribosome biogenesis. Furthermore, middle-aged and older individuals are the most affected population with cancer, and advanced cancer patients often show reduced levels of physical inactivity. Thus, aging and inactivity can themselves affect muscle ribosome biogenesis, which can further worsen the effect of chemotherapy on skeletal muscle ribosome biogenesis and, ultimately, muscle mass and function. We propose that chemotherapy can accelerate the onset or worsen cancer cachexia via its inhibitory effects on skeletal muscle ribosome biogenesis. We end our review by providing recommendations that could be used to ameliorate the negative effects of chemotherapy on skeletal muscle ribosome biogenesis.

miRNA-467b inhibits Th17 differentiation by targeting eIF4E in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are neuroinflammatory autoimmune diseases characterized by the axonal loss, demyelination, and neurodegeneration of the central nervous system. Overactivation of CD4⁺ T cells, especially the migration of the Th1 and Th17 subsets into the central nervous system (CNS), leads to the secretion of inflammatory mediators and destruction of the contact between neurons and activated macrophages, which can then result in a series of neurocognitive and motor deficits. In this study, we intended to explore the role of miRNA-467b in regulating Th cell development in EAE. We found that the level of miRNA-467b was decreased and eukaryotic initiation factor 4 F (eIF4E) was increased in lymph nodes and the CNS at EAE peak. eIF4E was confirmed as the direct target of miRNA467b. Overexpression of miRNA-467b could suppress a percentage of CD4⁺ IL-17⁺ cells in EAE CD4 + T cells in vitro. In addition, we also identified miRNA-467b, which could suppress Th17 cell differentiation by targeting eIF4E in vitro. Furthermore, injecting miRNA-467b mimics into the caudal vein of EAE mice contributed to less inflammation in the peripheral lymphoid organs and CNS and alleviated disease severity. Taken together, our findings imply that miRNA-467b inhibits the differentiation and function of Th17 cells by targeting eIF4E, thereby alleviating EAE.

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.

Ribosome Biogenesis Alterations in Colorectal Cancer

Many studies have focused on understanding the regulation and functions of aberrant protein synthesis in colorectal cancer (CRC), leaving the ribosome, its main effector, relatively underappreciated in CRC. The production of functional ribosomes is initiated in the nucleolus, requires coordinated ribosomal RNA (rRNA) processing and ribosomal protein (RP) assembly, and is frequently hyperactivated to support the needs in protein synthesis essential to withstand unremitting cancer cell growth. This elevated ribosome production in cancer cells includes a strong alteration of ribosome biogenesis homeostasis that represents one of the hallmarks of cancer cells. None of the ribosome production steps escape this cancer-specific dysregulation. This review summarizes the early and late steps of ribosome biogenesis dysregulations described in CRC cell lines, intestinal organoids, CRC stem cells and mouse models, and their possible clinical implications. We highlight how this cancer-related ribosome biogenesis, both at quantitative and qualitative levels, can lead to the synthesis of ribosomes favoring the translation of mRNAs encoding hyperproliferative and survival factors. We also discuss whether cancer-related ribosome biogenesis is a mere consequence of cancer progression or is a causal factor in CRC, and how altered ribosome biogenesis pathways can represent effective targets to kill CRC cells. The association between exacerbated CRC cell growth and alteration of specific steps of ribosome biogenesis is highlighted as a key driver of tumorigenesis, providing promising perspectives for the implementation of predictive biomarkers and the development of new therapeutic drugs.

Silencing of BRF2 inhibits the growth and metastasis of lung cancer cells

Transcription factor II B (TFIIB)‑related factor 2 (BRF2) is involved in the development of cancer, but its role in lung cancer is underreported. The present study aimed to explore the role of BRF2 in the regulation of lung cancer cells. Immunofluorescence staining and immunohistochemistry were performed to detect BRF2 protein expression in human lung cancer cells and tissues. Following cell transfection with small interfering RNA for silencing BRF2, the cell proliferation was examined by Cell Counting Kit‑8 and MTT assays. Cell apoptosis, migration and invasion were determined by flow cytometry, wound‑healing and Transwell assay. The expression levels of Akt, phosphorylated (p)‑Akt, Bax, E‑cadherin, Bcl‑2, N‑cadherin, Snail and epidermal growth factor receptor (EGFR) in human lung cancer A549 cells were detected by western blotting. The results demonstrated that BRF2 expression was increased in human lung cancer cells and tissues, and that silencing of BRF2 promoted cell apoptosis but inhibited cell proliferation and migration. The protein expression levels of Akt, E‑cadherin, p‑Akt, Bcl‑2, N‑cadherin, Snail and EGFR in A549 cells were inhibited by silencing of BRF2, while expression levels of Bax and E‑cadherin were increased by silencing BRF2. In conclusion, BRF2 demonstrates high expression in lung cancer and silencing of BRF2 inhibits the growth and metastasis of lung cancer cells. The current findings provide a novel approach for the treatment of lung cancer.

SAMMSON fosters cancer cell fitness by concertedly enhancing mitochondrial and cytosolic translation

Synchronization of mitochondrial and cytoplasmic translation rates is critical for the maintenance of cellular fitness, with cancer cells being especially vulnerable to translational uncoupling. Although alterations of cytosolic protein synthesis are common in human cancer, compensating mechanisms in mitochondrial translation remain elusive. Here we show that the malignant long non-coding RNA (lncRNA) SAMMSON promotes a balanced increase in ribosomal RNA (rRNA) maturation and protein synthesis in the cytosol and mitochondria by modulating the localization of CARF, an RNA-binding protein that sequesters the exo-ribonuclease XRN2 in the nucleoplasm, which under normal circumstances limits nucleolar rRNA maturation. SAMMSON interferes with XRN2 binding to CARF in the nucleus by favoring the formation of an aberrant cytoplasmic RNA-protein complex containing CARF and p32, a mitochondrial protein required for the processing of the mitochondrial rRNAs. These data highlight how a single oncogenic lncRNA can simultaneously modulate RNA-protein complex formation in two distinct cellular compartments to promote cell growth.

