Signal-dependent Elk-1 target genes involved in transcript processing and cell migration

Riddle of the Sphinx: Emerging role of circular RNAs in cervical cancer

Cervical cancer is a prominent cause of cancer-related mortality among women, with recent attention directed toward exploring the involvement of circular RNAs (circRNAs) in this particular cancer. CircRNAs, characterized by a covalently closed loop structure, belong to a class of single-stranded non-coding RNA (ncRNA) molecules that play crucial roles in cancer development and progression through diverse mechanisms. The abnormal expression of circRNAs in vivo is significantly associated with the development of cervical cancer. Notably, circRNAs actively interact with miRNAs in cervical cancer, leading to the regulation of diverse signaling pathways, and they can contribute to cancer hallmarks such as self-sufficiency in growth signals, insensitivity to antigrowth signals, limitless proliferation, evading apoptosis, tissue invasion and metastasis, and sustained angiogenesis. Moreover, the distinctive biomedical attributes exhibited by circRNAs, including their abundance, conservation, and stability in body fluids, position them as promising biomarkers for various cancers. In this review, we elucidate the tremendous potential of circRNAs as diagnostic markers or therapeutic targets in cervical cancer by expounding upon their biogenesis, characteristics, functions, and databases, highlighting the novel advances in the signaling pathways associated with circRNAs in cervical cancer.

Xiaozheng pill exerts an anti-mammary hyperplasia effect through Raf/ERK/ELK and HIF-1α/bFGF pathways

Background and aim

The purpose of this study is to explore whether the Xiaozheng pill (XZP) has the effect of anti-hyperplasia of mammary glands (HMG) and to identify the related signaling pathways.

Experimental procedure

We analyzed the effective chemical components of the XZP, as well as the key chemical components, key proteins, main biological processes, and pathways in the treatment of HMG; Secondly, the levels of Estradiol (E2), Follicle-stimulating hormone (FSH), Luteinizing hormone (LH), Progesterone (P), Raf/ERK/ELK and HIF-1α/bFGF pathways related proteins were detected; Finally, the effect of XZP on metabolites was analyzed by metabolomics.

Results and conclusion

In this study, we identified key targets and pathways for XZP therapy of HMG, including EGFR, VEGFA, ER, and Ras signaling pathways. Animal experiments show that XZP can reduce the levels of E2, LH, and FSH and increase the expression of P in HMG mice. XZP can restore the normal structure of breast tissue and reduce ERα, ERβ, and PR expression in breast tissue. In addition, metabolomics results show that XZP also regulates HMG metabolites, including HIF-1α and metabolic pathways. The Western blot results showed that XZP intervention can reduce the protein expression of p-Raf1, Raf1, p-ERK1/2, ERK1/2, ELK, HIF-1α, and bFGF in the breast tissue of HMG mice. XZP may eliminate abnormal breast hyperplasia through inhibition of apoptosis and angiogenesis, which may be linked with the regulation of the Raf/ERK/ELK and HIF-1α/bFGF signaling pathways in HMG mice. These results suggest that XZP treatment may be beneficial for the management of HMG.

C4orf19 inhibits colorectal cancer cell proliferation by competitively binding to Keap1 with TRIM25 via the USP17/Elk-1/CDK6 axis

Colorectal cancer (CRC) is one of the most common malignant tumors in the gastrointestinal tract, and has been attracted a great deal attention and extensive investigation due to its high morbidity and mortality rates. The C4orf19 gene encodes a protein with uncharacterized function. Our preliminary exploration of the TCGA database indicated that C4orf19 is markedly downregulated in CRC tissues in comparison to that observed in normal colonic tissues, suggesting its potential association with CRC behaviors. Further studies showed a significant positive correlation between C4orf19 expression levels and CRC patient prognosis. Ectopic expression of C4orf19 inhibited the growth of CRC cells in vitro and tumorigenic ability in vivo. Mechanistic studies showed that C4orf19 binds to Keap1 at near the Lys615, which prevents the ubiquitination of Keap1 by TRIM25, thus protecting the Keap1 protein from degradation. The accumulated Keap1 results in USP17 degradation and in turn leading to the degradation of Elk-1, further attenuates its regulated CDK6 mRNA transcription and protein expression, as well as its mediated proliferation of CRC cells. Collectively, the present studies characterize function of C4orf19 as a tumor suppressor for CRC cell proliferation by targeting Keap1/USP17/Elk-1/CDK6 axis.

Baicalin Inhibits Airway Smooth Muscle Cells Proliferation through the RAS Signaling Pathway in Murine Asthmatic Airway Remodeling Model

Background

Studies that looked at asthma airway remodeling pathogenesis and prevention have led to the discovery of the rat sarcoma viral oncogene (RAS) signaling pathway as a key mechanism that controls airway smooth muscle cell (ASMC) proliferation. Baicalin has great anti-inflammatory, proliferation-inhibited, and respiratory disease-relieving properties. However, the inhibitory effects and mechanisms of baicalin on ASMC-mediated airway remodeling in mice are still poorly understood.

Methods

After establishing the asthmatic mice model by ovalbumin (OVA) and interfering with baicalin, airway remodeling characteristics such as airway resistance, mRNA, and protein expression levels of remodeling-related cytokines were measured by histopathological assessment, quantitative real-time polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and western blot. Further efforts on detailed mechanisms were used antibody arrays to compare the expression and activation of proteins involved in the RAS signaling pathway. In addition, validation experiments were performed in ASMC proliferation model and low-expression cells of the target gene by using shRNA.

