Signal transduction and the Ets family of transcription factors

CircMFN2/miR-361-3p/ELK1 feedback loop promotes glutaminolysis and the progression of hepatocellular carcinoma

Current evidence indicates that circRNAs are involved in the development of multiple malignancies including hepatocellular carcinoma (HCC). However, the specific functions of circRNAs in HCC metabolism and progression and their underlying regulatory mechanisms remain unclear. We have identified a novel circRNA circMFN2, by bioinformatics analysis of circRNA microarray data from the GEO database. The levels of circMFN2 were assessed in HCC cell lines and tissues, and its clinical relevance was assessed. The effect of circMFN2 on HCC cells was evaluated in vitro and in vivo. The effect of ELK1 on glutaminolysis and HCC progression was also explored. Patients with HCC and high circMFN2 expression exhibited worse survival outcomes. Functionally, downregulation of circMFN2 repressed the proliferation, invasion, and migration of HCC cells in vitro, whereas ectopic expression of circMFN2 had the opposite effects. The effects of tumor enhancement by circMFN2 on HCC were confirmed by in vivo experiments. Mechanistically, circMFN2 acted as a sponge for miR-361-3p, leading to the upregulation of its target ELK1, whereas ELK1 was enriched in the MFN2 promoter to enhance the transcription and expression of MFN2, indirectly leading to the upregulation of circMFN2. Additionally, we found that circMFN2 promotes glutaminolysis in HCC by increasing ELK1 phosphorylation. We concluded that circMFN2 facilitates HCC progression via a circMFN2/miR-361-3p/ELK1 feedback loop, which promotes glutaminolysis mediated by the upregulation of phosphorylated ELK1. Therefore, circMFN2 not only serves as a potential prognostic indicator, but it could also serve as a therapeutic target for HCC. Further studies are warranted.

Evidence for Fgf and Wnt regulation of Lhx2 during limb development via two limb-specific Lhx2-associated cis-regulatory modules

Introduction

In vertebrate limb morphogenesis, wingless-related integration site (Wnt) proteins and fibroblast growth factors (Fgfs) secreted from the apical ectodermal ridge (AER) coordinate proximodistal outgrowth. Fgfs also sustain sonic hedgehog (Shh) in the zone of polarizing activity (ZPA). Shh directs anteroposterior patterning and expansion and regulates AER-Fgfs, establishing a positive regulatory feedback loop that is vital in sustaining limb outgrowth. The transcription factor LIM homeodomain 2 (Lhx2) is expressed in the distal mesoderm and coordinates AER and ZPA signals that control cellular proliferation, differentiation, and shaping of the developing limb. Yet how Lhx2 is transcriptionally regulated to support such functions has only been partially characterized.

Methods/Results

We have identified two limb-specific cis-regulatory modules (CRMs) active within the Lhx2 expression domain in the limb. Chromatin conformation analysis of the Lhx2 locus in mouse embryonic limb bud cells predicted CRMs-Lhx2 promoter interactions. Single-cell RNA-sequencing analysis of limb bud cells revealed co-expression of several Fgf-related Ets and Wnt-related Tcf/Lef transcripts in Lhx2-expressing cells. Additionally, disruption of Ets and Tcf/Lef binding sites resulted in loss of reporter-driven CRM activity. Finally, binding of β-catenin to both Lhx2-associated CRMs supports the associated binding of Tcf/Lef transcription factors.

Discussion

These results suggest a role for Ets and Tcf/Lef transcription factors in the regulation of Lhx2 expression through these limb-specific Lhx2-associated CRMs. Moreover, these CRMs provide a mechanism for Fgf and Wnt signaling to localize and maintain distal Lhx2 expression during vertebrate limb development.

Dynamic Coupling of MAPK Signaling to the Guanine Nucleotide Exchange Factor GEF-H1

The KRAS gene is nearly ubiquitously subjected to activating mutation in pancreatic adenocarcinomas (PDAC), occurring at a frequency of over 90% in tumors. Mutant KRAS drives sustained signaling through the MAPK pathway to affect frequently disrupted cancer phenotypes including transcription, proliferation and cell survival. Recent research has shown that PDAC tumor growth and survival required a guanine nucleotide exchange factor for RAS homolog family member A (RhoA) called GEF-H1. The GEF-H1 protein, encoded by the ARHGEF2 gene, is a microtubule-associated GEF for RhoA that promotes invasion-migration of PDAC cells via activation of RhoA. Unexpectedly, independent of its RhoGEF activity, GEF-H1 was found to potentiate MAPK signaling by scaffolding protein phosphatase 2A (PP2A) to the kinase suppressor of Ras 1 (KSR-1). In a feedback-dependent manner, enhanced MAPK activity drives expression of ARHGEF2 via regulation of transcription factors ETS and SP, and the RAS responsive element-binding protein 1 (RREB1). RREB1 a negative regulator of ARHGEF2 expression, is downregulated in PDAC cells, which permits sustained expression of GEF-H1 for PDAC tumor survival and subsequent MAPK pathway activation. Given that MAPK targeted therapies show limited clinical efficacy, highlights the need for novel targets. This review describes the unexpected complexity of GEF-H1 function leading to positive feedback that potentiates RAS-MAPK signaling and suggests inhibition of GEF-H1 as a therapeutic strategy for RAS-driven cancers.

Pan-cancer analysis of the potential of PEA3 subfamily genes as tumor markers

Polyomavirus enhancer activator 3 (PEA3), an ETS transcription factor, has been documented to regulate the development and metastasis of human cancers. Nonetheless, a thorough analysis examining the relationship between the PEA3 subfamily members and tumour development, prognosis, and the tumour microenvironment (TME) across various cancer types has not yet been conducted. The expression profiles and prognostic significance of the PEA3 subfamily were evaluated using data from the GEO, TCGA, and PrognoScan databases, in conjunction with COX regression analyses and the Kaplan-Meier Plotter. Furthermore, the relationships between PEA3 subfamily expression, stemness scores, tumor microenvironments, immune subtypes, and drug susceptibility across multiple cancer types were explored. We found that ETV1, ETV4 and ETV5 are highly expressed in cancer, and their biological functions are synergistic. In the prognostic analysis of the Cancer Genome Atlas, the PEA3 subfamily genes were found to be associated with the prognosis of multiple cancers such as Lung adenocarcinoma (LUAD), Liver hepatocellular carcinoma (LIHC), etc., and marked a worse prognosis at different endpoints. In addition, it was significantly correlated with the stromal and immune scores of pan-cancer, and also significantly associated with the RNA stemness score and DNA stemness score of pan-cancer. Expression levels of the PEA3 subfamily genes correlate with immune subtypes of LIHC, LUAD, and Lung squamous cell carcinoma. We also found a variety of drugs with positive and negative associations of ETV1, ETV4 and ETV5. These findings elucidate the role of the PEA3 subfamily gene as a biomarker for carcinogenesis and cancer progression, offering valuable insights for future research into the PEA3 subfamily gene as a potential therapeutic target across various cancer types.

The Blueprint of Logical Decisions in a NF-κB Signaling System

Nearly identical cells can exhibit substantially different responses to the same stimulus that causes phenotype diversity. Such interplay between phenotype diversity and the architecture of regulatory circuits is crucial since it determines the state of a biological cell. Here, we theoretically analyze how the circuit blueprints of NF-κB in cellular environments are formed and their role in determining the cells' metabolic state. The NF-κB is a collective name for a developmental conserved family of five different transcription factors that can form homodimers or heterodimers and often promote DNA looping to reprogram the inflammatory gene response. The NF-κB controls many biological functions, including cellular differentiation, proliferation, migration, and survival. Our model shows that nuclear localization of NF-κB differentially promotes logic operations such as AND, NAND, NOR, and OR in its regulatory network. Through the quantitative thermodynamic model of transcriptional regulation and systematic variation of promoter-enhancer interaction modes, we can account for the origin of various logic gates as formed in the NF-κB system. We further show that the interconversion or switching of logic gates yielded under systematic variations of the stimuli activity and DNA looping parameters. Such computation occurs in regulatory and signaling pathways in individual cells at a molecular scale, which one can exploit to design a biomolecular computer.

Dietary steroids promote body weight growth and induce gametogenesis by increasing the expressions of genes related to cell proliferation of sea cucumber (Apostichopus japonicus)

Steroids play a vital role in animal survival, promoting growth and development when administered appropriate concentration exogenously. However, it remains unclear whether steroids can induce gonadal development and the underlying mechanism. This study assessed sea cucumber weights post-culturing, employing paraffin sections and RNA sequencing (RNA-seq) to explore gonadal changes and gene expression in response to exogenous steroid addition. Testosterone and cholesterol, dissolved in absolute ethanol, were incorporated into sea cucumber diets. After 30 days, testosterone and cholesterol significantly increased sea cucumber weights, with the total weight of experimental groups surpassing the control. The testosterone-fed group exhibited significantly higher eviscerated weight than the control group. In addition, dietary steroids influenced gonad morphology and upregulated genes related to cell proliferation，such as RPL35, PC, eLF-1, MPC2, ADCY10 and CYP2C18. Thees upregulated differentially expressed genes were significantly enriched in the organic system, metabolism, genetic information and environmental information categories. These findings imply that steroids may contribute to the growth and the process of genetic information translation and protein synthesis essential for gonadal development and gametogenesis.