eIF4E Phosphorylation in Prostate Cancer

Prostate cancer (PCa) progression involves a shift from endocrine to paracrine and eventually autocrine control resulting from alterations in molecular mechanisms in the cells. Deregulation of RNA translation is crucial for tumor cells to grow and proliferate; therefore, overactivation of the translation machinery is often observed in cancer. The two most important signal transduction pathways regulating PCa progression are PI3K/Akt/mTOR and Ras/MAPK. These two pathways converge on the eukaryotic translation initiation factor 4E (eIF4E) which binds to the protein scaffold eIF4G upon mechanistic target of rapamycin (mTOR) activation and is phosphorylated by the mitogen-activated protein kinase (MAPK) interacting protein kinases (Mnk1/2). This review describes the role of eIF4E in mRNA translation initiation mediated by its binding to the methylated 5′ terminal structure (m7G-cap) of many mRNAs, and the ability of many tumor cells to bypass this mechanism. Hormonal therapy and chemotherapy are two of the most prevalent therapies used in patients with advanced PCa, and studies have implicated a role for eIF4E phosphorylation in promoting resistance to both these therapies. It appears that eIF4E phosphorylation enhances the rate of translation of oncogene mRNAs to increase tumorigenicity.

Immunohistochemical Expression of TGF-Β1, SMAD4, SMAD7, TGFβRII and CD68-Positive TAM Densities in Papillary Thyroid Cancer

BACKGROUND:

Papillary thyroid carcinoma (PTC) accounts for 80% of the thyroid malignancies that are characterised by slow growth and an excellent prognosis. Over-expression of SMAD4 protein restores TGF-β signalling, determines a strong increase in anti-proliferative effect and reduces invasive potential of tumour cells expressing it.

AIM:

The study aimed to analyse the immunohistochemical expression of TGF-β1 and its downstream phosphorylated SMAD4, element and of the inhibitory SMAD7 PTC variants and their association with the localisation of TAMs within the tumour microenvironment.

METHODS:

For this retrospective study we investigated 69 patients immunohistochemistry with antibodies against TGF-β, TGF – β-RII, SMAD4, SMAD7, CD68+ macrophages.

RESULTS:

Patients with low infiltration with CD68+ cells in tumour stroma has significantly shorter survival (median of 129.267 months) compared to those with high CD68+ cells infiltration (p = 0.034). From the analysis of CD68+ cells in tumour border and tumour stroma correlated with expression of TGF-β1 / SMAD proteins, we observed that the positive expression of TGF-β1 in tumour cytoplasm, significantly correlated with increased number of CD68+ cells in tumour border (X² = 5,945; p = 0.015).

CONCLUSION:

TGF-β enhances motility and stimulates recruitment of monocytes, macrophages and other immune cells while directly inhibiting their anti-tumour effector functions.

The correlation between gain of chromosome 8q and survival in patients with clear and papillary renal cell carcinoma

Background

The proto-oncogene c-MYC, located on chromosome 8q, can be upregulated through gain of 8q, causing alteration in biology of renal cell carcinoma (RCC). The aim of this study was to evaluate the prevalence of c-MYC through chromosome 8q gain and to correlate findings with cancer-specific mortality (CSM), and overall survival (OS).

Methods

Cytogenetic analysis by conventional or Chromosomal Genomic Microarray Analysis (CMA) was performed on 414 renal tumors. Nonclear and nonpapillary RCC were excluded. Impact of gain in chromosome 8q status on CSM, OS, and its correlation with clinicopathological variables were evaluated. CSM and OS were assessed using log-rank test and the Cox proportional hazards model.

Results

A total of 297 RCC tumors with cytogenetic analysis were included. Gain of 8q was detected in 18 (6.1%) tumors (9 clear cell and 9 papillary RCC), using conventional method (n = 11) or CMA (n = 7). Gain of 8q was associated with higher T stage (p < 0.001), grade (p < 0.001), nodal involvement (p = 0.005), and distant metastasis (p < 0.001). No association between gain of 8q and age (p = 0.23), sex (p = 0.46), and Charlson comorbidity index (CCI, p = 0.59) were seen. Gain of 8q was associated with an 8.38-fold [95% confidence interval (CI), 3.83-18.34, p < 0.001] and 3.31-fold (95% CI, 1.56-7.04, p = 0.001) increase in CSM and decrease in OS, respectively, at a median follow up of 56 months.

Conclusion

Chromosome 8q harbors the proto-oncogene c-MYC, which can be upregulated by gain of 8q. Our findings suggest that gain of 8q, can predict aggressive tumor phenotype and inferior survival in RCC.

Eukaryotic elongation factor 2 is a prognostic marker and its kinase a potential therapeutic target in HCC

Hepatocellular carcinoma is a cancer with increasing incidence and largely refractory to current anticancer drugs. Since Sorafenib, a multikinase inhibitor has shown modest efficacy in advanced hepatocellular carcinoma additional treatments are highly needed. Protein phosphorylation via kinases is an important post-translational modification to regulate cell homeostasis including proliferation and apoptosis. Therefore kinases are valuable targets in cancer therapy. To this end we performed 2D differential gel electrophoresis and mass spectrometry analysis of phosphoprotein-enriched lysates of tumor and corresponding non-tumorous liver samples to detect differentially abundant phosphoproteins to screen for novel kinases as potential drug targets. We identified 34 differentially abundant proteins in phosphoprotein enriched lysates. Expression and distribution of the candidate protein eEF2 and its phosphorylated isoform was validated immunohistochemically on 78 hepatocellular carcinoma and non-tumorous tissue samples. Validation showed that total eEF2 and phosphorylated eEF2 at threonine 56 are prognostic markers for overall survival of HCC-patients. The activity of the regulating eEF2 kinase, compared between tumor and non-tumorous tissue lysates by in vitro kinase assays, is more than four times higher in tumor tissues. Functional analyzes regarding eEF2 kinase were performed in JHH5 cells with CRISPR/Cas9 mediated eEF2 kinase knock out. Proliferation and growth is decreased in eEF2 kinase knock out cells.

Deletion of eIF2β lysine stretches creates a dominant negative that affects the translation and proliferation in human cell line: A tool for arresting the cell growth

BACKGROUND

Eukaryote initiation factor 2 subunit β (eIF2β) plays a crucial role in regulation protein synthesis, which mediates the interaction of eIF2 with mRNA. eIF2β contains evolutionarily conserved polylysine stretches in amino-terminal region and a zinc finger motif in the carboxy-terminus.

