Ets-related protein Elk-1 is homologous to the c-fos regulatory factor p62TCF

Leiomodin 2 neonatal dilated cardiomyopathy mutation results in altered actin gene signatures and cardiomyocyte dysfunction

Neonatal dilated cardiomyopathy (DCM) is a poorly understood muscular disease of the heart. Several homozygous biallelic variants in LMOD2, the gene encoding the actin-binding protein Leiomodin 2, have been identified to result in severe DCM. Collectively, LMOD2-related cardiomyopathies present with cardiac dilation and decreased heart contractility, often resulting in neonatal death. Thus, it is evident that Lmod2 is essential to normal human cardiac muscle function. This study aimed to understand the underlying pathophysiology and signaling pathways related to the first reported LMOD2 variant (c.1193 G > A, p.Trp398*). Using patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model harboring the homologous mutation to the patient, we discovered dysregulated actin-thin filament lengths, altered contractility and calcium handling properties, as well as alterations in the serum response factor (SRF)-dependent signaling pathway. These findings reveal that LMOD2 may be regulating SRF activity in an actin-dependent manner and provide a potential new strategy for the development of biologically active molecules to target LMOD2-related cardiomyopathies.

An integrated bioinformatic investigation of focal adhesion-related genes in glioma followed by preliminary validation of COL1A2 in tumorigenesis

Focal adhesions (FAs) allow cells to contact the extracellular matrix, helping to maintain tension and enabling signal transmission in cell migration, differentiation, and apoptosis. In addition, FAs are associated with changes in the tumor microenvironment (TME) that lead to malignant progression and drug resistance in tumors. However, there are still few studies on the comprehensive analysis of focal adhesion-related genes (FARGs) in glioma. Expression data and clinical information of glioma samples were downloaded from public databases. Two distinct molecular subtypes were identified based on FARGs using an unsupervised consensus clustering algorithm. A scoring system consisting of nine FARGs was constructed using integrated LASSO regression and multivariate Cox regression. It not only has outstanding prognostic value but also can guide immunotherapy of glioma patients, which was verified in TCGA, CGGA, GSE16011, and IMvigor210 cohorts. The results of bioinformatics analysis, immunohistochemistry staining, and western blotting all revealed that the expression of COL1A2 was up-regulated in glioblastoma and related to poor prognosis outcomes in patients from public datasets. COL1A2 promotes the proliferation, migration, and invasion of glioblastoma cells. A positive correlation between COL1A2 and CD8 was determined in GBM specimens from eight patients. Moreover, the results of cell co-cultured assay showed that COL1A2 participated in the killing of GBM cells by Jurkat cells. Our study indicates that the FARGs have prominent application value in the identification of molecular subtypes and prediction of survival outcomes in glioma patients. Bioinformatics analysis and experimental verification provide a direction for further research on FARGs.

GPX4 suppresses ferroptosis to promote malignant progression of endometrial carcinoma via transcriptional activation by ELK1

Background

Glutathione Peroxidase 4 (GPX4) is a key protein that inhibits ferroptosis. However, its biological regulation and mechanism in endometrial cancer (EC) have not been reported in detail.

Methods

The expression of GPX4 in EC tissues was determined by TCGA databases, qRT-PCR, Western blot, and immunohistochemistry (IHC). The effects of GPX4 on EC cell proliferation, migration, apoptosis, and tumorigenesis were studied in vivo and in vitro. In addition, ETS Transcription Factor ELK1 (ELK1) was identified by bioinformatics methods, dual-luciferase reporter assay, and chromatin immunoprecipitation (ChIP). Pearson correlation analysis was used to evaluate the association between ELK1 and GPX4 expression.

Results

The expression of GPX4 was significantly up-regulated in EC tissues and cell lines. Silencing GPX4 significantly inhibited the proliferation, migration ability, induced apoptosis, and arrested the cell cycle of Ishikawa and KLE cells. Knockdown of GPX4 accumulated intracellular ferrous iron and ROS, disrupted MMP, and increased MDA levels. The xenograft tumor model also showed that GPX4 knockdown markedly reduced tumor growth in mice. Mechanically, ELK1 could bind to the promoter of GPX4 to promote its transcription. In addition, the expression of ELK1 in EC was positively correlated with GPX4. Rescue experiments confirmed that GPX4 knockdown could reverse the strengthens of cell proliferation and migration ability and the lower level of Fe²⁺ and MDA caused by upregulating ELK1.

Conclusion

The results of the present study suggest that ELK1 / GPX4 axis plays an important role in the progress of EC by promoting the malignant biological behavior and inducing ferroptosis of EC cells, which provides evidence for investigating the potential therapeutic strategies of endometrial cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09986-3.

Regulation of c-Fos gene transcription by stimulus-responsive protein kinases

The basic region leucin zipper (bZIP) protein c-Fos constitutes together with other bZIP proteins the AP-1 transcription factor complex. Expression of the c-Fos gene is regulated by numerous extracellular signaling molecules including mitogens, metabolites, and ligands for receptor tyrosine kinases, G protein-coupled receptors, and cytokine receptors. Here, we analyzed the effects of the stimulus-responsive MAP kinases ERK1/2 (extracellular signal-regulated protein kinase), JNK (c-Jun N-terminal protein kinase) and p38 protein kinase on transcription of the c-Fos gene. We used chromatin-integrated c-Fos promoter-luciferase reporter genes containing inactivating point mutations of DNA binding sites for distinct transcription factors. ERK1/2, JNK, and p38 protein kinases were specifically activated following expression of either a mutant of B-Raf, a truncated version of mitogen-activated/extracellular signal responsive kinase kinase kinase-1 (MEKK1), or a mutant of MAP kinase kinase-6 (MKK6), respectively. The results show that the DNA binding sites for serum response factor (SRF) and for the ternary complex factor (TCF) are of major importance for stimulating c-Fos promoter activity by MAP kinases. ERK1/2 and p38-induced stimulation of the c-Fos promoter additionally required the DNA binding site for the transcription factor AP-1. Mutation of the DNA binding site for STAT had no or only a small effect on c-Fos promoter activity. We conclude that MAP kinases do not activate distinct transcription factors involving distinct genetic elements. Rather, these kinases mainly target SRF and TCF proteins, leading to an activation of transcription of the c-Fos gene via the serum response element.

β-Adrenergic signaling in skin cancer

Activation of the sympathetic nervous system releases catecholamines that can interact with β-adrenergic receptors on tumor cells. Preclinical models have shown that the signaling processes initiated by activation of β-adrenergic receptors increase tumorigenesis, stimulate cell proliferation, and inhibit apoptosis. Indeed, preclinical studies have also shown that β-adrenergic blockade can decrease tumor burden. Researchers have been studying the effects of β-adrenergic receptor blockers on tumor cells and how they may slow the progression of melanoma, basal cell carcinoma, and squamous cell carcinoma. Moreover, clinical data have shown improved prognosis in patients with skin cancer who take β-blockers. This review discusses the mechanisms of β-adrenergic signaling in cancer and immune cells, details preclinical models of sympathetic blockade, and considers clinical evidence of the effects of β-adrenergic blockade in skin cancers.

HTLV-1 intragenic viral enhancer influences immortalization phenotype in vitro, but is dispensable for persistence and disease development in animal models

Human T-cell leukemia virus type 1 (HTLV-1) is the causative infectious agent of adult T-cell leukemia/lymphoma (ATL) and chronic neurological disease. The disparity between silenced sense transcription versus constitutively active antisense (Hbz) transcription from the integrated provirus is not fully understood. The presence of an internal viral enhancer has recently been discovered in the Tax gene near the 3' long terminal repeat (LTR) of HTLV-1. In vitro, this enhancer has been shown to bind SRF and ELK-1 host transcription factors, maintain chromatin openness and viral gene transcription, and induce aberrant host gene transcription near viral integration sites. However, the function of the viral enhancer in the context of early HTLV-1 infection events remains unknown. In this study, we generated a mutant Enhancer virus (mEnhancer) and evaluated its effects on HTLV-1-mediated in vitro immortalization, establishment of persistent infection with an in vivo rabbit model, and disease development in a humanized immune system (HIS) mouse model. The mEnhancer virus was able to establish persistent infection in rabbits, and there were no significant differences in proviral load or HTLV-1-specific antibody responses over a 25-week study. However, rabbits infected with the mEnhancer virus had significantly decreased sense and antisense viral gene expression at 12-weeks post-infection. HIS mice infected with wt or mEnhancer virus showed similar disease progression, proviral load, and viral gene expression. While mEnhancer virus was able to sufficiently immortalize primary T-lymphocytes in cell culture, the immortalized cells had an altered phenotype (CD8⁺ T-cells), decreased proviral load, decreased sense and anti-sense gene expression, and altered cell cycle progression compared to HTLV-1.wt immortalized cells (CD4⁺ T-cells). These results suggest that the HTLV-1 enhancer element alone does not determine persistence or disease development but plays a pivotal role in regulating viral gene expression.

