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)

AGS human gastric cancer cells were characterized to possess EGF receptors. Scatchard analysis revealed a half saturation constant of 0.6 nM and 9000 receptors per cell. Exogenously added EGF stimulated gastric cancer cell growth in a dose-dependent manner with a maximum effect of +38% at 10 nM EGF. Inhibition of the EGFR-associated tyrosine kinase by genistein and the tyrphostins RG-13022, RG-14620 and RG-50864 resulted in a dose-dependent growth inhibition with half maximal inhibition at 10 microM, 7 microM and 23 microM, respectively. EGF mediated growth stimulation was dose-dependently reversed by coincubation with genistein. At genistein concentrations exceeding 6 microM serum-stimulated growth of AGS cancer cells was also inhibited. We conclude that EGF is an important growth factor for AGS gastric cancer cells. Inhibition of the EGFR-associated tyrosine kinase seems to be an effective antiproliferative principle in EGFR-positive human gastric cancer cells.
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PMID:Antiproliferative effect of tyrosine kinase inhibitors in epidermal growth factor-stimulated growth of human gastric cancer cells. 829 23

Despite the induction of an immunological reaction, Helicobacter pylori-associated gastritis is a chronic disease, suggesting that this microbe can evade the host immune defense. Previous studies by our group showed that H. pylori suppresses the in vitro proliferative response of human mononuclear cells to mitogens and antigens. Here we demonstrate that the antiproliferative activity of H. pylori also affects the proliferation of various mammalian cell lines (U937, Jurkat, AGS, Kato-3, HEP-2, and P388D1). This effect is detectable in the first 16 h of incubation and maximal between 24 and 48 h. In addition, the presence of H. pylori significantly diminished the protein synthesis of cells in the first 6 h of incubation, comparable to the results with cycloheximide and diphtheria toxin. The urease enzyme, the cagA gene product, and the vacuolizing cytotoxin of H. pylori were excluded as causative agents of the antiproliferative effect by using isogenic knockout mutant strains. The inhibitory effect was not due to a lytic activity of this bacterium. The results reported here indicate that the responsible factor is a protein with an apparent native molecular mass of 100 +/- 10 kDa. Our work implicates the presence of a protein factor in H. pylori (termed PIP [for proliferation-inhibiting protein]) with antiproliferative activity for mammalian cells, including immunocompetent and epithelial cells. Thus, it is reasonable to presume that this property may contribute to the pathogenesis of H. pylori-induced diseases. It may be involved on the one hand in immune response evasion and on the other hand in the suppression of epithelial repair mechanisms.
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PMID:Partial characterization of a cell proliferation-inhibiting protein produced by Helicobacter pylori. 875 89

Gastrin stimulates transcription of the human histidine decarboxylase (HDC) gene through binding to the G-protein-coupled cholecystokinin-B/gastrin receptor. We have explored the possibility that mitogen-activated protein kinase cascades play a role in mediating the effects of gastrin on transcription in a gastric cancer (AGS-B) cell line. Gastrin and phorbol 12-myristate 13-acetate (PMA) treatment of AGS-B cells was found to increase the phosphorylation of tyrosine residues of extracellular signal-regulated kinases (ERKs) 1 and 2 and increase ERK activity as determined by the in vitro phosphorylation of myelin basic protein. Reporter gene assays also demonstrated that gastrin and PMA stimulated Elk-1- and c-Myc-dependent transactivation, consistent with gastrin- and PMA-induced activation of ERKs. Overexpression of wild type ERK-1 and ERK-2 or activation of endogenous ERKs using activated MEK-1 (mitogen-activated protein kinase kinase or ERK kinase) overexpression stimulated HDC promoter activity in a dose-dependent fashion. Interruption of the ERK-related pathway using expression vectors for kinase-deficient ERKs or an ERK-specific phosphatase (PAC-1) blocked gastrin- and PMA-stimulated HDC promoter activity. In contrast, inhibition of the Jun kinase pathway using an interfering dominant negative SEK-1 (stress-activated protein kinase/ERK-1) mutant did not inhibit HDC promoter activity. Furthermore, whereas gastrin stimulated phosphorylation of Shc proteins and association with Grb2, activation of the HDC promoter was not influenced by expression of dominant negative Ras (N15 or N17) proteins. However, gastrin stimulated Raf-1 kinase activity, and activation of the HDC promoter was blocked by coexpression of a dominant negative Raf-1 construct. Overall, these data demonstrate that gastrin regulates HDC transcription in a Rafdependent, Ras-independent fashion predominantly through activation of the ERK-related pathway.
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PMID:Gastrin and phorbol 12-myristate 13-acetate regulate the human histidine decarboxylase promoter through Raf-dependent activation of extracellular signal-regulated kinase-related signaling pathways in gastric cancer cells. 934 Nov 40

