Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interleukin (IL)-6 is a pleiotropic cytokine that not only affects the immune system, but also acts in other biological systems and many physiological events in various organs. In a target cell, IL-6 can simultaneously generate functionally distinct or sometimes contradictory signals through its receptor complex, IL-6Ralpha and gp130. One good illustration is derived from the in vitro observations that IL-6 promotes the growth arrest and differentiation of M1 cells through gp130-mediated STAT3 activation, whereas the Y759/SHP-2-mediated cascade by gp130 stimulation has growth-enhancing effects. The final physiological output can be thought of as a consequence of the orchestration of the diverse signaling pathways generated by a given ligand. This concept, the signal orchestration model, may explain how IL-6 can elicit proinflammatory or anti-inflammatory effects, depending on the in vivo environmental circumstances. Elucidation of the molecular mechanisms underlying this issue is a challenging subject for future research. Intriguingly, recent in vivo studies indicated that the SHP-2-binding site- and YXXQ-mediated pathways through gp130 are not mutually exclusive but affect each other: a mutation at the SHP-2-binding site prolongs STAT3 activation, and a loss of STAT activation by gp130 truncation leads to sustained SHP-2/ERK MAPK phosphorylation. Although IL-6/gp130 signaling is a promising target for drug discovery for many human diseases, the interdependence of each signaling pathway may be an obstacle to the development of a nonpeptide orally active small molecule to inhibit one of these IL-6 signaling cascades, because it would disturb the signal orchestration. In mice, a consequence of the imbalanced signals causes unexpected results such as gastrointestinal disorders, autoimmune diseases, and/or chronic inflammatory proliferative diseases. However, lessons learned from IL-6 KO mice indicate that IL-6 is not essential for vital biological processes, but a significant impact on disease progression in many experimental models for human disorders. Thus, IL-6/gp130 signaling will become a more attractive therapeutic target for human inflammatory diseases when a better understanding of IL-6 signaling, including the identification of the conductor for gp130 signal transduction, is achieved.
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PMID:IL-6 signal transduction and its physiological roles: the signal orchestration model. 1268 4

Signal transducers and activators of transcription (STAT) proteins nuclear translocation and transcriptional activity are regulated by diverse protein kinases in response to extracellular stimuli by cytokines, growth factors and stress. Using two melanoma-derived cell lines that exhibit marked differences in basal activities of MAPKs and PI3K-AKT, we studied changes both in STAT activities and in their sensitization to apoptosis. Activating mutations of B-RAF (T1796A) and impaired expression of PTEN are detected in LU1205, but not in FEMX melanoma cells, and are reflected in high basal levels of expression and activities of MAPKs and PI3K-AKT. Treatment with either PD98059 (PD) or LY294002 (LY), the pharmacological inhibitors of MEK-ERK and PI3K, respectively, markedly increased GAS-Luc activity in LU1205, but not in FEMX cells. Tyrosine phosphorylation of STAT3/5 and of JAK2 also increased upon treatment of LU1205 cells with either PD or LY, suggesting that constitutive active MAPK and PI3K signals inhibit tyrosine phosphorylation of JAK/STATs. Treatment of FEMX and LU1205 with PD sensitized the cells to apoptosis, albeit by TNFalpha and TRAIL death cascades, respectively, indicating that additional yet distinct targets are affected by each signaling pathway. Indeed, the combination of LY and PD treatment synergistically increased the apoptosis of LU1205 and FEMX cells. Overall, whereas PI3K and MAPK downregulate JAK-STAT signaling, additional targets are affected by these kinases and sensitizes melanoma to apoptosis via distinct death cascades.
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PMID:ERK and PI3K negatively regulate STAT-transcriptional activities in human melanoma cells: implications towards sensitization to apoptosis. 1282 43

