Histone deacetylase inhibitors suppress the induction of c-Jun and its target genes including COX-2

Complexity of COX-2 gene regulation

Overexpression of the enzyme COX-2 (cyclo-oxygenase-2) is associated with various pathophysiological conditions, including inflammatory diseases and different cancers. Increased synthesis of COX-2 in fetal membranes and the myometrium is also linked with the onset of term and preterm labour. COX-2 gene regulation is controlled at various levels including gene transcription and post-transcriptional events. The present article focuses on the complexity of COX-2 gene regulation and reviews current concepts that highlight: (i) transcription of COX-2 is induced rapidly and transiently in response to a plethora of stimuli; (ii) COX-2 mRNA stability and translational efficiency is governed by multiple regulatory elements within the 3'-untranslated region; (iii) specific microRNAs and RNA-binding proteins influence COX-2 mRNA stability; and (iv) regulation of COX-2 involves alternative polyadenylation.

Histone deacetylase inhibitors suppress interleukin-1beta-induced nitric oxide and prostaglandin E2 production in human chondrocytes

OBJECTIVE

Overproduction of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) plays an important role in the pathogenesis of osteoarthritis (OA). In the present study, we determined the effect of trichostatin A (TSA) and butyric acid (BA), two histone deacetylase (HDAC) inhibitors, on NO and PGE(2) synthesis, inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 expression, and nuclear factor (NF)-kappaB DNA-binding activity, in interleukin-1beta (IL-1)-stimulated human OA chondrocytes, and on IL-1-induced proteoglycan degradation in cartilage explants.

METHODS

Chondrocytes were stimulated with IL-1 in the absence or presence of increasing concentrations of TSA or BA. The production of NO and PGE(2) was evaluated using Griess reagent and an enzyme immunoassay, respectively. The expression of iNOS and COX-2 proteins and mRNAs was evaluated using Western blotting and real-time reverse transcriptase-polymerase chain reaction (RT-PCR), respectively. Proteoglycan degradation was measured with dimethymethylene blue assay. Electrophoretic mobility shift assay (EMSA) was utilized to analyze the DNA-binding activity of NF-kappaB.

RESULTS

HDAC inhibition with TSA or BA resulted in a dose-dependent inhibition of IL-1-induced NO and PGE(2) production. IL-17- and tumor necrosis factor-alpha (TNF-alpha)-induced NO and PGE(2) production was also inhibited by TSA and BA. This inhibition correlated with the suppression of iNOS and COX-2 protein and mRNA expression. TSA and BA also prevented IL-1-induced proteoglycan release from cartilage explants. Finally, we demonstrate that the DNA-binding activity of NF-kappaB, was induced by IL-1, but was not affected by treatment with HDAC inhibitors.

CONCLUSIONS

These data indicate that HDAC inhibitors suppressed IL-1-induced NO and PGE(2) synthesis, iNOS and COX-2 expression, as well as proteoglycan degradation. The suppressive effect of HDAC inhibitors is not due to impaired DNA-binding activity of NF-kappaB. These findings also suggest that HDAC inhibitors may be of potential therapeutic value in the treatment of OA.

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1/GDF15) expression is increased by the histone deacetylase inhibitor trichostatin A

Nonsteroidal anti-inflammatory drug-activated gene (NAG-1) is a putative tumor suppressor whose expression can be increased by drug treatment. Glioblastoma is the most common central nervous system tumor, is associated with high morbidity and mortality, and responds poorly to surgical, chemical, and radiation therapy. The histone deacetylase inhibitors are under current consideration as therapeutic agents in treating glioblastoma. We investigated whether trichostatin A (TSA) would alter the expression of NAG-1 in glioblastoma cells. The DNA demethylating agent 5-aza-dC did not increase NAG-1 expression, but TSA up-regulated NAG-1 expression and acted synergistically with 5-aza-dC to induce NAG-1 expression. TSA indirectly increases NAG-1 promoter activity and increases NAG-1 mRNA and protein expression in the T98G human glioblastoma cell line. TSA also increases the expression of transcription factors Sp-1 and Egr-1. Small interfering RNA experiments link NAG-1 expression to apoptosis induced by TSA. Reporter gene assays, specific inhibition by small interfering RNA transfections, and chromatin immunoprecipitation assays indicate that Egr-1 and Sp-1 mediate TSA-induced NAG-1 expression. TSA also increases the stability of NAG-1 mRNA. TSA-induced NAG-1 expression involves multiple mechanisms at the transcriptional and post-transcriptional levels.