METHODS

The gene eIF2β was cloned under tetracycline transcription control and the polylysine stretches were deleted by site-directed mutagenesis (eIF2βΔ3K). The plasmid was transfected into HEK 293 TetR cells. These cells were analyzed for their proliferative and translation capacities as well as cell death rate. Experiments were performed using gene reporter assays, western blotting, flow cytometry, cell sorting, cell proliferation assays and confocal immunofluorescence.

RESULTS

eIF2βΔ3K affected negatively the protein synthesis, cell proliferation and cell survival causing G2 cell cycle arrest and increased cell death, acting in a negative dominant manner against the native protein. Polylysine stretches are also essential for eIF2β translocated from the cytoplasm to the nucleus, accumulating in the nucleolus and eIF2βΔ3K did not make this translocation.

DISCUSSION

eIF2β is involved in the protein synthesis process and should act in nuclear processes as well. eIF2βΔ3K reduces cell proliferation and causes cell death. Since translation control is essential for normal cell function and survival, the development of drugs or molecules that inhibit translation has become of great interest in the scenario of proliferative disorders. In conclusion, our results suggest the dominant negative eIF2βΔ3K as a therapeutic strategy for the treatment of proliferative disorders and that eIF2β polylysine stretch domains are promising targets for this.

Novel Assay to Detect RNA Polymerase I Activity In Vivo

This report develops an analytically validated chromogenic in situ hybridization (CISH) assay using branched DNA signal amplification (RNAscope) for detecting the expression of the 5' external transcribed spacer (ETS) of the 45S ribosomal (r) RNA precursor in formalin-fixed and paraffin-embedded (FFPE) human tissues. 5'ETS/45S CISH was performed on standard clinical specimens and tissue microarrays (TMA) from untreated prostate carcinomas, high-grade prostatic intraepithelial neoplasia (PIN), and matched benign prostatic tissues. Signals were quantified using image analysis software. The 5'ETS rRNA signal was restricted to the nucleolus. The signal was markedly attenuated in cell lines and in prostate tissue slices after pharmacologic inhibition of RNA polymerase I (Pol I) using BMH-21 or actinomycin D, and by RNAi depletion of Pol I, demonstrating validity as a measure of Pol I activity. Clinical human prostate FFPE tissue sections and TMAs showed a marked increase in the signal in the presumptive precursor lesion (high-grade PIN) and invasive adenocarcinoma lesions (P = 0.0001 and P = 0.0001, respectively) compared with non-neoplastic luminal epithelium. The increase in 5'ETS rRNA signal was present throughout all Gleason scores and pathologic stages at radical prostatectomy, with no marked difference among these. This precursor rRNA assay has potential utility for detection of increased rRNA production in various tumor types and as a novel companion diagnostic for clinical trials involving Pol I inhibition.Implications: Increased rRNA production, a possible therapeutic target for multiple cancers, can be detected with a new, validated assay that also serves as a pharmacodynamic marker for Pol I inhibitors. Mol Cancer Res; 15(5); 577-84. ©2017 AACR.

eIF3 controls cell size independently of S6K1-activity

All multicellular organisms require a life-long regulation of the number and the size of cells, which build up their organs. mTOR acts as a signaling nodule for the regulation of protein synthesis and growth. To activate the translational cascade, mTOR phosphorylates S6 kinase (S6K1), which is liberated from the eIF3-complex and mobilized for activation of its downstream targets. How S6K1 regulates cell size remains unclear. Here, we challenged cell size control through S6K1 by specifically depleting its binding partner eIF3 in normal and transformed cell lines. We show that loss of eIF3 leads to a massive reduction of cell size and cell number accompanied with an unexpected increase in S6K1-activity. The hyperactive S6K1-signaling was rapamycin-sensitive, suggesting an upstream mTOR-regulation. A selective S6K1 inhibitor (PF-4708671) was unable to interfere with the reduced size, despite efficiently inhibiting S6K1-activity. Restoration of eIF3 expression recovered size defects, without affecting the p-S6 levels. We further show that two, yet uncharacterized, cancer-associated mutations in the eIF3-complex, have the capacity to recover from reduced size phenotype, suggesting a possible role for eIF3 in regulating cancer cell size. Collectively, our results uncover a role for eIF3-complex in maintenance of normal and neoplastic cell size - independent of S6K1-signaling.

Spatial and temporal translational control of germ cell mRNAs mediated by the eIF4E isoform IFE-1

Regulated mRNA translation is vital for germ cells to produce new proteins in the spatial and temporal patterns that drive gamete development. Translational control involves the de-repression of stored mRNAs and their recruitment by eukaryotic initiation factors (eIFs) to ribosomes. C. elegans expresses five eIF4Es (IFE-1-IFE-5); several have been shown to selectively recruit unique pools of mRNA. Individual IFE knockouts yield unique phenotypes due to inefficient translation of certain mRNAs. Here, we identified mRNAs preferentially translated through the germline-specific eIF4E isoform IFE-1. Differential polysome microarray analysis identified 77 mRNAs recruited by IFE-1. Among the IFE-1-dependent mRNAs are several required for late germ cell differentiation and maturation. Polysome association of gld-1, vab-1, vpr-1, rab-7 and rnp-3 mRNAs relies on IFE-1. Live animal imaging showed IFE-1-dependent selectivity in spatial and temporal translation of germline mRNAs. Altered MAPK activation in oocytes suggests dual roles for IFE-1, both promoting and suppressing oocyte maturation at different stages. This single eIF4E isoform exerts positive, selective translational control during germ cell differentiation.