Results

In OVA-induced asthmatic mice model, baicalin significantly reduced the infiltration of inflammatory cells in lung tissue, attenuated airway resistance, and decreased mRNA and protein expression levels of remodeling-related cytokines such as interleukin-13 (IL-13), vascular endothelial growth factor (VEGF), transforming growth factor-beta 1 (TGF-β1), matrix metallopeptidase 9 (MMP9), and tissue inhibitor of metalloproteinase 1 (TIMP1). The results of antibody arrays involved in RAS signaling pathway revealed that OVA and baicalin administration altered the activation of protein kinase C alpha type (PKC-α), A-rapidly accelerated fibrosarcoma (A-RAF), mitogen-activated protein kinase 2 (MEK2), extracellular regulated MAP kinase (ERK), MAPK interacting serine/threonine kinase 1 (MNK1), and ETS transcription factor 1 (ELK1). The above results were further verified in the ASMC proliferation model. A-RAF silencing (shA-RAF) could promote ASMC proliferation and downregulate p-MEK2, p-ERK, p-MNK1, and p-ELK1 expression.

Conclusion

The effects of baicalin against airway remodeling and ASMC proliferation might partially be achieved by suppressing the RAS signaling pathway. Baicalin may be a new therapeutic option for managing airway remodeling in asthma patients.

Di-2-ethylhexyl phthalate affects zinc metabolism and neurogenesis in the developing rat brain

We previously observed that developmental marginal zinc deficiency affects neurogenesis. Maternal phthalate exposure could disrupt fetal zinc homeostasis by triggering an acute phase response, causing maternal liver zinc retention that limits zinc availability to the fetus. Thus, we currently investigated whether exposure to di-2-ethylhexyl phthalate (DEHP) during gestation in rats alters fetal brain neurogenesis by impairing zinc homeostasis. Dams consumed an adequate (25 μg zinc/g diet) (C) or a marginal zinc deficient (MZD) (10 μg zinc/g diet) diet, without or with DEHP (300 mg/kg BW) (C + DEHP, MZD + DEHP) from embryonic day (E) 0 to E19. To evaluate neurogenesis we measured parameters of neural progenitor cells (NPC) proliferation and differentiation. Maternal exposure to DEHP and/or zinc deficiency lowered fetal brain cortical tissue (CT) zinc concentrations. Transcription factors involved in NPC proliferation (PAX6, SOX2, EMX1), differentiation (TBR2, TBR1) and mature neurons (NeuN) were lower in MZD, MZD + DEHP and C + DEHP than in C E19 brain CT, being the lowest in the MZD + DEHP group. VGLUT1 levels, a marker of glutamatergic neurons, showed a similar pattern. Levels of a marker of GABAergic neurons, GAD65, did not vary among groups. Phosphorylated ERK1/2 levels were reduced by both MZD and DEHP, and particularly in the MZD + DEHP group. MEHP-treated human neuroblastoma IMR-32 cells and E19 brains from DEHP-treated dams showed that the zinc-regulated phosphatase PP2A can be in part responsible for DEHP-mediated ERK1/2 downregulation and impaired neurogenesis. Overall, gestational exposure to DEHP caused secondary zinc deficiency and impaired neurogenesis. These harmful effects could have long-term consequences on the adult offspring brain structure and function.

ELK1 Promotes Epithelial-Mesenchymal Transition and the Progression of Lung Adenocarcinoma by Upregulating B7-H3

In previous studies, we found that B7 homolog 3 (B7-H3) was highly expressed in lung adenocarcinoma (LUAD) and promoted epithelial-to-mesenchymal transition (EMT) of LUAD cells. However, the underlying molecular mechanism is unclear. This study is aimed at evaluating the role of Ets-like protein 1 (ELK1) as a transcriptional regulator of B7-H3 for mediating the development and progression of LUAD in vitro and in vivo. We confirmed that ELK1 is highly expressed in LUAD and is associated with poor patient prognosis. ELK1 was found to promote proliferation, invasion, migration, and EMT of LUAD cells through in vivo and in vitro experiments. In terms of mechanism, ELK1 binds to the B7-H3 promoter region and induces the upregulation of B7-H3 in LUAD. Our data suggest that ELK1 plays an important role in the development of LUAD and could be used as a prognostic marker and therapeutic target for LUAD.

β-Neoendorphin Enhances Wound Healing by Promoting Cell Migration in Keratinocyte

The skin is the largest and a remarkably plastic organ that serves as a protective barrier against environmental stimuli and injuries throughout life. Skin injuries are serious health problems, and wound healing is a critical process to replace devitalized cellular and tissue structures. Although some endogenous opioids are known to be involved in the modulation of wound healing, it remains to be determined whether the β-neoendorphin (β-NEP), an endogenous opioid, has beneficial effects on wound repair in human keratinocyte. In this study, we found that β-NEP accelerated wound repair through activation of mitogen-activated protein kinase (MAPK)/Erk1/2 signaling pathways in human keratinocytes. Moreover, the wound healing effect of β-NEP is mainly through the acceleration of keratinocyte migration without affecting cell proliferation. Therefore, our studies reveal that β-NEP plays an important role in the regulation of wound repair and suggest a therapeutic strategy to promote wound healing using β-NEP.

USP9X promotes the proliferation, invasion and metastasis of liver cancer cells through regulating the JAK2/STAT3 signaling

X-linked ubiquitin-specific peptidase 9 (USP9X) serves important roles in the development and progression of various human cancers. However, its role and molecular mechanism in liver cancer require further elucidation. In the present study, USP9X was found to be upregulated in liver cancer tissues. At the same time, overexpression of USP9X promoted the proliferation, invasiveness and migration of liver cancer cells, which were subsequently suppressed by USP9X silencing. On a molecular level, the results revealed that USP9X knockdown suppressed elements of the Janus kinase 2 (JAK2)/STAT3 signaling pathway, including JAK2, STAT3, matrix metalloproteinase-2 and c-Myc. By contrast, overexpression of USP9X had the opposite effect. In conclusion, the results of the present study suggest that USP9X is upregulated in patients with liver cancer, which may accelerate the proliferation, invasiveness and migration of liver cancer cells by regulating the JAK2/STAT3 signaling pathway.