Trichostatin A, a histone deacetylase inhibitor, suppresses synovial inflammation and subsequent cartilage destruction in a collagen antibody-induced arthritis mouse model

OBJECTIVE

To investigate the effect of the histone deacetylase (HDAC) inhibitor, trichostatin A (TSA), on joint inflammation and cartilage degeneration in a collagen antibody-induced arthritis (CAIA) mouse model.

METHODS

CAIA mice were given daily subcutaneous injections of various concentrations of TSA (0, 0.5, 1.0, and 2.0 mg/kg) and various parameters were monitored for 14 days. On Day 15, the hind paws were examined histologically. To investigate the effects of TSA on the expressions of matrix metalloproteinase (MMP)-3, MMP-13, tissue inhibitor of MMP-1 (TIMP-1), and acetyl-H4 by chondrocytes, another group of mice was sacrificed on Day 6. In vitro direct effect of TSA was examined by real-time PCR for mRNA of type II collagen, aggrecan, MMP-3, and MMP-13 in murine chondrogenic ATDC5 cells after pro-inflammatory cytokine stimulation.

RESULTS

In the TSA-treated group, clinical arthritis was significantly ameliorated in a dose-dependent manner. The severity of synovial inflammation and the cartilage destruction score were significantly lower in the TSA 2.0 mg/kg group compared to the other TSA-treated groups. On immunohistochemistry, the number of MMP-3 and MMP-13-positive chondrocytes was significantly lower in the TSA 2.0 mg/kg group than in the control group. In contrast, the number of TIMP-1-positive cells and acetyl-histone H4-positive cells was significantly higher in the TSA 2.0mg/kg group than in the control group. TSA suppressed interleukin 1-beta and tumor necrosis factor-alpha-stimulated up-regulation of MMP-3, but not MMP-13 mRNA expression by ATDC5.

CONCLUSION

The systemic administration of TSA ameliorated synovial inflammation in CAIA mice. Subsequently cartilage destruction was also suppressed by TSA, at least in part, by modulating chondrocyte gene expression.

HDAC3 overexpression and colon cancer cell proliferation and differentiation

An immunohistochemical analysis of human colorectal adenocarcinomas showed that cancer cells express widely varying levels of HDAC3. The SW480 colon cancer cell line was found to express high levels of HDAC3 compared to other colon cancer cell lines. p21 was poorly induced in SW480 cells relative to the lower HDAC3-expressing HT-29 cells. RNAi-induced reduction of HDAC3 in SW480 cells increased their constitutive, butyrate-, TSA-, and TNF-alpha-induced expression of p21, but did not cause all the gene expression changes induced upon general histone deacetylase (HDAC) inhibition. SW480 cells with lower HDAC3 expression appeared to be poised for gene expression responses with increased histone H4-K12 acetylation, but not K5, K8, or K16 acetylation. Even though p21 was readily activated in HT29 cells, HDAC3 siRNA nonetheless stimulated p21 expression in these cells to a greater degree than HDAC1 and HDAC2 siRNA. SW480 cells with lower HDAC3 levels displayed an enhanced cell cycle arrest and growth inhibition by butyrate, but without changes in apoptosis or sensitivity to chemotherapeutic agents. As reported for other colon cancer cell lines, butyrate induced the rapid downregulation of the secretory cell differentiation markers mucin 2 and intestinal trefoil factor in SW480 cells. Interestingly, selective HDAC3 inhibition was sufficient to downregulate these genes. Our data support a central role for HDAC3 in regulating the cell proliferation and differentiation of colon cancer cells and suggest a potential mechanism by which colon cancers may become resistant to luminal butyrate.

Histone deacetylase inhibitors exert time-dependent effects on nuclear factor-kappaB but consistently suppress the expression of proinflammatory genes in human myometrial cells

