Differential Regulation of the Melanoma Proteome by eIF4A1 and eIF4E

Chemical Probes for Studying the Eukaryotic Translation Initiation Factor 4E (eIF4E)-Regulated Translatome in Cancer

The dysregulation of translation is a hallmark of cancer that enables rapid changes in the cell proteome to shape oncogenic phenotypes that promote tumor survival. The predominant signaling pathways leading to dysregulation of translational control in cancer are the PI3K-AKT-mTORC1, RAS-RAF-MAPK, and MYC pathways, which all converge on eukaryotic translation initiation factor 4E (eIF4E), an RNA-binding protein that binds to the m7GpppX cap structure at the 5' end of mRNAs to initiate cap-dependent translation. eIF4E is the rate-limiting factor of translation initiation, and its overexpression is known to drive oncogenic transformation, progression, and chemoresistance across many cancers, establishing it as an attractive therapeutic target. Over the last several decades, significant efforts have been made to inhibit eIF4E through the development of mechanistically distinct small-molecule inhibitors that both directly and indirectly act on eIF4E to prevent cap-dependent translation initiation. These inhibitors can serve as powerful chemical tools to improve our understanding of the mechanisms of cap-dependent translation in cancer and to ultimately predict specific cancers that may benefit from eIF4E-targeted therapeutics. This review discusses the progress made in the development of different classes of small-molecule eIF4E inhibitors, the challenges that remain, and their potential as chemical probes to elucidate the complexities of cap-dependent translation in cancer.

Unraveling the role of PBK in glioblastoma: from molecular mechanisms to therapeutic targets

BACKGROUND

This study investigates the gene expression characteristics of glioma-initiating cells (GIC), an important subgroup of glioblastoma (GBM), after knockdown of PBK (PDZ-binding kinase). Differentially expressed genes (DEGs) between PBK knockdown GIC and control groups were screened through bioinformatics methods. The authors analyzed the mechanisms and roles of these DEGs in GBM tumorigenesis and patient prognosis.

METHODS

Microarray data (GSE53800) were obtained from the Gene Expression Omnibus (GEO) database, selecting 18 GIC cell line samples with or without PBK knockdown. Each control and knockdown group contained three samples. DEGs were screened using R software. GO enrichment analysis, KEGG pathway analysis, PPI network analysis, and hub gene identification were conducted to explore DEG mechanisms. Western blot analysis was also performed to detect EIF4E protein expression, one of the key hub genes, after PBK knockdown in the HS683 glioma cell line.

RESULTS

A total of 175 upregulated and 145 downregulated genes were identified. GO analysis showed that DEGs were mainly enriched in the positive regulation of cell proliferation, cell adhesion, and angiogenesis. KEGG pathway analysis revealed that DEGs were mainly involved in neuroactive ligand-receptor interactions, calcium signaling, and HIF-1 signaling pathways. Western blot results indicated that EIF4E was downregulated after PBK knockdown.

CONCLUSION

A group of genes, such as EIF4E, were closely associated with PBK expression and functions. These findings may provide insight into the molecular mechanism of PBK in GBM.

Targeting eIF4G1-dependent translation in melanoma

Elevated expression of components of eIF4F translation initiation complex has been documented in cancer, resulting in enhanced translation of mRNAs encoding pro-tumorigenic factors, including oncogenic proteins. We previously identified SBI-756, a small molecule that interferes with the eIF4F assembly and overcomes melanoma resistance to BRAF inhibitors. SBI-756 enhanced anti-tumor immunity in pancreatic cancer and was effective in the treatment of diffuse large B cell lymphoma. Here, we identified the eIF4G1 MA3 (4G1-MA3) domain as the target of SBI-756, attenuating eIF4F complex assembly. Melanoma cells expressing a mutant form of 4G1-MA3 exhibited polysome profiles resembling those of melanoma cells treated with SBI-756. A structure-based in silico screen against the eIF4G1 MA3 domain identified M19, a small molecule inhibitor that exhibited anti-melanoma effects. RNA sequencing (RNA-seq) revealed upregulation of UPR, mTOR, p53, and ROS signaling in M19-treated melanoma cells. Ribosome sequencing identified changes in ribosomal structure and electron transport chain components following M19-6 treatment of melanoma cells. Autophagy and histone deacetylase inhibitors were found to enhance anti-neoplastic activities of M19 or its analog, M19-6. M19-6 conferred a greater effect on melanoma than melanocytes and overcame melanoma resistance to BRAF or MEK inhibitors. Alone, M19-6 reduced melanoma growth and metastasis in a xenograft model. M19-6 offers a new therapeutic modality to overcome resistance and metastasis.

