C-fos Promoter Activity Research Articles

Increase of c-FOS promoter transcriptional activity by the dual leucine zipper kinase

The dual leucine zipper kinase (DLK) and the ubiquitously expressed transcription factor c-FOS have important roles in beta-cell proliferation and function. Some studies in neuronal cells suggest that DLK can influence c-FOS expression. Given that c-FOS is mainly regulated at the transcriptional level, the effect of DLK on c-FOS promoter activity was investigated in the beta-cell line HIT. The methods used in this study are the following: Luciferase reporter gene assays, immunoblot analysis, CRISPR-Cas9-mediated genome editing, and real-time quantitative PCR. In the beta-cell line HIT, overexpressed DLK increased c-FOS promoter activity twofold. Using 5′-,3′-promoter deletions, the promoter regions from − 348 to − 339 base pairs (bp) and from a − 284 to − 53 bp conferred basal activity, whereas the promoter region from − 711 to − 348 bp and from − 53 to + 48 bp mediated DLK responsiveness. Mutation of the cAMP response element within the promoter prevented the stimulatory effect of DLK. Treatment of HIT cells with KCl and the adenylate cyclase activator forskolin increased c-FOS promoter transcriptional activity ninefold. Since the transcriptional activity of those promoter fragments activated by KCl and forskolin was decreased by DLK, DLK might interfere with KCl/forskolin-induced signaling. In a newly generated, genome-edited HIT cell line lacking catalytically active DLK, c-Fos mRNA levels were reduced by 80% compared to the wild-type cell line. DLK increased c-FOS promoter activity but decreased stimulated transcriptional activity, suggesting that DLK fine-tunes c-FOS promoter-dependent gene transcription. Moreover, at least in HIT cells, DLK is required for FOS mRNA expression.

Time-tagged ticker tapes for intracellular recordings.

Recording transcriptional histories of a cell would enable deeper understanding of cellular developmental trajectories and responses to external perturbations. Here we describe an engineered protein fiber that incorporates diverse fluorescent marks during its growth to store a ticker tape-like history. An embedded HaloTag reporter incorporates user-supplied dyes, leading to colored stripes that map the growth of each individual fiber to wall clock time. A co-expressed eGFP tag driven by a promoter of interest records a history of transcriptional activation. High-resolution multi-spectral imaging on fixed samples reads the cellular histories, and interpolation of eGFP marks relative to HaloTag timestamps provides accurate absolute timing. We demonstrate recordings of doxycycline-induced transcription in HEK cells and cFos promoter activation in cultured neurons, with a single-cell absolute accuracy of 30-40 minutes over a 12-hour recording. The protein-based ticker tape design we present here could be generalized to achieve massively parallel single-cell recordings of diverse physiological modalities.

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.

Interleukin-34-CSF1R Signaling Axis Promotes Epithelial Cell Transformation and Breast Tumorigenesis.

IL-34 has been recently identified as a ligand for CSF1R that regulates various cellular processes including cell proliferation, survival, and differentiation. Although the binding of IL-34 to CSF1R modulates several cancer-driving signaling pathways, little is known about the role of IL-34/CSF1R signaling in breast cancer. Herein, we report that IL-34 induces epithelial cell transformation and breast tumorigenesis through activation of MEK/ERK and JNK/c-Jun pathways. IL-34 increased the phosphorylation of MEK1/2, ERK1/2, JNK1/2, and c-Jun through CSF1R in mouse skin epidermal JB6 C141 cells and human breast cancer MCF7 cells. IL-34 enhanced c-Fos and c-Jun promoter activity, resulting in increased AP-1 transactivation activity in JB6 Cl41 and MCF7 cells. Moreover, PIN1 enhanced IL-34-induced phosphorylation of MEK1/2, ERK1/2, JNK1/2, and c-Jun in JB6 Cl41 and MCF7 cells. Inhibition of PIN1 using juglone prevented the IL-34-induced transformation of JB6 C141 cells. Similarly, silencing of PIN1 reduced the IL-34-induced tumorigenicity of MCF7 cells. Consistent with these results, the synergistic model showed that treatment with juglone suppressed the IL-34-induced growth of tumors formed by 4T1 cells in BALB/c mice. Our study demonstrates the role of IL-34-induced MEK/ERK and JNK/c-Jun cascades in breast cancer and highlights the regulatory role of PIN1 in IL-34-induced breast tumorigenesis.