SOX18 promotes gastric cancer metastasis through transactivating MCAM and CCL7

The therapeutic strategies for advanced gastric cancer (GC) remain unsatisfying and limited. Therefore, it is still imperative to fully elucidate the mechanisms underlying GC metastasis. Here, we report a novel role of SRY-box transcription factor 18 (SOX18), a member of the SOX family, in promoting GC metastasis. The elevated expression of SOX18 was positively correlated with distant metastasis, higher AJCC stage, and poor prognosis in human GC. SOX18 expression was an independent and significant risk factor for the recurrence and survival in GC patients. Up-regulation of SOX18 promoted GC invasion and metastasis, whereas down-regulation of SOX18 decreased GC invasion and metastasis. Melanoma cell adhesion molecule (MCAM) and C-C motif chemokine ligand 7 (CCL7) are direct transcriptional targets of SOX18. Knockdown of MCAM and CCL7 significantly decreased SOX18-mediated GC invasion and metastasis, while the stable overexpression of MCAM and CCL7 reversed the decrease in cell invasion and metastasis that was induced by the inhibition of SOX18. A mechanistic investigation indicated that the upregulation of SOX18 that was mediated by the CCL7-CCR1 pathway relied on the ERK/ELK1 pathway. SOX18 knockdown significantly reduced CCL7-enhanced GC invasion and metastasis. Furthermore, BX471, a specific CCR1 inhibitor, significantly reduced the SOX18-mediated GC invasion and metastasis. In human GC tissues, SOX18 expression was positively correlated with CCL7 and MCAM expression, and patients with positive coexpression of SOX18/CCL7 or SOX18/MCAM had the worst prognosis. In conclusion, we defined a CCL7-CCR1-SOX18 positive feedback loop that played a pivotal role in GC metastasis, and targeting this pathway may be a promising therapeutic option for the clinical management of GC.

Elk-1 transcriptionally regulates ZC3H4 expression to promote silica-induced epithelial-mesenchymal transition

The epithelial-mesenchymal transition (EMT) process is a key priming activity of fibroblasts in pulmonary fibrosis during silicosis. Ets-like protein-1 (Elk-1) is a critical modulator that promotes functional changes in cells, and the effects are mediated by oxidative stress (OS). However, whether ELK-1 is involved in EMT of silicosis remains unclear. In addition, researchers have found that Elk-1 is involved in the expression of the gene zc3h12a, which encodes the protein MCPIP1, and MCPIP1 is a member of the zinc finger Cys-Cys-Cys-His (CCCH)-type protein family. A previous study from our lab showed that ZC3H4, which is also a member of the CCCH-type protein family, critically affected the regulation of EMT during silicosis. However, it has not yet been elucidated if ELK-1 acts at the promoter for zc3h4 to increase its expression in a mechanism that is similar to that of the zc3h12a gene and whether such regulation ultimately controls EMT. Therefore, we explored the correlation between ELK-1 and ZC3H4 expression and tested the underlying mechanisms affecting ELK-1 activation induced by silica. Our study identifies that SiO₂-mediated EMT via ELK-1, with the upstream activity of OS and the downstream signaling of ZC3H4 expression resulting in enhanced EMT. These findings suggest that the nuclear transcription factor ELK-1 may be useful as a novel target for the treatment of pulmonary fibrosis.

Hsa_circRNA_000166 Promotes Cell Proliferation, Migration and Invasion by Regulating miR-330-5p/ELK1 in Colon Cancer

INTRODUCTION

Circular RNAs (circRNAs), a novel class of non-coding RNAs, which are widely expressed in human cells, have essential roles in the development and progression of cancers. The aim of this study is to figure out the role of circ_000166 in colon cancer (CC) development and the signaling pathway involved.

MATERIALS AND METHODS

HT29 and HCT116 cells were transfected with siRNA of circRNA, miRNA mimics and inhibitors. Cell proliferation, migration and invasion were examined using CCK-8 assay and transwell assay, respectively. Luciferase reporter assay was used to validate the targets of circRNA and miRNA. CC cells were implanted into nude mice subcutaneously to detect tumor growth.

RESULTS

hsa_circRNA_000166 was significantly upregulated in the human CC tissue and in the CC cell lines. Knockdown of hsa_circRNA_000166 reduced cell viability, colony formation, migration and invasion in vitro and decreased tumor size and weight in vivo. Luciferase reporter assay revealed that miR-330-5p was the target of circRNA_000166. miR-330-5p could bind to 3' untranslated region (3'UTR) of ELK1 to downregulate both mRNA and protein expression of ELK1. Dual inhibition of circRNA_000166 and miR-330-5p inhibited the suppression of cell proliferation, migration and invasion induced by si-circRNA_000166.

CONCLUSION

The data of this study demonstrated that the hsa_circRNA_000166 could upregulated the expression of gene ELK1 by sponging miR-330-5p, which may contribute to a better understanding of the regulatory circRNA/miRNA/mRNA network and CC pathogenesis.

Circular RNA hsa_circ_0000515 acts as a miR-326 sponge to promote cervical cancer progression through up-regulation of ELK1

This study investigates the role of circular RNA (circRNA) hsa_circ_0000515 in cervical cancer and the underlying mechanism associated with microRNA-326 (miR-326). hsa_circ_0000515 and ETS transcription factor ELK1 (ELK1) were initially over-expressed and miR-326 was down-regulated in cervical cancer tissues and cells. Low hsa_circ_0000515 expression was found to be associated with favorable prognosis of patients with cervical cancer. A series of mimics, inhibitors, over-expression plasmids or siRNAs were introduced into cervical cancer cells to alter the expression of hsa_circ_0000515, miR-326 and ELK1. In vitro experiments exhibited that silencing of hsa_circ_0000515 or upregulation of miR-326 resulted in suppressed proliferation and invasion, along with induced apoptosis and autophagy of cervical cancer cells. Dual-luciferase reporter assay, RNA pull-down and RIP assays highlighted that hsa_circ_0000515 was able to act as a ceRNA of miR-326 to increase ELK1. Furthermore, enhancement of ELK1 expression resulted in enhanced proliferation and invasion but repressed apoptosis and autophagy of cervical cancer cells. In vivo experiments further confirmed the suppressed tumor growth by hsa_circ_0000515 silencing. Our findings demonstrated that hsa_circ_0000515 acts as a tumor promoter in cervical cancer. The study provides evidence for targeting hsa_circ_0000515 for therapeutic purposes in treating cervical cancer.