Integration approach of transcriptomics and metabolomics reveals the toxicity of Anthracene and its chlorinated derivatives on human hepatic cells

Polycyclic aromatic hydrocarbons (PAHs) and Chlorinated PAHs (Cl-PAHs) are ubiquitous environmental contaminants. The toxicological information of anthracene (Ant) and its chlorinated derivatives is quite limited. In this study, an integrated metabolomic and transcriptomic analysis approach was adopted to assess the toxic effects triggered by Ant and its chlorinated derivatives, 2-chloroanthracene (2-ClAnt) and 9,10-dichloroanthracen (9,10-Cl2Ant), at human-relevant levels on human normal hepatocyte L02 cells. The cell viability test showed no significant effects on the viability of L02 cells exposed to Ant, 2-ClAnt and 9,10-Cl2Ant at doses of 5-500 nM for 24 h. However, based on transcriptomic analysis, Ant, 2-ClAnt and 9,10-Cl2Ant exposure at human-relevant levels obviously perturbed global gene expression in L02 cells and induced the differential expression of several genes related to cancer development. As the number of genes related to cancer development altered by 9,10-Cl2Ant is the largest, 9,10-Cl2Ant posed greater risks of tumor development than Ant and 2-ClAnt did. Metabolomics analysis demonstrated that Ant, 2-ClAnt and 9,10-Cl2Ant caused significant metabolic perturbation in L02 cells. Pathway enrichment analysis indicated that Ant, 2-ClAnt and 9,10-Cl2Ant mainly perturbed the lipid metabolism and nucleotide metabolism pathway. However, 9,10-Cl2Ant caused a wider perturbation to metabolic pathways than Ant and 2-ClAnt did. In addition, dysregulation of nucleotide metabolism perturbed by Ant, 2-ClAnt and 9,10-Cl2Ant may be associated with the genomic instability and further carcinogenesis.

Translational regulation of cell invasion through extracellular matrix-an emerging role for ribosomes

Many developmental and physiological processes require cells to invade and migrate through extracellular matrix barriers. This specialized cellular behavior is also misregulated in many diseases, such as immune disorders and cancer. Cell invasive activity is driven by pro-invasive transcriptional networks that activate the expression of genes encoding numerous different proteins that expand and regulate the cytoskeleton, endomembrane system, cell adhesion, signaling pathways, and metabolic networks. While detailed mechanistic studies have uncovered crucial insights into pro-invasive transcriptional networks and the distinct cell biological attributes of invasive cells, less is known about how invasive cells modulate mRNA translation to meet the robust, dynamic, and unique protein production needs of cell invasion. In this review we outline known modes of translation regulation promoting cell invasion and focus on recent studies revealing elegant mechanisms that expand ribosome biogenesis within invasive cells to meet the increased protein production requirements to invade and migrate through extracellular matrix barriers.