Increased VEGF expression is found in several pathologies characterized by abnormal angiogenesis. Previous studies have shown that the transcription factor STAT3 mediates VEGF gene transcription and its activation. In this study, Western analysis and confocal immunocytochemistry were used to examine STAT3 activation in retinal microvascular endothelial cells (BREC). We found that VEGF rapidly induces STAT3 tyrosine phosphorylation and nuclear translocation. Immunoprecipitation studies also showed that VEGF forms a complex with VEGFR2 only in BREC and not in aortic macrovascular endothelial cells (BAEC). In addition, quantitative real-time RT-PCR analysis of VEGF-induced VEGF expression showed a significant increase in specific mRNA formation only in BREC and not in BAEC, and this effect was significantly reduced by antisense-mediated reduction of STAT3 expression. Furthermore, studies conducted in human dermal microvascular endothelial cells (HDMEC) showed that, in this endothelial cell type, VEGF autocrine expression is also accompanied by STAT3 activation as in BREC. In this study we showed that VEGF can differentially induce STAT3 activation in micro- versus macro-vascular endothelial cells and that this effect is linked to VEGFR2/STAT3 complex formation, which correlates with VEGF autocrine ability to stimulate its own gene expression.
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PMID:VEGF differentially activates STAT3 in microvascular endothelial cells. 1282 81

Granulocytes and mononuclear phagocytes develop from the same myeloid progenitor cells in the bone marrow via distinct differentiation pathways. Yet, it is known that mature macrophages are more resistant than granulocytes to spontaneous apoptosis in cultures without hematopoietic growth factors. This fact suggests that the development of resistance to apoptosis during myeloid differentiation is differentially regulated by a lineage-dependent mechanism. Using primary cultures of human bone marrow cells, we now report that induction of monocytic differentiation into mature macrophages with M-CSF was correlated with a steady and gradual increase in the levels of X-chromosome-linked inhibitor of apotosis (XIAP) and Bcl-2, while induction of granulocytic differentiation with G-CSF had no significant effects on the expression of these proteins. Consistent with this, NF-kappaB activation is linked to monocytic, but not granulocytic differentiation, while ERK or STAT3 activation is not lineage-dependent. Blockade of NF-kappaB activation in mature macrophages resulted in a marked decrease in the levels of XIAP and Bcl-2, which was accompanied with cell death through an apoptotic mechanism. Thus lineage-dependent activation of NF-kappaB is responsible at least in part for the resistance of mature macrophages to 'spontaneous' apoptosis in vitro.
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PMID:Lineage-dependent NF-kappaB activation contributes to the resistance of human macrophages to apoptosis. 1287 53

BACKGROUND: Steroid hormone receptors (SHRs) are members of the superfamily of ligand-activated transcription factors that regulate many biological processes. Co-regulators act as bridging molecules between the SHR and general transcription factors to enhance transactivation of target genes. Previous studies demonstrated that Stat3 is constitutively activated in prostate cancer and can enhance prostate specific antigen (PSA) expression and promote androgen independent growth. In this study, we investigate whether Stat3 can enhance steroid hormone receptors activation. METHODS: CV-1 cells in which plasmids expressing androgen receptor (AR), glucocorticoid receptor (GR), progesterone receptor (PR) or estrogen receptor (ER) were cotransfected with a constitutively active STAT3 mutant. RESULTS: Stat3 stimulates the transcriptional activity of all four SHR tested, AR, GR, PR and ER, in a hormone-dependent manner. Stat3 acts in a synergistic fashion with other coactivators such as SRC-1, pCAF, CBP, and TIF-2 on the transcriptional activity of these SHR. In addition, Stat3 significantly enhanced the sensitivity of androgen receptor in response to androgen. STAT3 did not affect the specificity of AR for other steroid hormones other than androgen or binding of AR to other hormone responsive elements. CONCLUSIONS: These findings suggest that Stat3 can enhance the transactivation of AR, GR, PR and ER, and activated Stat3 could have a role in the development or progression of a hypersensitive AR.
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PMID:Stat3 enhances transactivation of steroid hormone receptors. 1290 56