Transcription factors regulating vasculogenesis and angiogenesis

Transcription factors (TFs) play a crucial role in regulating the dynamic and precise patterns of gene expression required for the initial specification of endothelial cells (ECs), and during endothelial growth and differentiation. While sharing many core features, ECs can be highly heterogeneous. Differential gene expression between ECs is essential to pattern the hierarchical vascular network into arteries, veins and capillaries, to drive angiogenic growth of new vessels, and to direct specialization in response to local signals. Unlike many other cell types, ECs have no single master regulator, instead relying on differing combinations of a necessarily limited repertoire of TFs to achieve tight spatial and temporal activation and repression of gene expression. Here, we will discuss the cohort of TFs known to be involved in directing gene expression during different stages of mammalian vasculogenesis and angiogenesis, with a primary focus on development.

Altered transcription factor targeting is associated with differential peripheral blood mononuclear cell proportions in sarcoidosis

Introduction

In sarcoidosis, peripheral lymphopenia and anergy have been associated with increased inflammation and maladaptive immune activity, likely promoting development of chronic and progressive disease. However, the molecular mechanisms that lead to reduced lymphocyte proportions, particularly CD4+ T-cells, have not been fully elucidated. We posit that paradoxical peripheral lymphopenia is characterized by a dysregulated transcriptomic network associated with cell function and fate that results from altered transcription factor targeting activity.

Methods

Messenger RNA-sequencing (mRNA-seq) was performed on peripheral blood mononuclear cells (PBMCs) from ACCESS study subjects with sarcoidosis and matched controls and findings validated on a sarcoidosis case-control cohort and a sarcoidosis case series. Preserved PBMC transcriptomic networks between case-control cohorts were assessed to establish cellular associations with gene modules and define regulatory targeting involved in sarcoidosis immune dysregulation utilizing weighted gene co-expression network analysis and differential transcription factor involvement analysis. Network centrality measures identified master transcriptional regulators of subnetworks related to cell proliferation and death. Predictive models of differential PBMC proportions constructed from ACCESS target gene expression corroborated the relationship between aberrant transcription factor regulatory activity and imputed and clinical PBMC populations in the validation cohorts.

Results

We identified two unique and preserved gene modules significantly associated with sarcoidosis immune dysregulation. Strikingly, increased expression of a monocyte-driven, and not a lymphocyte-driven, gene module related to innate immunity and cell death was the best predictor of peripheral CD4+ T-cell proportions. Within the gene network of this monocyte-driven module, TLE3 and CBX8 were determined to be master regulators of the cell death subnetwork. A core gene signature of differentially over-expressed target genes of TLE3 and CBX8 involved in cellular communication and immune response regulation accurately predicted imputed and clinical monocyte expansion and CD4+ T-cell depletion.

Conclusions

Altered transcriptional regulation associated with aberrant gene expression of a monocyte-driven transcriptional network likely influences lymphocyte function and survival. Although further investigation is warranted, this indicates that crosstalk between hyperactive monocytes and lymphocytes may instigate peripheral lymphopenia and underlie sarcoidosis immune dysregulation and pathogenesis. Future therapies selectively targeting master regulators, or their targets, may mitigate dysregulated immune processes in sarcoidosis and disease progression.

Regulation of MMP9 transcription by ETS1 in immortalized salivary gland epithelial cells of patients with salivary hypofunction and primary Sjögren's syndrome

Primary Sjögren’s syndrome (pSS) patients exhibit enhanced degradation of the salivary epithelium initially through MMP9 overexpression. We assessed the expression of MMP9 and an associated transcription factor, ETS1, in primary salivary gland epithelial cells (SGECs) and investigated potential regulatory mechanism(s) in immortalized SGECs. SGECs and iSGECs were derived from pSS and/or xerostomic “sicca” patients. siRNA knockdown of ETS1 in iSGECs was performed to determine MMP9 mRNA (qRT-PCR) and protein expression (ELISA). ETS1 binding to MMP9 promoter was assessed by luciferase activity and binding confirmed by mutagenesis and ChIP. Effects of ETS1 overexpression on progenitor and Epithelial-Mesenchymal transition (EMT) associated markers were determined by Western blot. Expression of ETS1 and its phosphorylated form in iSGECs was determined by immunofluorescence microscopy. ETS1 and MMP9 were overexpressed in SGECs of pSS and non-pSS sicca patients with salivary gland lymphocytic infiltration compared to non-pSS sicca patients without infiltration. ETS1 siRNA knockdown reduced both MMP9 mRNA and protein levels. ETS1 overexpression affected the expression of EMT and progenitor cell markers. Lastly, ETS1 bound the MMP9 promoter within the DNA region of −296 bp to −339 bp. ETS1 may impair salivary function through direct transcriptional control of the MMP9 promoter. ETS1 upregulation may also affect other factors involved in repair of the dysfunctional pSS salivary epithelium.

Etv4 regulates nociception by controlling peptidergic sensory neuron development and peripheral tissue innervation

The perception of noxious environmental stimuli by nociceptive sensory neurons is an essential mechanism for the prevention of tissue damage. Etv4 is a transcriptional factor expressed in most nociceptors in dorsal root ganglia (DRG) during the embryonic development. However, its physiological role remains unclear. Here, we show that Etv4 ablation results in defects in the development of the peripheral peptidergic projections in vivo, and in deficits in axonal elongation and growth cone morphology in cultured sensory neurons in response to NGF. From a mechanistic point of view, our findings reveal that NGF regulates Etv4-dependent gene expression of molecules involved in extracellular matrix (ECM) remodeling. Etv4-null mice were less sensitive to noxious heat stimuli and chemical pain, and this behavioral phenotype correlates with a significant reduction in the expression of the pain-transducing ion channel TRPV1 in mutant mice. Together, our data demonstrate that Etv4 is required for the correct innervation and function of peptidergic sensory neurons, regulating a transcriptional program that involves molecules associated with axonal growth and pain transduction.

Identification of Prognostic Markers for Head and NeckSquamous Cell Carcinoma Based on Glycolysis-Related Genes

Head and neck squamous cell carcinomas (HNSCCs) comprise a heterogeneous group of tumors. Many patients respond differently to treatment and prognosis due to molecular heterogeneity. There is an urgent need to identify novel biomarkers to predict the prognosis of patients with HNSCC. Glycolysis has an important influence on the progress of HNSCC. Therefore, we investigated the prognostic significance of glycolysis-related genes in HNSCC. Our results showed that ELF3, AURKA, and ADH7 of 20 glycolysis-related DEGs were significantly related to survival and were used to construct the risk signature. The risk score showed high accuracy in distinguishing the overall survival (OS) of HNSCC. The Kaplan–Meier curves demonstrated that the risk score was associated with an unfavorable prognosis in patients with female sex, male sex, grade 3, T1/2 stage, N⁺ stage, N2 stage, M0 stage, and clinical stage III/IV. Independent prognostic analysis showed that clinical stage and risk score were strongly associated with OS. Moreover, the risk score had higher accuracy in predicting 1-, 3-, and 5-year survival. AURKA and ADH7 were only significantly related to M1 macrophages and neutrophils, respectively, while ELF3 was significantly correlated with M2 macrophages and monocytes (all p < 0.05).The ceRNA network demonstrated that miR-335-5p and miR-9-5p may play core roles in the regulation of these three genes in HNSCC. The risk score constructed based on three glycolysis-related genes showed high accuracy in predicting the prognosis and clinicopathological characteristics of HNSCC.

elk1/miR-462-731 Feedback Loop Regulates Macrophages Polarization and Phagocytosis in Grass Carp (Ctenopharyngodon idella)

MicroRNA clusters are microRNAs (miRNAs) that are distributed in close proximity on chromosomes. In this study, we report a miRNA cluster identified from grass carp (Ctenopharyngodon idella), miR-462-731, which plays a positive role in host antibacterial immunity. The expression of miR-462-731 was disrupted after infection by Aeromonas hydrophila. Transcription factor ETS transcription factor ELK1 was identified to bind to the promoter of the miR-462-731 cluster and suppress its expression. In addition, miR-731 negatively regulates the expression of elk1, forms an elk1/miR-462-731 double negative feedback loop. In addition, we found that miR-731 directly targets ezrin a (ezra), participates in inducing PI3K/AKT signaling in macrophage, to induce macrophage polarization to the M1 phenotype with stronger phagocytosis. Our results demonstrate a novel elk1/miR-462-731 feedback loop. The data deepen our understanding of the relationship between macrophage polarization and phagocytosis in teleost fish.