The super-cooling compound icilin stimulates c-Fos and Egr-1 expression and activity involving TRPM8 channel activation, Ca2+ ion influx and activation of the ternary complex factor Elk-1

The TRPM8 cation channel can be activated by the cooling compound icilin. Recently, we showed that stimulation of TRPM8 channels induces a signaling cascade leading to the activation of the transcription factor AP-1. Additionally, expression of the AP-1 constituent c-Fos has been shown to be induced following TRPM8 stimulation. c-Fos is frequently used as a marker for neuronal activity. Here, we have analyzed the mechanism connecting TRPM8 stimulation and c-Fos expression. Furthermore, we analyzed the expression of the neuronal activity-responsive transcription factor Egr-1 following TRPM8 activation. The results show that icilin-induced stimulation of TRPM8 channels increased c-Fos promoter activity and induced c-Fos expression. Moreover, icilin stimulation increased Egr-1 promoter activity and induced the expression of Egr-1. Pharmacological inhibition of TRPM8 blocked the icilin-induced expression of Egr-1 and c-Fos. An influx of Ca2+ ions into the cells via TRPM8 was necessary to stimulate Egr-1 and c-Fos expression following icilin treatment. Genetic experiments revealed that serum response elements within the Egr-1 and c-Fos promoters are crucial to couple TRPM8 stimulation with enhanced transcription of both the Egr-1 and c-Fos genes. These data were corroborated by experiments showing that TRPM8 stimulation increased the transcriptional activation potential of Elk-1, a SRE binding protein. c-Fos is important for neuronal excitability and survival. Egr-1 plays an important role in synaptic plasticity, consolidation and reconsolidation of long-term memory. Elk-1 may preserve neurons against toxic insults but may also induce depressive behaviour. The fact that TRPM8 stimulation activates the transcription factors c-Fos, Egr-1, and Elk-1 connects TRPM8 signaling with maintaining important brain functions.

Calcineurin controls gene transcription following stimulation of a Gαq-coupled designer receptor

Stimulation of Gaq-coupled receptors triggers the activation of gene transcription via a rise of intracellular Ca2+. To investigate the role of the Ca2+/calmodulin-dependent phosphatase calcineurin in regulating transcription following Gαq-coupled receptor stimulation, we used a gain-of-function approach and expressed ΔCnA, a constitutively active mutant of calcineurin A. Furthermore, we expressed hM3Dq, a designer receptor that is specifically coupled to Gαq and can be activated by the pharmacological compound clozapine-N-oxide. Stimulation of hM3Dq or expression of ΔCnA induced transcription of a reporter gene controlled by the calcineurin substrate nuclear factor of activated T cells (NFAT), suggesting that calcineurin increased NFAT-regulated gene transcription. In contrast, expression of ΔCnA attenuated hM3Dq-induced biosynthesis of the transcription factors c-Fos and Egr-1 and reduced both c-Fos and Egr-1 promoter activities. A dissection of the c-Fos and Egr-1 promoters revealed that calcineurin inhibited serum response element-mediated transcription. In particular, the expression of ΔCnA reduced the transcriptional activity of the ternary complex factor Elk-1 following stimulation of hM3Dq receptors. Furthermore, ΔCnA reduced the transcriptional activity of the transcription factor CREB and thus attenuated transcription mediated by the cAMP response element. In summary, we show that calcineurin functions as a positive and negative modulator of gene transcription.

RSK2-Mediated ELK3 Activation Enhances Cell Transformation and Breast Cancer Cell Growth by Regulation of c-fos Promoter Activity.