Molecular Docking studies of FKBP12-mTOR inhibitors using binding predictions

Mammalian target of rapamycin (mTOR) is a key regulator of cell growth, proliferation and angiogenesis. mTOR signaling is frequently hyper activated in a broad spectrum of human cancers thereby making it a potential drug target. The current drugs available have been successful in inhibiting the mTOR signaling, nevertheless, show low oral bioavailability and suboptimal solubility. Considering the narrow therapeutic window of the available inhibitors, through computational approaches, the present study pursues to identify a compound with optimal oral bioavailability and better solubility properties in addition ensuing high affinity between FKBP12 and FRB domain of mTOR. Current mTOR inhibitors; Everolimus, Temsirolimus Deforolimus and Echinomycin served as parent molecules for similarity search with a threshold of 95%. The query molecules and respective similar molecules were docked at the binding cleft of FKBP12 protein. Aided by MolDock algorithm, high affinity compounds against FKBP12 were retrieved. Patch Dock supervised protein-protein interactions were established between FRB domain of mTOR and ligand (query and similar) bound and free states of FKBP12. All the similar compounds thus retrieved showed better solubility properties and enabled better complex formation of mTOR and FKBP12. In particular Everolimus similar compound PubChem ID: 57284959 showed appreciable drugs like properties bestowed with better solubility higher oral bioavailability. In addition this compound brought about enhanced interaction between FKBP12 and FRB domain of mTOR. In the study, we report Everolimus similar compound PubChem ID: 57284959 to be potential inhibitor for mTOR pathway which can overcome the affinity and solubility concerns of current mTOR drugs.

ABBREVIATIONS

mTOR - Mammalian Target of Rapamycin, FRB domain - FKBP12-rapamycin associated protein, FKBP12 - FK506-binding protein 12, OPLS - Optimized Potentials for Liquid Simulations, Akt - RAC-alpha serine/threonine-protein kinase, PI3K - phosphatidylinositide 3-kinases.

Maduramicin inhibits proliferation and induces apoptosis in myoblast cells

Maduramicin, a polyether ionophore antibiotic derived from the bacterium Actinomadura yumaensis, is currently used as a feed additive against coccidiosis in poultry worldwide. It has been clinically observed that maduramicin can cause skeletal muscle and heart cell damage, resulting in skeletal muscle degeneration, heart failure, and even death in animals and humans, if improperly used. However, the mechanism of its toxic action in myoblasts is not well understood. Using mouse myoblasts (C2C12) and human rhabdomyosarcoma (RD and Rh30) cells as an experimental model for myoblasts, here we found that maduramicin inhibited cell proliferation and induced cell death in a concentration-dependent manner. Further studies revealed that maduramicin induced accumulation of the cells at G₀/G₁ phase of the cell cycle, and induced apoptosis in the cells. Concurrently, maduramicin downregulated protein expression of cyclin D1, cyclin-dependent kinases (CDK4 and CDK6), and CDC25A, and upregulated expression of the CDK inhibitors (p21^Cip1 and p27^Kip1), resulting in decreased phosphorylation of Rb. Maduramicin also induced expression of BAK, BAD, DR4, TRADD and TRAIL, leading to activation of caspases 8, 9 and 3 as well as cleavage of poly ADP ribose polymerase (PARP). Taken together, our results suggest that maduramicin executes its toxicity in myoblasts at least by inhibiting cell proliferation and inducing apoptotic cell death.

Distinct signaling mechanisms of mTORC1 and mTORC2 in glioblastoma multiforme: a tale of two complexes

Mechanistic target of rapamycin (mTOR) is a serine-threonine kinase that functions via two multiprotein complexes, namely mTORC1 and mTORC2, each characterized by different binding partners that confer separate functions. mTORC1 function is tightly regulated by PI3-K/Akt and is sensitive to rapamycin. mTORC2 is sensitive to growth factors, not nutrients, and is associated with rapamycin-insensitivity. mTORC1 regulates protein synthesis and cell growth through downstream molecules: 4E-BP1 (also called EIF4E-BP1) and S6K. Also, mTORC2 is thought to modulate growth factor signaling by phosphorylating the C-terminal hydrophobic motif of some AGC kinases such as Akt and SGK. Recent evidence has suggested that mTORC2 may play an important role in maintenance of normal as well as cancer cells by virtue of its association with ribosomes, which may be involved in metabolic regulation of the cell. Rapamycin (sirolimus) and its analogs known as rapalogues, such as RAD001 (everolimus) and CCI-779 (temsirolimus), suppress mTOR activity through an allosteric mechanism that acts at a distance from the ATP-catalytic binding site, and are considered incomplete inhibitors. Moreover, these compounds suppress mTORC1-mediated S6K activation, thereby blocking a negative feedback loop, leading to activation of mitogenic pathways promoting cell survival and growth. Consequently, mTOR is a suitable target of therapy in cancer treatments. However, neither of these complexes is fully inhibited by the allosteric inhibitor rapamycin or its analogs. In recent years, new pharmacologic agents have been developed which can inhibit these complexes via ATP-binding mechanism, or dual inhibition of the canonical PI3-K/Akt/mTOR signaling pathway. These compounds include WYE-354, KU-003679, PI-103, Torin1, and Torin2, which can target both complexes or serve as a dual inhibitor for PI3-K/mTOR. This investigation describes the mechanism of action of pharmacological agents that effectively target mTORC1 and mTORC2 resulting in suppression of growth, proliferation, and migration of tumor and cancer stem cells.

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.

The impact of PKR activation: from neurodegeneration to cancer

An inverse association between cancer and neurodegeneration is plausible because these biological processes share several genes and signaling pathways. Whereas uncontrolled cell proliferation and decreased apoptotic cell death governs cancer, excessive apoptosis contributes to neurodegeneration. Protein kinase R (PKR), an interferon-inducible double-stranded RNA protein kinase, is involved in both diseases. PKR activation blocks global protein synthesis through eIF2α phosphorylation, leading to cell death in response to a variety of cellular stresses. However, PKR also has the dual role of activating the nuclear factor κ-B pathway, promoting cell proliferation. Whereas PKR is recognized for its negative effects on neurodegenerative diseases, in part, inducing high level of apoptosis, the role of PKR activation in cancer remains controversial. In general, PKR is considered to have a tumor suppressor function, and some clinical data show a correlation between suppressed or inactivated PKR and a poor prognosis for several cancers. However, other studies show high PKR expression and activation levels in various cancers, suggesting that PKR might contribute to neoplastic progression. Understanding the cellular factors and signals involved in the regulation of PKR in these age-related diseases is relevant and may have important clinical implications. The present review highlights the current knowledge on the role of PKR in neurodegeneration and cancer, with special emphasis on its regulation and clinical implications.