A PI3K inhibitor-induced growth inhibition of cancer cells is linked to MEK-ERK pathway

Phosphatidylinositol-4,5-bisphosphate 3-kinases (PI3Ks) regulate several important cellular and subcellular processes including cell proliferation and differentiation. LY294002 was originally reported to be a selective inhibitor of PI3K-Akt. Later, it showed that this compound also inhibits several other molecules. In this study, we investigated the effect of LY294002 on the growth of suspension (MV4-11 and TF-1a) and tissue (Hep-G2) cells. In exponential phase, MV4-11 cells, but not TF-1a and Hep-G2 cells, expressed a low level of PI3Kp85 and addition of LY294002 inhibited the phosphorylation of PI3Kp85. LY294002 also significantly inhibited the proliferation of MV4-11, TF-1a and Hep-G2 cell and caused formation of cell clusters/aggregates measured by MTT and BrdU assays, and observed under an inverted microscope, respectively. Surprisingly, we found that LY294002 markedly repressed the activation of mitogen-activated protein kinase (MAPK) signal molecules, MEK and ERK, in all these cells. The inhibition of MEK and ERK was confirmed by using MEK stimulators, GM-CSF and phorbol 12-myristate 13-acetate, and MEK-specific inhibitor, PD98059. Although transforming growth factor beta (TGFβ) also inhibited the growth of Hep-G2 cells, it had no effect on the activity of MEK and ERK. The clusters/aggregates found in LY294002-treated cells were not detectable in TGFβ-treated cells. Our data suggest that LY294002 may directly inhibit the activation of MEK and ERK by its ability to bind to the ATP-binding site of the MAPK molecules.

RAF-MEK-ERK pathway in cancer evolution and treatment

The RAF-MEK-ERK signaling cascade is a well-characterized MAPK pathway involved in cell proliferation and survival. The three-layered MAPK signaling cascade is initiated upon RTK and RAS activation. Three RAF isoforms ARAF, BRAF and CRAF, and their downstream MEK1/2 and ERK1/2 kinases constitute a coherently orchestrated signaling module that directs a range of physiological functions. Genetic alterations in this pathway are among the most prevalent in human cancers, which consist of numerous hot-spot mutations such as BRAF^V600E. Oncogenic mutations in this pathway often override otherwise tightly regulated checkpoints to open the door for uncontrolled cell growth and neoplasia. The crosstalk between the RAF-MEK-ERK axis and other signaling pathways further extends the proliferative potential of this pathway in human cancers. In this review, we summarize the molecular architecture and physiological functions of the RAF-MEK-ERK pathway with emphasis on its dysregulations in human cancers, as well as the efforts made to target the RAF-MEK-ERK module using small molecule inhibitors.

Regulation of Oncogenic Targets by the Tumor-Suppressive miR-139 Duplex (miR-139-5p and miR-139-3p) in Renal Cell Carcinoma

We previously found that both the guide and passenger strands of the miR-139 duplex (miR-139-5p and miR-139-3p, respectively) were downregulated in cancer tissues. Analysis of TCGA datasets revealed that low expression of miR-139-5p (p < 0.0001) and miR-139-3p (p < 0.0001) was closely associated with 5-year survival rates of patients with renal cell carcinoma (RCC). Ectopic expression assays showed that miR-139-5p and miR-139-3p acted as tumor-suppressive miRNAs in RCC cells. Here, 19 and 22 genes were identified as putative targets of miR-139-5p and miR-139-3p in RCC cells, respectively. Among these genes, high expression of PLXDC1, TET3, PXN, ARHGEF19, ELK1, DCBLD1, IKBKB, and CSF1 significantly predicted shorter survival in RCC patients according to TCGA analyses (p < 0.05). Importantly, the expression levels of four of these genes, PXN, ARHGEF19, ELK1, and IKBKB, were independent prognostic factors for patient survival (p < 0.05). We focused on PXN (paxillin) and investigated its potential oncogenic role in RCC cells. PXN knockdown significantly inhibited cancer cell migration and invasion, possibly by regulating epithelial-mesenchymal transition. Involvement of the miR-139-3p passenger strand in RCC molecular pathogenesis is a new concept. Analyses of tumor-suppressive-miRNA-mediated molecular networks provide important insights into the molecular pathogenesis of RCC.

Transcriptional and signalling regulation of skin epithelial stem cells in homeostasis, wounds and cancer

The epidermis and skin appendages are maintained by their resident epithelial stem cells, which undergo long-term self-renewal and multilineage differentiation. Upon injury, stem cells are activated to mediate re-epithelialization and restore tissue function. During this process, they often mount lineage plasticity and expand their fates in response to damage signals. Stem cell function is tightly controlled by transcription machineries and signalling transductions, many of which derail in degenerative, inflammatory and malignant dermatologic diseases. Here, by describing both well-characterized and newly emerged pathways, we discuss the transcriptional and signalling mechanisms governing skin epithelial homeostasis, wound repair and squamous cancer. Throughout, we highlight common themes underscoring epithelial stem cell plasticity and tissue-level crosstalk in the context of skin physiology and pathology.

Kras-Deficient T Cells Attenuate Graft-versus-Host Disease but Retain Graft-versus-Leukemia Activity

Acute graft-versus-host disease (aGVHD) is one major serious complication that is induced by alloreactive donor T cells recognizing host Ags and limits the success of allogeneic hematopoietic stem cell transplantation. In the current studies, we identified a critical role of Kras in regulating alloreactive T cell function during aGVHD. Kras deletion in donor T cells dramatically reduced aGVHD mortality and severity in an MHC-mismatched allogeneic hematopoietic stem cell transplantation mouse model but largely maintained the antitumor capacity. Kras-deficient CD4 and CD8 T cells exhibited impaired TCR-induced activation of the ERK pathway. Kras deficiency altered TCR-induced gene expression profiles, including the reduced expression of various inflammatory cytokines and chemokines. Moreover, Kras deficiency inhibited IL-6-mediated Th17 cell differentiation and impaired IL-6-induced ERK activation and gene expression in CD4 T cells. These findings support Kras as a novel and effective therapeutic target for aGVHD.

Expanding the Toolkit of Fluorescent Biosensors for Studying Mitogen Activated Protein Kinases in Plants

Mitogen-activated protein kinases (MAPKs) are key regulators of numerous biological processes in plants. To better understand the mechanisms by which these kinases function, high resolution measurement of MAPK activation kinetics in different biological contexts would be beneficial. One method to measure MAPK activation in plants is via fluorescence-based genetically-encoded biosensors, which can provide real-time readouts of the temporal and spatial dynamics of kinase activation in living tissue. Although fluorescent biosensors have been widely used to study MAPK dynamics in animal cells, there is currently only one MAPK biosensor that has been described for use in plants. To facilitate creation of additional plant-specific MAPK fluorescent biosensors, we report the development of two new tools: an in vitro assay for efficiently characterizing MAPK docking domains and a translocation-based kinase biosensor for use in plants. The implementation of these two methods has allowed us to expand the available pool of plant MAPK biosensors, while also providing a means to generate more specific and selective MAPK biosensors in the future. Biosensors developed using these methods have the potential to enhance our understanding of the roles MAPKs play in diverse plant signaling networks affecting growth, development, and stress response.

miR-597-5p inhibits cell growth and promotes cell apoptosis by targeting ELK1 in pancreatic cancer

Pancreatic cancer is a malignant disease with poor prognosis. Emerging evidences have showed that miR-597-5p is closely related to tumor development. However, the functional roles of miR-597-5p in pancreatic cancer remain unknown. This study aimed to investigate the expression of miR-597-5p in pancreatic cancer tissues and cells, and explored its regulatory mechanism during pancreatic cancer progression. Pancreatic cancer and adjacent tissues were obtained to detect the expression of miR-597-5p by RT-qPCR. Cell growth, apoptosis, and related protein expression were, respectively, tested by CCK-8 assay, cell formation, wound healing, Transwell assay, flow cytometry, and western blotting. Finally, the pancreatic cancer mice model was constructed. In vitro and in vivo results showed that miR-597-5p expression was down-regulated in pancreatic cancer tissues and cell lines, and increased the overall survival of pancreatic cancer patients. Moreover, miR-597-5p decreased pancreatic cancer cell viability, reduced relative wound width, suppressed colony formation and decreased invasive cell number, as well as reduced the expression of proliferating cell nuclear antigen (PCNA), Ki67, Cyclin D1, N-cad, and Bcl-2. Meanwhile, it increased pancreatic cancer cell apoptosis and the expression of E-cad, cleaved caspase 3, and Bax. The dual-luciferase reporter assay confirmed miR-597-5p could directly target e-twenty six like-1 (ELK1) oncogene. The reduction of cell growth and the induction of cell apoptosis induced by miR-597-5p were reversed by ELK1. In addition, miR-597-5p inhibited the growth of pancreatic cancer in vivo. This study demonstrated that miR-597-5p may be a novel suppressor of pancreatic cancer. It inhibits pancreatic cancer cell growth and promotes apoptosis by the down-regulation of ELK1 in vitro and in vivo.