Protein inhibitor of activated STAT1 Ser503 phosphorylation-mediated Elk-1 SUMOylation promotes neuronal survival in APP/PS1 mice

BACKGROUND AND PURPOSE

Protein inhibitor of activated STAT1 (PIAS1) is phosphorylated by IKKα at Ser⁹⁰ in a PIAS1 E3 ligase activity-dependent manner. Whether PIAS1 is also phosphorylated at other residues and the functional significance of these additional phosphorylation events are not known. The transcription factor Elk-1 remains SUMOylated under basal conditions, but the role of Elk-1 SUMOylation in brain is unknown. Here, we examined the functional significance of PIAS1-mediated Elk-1 SUMOylation in Alzheimer's disease (AD) using the APP/PS1 mouse model of AD and amyloid β (Aβ) microinjections in vivo.

EXPERIMENTAL APPROACH

Novel phosphorylation site(s) on PIAS1 were identified by LC-MS/MS, and MAPK/ERK-mediated phosphorylation of Elk-1 demonstrated using in vitro kinase assays. Elk-1 SUMOylation by PIAS1 in brain was determined using in vitro SUMOylation assays. Apoptosis in hippocampus was assessed by measuring GADD45α expression by western blotting, and apoptosis of hippocampal neurons in APP/PS1 mice was assessed by TUNEL assay.

KEY RESULTS

Using LC-MS/MS, we identified a novel MAPK/ERK-mediated phosphorylation site on PIAS1 at Ser⁵⁰³ and showed this phosphorylation determines PIAS1 E3 ligase activity. In rat brain, Elk-1 was SUMOylated by PIAS1, which decreased Elk-1 phosphorylation and down-regulated GADD45α expression. Moreover, lentiviral-mediated transduction of Elk-1-SUMO1 reduced the number of hippocampal apoptotic neurons in APP/PS1 mice.

CONCLUSIONS AND IMPLICATIONS

MAPK/ERK-mediated phosphorylation of PIAS1 at Ser⁵⁰³ determines PIAS1 E3 ligase activity. Moreover, PIAS1 mediates SUMOylation of Elk-1, which functions as an endogenous defence mechanism against Aβ toxicity in vivo. Targeting Elk-1 SUMOylation could be considered a novel therapeutic strategy against AD.

Suppression of lymphocyte apoptosis in spleen by CXCL13 after porcine circovirus type 2 infection and regulatory mechanism of CXCL13 expression in pigs

Porcine circovirus-associated disease (PCVAD) is one of the most serious infectious diseases in pigs worldwide. The primary causative agent of PCVAD is porcine circovirus type 2 (PCV2), which can cause lymphoid depletion and immunosuppression in pigs. Our previous study demonstrated that Laiwu (LW) pigs, a Chinese indigenous pig breed, have stronger resistance to PCV2 infection than Yorkshire × Landrace (YL) pigs. In this study, we found that the YL pigs showed more severe lymphocyte apoptosis and higher viral load in the spleen tissue than LW pigs. To illustrate the differential gene expression between healthy and infected spleens, transcriptome profiling of spleen tissues from PCV2-infected and control YL pigs was compared by RNA sequencing. A total of 90 differentially expressed genes (DEGs) was identified, including CD207, RSAD2, OAS1, OAS2, MX2, ADRB3, CXCL13, CCR1, and ADRA2C, which were significantly enriched in gene ontology (GO) terms related to the defense response to virus and cell-cell signaling, and another nine DEGs, KLF11, HGF, PTGES3, MAP3K11, XDH, CYCS, ACTC1, HSPH1, and RYR2, which were enriched in GO terms related to regulation of cell proliferation or apoptosis. Among these DEGs, the CXCL13 gene, which can suppress lymphocyte apoptosis during PCV2 infection, was significantly down-regulated in response to PCV2 infection in YL but not in LW pigs. By analysis of the regulatory elements in the promoter and 3'-untranslated region (3'-UTR) of porcine CXCL13, we found that the single nucleotide polymorphism (SNP) -1014 G (LW) > A (YL) and the Sus scrofa microRNA-296-5p (ssc-miR-296-5p) participated in regulating CXCL13 expression during the response to PCV2 infection.

Targeting liver cancer stem cells for the treatment of hepatocellular carcinoma

Liver cancer is one of the most common malignant tumors and prognosis remains poor. It has been increasingly recognized that liver cancer stem cells (LCSCs) are responsible for the carcinogenesis, recurrence, metastasis and chemoresistance of hepatocellular carcinoma (HCC). Targeting LCSCs is promising to be a new direction for the treatment of HCC. Herein, we summarize the potentially therapeutic targets in LCSCs at the level of genes, molecules and cells, such as knockout of oncogenes or oncoproteins, restoring the silent tumor suppressor genes, inhibition of the transcription factors and regulation of noncoding RNAs (including microRNAs and long noncoding RNAs) in LCSCs at the genetic level; inhibition of markers and blockade of the key signaling pathways of LCSCs at the molecular level; and inhibiting autophagy and application of oncolytic adenoviruses in LCSCs at the cellular level. Moreover, we analyze the potential targets in LCSCs to eliminate chemoresistance of HCC. Thereinto, the suppression of autophagy and Nanog by chloroquine and shRNA respectively may be the most promising targeting approaches. These targets may provide novel therapeutic strategies for the treatment of HCC by targeting LCSCs.