RAGE management: ETS1- EGR1 mediated transcriptional networks regulate angiogenic factors in wood frogs

Freeze-tolerant species, such as wood frogs (Rana sylvatica), are susceptible to multiple co-occurring stresses that they must overcome to survive. Freezing is accompanied by mechanical stress and dehydration due to ice crystal formation in the extracellular space, ischemia/anoxia due to interruption in blood flood, and hyperglycemia due to cryoprotective measures. Wood frogs can survive dehydration, anoxia, and high glucose stress independently of freezing, thereby creating a multifactorial model for studying freeze-tolerance. Oxidative stress and high glucose levels favors the production of pro-oxidant molecules and advanced glycation end product (AGE) adducts that could cause substantial cellular damage. In this study, the involvement of the high mobility group box 1 (HMGB1)-AGE/RAGE (receptor for AGE) axis and the regulation of ETS1 and EGR1-mediated angiogenic responses were investigated in liver of wood frogs expose to freeze/thaw, anoxia/reoxygenation and dehydration/rehydration treatments. HMGB1 and not AGE-adducts are likely to induce the activation of ETS1 and EGR1 via the RAGE pathway. The increase in nuclear localization of both ETS1 and EGR1, but not DNA binding activity in response to stress hints to a potential spatial and temporal regulation in inducing angiogenic factors. Freeze/thaw and dehydration/rehydration treatments increase the levels of both pro- and anti-angiogenic factors, perhaps to prepare for the distribution of cryoprotectants or enable the repair of damaged capillaries and wounds when needed. Overall, wood frogs appear to anticipate the need for angiogenesis in response to freezing and dehydration but not anoxic treatments, probably due to mechanical stress associated with the two former conditions.

Ectopic viral integration Site-1 oncogene promotes NRAS pathway through epigenetic silencing of microRNA-124 in acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is an aggressive hematological malignancy characterized by genetic mutations that promote proliferation of myeloid progenitors and prevent their differentiation. Over-expression of Ectopic Viral Integration site-1(EVI-1) is related to the poor prognosis in myeloid leukemia, but the underlying mechanism remains unclear.

METHODS

Using qRT-PCR and western blotting, we quantified expressions of EVI-1, NRAS and ERK/p-ERK in leukemia cell lines and PBMCs. Using WTS-8 and cell cycle analysis, we further investigated whether downregulation of EVI-1 by siRNA can inhibit cell proliferation. Microscopic observation of peripheral blood cells from EVI-1 transgenic zebrafish and WT control were analyzed by Wright Giemsa staining. Using miR-seq, qPCR, dual-luciferase reporter and coimmunoprecipitation assays, we revealed the relationship between EVI-1, miR-124 and NRAS.

RESULTS

EVI-1 was highly expressed in both primary AML and leukemia cell lines (THP-1 and K562). In a transgenic zebrafish model, EVI-1 mediated higher mortality and induced immature hematopoietic cells in the blood circulation, suggesting its oncogenic role. Furthermore, our results suggested that EVI-1 upregulated NRAS expression, thereby activating the RAS/ERK pathway through epigenetic silencing of a potent NRAS suppressor, miR-124. In this study, we found that EVI1 physically interacts with Dnmt3a to form a protein complex that targets and binds to regulatory elements of miR-124.

CONCLUSIONS

Overall, the current findings demonstrate that EVI-1 overexpression converges on the regulation of miR-124 promoter methylation and activation of the RAS/ERK pathway in AML carcinogenesis, and suggest EVI-1 and/or miR-124 as therapeutic targets for this dismal disease.

The Impact of Sex Chromosomes in the Sexual Dimorphism of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a sex-biased disease with a poorly understood female prevalence. Emerging research suggests that nonhormonal factors, such as the XX or XY sex chromosome complement and sex bias in gene expression, may also lead to sex-based differences in PAH incidence, penetrance, and progression. Typically, one of females' two X chromosomes is epigenetically silenced to offer a gender-balanced gene expression. Recent data demonstrate that the long noncoding RNA X-inactive specific transcript, essential for X chromosome inactivation and dosage compensation of X-linked gene expression, shows elevated levels in female PAH lung specimens compared with controls. This molecular event leads to incomplete inactivation of the females' second X chromosome, abnormal expression of X-linked gene(s) involved in PAH pathophysiology, and a pulmonary artery endothelial cell (PAEC) proliferative phenotype. Moreover, the pathogenic proliferative p38 mitogen-activated protein kinase/ETS transcription factor ELK1 (Elk1)/cFos signaling is mechanistically linked to the sexually dimorphic proliferative response of PAECs in PAH. Apprehending the complicated relationship between long noncoding RNA X-inactive specific transcript and X-linked genes and how this relationship integrates into a sexually dimorphic proliferation of PAECs and PAH sex paradox remain challenging. We highlight herein new findings related to how the sex chromosome complement and sex-differentiated epigenetic mechanisms to control gene expression are decisive players in the sexual dimorphism of PAH. Pharmacologic interventions in the light of the newly elucidated mechanisms are discussed.

Shifting the Focus of Signaling Abnormalities in Colon Cancer

Colon cancer tumorigenesis occurs incrementally. The process involves the acquisition of mutations which typically follow an established pattern: activation of WNT signaling, activation of RAS signaling, and inhibition of TGF-β signaling. This arrangement recapitulates, to some degree, the stem cell niche of the intestinal epithelium, which maintains WNT and EGF activity while suppressing TGF-β. The resemblance between the intestinal stem cell environment and colon cancer suggests that the concerted activity of these pathways generates and maintains a potent growth-inducing stimulus. However, each pathway has a myriad of downstream targets, making it difficult to identify which aspects of these pathways are drivers. To address this, we utilize the cell cycle, the ultimate regulator of cell proliferation, as a foundation for cross-pathway integration. We attempt to generate an overview of colon cancer signaling patterns by integrating the major colon cancer signaling pathways in the context of cell replication, specifically, the entrance from G1 into S-phase.

Inhibition of β-catenin dependent WNT signalling upregulates the transcriptional repressor NR0B1 and downregulates markers of an A9 phenotype in human embryonic stem cell-derived dopaminergic neurons: Implications for Parkinson's disease

In this study we investigate how β-catenin-dependent WNT signalling impacts midbrain dopaminergic neuron (mDA) specification. mDA cultures at day 65 of differentiation responded to 25 days of the tankyrase inhibitor XAV969 (XAV, 100nM) with reduced expression of markers of an A9 mDA phenotype (KCNJ6, ALDH1A1 and TH) but increased expression of the transcriptional repressors NR0B1 and NR0B2. Overexpression of NR0B1 and or NR0B2 promoted a loss of A9 dopaminergic neuron phenotype markers (KCNJ6, ALDH1A1 and TH). Overexpression of NR0B1, but not NR0B2 promoted a reduction in expression of the β-catenin-dependent WNT signalling pathway activator RSPO2. Analysis of Parkinson’s disease (PD) transcriptomic databases shows a profound PD-associated elevation of NR0B1 as well as reduced transcript for RSPO2. We conclude that reduced β-catenin-dependent WNT signalling impacts dopaminergic neuron identity, in vitro, through increased expression of the transcriptional repressor, NR0B1. We also speculate that dopaminergic neuron regulatory mechanisms may be perturbed in PD and that this may have an impact upon both existing nigral neurons and also neural progenitors transplanted as PD therapy.

Multidrug efflux transporter ABCG2: expression and regulation

The adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) was originally discovered in a multidrug-resistant breast cancer cell line. Studies in the past have expanded the understanding of its role in physiology, disease pathology and drug resistance. With a widely distributed expression across different cell types, ABCG2 plays a central role in ATP-dependent efflux of a vast range of endogenous and exogenous molecules, thereby maintaining cellular homeostasis and providing tissue protection against xenobiotic insults. However, ABCG2 expression is subjected to alterations under various pathophysiological conditions such as inflammation, infection, tissue injury, disease pathology and in response to xenobiotics and endobiotics. These changes may interfere with the bioavailability of therapeutic substrate drugs conferring drug resistance and in certain cases worsen the pathophysiological state aggravating its severity. Considering the crucial role of ABCG2 in normal physiology, therapeutic interventions directly targeting the transporter function may produce serious side effects. Therefore, modulation of transporter regulation instead of inhibiting the transporter itself will allow subtle changes in ABCG2 activity. This requires a thorough comprehension of diverse factors and complex signaling pathways (Kinases, Wnt/β-catenin, Sonic hedgehog) operating at multiple regulatory levels dictating ABCG2 expression and activity. This review features a background on the physiological role of transporter, factors that modulate ABCG2 levels and highlights various signaling pathways, molecular mechanisms and genetic polymorphisms in ABCG2 regulation. This understanding will aid in identifying potential molecular targets for therapeutic interventions to overcome ABCG2-mediated multidrug resistance (MDR) and to manage ABCG2-related pathophysiology.