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.

EPHB6 controls catecholamine biosynthesis by up-regulating tyrosine hydroxylase transcription in adrenal gland chromaffin cells

EPHB6 is a member of the erythropoietin-producing hepatocellular kinase (EPH) family and a receptor tyrosine kinase with a dead kinase domain. It is involved in blood pressure regulation and adrenal gland catecholamine (CAT) secretion, but several facets of EPHB6-mediated CAT regulation are unclear. In this study, using biochemical, quantitative RT-PCR, immunoblotting, and gene microarray assays, we found that EPHB6 up-regulates CAT biosynthesis in adrenal gland chromaffin cells (AGCCs). We observed that epinephrine content is reduced in the AGCCs from male Ephb6-KO mice, caused by decreased expression of tyrosine hydroxylase, the rate-limiting enzyme in CAT biosynthesis. We demonstrate that the signaling pathway from EPHB6 to tyrosine hydroxylase expression in AGCCs involves Rac family small GTPase 1 (RAC1), MAP kinase kinase 7 (MKK7), c-Jun N-terminal kinase (JNK), proto-oncogene c-Jun, activator protein 1 (AP1), and early growth response 1 (EGR1). On the other hand, signaling via extracellular signal-regulated kinase (ERK1/2), p38 mitogen-activated protein kinase, and ELK1, ETS transcription factor (ELK1) was not affected by EPHB6 deletion. We further report that EPHB6's effect on AGCCs was via reverse signaling through ephrin B1 and that EPHB6 acted in concert with the nongenomic effect of testosterone to control CAT biosynthesis. Our findings elucidate the mechanisms by which EPHB6 modulates CAT biosynthesis and identify potential therapeutic targets for diseases, such as hypertension, caused by dysfunctional CAT biosynthesis.

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.

Expression of Phospho-ELK1 and Its Prognostic Significance in Urothelial Carcinoma of the Upper Urinary Tract

Using preclinical models, we have recently found that ELK1, a transcriptional factor that activates downstream targets, including c-fos proto-oncogene, induces bladder cancer outgrowth. Here, we immunohistochemically determined the expression status of phospho-ELK1, an activated form of ELK1, in upper urinary tract urothelial carcinoma (UUTUC). Overall, phospho-ELK1 was positive in 47 (47.5%; 37 weak (1+) and 10 moderate (2+)) of 99 UUTUCs, which was significantly (P = 0.002) higher than in benign urothelium (21 (25.3%) of 83; 17 1+ and 4 2+) and was also associated with androgen receptor expression (P = 0.001). Thirteen (35.1%) of 37 non-muscle-invasive versus 34 (54.8%) of 62 muscle-invasive UUTUCs (P = 0.065) were immunoreactive for phospho-ELK1. Lymphovascular invasion was significantly (P = 0.014) more often seen in phospho-ELK1(2+) tumors (80.0%) than in phospho-ELK1(0/1+) tumors (36.0%). There were no statistically significant associations between phospho-ELK1 expression and tumor grade, presence of concurrent carcinoma in situ or hydronephrosis, or pN status. Kaplan-Meier and log-rank tests revealed that patients with phospho-ELK1(2+) tumor had marginally and significantly higher risks of disease progression (P = 0.055) and cancer-specific mortality (P = 0.008), respectively, compared to those with phospho-ELK1(0/1+) tumor. The current results thus support our previous observations in bladder cancer and further suggest that phospho-ELK1 overexpression serves as a predictor of poor prognosis in patients with UUTUC.

Resveratrol stimulates c-Fos gene transcription via activation of ERK1/2 involving multiple genetic elements

The polyphenol resveratrol is found in many plant and fruits and is a constituent of our diet. Resveratrol has been proposed to have chemopreventive and anti-inflammatory activities. On the cellular level, resveratrol activates stimulus-regulated transcription factors. To identify resveratrol-responsive elements within a natural gene promoter, the molecular pathway leading to c-Fos gene expression by resveratrol was dissected. The c-Fos gene encodes a basic region leucine zipper transcription factor and is a prototype of an immediate-early gene that is regulated by a wide range of signaling molecules. We analyzed chromatin-integrated c-Fos promoter-luciferase reporter genes where transcription factor binding sites were destroyed by point mutations or deletion mutagenesis. The results show that mutation of the binding sites for serum response factor (SRF), activator protein-1 (AP-1) and cAMP response element binding protein (CREB) significantly reduced reporter gene transcription following stimulation of the cells with resveratrol. Inactivation of the binding sites for signal transducer and activator of transcription (STAT) or ternary complex factors did not influence resveratrol-regulated c-Fos promoter activity. Thus, the c-Fos promoter contains three resveratrol-responsive elements, the cAMP response element (CRE), and the binding sites for SRF and AP-1. Moreover, we show that the transcriptional activation potential of the c-Fos protein is increased in resveratrol-stimulated cells, indicating that the biological activity of c-Fos is elevated by resveratrol stimulation. Pharmacological and genetic experiments revealed that the protein kinase ERK1/2 is the signal transducer that connects resveratrol treatment with the c-Fos gene.

Role of hippocampal activity-induced transcription in memory consolidation

Experience-dependent changes in the strength of connections between neurons in the hippocampus (HPC) are critical for normal learning and memory consolidation, and disruption of this process drives a variety of neurological and psychiatric diseases. Proper HPC function relies upon discrete changes in gene expression driven by transcription factors (TFs) induced by neuronal activity. Here, we describe the induction and function of many of the most well-studied HPC TFs, including cyclic-AMP response element binding protein, serum-response factor, AP-1, and others, and describe their role in the learning process. We also discuss the known target genes of many of these TFs and the purported mechanisms by which they regulate long-term changes in HPC synaptic strength. Moreover, we propose that future research in this field will depend upon unbiased identification of additional gene targets for these activity-dependent TFs and subsequent meta-analyses that identify common genes or pathways regulated by multiple TFs in the HPC during learning or disease.

Emerging themes in neuronal activity-dependent gene expression

In this review, we attempt to discuss emerging themes in the regulation of neuronal activity-regulated genes, focusing primarily on an important subset of immediate-early genes. We first discuss earlier studies that have illuminated the role of cis-acting elements within the promoters of immediate-early genes, the corresponding transcription factors that bind these elements, and the roles of major activity-regulated signaling pathways. However, our emphasis is on new studies that have revealed an important role for epigenetic and topological mechanisms, including enhancer-promoter interactions, enhancer RNAs (eRNAs), and activity-induced DNA breaks, that have emerged as important factors that govern the temporal dynamics of activity-induced gene transcription.

The Insula and Taste Learning

The sense of taste is a key component of the sensory machinery, enabling the evaluation of both the safety as well as forming associations regarding the nutritional value of ingestible substances. Indicative of the salience of the modality, taste conditioning can be achieved in rodents upon a single pairing of a tastant with a chemical stimulus inducing malaise. This robust associative learning paradigm has been heavily linked with activity within the insular cortex (IC), among other regions, such as the amygdala and medial prefrontal cortex. A number of studies have demonstrated taste memory formation to be dependent on protein synthesis at the IC and to correlate with the induction of signaling cascades involved in synaptic plasticity. Taste learning has been shown to require the differential involvement of dopaminergic GABAergic, glutamatergic, muscarinic neurotransmission across an extended taste learning circuit. The subsequent activation of downstream protein kinases (ERK, CaMKII), transcription factors (CREB, Elk-1) and immediate early genes (c-fos, Arc), has been implicated in the regulation of the different phases of taste learning. This review discusses the relevant neurotransmission, molecular signaling pathways and genetic markers involved in novel and aversive taste learning, with a particular focus on the IC. Imaging and other studies in humans have implicated the IC in the pathophysiology of a number of cognitive disorders. We conclude that the IC participates in circuit-wide computations that modulate the interception and encoding of sensory information, as well as the formation of subjective internal representations that control the expression of motivated behaviors.