Synergistic anti-inflammatory effects of quercetin and catechin via inhibiting activation of TLR4-MyD88-mediated NF-κB and MAPK signaling pathways

The synergistic anti-inflammatory effect of quercetin and catechin was investigated using lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. Results showed that the combined treatment of quercetin with catechin synergistically attenuated LPS-stimulated increase of some proinflammatory molecules, including nitric oxide, tumor necrosis factor α, interleukin-1β, nitric oxide synthase, and cyclooxygenase-2. Moreover, it exhibited significantly (p < 0.05) stronger inhibitory effect on nuclear translocation of nuclear factor-κB (NF-κB) by suppressing the phosphorylation of NF-κB p65 and p50 submits and on the phosphorylation of ETS domain-containing protein and c-Jun N-terminal kinase than any of quercetin or catechin alone. Besides, the cotreatment of quercetin with catechin significantly (p < 0.05) restored the impaired expression of toll-like receptor 4, myeloid differentiation primary response gene 88, and some downstream effectors (IRAK1, TRAF6, and TAK1). These results suggest that quercetin and catechin possessed synergistic anti-inflammatory effects, which may be attributed to their roles in suppressing the activation of TLR4-MyD88-mediated NF-κB and mitogen-activated protein kinases signaling pathways.

Stimulation of TRPM3 channels increases the transcriptional activation potential of Elk-1 involving cytosolic Ca2+, extracellular signal-regulated protein kinase, and calcineurin

Stimulation of transient receptor potential M3 (TRPM3) channels with the steroid pregnenolone sulfate increases the transcriptional activation potential of Elk-1, a transcription factor that regulates serum response element-mediated transcription. Here, we show that an influx of Ca²⁺ ions into the cells is essential for the activation of Elk-1 following stimulation of TRPM3. Using genetically encoded Ca²⁺ buffers, we show that a rise in cytoplasmic Ca²⁺ is required for the upregulation of the transcriptional activation potential of Elk-1, while buffering of Ca²⁺ in the nucleus had no inhibitory effect on the transcriptional activity of Elk-1. Pharmacological and genetic experiments showed that extracellular signal-regulated protein kinase (ERK1/2) functions as signal transducer connecting TRPM3 channels with the Elk-1 transcription factor. Accordingly, dephosphorylation of ERK1/2 in the nucleus by MAP kinase phosphatase attenuated TRPM3-mediated Elk-1 activation. Moreover, we show that the Ca²⁺/calmodulin-dependent protein phosphatase calcineurin is part of a shut-off-device for the signaling cascade connecting TRPM3 channels with the activation of Elk-1. The fact that TRPM3 channel stimulation activates Elk-1 connects TRPM3 with the biological functions of Elk-1, including the regulation of proliferation, differentiation, survival, transcription, and cell migration.

Cell Based-Green Fluorescent Biosensor Using Cytotoxic Pathway for Bacterial Lipopolysaccharide Recognition

Lipopolysaccharide (LPS), a characteristic component of the outer membrane of Gram-negative bacteria, can be used as an effective biomarker to detect bacterial contamination. Here, we reported a 293/hTLR4A-MD2-CD14 cell-based fluorescent biosensor to detect and identify LPS, which is carried out in a 96-well microplate which is nondestructive, user-friendly, and highly efficient. The promoter sequence of the critical signaling pathway gene ZC3H12A (encoding MCPIP1 protein) and enhanced green fluorescence protein (EGFP) were combined to construct a recombinant plasmid, which was transferred into 293/hTLR4A-MD2-CD14 cells through lipid-mediated, DNA-transfection way. LPS was able to bind to TLR4 and coreceptors-induced signaling pathway could result in green fluorescent protein expression. Results show that stable transfected 293/hTLR4A-MD2-CD14 cells with LPS treatment could be directly and continually observed under a high content screening imaging system. The novel cell-based biosensor detects LPS at low concentration, along with the detection limit of 0.075 μg/mL. The cell-based biosensor was evaluated by differentiating Gram-negative and Gram-positive bacteria and detecting LPS in fruit juices as well. This proposed fluorescent biosensor has potential in sensing LPS optically in foodstuff and biological products, as well as bacteria identification, contributing to the control of foodborne diseases and ensurance of public food safety with its high throughput detection way.

MTBP inhibits the Erk1/2-Elk-1 signaling in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and the prognosis of HCC patients, especially those with metastasis, remains extremely poor. This is partly due to unclear molecular mechanisms underlying HCC metastasis. Our previous study indicates that MDM2 Binding Protein (MTBP) suppresses migration and metastasis of HCC cells. However, signaling pathways regulated by MTBP remain unknown. To identify metastasis-associated signaling pathways governed by MTBP, we have performed unbiased luciferase reporter-based signal array analyses and found that MTBP suppresses the activity of the ETS-domain transcription factor Elk-1, a downstream target of Erk1/2 MAP kinases. MTBP also inhibits phosphorylation of Elk-1 and decreases mRNA expression of Elk-1 target genes. Reduced Elk-1 activity is caused by inhibited nuclear translocation of phosphorylated Erk1/2 (p-Erk) by MTBP and subsequent inhibition of Elk-1 phosphorylation. We also reveal that MTBP inhibits the interaction of p-Erk with importin-7/RanBP7 (IPO7), an importin family member which shuttles p-Erk into the nucleus, by binding to IPO7. Moreover, high levels of MTBP in human HCC tissues are correlated with cytoplasmic localization of p-Erk1/2. Our study suggests that MTBP suppresses metastasis, at least partially, by down-modulating the Erk1/2-Elk-1 signaling pathway, thus identifying a novel regulatory mechanism of HCC metastasis by regulating the subcellular localization of p-Erk.