Epidermal growth factor (EGF) receptor activation stimulates gastrin gene expression through a GC-rich element called gastrin EGF response element (gERE). This element is bound by Sp1 family members and is a target of the ras-extracellular signal-regulated kinase (Erk) signal transduction cascade. This raised the possibility that Sp1 may be phosphorylated by kinases of this signaling pathway. Erk is capable of phosphorylating other mitogen-inducible transcription factors, e.g., Elk and Sap, suggesting that Erk may also mediate EGF-dependent phosphorylation of Sp1. This possibility was tested by studying Sp1-dependent kinase activity in extracts prepared from EGF-activated AGS cells by use of solid-phase kinase assays and immunoprecipitation of metabolically labeled Sp1. The results revealed that Sp1 kinase activity (like gastrin promoter activation) is inhibited by PD-98059 and, therefore, is dependent on mitogen-activated protein kinase kinase 1 (Mek 1). However, EGF-dependent activation of endogenous Erk did not account for most of the Sp1 kinase activity, since Erk and additional Sp1 kinase activity analyzed in a solid-phase kinase assay eluted from an ion-exchange column in different fractions. Phosphoamino acid analysis of in vivo radiolabeled Sp1 demonstrated that the kinase phosphorylates Sp1 on Ser and Thr in response to EGF. Therefore, most EGF-stimulated Sp1 kinase activity is Mek 1 dependent and distinct from Erk.
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PMID:EGF stimulates gastrin promoter through activation of Sp1 kinase activity. 1075 19

Differentiation-inducing factor-1 (DIF-1) is a chlorinated hexaphenone isolated from Dictyostelium. DIF-1 exhibits antitumor activity in several types of mammalian tumor cells, although the underlying mechanisms remain unknown. On the other hand, recent studies indicate that constitutively activated STAT3 acts as an oncogene and could be a target for antitumor drug. In the present study, we examined the effects of DIF-1 on proliferation of gastric cancer cell lines as well as on its signal transduction pathways, focusing mainly on STAT proteins. DIF-1 inhibited proliferation of gastric cancer cells. Western blot analysis and electrophoretic mobility shift assay showed that DIF-1 inhibited STAT3 activity in an MEK-ERK-dependent manner in gastric cancer cell lines, AGS and MKN28. Moreover, blockade of STAT3 activity by ectopic expression of dominant-negative STAT3 or the Janus kinase inhibitor, tyrphostin AG490, inhibited cell growth of AGS cells. These results suggest that STAT3 activity plays an important role for cell growth in AGS cells, and raises the possibility that inhibition of STAT3 activity is one of the mechanisms responsible for the antitumor effect of DIF-1 in these cells.
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PMID:Differentiation-inducing factor-1 (DIF-1) inhibits STAT3 activity involved in gastric cancer cell proliferation via MEK-ERK-dependent pathway. 1255 68