Eukaryotic translation initiation factor 4A1 in the pathogenesis and treatment of cancers

Abnormal translate regulation is an important phenomenon in cancer initiation and progression. Eukaryotic translation initiation factor 4A1 (eIF4A1) protein is an ATP-dependent Ribonucleic Acid (RNA) helicase, which is essential for translation and has bidirectional RNA unwinders function. In this review, we discuss the levels of expression, regulatory mechanisms and protein functions of eIF4A1 in different human tumors. eIF4A1 is often involved as a target of microRNAs or long non-coding RNAs during the epithelial-mesenchymal transition, associating with the proliferation and metastasis of tumor cells. eIF4A1 protein exhibits the promising biomarker for rapid diagnosis of pre-cancer lesions, histological phenotypes, clinical staging diagnosis and outcome prediction, which provides a novel strategy for precise medical care and target therapy for patients with tumors at the same time, relevant small molecule inhibitors have also been applied in clinical practice, providing reliable theoretical support and clinical basis for the development of this gene target.

High expression of eIF4A1 predicts unfavorable prognosis in clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is a worldwide malignancy with high morbidity and mortality. Translation initiation factor 4A1 (eIF4A1), which is an ATP-dependent RNA helicase as a part of eIF4F complex, has been linked to malignant transformation and progression, and a variety of cancers display dysregulation of this enzyme. However, its role in ccRCC remains unclear. In our study, we examined its potential effects in ccRCC.

METHODS

Based on Proteomic data, TCGA and ONCOMINE database, RCC cell lines and tissues, the expression of eIF4A1 between ccRCC and normal tissues were investigated. A correlation was evaluated between the prognostic model for OS and ccRCC progression. Analysis of functional enrichment and PPI network were performed. After examining differentially expressed genes between the eIF4A1 high and low-expression groups, we performed GSEA analysis. Furthermore, we investigated immune cell infiltration of eIF4A1. Then we determined eIF4A1 functions in the establishment and maintenance of cell viability, migration and invasion of cell lines. Flow cytometry was utilized to detect cell cycle.

RESULTS

The eIF4A1 was up-regulated in ccRCC tissues and cell lines. An increased level of eIF4A1 was linked to lower survival rates and impaired immunity. Depletion of eIF4A1 could arrest tumor cells in G1 phase, so as to seriously limit cell proliferation and weaken the capacity of cell migration.

CONCLUSION

ccRCC patients with high eIF4A1 expression are at increased risk of poor prognosis, furthermore eIF4A1 plays a prominent role in facilitating tumor cell proliferation and migration which may further be a potential prognostic biomarker and therapeutic target.

Astragaloside IV exhibits anti-tumor function in gastric cancer via targeting circRNA dihydrolipoamide S-succinyltransferase (circDLST)/miR-489-3p/ eukaryotic translation initiation factor 4A1(EIF4A1) pathway

Astragaloside IV (AS-IV) is an inartificial saponin separated from astragalus membranaceus, which has exhibited key anti-tumor regulation in some cancers. Circular RNAs (circRNAs) are important regulators in malignant development of gastric cancer (GC). Herein, we focused on the molecular mechanism of AS-IV with circRNA dihydrolipoamide S-succinyltransferase (circDLST) in GC. CircDLST, microRNA-489-3p (miR-489-3p), and eukaryotic translation initiation factor 4A1 (EIF4A1) levels were detected by quantitative real-time polymerase-chain reaction and western blot. Cell functions were assessed by cell counting kit-8 assay, ethynyl-2’-deoxyuridine assay, colony formation assay, and transwell assay. The interaction between miR-489-3p and circDLST or EIF4A1 was analyzed by dual-luciferase reporter assay. Xenograft tumor assay was adopted to check the role of circDLST and AS-IV in vivo. CircDLST and EIF4A1 were upregulated but miR-489-3p was downregulated in GC cells. AS-IV restrained cell proliferation and metastasis in GC cells by downregulating circDLST. CircDLST served as a miR-489-3p sponge, and miR-489-3p inhibition reversed anti-tumor function of AS-IV. EIF4A1 was a target for miR-489-3p and circDLST sponged miR-489-3p to regulate EIF4A1. AS-IV suppressed GC cell progression via circDLST-mediated downregulation of EIF4A1. Also, AS-IV recued tumor growth in vivo via targeting circDLST to regulate miR-489-3p/EIF4A1 axis. AS-IV inhibited the development of GC through circDLST/miR-489-3p/EIF4A1 axis.