Chemical Inhibition of Apurinic-Apyrimidinic Endonuclease 1 Redox and DNA Repair Functions Affects the Inflammatory Response via Different but Overlapping Mechanisms

The presence of oxidized DNA lesions, such as 7,8-dihydro-8-oxoguanine (8-oxoG) and apurinic/apyrimidinic sites (AP sites), has been described as epigenetic signals that are involved in gene expression control. In mammals, Apurinic-apyrimidinic endonuclease 1/Redox factor-1 (APE1/Ref-1) is the main AP endonuclease of the base excision repair (BER) pathway and is involved in active demethylation processes. In addition, APE1/Ref-1, through its redox function, regulates several transcriptional factors. However, the transcriptional control targets of each APE1 function are not completely known. In this study, a transcriptomic approach was used to investigate the effects of chemical inhibition of APE1/Ref-1 redox or DNA repair functions by E3330 or methoxyamine (MX) in an inflammatory cellular model. Under lipopolysaccharide (LPS) stimulation, both E3330 and MX reduced the expression of some cytokines and chemokines. Interestingly, E3330 treatment reduced cell viability after 48 h of the treatment. Genes related to inflammatory response and mitochondrial processes were downregulated in both treatments. In the E3330 treatment, RNA processing and ribosome biogenesis genes were downregulated, while they were upregulated in the MX treatment. Furthermore, in the E3330 treatment, the cellular stress response was the main upregulated process, while the cellular macromolecule metabolic process was observed in MX-upregulated genes. Nuclear respiratory factor 1 (NRF1) was predicted to be a master regulator of the downregulated genes in both treatments, while the ETS transcription factor ELK1 (ELK1) was predicted to be a master regulator only for E3330 treatment. Decreased expression of ELK1 and its target genes and a reduced 28S/18S ratio were observed, suggesting impaired rRNA processing. In addition, both redox and repair functions can affect the expression of NRF1 and GABPA target genes. The master regulators predicted for upregulated genes were YY1 and FLI1 for the E3330 and MX treatments, respectively. In summary, the chemical inhibition of APE1/Ref-1 affects gene expression regulated mainly by transcriptional factors of the ETS family, showing partial overlap of APE1 redox and DNA repair functions, suggesting that these activities are not entirely independent. This work provides a new perspective on the interaction between APE1 redox and DNA repair activity in inflammatory response modulation and transcription.

The Mutational Landscape of Myeloid Leukaemia in Down Syndrome

Children with Down syndrome (DS) are particularly prone to haematopoietic disorders. Paediatric myeloid malignancies in DS occur at an unusually high frequency and generally follow a well-defined stepwise clinical evolution. First, the acquisition of mutations in the GATA1 transcription factor gives rise to a transient myeloproliferative disorder (TMD) in DS newborns. While this condition spontaneously resolves in most cases, some clones can acquire additional mutations, which trigger myeloid leukaemia of Down syndrome (ML-DS). These secondary mutations are predominantly found in chromatin and epigenetic regulators-such as cohesin, CTCF or EZH2-and in signalling mediators of the JAK/STAT and RAS pathways. Most of them are also found in non-DS myeloid malignancies, albeit at extremely different frequencies. Intriguingly, mutations in proteins involved in the three-dimensional organization of the genome are found in nearly 50% of cases. How the resulting mutant proteins cooperate with trisomy 21 and mutant GATA1 to promote ML-DS is not fully understood. In this review, we summarize and discuss current knowledge about the sequential acquisition of genomic alterations in ML-DS.

Current Treatment of Juvenile Myelomonocytic Leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare pediatric leukemia characterized by mutations in five canonical RAS pathway genes. The diagnosis is made by typical clinical and hematological findings associated with a compatible mutation. Although this is sufficient for clinical decision-making in most JMML cases, more in-depth analysis can include DNA methylation class and panel sequencing analysis for secondary mutations. NRAS-initiated JMML is heterogeneous and adequate management ranges from watchful waiting to allogeneic hematopoietic stem cell transplantation (HSCT). Upfront azacitidine in KRAS patients can achieve long-term remissions without HSCT; if HSCT is required, a less toxic preparative regimen is recommended. Germline CBL patients often experience spontaneous resolution of the leukemia or exhibit stable mixed chimerism after HSCT. JMML driven by PTPN11 or NF1 is often rapidly progressive, requires swift HSCT and may benefit from pretransplant therapy with azacitidine. Because graft-versus-leukemia alloimmunity is central to cure high risk patients, the immunosuppressive regimen should be discontinued early after HSCT.

Up-Regulation of the Long Noncoding RNA X-Inactive-Specific Transcript and the Sex Bias in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a sex-biased disease. Increased expression and activity of the long-noncoding RNA X-inactive-specific transcript (Xist), essential for X-chromosome inactivation and dosage compensation of X-linked genes, may explain the sex bias of PAH. The present studies used a murine model of plexiform PAH, the intersectin-1s (ITSN) heterozygous knockout (KOITSN+/-) mouse transduced with an ITSN fragment (EHITSN) possessing endothelial cell proliferative activity, in conjunction with molecular, cell biology, biochemical, morphologic, and functional approaches. The data demonstrate significant sex-centered differences with regard to EHITSN-induced alterations in pulmonary artery remodeling, lung hemodynamics, and p38/ETS domain containing protein/c-Fos signaling, altogether leading to a more severe female lung PAH phenotype. Moreover, the long-noncoding RNA-Xist is up-regulated in the lungs of female EHITSN-KOITSN+/- mice compared with that in female wild-type mice, leading to sex-specific modulation of the X-linked gene ETS domain containing protein and its target, two molecular events also characteristic to female human PAH lung. More importantly, cyclin A1 expression in the S and G2/M phases of the cell cycle of synchronized pulmonary artery endothelial cells of female PAH patients is greater versus controls, suggesting functional hyperproliferation. Thus, Xist up-regulation leading to female pulmonary artery endothelial cell sexual dimorphic behavior may provide a better understanding of the origin of sex bias in PAH. Notably, the EHITSN-KOITSN+/- mouse is a unique experimental animal model of PAH that recapitulates most of the sexually dimorphic characteristics of human disease.

Phosphoprotein enriched in astrocytes (PEA)-15 is a novel regulator of adipose tissue expansion

Excessive expansion of adipose tissue in obesity typically leads to overflow and accumulation of lipids in other tissues, causing fatty liver disease and atherosclerosis. The intracellular protein, phosphoprotein enriched in astrocytes (PEA)-15 has been linked to metabolic disease but its role in lipid storage has not been examined. To delineate the role of PEA-15 in adipose tissue, we placed PEA-15^−/− mice on a high fat diet. These mice developed increased body weight and greater white adipose tissue expansion compared to high fat diet-fed wild type mice. This was due to increased adipocyte cell size in PEA-15^−/− mice consistent with greater lipid storage capacity. Surprisingly, PEA-15^−/− mice exhibited improvements in whole body insulin sensitivity, lower hepatic weight and decreased serum triglycerides indicating a protective phenotype. To determine effects on atherosclerosis, PEA-15^−/− mice were crossed with the ApoE^−/− mice on a high fat diet. Strikingly, these mice were protected from atherosclerosis and had less hepatic lipid accumulation despite increased adiposity. Therefore, we reveal for the first time that PEA-15 plays a novel role in regulating the expansion of adipose tissue. Decreasing PEA-15 expression increases the sequestering of lipids in adipose tissue, protecting other tissues in obesity, thereby improving metabolic health.

Construction and Analysis of Survival-Associated Competing Endogenous RNA Network in Lung Adenocarcinoma

Increasing evidence has shown that noncoding RNAs play significant roles in the initiation, progression, and metastasis of tumours via participating in competing endogenous RNA (ceRNA) networks. However, the survival-associated ceRNA in lung adenocarcinoma (LUAD) remains poorly understood. In this study, we aimed to investigate the regulatory mechanisms underlying ceRNA in LUAD to identify novel prognostic factors. mRNA, lncRNA, and miRNA sequencing data obtained from the GDC data portal were utilized to identify differentially expressed (DE) RNAs. Survival-related RNAs were recognized using univariate Kaplan-Meier survival analysis. We performed functional enrichment analysis of survival-related mRNAs using the clusterProfiler package of R and STRING. lncRNA-miRNA and miRNA-mRNA interactions were predicted based on miRcode, Starbase, and miRanda. Subsequently, the survival-associated ceRNA network was constructed for LUAD. Multivariate Cox regression analysis was used to identify prognostic factors. Finally, we acquired 15 DE miRNAs, 49 DE lncRNAs, and 843 DE mRNAs associated with significant overall survival. Functional enrichment analysis indicated that survival-related DE mRNAs were enriched in cell cycle. The survival-associated lncRNA-miRNA-mRNA ceRNA network was constructed using five miRNAs, 49 mRNAs, and 21 lncRNAs. Furthermore, seven hub RNAs (LINC01936, miR-20a-5p, miR-31-5p, TNS1, TGFBR2, SMAD7, and NEDD4L) were identified based on the ceRNA network. LINC01936 and miR-31-5p were found to be significant using the multifactorial Cox regression model. In conclusion, we successfully constructed a survival-related lncRNA-miRNA-mRNA ceRNA regulatory network in LUAD and identified seven hub RNAs, which provide novel insights into the regulatory molecular mechanisms associated with survival of LUAD, and identified two independent prognostic predictors for LUAD.