Potentiation of cytotoxic chemotherapy by growth hormone-releasing hormone agonists

The dismal prognosis of malignant brain tumors drives the development of new treatment modalities. In view of the multiple activities of growth hormone-releasing hormone (GHRH), we hypothesized that pretreatment with a GHRH agonist, JI-34, might increase the susceptibility of U-87 MG glioblastoma multiforme (GBM) cells to subsequent treatment with the cytotoxic drug, doxorubicin (DOX). This concept was corroborated by our findings, in vivo, showing that the combination of the GHRH agonist, JI-34, and DOX inhibited the growth of GBM tumors, transplanted into nude mice, more than DOX alone. In vitro, the pretreatment of GBM cells with JI-34 potentiated inhibitory effects of DOX on cell proliferation, diminished cell size and viability, and promoted apoptotic processes, as shown by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide proliferation assay, ApoLive-Glo multiplex assay, and cell volumetric assay. Proteomic studies further revealed that the pretreatment with GHRH agonist evoked differentiation decreasing the expression of the neuroectodermal stem cell antigen, nestin, and up-regulating the glial maturation marker, GFAP. The GHRH agonist also reduced the release of humoral regulators of glial growth, such as FGF basic and TGFβ. Proteomic and gene-expression (RT-PCR) studies confirmed the strong proapoptotic activity (increase in p53, decrease in v-myc and Bcl-2) and anti-invasive potential (decrease in integrin α3) of the combination of GHRH agonist and DOX. These findings indicate that the GHRH agonists can potentiate the anticancer activity of the traditional chemotherapeutic drug, DOX, by multiple mechanisms including the induction of differentiation of cancer cells.

Inhibition of U-87 MG glioblastoma by AN-152 (AEZS-108), a targeted cytotoxic analog of luteinizing hormone-releasing hormone

Glioblastoma multiforme is the most frequent tumor of the central nervous system in adults and has a dismal clinical outcome, which necessitates the development of new therapeutic approaches. We investigated in vivo the action of the targeted cytotoxic analog of luteinizing hormone releasing hormone, AN-152 (AEZS-108) in nude mice (Ncr nu/nu strain) bearing xenotransplanted U-87 MG glioblastoma tumors. We evaluated in vitro the expression of LHRH receptors, proliferation, apoptosis and the release of oncogenic and tumor suppressor cytokines. Clinical and U-87 MG samples of glioblastoma tumors expressed LHRH receptors. Treatment of nude mice with AN-152, once a week at an intravenous dose of 413 nmol/20g, for six weeks resulted in 76 % reduction in tumor growth. AN-152 nearly completely abolished tumor progression and elicited remarkable apoptosis in vitro. Genomic (RT-PCR) and proteomic (ELISA, Western blot) studies revealed that AN-152 activated apoptosis, as reflected by the changes in p53 and its regulators and substrates, inhibited cell growth, and elicited changes in intermediary filament pattern. AN-152 similarly reestablished contact regulation as demonstrated by expression of adhesion molecules and inhibited vascularization, as reflected by the transcription of angiogenic factors. Our findings suggest that targeted cytotoxic analog AN-152 (AEZS-108) should be considered for a treatment of glioblastomas.

Repression of microRNA-768-3p by MEK/ERK signalling contributes to enhanced mRNA translation in human melanoma

Increased global protein synthesis and selective translation of mRNAs encoding proteins contributing to malignancy is common in cancer cells. This is often associated with elevated expression of eukaryotic translation initiation factor 4 (eIF4E), the rate-limiting factor of cap-dependent translation initiation. We report here that in human melanoma downregulation of miR-768-3p as a result of activation of the mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway has an important role in the upregulation of eIF4E and enhancement in protein synthesis. Melanoma cells displayed increased nascent protein production and elevated eIF4E expression, which was associated with the downregulation of miR-768-3p that was predicted to target the 3'-untranslated region of the eIF4E mRNA. Overexpression of miR-768-3p led to the downregulation of the endogenous eIF4E protein, reduction in nascent protein synthesis and inhibition of cell survival and proliferation. These effects were efficiently reversed when eIF4E was co-overexpressed in melanoma cells. On the other hand, introduction of anti-miR-768-3p into melanocytes upregulated endogenous eIF4E protein expression and increased global protein synthesis. Downregulation of miR-768-3p appeared to be mediated by activation of the MEK/ERK pathway, in that treatment of BRAF(V600E) melanoma cells with the mutant BRAF inhibitor PLX4720 or exposure of either BRAF(V600E) or wild-type BRAF melanoma cells to the MEK inhibitor U0126 resulted in the upregulation of miR-768-3p and inhibition of nascent protein synthesis. This inhibition was partially blocked in cells cointroduced with anti-miR-768-3p. Significantly, miR-768-3p was similarly downregulated, which was inversely associated with the expression levels of eIF4E in fresh melanoma isolates. Taken together, these results identify downregulation of miR-768-3p and subsequent upregulation of eIF4E as an important mechanism in addition to phosphorylation of eIF4E responsible for MEK/ERK-mediated enhancement of protein synthesis in melanoma.

Deletions of chromosomes 3p and 14q molecularly subclassify clear cell renal cell carcinoma

BACKGROUND

The short arm of chromosome 3 (3p) harbors the von Hippel-Lindau (VHL) tumor suppressor gene, and the long arm of chromosome 14 (14q) harbors the hypoxia-inducible factor 1α (HIF-1α) gene. The objective of this study was to evaluate the significance of 3p loss (loss VHL gene) and 14q loss (loss HIF-1α gene) in clear cell renal cell carcinoma (ccRCC).

METHODS

In total, 288 ccRCC tumors underwent a prospective cytogenetic analysis for alterations in chromosomes 3p and 14q. Tumors were assigned to 1 of 4 possible chromosomal alterations: VHL +3p/+14q (VHL wild type [VHL-WT]), VHL +3p/-14q (VHL-WT plus HIF2α [WT/H2]), -3p/+14q (HIF1α and HIF2α [H1H2]), and -3p/-14q (HIF2α [H2]).