Pre-mRNA processing factor 19 functions in DNA damage repair and radioresistance by modulating cyclin D1 in hepatocellular carcinoma

Pre-mRNA processing factor 19 (PRP19) is elevated in hepatocellular carcinoma (HCC); however, little is known about its function in DNA damage repair in HCC. In this study, analysis of The Cancer Genome Atlas data and our tumor models after ionizing radiation (IR) treatment indicated that increased expression of PRP19 was positively correlated with DNA damage repair. Gain of PRP19 expression induced by plasmids resulted in decreases in apoptosis and double-strand breaks (DSBs), and an increase in cell survival after IR. Loss of PRP19 expression induced by small interfering RNAs resulted in the accumulation of apoptosis and DSBs, and a decrease in cell survival. Mechanistically, the effect of PRP19 on DNA damage repair was mediated by the modulation of cyclin D1 expression in HCC. PRP19 controlled the translation of cyclin D1 by modulating eukaryotic initiation factor 4E. PRP19 affected the DNA damage repair ability of cyclin D1 by interacting with the WD40 domain. The combination of PRP19 and cyclin D1 was more valuable than each single marker for predicting the prognosis of patients. Taken together, the present results demonstrate that PRP19 promotes DNA damage repair by modulating cyclin D1 expression and function, thereby contributing to the radioresistance in HCC.

Expression and Functional Roles of Eukaryotic Initiation Factor 4A Family Proteins in Human Cancers

The dysregulation of mRNA translation is common in malignancies and may lead to tumorigenesis and progression. Eukaryotic initiation factor 4A (eIF4A) proteins are essential for translation, exhibit bidirectional RNA helicase function, and act as RNA-dependent ATPases. In this review, we explored the predicted structures of the three eIF4A isoforms (eIF4A1, eIF4A2, and eIF4A3), and discussed possible explanations for which function during different translation stages (initiation, mRNA localization, export, and mRNA splicing). These proteins also frequently served as targets of microRNAs (miRNAs) or long noncoding RNAs (lncRNAs) to mediate epithelial-mesenchymal transition (EMT), which was associated with tumor cell invasion and metastasis. To define the differential expression of eIF4A family members, we applied the Tumor Immune Estimation Resource website. We figured out that the eIF4A family genes were differently expressed in specific cancer types. We also found that the level of the eIF4A family genes were associated with abundant immune cells infiltration and tumor purity. The associations between eIF4A proteins and cancer patient clinicopathological features suggested that eIF4A proteins might serve as biomarkers for early tumor diagnosis, histological classification, and clinical grading/staging, providing new tools for precise and individualized cancer treatment.

Cellular delivery of dinucleotides by conjugation with small molecules: targeting translation initiation for anticancer applications

Targeting cap-dependent translation initiation is one of the experimental approaches that could lead to the development of novel anti-cancer therapies. Synthetic dinucleoside 5',5'-triphosphates cap analogs are potent antagonists of eukaryotic translation initiation factor 4E (eIF4E) in vitro and could counteract elevated levels of eIF4E in cancer cells; however, transformation of these compounds into therapeutic agents remains challenging - they do not easily penetrate into cells and are susceptible to enzymatic cleavage. Here, we tested the potential of several small molecule ligands - folic acid, biotin, glucose, and cholesterol - to deliver both hydrolyzable and cleavage-resistant cap analogs into cells. A broad structure-activity relationship (SAR) study using model fluorescent probes and cap-ligand conjugates showed that cholesterol greatly facilitates uptake of cap analogs without disturbing the interactions with eIF4E. The most potent cholesterol conjugate identified showed apoptosis-mediated cytotoxicity towards cancer cells.