ETS factors are required but not sufficient for specific patterns of enhancer activity in different endothelial subtypes

Correct vascular differentiation requires distinct patterns of gene expression in different subtypes of endothelial cells. Members of the ETS transcription factor family are essential for the transcriptional activation of arterial and angiogenesis-specific gene regulatory elements, leading to the hypothesis that they play lineage-defining roles in arterial and angiogenic differentiation directly downstream of VEGFA signalling. However, an alternative explanation is that ETS binding at enhancers and promoters is a general requirement for activation of many endothelial genes regardless of expression pattern, with subtype-specificity provided by additional factors. Here we use analysis of Ephb4 and Coup-TFII (Nr2f2) vein-specific enhancers to demonstrate that ETS factors are equally essential for vein, arterial and angiogenic-specific enhancer activity patterns. Further, we show that ETS factor binding at these vein-specific enhancers is enriched by VEGFA signalling, similar to that seen at arterial and angiogenic enhancers. However, while arterial and angiogenic enhancers can be activated by VEGFA in vivo, the Ephb4 and Coup-TFII venous enhancers are not, suggesting that the specificity of VEGFA-induced arterial and angiogenic enhancer activity occurs via non-ETS transcription factors. These results support a model in which ETS factors are not the primary regulators of specific patterns of gene expression in different endothelial subtypes.

•

Vein-specific enhancers can contain essential ETS motifs.

•

VEGFA induced an increase in ETS binding at vein, arterial and angiogenic enhancers.

•

VEGFA stimulation cannot induce vein-specific enhancer activity.

Role of RIN1 on telomerase activity driven by EGF-Ras mediated signaling in breast cancer

Epidermal growth factor (EGF)-receptor regulates several downstream signaling pathways upon EGF stimulation that involves cell proliferation, migration and invasion. Internalized EGF-receptor is either recycled or degraded, which fate is regulated in part by Ras interference 1 (RIN1). In this study, we tested the hypothesis that RIN1, a Ras effector protein and Rab5 guanine nucleotide exchange factor, controls several signaling molecules leading to the modulation of the telomerase activity; thus, allowing proper cell proliferation. We report that expression of RIN1 completely blocked proliferation of MCF-12 A and MCF-7 cells, while partially inhibited proliferation of MDA-MB-231 cells upon EGF stimulation. Furthermore, expression of the C-terminal region of RIN1 selectively plays a critical role in the inhibition of the proliferation of MDA-MB-231 cells. However, this inhibitory effect was specifically affected by the independent expression of RIN1:Vsp9 and RIN1:RA domains. Additionally, endogenous level of expression of RIN1 was decreased in metastatic MDA-MB-231 cells as compared with non-tumorigenic MCF-12 A cells. We observed that expression of RIN1:R94A mutant blocked the proliferation of MDA-MB-231 cells, while expression of RIN1:Y561F and RIN1:R629A mutants completely reversed the inhibitory effect of RIN1:WT. Consistent with our observations, we found that expression of RIN1:WT in MDA-MB-231 cells diminished both protein kinase B (AKT) and extracellular-signal-regulated kinase 1/2 (ERK1/2) activities while p38 mitogen-activated protein kinases (p38 MAPK) and stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK) were unaffected, but it produced downregulation of cellular-myelocytomatosis (c-Myc), erythroblast transformation specific (Ets2) and signal transducer and activator of transcription 3 (Stat3) activities. Inversely, expression of high-mobility group box 1 (HMBG1) was inhibited whereas expression of forkhead box transcription factor 1 (FOXO1) was increased in cells expressing RIN1. Interestingly, expression of RIN1 blocked telomerase activity and human telomerase reverse transcriptase (hTERT) expression, which correlated with the downregulations of c-Myc, Ets-2 and Stat3 activation. Taken together these findings indicate that RIN1 is a critical player in the modulation of the telomerase activity as well as hTERT expression in MDA-MB-231 cells upon EGF stimulation.

RAS Function in cancer cells: translating membrane biology and biochemistry into new therapeutics

The three human RAS proteins are mutated and constitutively activated in ∼20% of cancers leading to cell growth and proliferation. For the past three decades, many attempts have been made to inhibit these proteins with little success. Recently; however, multiple methods have emerged to inhibit KRAS, the most prevalently mutated isoform. These methods and the underlying biology will be discussed in this review with a special focus on KRAS-plasma membrane interactions.

Heme oxygenase promotes B-Raf-dependent melanosphere formation

Biosynthesis and degradation of heme, an iron-bound protoporphyrin molecule utilized by a wide variety of metabolic processes, are tightly regulated. Two closely related enzymes, heme oxygenase 1 (HMOX1) and heme oxygenase 2 (HMOX2), degrade free heme to produce carbon monoxide, Fe²⁺ , and biliverdin. HMOX1 expression is controlled via the transcriptional activator, NFE2L2, and the transcriptional repressor, Bach1. Transcription of HMOX1 and other NFE2L2-dependent genes is increased in response to electrophilic and reactive oxygen species. Many tumor-derived cell lines have elevated levels of NFE2L2. Elevated expression of NFE2L2-dependent genes contributes to tumor growth and acquired resistance to therapies. Here, we report a novel role for heme oxygenase activity in melanosphere formation by human melanoma-derived cell lines. Transcriptional induction of HMOX1 through derepression of Bach1 or transcriptional activation of HMOX2 by oncogenic B-Raf^V600E results in increased melanosphere formation. Genetic ablation of HMOX1 diminishes melanosphere formation. Further, inhibition of heme oxygenase activity with tin protoporphyrin markedly reduces melanosphere formation driven by either Bach1 derepression or B-Raf^V600E expression. Global transcriptome analyses implicate genes involved in focal adhesion and extracellular matrix interactions in melanosphere formation.

Quantitative Phosphoproteomics Reveals Cell Alignment and Mitochondrial Length Change under Cyclic Stretching in Lung Cells

Lung cancer is a leading cause of death. Most previous studies have been based on traditional cell-culturing methods. However, lung cells are periodically subjected to mechanical forces during breathing. Understanding the mechanisms underlying the cyclic stretching induced in lung cells may be important for lung cancer therapy. Here, we applied cyclic stretching to stimulate the continual contraction that is present under physiological conditions in lung cells. We first uncovered the stretching-induced phosphoproteome in lung cancer cell line A549 and fibroblast cell line IMR-90. We identified 2048 and 2604 phosphosites corresponding to 837 and 1008 phosphoproteins in A549 and IMR-90, respectively. Furthermore, we combined our phosphoproteomics and public gene expression data to identify the biological functions in response to cyclic stretching. Interestingly, cytoskeletal and mitochondrial reorganization were enriched. We further used cell imaging analysis to validate the profiling results and found that this physical force changed cell alignment and mitochondrial length. This study not only reveals the molecular mechanism of cyclic stretching but also provides evidence that cell stretching causes cellular rearrangement and mitochondrial length change.

Vascular transcriptome landscape of Trail-/- mice: Implications and therapeutic strategies for diabetic vascular disease

Circulating plasma TRAIL levels are suppressed in patients with cardiovascular and diabetic diseases. To identify novel targets in vascular metabolic diseases, genome-wide transcriptome of aortic tissue from Trail^-/- versus Trail^+/+ mice were interrogated. We found 861 genes differentially expressed with TRAIL deletion. Gene enrichment analyses showed many of these genes were related to inflammation, cell-to-cell cytoskeletal interactions, and transcriptional modulation. We identified vascular protective and pathological gene clusters, with Ifi205 as the most significantly reduced vascular protective gene, whereas Glut1, the most significantly increased pathological gene with TRAIL deletion. We hypothesized that therapeutic targets could be devised from such integrated analysis and validated our findings from vascular tissues of diabetic mice. From the differentially expressed gene targets, enriched transcription factor (TF) and microRNA binding motifs were identified. The top two TFs were Elk1 and Sp1, with enrichment to eight gene targets common to both. miR-520d-3p and miR-377-3p were the top enriched microRNAs with TRAIL deletion; with four overlapping genes enriched for both microRNAs. Our findings offer an alternate in silico approach for therapeutic target identification and present a deeper understanding of gene signatures and pathways altered with TRAIL suppression in the vasculature.