The erythropoietin-producing hepatocellular (EPH)A2 receptor, tyrosine kinase, is overexpressed and phosphorylated in several types of human tumors and has been associated with malignant transformation. A recent report, however, indicated that stimulation of the EPHA2 receptor ligand, ephrinA1 (EFNA1), inhibits the growth of EPHA2-expressing breast cancer. The authors examined the expression of EPHA2 and EFNA1 using semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) in four gastric cancer cell lines and 49 primary gastric cancer samples, as well as in normal gastric tissue. EPHA2 was more highly expressed in tumor tissue than in normal tissue in 27 cases (55%). EFNA1 was overexpressed in tumor tissue in 28 cases (57%). No significant correlation was detected between the expression levels and histologic features such as tumor size, age, vessel invasion, or lymph node involvement. However, EPHA2 overexpression was more prominent in macroscopic type 3 and 4 tumors than in type 1 or 2 advanced gastric cancer. The authors observed EPHA2 expression in three of the four gastric cancer cell lines (AGS, KATO3, and MKN74) that were examined. In one cell line, TMK1, EPHA2 expression was barely detectable using northern blotting, RT-PCR, and western blotting. In contrast, EFNA1 was detected in all cell lines. In the gastric cancer cell lines that endogenously expressed EPHA2, stimulation with ephrinA1-Fc led to decreased EPHA2 protein expression and increased EPHA2 phosphorylation. Finally, the growth of EPHA2-expressing cells was inhibited by repetitive stimulation with soluble ephrinA1-Fc. Taken together, these findings suggest that EPHA2 and EFNA1 expression may influence the behavior of human gastric cancer.
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PMID:EPHA2/EFNA1 expression in human gastric cancer. 1564 54

Anthocyanins are naturally occurring reddish pigments that abundant in fruits and vegetables. To investigate the mechanistic basis for the anti-tumor properties of anthocyanins, five aglycone (cyanidin, delphinidin, malvidin, pelargonidin, and peonidin) and four glycosylated (cyanidin-3-glucoside, malvidin-3-glucoside, pelargonidin-3-glucoside and peonidin-3-glucoside) anthocyanins were used to examine their effects on cell cycle progression and induction of apoptosis in human gastric adenocarcinoma AGS cells. The data from cell viability assay showed that malvidin exhibited the most potent anti-proliferation effect on AGS cells in a time- and dose-dependent manner (P<0.05). This event is accompanied the arrest of AGS cells at the G0/G1 phase by malvidin at the tested concentrations of 0-200 microM. Cellular uptake of anthocyanin and anthocyanidin was confirmed by HPLC analysis and the intracellular accumulation of malvidin (24.9+/-1.1 microM/mg protein) was observed when treatment of AGS cells with malvidin for 12 h. In addition, an accumulation of AGS cells in sub-G1 phase (20% and 30% increase for 100 and 200 microM of malvidin, respectively) was observed as well as by the appearance of a fraction of cells with an aneudiploid DNA content. The occurrence of apoptosis induced by malvidin was confirmed by morphological and biochemical features, including apoptotic bodies formation, caspase-3 activation and poly(ADP-ribose) polymerase proteolysis. Furthermore, the mitochondrial membrane potential of apoptotic cells after treatment with malvidin was significantly lost and resulted in the elevation of Bax/Bcl-2 ratio for 1.6-fold against control for 100 microM treatment. In addition, the malvidin treatment significantly increased the p38 kinase expression and inhibited the ERK activity, and the effects of malvidin on caspase-3 activation were blocked, respectively, by the ERK and p38 inhibitors. These findings suggest that growth inhibition and cytotoxicity of AGS cells by malvidin is involved in the induction of apoptosis rather than necrosis.
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PMID:Effects of anthocyanidin on the inhibition of proliferation and induction of apoptosis in human gastric adenocarcinoma cells. 1596 18

Bile acids, which have been implicated in gastrointestinal-tract cell carcinogenesis, share properties with tumor promoters in that both affect signal transduction pathways responsible for cell proliferation and apoptosis. In the present study, we demonstrate that EGFR-ERK1/2 is activated following treatment of AGS human gastric carcinoma cells with bile acids. EGFR phosphoactivation is ligand-dependent, since treatment of cells with HB-EGF antisera or CM197 (a selective inhibitor of HB-EGF) markedly inhibits deoxycholate (DC)-promoted activation. Membrane-type bile acid receptor (M-BAR)/TGR5 is a recently identified G-protein-coupled receptor (GPCR). In AGS cells, siRNAs that target M-BAR suppress DC-induced phosphorylation of EGFR. Furthermore, introduction of siRNAs targeting ADAM17 transcripts resulted in suppression of DC-induced activation of EGFR and ERK1/2. These results suggest that in AGS cells, DC transactivates EGFR through M-BAR- and ADAM/HB-EGF-dependent mechanisms.
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PMID:Involvement of membrane-type bile acid receptor M-BAR/TGR5 in bile acid-induced activation of epidermal growth factor receptor and mitogen-activated protein kinases in gastric carcinoma cells. 1721 62