RESULTS

Among patients who had loss of 3p, tumors with -3p/-14q (H2) alterations were larger (P = .002), had higher grade (P = .002) and stage (P = .001), and more often were metastatic (P = .029) than tumors that retained 14q (H1H2). All patients who had tumors with -3p/-14q (H2) had worse cancer-specific survival (P = .014), and patients who had localized disease (P = .012) and primary T1 (pT1) tumors (P = .008) had worse recurrence-free survival. In patients who had pT1 tumors, combined 3p/14q loss was an independent predictor of recurrence-free survival (hazard ratio, 11.19; 95% confidence interval, 1.91-65.63) and cancer-specific survival (hazard ratio, 15.93; 95% confidence interval, 3.09-82.16). The current investigation was limited by its retrospective design, single-center experience, and a lack of confirmatory protein analyses.

CONCLUSIONS

Loss of chromosome 3p (the VHL gene) was associated with improved survival in patients with ccRCC, whereas loss of chromosome 14q (the HIF-1α gene) was associated with worse outcomes. The results of the current study support the hypothesis that HIF-1α functions as an important tumor suppressor gene in ccRCC.

Differential transcriptomic analysis of spontaneous lung tumors in B6C3F1 mice: comparison to human non-small cell lung cancer

Lung cancer is the leading cause of cancer-related death in people and is mainly due to environmental factors such as smoking and radon. The National Toxicology Program (NTP) tests various chemicals and mixtures for their carcinogenic hazard potential. In the NTP chronic bioassay using B6C3F1 mice, the incidence of lung tumors in treated and control animals is second only to the liver tumors. In order to study the molecular mechanisms of chemically induced lung tumors, an understanding of the genetic changes that occur in spontaneous lung (SL) tumors from untreated control animals is needed. The authors have evaluated the differential transcriptomic changes within SL tumors compared to normal lungs from untreated age-matched animals. Within SL tumors, several canonical pathways associated with cancer (eukaryotic initiation factor 2 signaling, RhoA signaling, PTEN signaling, and mammalian target of rapamycin signaling), metabolism (Inositol phosphate metabolism, mitochondrial dysfunction, and purine and pyramidine metabolism), and immune responses (FcγR-mediated phagocytosis, clathrin-mediated endocytosis, interleukin 8 signaling, and CXCR4 signaling) were altered. Meta-analysis of murine SL tumors and human non-small cell lung cancer transcriptomic data sets revealed a high concordance. These data provide important information on the differential transcriptomic changes in murine SL tumors that will be critical to our understanding of chemically induced lung tumors and will aid in hazard analysis in the NTP 2-year carcinogenicity bioassays.

Gain of chromosome 8q is associated with metastases and poor survival of patients with clear cell renal cell carcinoma

BACKGROUND

The aim of this study was to evaluate the prevalence of chromosome 8q gain in clear cell renal cell carcinoma (CCRCC) and to correlate the findings with tumor phenotype and disease-specific survival (DSS).

METHODS

The tumor karyotypes of 336 consecutive patients with CCRCC were prospectively evaluated with classical cytogenetic analysis. Chromosome 8q status was correlated with clinicopathological variables, and its impact on DSS was evaluated.

RESULTS

Gain of 8q occurred in 28 tumors (8.3%). Gain of 8q was associated with a higher risk of regional lymph node (21.4% vs 6.2%, P = .011) and distant metastases (50.0% vs 24.4%, P = .006), and greater tumor sizes (P = .030). Patients with gain of 8q had a 3.22-fold increased risk of death from CCRCC (P < .001). In multivariable analysis, gain of 8q was identified as an independent prognostic factor (hazard ratio, 2.37; P = .006). The concordance index of a multivariable base model increased significantly following inclusion of 8q gain (P = .0015).

CONCLUSIONS

Gain of chromosome 8q occurs in a subset of CCRCCs and is associated with an increased risk of metastases and death from CCRCC. Because the proto-oncogene c-MYC is among the list of candidate genes located on 8q, our data suggest that these tumors may have unique pathways activated, which are associated with an aggressive tumor phenotype. If confirmed, defining tumors with gain of 8q may assist in identifying patients who would benefit for specific c-MYC inhibitors or agents that target the MAPK/ERK (mitogen-activated protein kinase) pathway.

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.

On translational regulation and EMT

Translational regulation is increasingly recognized as a critical mediator of gene expression. It endows cells with the ability to decide when a particular protein is expressed, thereby ensuring proper and prompt cellular responses to environmental cues. This ability to reprogram protein synthesis and to permit the translation of the respective regulatory messages is particularly important in complex changing environments, including embryonic development, wound healing and environmental stress. Not surprisingly, mistakes in this process can lead to cancer. This review will focus on the mechanisms of translational control operating in normal and cancer cells. We discuss the possibility that progression of primary epithelial tumors into a motile mesenchymal-like phenotype during the invasive phase of metastasis is driven, in part, by a switch from cap-dependent to cap-independent translation.

The translation factor eIF6 is a Notch-dependent regulator of cell migration and invasion

A growing body of evidence indicates that protein factors controlling translation play an important role in tumorigenesis. The protein known as eIF6 is a ribosome anti-association factor that has been implicated in translational initiation and in ribosome synthesis. Over-expression of eIF6 is observed in many natural tumours, and causes developmental and differentiation defects in certain animal models. Here we show that the transcription of the gene encoding eIF6 is modulated by the receptor Notch-1, a protein involved in embryonic development and cell differentiation, as well as in many neoplasms. Inhibition of Notch-1 signalling by γ-secretase inhibitors slowed down cell-cycle progression and reduced the amount of eIF6 in lymphoblastoid and ovarian cancer cell lines. Cultured ovarian cancer cell lines engineered to stably over-expressing eIF6 did not show significant changes in proliferation rate, but displayed an enhanced motility and invasive capacity. Inhibition of Notch-1 signalling in the cells over-expressing eIF6 was effective in slowing down the cell cycle, but did not reduce cell migration and invasion. On the whole, the results suggest that eIF6 is one of the downstream effectors of Notch-1 in the pathway that controls cell motility and invasiveness.