Tumor-suppressive miRNA-135a inhibits breast cancer cell proliferation by targeting ELK1 and ELK3 oncogenes

Breast cancer is the most common malignant disease amongst women. miRNAs are small, non-coding RNAs that regulate gene expression, thus have the potential to play an important role during cancer development. Emerging evidence shows that miR-135a is down-regulated in breast cancer cells, but the functional roles of miR-135a in breast cancer cells remains unexplored. For this purpose, we investigated the expression of miR-135a in breast cancer cells and explored its functional role during breast cancer progression. In vitro study showed that miR-135a may be a novel tumor suppressor. Further studies showed that transcription factors ELK1 and ELK3 are direct target genes of miR-135a that modulates the suppressive function of miR-135a in breast cancer cells. Induced expression of miR-135a significantly downregulated the expression of ELK1 and ELK3 both at mRNA and protein levels. Furthermore, the effect of miR-135a in MCF-7 and T47D cells was investigated by the overexpression of miR-135a mimics. In vitro, induced expression of miR-135a in breast cancer cells inhibited cell Proliferation and clongenicity. Moreover, a luciferase activity assay revealed that miR-135a could directly target the 3'-untranslated region (3' UTRS) of ELK1 and ELK3 oncogenes. In addition, rescue experiment demonstrated that the promoted cell growth by transcription factors ELK1 and ELK3 was attenuated by the over-expression of miR-135a. Our study demonstrates that miR-135a regulates cell proliferation in breast cancer by targeting ELK1 and ELK3 oncogenes, and suggests that miR-135a potentially can act as a tumor suppressor.

The protumorigenic potential of FTY720 by promoting extramedullary hematopoiesis and MDSC accumulation

FTY720 (also called fingolimod) is recognized as an immunosuppressant and has been approved by the Food and Drug Administration to treat refractory multiple sclerosis. However, long-term administration of FTY720 potentially increases the risk for cancer in recipients. The underlying mechanisms remain poorly understood. Herein, we provided evidence that FTY720 administration potentiated tumor growth. Mechanistically, FTY720 enhanced extramedullary hematopoiesis and massive accumulation of myeloid-derived suppressor cells (MDSCs), which actively suppressed antitumor immune responses. Granulocyte-macrophage colony-stimulating factor (GM-CSF), mainly produced by MDSCs, was identified as a key factor to mediate these effects of FTY720 in tumor microenvironment. Furthermore, we showed that FTY720 triggers MDSCs to release GM-CSF via S1P receptor 3 (S1pr3) through Rho kinase and extracellular signal-regulated kinase-dependent pathway. Thus, our findings provide mechanistic explanation for the protumorigenic potentials of FTY720 and suggest that targeting S1pr3 simultaneously may be beneficial for the patients receiving FTY720 treatment.

Pancancer modelling predicts the context-specific impact of somatic mutations on transcriptional programs

Pancancer studies have identified many genes that are frequently somatically altered across multiple tumour types, suggesting that pathway-targeted therapies can be deployed across diverse cancers. However, the same ‘actionable mutation' impacts distinct context-specific gene regulatory programs and signalling networks—and interacts with different genetic backgrounds of co-occurring alterations—in different cancers. Here we apply a computational strategy for integrating parallel (phospho)proteomic and mRNA sequencing data across 12 TCGA tumour data sets to interpret the context-specific impact of somatic alterations in terms of functional signatures such as (phospho)protein and transcription factor (TF) activities. Our analysis predicts distinct dysregulated transcriptional regulators downstream of somatic alterations in different cancers, and we validate the context-specific differential activity of TFs associated to mutant PIK3CA in isogenic cancer cell line models. These results have implications for the pancancer use of targeted drugs and potentially for the design of combination therapies.

Cancer genomic data sets contain a wealth of data that can be used to predict prognosis and further understand disease. Here, the authors integrate multiple genomics data types to identify transcriptional dysregulation in response to somatic mutations.

STAT3 and ERK pathways are involved in cell growth stimulation of the ST2/IL1RL1 promoter

The ST2 gene was originally identified as a primary responsive gene induced by stimulation with growth factors and by oncogenic stress. The ST2 gene harbors two distinct promoters - a distal promoter and a proximal promoter. In this study, we identified a novel type of serum-responsive element in the ST2 proximal promoter using reporter gene analysis; this element includes a possible responsive element for STAT family proteins. Indeed, enforced expression of constitutively active STAT3 activated this promoter element and induced the expression of ST2 gene products. Furthermore, an oncogenic Ras (G12V) mutant also caused the expression of ST2 gene products by utilizing the proximal promoter. We also clarified that activation of the ST2 promoter by either growth stimulation or oncogenic Ras was suppressed by the inhibitors for STAT3 and ERK pathways. Our observations strongly suggest the importance of STAT family and ERK pathways for the induction of ST2 gene products by cell growth stimulation.

ELK1 is up-regulated by androgen in bladder cancer cells and promotes tumor progression

Little is known about biological significance of ELK1, a transcriptional factor that activates downstream targets including c-fos proto-oncogene, in bladder cancer. Recent preclinical evidence also suggests the involvement of androgen receptor (AR) signaling in bladder cancer progression. In this study, we aim to investigate the functions of ELK1 in bladder cancer growth and their regulation by AR signals. Immunohistochemistry in bladder tumor specimens showed that the levels of phospho-ELK1 (p-ELK1) expression were significantly elevated in urothelial neoplasms, compared with non-neoplastic urothelium tissues, and were also correlated with AR positivity. Patients with p-ELK1-positive non-muscle-invasive and muscle-invasive tumors had significantly higher risks for tumor recurrence and progression, respectively. In AR-positive bladder cancer cell lines, dihydrotestosterone treatment increased ELK1 expression (mRNA, protein) and its nuclear translocation, ELK1 transcriptional activity, and c-fos expression, which was restored by an anti-androgen hydroxyflutamide. ELK1 silencing via short hairpin RNA (shRNA) resulted in decreases in cell viability/colony formation, and cell migration/invasion as well as an increase in apoptosis. Importantly, ELK1 appears to require activated AR to regulate bladder cancer cell proliferation, but not cell migration. Androgen also failed to significantly induce AR transactivation in ELK1-knockdown cells. In accordance with our in vitro findings, ELK1-shRNA expression considerably retarded tumor formation as well as its growth in xenograft-bearing male mice. Our results suggest that ELK1 plays an important role in bladder tumorigenesis and cancer progression, which is further induced by AR activation. Accordingly, ELK1 inhibition, together with AR inactivation, has the potential of being a therapeutic approach for bladder cancer.

Silodosin inhibits prostate cancer cell growth via ELK1 inactivation and enhances the cytotoxic activity of gemcitabine

BACKGROUND

Biological significance of ELK1, a transcriptional factor whose phosphorylation is necessary for c-fos proto-oncogene activation, in prostate cancer remains far from fully understood. In this study, we aim to investigate the role of ELK1 in tumor growth as well as the efficacy of a selective α1A-adrenergic blocker, silodosin, in ELK1 activity in prostate cancer cells.

METHODS

We first immunohistochemically determined the levels of phospho-ELK1 (p-ELK1) expression in radical prostatectomy specimens. We then assessed the effects of ELK1 knockdown via short hairpin RNA and silodosin on cell proliferation, migration, and invasion in prostate cancer lines.

RESULTS

The levels of p-ELK1 expression were significantly higher in carcinoma than in benign (P < 0.001) or high-grade prostatic intraepithelial neoplasia (HGPIN) (P = 0.002) as well as in HGPIN than in benign (P < 0.001). Kaplan-Meier and log-rank tests revealed that moderate-strong positivity of p-ELK1 in carcinomas tended to correlate with biochemical recurrence after radical prostatectomy (P = 0.098). In PC3 and DU145 expressing ELK1 (mRNA/protein) but no androgen receptor (AR), ELK1 silencing resulted in considerable decreases in the expression of c-fos as well as in cell migration/invasion and matrix metalloproteinase-2 expression, but not in cell viability. Silodosin treatment reduced the expression/activity of ELK1 in these cells as well as the viability of AR-positive LNCaP and C4-2 cells and the migration of both AR-positive and AR-negative cells, but not the viability of AR-negative or ELK1-negative cells. Interestingly, silodosin significantly increased sensitivity to gemcitabine, but not to cisplatin or docetaxel, even in AR-negative cells.