Ribosomal S6 kinase 2 (RSK2), regulated by Ras/Raf/MEKs/ERKs, transmits upstream activation signals to downstream substrates including kinases and transcription and epigenetic factors. We observed that ELK members, including ELK1, 3, and 4, highly interacted with RSK2. We further observed that the RSK2-ELK3 interaction was mediated by N-terminal kinase and linker domains of RSK2, and the D and C domains of ELK3, resulting in the phosphorylation of ELK3. Importantly, RSK2-mediated ELK3 enhanced c-fos promoter activity. Notably, chemical inhibition of RSK2 signaling using kaempferol (a RSK2 inhibitor) or U0126 (a selective MEK inhibitor) suppressed EGF-induced c-fos promoter activity. Moreover, functional deletion of RSK2 by knockdown or knockout showed that RSK2 deficiency suppressed EGF-induced c-fos promoter activity, resulting in inhibition of AP-1 transactivation activity and Ras-mediated foci formation in NIH3T3 cells. Immunocytofluorescence assay demonstrated that RSK2 deficiency reduced ELK3 localization in the nucleus. In MDA-MB-231 breast cancer cells, knockdown of RSK2 or ELK3 suppressed cell proliferation with accumulation at the G1 cell cycle phase, resulting in inhibition of foci formation and anchorage-independent cancer colony growth in soft agar. Taken together, these results indicate that a novel RSK2/ELK3 signaling axis, by enhancing c-Fos-mediated AP-1 transactivation activity, has an essential role in cancer cell proliferation and colony growth.

Abstract 3456: Molecular mechanisms of RSK2-ELK3 signaling axis in neoplastic cell transformation

Abstract Constitutive active Ras mutation (RasG12V) plays a key role in cell proliferation and transformation in many solid human cancers. RSK2, a member of p90RSK superfamily, controlled by ERKs is an intermediate signaling molecule transducing Ras activation signal to downstream substrates including transcription factors, epigenetic factors and some kinases. Since RSK2 shows wide range of substrate spectrum, identification of RSK2's novel substrates is important to understand the role of RSK2 in cancer. We found that ELKs including ELK1, ELK3 and ELK4 are novel interaction partners of RSK2 by mammalian two-hybrid assay. In vitro kinase assay and immunoprecipitation assay indicated that ELK3 is a major binding partner of RSK2. Luciferase reporter assay demonstrated that ELK3 transactivation activity was increased by RSK2, resulted in the increase of c-fos promoter activity. Importantly, constitutive active (CA)-RasG12V-mediated foci formation in NIH3T3 cells were more increased by ectopic co-expression of CA-RasG12V and RSK2. Additionally, signaling blockage of the CA-RasG12V/ELK3 by RSK2 knockdown suppressed foci formation. These results demonstrated that RSK2-ELK3 signaling axis plays an important role in RasG12V-mediated neoplastic cell transformation. Key words : MAPK, RSK2, ELKs, cell proliferation, cell transformation Citation Format: Seon-Yeon Cho, Cheol-Jung Lee, Sun-Mi Yoo, Seung-Min Kim, Juhee Park, Yong-Yeon Cho. Molecular mechanisms of RSK2-ELK3 signaling axis in neoplastic cell transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3456.

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.

Stimulation of B-Raf increases c-Jun and c-Fos expression and upregulates AP-1-regulated gene transcription in insulinoma cells.

Stimulation of pancreatic β-cells with glucose activates the protein kinases B-Raf and extracellular signal-regulated protein kinase that participate in glucose sensing. Inhibition of both kinases results in impairment of glucose-regulated gene transcription. To analyze the signaling pathway controlled by B-Raf, we expressed a conditionally active form of B-Raf in INS-1 insulinoma cells. Here, we show that stimulation of B-Raf strongly activated the transcription factor AP-1 which is accompanied by increased c-Jun and c-Fos promoter activities, an upregulation of c-Jun and c-Fos biosynthesis, and elevated transcriptional activation potentials of c-Jun and c-Fos. Mutational analysis identified the AP-1 sites within the c-Jun promoter and the serum response element (SRE) within the c-Fos promoter as the essential genetic elements connecting B-Raf stimulation with AP-1 activation. In line with this, the transcriptional activation potential of the SRE-binding protein Elk-1 was increased following B-Raf activation. The signal pathway from B-Raf to AP-1 required the activation of c-Jun. We identified the cyclin D1 gene as a delayed response gene for AP-1 following stimulation of B-Raf in insulinoma cells. Moreover, MAP kinase phosphatase-1 and the Ca2+/calmodulin-dependent protein phosphatase calcineurin were identified to function as shut-off-devices for the signaling cascade connecting B-Raf stimulation with the activation of AP-1. The fact that stimulation with glucose, activation of L-type voltage-gated Ca2+ channels, and stimulation of B-Raf all trigger an activation of AP-1 indicates that AP-1 is a point of convergence of signaling pathways in β-cell.