Eukaryotic initiating factor eIF4E is targeted by EBV-encoded miR-BART11-3p and regulates cell cycle and apoptosis in EBV-associated gastric carcinoma

The eukaryotic translation initiation factor 4E (eIF4E) is a component of the eukaryotic translation initiation factor 4F, a significant complex in the protein translation process. It has been found to be closely related to many human tumors, such as gastric carcinoma. It is known that the Epstein-Barr virus (EBV) upregulates eIF4E in various ways in nasopharyngeal carcinoma. However, there are very few studies on eIF4E in EBV-associated gastric carcinoma. We found that the expression level of eIF4E in EBV-associated gastric carcinoma was lower than other types of gastric carcinoma, and the downregulation of eIF4E could lead to increased apoptosis of gastric carcinoma cells, retardation at S phase, and decreased cell migration. The dual luciferase reporter experiment showed that EBV-miR-BART11-3p could directly target the 3'-UTR region of eIF4E, and BART11-3p is the key factor leading to the downregulation of eIF4E. It could provide a new evidence for EBV-regulating host gene to affect the development of gastric carcinoma.

EIF3B promotes cancer progression in pancreatic cancer

BACKGROUND

This study aimed to analyze the relative expression of Eukaryotic Translation Initiation Factor 3 Subunit B (EIF3B) in pancreatic cancer and elucidate its contribution to this disease.

METHODS

Relative expression of EIF3B in pancreatic cancer was analyzed by immunohistochemistry. Cell viability was determined by the MTT assay and cell proliferation was measured by direct cell counting. Cell apoptosis was detected by Annexin V staining followed by flow cytometry analysis, and cell cycle was analyzed by PI staining. The differential expression gene analysis was performed by microarray. Tumor progression in response to EIF3B deficiency in vivo was investigated using the xenograft tumor model.

RESULTS

We found aberrantly high expression of EIF3B in pancreatic cancer, which associated with unfavorable prognosis. Knockdown of EIF3B greatly compromised cell viability and proliferation in both SW1990 and PANC-1 cells. Furthermore, EIF3B deficiency induced cell cycle arrest and spontaneous apoptosis. In vivo tumor progression was significantly suppressed by EIF3B silencing in the xenograft mouse model. Mechanistically, we characterized down-regulation of CDH1 and IRS1 and up-regulation of DDIT3, PTEN and CDKN1B, in response to EIF3B knockdown, which might mediate the oncogenic effect of EIF3B in pancreatic cancer.

CONCLUSIONS

Our data uncovered the oncogenic role of EIF3B in pancreatic cancer.

USP15 Enhances Re-epithelialization Through Deubiquitinating EIF4A1 During Cutaneous Wound Repair

Re-epithelialization is a fundamental process in wound healing that involves various cytokines and cells during cutaneous barrier reconstruction. Ubiquitin-specific peptidase 15 (USP15), an important member of the deubiquitinating enzymes (DUBs), removes ubiquitin chains from target proteins and maintains protein stability. However, the dynamic role of USP15 in epithelialization remains unclear. We aimed to investigate the regulatory function of USP15 in re-epithelialization. An excisional wound splinting model was established to evaluate the re-epithelialization rate in Usp15 knockout (KO) mice. Coimmunoprecipitation (Co-IP) and mass spectrum analyses were performed to identify USP15-interacting proteins. RNA-sequencing was performed for transcriptome analysis in keratinocytes and uploaded into NODE database (http://www.biosino.org/node, accession numbers: OEP000770 and OEP000763). First, a significant delay in epithelialization was observed in the Usp15 KO mice. Moreover, inhibition of cell migration and proliferation was observed in the USP15-silenced keratinocytes (HaCaTs). Moreover, we revealed for the first time that USP15 could interact with eukaryotic initiation factor 4A-1 (EIF4A1), thereby promoting translational efficacy in keratinocytes, which is essential for keratinocyte proliferation and migration. Conclusively, the USP15-EIF4A1 complex significantly accelerated re-epithelialization in wound healing. These observations helped elucidate the function and mechanisms of USP15 in modulating re-epithelialization in wound healing, providing a promising target for refractory wound treatment.