CONCLUSIONS

ELK1 is likely to be activated in prostate cancer cells and promote tumor progression. Furthermore, silodosin that inactivates ELK1 in prostate cancer cells not only inhibits their growth but also enhances the cytotoxic activity of gemcitabine. Thus, ELK1 inhibition has the potential of being a therapeutic approach for prostate cancer.

An Elk transcription factor is required for Runx-dependent survival signaling in the sea urchin embryo

Elk proteins are Ets family transcription factors that regulate cell proliferation, survival, and differentiation in response to ERK (extracellular-signal regulated kinase)-mediated phosphorylation. Here we report the embryonic expression and function of Sp-Elk, the single Elk gene of the sea urchin Strongylocentrotus purpuratus. Sp-Elk is zygotically expressed throughout the embryo beginning at late cleavage stage, with peak expression occurring at blastula stage. Morpholino antisense-mediated knockdown of Sp-Elk causes blastula-stage developmental arrest and embryo disintegration due to apoptosis, a phenotype that is rescued by wild-type Elk mRNA. Development is also rescued by Elk mRNA encoding a serine to aspartic acid substitution (S402D) that mimics ERK-mediated phosphorylation of a conserved site that enhances DNA binding, but not by Elk mRNA encoding an alanine substitution at the same site (S402A). This demonstrates both that the apoptotic phenotype of the morphants is specifically caused by Elk depletion, and that phosphorylation of serine 402 of Sp-Elk is critical for its anti-apoptotic function. Knockdown of Sp-Elk results in under-expression of several regulatory genes involved in cell fate specification, cell cycle control, and survival signaling, including the transcriptional regulator Sp-Runt-1 and its target Sp-PKC1, both of which were shown previously to be required for cell survival during embryogenesis. Both Sp-Runt-1 and Sp-PKC1 have sequences upstream of their transcription start sites that specifically bind Sp-Elk. These results indicate that Sp-Elk is the signal-dependent activator of a feed-forward gene regulatory circuit, consisting also of Sp-Runt-1 and Sp-PKC1, which actively suppresses apoptosis in the early embryo.

Multifaceted enrichment analysis of RNA-RNA crosstalk reveals cooperating micro-societies in human colorectal cancer

Alterations in the balance of mRNA and microRNA (miRNA) expression profiles contribute to the onset and development of colorectal cancer. The regulatory functions of individual miRNA-gene pairs are widely acknowledged, but group effects are largely unexplored. We performed an integrative analysis of mRNA–miRNA and miRNA–miRNA interactions using high-throughput mRNA and miRNA expression profiles obtained from matched specimens of human colorectal cancer tissue and adjacent non-tumorous mucosa. This investigation resulted in a hypernetwork-based model, whose functional backbone was fulfilled by tight micro-societies of miRNAs. These proved to modulate several genes that are known to control a set of significantly enriched cancer-enhancer and cancer-protection biological processes, and that an array of upstream regulatory analyses demonstrated to be dependent on miR-145, a cell cycle and MAPK signaling cascade master regulator. In conclusion, we reveal miRNA-gene clusters and gene families with close functional relationships and highlight the role of miR-145 as potent upstream regulator of a complex RNA–RNA crosstalk, which mechanistically modulates several signaling pathways and regulatory circuits that when deranged are relevant to the changes occurring in colorectal carcinogenesis.

Stepwise evolution of Elk-1 in early deuterostomes

Metazoans have multiple ETS paralogues with overlapping or indiscriminate biological functions. Elk-1, one of three mammalian ternary complex factors (TCFs), is a well-conserved, ETS domain-containing transcriptional regulator of mitogen-responsive genes that operates in concert with serum response factor (SRF). Nonetheless, its genetic role remains unresolved because the elk-1 gene could be deleted from the mouse genome seemingly without adverse effect. Here we have explored the evolution of Elk-1 to gain insight into its conserved biological role. We identified antecedent Elk-1 proteins in extant early metazoans and used amino acid sequence alignments to chart the appearance of domains characteristic of human Elk-1. We then performed biochemical studies to determine whether putative domains apparent in the Elk-1 protein of a primitive hemichordate were functionally orthologous to those of human Elk-1. Our findings imply the existence of primordial Elk-1 proteins in primitive deuterostomes that could operate as mitogen-responsive ETS transcription factors but not as TCFs. The role of TCF was acquired later, but presumably prior to the whole genome duplications in the basal vertebrate lineage. Thus its evolutionary origins link Elk-1 to the appearance of mesoderm.

Dual Specificity Phosphatase 5, a Specific Negative Regulator of ERK Signaling, Is Induced by Serum Response Factor and Elk-1 Transcription Factor

Serum stimulation of mammalian cells induces, via the MAPK pathway, the nuclear protein DUSP5 (dual-specificity phosphatase 5), which specifically interacts with and inactivates the ERK1/2 MAP kinases. However, molecular mechanisms underlying DUSP5 induction are not well known. Here, we found that the DUSP5 mRNA induction depends on a transcriptional regulation by the MAPK pathway, without any modification of the mRNA stability. Two contiguous CArG boxes that bind serum response factor (SRF) were found in a 1 Kb promoter region, as well as several E twenty-six transcription factor family binding sites (EBS). These sites potentially bind Elk-1, a transcription factor activated by ERK1/2. Using wild type or mutated DUSP5 promoter reporters, we demonstrated that SRF plays a crucial role in serum induction of DUSP5 promoter activity, the proximal CArG box being important for SRF binding in vitro and in living cells. Moreover, in vitro and in vivo binding data of Elk-1 to the same promoter region further demonstrate a role for Elk-1 in the transcriptional regulation of DUSP5. SRF and Elk-1 form a ternary complex (Elk-1-SRF-DNA) on DUSP5 promoter, consequently providing a link to an important negative feedback tightly regulating phosphorylated ERK levels.

DNA Electric Charge Oscillations Govern Protein-DNA Recognition

The transcriptional activity of the serum response factor (SRF) protein is triggered by its binding to a 10-base-pair DNA consensus sequence designated the CArG box, which is the core sequence of the serum response element (SRE). Sequence-specific recognition of the CArG box by a core domain of 100 amino acid residues of SRF (core-SRF) was asserted to depend almost exclusively on the intrinsic SRE conformation and on the degree of protein-induced SRE bending. Nevertheless, this paradigm was invalidated by a temperature-dependent Raman spectroscopy study of 20-mer oligonucleotides involved in bonding interactions with core-SRF that reproduced both wild type and mutated c-fos SREs. Indeed, the SRE moieties that are complexed with core-SRF exhibit permanent interconversion dynamics between bent and linear conformers. Thus, sequence-specific recognition of the CArG box by core-SRF cannot be explained only in terms of the three-dimensional structure of the SRE. A particular dynamic pairing process discriminates between the wild type and mutated complexes. Specific oscillations of the phosphate charge network of the SRE govern the recognition between both partners rather than an intrinsic set of conformations of the SRE.

Organization of the MADS box from human SRF revealed by tyrosine perturbation

MADS box family transcription factors are involved in signal transduction and development control through DNA specific sequence recognition. The DNA binding domain of these proteins contains a conservative 55-60 amino acid sequence which defines the membership of this large family. Here we present a thorough study of the MADS segment of serum response factor (MADS(SRF)). Fluorescence, UV-absorption, and Raman spectroscopy studies were performed in order to disclose its behavior and basic functional properties in an aqueous environment. The secondary structure of MADS(SRF) estimated by analysis of Raman spectra and supported by CD has revealed only the C-terminal part as homologous with those of free core-SRF, while the N-terminal part has lost the stable α-helical structure found in both the free core-SRF and its specific complex with DNA. The three tyrosine residues of the MADS(SRF) were used as spectroscopic inner probes. The effect of environmental conditions, especially pH variations and addition of variously charged quenchers, on their spectra was examined. Two-component fluorescence quenching was revealed using factor analysis and corresponding Stern-Volmer constants determined. Factor analysis of absorbance and fluorescence pH titration led to determination of three dissociation constants pKa1 = 6.4 ± 0.2, pKa2 = 7.3 ± 0.2, and pKa3 = 9.6 ± 0.6. Critical comparison of all experiments identified the deprotonation of His193 hydrogen bonded to Tyr195 as a candidate for pKa1 (and that of Tyr158 as a candidate for pKa2). Within MADS(SRF), His193 is a key intermediary between the N-terminal primary DNA binding element and the hydrophobic C-terminal protein dimerization element.