Identification of Secretory Leukoprotease Inhibitor As an Endogenous Negative Regulator in Allergic Effector Cells

Mast cells, basophils, and eosinophils are central effectors in allergic inflammatory disorders. These cells secrete abundant serine proteases as well as chemical mediators and cytokines; however, the expression profiles and functions of their endogenous inhibitors remain elusive. We found that murine secretory leukoprotease inhibitor (SLPI) is expressed in basophils and eosinophils but in not in mast cells. SLPI-deficient (Slpi^−/−) basophils produce more cytokines than wild-type mice after IgE stimulation. Although the deletion of SLPI in basophils did not affect the release of chemical mediators upon IgE stimulation, the enzymatic activity of the serine protease tryptase was increased in Slpi^−/− basophils. Mice transferred with Slpi^−/− basophils were highly sensitive to IgE-mediated chronic allergic inflammation. Eosinophils lacking SLPI showed greater interleukin-6 secretion and invasive activity upon lipopolysaccharide stimulation, and the expression of matrix metalloproteinase-9 by these eosinophils was increased without stimulation. The absence of SLPI increases JNK1 phosphorylation at the steady state, and augments the serine phosphorylation of JNK1-downstream ETS transcriptional factor Elk-1 in eosinophils upon stimulation. Of note, SLPI interacts with a scaffold protein, JNK-interacting protein 3 (JIP3), that constitutively binds to the cytoplasmic domain of toll-like receptor (TLR) 4, suggesting that SLPI controls Elk-1 activation via binding to JIP3 in eosinophils. Mice transferred with Slpi^−/− eosinophils showed the exacerbation of chitin-induced allergic inflammation. These findings showed that SLPI is a negative regulator in allergic effector cells and suggested a novel inhibitory role of SLPI in the TLR4 signaling pathways.

Platelet-Derived Growth Factor Receptor α Contributes to Human Hepatic Stellate Cell Proliferation and Migration

Platelet-derived growth factor receptor α (PDGFRα), a tyrosine kinase receptor, is up-regulated in hepatic stellate cells (HSCs) during chronic liver injury. HSCs mediate hepatic fibrosis through their activation from a quiescent state partially in response to profibrotic growth factors. HSC activation entails enhanced expression of profibrotic genes, increase in proliferation, and increase in motility, which facilitates migration within the hepatic lobule. We show colocalization of PDGFRα in murine carbon tetrachloride, bile duct ligation, and 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine models of chronic liver injury, and investigate the role of PDGFRα on proliferation, profibrotic gene expression, and migration in primary human HSCs (HHSteCs) using the PDGFRα-specific inhibitory monoclonal antibody olaratumab. Although lacking any effects on HHSteC transdifferentiation assessed by gene expression of ACTA2, TGFB1, COL1A1, SYP1, and FN1, olaratumab specifically reduced HHSteC proliferation (AlamarBlue assay) and cell migration (transwell migration assays). Using phospho-specific antibodies, we show that olaratumab attenuates PDGFRα activation in response to PDGF-BB, and reduced phosphorylation of extracellular signal-regulated kinase 1 and 2, Elk-1, p38, Akt, focal adhesion kinase, mechanistic target of rapamycin, C10 regulator of kinase II, and C10 regulator of kinase-like, suggesting that PDGFRα contributes to mitogenesis and actin reorganization through diverse downstream effectors. Our findings support a distinct contribution of PDGFRα signaling to HSC proliferation and migration and provide evidence that inhibition of PDGFRα signaling could alter the pathogenesis of hepatic fibrosis.

FBXO25 regulates MAPK signaling pathway through inhibition of ERK1/2 phosphorylation

The FBXO25 mediates degradation of ELK-1 and thus inhibits transcriptional activation of immediate early genes (iEG). Here we show that FBXO25 regulates yet another node of this signaling pathway, by decreasing MAPK/ERK activity. We show that induction of FBXO25 reduced ERK1/2 phosphorylation independently of MEK1/2. Accordingly, in HAP1 FBXO25 knockout cells (FBXO25^KO), we observed that upon PMA treatment ERK1/2 was more active than in parental cells. An increase in cell proliferation under receptor mediated activation of the ERK signaling pathway in FBXO25^KO cells was also observed. Taken together we show that FBXO25 functions as a negative regulator of MAPK signaling though the reduction of ERK1/2 activation.

Lapatinib inhibits CIP2A/PP2A/p-Akt signaling and induces apoptosis in triple negative breast cancer cells

We tested the efficacy of lapatinib, a dual tyrosine kinase inhibitor which interrupts the HER2 and epidermal growth factor receptor (EGFR) pathways, in a panel of triple-negative breast cancer (TNBC) cells, and examined the drug mechanism. Lapatinib showed an anti-proliferative effect in HCC 1937, MDA-MB-468, and MDA-MB-231 cell lines. Lapatinib induced significant apoptosis and inhibited CIP2A and p-Akt in a dose and time-dependent manner in the three TNBC cell lines. Overexpression of CIP2A reduced lapatinib-induced apoptosis in MDA-MB-468 cells. In addition, lapatinib increased PP2A activity (in relation to CIP2A inhibition). Moreover, lapatinib-induced apoptosis and p-Akt downregulation was attenuated by PP2A antagonist okadaic acid. Furthermore, lapatinib indirectly decreased CIP2A transcription by disturbing the binding of Elk1 to the CIP2A promoter. Importantly, lapatinib showed anti-tumor activity in mice bearing MDA-MB-468 xenograft tumors, and suppressed CIP2A as well as p-Akt in these xenografted tumors. In summary, inhibition of CIP2A determines the effects of lapatinib-induced apoptosis in TNBC cells. In addition to being a dual tyrosine kinase inhibitor of HER2 and EGFR, lapatinib also inhibits CIP2A/PP2A/p-Akt signaling in TNBC cells.