Extracellular Signal-Regulated Protein Kinase, c-Jun N-Terminal Protein Kinase, and Calcineurin Regulate Transient Receptor Potential M3 (TRPM3) Induced Activation of AP-1

Stimulation of transient receptor potential M3 (TRPM3) cation channels with pregnenolone sulfate induces an influx of Ca2+ ions into the cells and a rise in the intracellular Ca2+ concentration, leading to the activation of the activator protein-1 (AP-1) transcription factor. Here, we show that expression of a constitutively active mutant of the Ca2+ /calmodulin-dependent protein phosphatase calcineurin attenuated pregnenolone sulfate-induced AP-1 activation in TRPM3-expressing cells. Likewise, expression of the regulatory B subunit of calcineurin reduced AP-1 activity in the cells following stimulation of TRPM3 channels. MAP kinase phosphatase-1 has been shown to attenuate TRPM3-mediated AP-1 activation. Here, we show that pregnenolone sulfate-induced stimulation of TRPM3 triggers the phosphorylation and activation of the MAP kinase extracellular signal-regulated protein kinase (ERK1/2). Pharmacological and genetic experiments revealed that stimulation of ERK1/2 is essential for the activation of AP-1 in cells expressing stimulated TRPM3 channels. ERK1/2 is required for the activation of the transcription factor c-Jun, a key component of the AP-1 transcription factor, and regulates c-Fos promoter activity. In addition, we identified c-Jun N-terminal protein kinase (JNK1/2) as a second signal transducer of activated TRPM3 channels. Together, the data show that calcineurin and the protein kinases ERK1/2 and JNK1/2 are important regulators within the signaling cascade connecting TRPM3 channel stimulation with increased AP-1-regulated transcription. J. Cell. Biochem. 118: 2409-2419, 2017. © 2017 Wiley Periodicals, Inc.

Hyperforin activates gene transcription involving transient receptor potential C6 channels

Hypericum perforatum is one of the most prominent medical plants. Hyperforin, a main ingredient of H. perforatum, has been shown to activate transient receptor potential canonical C6 (TRPC6) channels. Alternatively, it has been proposed that hyperforin functions as a protonophore in a TRPC6-independent manner. Here, we show that hyperforin stimulation activates the transcription factor AP-1 in HEK293 cells expressing TRPC6 (T6.11 cells), but did not substantially change the AP-1 activity in HEK293 cells lacking TRPC6. We identified the AP-1 binding site as a hyperforin-responsive element. AP-1 is composed of the transcription factors c-Jun and c-Fos, or other members of the c-Jun and c-Fos families of proteins. Hyperforin stimulation increased c-Jun and c-Fos promoter activities in T6.11 cells and induced an upregulation of c-Jun and c-Fos biosynthesis. The analysis of the c-Fos promoter revealed that the cAMP-response element also functions as a hyperforin-responsive element. Hyperforin-induced upregulation of AP-1 in T6.11 cells was attenuated by preincubation of the cells with either pregnenolone or progesterone, indicating that gene regulation via TRPC6 is under control of hormones or hormonal precursors. The signal transduction of hyperforin-induced AP-1 gene transcription required an influx of Ca2+ ions into the cells, the activation of MAP kinases, and the activation of the transcription factors c-Jun and ternary complex factor. We conclude that hyperforin regulates gene transcription via activation of TRPC6 channels, involving stimulus-regulated protein kinases and stimulus-responsive transcription factors. The fact that hyperforin regulates gene transcription may explain many of the intracellular alterations induced by this compound.

Stimulus-specific combinatorial functionality of neuronal c-fos enhancers.