Because the mechanisms of Helicobacter pylori-induced gastric injury are incompletely understood, we examined the hypothesis that H. pylori induces matrix metalloproteinase-1 (MMP-1) secretion, with potential to disrupt gastric stroma. We further tested the role of CagA, an H. pylori virulence factor, in MMP-1 secretion. Co-incubation of AGS cells with Tx30a, an H. pylori strain lacking the cagA virulence gene, stimulated MMP-1 secretion, confirming cagA-independent secretion. Co-incubation with strain 147C (cagA(+)) resulted in CagA translocation into AGS cells and increased MMP-1 secretion relative to Tx30a. Transfection of cells with the recombinant 147C cagA gene also induced MMP-1 secretion, indicating that CagA can independently stimulate MMP-1 secretion. Co-incubation with strain 147A, containing a cagA gene that lacks an EPIYA tyrosine phosphorylation motif, as well as transfection with 147A cagA, yielded an MMP-1 secretion intermediate between no treatment and 147C, indicating that CagA tyrosine phosphorylation regulates cellular signaling in this model system. H. pylori induced activation of the MAP kinase ERK, with CagA-independent (early) and dependent (later) components. MEK inhibitors UO126 and PD98059 inhibited both CagA-independent and -dependent MMP-1 secretion, whereas p38 inhibition enhanced MMP-1 secretion and ERK activation, suggesting p38 negative regulation of MMP-1 and ERK. These data indicate H. pylori effects on host epithelial MMP-1 expression via ERK, with p38 playing a potential regulatory role.
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PMID:Helicobacter pylori stimulates gastric epithelial cell MMP-1 secretion via CagA-dependent and -independent ERK activation. 1747 25

12-Lipoxygenase (12-LOX) is over-expressed in a variety of human tumors, but its exact effect on the tumorogenesis of gastric cancer remains largely obscure. To investigate the effect of 12-LOX and its inhibitor baicalein on proliferation and apoptosis of human gastric cancer, AGS cells were separately treated with 12-hydroxyeicosatetraenoic acid (12-HETE, a metabolite of 12-LOX) and baicalein. MTT assay revealed that the absorbance of the 12-HETE-treated group was significantly (P < 0.01) higher than that of control group and that the absorbance of baicalein-treated group was significantly (P < 0.01) less than that of the control group, and that 48 h after treatment the apoptosis index of the baicalein-treated group was significantly (P < 0.01) higher than that of the untreated group and was significantly (P < 0.01) lower in the 12-HETE-treated group. Western blotting analysis was used to investigate the mechanism of these effects. The results revealed that the concentration of phosphorylated ERK in cells treated with 100 nmol L(-1) 12-HETE was significantly (P < 0.05) higher than in the untreated group and that the concentration of phosphorylated ERK1/2 in cells treated with 40 micromol L(-1) baicalein was significantly (P < 0.05) lower than in the untreated group. The expression level of bcl-2 was up-regulated and down-regulated after separate treatment with 12-HETE and baicalein, respectively, and both of these effects could be blocked by PD98059. Protein kinase C (PKC) activity was increased by treatment with 12-HETE and reduced by treatment with baicalein (P < 0.05). The PKC inhibitor BIM (bisindolymaleimide-I) blocked the phosphorylation of ERK1/2 and activation of PKC induced by 12-LOX. When pretreated with BIM, the concentration of phospho-ERK1/2 or bcl-2 in the BIM + 12-HETE-treated group was significantly (P < 0.05) lower than in that treated with 12-HETE only, and the concentration in the BIM + baicalein-treated group was significantly (P < 0.05) higher than in that treated with baicalein only. On the basis of these data we conclude that, via its metabolite 12-HETE, 12-LOX abolishes proliferation of AGS cells and protect cells from apoptosis by activating the ERK1/2 pathway and, eventually, enhances expression of bcl-2. Because PKC is also involved in the activation of ERK1/2 induced by 12-LOX, 12-LOX inhibitors would be potentially powerful anticancer agents for prevention and cure of human gastric cancer.
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PMID:12-lipoxygenase induces apoptosis of human gastric cancer AGS cells via the ERK1/2 signal pathway. 1752 76


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