Current development of the second generation of mTOR inhibitors as anticancer agents

The mammalian target of rapamycin (mTOR), a serine/threonine protein kinase, acts as a “master switch” for cellular anabolic and catabolic processes, regulating the rate of cell growth and proliferation. Dysregulation of the mTOR signaling pathway occurs frequently in a variety of human tumors, and thus, mTOR has emerged as an important target for the design of anticancer agents. mTOR is found in two distinct multiprotein complexes within cells, mTORC1 and mTORC2. These two complexes consist of unique mTOR-interacting proteins and are regulated by different mechanisms. Enormous advances have been made in the development of drugs known as mTOR inhibitors. Rapamycin, the first defined inhibitor of mTOR, showed effectiveness as an anticancer agent in various preclinical models. Rapamycin analogues (rapalogs) with better pharmacologic properties have been developed. However, the clinical success of rapalogs has been limited to a few types of cancer. The discovery that mTORC2 directly phosphorylates Akt, an important survival kinase, adds new insight into the role of mTORC2 in cancer. This novel finding prompted efforts to develop the second generation of mTOR inhibitors that are able to target both mTORC1 and mTORC2. Here, we review the recent advances in the mTOR field and focus specifically on the current development of the second generation of mTOR inhibitors as anticancer agents.

Targeting translation dependence in cancer

A challenge in cancer therapy is to selectively target activities that are essential for survival of malignant cells while sparing normal cells. Translational control represents a potential anti-neoplastic target because it is exerted by major signaling pathways that are often usurped in cancers. Herein we describe approaches being developed that target eukaryotic initiation factor (eIF) 4F, a heterotrimeric complex that integrates multiple signaling inputs to the translation apparatus.

The targets of curcumin

Curcumin (diferuloylmethane), an orange-yellow component of turmeric or curry powder, is a polyphenol natural product isolated from the rhizome of the plant Curcuma longa. For centuries, curcumin has been used in some medicinal preparation or used as a food-coloring agent. In recent years, extensive in vitro and in vivo studies suggested curcumin has anticancer, antiviral, antiarthritic, anti-amyloid, antioxidant, and anti-inflammatory properties. The underlying mechanisms of these effects are diverse and appear to involve the regulation of various molecular targets, including transcription factors (such as nuclear factor-kB), growth factors (such as vascular endothelial cell growth factor), inflammatory cytokines (such as tumor necrosis factor, interleukin 1 and interleukin 6), protein kinases (such as mammalian target of rapamycin, mitogen-activated protein kinases, and Akt) and other enzymes (such as cyclooxygenase 2 and 5 lipoxygenase). Thus, due to its efficacy and regulation of multiple targets, as well as its safety for human use, curcumin has received considerable interest as a potential therapeutic agent for the prevention and/or treatment of various malignant diseases, arthritis, allergies, Alzheimer's disease, and other inflammatory illnesses. This review summarizes various in vitro and in vivo pharmacological aspects of curcumin as well as the underlying action mechanisms. The recently identified molecular targets and signaling pathways modulated by curcumin are also discussed here.

Interrelationships between tumor proliferative activity, leucocyte and macrophage infiltration, systemic inflammatory response, and survival in patients selected for potentially curative resection for gastroesophageal cancer

BACKGROUND

A number of accepted criteria, including pathological tumor, node, metastasis system stage, lymph node metastasis, and tumor differentiation, predict survival in patients undergoing surgery for gastroesophageal cancer. We examined the interrelationships between standard clinicopathological factors, systemic and local inflammatory responses, tumor proliferative activity, and survival.

METHODS

The interrelationships between the systemic inflammatory response (Glasgow prognostic score, mGPS), standard clinicopathological factors, local inflammatory response (Klintrup criteria, macrophage infiltration), and tumor proliferative activity (Ki-67) were examined by immunohistochemistry in 100 patients (44 esophageal [19 squamous, 25 adenocarcinoma], 19 junctional, and 37 gastric cancers) selected for potentially curative resection.

RESULTS

The minimum follow-up was 59 months. On multivariate survival analysis, lymph node ratio (hazard ratio [HR] 1.63, 95% confidence interval [CI] 1.11-2.40, P < 0.05), tumor differentiation (HR 2.63, 95% CI 1.45-4.77, P = 0.001), mGPS (HR 3.91, 95% CI 1.96-8.11, P < 0.001), Klintrup score (HR 3.47, 95% CI 1.14-10.55, P < 0.05), and Ki-67 (HR 0.67, 95% CI 0.47-0.96, P < 0.05) were independently associated with cancer-specific survival. A higher lymph node ratio was associated with poor tumor differentiation (P < 0.05), low-grade Klintrup criteria (P < 0.005), and low tumor proliferative activity (P < 0.05).

CONCLUSION

Tumor proliferation rate and local and systemic inflammatory responses are important predictors of survival, albeit in a heterogeneous cohort of patients including esophageal, junctional, and gastric cancers. These scores may be combined with accepted tumor-based factors to improve prediction of outcome.

The complexes of mammalian target of rapamycin

The mammalian target of rapamycin (mTOR) has attracted substantial attention because of its involvement in a variety of diseases, such as cancer, cardiac hypertrophy, diabetes and obesity. Current knowledge indicates that mTOR functions as two distinct multiprotein complexes, mTORC1 and mTORC2. mTORC1 phosphorylates p70 S6 kinase (S6K1) and eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1), and regulates cell growth, proliferation, and survival by integrating hormones, growth factors, nutrients, stressors and energy signals. In contrast, mTORC2 is insensitive to nutrients or energy conditions. However, in response to hormones or growth factors, mTORC2 phosphorylates Akt, and regulates actin cytoskeleton and cell survival. These findings not only reveal the crucial role of mTOR in physiology and pathology, but also reflect the complexity of the mTOR signaling network. In this review, we discuss the advances in studies of the mTOR complexes, including the interacting proteins, the upstream regulators and the downstream effectors of mTOR complexes, as well as their implication in certain human diseases.