Premature activation of the inflammatory processes that mediate human parturition leads to preterm birth, a major clinical problem associated with neonatal morbidity and mortality. Histone deacetylase inhibitors (HDACi) are currently in clinical trials for the treatment of inflammatory disorders. Recent evidence suggests that there may be a therapeutic use for HDACi in the management of preterm birth, with administration of HDACi to pregnant mice shown to delay delivery. Because NF-kappaB is a key orchestrator of the inflammatory response and plays a pivotal role in parturition, it is important to understand how administration of HDACi might affect NF-kappaB activity in human uterine tissues. We show here that the effects of HDACi on nuclear factor-kappaB (NF-kappaB) in human myometrial cells are time-dependent. Short-term exposure to HDACi enhanced interleukin (IL)-1beta-induced NF-kappaB activity as a result of potentiating IkappaB kinase (IKK)beta activity, thereby leading to persistent turnover of IkappaBalpha/epsilon proteins and prolonging NF-kappaB phosphorylation, nuclear localization, and DNA binding. Conversely, long-term HDACi treatments resulted in repression of NF-kappaB DNA binding. Nevertheless, both short- and long-term HDACi treatments inhibited the expression of four labor-associated proinflammatory genes (COX-2, IL-8, IL-6, and RANTES), and this was associated with repression of the proinflammatory transcription factor c-Jun. Together, our data indicate that HDACi exert anti-inflammatory effects in human myometrium and may thus be useful in achieving a myometrial gene expression profile that favors uterine quiescence. However, coadministration of an IKKbeta inhibitor may be both necessary and sufficient to circumvent potential induction of labor-associated pathways that could result from HDACi-induced augmentation of NF-kappaB activity.

A shifting paradigm: histone deacetylases and transcriptional activation

Transcriptional repression and silencing have been strongly associated with hypoacetylation of histones. Accordingly, histone deacetylases, which remove acetyl groups from histones, have been shown to participate in mechanisms of transcriptional repression. Therefore, current models of the role of acetylation in transcriptional regulation focus on the acetylation status of histones and designate histone acetyltransferases, which add acetyl groups to histones, as transcriptional coactivators and histone deacetylases as corepressors. In recent years, an accumulation of studies have shown that these enzymes also target non-histone proteins and that histone deacetylases have clear roles as coactivators at a variety of genes, some of which are key regulators of cell growth and survival. This review summarizes the evidence for histone deacetylases as coactivators and provides models of coactivation mechanisms, some of which integrate roles of acetylated histones and non-histone proteins in transcription.

Thyroid hormone receptor-beta (TR beta 1) impairs cell proliferation by the transcriptional inhibition of cyclins D1, E and A2

Thyroid hormone receptor-beta1 (TRbeta1) belongs to the ligand-inducible transcription factor superfamily. We have previously described that stable TRbeta1 expression impairs fibroblast proliferation diminishing levels and activity of the main regulators of the G(1)/S transition. To unmask the underlying molecular mechanism of this action, we have investigated the expression of cyclin D1, E and A2 upon serum stimulation in TRbeta1 expressing cells, finding a strong downregulation of their mRNAs, concomitant with low protein levels. The inhibition of the transcriptional activation in response to serum of these cyclins is differently exerted. For cyclin D1, we demonstrate that TRbeta1 represses its promoter as a consequence of the downregulation of c-jun levels, diminished AP-1 activation and loss of c-jun recruitment to its binding sites on cyclin D1 promoter. For cyclin E and A2, it is the impairment of the cyclinD/Rb/E2F pathway by TRbeta1 that prevents the activation of these two E2F target genes. Indeed, recruitment of E2F-1 to cyclin A2 promoter could not be detected. In summary, we propose that apo-TRbeta1 exerts its antiproliferative action through a mechanism that could constitute a model by which other nuclear receptors may control cell division.

Suppression of IL-1β-induced COX-2 expression by trichostatin A (TSA) in human endometrial stromal cells

OBJECTIVE

Over-production of cyclooxygenase-2 (COX-2) plays an important role in the positive feedback loop that leads to proliferation and inflammation in endometriosis. Following our observation that histone deacetylase inhibitors (HDACIs) trichostatin A (TSA) and valproic acid (VPA) can suppress proliferation of endometrial stromal cells, we sought to determine whether TSA suppresses IL-1beta-induced COX-2 expression in endometrial stromal cells.

STUDY DESIGN

In vitro study using a recently established immortalized endometrial stromal cell line. The stromal cells were pretreated with TSA before stimulation with IL-1beta, and COX-2 gene and protein expression was measured by real-time quantitative RT-PCR and Western blot analysis, respectively.

RESULTS

IL-1beta stimulated COX-2 expression in a concentration-dependent manner in endometrial stromal cells. The induced COX-2 gene and protein expression were suppressed by TSA pretreatment.

CONCLUSIONS

TSA suppresses IL-1beta-induced COX-2 gene and protein expression in endometrial stromal cells. This finding, coupled with the findings that TSA and another HDACI, valproic acid, suppress proliferation and induce cell cycle arrest, suggests that HDACIs are a promising class of compound that has therapeutic potential for endometriosis.