Eukaryotic translation initiation factor 3 subunit b is a novel oncogenic factor in prostate cancer

Prostate cancer, the second most common cancer among male adults, affects millions globally. We sought to investigate the expression and contribution of Eukaryotic translation initiation factor 3 subunit b (EIF3B) in prostate cancer. Expression of EIF3B was analyzed in both human prostate patient tissues and prostate cancer cell lines. Small interfering RNA (siRNA) knockdown of EIF3B was introduced into prostate cancer cell line PC-3 and LNCaP, followed by examination of cell viability, proliferation and apoptosis using the MTT, cell counting and terminal deoxynucleotidyl transferase dUTP nick end labeling assays, respectively. An in vivo xenograft tumor mouse model was employed to address the role of EIF3B in tumorigenesis as well. Finally, a gene microarray analysis was performed to search for differentially expressed genes upon EIF3B knockdown. EIF3B was upregulated in prostate tumor tissues and prostate cancer cell lines. EIF3B knockdown inhibited viability and proliferation of prostate cancer cells, as well as promoted cell apoptosis. In the in vivo mouse model, inoculation of EIF3B knockdown PC-3 cells displayed inhibited growth of xenograft tumors. In addition, potential signaling pathways that might be involved in EIF3B action in prostate cancer were identified by the gene microarray. EIF3B is a novel oncogenic factor in prostate cancer both in vitro and in vivo, which could be employed as a novel therapeutic target in the treatment against prostate cancer.

Cinobufagin Triggers Defects in Spindle Formation and Cap-Dependent Translation in Liver Cancer Cells by Inhibiting the AURKA-mTOR-eIF4E Axis

Cinobufagin is a Na+/K+-ATPase (NKA) inhibitor with excellent anticancer effects to prolong the survival of patients. The purpose of the present study was to clarify the underlying mechanism of the anticancer effects of cinobufagin using overexpression or inhibition of aurora kinase A (AURKA) signaling. First, high expression of Na+/K+-ATPase alpha 1 subunit (ATP1A1) and AURAK resulted in increased malignant transformation in hepatocellular carcinoma (HCC) patients using the cancer genome atlas (TCGA) data and tissue samples. After treatment with cinobufagin, we successfully screened 202, 249, and 335 changing expression proteins in Huh-7 cells under normal, overexpression, and inhibition of AURKA using tandem mass tags (TMT)-labeled quantitative proteomics coupled to 2D liquid chromatography-tandem mass spectrometry (LC-MS/MS). Bioinformatics analysis revealed that these molecules were closely associated with chromosome segregation, DNA damage, and regulation of translation processes. We further confirmed that cinobufagin induced DNA damage and chromosome segregation disorders and suppresses translational processing in oncogenes by decreasing the expression of AURKA, mechanistic target of rapamycin kinase (mTOR), p-mTOR, p-extracellular regulated protein kinases (ERK), eukaryotic translation initiation factor 4E (eIF4E), and p-eIF4E, while increasing the expression of p-eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) (S65, T37, T46, T45) and increasing the interaction between eIF4 and 4E-BP1. Our results suggested that cinobufagin performed an antitumor effects in liver cancer cells by inhibiting the AURKA-mTOR-eIF4E axis.

Novel AU-rich proximal UTR sequences (APS) enhance CXCL8 synthesis upon the induction of rpS6 phosphorylation