The c-fos gene is induced by a broad range of stimuli, and has been commonly used as a reliable marker for neural activity. Its induction mechanism and available reporter mouse lines are exclusively based on the c-fos promoter activity. Here, we demonstrate that multiple enhancers surrounding the c-fos gene are critical for ensuring robust c-fos response to various stimuli. Membrane depolarization, brain-derived neurotrophic factor (BDNF), and Forskolin activate distinct subsets of the enhancers to induce c-fos transcription in neurons, suggesting that stimulus-specific combinatorial activation of multiple enhancers underlies the broad inducibility of the c-fos gene. Accordingly, the functional requirement of key transcription factors varies depending on the type of stimulation. Combinatorial enhancer activation also occurs in the brain. Providing a comprehensive picture of the c-fos induction mechanism beyond the minimal promoter, our study should help in understanding the physiological nature of c-fos induction in relation to neural activity and plasticity.

P38α MAPK is required for arsenic-induced cell transformation.

Arsenic exposure has been reported to cause neoplastic transformation through the activation of PcG proteins. In the present study, we show that activation of p38α mitogen-activated protein kinase (MAPK) is required for arsenic-induced neoplastic transformation. Exposure of cells to 0.5 μM arsenic increased CRE and c-Fos promoter activities that were accompanied by increases in p38α MAPK and CREB phosphorylation and expression levels concurrently with AP-1 activation. Introduction of short hairpin (sh) RNA-p38α into BALB/c 3T3 cells markedly suppressed arsenic-induced colony formation compared with wildtype cells. CREB phosphorylation and AP-1 activation were decreased in p38α knockdown cells after arsenic treatment. Arsenic-induced AP-1 activation, measured as c-Fos and CRE promoter activities, and CREB phosphorylation were attenuated by p38 inhibition in BALB/c 3T3 cells. Thus, p38α MAPK activation is required for arsenic-induced neoplastic transformation mediated through CREB phosphorylation and AP-1 activation.

Abstract 556: Cot/Tpl2 is required for neoplastic cell transformation induced by interleukin-22: a possible mechanism in breast carcinogenesis.

Abstract Interleukin 22 (IL-22), a member of the IL-10 family of cytokines, is secreted T helper 17 (Th17) cells. Although IL-22 was recently reported to be a novel inflammation mediator through STAT3 signaling activation, the precise mechanisms of IL-22 in neoplastic cellular transformation and breast carcinogenesis are not well explored yet. Here, we report that IL-22 induced neoplastic transformation of JB6 Cl41 cells through activation of Cot/Tpl2. IL-22 dose- and time-dependently increased Cot/Tpl2 phosphorylation in JB6 Cl41 cells through IL-22 receptor. IL-22 phosphorylated MEK1/2, JNK1/2 and STAT3, which were inhibited by a specific inhibitor of Cot/Tpl2 kinase. When small interfering RNA (siRNA) of IL-22 and IL-22 receptor (IL-22R) were transfected into JB6 Cl41 cells, IL-22-induced Cot/Tpl2 phosphorylation was markedly decreased, followed by inhibition of MEK-ERK, JNK-c-Jun and STAT3 signaling pathway. Also, IL-22 activated c-fos and c-jun promoter activity, leading to increased activator protein-1 (AP-1) activity, which was suppressed by Cot/Tpl2 inhibitor. The in vivo chorioallantoic membrane (CAM) assay also showed that IL-22 increased tumor growth of JB6 Cl41 cells, whereas Cot/Tpl2 inhibitor suppressed the tumorigenesis induced by IL-22. In addition, knockdown of IL-22 and/or inhibition of Cot/Tpl2 diminished tumorigenecity of human breast cancer SKBR3 cells. Consistent with these observations, immunohistochemical staining showed that both expressions of IL-22 and Cot/Tpl2 proteins were highly upregulated in human breast cancers. Thus, this suggests that Cot/Tpl2 plays a pivotal role in IL-22-induced neoplastic cell transformation, and that Cot/Tpl2 may be the therapeutic target of breast cancer promoted by IL-22. Citation Format: Karam Kim, Hong Seok Choi. Cot/Tpl2 is required for neoplastic cell transformation induced by interleukin-22: a possible mechanism in breast carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 556. doi:10.1158/1538-7445.AM2013-556 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract 1422: Interleukin-17A activates tumor progression locus 2 to induce neoplastic cell transformation and breast carcinogenesis.