Different cellular signal transduction cascades are affected by environmental stressors (UV-radiation, gamma-irradiation, hyperosmotic conditions, oxidants). In this study, we examined oxidative stress-evoked signal transduction pathways leading to activation of STATs in A431 carcinoma cells. Oxidative stress, initiated by addition of H2O2 (1-2 mM) to A431 cells, activates STAT3 and, to a lesser extent, STAT1 in dose- and time-dependent manner. Maximum phosphorylation levels were observed after a 2 minutes stimulation at 1-2 mM H2O2. Phosphorylation was blocked by AG1478, a pharmacological inhibitor of the epidermal growth factor receptor tyrosine kinase, implicating intrinsic EGF receptor tyrosine kinase in this process. Consistent with this observation, H2O2-stimulated EGFR tyrosine phosphorylation was abolished by specific Src kinase family inhibitor CGP77675, implicating Src in H2O2-induced EGFR activation. An essential role for Src and JAK2 in STATs activation was suggested by three findings. 1. Src kinase family inhibitor CGP77675 blocked STAT3 and STAT1 activation by H2O2 in a concentration-dependent manner. 2. In Src-/-fibroblasts, activation of both STAT3 and STAT1 by H2O2 was significantly attenuated. 3. Inhibiting JAK2 activity with the specific inhibitor AG490 reduced the level of H2O2-induced STAT3 phosphorylation, but not STAT1 in A431 cells. These data show essential roles for Src and JAK2 inactivation of STAT3. In contrast, H2O2-mediated activation of STAT1 requires only Src kinase activity. Herein, we postulate also that H2O2-induced STAT activation in carcinoma cells involves Src-dependent EGFR transactivation.
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PMID:[STAT1 and STAT3 activation by oxidative stress in A431 cells involves Src-dependent EGF receptor transactivation]. 1452 Oct 54

Mutations in the proto-oncogene c-kit cause constitutive kinase activity of its product, KIT protein, and are associated with human mastocytosis and gastrointestinal stromal tumors (GISTs). Although currently available tyrosine kinase inhibitors are effective in the treatment of GISTs, there has been limited success in the treatment of mastocytosis. 17-Allylamino-17-demethoxygeldanamycin (17-AAG), a benzoquinoid ansamycin antibiotic, which binds to heat shock protein 90 (hsp90) causes destabilization of various hsp90-dependent kinases important in oncogenesis. Treatment with 17-AAG of the mast cell line HMC-1.2, harboring the Asp816Val and Val560Gly KIT mutations, and the cell line HMC-1.1, harboring a single Val560Gly mutation, causes both the level and activity of KIT and downstream signaling molecules AKT and STAT3 to be down-regulated following drug exposure. These data were validated using Cos-7 cells transfected with wild-type and mutated KIT. 17-AAG promotes cell death of both HMC mast cell lines. In addition, neoplastic mast cells isolated from patients with mastocytosis, incubated with 17-AAG ex vivo, are selectively sensitive to the drug compared to the mononuclear fraction. These data provide compelling evidence that 17-AAG may be effective in the treatment of c-kit-related diseases including mastocytosis, GISTs, mast cell leukemia, subtypes of acute myelogenous leukemia, and testicular cancer.
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PMID:17-Allylamino-17-demethoxygeldanamycin (17-AAG) is effective in down-regulating mutated, constitutively activated KIT protein in human mast cells. 1455 Nov 38

Accumulating evidence indicates that expression of anaplastic lymphoma kinase (ALK), typically due to t(2;5) translocation that creates an NPM-ALK fusion gene, defines a distinct type of T/null-cell lymphoma (TCL) within a vastly heterogeneous group of anaplastic large cell lymphomas. Through the translocation mechanism or as a full-length apparently intact protein, ALK also is expressed by a subset of inflammatory myofibroblastic tumors, glioblastomas, diffuse large B-cell lymphomas, and other malignant neoplasms. Owing to the recent progress in understanding its pathogenesis, ALK+ TCL has become a model malignant neoplasm in which morphology-based diagnosis and classification are gradually shifting toward biology-based diagnosis. Several lines of experimental evidence indicate that the ectopically expressed ALK is oncogenic in ALK+ TCL by being constitutively active owing to autophosphorylation and, consequently, by stimulating several critical signal transduction pathways involving phospholipase C-gamma, AKT, and STAT3 (signal transducer and activator of transcription 3). Targeting ALK and, perhaps, its downstream signaling effector proteins represents a promising novel therapeutic approach to ALK+ TCL. Diagnostic implications of the ALK expression in ALK+ TCL and other malignant neoplasms and the related current controversies are discussed.
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PMID:Expression of anaplastic lymphoma kinase in non-Hodgkin's lymphomas and other malignant neoplasms. Biological, diagnostic, and clinical implications. 1456 15