The role of ribosomal protein S6 (rpS6) phosphorylation in mRNA translation remains poorly understood. Here, we reveal a potential role in modulating the translation rate of chemokine (C-X-C motif) ligand 8 (CXCL8 or Interleukin 8, IL8). We observed that more CXCL8 protein was being secreted from less CXCL8 mRNA in primary macrophages and macrophage-like HL-60 cells relative to other cell types. This correlated with an increase in CXCL8 polyribosome association, suggesting an increase in the rate of CXCL8 translation in macrophages. The cell type-specific expression levels were replicated by a CXCL8- UTR-reporter (Nanoluc reporter flanked by the 5' and 3' UTR of CXCL8). Mutations of the CXCL8-UTR-reporter revealed that cell type-specific expression required: 1) a 3' UTR of at least three hundred bases; and 2) an AU base content that exceeds fifty percent in the first hundred bases of the 3' UTR immediately after the stop codon, which we dub AU-rich proximal UTR sequences (APS). The 5' UTR of CXCL8 enhanced expression at the protein level and conferred cell type-specific expression when paired with a 3' UTR. A search for other APS-positive mRNAs uncovered TNF alpha induced protein 6 (TNFAIP6), another mRNA that was translationally upregulated in macrophages. The elevated translation of APS-positive mRNAs in macrophages coincided with elevated rpS6 S235/236 phosphorylation. Both were attenuated by the ERK1/2 signaling inhibitors, U0126 and AZD6244. In A549 cells, rpS6 S235/236 phosphorylation was induced by TAK1, Akt or PKA signaling. This enhanced the translation of the CXCL8-UTR-reporters. Thus, we propose that the induction of rpS6 S235/236 phosphorylation enhances the translation of mRNAs that contain APS motifs, such as CXCL8 and TNFAIP6. This may contribute to the role of macrophages as the primary producer of CXCL8, a cytokine that is essential for immune cell recruitment and activation.

Translation regulation in skin cancer from a tRNA point of view

Protein synthesis is a central and dynamic process, frequently deregulated in cancer through aberrant activation or expression of translation initiation factors and tRNAs. The discovery of tRNA-derived fragments, a new class of abundant and, in some cases stress-induced, small Noncoding RNAs has perplexed the epigenomics landscape and highlights the emerging regulatory role of tRNAs in translation and beyond. Skin is the biggest organ in human body, which maintains homeostasis of its multilayers through regulatory networks that induce translational reprogramming, and modulate tRNA transcription, modification and fragmentation, in response to various stress signals, like UV irradiation. In this review, we summarize recent knowledge on the role of translation regulation and tRNA biology in the alarming prevalence of skin cancer.

A meta-analysis of transcriptome datasets characterizes malignant transformation from melanocytes and nevi to melanoma

Melanoma represents one of the most aggressive malignancies and has a high tendency to metastasize. The present study aims to investigate the molecular mechanisms of two pathways to cancer transformation with the purpose of identifying potential biomarkers. Our approach is based on a meta-analysis of gene expression profiling contrasting two scenarios: A model that describes a transformation pathway from melanocyte to melanoma and a second model where transformation occurs through an intermediary nevus. Data consists of three independent, publicly available microarray datasets from the Gene Expression Omnibus (GEO) database comprising samples from melanocytes, nevi and melanoma. The present analysis identified 808 differentially expressed genes (528 upregulated and 360 downregulated) in melanoma compared with nevi, and 2,331 differentially expressed genes (946 upregulated and 1,385 downregulated) in melanoma compared with melanocytes. Further analysis narrowed down this list, since 682 differentially expressed genes were found in both models (417 upregulated and 265 downregulated). Enrichment analysis identified relevant dysregulated pathways. This article also presented a discussion on significant genes including ADAM like decysin 1, neudesin neurotrophic factor, MMP19, apolipoprotein L6, C-X-C motif chemokine ligand (CXCL)8, basic, immunoglobulin-like variable motif containing and CXCL16. These are of particular interest because they encode secreted proteins hence represent potential blood biomarkers for the early detection of malignant transformation in both scenarios. Cytotoxic T-lymphocyte associated protein 4, an important therapeutic target in melanoma treatment, was also upregulated in both comparisons indicating a potential involvement in immune tolerance, not only at advanced stages but also during the early transformation to melanoma. The results of the present study may provide a research direction for studying the mechanisms underlying the development of melanoma, depending on its origin.