Double Agent: SPDEF Gene with Both Oncogenic and Tumor-Suppressor Functions in Breast Cancer

The dichotomy of cancer-regulatory genes into “oncogenes (OCGs)” and “tumor-suppressor genes (TSGs)” has greatly helped us in learning molecular details of tumor biology. SPDEF, known as the prostate-derived ETS factor, is reported to play a pivotal role in normal cell development and survival, which has also been endowed with dual characteristics in cancers. Breast cancer (BC) is a highly heterogeneous disease which becomes the leading reason for cancer-related fatality among women worldwide. The involvement of SPDEF in many aspects of BC has been postulated, whereas the mechanism governing the regulation of the pro- and anti-oncogenic activities of SPDEF in BC state remains poorly defined. In this review, we summarized SPDEF as the double agent involving in expression profiles, the regulatory mechanism in BC progression, as well as the role in diagnosis, treatment and prognosis of BC. The understanding of SPDEF duality has contributed to gain insight into the tumor biology and also add a new dimension to the new therapy targets for BC.

EGFR activates GDH1 transcription to promote glutamine metabolism through MEK/ERK/ELK1 pathway in glioblastoma

Cancer metabolism research has recently been revived and its focus expanded from glucose and the Warburg's effects on other nutrients, such as glutamine. The underlying mechanism of oncogenic alterations of glutaminolysis remains unclear. Genetic alterations of EGFR are observed in ~50% of glioblastoma (GBM) patients, and have been found to play important roles in the metabolic abnormalities of GBM. In this study, we found that glutamine metabolism was upregulated after EGFR activation in a GDH1 (glutamate dehydrogenase 1)-dependent manner. Knockdown of GDH1 significantly reduced the cell proliferation, colony formation and tumorigenesis abilities of glioblastoma cells. Furthermore, we showed that GDH1-mediated glutaminolysis was involved in EGF-promoted cell proliferation. EGFR triggered the phosphorylation of ELK1 at Ser 383 through activating MEK/ERK signaling. Phosphorylated ELK1 enriched in the promoter of GDH1 to activate the transcription of GDH1, which then promoted glutamine metabolism. In addition, EGFR activation did not accelerate glutaminolysis in ELK1 knockdown or ELK1 Ser383-mutated cells. Collectively, our findings indicate that EGFR phosphorylates ELK1 to activate GDH1 transcription and glutaminolysis through MEK/ERK pathway, providing new insight into oncogenic alterations of glutamine metabolism.

Integrative analysis identifies genetic variant modulating MICA expression and altering susceptibility to persistent HBV infection

BACKGROUND & AIMS

Genome-wide association studies have identified multiple genetic signals associated with the risk of persistent hepatitis B virus (HBV) infection and HBV-related hepatocellular carcinoma. However, the majority of the associated variants may only be markers of functional variants and the underlying biological mechanisms remain elusive. We hypothesized that the functional variants with modulating transcription factor (TF) binding affinity in genome-wide association studies-identified loci may influence the risk of persistent HBV infection in Chinese people.

METHODS

A systematic bioinformatics approach was implemented to prioritize potential functional variants that may influence TF binding. A two-stage case-control study, including 1595 HBV-persistent carriers and 1590 subjects with HBV natural clearance, was conducted to examine the associations between candidate variants and susceptibility to persistent HBV infection. Biological assays were carried out to elucidate the underlying mechanism of the associated genetic variants.

RESULTS

Twelve candidate variants were identified, and rs2523454 G > A increased the risk of persistent HBV infection (dominant model: ORcombined  = 1.37, 95% CI = 1.19-1.58, P = 1.610 × 10-5 ). Functional assays indicated that the rs2523454 A allele significantly decreased transcriptional activity compared to the G allele by influencing TF-binding affinity. In addition, expression quantitative trait loci analyses revealed that the A allele was associated with the reduced expression of MICA (P < 0.01).

CONCLUSIONS

Our findings suggest that the germline G > A variation at rs2523454 may influence TF-DNA interaction, downregulate the expression of MICA and play an important role in the development of persistent HBV infection in the Chinese population.

EGF suppresses the expression of miR-124a in pancreatic β cell lines via ETS2 activation through the MEK and PI3K signaling pathways

Diabetes mellitus is characterized by pancreatic β cell dysfunction. Previous studies have indicated that epidermal growth factor (EGF) and microRNA-124a (miR-124a) play opposite roles in insulin biosynthesis and secretion by beta cells. However, the underlying mechanisms remain poorly understood. In the present study, we demonstrated that EGF could inhibit miR-124a expression in beta cell lines through downstream signaling pathways, including mitogen-activated protein kinase kinase (MEK) and phosphatidylinositol 3-kinase (PI3K) cascades. Further, the transcription factor ETS2, a member of the ETS (E26 transformation-specific) family, was identified to be responsible for the EGF-mediated suppression of miR-124a expression, which was dependent on ETS2 phosphorylation at threonine 72. Activation of ETS2 decreased miR-124a promoter transcriptional activity through the putative conserved binding sites AGGAANA/TN in three miR-124a promoters located in different chromosomes. Of note, ETS2 played a positive role in regulating beta cell function-related genes, including miR-124a targets, Forkhead box a2 (FOXA2) and Neurogenic differentiation 1 (NEUROD1), which may have partly been through the inhibition of miR-124 expression. Knockdown and overexpression of ETS2 led to the prevention and promotion of insulin biosynthesis respectively, while barely affecting the secretion ability. These results suggest that EGF may induce the activation of ETS2 to inhibit miR-124a expression to maintain proper beta cell functions and that ETS2, as a novel regulator of insulin production, is a potential therapeutic target for diabetes mellitus treatment.

Integration of Wnt and FGF signaling in the Xenopus gastrula at TCF and Ets binding sites shows the importance of short-range repression by TCF in patterning the marginal zone

During Xenopus gastrulation, Wnt and FGF signaling pathways cooperate to induce posterior structures. Wnt target expression around the blastopore falls into two main categories: a horseshoe shape with a dorsal gap, as in Wnt8 expression; or a ring, as in FGF8 expression. Using ChIP-seq, we show, surprisingly, that the FGF signaling mediator Ets2 binds near all Wnt target genes. However, β-catenin preferentially binds at the promoters of genes with horseshoe patterns, but further from the promoters of genes with ring patterns. Manipulation of FGF or Wnt signaling demonstrated that 'ring' genes are responsive to FGF signaling at the dorsal midline, whereas 'horseshoe' genes are predominantly regulated by Wnt signaling. We suggest that, in the absence of active β-catenin at the dorsal midline, the DNA-binding protein TCF binds and actively represses gene activity only when close to the promoter. In contrast, genes without functional TCF sites at the promoter may be predominantly regulated by Ets at the dorsal midline and are expressed in a ring. These results suggest recruitment of only short-range repressors to potential Wnt targets in the Xenopus gastrula.

The Transcription Factor Elf3 Is Essential for a Successful Mesenchymal to Epithelial Transition

The epithelial to mesenchymal transition (EMT) and the mesenchymal to epithelial transition (MET) are two critical biological processes that are involved in both physiological events such as embryogenesis and development and also pathological events such as tumorigenesis. They present with dramatic changes in cellular morphology and gene expression exhibiting acute changes in E-cadherin expression. Despite the comprehensive understanding of EMT, the regulation of MET is far from being understood. To find novel regulators of MET, we hypothesized that such factors would correlate with Cdh1 expression. Bioinformatics examination of several expression profiles suggested Elf3 as a strong candidate. Depletion of Elf3 at the onset of MET severely impaired the progression to the epithelial state. This MET defect was explained, in part, by the absence of E-cadherin at the plasma membrane. Moreover, during MET, ELF3 interacts with the Grhl3 promoter and activates its expression. Our findings present novel insights into the regulation of MET and reveal ELF3 as an indispensable guardian of the epithelial state. A better understanding of MET will, eventually, lead to better management of metastatic cancers.

FGF Signaling Directs the Cell Fate Switch from Neurons to Astrocytes in the Developing Mouse Cerebral Cortex

During mammalian neocortical development, neural precursor cells generate neurons first and astrocytes later. The cell fate switch from neurons to astrocytes is a key process generating proper numbers of neurons and astrocytes. Although the intracellular mechanisms regulating this cell fate switch have been well characterized, extracellular regulators are still largely unknown. Here, we uncovered that fibroblast growth factor (FGF) regulates the cell fate switch from neurons to astrocytes in the developing cerebral cortex using mice of both sexes. We found that the FGF signaling pathway is activated in radial glial cells of the ventricular zone at time points corresponding to the switch in cell fate. Our loss- and gain-of-function studies using in utero electroporation indicate that activation of FGF signaling is necessary and sufficient to change cell fates from neurons to astrocytes. We further found that the FGF-induced neuron-astrocyte cell fate switch is mediated by the MAPK pathway. These results indicate that FGF is a critical extracellular regulator of the cell fate switch from neurons to astrocytes in the mammalian cerebral cortex.SIGNIFICANCE STATEMENT Although the intracellular mechanisms regulating the neuron-astrocyte cell fate switch in the mammalian cerebral cortex during development have been well studied, their upstream extracellular regulators remain unknown. By using in utero electroporation, our study provides in vivo data showing that activation of FGF signaling is necessary and sufficient for changing cell fates from neurons to astrocytes. Manipulation of FGF signaling activity led to drastic changes in the numbers of neurons and astrocytes. These results indicate that FGF is a key extracellular regulator determining the numbers of neurons and astrocytes in the mammalian cerebral cortex, and is indispensable for the establishment of appropriate neural circuitry.