Abstract Interleukin-17 (IL-17) is a pro-inflammatory cytokine secreted by activated CD4+ memory T cells. Although the role of T cells in cancer promotion has been examined, little is known about the underlying molecular mechanisms of interleukin-17 A (IL-17A) in carcinogenesis. In the present study, we first found that IL-17A induces neoplastic transformation of JB6 Cl41 cells through activation of tumor progression locus 2 (TPL2). IL-17A activates MEKs-ERKs, JNKs-c-Jun, and STAT3 signaling pathways, which are inhibited by a TPL2 kinase inhibitor (TKI). Furthermore, IL-17A activates c-fos and c-jun promoter activity, resulting in increased activator protein-1 (AP-1) activity. When small interfering RNA (siRNA) of IL-17A receptor (IL-17R), IL-17A, and TPL2 were introduced into JB6 Cl41 cells, respectively, IL-17A-induced AP-1 activity was significantly decreased compared to control cells. Similarly, TPL2 inhibition suppressed AP-1 activity induced by IL-17A. The knockdown of IL-17R and TKI treatment in JB6 Cl41 cells resulted in decreased IL-17A-induced cell transformation. The in vivo chorioallantoic membrane (CAM) assay also showed that IL-17A increased tumor formation of JB6 Cl41 cells, whereas TKI inhibited the tumorigenesis promoted by IL-17A. Consistent with these observations, knockdown of IL-17A and/or inhibition of TPL2 attenuated tumorigenecity of human breast cancer MCF7 cells. Moreover, immunohistochemical staining showed that both expressions of IL-17A and TPL2 were highly upregulated in human breast cancers. Together, our findings point to a critical role for the IL-17A-induced TPL2 signaling pathway in supporting cancer-associated inflammation in the tumor microenvironment. Therapeutic approaches that target this pathway may therefore effectively inhibit carcinogenesis. Citation Format: Garam Kim, Hong Seok Choi. Interleukin-17A activates tumor progression locus 2 to induce neoplastic cell transformation and breast carcinogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1422. doi:10.1158/1538-7445.AM2013-1422 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Interleukin-17 induces AP-1 activity and cellular transformation via upregulation of tumor progression locus 2 activity

Inflammatory conditions elicited by extrinsic environmental factors promote malignant transformation, tumor growth and metastasis. Although the role of T cells in cancer promotion has been examined, little is known about the underlying molecular mechanisms of interleukin-17 A (IL-17A), a proinflammatory cytokine produced by activated CD4(+) memory T cells, in carcinogenesis. Here, we report that IL-17A induces neoplastic transformation of JB6 Cl41 cells through activation of tumor progression locus 2 (TPL2). IL-17A dose- and time-dependently increases TPL2 phosphorylation in JB6 Cl41 cells through IL-17A receptor. IL-17A activates mitogen-activated protein kinase/extracellular signal-regulated kinase kinases, c-jun N-terminal kinases and STAT3 signaling pathways, which are inhibited by a TPL2 kinase inhibitor (TKI). Furthermore, IL-17A activates c-fos and c-jun promoter activity, resulting in increased activator protein-1 (AP-1) activity. When small interfering RNA of IL-17A receptor (IL-17R), IL-17A and TPL2 were introduced into JB6 Cl41 cells, respectively, IL-17A-induced AP-1 activity was significantly decreased compared with control cells. Similarly, TPL2 inhibition suppressed AP-1 activity induced by IL-17A. The knockdown of IL-17R and TKI treatment in JB6 Cl41 cells resulted in decreased IL-17A-induced cell transformation. The in vivo chorioallantoic membrane assay also showed that IL-17A increased tumor formation of JB6 Cl41 cells, whereas TKI inhibited the tumorigenesis promoted by IL-17A. Consistent with these observations, knockdown of IL-17A and/or inhibition of TPL2 attenuated tumorigenicity of human breast cancer MCF7 cells. Together, our findings point to a critical role for the IL-17A-induced TPL2 signaling pathway in supporting cancer-associated inflammation in the tumor microenvironment. Therapeutic approaches that target this pathway may, therefore, effectively inhibit carcinogenesis.