Invasive lobular and ductal breast carcinoma differ in immune response, protein translation efficiency and metabolism

Invasive lobular carcinoma (ILC) is the second most common histological subtype of breast cancer following invasive ductal carcinoma (IDC). ILC differs from IDC in a number of histological and clinical features, such as single strand growth, difficulty in detection, and frequent late recurrences. To understand the molecular pathways involved in the clinical characteristics of ILC, we compared the gene expression profiles of luminal A ILC and luminal A IDC using data from TCGA and utilized samples from METABRIC as a validation data set. Top pathways that were significantly enriched in ILC were related to immune response. ILC exhibited a higher activity of almost all types of immune cells based on cell type-specific signatures compared to IDC. Conversely, pathways that were less enriched in ILC were related to protein translation and metabolism, which we functionally validated in cell lines. The higher immune activity uncovered in our study highlights the currently unexplored potential of a response to immunotherapy in a subset of patients with ILC. Furthermore, the lower rates of protein translation and metabolism - known features of tumor dormancy - may play a role in the late recurrences of ILC and lower detection rate in mammography and PET scanning.

Fatty Acid Synthase induced S6Kinase facilitates USP11-eIF4B complex formation for sustained oncogenic translation in DLBCL

Altered lipid metabolism and aberrant protein translation are strongly associated with cancerous outgrowth; however, the inter-regulation of these key processes is still underexplored in diffuse large B-cell lymphoma (DLBCL). Although fatty acid synthase (FASN) activity is reported to positively correlate with PI3K-Akt-mTOR pathway that can modulate protein synthesis, the precise impact of FASN inhibition on this process is still unknown. Herein, we demonstrate that attenuating FASN expression or its activity significantly reduces eIF4B (eukaryotic initiation factor 4B) levels and consequently overall protein translation. Through biochemical studies, we identified eIF4B as a bonafide substrate of USP11, which stabilizes and enhances eIF4B activity. Employing both pharmacological and genetic approaches, we establish that FASN-induced PI3K-S6Kinase signaling phosphorylates USP11 enhancing its interaction with eIF4B and thereby promoting oncogenic translation.

Translation initiation factors and their relevance in cancer

Deregulation of several translation initiation factors occurs in numerous types of cancers. Translation initiation factors are not merely ancillary players in cancer development and progression, but rather, they are key participants in cellular transformation and tumor development. In fact, the altered expression of translation initiation factors is involved in cancer cell survival, metastasis and tumor angiogenesis. Although the exact mechanisms remain to be fully characterized, translation initiation factors comprise novel targets for pharmacologic intervention. Here we review the most recently established roles of initiation factors in cancer development and progression, as well as unique methods used to study translational regulation.

Recent advances in melanoma research via "omics" platforms

Melanoma has a high mortality rate and metastatic melanoma is highly resistant to conventional therapies. "Omics" fields such as proteomics and microRNA and exosome studies have provided new knowledge to complement the information generated by genomic studies. This work aimed to review the current status of biomarker discovery for melanoma through multi-"omics" platforms. A few sets of novel microRNAs and proteins are described, some of them with important implications in suppressing melanoma at different stages. Upregulation of genes involved in angiogenesis, immunosuppressive factors, modification of stroma, capture of melanoma cells in lymph nodes and factors responsible for tumour cell recruitment have been identified in exosomes, among molecules with other functions. A remarkable series of proteins involved in epithelial-mesenchymal/mesenchymal-epithelial transitions, inflammation, motility, proliferation and progression processes, centrosome amplification, aneuploidy, inhibition of CD8+ effector T-cells, and metastasis in general were identified. Genomic and protein-protein interactions or metabolome levels were not analysed. Proteomics tools such as Orbitrap shotgun mass spectrometry or deep mining proteomic analysis utilizing high-resolution reversed phase nanoseparation in combination with mass spectrometry are also discussed. The application of these tools together with bioinformatics approaches applied to the clinical setting will enable the implementation of personalized medicine in the near future.