Exploiting human herpesvirus immune evasion for therapeutic gain: potential and pitfalls

Herpesviruses stand out for their capacity to establish lifelong infections of immunocompetent hosts, generally without causing overt symptoms. Herpesviruses are equipped with sophisticated immune evasion strategies, allowing these viruses to persist for life despite the presence of a strong antiviral immune response. Although viral evasion tactics appear to target virtually any stage of the innate and adaptive host immune response, detailed knowledge is now available on the molecular mechanisms underlying herpesvirus obstruction of MHC class I-restricted antigen presentation to T cells. This opens the way for clinical application. Here, we review and discuss recent efforts to exploit human herpesvirus MHC class I evasion strategies for the rational design of novel strategies for vaccine development, cancer treatment, transplant protection and gene therapy.

Updates of mTOR inhibitors

Mammalian target of rapamycin (mTOR) is a central controller of cell growth, proliferation, metabolism and angiogenesis. mTOR signaling is often dysregulated in various human diseases and thus attracts great interest in developing drugs that target mTOR. Currently it is known that mTOR functions as two complexes, mTOR complex 1/2 (mTORC1/2). Rapamycin and its analogs (all termed rapalogs) first form a complex with the intracellular receptor FK506 binding protein 12 (FKBP12) and then bind a domain separated from the catalytic site of mTOR, blocking mTOR function. Rapalogs are selective for mTORC1 and effective as anticancer agents in various preclinical models. In clinical trials, rapalogs have demonstrated efficacy against certain types of cancer. Recently, a new generation of mTOR inhibitors, which compete with ATP in the catalytic site of mTOR and inhibit both mTORC1 and mTORC2 with a high degree of selectivity, have been developed. Besides, some natural products, such as epigallocatechin gallate (EGCG), caffeine, curcumin and resveratrol, have been found to inhibit mTOR as well. Here, we summarize the current findings regarding mTOR signaling pathway and review the updated data about mTOR inhibitors as anticancer agents.

Clinical pathological significance of mTOR and Cyclin D1 protein expression in esophageal squamous cell carcinoma

AIM: To explore the relationship of mammalian target of rapamycin (mTOR) and Cyclin D1 protein expression with the development, progression, invasion, and metastasis of esophageal squamous cell carcinoma.

METHODS: The expression of mTOR and Cyclin D1 proteins in 62 esophageal squamous cell carcinoma specimens and 56 normal esophageal epithelial tissue specimens was detected by immunohistochemistry using the streptaridin-peroxidase method.

RESULTS: The positive rates of mTOR and Cyclin D1 protein expression in esophageal squamous cell carcinoma were significantly higher than those in normal esophageal epithelium (53.2% vs 30.4% and 77.4% vs 12.3%; χ² = 5.400 and 48.106; both P < 0.05). The positive rate of mTOR protein expression is closely correlated with tumor histological grade in esophageal squamous cell carcinoma (χ² = 3.960, P < 0.05). There is a positive correlation between the expression of mTOR and Cyclin D1 proteins (g_p = 0.344, P < 0.05).

CONCLUSION: Both mTOR and Cyclin D1 play an important role in the invasion, metastasis and mucosal epithelial canceration of esophageal squamous cell carcinoma. Combined detection of mTOR and Cyclin D1 expression is a promising molecular parameter for early diagnosis and prognostic evaluation of esophageal squamous cell carcinoma.

Emerging role for the cytoskeleton as an organizer and regulator of translation

The cytoskeleton is an intricate and dynamic fibrous network that has an essential role in the generation and regulation of cell architecture and cellular mechanical properties. The cytoskeleton also evolved as a scaffold that supports diverse biochemical pathways. Recent evidence favours the hypothesis that the cytoskeleton participates in the spatial organization and regulation of translation, at both the global and local level, in a manner that is crucial for cellular growth, proliferation and function.

Inhibition of eIF2alpha dephosphorylation inhibits ErbB2-induced deregulation of mammary acinar morphogenesis

BACKGROUND

The ErbB2/Her2/Neu receptor tyrosine kinase is amplified in approximately 30% of human breast cancers. Phosphorylation of the translation initiation factor, eIF2alpha inhibits global protein synthesis and activates a stress signaling and growth suppressive program. We have shown that forced phosphorylation of eIF2alpha can suppress head and neck, colorectal carcinoma and multiple myeloma tumor growth and/or survival. Here we explore whether ErbB2 modulates eIF2alpha phosphorylation and whether forced phosphorylation of the latter can antagonize ErbB2 deregulation of mammary acinar morphogenesis.

RESULTS

We tested whether ErbB2 signaling influenced eIF2alpha signaling and whether enhanced phosphorylation of the latter affected ErbB2-deregulated mammary acinar development. We obtained stable MCF10A cells overexpressing wild-type (Wt) Neu/ErbB2 or a constitutively active (CA) variant via retroviral delivery or mammary tumor cells from MMTV-Neu tumors. Western blotting, RT-PCR and confocal microscopy were used to analyze the effects of ErbB2 activation on eIF2alpha signaling and the effect of the GADD34-PP1C inhibitor salubrinal. Wt- and MMTV-Neu cells formed aberrant acini structures resembling DCIS, while CA-ErbB2 overexpression induced invasive lesions. In these structures we found that CA-ErbB2 but not the Wt variant significantly down-regulated the pro-apoptotic gene CHOP. This occurred without apparent modulation of basal phosphorylation of PERK and eIF2alpha or induction of its downstream target ATF4. However, inhibition of eIF2alpha dephosphorylation with salubrinal was sufficient to inhibit Wt- and CA-ErbB2- as well as MMTV-Neu-induced deregulation of acinar growth. This was linked to enhanced CHOP expression, inhibition of proliferation, induction of apoptosis and luminal clearing in Wt-ErbB2 and to inhibition of cyclin D1 levels and subsequent proliferation in CA-ErbB2 cells.

CONCLUSION

Depending on the strength of ErbB2 signaling there is a differential regulation of CHOP and eIF2alpha phosphorylation. ErbB2 uncouples in basal conditions eIF2alpha phosphorylation from CHOP induction. However, this signal was restored by salubrinal treatment in Wt-ErbB2 expressing MCF10A cells as these DCIS-like structures underwent luminal clearing. In CA-ErbB2 structures apoptosis is not induced by salubrinal and instead a state of quiescence with reduced proliferation was achieved. Treatments that stabilize P-eIF2alpha levels may be effective in treating ErbB2 positive cancers without severely disrupting normal tissue function and structure.