Pancreatic ductal adenocarcinoma (PDAC) cell lines, MIA PaCa-2, and UK Pan-1, were used to investigate the role of ErbB2 in PDAC oncogenesis. Both these cell lines exhibit exogenous growth factor-independent proliferation that was attributed to the production of autocrine growth factors and/or overexpression of growth factor receptors. The exogenous growth factor-independent phenotype displayed by these PDAC cell lines was dependent on ErbB2 kinase activity since treatment of cells with tyrphostin AG879 prevented serum-free media (SFM) induction of cell proliferation. We determined that ErbB2 kinase contributed to aberrant cell cycle regulation in PDAC through the induction of cyclin D1 levels and the suppression of p21(Cip1) and p27(Kip1). Inhibition of ErbB2 kinase led to cell cycle arrest marked by an increased association of p27(Kip1) with cdk2 and reduced levels of phosphorylated pRb. We further observed constitutive STAT3 activation in the PDAC cell lines and an increase in STAT3 activation upon stimulating quiescent cells with SFM. Inhibitors of ErbB2 kinase blocked STAT3 activation, whereas inhibition of EGFR kinase led to a slight reduction of STAT3 activation. STAT3 was coimmunoprecipitated with ErbB2. SFM stimulation caused an increase in the association of ErbB2 and STAT3, which was blocked by inhibition of ErbB2 kinase. Expression of a STAT3 dominant negative prevented SFM-stimulated cell proliferation of MIA PaCa-2 cells, suggesting that activation of STAT3 by ErbB2 is required for a growth factor-independent phenotype of these cells. Consistent with this observation in PDAC cell lines, we found that most PDAC tumor specimens (10 of 11) showed constitutive activation of STAT3 and that ErbB2 was readily detected in most of these tumors (nine of 11). We believe that these findings indicate a novel mechanism of oncogenesis in PDAC and may suggest future therapeutic strategies in the treatment of PDAC.
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PMID:Autocrine-mediated ErbB-2 kinase activation of STAT3 is required for growth factor independence of pancreatic cancer cell lines. 1458 4

The production of interleukin-6 (IL-6) has been discovered in a variety of human tumors. Here we report the expression of IL-6, IL-6 receptor alpha (IL-6Ralpha), and gp130 in human esophageal carcinoma tissues. We further demonstrate that IL-6 protects an esophageal carcinoma cell line CE48T/VGH from apoptosis induced by staurosporine. IL-6 stimulation induced a rapid phosphorylation of gp130 and STAT3, and a dominant-negative STAT3 completely abolished the antiapoptotic effect. IL-6 also activated ERK 1/2 in CE48T/VGH cells. Inhibition of the ERK activation by PD98059 and transfection of a dominant-negative ERK2 completely blocked the protection of IL-6 against apoptosis. Thus, both STAT and MAP kinase pathways are responsible for the IL-6-delivered survival signal in human esophageal carcinoma cells. In contrast, PI3-K inhibitors only partially attenuated the effect of IL-6, suggesting that PI3-K does not play a major role in the antiapoptotic signal of IL-6 in our system. To investigate whether IL-6 could induce the production of antiapoptotic molecules, proteins of the Bcl-2 family were measured. While Bcl-2, Bcl-x(L,), and Bax were not affected, Mcl-1 was induced by IL-6 in human esophageal carcinoma cells. Our results suggest that IL-6 may contribute to the progression of esophageal cancers in an autocrine or paracrine manner.
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PMID:Interleukin-6 acts as an antiapoptotic factor in human esophageal carcinoma cells through the activation of both STAT3 and mitogen-activated protein kinase pathways. 1458 7


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