MicroRNA-146b Overexpression Promotes Human Bladder Cancer Invasion via Enhancing ETS2-Mediated mmp2 mRNA Transcription

Although microRNAs have been validated to play prominent roles in the occurrence and development of human bladder cancer (BC), alterations and function of many microRNAs (miRNAs) in bladder cancer invasion are not fully explored yet. miR-146b was reported to be a tumor suppressor or oncomiRNA in various types of cancer. However, its accurate expression, function, and mechanism in bladder cancer remain unclear. Here we discovered that miR-146b was frequently upregulated in bladder cancer tissues compared with adjacent non-cancerous tissues. Inhibition of miR-146b resulted in a significant inhibitory effect on the invasion of bladder cancer cells by reducing mmp2 mRNA transcription and protein expression. We further demonstrated that knockdown of miR-146b attenuated ETS2 expression, which was the transcription factor of matrix metalloproteinase (MMP)2. Moreover, mechanistic studies revealed that miR-146b inhibition stabilized ARE/poly(U)-binding/degradation factor 1 (auf1) mRNA by directly binding to its mRNA 3′ UTR, further reduced ets2 mRNA stability, and finally inhibited mmp2 transcription and attenuated bladder cancer invasion abilities. The identification of the miR-146b/AUF1/ETS2/MMP2 mechanism for promoting bladder cancer invasion provides significant insights into understanding the nature of bladder cancer metastasis. Targeting the pathway described here may be a novel approach for inhibiting invasion and metastasis of bladder cancer.

Crosstalk between p38 and Erk 1/2 in Downregulation of FGF1-Induced Signaling

Mitogen-activated protein kinases (MAPK): Erk1 and Erk2 are key players in negative-feedback regulation of fibroblast growth factor (FGF) signaling. Upon activation, Erk1 and Erk2 directly phosphorylate FGF receptor 1 (FGFR1) at a specific serine residue in the C-terminal part of the receptor, substantially reducing the tyrosine phosphorylation in the receptor kinase domain and its signaling. Similarly, active Erks can also phosphorylate multiple threonine residues in the docking protein FGF receptor substrate 2 (FRS2), a major mediator of FGFR signaling. Here, we demonstrate that in NIH3T3 mouse fibroblasts and human osteosarcoma U2OS cells stably expressing FGFR1, in addition to Erk1 and Erk2, p38 kinase is able to phosphorylate FRS2. Simultaneous inhibition of Erk1/2 and p38 kinase led to a significant change in the phosphorylation pattern of FRS2 that in turn resulted in prolonged tyrosine phosphorylation of FGFR1 and FRS2 and in sustained signaling, as compared to the selective inhibition of Erks. Furthermore, excessive activation of p38 with anisomycin partially compensated the lack of Erks activity. These experiments reveal a novel crosstalk between p38 and Erk1/2 in downregulation of FGF-induced signaling.

Elk1 affects katanin and spastin proteins via differential transcriptional and post-transcriptional regulations

Microtubule severing, which is highly critical for the survival of both mitotic and post-mitotic cells, has to be precisely adjusted by regulating the expression levels of severing proteins, katanin and spastin. Even though severing mechanism is relatively well-studied, there are limited studies for the transcriptional regulation of microtubule severing proteins. In this study, we identified the main regulatory region of KATNA1 gene encoding katanin-p60 as 5’ UTR, which has a key role for its expression, and showed Elk1 binding to KATNA1. Furthermore, we identified that Elk1 decreased katanin-p60 and spastin protein expressions, while mRNA levels were increased upon Elk1 overexpression. In addition, SUMOylation is a known post-translational modification regulating Elk1 activity. A previous study suggested that K230, K249, K254 amino acids in the R domain are the main SUMOylation sites; however, we identified that these amino acids are neither essential nor substantial for Elk1 SUMOylation. Also, we determined that KATNA1 methylation results in the reduction of Elk1 binding whereas SPG4 methylation does not. Together, our findings emphasizing the impacts of both transcriptional and post-transcriptional regulations of katanin-p60 and spastin suggest that Elk1 has a key role for differential expression patterns of microtubule severing proteins, thereby regulating cellular functions through alterations of microtubule organization.

The Transcription Factor ETV5 Mediates BRAFV600E-Induced Proliferation and TWIST1 Expression in Papillary Thyroid Cancer Cells

The ETS family of transcription factors is involved in several normal remodeling events and pathological processes including tumor progression. ETS transcription factors are divided into subfamilies based on the sequence and location of the ETS domain. ETV5 (Ets variant gene 5; also known as ERM) is a member of the PEA3 subfamily. Our meta-analysis of normal, benign, and malignant thyroid samples demonstrated that ETV5 expression is upregulated in papillary thyroid cancer and was predominantly associated with BRAF V600E or RAS mutations. However, the precise role of ETV5 in these lesions is unknown. In this study, we used the KTC1 cell line as a model for human advanced papillary thyroid cancer (PTC) because the cells harbor the heterozygous BRAF (V600E) mutation together with the C250T TERT promoter mutation. The role of ETV5 in PTC proliferation was tested using RNAi followed by high-throughput screening. Signaling pathways driving ETV5 expression were identified using specific pharmacological inhibitors. To determine if ETV5 influences the expression of epithelial-to-mesenchymal (EMT) markers in these cells, an EMT PCR array was used, and data were confirmed by qPCR and ChIP-qPCR. We found that ETV5 is critical for PTC cell growth, is expressed downstream of the MAPK pathway, and directly upregulates the transcription factor TWIST1, a known marker of intravasation and metastasis. Increased ETV5 expression could therefore be considered as a marker for advanced PTCs and a possible future therapeutic target.

Pea3 Transcription Factors, Etv4 and Etv5, Are Required for Proper Hippocampal Dendrite Development and Plasticity

The proper formation and morphogenesis of dendrites is essential to the establishment of neuronal connectivity. We report that 2 members of the Pea3 family of transcription factors, Etv4 and Etv5, are expressed in hippocampal neurons during the main period of dendritogenesis, suggesting that they have a function in dendrite development. Here, we show that these transcription factors are physiological regulators of growth and arborization of pyramidal cell dendrites in the developing hippocampus. Gain and loss of function assays indicate that Etv4 and Etv5 are required for proper development of hippocampal dendritic arbors and spines. We have found that in vivo deletion of either Etv4 or Etv5 in hippocampal neurons causes deficits in dendrite size and complexity, which are associated with impaired cognitive function. Additionally, our data support the idea that Etv4 and Etv5 are part of a brain-derived neurotrophic factor-mediated transcriptional program required for proper hippocampal dendrite connectivity and plasticity.

Down-regulation of ETS2 inhibits the invasion and metastasis of renal cell carcinoma cells by inducing EMT via the PI3K/Akt signaling pathway

V-ets erythroblastosis virus E26 oncogene homolog 2 (ETS2), belonging to the ETS family of transcription factors, is implicated in a broad range of cellular functions. Recently, ETS2 has been found playing an important role in the progression of some types of cancers. However, it remains unclear whether ETS2 has any effects on renal cell carcinoma (RCC). In this study, we investigated the biological functions of ETS2 in RCC. The results showed that ETS2 was highly expressed in RCC tissues and cell lines and its expression had an association with clinicopathological characteristics of RCC patients. In addition, down-regulation of ETS2 significantly inhibited RCC cell invasion in vitro and metastasis in vivo as well as suppressed the epithelial-mesenchymal transition (EMT) process. We also found that ETS2 down-regulation significantly reduced the levels of PI3K and Akt phosphorylation in RCC cells. Taken together, we suggest that ETS2 is of potential value as a molecular target for RCC treatment.