Lurbinectedin Inactivates the Ewing Sarcoma Oncoprotein EWS-FLI1 by Redistributing It within the Nucleus

There is a great need to develop novel approaches to target oncogenic transcription factors with small molecules. Ewing sarcoma is emblematic of this need, as it depends on the continued activity of the EWS-FLI1 transcription factor to maintain the malignant phenotype. We have previously shown that the small molecule trabectedin interferes with EWS-FLI1. Here, we report important mechanistic advances and a second-generation inhibitor to provide insight into the therapeutic targeting of EWS-FLI1. We discovered that trabectedin functionally inactivated EWS-FLI1 by redistributing the protein within the nucleus to the nucleolus. This effect was rooted in the wild-type functions of the EWSR1, compromising the N-terminal half of the chimeric oncoprotein, which is known to be similarly redistributed within the nucleus in the presence of UV light damage. A second-generation trabectedin analogue lurbinectedin (PM01183) caused the same nuclear redistribution of EWS-FLI1, leading to a loss of activity at the promoter, mRNA, and protein levels of expression. Tumor xenograft studies confirmed this effect, and it was increased in combination with irinotecan, leading to tumor regression and replacement of Ewing sarcoma cells with benign fat cells. The net result of combined lurbinectedin and irinotecan treatment was a complete reversal of EWS-FLI1 activity and elimination of established tumors in 30% to 70% of mice after only 11 days of therapy. Our results illustrate the preclinical safety and efficacy of a disease-specific therapy targeting the central oncogenic driver in Ewing sarcoma. Cancer Res; 76(22); 6657-68. ©2016 AACR.

TEL2 suppresses metastasis by down-regulating SERPINE1 in nasopharyngeal carcinoma

Metastasis is the major cause of treatment failure in patients with nasopharyngeal carcinoma (NPC). However, the molecular mechanisms of NPC metastasis are poorly understood. Here, using our customized gene microarray containing all of the known human transcription factors and the current markers for epithelial-mesenchymal transition, we report that TEL2 was down-regulated in highly metastatic NPC cells and the metastatic tissues in lymph node. Mechanistically, TEL2 inhibits the cell migration and invasion in vitro and metastasis in vivo by releasing its direct suppression on the SERPINE1 promoter in NPC. Consistently, an inverse correlation was observed between the protein levels of TEL2 and SERPINE1 using clinical NPC samples. Collectively, we have provided the first evidence that TEL2 plays a key role in NPC metastasis by directly down-regulating SERPINE1, and that this novel axis of TEL2 / SERPINE1 may be valuable to develop new strategies for treating NPC patients with metastasis.

Vitamin D Control of Hematopoietic Cell Differentiation and Leukemia

It is now well known that in the mammalian body vitamin D is converted by successive hydroxylations to 1,25-dihydroxyvitamin D (1,25D), a steroid-like hormone with pleiotropic properties. These include important contributions to the control of cell proliferation, survival and differentiation, as well as the regulation of immune responses in disease. Here, we present recent advances in current understanding of the role of 1,25D in myelopoiesis and lymphopoiesis, and the potential of 1,25D and analogs (vitamin D derivatives; VDDs) for the control of hematopoietic malignancies. The reasons for the unimpressive results of most clinical studies of the therapeutic effects of VDDs in leukemia and related diseases may include the lack of a precise rationale for the conduct of these studies. Further, clinical trials to date have generally used extremely heterogeneous patient populations and, in many cases, small numbers of patients, generally without controls. Although low calcemic VDDs have been used and combined with agents that can increase the leukemia cell killing or differentiation effects in acute leukemias, the sequencing of agents used for combination therapy should to be more clearly delineated. Most importantly, it is recommended that in future clinical trials the rationale for the basis of the enhancing action of drug combinations should be clearly articulated and the effects on anticancer immunity should also be evaluated.

Serum Levels of IL-1 β , IL-6, TGF- β , and MMP-9 in Patients Undergoing Carotid Artery Stenting and Regulation of MMP-9 in a New In Vitro Model of THP-1 Cells Activated by Stenting

Inflammation plays an important role in the pathophysiological process after carotid artery stenting (CAS). Monocyte is a significant source of inflammatory cytokines in vascular remodeling. Telmisartan could reduce inflammation. In our study, we first found that, after CAS, the serum IL-1β, IL-6, TGF-β, and MMP-9 levels were significantly increased, but only MMP-9 level was elevated no less than 3 months. Second, we established a new in vitro model, where THP-1 monocytes were treated with the supernatants of human umbilical vein endothelial cells (HUVECs) that were scratched by pipette tips, which mimics monocytes activated by mechanical injury of stenting. The treatment enhanced THP-1 cell adhesion, migration and invasion ability, and the phosphorylation of ERK1/2 and Elk-1 and MMP-9 expression were significantly increased. THP-1 cells pretreated with PD98095 (ERK1/2 inhibitor) attenuated the phosphorylation of ERK1/2 and Elk-1 and upregulation of MMP-9, while pretreatment with telmisartan merely decreased the phosphorylation of Elk-1 and MMP-9 expression. These results suggested that IL-1β, IL-6, TGF-β, and MMP-9 participate in the pathophysiological process after CAS. Our new in vitro model mimics monocytes activated by stenting. MMP-9 expression could be regulated through ERK1/2/Elk-1 pathway, and the protective effects of telmisartan after stenting are partly attributed to its MMP-9 inhibition effects via suppression of Elk-1.

The Mediator complex: a central integrator of transcription

The RNA polymerase II (Pol II) enzyme transcribes all protein-coding and most non-coding RNA genes and is globally regulated by Mediator - a large, conformationally flexible protein complex with a variable subunit composition (for example, a four-subunit cyclin-dependent kinase 8 module can reversibly associate with it). These biochemical characteristics are fundamentally important for Mediator's ability to control various processes that are important for transcription, including the organization of chromatin architecture and the regulation of Pol II pre-initiation, initiation, re-initiation, pausing and elongation. Although Mediator exists in all eukaryotes, a variety of Mediator functions seem to be specific to metazoans, which is indicative of more diverse regulatory requirements.