Neurotensin, a Novel Messenger to Cross-Link Inflammation and Tumor Invasion via Epithelial-Mesenchymal Transition Pathway

Multiple cytokines and growth factors are critical for the prognosis of cancer which has been regarded as a worldwide health problem. Recently, neuropeptides, soluble factors regulating a series of functions in the central nervous system, have also been demonstrated to stimulate the proliferation and migration of tumor cells. Among these signaling peptides, the role of neurotensin (NTS) on malignancy procession has become a hot topic. The effects of NTS on tumor growth and its antiapoptosis role have already been identified. Subsequently, studies demonstrated the impact of NTS on the migration and invasion, but the molecular mechanisms involved are still unclear at present. Recently, some reports indicated that NTS could induce expression and secretion of interleukin-8 (IL-8) to promote local imflammatory response which might participate in epithelial-mesenchymal transition (EMT)-related tumor migration. In present review, we highlight the process of tumor EMT induced by NTS through stimulating IL-8 and the significance of NTS/IL-8 pathway in clinical application prospect.

Effects of egg yolk-derived peptide on osteogenic gene expression and MAPK activation

The present study investigated the effects of egg yolk-derived peptide (YPEP) on osteogenic activities and MAPK-regulation of osteogenic gene expressions. The effects of YPEP on cell proliferation, alkaline phosphatase activity, collagen synthesis, and mineralization were measured in human osteoblastic MG-63 cells. Activation of MAPKs and downstream transcription factors such as extracellular-signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase 1/2 (JNK1/2), p38, ELK1, and cJUN were examined using western blot analysis. YPEP dose-dependently increased MG-63 cell proliferation, ALP activity, collagen synthesis, and calcium deposition. YPEP activated ERK1/2, p38, and ELK1 phosphorylation whereas JNK and cJUN were not affected by YPEP. The COL1A1 (collagen, type I, alpha 1), ALPL (alkaline phosphatase), and SPP1 (secreted phosphoprotein 1, osteopontin) gene expressions were increased while BGLAP (osteocalcin) was not affected by YPEP. The ERK1/2 inhibitor (PD98509) blocked the YPEP-induced COL1A1 and ALPL gene expressions as well as ELK1 phosphorylation. The p38 inhibitor (SB203580) blocked YPEP-induced COL1A1 and ALPL gene expressions. SPP1 gene expression was not affected by these MAPK inhibitors. In conclusion, YPEP treatment stimulates the osteogenic differentiation via the MAPK/ELK1 signaling pathway. These results could provide a mechanistic explanation for the bone-strengthening effects of YPEP.

Erlotinib derivative inhibits hepatocellular carcinoma by targeting CIP2A to reactivate protein phosphatase 2A

Protein phosphatase 2A (PP2A) is a tumor suppressor, which is functionally defective in various cancers. Previously, we found that PP2A activity determined the anticancer effect of bortezomib and erlotinib in hepatocellular carcinoma (HCC) cells. Here, we tested a novel erlotinib derivative, TD52, in four HCC cell lines, PLC5, Huh-7, Hep3B and Sk-Hep1. Using MTT and flow cytometry, we showed that TD52 had more potent apoptotic effects than erlotinib in HCC cells. TD52-induced apoptosis was associated with dose- and time- dependent reactivation of PP2A and downregulation of cancerous inhibitor of protein phosphatase 2A (CIP2A) and p-Akt. Inhibition of PP2A or ectopic expression of CIP2A or Akt in PLC5 cells abolished the effects of TD52. Furthermore, we demonstrated that TD52 affected the binding of Elk-1 to the proximal promoter of the CIP2A gene, thus downregulating transcription of CIP2A. Importantly, TD52-induced tumor inhibition was associated with reactivation of PP2A and downregulation of CIP2A and p-Akt in vivo. In conclusion, we found that enhancement of PP2A activity by inhibition of CIP2A determines the apoptotic effect induced by TD52. Our findings disclose the therapeutic mechanism of this novel targeted agent, and suggest the therapeutic potential and feasibility of developing PP2A enhancers as a novel anticancer strategy.

Epidermal growth factor receptor signalling in human breast cancer cells operates parallel to estrogen receptor α signalling and results in tamoxifen insensitive proliferation

Background

Tamoxifen resistance is a major problem in the treatment of estrogen receptor (ER) α -positive breast cancer patients. Although the mechanisms behind tamoxifen resistance are still not completely understood, clinical data suggests that increased expression of receptor tyrosine kinases is involved. Here, we studied the estrogen and anti-estrogen sensitivity of human breast cancer MCF7 cells that have a moderate, retroviral-mediated, ectopic expression of epidermal growth factor receptor (MCF7-EGFR).

Methods

Proliferation of MCF7-EGFR and parental cells was induced by 17β-estradiol (E2), epidermal growth factor (EGF) or a combination of these. Inhibition of proliferation under these conditions was investigated with 4-hydroxy-tamoxifen (TAM) or fulvestrant at 10^-12 to 10^-6 M. Cells were lysed at different time points to determine the phosphorylation status of EGFR, MAPK_1/3, AKT and the expression of ERα. Knockdown of target genes was established using smartpool siRNAs. Transcriptomics analysis was done 6 hr after stimulation with growth factors using Affymetrix HG-U133 PM array plates.

Results

While proliferation of parental MCF7 cells could only be induced by E2, proliferation of MCF7-EGFR cells could be induced by either E2 or EGF. Treatment with TAM or fulvestrant did significantly inhibit proliferation of MCF7-EGFR cells stimulated with E2 alone. EGF treatment of E2/TAM treated cells led to a marked cell proliferation thereby overruling the anti-estrogen-mediated inhibition of cell proliferation. Under these conditions, TAM however did still inhibit ERα- mediated transcription. While siRNA-mediated knock-down of EGFR inhibited the EGF- driven proliferation under TAM/E2/EGF condition, knock down of ERα did not. The TAM resistant cell proliferation mediated by the conditional EGFR-signaling may be dependent on the PI3K/Akt pathway but not the MEK/MAPK pathway, since a MEK inhibitor (U0126), did not block the proliferation. Transcriptomic analysis under the various E2/TAM/EGF conditions revealed that E2 and EGF dependent transcription have little overlap and rather operate in a parallel fashion.

Conclusions

Our data indicate that enhanced EGFR-driven signalling is sufficient to overrule the TAM- mediated inhibition of E2-driven cell proliferation. This may have profound implications for the anti-estrogen treatment of ER-positive breast cancers that have increased levels of EGFR.

Site-specific association with host and viral chromatin by Kaposi's sarcoma-associated herpesvirus LANA and its reversal during lytic reactivation

Latency-associated nuclear antigen (LANA), a multifunctional protein expressed by the Kaposi sarcoma-associated herpesvirus (KSHV) in latently infected cells, is required for stable maintenance of the viral episome. This is mediated by two interactions: LANA binds to specific sequences (LBS1 and LBS2) on viral DNA and also engages host histones, tethering the viral genome to host chromosomes in mitosis. LANA has also been suggested to affect host gene expression, but both the mechanism(s) and role of this dysregulation in KSHV biology remain unclear. Here, we have examined LANA interactions with host chromatin on a genome-wide scale using chromatin immunoprecipitation with high-throughput sequencing (ChIP-seq) and show that LANA predominantly targets human genes near their transcriptional start sites (TSSs). These host LANA-binding sites are generally found within transcriptionally active promoters and display striking overrepresentation of a consensus DNA sequence virtually identical to the LANA-binding site 1 (LBS1) motif in KSHV DNA. Comparison of the ChIP-seq profile with whole-transcriptome (high-throughput sequencing of RNA transcripts [RNA-seq]) data reveals that few of the genes that are differentially regulated in latent infection are occupied by LANA at their promoters. This suggests that direct LANA binding to promoters is not the prime determinant of altered host transcription in KSHV-infected cells. Most surprisingly, the association of LANA to both host and viral DNA is strongly disrupted during the lytic cycle of KSHV. This disruption can be prevented by the inhibition of viral DNA synthesis, suggesting the existence of novel and potent regulatory mechanisms linked to either viral DNA replication or late gene expression.