Abstract 2337: Effect of embryonic stem (ES) cell-conditioned microenvironment on the reprogramming of human cancer

Abstract During embryonic development, the extracellular matrix (ECM) plays a critical role in the regulation of stem cells to different lineages, cell migration and proliferation. A recently developed 3-dimensional (3D) ES-conditioned matrigel matrix culture of metastatic melanoma cells induces reprogramming and differentiation. However, although the ES-cell conditioned microenvironment induces melanoma cell reprogramming to suppress invasive behavior, the mechanisms have not yet been clearly understood. To investigate the effect of the cancer cell microenvironment, we hypothesized that 1) the microenvironment might induce nuclear reprogramming; 2) microenvironment-induced reprogramming might affect cell proliferation; 3) microenvironment-induced reprogramming might induce differentiation-mediated cellular senescence; and 4) microenvironment-induced reprogramming causes a loss of anchorage-independent cell growth, which is a hallmark of cancer cell properties. Here, we found that the ES-conditioned 3D-microenvironment induced a dramatic change in the morphology of A431 human skin epidermoid carcinoma cells and SK-MEL-28 human skin malignant melanoma cells. In the anchorage-independent cell growth assay, we found that A431 and SK-MEL-28 cells grown in the 3D ES-conditioned microenvironment exhibited dramatically decreased colony growth in soft agar. Real time PCR analysis indicated that ES-conditioned microenvironment suppressed endogenous Oct4 and Nanog gene expression in A431 and SK-MEL-28 cells and inhibited c-jun and c-fos promoter activities, which are components of the AP-1 transcriptional factor complex. Very importantly, we found that the ES cell-conditioned microenvironment inhibited telomerase activity, resulting in the induction of cellular senescence in human skin melanoma cells. We found that ES-conditioned medium contained a greater amount of Gremlin, a natural inhibitor of TGF-β signaling. Gremlin treatment of A431 and SK-MEL-28 cells induced morphological changes as observed in the 3D ES-conditioned matrigel matrix. Our results demonstrated that the ES-cell conditioned microenvironment inhibited proliferation and induced cellular senescence of A431 and SK-Mel-28 cells through the inhibition of TGF-β signaling by Gremlin. Furthermore, our data strongly suggests that modulation of TGF-β signaling in the cancer microenvironment is a potential strategy to modulate cancer cell behaviors and properties. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2337.

Bioluminescence imaging of c-fos gene expression accompanying filial imprinting in the newly hatched chick brain

Bioluminescence imaging is a powerful tool for examining gene expression in living animals. Previously, we reported that exogenous DNA could be successfully delivered into neurons in the newly hatched chick brain using electroporation. Here, we show the in vivo bioluminescence imaging of c-fos promoter activity and its upregulation, which is associated with filial imprinting. The upregulation of c-fos gene expression correlated with both the strength of the chicks’ approach activity to the training object and the acquisition of memory. The present technique should be a powerful tool for analyzing the time changes in neural activity of certain brain areas in real-time during memory formation, using brains of living animals.

Abstract A46: Tpl-2 kinase downregulates the activity of p53 and enhances signaling pathways leading to activation of activator protein 1 induced by EGF

Abstract Tumor progression locus-2 (Tpl-2) kinase is a member of the mitogen-activated protein kinase (MAPK) kinase kinase family that has been implicated in cellular transformation. The enhanced expression of this protein has been shown to activate both the MAPK and c-Jun N-terminal kinase (JNK) pathways. However the molecular mechanisms responsible for the oncogenic potential of Tpl-2 are still largely unknown. Here, we show that Tpl-2 interacts with p53 both in vitro and ex vivo. The overexpression of Tpl-2 inhibits the phosphorylation of p53 at serine 15 induced by EGF by upregulating the activity of protein phosphatase 2A (PP2A). In addition, the EGF-induced p53 activity was suppressed in the Tpl-2-wild-type-transfeted HEK 293 cells, but had no effect in the Tpl-2-mutant (S413A)-transfected cells. Furthermore, the Tpl-2 wild type, but not Tpl-2 mutant (S413A), showed increased EGF-induced c-fos promoter activity, followed by AP-1 transactivation activity, which is associated with the cell transformation prompted by the H-Ras-Tpl-2-AP-1 signaling axis. These results suggest that Tpl-2 plays an important role in EGF-induced carcinogenesis by inactivating the p53 tumor suppressor. Citation Information: Cancer Res 2009;69(23 Suppl):A46.