Antifibrogenic effects of histone deacetylase inhibitors on pancreatic stellate cells

Pancreatic stellate cells (PSCs) are essentially involved in pancreatic fibrogenesis and considered as a target for antifibrotic therapies. Here, we have analyzed the effects of three histone deacetylase inhibitors (HDACIs), sodium butyrate, sodium valproate (VPA) and trichostatin A (TSA), on profibrogenic activities of PSC and elucidated molecular targets of HDACI action. Therefore, cultured PSCs were exposed to HDACI. Cell proliferation and viability were assessed by 5-bromo-2'-deoxyuridine (BrdU) incorporation and trypan blue staining assays. Exhibition of the myofibroblastic PSC phenotype was monitored by immunofluorescence analysis of alpha-smooth muscle actin (alpha-SMA) expression. [(3)H]-proline incorporation into acetic acid-soluble proteins was measured to quantify collagen synthesis. Levels of mRNA were determined by quantitative reverse transcriptase real-time PCR. Protein expression, phosphorylation and acetylation were analyzed by immunoblotting, and gel shift assays were performed to study DNA binding of nuclear proteins. HDACI enhanced histone H3 acetylation in a dose-dependent manner. In the same dose range, they strongly inhibited cell proliferation, alpha-SMA expression and collagen synthesis. A significantly increased rate of cell death was observed in response to TSA at 1 microM. While all three HDACI inhibited mRNA expression of endothelin-1, only VPA significantly reduced expression of transforming growth factor-beta1. Both mediators exert autocrine profibrogenic effects on PSC. Furthermore, HDACI-treated PSC displayed a diminished DNA binding of AP-1, a key transcription factor in profibrogenic signaling. Together, the results suggest that HDACI exert antifibrogenic effects on PSC. Interruption of AP-1 signaling and autocrine loops enhancing PSC activation might be key mechanisms of HDACI action.

Pathogenesis of colorectal carcinoma and therapeutic implications: the roles of the ubiquitin-proteasome system and Cox-2

Pathways of the molecular pathogenesis of colorectal carcinoma have been extensively studied and molecular lesions during the development of the disease have been revealed. High up in the list of colorectal cancer lesions are APC (adenomatous polyposis coli), K-ras, Smad4 (or DPC4-deleted in pancreatic cancer 4) and p53 genes. All these molecules are part of important pathways for the regulation of cell proliferation and apoptosis and as a result perturbation of these processes lead to carcinogenesis. The ubiquitin-proteasome system (UPS) is comprised of a multi-unit cellular protease system that regulates several dozens of cell proteins after their ligation with the protein ubiquitin. Given that among these proteins are regulators of the cell cycle, apoptosis, angiogenesis, adhesion and cell signalling, this system plays a significant role in cell fate and carcinogenesis. UPS inhibition has been found to be a pre-requisite for apoptosis and is already clinically exploited with the proteasome inhibitor bortezomib in multiple myeloma. Cyclooxygenase-2 (Cox-2) is the inducible form of the enzyme that metabolizes the lipid arachidonic acid to prostaglandin H2, the first step of prostaglandins production. This enzyme is up-regulated in colorectal cancer and in several other cancers. Inhibition of Cox-2 by aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been found to inhibit proliferation of colorectal cancer cells and in epidemiologic studies has been shown to reduce colon polyp formation in genetically predisposed populations and in the general population. NSAIDs have also Cox-independent anti-proliferative effects. Targeted therapies, the result of increasingly understanding carcinogenesis in the molecular level, have entered the field of anti-neoplastic treatment and are used by themselves and in combination with chemotherapy drugs. Combinations of targeted drugs have started also to be investigated. This article reviews the molecular pathogenesis of colorectal cancer, the roles of UPS and Cox-2 in it and puts forward a rational for their combined inhibition in colorectal cancer treatment.

Histone deacetylase inhibitors decrease Toll-like receptor-mediated activation of proinflammatory gene expression by impairing transcription factor recruitment