IMPORTANCE

Here, we employ complementary genome-wide analyses to evaluate the distribution of the highly abundant latency-associated nuclear antigen, LANA, on the host genome and its impact on host gene expression during KSHV latent infection. Combined, ChIP-seq and RNA-seq reveal that LANA accumulates at active gene promoters that harbor specific short DNA sequences that are highly reminiscent of its cognate binding sites in the virus genome. Unexpectedly, we found that such association does not lead to remodeling of global host transcription during latency. We also report for the first time that LANA's ability to bind host and viral chromatin is highly dynamic and is disrupted in cells undergoing an extensive lytic reactivation. This therefore suggests that the association of LANA to chromatin during a productive infection cycle is controlled by a new regulatory mechanism.

Oncogenic Ras pushes (and pulls) cell cycle progression through ERK activation

The Ras-Raf-MEK-ERK signaling cascade is capable of channeling a wide variety of extracellular signals into control of cell proliferation, differentiation, senescence, and death. Because aberrant regulation at all steps of this signaling axis is observed in cancer, it remains an area of great interest in the field of tumor biology. Here we present evidence of the intricate and delicate levels of control of this pathway as it pertains to cell cycle regulation and illustrate how this control is not simply a rheostat.

Molecular mechanisms of gonadotropin-releasing hormone signaling: integrating cyclic nucleotides into the network

Gonadotropin-releasing hormone (GnRH) is the primary regulator of mammalian reproductive function in both males and females. It acts via G-protein coupled receptors on gonadotropes to stimulate synthesis and secretion of the gonadotropin hormones luteinizing hormone and follicle-stimulating hormone. These receptors couple primarily via G-proteins of the Gq/ll family, driving activation of phospholipases C and mediating GnRH effects on gonadotropin synthesis and secretion. There is also good evidence that GnRH causes activation of other heterotrimeric G-proteins (Gs and Gi) with consequent effects on cyclic AMP production, as well as for effects on the soluble and particulate guanylyl cyclases that generate cGMP. Here we provide an overview of these pathways. We emphasize mechanisms underpinning pulsatile hormone signaling and the possible interplay of GnRH and autocrine or paracrine regulatory mechanisms in control of cyclic nucleotide signaling.

Involvement of MAPK signaling pathway in the osteogenic gene expressions of Cervi Pantotrichum Cornu in MG-63 human osteoblast-like cells

AIMS

The purposes of this study were to determine whether Cervi Pantotrichum Cornu (CPC) has osteogenic activities in human osteoblastic MG-63 cells and to investigate the underlying molecular mechanism.

MAIN METHODS

The effects of CPC on alkaline phosphatase activity, collagen synthesis, and calcium deposits were measured. The COL1A1, ALPL, BGLAP, and SPP1 expressions were measured by real-time PCR. Phosphorylated MAP kinases (ERK1/2, JNK1/2, p38, ELK1, and cJUN) were studied by western blot analysis. The involvement of MAPK pathway in osteogenic gene expressions was determined by using each selective MAPK inhibitor (PD98059, SP600125, and SB203580).

KEY FINDINGS

CPC increased alkaline phosphatase activity, collagen synthesis, and calcium deposits. CPC activated ERK1/2, JNK1/2, p38, and ELK1 phosphorylation except cJUN. CPC increased the COL1A1, ALPL, BGLAP, and SPP1 gene expressions. The elevated COL1A1 and BGLAP expressions were inhibited by PD98059, SP600125 or SB203580. The elevated ALPL expression was blocked by SB203580. The elevated SPP1 expression was inhibited by SP600125 or SB203580. CPC increased COL1A1 and BGLAP expressions via ERK1/2, JNK1/2, and p38 MAPKs pathways and SPP1 expression via JNK1/2 and p38 pathways. p38 pathway is needed for ALPL expression.

SIGNIFICANCE

These results imply that MAPK signaling pathway is an indispensable factor for bone matrix genes expression of CPC in MG-63 human osteoblast-like cells.

The F-box protein FBXO25 promotes the proteasome-dependent degradation of ELK-1 protein

FBXO25 is one of the 69 known human F-box proteins that serve as specificity factors for a family of ubiquitin ligases composed of SKP1, Rbx1, Cullin1, and F-box protein (SCF1) that are involved in targeting proteins for degradation across the ubiquitin proteasome system. However, the substrates of most SCF E3 ligases remain unknown. Here, we applied an in chip ubiquitination screen using a human protein microarray to uncover putative substrates for the FBXO25 protein. Among several novel putative targets identified, the c-fos protooncogene regulator ELK-1 was characterized as the first endogenous substrate for SCF1(FBXO25) E3 ligase. FBXO25 interacted with and mediated the ubiquitination and proteasomal degradation of ELK-1 in HEK293T cells. In addition, FBXO25 overexpression suppressed induction of two ELK-1 target genes, c-fos and egr-1, in response to phorbol 12-myristate 13-acetate. Together, our findings show that FBXO25 mediates ELK-1 degradation through the ubiquitin proteasome system and thereby plays a role in regulating the activation of ELK-1 pathway in response to mitogens.

Net expression inhibits the growth of pancreatic ductal adenocarcinoma cell PL45 in vitro and in vivo

Pancreatic ductal adenocarcinoma has a poor prognosis due to late diagnosis and a lack of effective therapeutic options. Thus, it is important to better understand its molecular mechanisms and to develop more effective treatments for the disease. The ternary complex factor Net, which exerts its strong inhibitory function on transcription of proto-oncogene gene c-fos by forming ternary complexes with a second transcription factor, has been suspected of being involved in pancreatic cancer and other tumors biology. In this study, we found that the majority of pancreatic ductal adenocarcinoma tissues and cell lines had weak or no expression of Net, whereas significantly high level of Net expression occurred in paired adjacent normal tissues we studied. Furthermore, using in vitro and in vivo model systems, we found that overexpression of Net inhibited cell growth and survival and induced cell apoptosis in human pancreatic ductal adenocarcinoma cell PL45; the mechanisms by which Net inhibited the cell cycle progression were mainly through P21-Cyclin D1/CDK4 Pathway. Our data thus suggested that Net might play an important role in pancreatic carcinogenesis, possibly by acting as a tumor suppressor gene.

Efficacy of three drugs for protecting against gentamicin-induced hair cell and hearing losses

BACKGROUND AND PURPOSE Exposure to an ototoxic level of an aminoglycoside can result in hearing loss. In this we study investigated the otoprotective efficacy of dexamethasone (DXM), melatonin (MLT) and tacrolimus (TCR) in gentamicin (GM)-treated animals and cultures. EXPERIMENTAL APPROACH Wistar rats were divided into controls (treated with saline); exposed to GM only (GM); and three GM-exposed groups treated with either DXM, MLT or TCR. Auditory function and cochlear surface preparations were studied. In vitro studies of oxidative stress, pro-inflammatory cytokine mRNA levels, the MAPK pathway and caspase-3 activation were performed in organ of Corti explants from 3-day-old rats. KEY RESULTS DXM, MLT and TCR decreased levels of reactive oxygen species in GM-exposed explants. The mRNA levels of TNF-α, IL-1β and TNF-receptor type 1 were significantly reduced in GM + DXM and GM + MLT groups. Phospho-p38 MAPK levels decreased in GM + MLT and GM + TCR groups, while JNK phosphorylation was reduced in GM + DXM and GM + MLT groups. Caspase-3 activation decreased in GM + DXM, GM + MLT and GM + TCR groups. These results were consistent with in vivo results. Local treatment of GM-exposed rat cochleae with either DXM, MLT or TCR preserved auditory function and prevented auditory hair cell loss. CONCLUSIONS AND IMPLICATIONS In organ of Corti explants, GM increased oxidative stress and initiated an inflammatory response that led to the activation of MAPKs and apoptosis of hair cells. The three compounds tested demonstrated otoprotective properties that could be beneficial in the treatment of ototoxicity-induced hearing loss.