The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web

The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies. Despite the advances, cases of drug resistance and recurrence of disease still remain a challenge to overcome. An important aspect for drug resistance is the complexity of the HER2 signaling network. This includes the crosstalk between HER2 and hormone receptors; its function as a transcription factor; the regulation of HER2 by protein-tyrosine phosphatases and a complex network of positive and negative feedback-loops. This review summarises the current knowledge of many different HER2 interactions to illustrate the complexity of the HER2 network from the transcription of HER2 to the effect of its downstream targets. Exploring the novel avenues of the HER2 signaling could yield a better understanding of treatment resistance and give rise to developing new and more effective therapies.

Cyr61 promotes epithelial-mesenchymal transition and tumor metastasis of osteosarcoma by Raf-1/MEK/ERK/Elk-1/TWIST-1 signaling pathway

Background

Osteosarcoma is the most common primary malignant tumor in children and young adults, and its treatment requires effective therapeutic approaches because of a high mortality rate for lung metastasis. Epithelial to mesenchymal transition (EMT) has received considerable attention as a conceptual paradigm for explaining the invasive and metastatic behavior during cancer progression. The cysteine-rich angiogenic inducer 61 (Cyr61) gene, a member of the CCN gene family, is responsible for the secretion of Cyr61, a matrix-associated protein that is involved in several cellular functions. A previous study showed that Cyr61 expression is related to osteosarcoma progression. In addition, Cyr61 could promote cell migration and metastasis in osteosarcoma. However, discussions on the molecular mechanism involved in Cyr61-regulated metastasis in osteosarcoma is poorly discussed.

Results

We determined that the expression level of Cyr61 induced cell migration ability in osteosarcoma cells. The Cyr61 protein promoted the mesenchymal transition of osteosarcoma cells by upregulating mesenchymal markers (TWIST-1 and N-cadherin) and inhibiting the epithelial marker (E-cadherin). Moreover, the Cyr61-induced cell migration was mediated by EMT. The Cyr61 protein elicited a signaling cascade that included αvβ5 integrin, Raf-1, mitogen-activated protein kinase (MEK), extracellular signal-regulated kinase (ERK), and Elk-1. The reagent or gene knockdown of these signaling proteins could inhibit Cyr61-promoted EMT in osteosarcoma. Finally, the knockdown of Cyr61 expression obviously inhibited cell migration and repressed mesenchymal phenotypes, reducing lung metastasis.

Conclusion

Our results indicate that Cyr61 promotes the EMT of osteosarcoma cells by regulating EMT markers via a signal transduction pathway that involves αvβ5 integrin, Raf-1, MEK, ERK, and Elk-1.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-236) contains supplementary material, which is available to authorized users.

Nutlin-3 induces BCL2A1 expression by activating ELK1 through the mitochondrial p53-ROS-ERK1/2 pathway

Nutlin-3 which occupies the p53 binding pocket in HDM2, has been reported to activate apoptosis through both the transcriptional activity-dependent and -independent programs of p53. Transcription-independent apoptosis by nutlin-3 is triggered by p53 which is translocated to mitochondria. However, we previously demonstrated that the nutlin-3-induced mitochondrial translocation of p53 stimulates ERK1/2 activation, an anti-apoptosis signal, via mitochondrial ROS generation. We report on how nutlin-3-stimulated ERK1/2 activity inhibits p53-induced apoptosis. Among the anti-apoptotic BCL2 family proteins, BCL2A1 expression was increased by nutlin-3 at both the mRNA and protein levels, and this increase was prevented by the inhibition of ERK1/2. TEMPO, a ROS scavenger, and PFT-μ , a blocker of the mitochondrial translocation of p53, also inhibited BCL2A1 expression as well as ERK1/2 phosphorylation. In addition, nutlin-3 stimulated phosphorylation of ELK1, which was prevented by all compounds that inhibited nutlin-3-induced ERK1/2 such as U0126, PFT-μ and TEMPO. Moreover, an increase in BCL2A1 expression was weakened by the knockdown of ELK1. Finally, nutlin-3-induced apoptosis was found to be potentiated by the knockdown of BCL2A1, as demonstrated by an increase of in hypo-diploidic cells and Annexin V-positive cells. Parallel to the increase in apoptotic cells, the knockdown of BCL2A1 augmented the cleavage of poly(ADP-ribose) polymerase-1. It is noteworthy that the augmented levels of apoptosis induced by the knockdown of BCL2A1 were comparable to those of apoptosis induced by U0126. Collectively, these results suggest that nutlin-3-activated ERK1/2 may stimulate the transcription of BCL2A1 via the activation of ELK1, and BCL2A1 expression may contribute to the inhibitory effect of ERK1/2 on nutlin-3-induced apoptosis, thereby constituting a negative feedback loop of p53-induced apoptosis.

Involvement of RECK in gambogic acid induced anti-invasive effect in A549 human lung carcinoma cells

Gambogic acid (GA), a xanthone derived from the resin of the Garcinia hanburyi, has been demonstrated possessing anti-metastatic activity in vitro and in vivo. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a membrane-anchored glycoprotein negatively regulating matrix metalloproteinases (MMPs), plays an important role in tumor invasion and metastasis. The present study investigates the regulatory effect of GA on RECK expression and the role of RECK in GA-induced anti-invasion in A549 human lung cancer cells. Our results showed that GA dose-dependently inhibited cell invasion and suppressed A549 experimental lung metastasis in vivo, which was attributed to RECK up-regulation at both protein and mRNA levels. With small interference RNA (siRNA) blocking RECK expression, we found inhibition of RECK decreased the GA-induced inhibition of MMP-2/9, which was in consistent with the attenuated anti-invasive effect of GA. Further study indicated that GA effectively suppressed Histone deacetylase (HDAC) 1/specificity protein (Sp) 1 binding and Sp1 phosphorylation associating with Extracellular signal-regulated kinases (ERK) signaling blocking, leading to RECK up-regulation. Taken together, these data demonstrate that RECK contributes to GA's anti-invasive activity and provide new evidence for GA being served as a therapeutic candidate for cancer metastasis.