Post-translational modifications of histone proteins are major mechanisms that modify chromatin structure and regulate gene expression in eukaryotes. Activation of histone acetyltransferases or inhibition of histone deacetylases (HDACs) is generally believed to allow chromatin to assume a more open state, permitting transcriptional activity. We report here the surprising observation that treatment of murine dendritic cells with the HDAC inhibitors trichostatin A (TSA) or suberoylanilide hydroxamic acid (SAHA) in non-apoptotic concentrations strongly inhibited induction of both interleukin-12 protein p40 (IL-12p40) mRNA and protein upon stimulation of Toll-like receptors (TLRs). Moreover, TLR-mediated up-regulation of costimulatory molecules was also inhibited. Up-regulation of tumour necrosis factor-alpha mRNA and protein in response to TLR agonists was only affected upon prolonged exposure to HDAC inhibitors and regulation of IL-1 beta was not affected. Similar effects were apparent in murine and human macrophages. Regarding the mode of action, HDAC inhibition increased the acetylation status at the IL-12p40 locus. Nevertheless, IL-12p40 chromatin remodelling, binding of Rel-A and IRF1 to the IL-12p40 promoter and transcriptional activation were abrogated. In contrast, HDAC inhibitors had no effects on upstream nuclear factor-kappaB and mitogen-activated protein kinase activation. Thus HDACs positively regulate the expression of a subset of cytokine genes by enabling transcription factor recruitment.

Cranberry components inhibit interleukin-6, interleukin-8, and prostaglandin E production by lipopolysaccharide-activated gingival fibroblasts

Periodontitis is a chronic inflammatory disease that affects the tooth supporting tissues. Gingival fibroblasts are the most abundant cells in periodontal tissues and participate actively in the host inflammatory response to periodontopathogens, which is known to mediate local tissue destruction in periodontitis. The aim of this study was to investigate the effect of a proanthocyanidin-enriched cranberry fraction, prepared from cranberry juice concentrate, on inflammatory mediator production by gingival fibroblasts stimulated by the lipopolysaccharide (LPS) of Aggregatibacter actinomycetemcomitans. Interleukin (IL)-6, IL-8, and prostaglandin E(2) (PGE(2)) production by fibroblasts treated with the cranberry fraction and stimulated by A. actinomycetemcomitans LPS was evaluated by enzyme-linked immunosorbent assay. Changes induced by A. actinomycetemcomitans LPS and the cranberry fraction in the expression and phosphorylation state of fibroblast intracellular signaling proteins were characterized by antibody microarrays. The LPS-induced IL-6, IL-8, and PGE(2) responses of gingival fibroblasts were inhibited by treatment with the cranberry fraction. This fraction was found to inhibit fibroblast intracellular signaling proteins, a phenomenon that may lead to a down-regulation of activating protein-1 activity. Cranberry components also reduced cyclooxygenase 2 expression. This study suggests that cranberry juice contains molecules with interesting properties for the development of new host-modulating therapeutic strategies in the adjunctive treatment of periodontitis.

The activator protein-1 transcription factor in respiratory epithelium carcinogenesis

Respiratory epithelium cancers are the leading cause of cancer-related death worldwide. The multistep natural history of carcinogenesis can be considered as a gradual accumulation of genetic and epigenetic aberrations, resulting in the deregulation of cellular homeostasis. Growing evidence suggests that cross-talk between membrane and nuclear receptor signaling pathways along with the activator protein-1 (AP-1) cascade and its cofactor network represent a pivotal molecular circuitry participating directly or indirectly in respiratory epithelium carcinogenesis. The crucial role of AP-1 transcription factor renders it an appealing target of future nuclear-directed anticancer therapeutic and chemoprevention approaches. In the present review, we will summarize the current knowledge regarding the implication of AP-1 proteins in respiratory epithelium carcinogenesis, highlight the ongoing research, and consider the future perspectives of their potential therapeutic interest.

Characterization of cellular retinoid-binding proteins in human myometrium during pregnancy

Many complementary or competing signalling pathways bear an influence on the myometrium at any one time, and because the retinoic acid signalling pathway influences differentiation of a wide array of human tissues, this may be one of the determinants of myometrial differentiation during pregnancy. We have explored the novel hypothesis that the retinoids may act as important regulators in controlling the differentiated state of the human myometrium during pregnancy by characterizing the expression profiles for cellular retinoid-binding proteins CRBPI, CRABPI and CRABPII in non-pregnant, pregnant (non-labouring) and labouring human myometrium taken from the functionally distinct upper and lower uterine segments. In addition, we have investigated the effect of all-trans retinoic acid (ATRA) on the expression of several retinoic acid response genes including cyclooxygenase-2 (COX-2) and connexin-43 (Cx-43). Different spatial and temporal patterns of expression were observed for CRBPI, CRABPI and CRABPII within the upper and lower uterine segments through the three trimesters of pregnancy and in labour. Furthermore, the expression of COX-2, Cx-43, CRABPI, the transcription factor c-Jun and the retinoic acid receptor RARbeta altered in response to different concentrations of ATRA, suggesting that the differential expression of cellular retinoid-binding proteins may lead to different levels of retinoic acid being delivered to its nuclear targets, leading to the differential expression of specific target genes within the myometrium during pregnancy.