Elk-1 phosphorylated at threonine-417 is present in diverse cancers and correlates with differentiation grade of colonic adenocarcinoma

Elk-1 is a member of the Ets family of transcription factors, which are identified by a conserved Ets DNA-binding domain that mediates transcriptional regulation at Ets sequence--containing promoters. The activation domain of Elk-1 is important for executing its physiologic functions and contains many phosphorylation sites targeted by various MAP kinases following exposure to cell stressors or mitogenic stimuli. The different combinations of phosphorylated sites allow specificity of cellular responses mediated through redundant signaling pathways activated by distinct stimuli. Through phosphorylation of S383, mitogen-activated protein kinase (MAPK)-activating stimuli have been shown to regulate various processes important in carcinogenesis through transcriptional regulation in various cell lines, including proliferation. Phosphorylation at the T417 site (pT417), but not the S383 site, is involved in neuronal apoptosis induced through dendritic signaling mechanisms and associates with neuronal lesions in many Lewy body diseases. This points to distinct roles for these different phosphorylation sites in pathophysiologic pathways. However, the S383 site remains the best characterized in the context of normal function and carcinogenesis in cell lines, and less is known about the biochemistry of other phosphorylation sites, particularly in more biochemically relevant models. Here, we show that Elk-1 pT417 is present in epithelial cell nuclei of various normal and cancer tissues and that the number of pT417-positive cells correlates with differentiation grade of colonic adenocarcinomas. This nuclear localization and correlation with tumor differentiation in adenocarcinoma suggests a potentially important transcriptional and biochemical role of this phosphorylation site in carcinogenesis of this tumor type.

Adhesion regulates MAP kinase/ternary complex factor exchange to control a proliferative transcriptional switch

BACKGROUND

The ternary complex factors (TCFs; Elk1, Net, and Sap-1) are growth factor-responsive transcription cofactors of serum response factor (SRF) and are activated by MAP kinase (MAPK) phosphorylation to regulate immediate early gene transcription. Although cell adhesion also can regulate immediate early genes and proliferation, the mechanism for this effect has remained unexplored.

RESULTS

Restricting adhesion and spreading of G(0)-synchronized cells on substrates with decreasing size of micropatterned islands of fibronectin suppressed serum-induced immediate early gene expression and S phase entry. Knockdown of Sap-1 decreased expression of the immediate early genes egr1 and fos and subsequent proliferation normally present with high adhesion, whereas knockdown of Net rescued egr1 and fos expression and proliferation normally suppressed by low adhesion. Chromatin immunoprecipitation studies showed increased occupancy of egr1 and fos promoters by Sap-1 with high adhesion, whereas low adhesion increased Net occupancy. This switch in TCF promoter binding was regulated by an adhesion-mediated switch in MAPK activity. Increasing adhesion enhanced serum-induced JNK activity while suppressing p38 activity, leading to increased Sap-1 phosphorylation and Net dephosphorylation, and switching Net with Sap-1 at egr1 and fos promoters to support proliferation. Microarray studies confirmed this switch in TCF regulation of proliferative genes and uncovered novel gene targets and functions coregulated by Sap-1 and Net.

CONCLUSIONS

These data demonstrate a key role for the TCFs in adhesion-induced transcription and proliferation and reveal a novel MAPK/TCF transcriptional switch that controls this process.

Common genetic variants in the PSCA gene influence gene expression and bladder cancer risk

Genome-wide association studies have identified a SNP, rs2294008, on 8q24.3 within the prostate stem cell antigen (PSCA) gene, as a risk factor for bladder cancer. To fine-map this region, we imputed 642 SNPs within 100 Kb of rs2294008 in addition to 33 markers genotyped in one of the reported genome-wide association study in 8,652 subjects. A multivariable logistic regression model adjusted for rs2294008 revealed a unique signal, rs2978974 (r(2) = 0.02, D' = 0.19 with rs2294008). In the combined analysis of 5,393 cases and 7,324 controls, we detected a per-allele odds ratio (OR) = 1.11 [95% confidence interval (CI) = 1.06-1.17, P = 5.8 × 10(-5)] for rs2294008 and OR = 1.07 (95% CI = 1.02-1.13, P = 9.7 × 10(-3)) for rs2978974. The effect was stronger in carriers of both risk variants (OR = 1.24, 95% CI = 1.08-1.41, P = 1.8 × 10(-3)) and there was a significant multiplicative interaction (P = 0.035) between these two SNPs, which requires replication in future studies. The T risk allele of rs2294008 was associated with increased PSCA mRNA expression in two sets of bladder tumor samples (n = 36, P = 0.0007 and n = 34, P = 0.0054) and in normal bladder samples (n = 35, P = 0.0155), but rs2978974 was not associated with PSCA expression. SNP rs2978974 is located 10 Kb upstream of rs2294008, within an alternative untranslated first exon of PSCA. The non-risk allele G of rs2978974 showed strong interaction with nuclear proteins from five cell lines tested, implying a regulatory function. In conclusion, a joint effect of two PSCA SNPs, rs2294008 and rs2978974, suggests that both variants may be important for bladder cancer susceptibility, possibly through different mechanisms that influence the control of mRNA expression and interaction with regulatory factors.

The role of prostaglandin E2 in endometriosis

Endometriosis is a leading cause of infertility in women of reproductive age. It involves the occurrence of endometrial tissue outside the uterine endometrium, mainly in the peritoneal cavity. Prostaglandin E(2) is up regulated in the peritoneal cavity in endometriosis and is produced by macrophages and ectopic endometrial cells. This prostaglandin is involved in the pathophysiology of the disease and elicits cell signals via four receptor types. Prostaglandin E(2) increases estrogen synthesis by up regulating steroidogenic acute regulatory protein (StAR) and aromatase. It inhibits apoptosis and up regulates fibroblast growth factor-9 (FGF-9) promoting cell proliferation. Prostaglandin E(2) affects leukocyte populations and promotes angiogenesis through its effect on estrogen and up regulation of vascular endothelial growth factor (VEGF). Dienogest is a synthetic progestin targeting expression of genes involved in prostaglandin synthesis.

AP-1 elements and TCL1 protein regulate expression of the gene encoding protein tyrosine phosphatase PTPROt in leukemia

We previously demonstrated that the gene encoding PTPROt, the truncated form of protein tyrosine phosphatase receptor type O expressed predominantly in hematopoietic cells, is a candidate tumor suppressor and is down-regulated in chronic lymphocytic leukemia (CLL). Here, we show that PTPROt expression is significantly reduced in CD19(+) spleen B cells from Eμ-T cell leukemia 1 (TCL1) transgenic mice relative to the wild-type mice. Strikingly, as much as a 60% decrease in PTPROt expression occurs at 7 weeks independently of promoter methylation. To elucidate the potential mechanism for this early suppression of PTPROt in these mice, we explored the role of activating protein-1 (AP-1) in its expression. We first demonstrate that AP-1 activation by 12-O-tetradecanoylphorbol-13-acetate induces PTPROt expression with concurrent recruitment of c-fos and c-jun to its promoter. The PTPROt promoter is also responsive to over- and underexpression of AP-1, confirming the role of AP-1 in PTPROt expression. Next, we demonstrate that TCL1 can repress the PTPROt promoter by altering c-fos expression and c-jun activation state. Finally, using primary CLL cells we have shown an inverse relationship between TCL1 and PTPROt expression. These findings further substantiate the role of TCL1 in PTPROt suppression and its importance in the pathogenesis of CLL.

Genome-wide analysis reveals PADI4 cooperates with Elk-1 to activate c-Fos expression in breast cancer cells

Peptidylarginine deiminase IV (PADI4) catalyzes the conversion of positively charged arginine and methylarginine residues to neutrally charged citrulline, and this activity has been linked to the repression of a limited number of target genes. To broaden our knowledge of the regulatory potential of PADI4, we utilized chromatin immunoprecipitation coupled with promoter tiling array (ChIP-chip) analysis to more comprehensively investigate the range of PADI4 target genes across the genome in MCF-7 breast cancer cells. Results showed that PADI4 is enriched in gene promoter regions near transcription start sites (TSSs); and, surprisingly, this pattern of binding is primarily associated with actively transcribed genes. Computational analysis found potential binding sites for Elk-1, a member of the ETS oncogene family, to be highly enriched around PADI4 binding sites; and coimmunoprecipitation analysis then confirmed that Elk-1 physically associates with PADI4. To better understand how PADI4 may facilitate gene transactivation, we then show that PADI4 interacts with Elk-1 at the c-Fos promoter and that, following Epidermal Growth Factor (EGF) stimulation, PADI4 catalytic activity facilitates Elk-1 phosphorylation, histone H4 acetylation, and c-Fos transcriptional activation. These results define a novel role for PADI4 as a transcription factor co-activator.