RALB provides critical survival signals downstream of Ras in acute myeloid leukemia

Mutations that activate RAS proto-oncogenes and their effectors are common in acute myeloid leukemia (AML); however, efforts to therapeutically target Ras or its effectors have been unsuccessful, and have been hampered by an incomplete understanding of which effectors are required for AML proliferation and survival. We investigated the role of Ras effector pathways in AML using murine and human AML models. Whereas genetic disruption of NRAS(V12) expression in an NRAS(V12) and Mll-AF9-driven murine AML induced apoptosis of leukemic cells, inhibition of phosphatidylinositol-3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) signaling did not reproduce this effect. Conversely, genetic disruption of RALB signaling induced AML cell death and phenocopied the effects of suppressing oncogenic Ras directly - uncovering a novel role for RALB signaling in AML survival. Knockdown of RALB led to decreased phosphorylation of TBK1 and reduced BCL2 expression, providing mechanistic insight into RALB survival signaling in AML. Notably, we found that patient-derived AML blasts have higher levels of RALB-TBK1 signaling compared to normal blood leukocytes, supporting a pathophysiologic role for RALB signaling for AML patients. Overall, our work provides new insight into the specific roles of Ras effector pathways in AML and has identified RALB signaling as a key survival pathway.

Increased expression of EHF contributes to thyroid tumorigenesis through transcriptionally regulating HER2 and HER3

E26 transformation-specific (ETS) transcription factor EHF plays a tumor suppressor role in prostate cancer and esophageal squamous cell carcinoma (ESCC), whereas it is overexpressed and may act as an oncogene in ovarian and mammary cancers. However, its biological role in thyroid cancer remains totally unknown. The aim of this study was to explore the biological functions of EHF and its potential as a therapeutic target in thyroid cancer. Using quantitative RT-PCR (qRT-PCR) assay, we evaluated mRNA expression of EHF in a cohort of primary papillary thyroid cancers (PTCs) and matched non-cancerous thyroid tissues. The functions of knockdown and ectopic expression of EHF in thyroid cancer cells were determine by a series of in vitro and in vivo experiments. Moreover, dual-luciferase reporter and chromatin immunoprecipitation (ChIP) assays were performed to identify its downstream targets. Our data showed that EHF expression was significantly increased in PTCs compared with matched non-cancerous thyroid tissues. EHF knockdown significantly inhibited thyroid cancer cell proliferation, colony formation, migration, invasion and tumorigenic potential in nude mice and induced cell cycle arrested and apoptosis by modulating the PI3K/Akt and MAPK/Erk signaling pathways. On the other hand, ectopic expression of EHF in thyroid cancer cells notably promoted cell growth and invasiveness. Importantly, EHF was identified as a new transcription factor for HER2 and HER3, contributing to thyroid tumorigenesis. Altogether, our findings suggest that EHF is a novel functional oncogene in thyroid cancer by transcriptionally regulating HER2 and HER3, and may represent a potential therapeutic target for this cancer.

An oncogenic KRAS transcription program activates the RHOGEF ARHGEF2 to mediate transformed phenotypes in pancreatic cancer

Activating mutations of KRAS are nearly ubiquitous in pancreatic adenocarcinomas occurring in greater than 90% of cases. Cellular transformation by oncogenic RAS requires the RHO guanine exchange factor ARHGEF2 (also known as GEF-H1) for tumor growth and survival. Here, we find oncogenic KRAS activates ARHGEF2 through a minimal RAS responsive promoter. We have determined the endogenous ARHGEF2 promoter is positively regulated by the transcription factors ELK1, ETS1, SP1 and SP3 and negatively regulated by the RAS responsive element binding protein (RREB1). We find that the panel of ARHGEF2-regulating transcription factors modulates RAS transformed phenotypes including cellular viability, anchorage-independent growth and invasion-migration of pancreatic cancer cells. RREB1 knockdown activates the amplitude and duration of RHOA via increased ARHGEF2 expression. By relieving the negative regulation of RREB1 on the ARHGEF2 promoter, we determined that ETS1 and SP3 are essential for the normal expression of ARHGEF2 and contribute to the migratory behavior of pancreatic cancer cells. Furthermore, enforced expression of ARHGEF2 rescues loss of SP3 driven invasion-migration and anchorage-independent growth defective phenotypes through restored activation of RHOA. Collectively, our results identify a transcription factor program required for RAS transformation and provide mechanistic insight into the highly metastatic behavior of pancreatic cancer.

Oral administration of Lentinus edodes β-glucans ameliorates DSS-induced ulcerative colitis in mice via MAPK-Elk-1 and MAPK-PPARγ pathways

To evaluate the anti-inflammatory effect of β-glucans from Lentinus edodes, and its molecular mechanism, the dextran sulfate sodium salt (DSS) induced colitis model of mice and the LPS-stimulated RAW264.7 cell inflammation model were used in this study. 40 ICR male mice were randomly divided into 4 groups: Control, DSS (DSS treated only), DSS + low-βGs (500 mg kg^-1 d^-1) and DSS + high-βGs (1000 mg kg^-1 d^-1). The body weight of the mice with Lentinus edodes β-glucan supplementation increased significantly compared to the DSS group and the disease activity index (DAI) was improved in both βG-treated groups. Compared with the DSS group, histopathological analysis showed that the infiltration of inflammatory cells of both βG-treated groups decreased significantly in colonic tissues. Furthermore, oral administration of β-glucans decreases the concentration of malondialdehyde (MDA) and myeloperoxidase (MPO) and inhibits the expression of iNOS and several inflammatory factors: TNF-α, IL-1β and IL-6 as well as nitric oxide (NO) of the colonic tissues. The mitogen-activated protein kinase (MAPK) pathway is closely related to the expression of pro-inflammatory factors. In the DSS-induced colitis model and the LPS-stimulated RAW264.7 cell model, βGs inhibited the expression of pro-inflammatory factors and blocked the phosphorylation of JNK/ERK1/2 and p38; βGs also suppress the phosphorylation of Elk-1 at Ser84 and the phosphorylation of PPARγ at Ser112. Altogether, these results suggest that Lentinus edodes βGs could inhibit the DSS-induced ulcerative colitis and decrease inflammatory factor expressions. The molecular mechanism may be involved in suppressing MAPK signaling and inactivation of Elk-1 and activation of PPARγ.

Fibroblast growth factors in the management of spinal cord injury

Spinal cord injury (SCI) possesses a significant health and economic burden worldwide. Traumatic SCI is a devastating condition that evolves through two successive stages. Throughout each of these stages, disturbances in ionic homeostasis, local oedema, ischaemia, focal haemorrhage, free radicals stress and inflammatory response were observed. Although there are no fully restorative cures available for SCI patients, various molecular, cellular and rehabilitative therapies, such as limiting local inflammation, preventing secondary cell death and enhancing the plasticity of local circuits in the spinal cord, were described. Current preclinical studies have showed that fibroblast growth factors (FGFs) alone or combination therapies utilizing cell transplantation and biomaterial scaffolds are proven effective for treating SCI in animal models. More importantly, some studies further demonstrated a paucity of clinical transfer usage to promote functional recovery of numerous patients with SCI. In this review, we focus on the therapeutic capacity and pitfalls of the FGF family and its clinical application for treating SCI, including the signalling component of the FGF pathway and the role in the central nervous system, the pathophysiology of SCI and the targets for FGF treatment. We also discuss the challenges and potential for the clinical translation of FGF-based approaches into treatments for SCI.

Pravastatin attenuates the action of the ETS domain-containing protein ELK1 to prevent atherosclerosis in apolipoprotein E-knockout mice via modulation of extracellular signal-regulated kinase 1/2 signal pathway

Oxidative stress plays an important role in atherosclerosis, a vascular disease with high morbidity and mortality. The ETS domain-containing protein ELK1 is an oxidative stress-sensitive factor modulated by the extracellular signal-regulated kinase (ERK) 1/2 pathway. However, the role of ELK1 in the prevention of atherosclerosis by pravastatin remains unclear. In the present study, male apolipoprotein E-knockout (apoE^-/- ) mice fed a diet containing 1.25% cholesterol (w/w) were divided into two groups, one treated with pravastatin (80 mg/kg, 2-2.4 mg/mouse per day) for 8 weeks and the other not. Male C57BL/6J mice fed with a normal diet were used as a control group. Human umbilical vein endothelial cells (HUVEC) were cultured and treated with pravastatin (10 μmol/L) for 18 hours before testing for the presence or absence of 100 μmol/L H₂ O₂ (24 hours). Examination of pathological sections from mice aortas revealed that pravastatin treatment almost prevented atherosclerotic plaque formation. Pravastatin also inhibited increases in serum and aortic levels of oxidized low-density lipoprotein and aortic malondialdehyde levels and decreases in aortic reduced glutathione, and the activities of superoxide dismutase, catalase and glutathione peroxidase. H₂ O₂ -induced increases in reactive oxygen species in HUVECs were reversed by pravastatin by 48%. Pravastatin blocked the phosphorylation of ELK1 and ERK1/2 proteins and reduced mRNA levels of early growth response 1, a known atherogenic transcription factor upregulated by the ROS/ERK/ELK1 pathway, in mice. In conclusion, pravastatin attenuates the action of ELK1 induced by oxidative stress to prevent atherosclerosis, which is dependent partly on modulation of ERK1/2 signalling.