N-(3-oxo-acyl)homoserine lactones signal cell activation through a mechanism distinct from the canonical pathogen-associated molecular pattern recognition receptor pathways

Innate immune system receptors function as sensors of infection and trigger the immune responses through ligand-specific signaling pathways. These ligands are pathogen-associated products, such as components of bacterial walls and viral nuclear acids. A common response to such ligands is the activation of mitogen-activated protein kinase p38, whereas double-stranded viral RNA additionally induces the phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha). Here we have shown that p38 and eIF2alpha phosphorylation represent two biochemical markers of the effects induced by N-(3-oxo-acyl)homoserine lactones, the secreted products of a number of Gram-negative bacteria, including the human opportunistic pathogen Pseudomonas aeruginosa. Furthermore, N-(3-oxo-dodecanoyl)homoserine lactone induced distension of mitochondria and the endoplasmic reticulum as well as c-jun gene transcription. These effects occurred in a wide variety of cell types including alveolar macrophages and bronchial epithelial cells, requiring the structural integrity of the lactone ring motif and its natural stereochemistry. These findings suggest that N-(3-oxo-acyl)homoserine lactones might be recognized by receptors of the innate immune system. However, we provide evidence that N-(3-oxo-dodecanoyl)homoserine lactone-mediated signaling does not require the presence of the canonical innate immune system receptors, Toll-like receptors, or two members of the NLR/Nod/Caterpillar family, Nod1 and Nod2. These data offer a new understanding of the effects of N-(3-oxo-dodecanoyl)homoserine lactone on host cells and its role in persistent airway infections caused by P. aeruginosa.

NFAT3 is Required for EGF-Induced COX-2 Transcription, but Neither iNOS Transcription Nor Cell Transformation in Cl 41 Cells

Epidermal growth factor (EGF) has been reported to act as a tumor promoter in several tissues, such as skin, in association with the induction of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). However, molecular mechanisms involved in these regulations are not well defined. This study addressed a potential role of nuclear factor of activated T cells 3 (NFAT3) in EGF-induced COX-2 and iNOS transcription and cell transformation in mouse epidermal Cl 41 cells. We found that EGF markedly induced anchorage-independent growth (cell transformation) of Cl 41 cells, as well as COX-2 (> 6-fold) and iNOS (> 5-fold) promoter-dependent transcription. The EGF-induced COX-2 transcription was blocked by knockdown of NFAT3 with NFAT3 siRNA, whereas the transcription of iNOS and cell transformation induced by EGF were not affected. Although our recent studies supported that NFAT3 plays an essential role in chemical carcinogen benzo[a]pyrene-7,8-diol-9,10-epoxide (B[a]PDE)-induced cell transformation, the data presented here demonstrated that NFAT3 is required for EGF-induced COX-2 transcription, but neither iNOS transcription nor cell transformation, indicating that the role of NFAT3 in regulating cell transformation is carcinogen-specific.

Differentiation-associated genes regulated by TPA-induced c-Jun expression via a PKC/JNK pathway in KYSE450 cells

A group of potential differentiation-associated genes had been identified by microarray analysis as c-Jun/AP-1 target genes essential for epithelial differentiation program. Our previous study showed that c-Jun/AP-1 could bind and activate these gene promoters in vivo using chromatin immunoprecipitation. To further understand how the mitogen-activated protein kinase signaling pathways regulate AP-1 activity and expression of c-Jun target genes, our strategy was based on the use of 12-o-tetradecanoylophorbol-13-acetate (TPA) and pharmacological reagents to induce or block c-Jun expression. The mRNA and protein expression of these genes increased in response to TPA-induced c-Jun/AP-1 expression. Inhibitors of JNK (SP600125) and PKC (GF109203X) mainly blocked expression and phosphorylation of c-Jun, while inhibition of MEK-ERK activity with PD98059 (an inhibitor of MEK) had little effect. Expression of involucrin and keratin 4 in response to TPA was attenuated by pretreatments with GF109203X and SP600125, but not PD98059, suggesting involvement of PKC and JNK in this response. Taken together, these results suggested that differentiation-associated genes were regulated by TPA-induced c-Jun/AP-1 mainly via a PKC/JNK pathway in esophageal cancer cell line KYSE450.