u-0126 and Stomach-Neoplasms

BACKGROUND Ginkgo biloba extract (EGb761), a standard extract of the Chinese traditional medicine Ginkgo biloba, plays an anti-tumor role in various cancers. However, whether EGb761 is involved in the invasion and metastasis of gastric cancer remains unclear. MATERIAL AND METHODS In the current study, cell viability assay, Western blotting, wound-healing assay, Transwell invasion assay, and orthotopic transplantation model were performed to explore the effects of EGb761 on gastric cancer. RESULTS In vitro, the results showed that EGb761 suppressed the proliferation of gastric cancer cells in a dose-dependent manner. Furthermore, the migration and invasiveness were weakened and the protein levels of p-ERK1/2, NF-kappaB P65, NF-kappaB p-P65, and MMP2 were decreased by EGb761 or U0126 (an inhibitor of ERK signaling pathway) exposure in gastric cancer cells. Moreover, the combined treatment with EGb761 and U0126 significantly inhibited ERK, NF-kappaB signaling pathway, and the expression of MMP2 than those of single drug. In vivo, EGb761 inhibited the tumor growth and hepatic metastasis of gastric cancer in the mouse model. Results of immunohistochemistry indicated that the expression of ERK1/2, NF-kappaB P65 and MMP2 were decreased by EGb761 in the tumor tissues. CONCLUSIONS EGb761 plays a vital role in the suppression of metastasis and ERK/NF-kappaB signaling pathway in gastric cancer.

Topics: Animals; Butadienes; Cell Line, Tumor; Cell Movement; Cell Proliferation; Extracellular Signal-Regulated MAP Kinases; Ginkgo biloba; Humans; MAP Kinase Signaling System; Matrix Metalloproteinase 2; Mice, Nude; Neoplasm Invasiveness; Neoplasm Metastasis; NF-kappa B; Nitriles; Phosphorylation; Plant Extracts; Signal Transduction; Stomach Neoplasms

Topics: Aged; Anthracenes; Apoptosis; Bortezomib; Butadienes; Caspases; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Drug Synergism; Female; Gene Expression Regulation, Neoplastic; Humans; Male; MAP Kinase Kinase 4; MAP Kinase Signaling System; Middle Aged; Nitriles; p21-Activated Kinases; Receptors, TNF-Related Apoptosis-Inducing Ligand; Stomach Neoplasms; TNF-Related Apoptosis-Inducing Ligand

Solamargine, a derivative from the steroidal solasodine in Solanum species, has exhibited anticancer activities in numerous types of cancer; however, its role in gastric cancer (GC) remains unknown. In the present study, it was demonstrated that Solamargine suppressed the viability of five gastric cancer cell lines in a dose‑dependent manner and induced notable alterations in morphology. Treatment with Solamargine promoted cell apoptosis (P<0.01). Solamargine increased the expression of long noncoding RNA (lnc) p53 induced transcript and lnc nuclear paraspeckle assembly transcript 1 (NEAT1)_2 (P<0.01) in GC by reducing the phosphorylation of extracellular signal‑regulated kinase (Erk)1/2 mitogen‑activated protein kinase (MAPK). To gain insight into the potential mechanism, an Erk1/2 inhibitor (U0126) was applied. The results revealed that lncNEAT1_2 expression levels increased, which was consistent with the effects of Solamargine. Downregulation of lncNEAT1_2 in GC cells revealed no effect on the expression levels of total Erk1/2 and, and counteracted the effect of Solamargine. Solamargine was observed to increase the expression of lncNEAT1_2 via the Erk1/2 MAPK signaling pathway. Of note, the knockdown of lncNEAT1_2 reduced the inhibitory effect of Solamargine (P<0.05). Additionally, experiments in vivo and in primary GC cells from patients demonstrated that Solamargine significantly suppressed tumor growth (P<0.05). In vivo analysis of a xenograft mouse model further supported that Solamargine could induce the apoptosis of cancer cells in tumor tissue as observed by a terminal deoxynucleotidyl transferase‑mediated dUTP‑biotin nick end labeling and H&E staining (P<0.05). Experiments in primary GC cells from patients verified the anti‑tumor effect of Solamargine. In summary, the findings of the present study indicated that Solamargine inhibited the progression of GC by regulating lncNeat1_2 via the MAPK pathway.

Topics: Animals; Butadienes; Cell Line, Tumor; Cell Proliferation; Cell Survival; Gene Expression Regulation, Neoplastic; Humans; MAP Kinase Signaling System; Mice; Nitriles; RNA, Long Noncoding; Solanaceous Alkaloids; Stomach Neoplasms; Up-Regulation; Xenograft Model Antitumor Assays

Cancer‑associated fibroblasts (CAFs) are predominate cells in tumor stroma and play a key role in tumor progression. Hepatocyte growth factor (HGF) is a cytokine mainly derived from fibroblasts. In the present study, we reported that HGF significantly promoted angiogenesis of human umbilical vein endothelial cells (HUVECs) and vasculogenic mimicry (VM) formation of gastric cancer cells, respectively, by increasing cell proliferation and migration. In addition, mosaic vessels formed by HUVECs and gastric cancer cells were also increased with treatment of recombinant human HGF and conditioned medium from CAFs. The opposite results were achieved in HGF‑neutralized groups. In accordance with these observations, we determined that phosphorylation of AKT and ERK1/2 were upregulated in HUVECs and gastric cancer cells with HGF treatment and co‑culture with CAFs. Both AKT inhibitor LY294002 and ERK1/2 inhibitor U0126 reduced the ability of angiogenesis and VM formation, as well as mosaic vessel formation induced by HGF. Gene Set Enrichment Analysis and correlation analysis were performed to confirm our findings. In conclusion, CAF‑derived HGF promotes angiogenesis, VM and mosaic vessel formation via PI3K/AKT and ERK1/2 signaling in gastric cancer and HGF may serve as a potential therapeutic target for cancer anti‑vascular treatment.

Topics: Butadienes; Cancer-Associated Fibroblasts; Cell Line; Cell Line, Tumor; Cell Movement; Cell Proliferation; Chromones; Hepatocyte Growth Factor; Human Umbilical Vein Endothelial Cells; Humans; MAP Kinase Signaling System; Morpholines; Neovascularization, Pathologic; Nitriles; Phosphatidylinositol 3-Kinases; Phosphorylation; Proto-Oncogene Proteins c-akt; Signal Transduction; Stomach Neoplasms; Up-Regulation

Gastric cancer cell are not particularly sensitive to Ara-C, a deoxycytidine analog that affects DNA synthesis. In the present study, AGS and MKN-45 gastric cancer cell lines were treated with Ara-C to determine its role in cell prolife-ration and apoptosis. The antiproliferative effect of Ara-C was assessed using the Cell Counting kit-8. Gelatinase zymography was utilized to detect the activity of MMP-2 and MMP-9, and an in vitro invasion assay was performed. Using RT-PCR, CD-147, MMP-2 and MPP-9 mRNA levels were assessed in AGS cells with various doses of Ara-C treatment. CD-147, MMP-2 and MMP-9 protein levels were analysed in Ara-C‑treated AGS and MKN-45 cells. AGS cells were treated with or without U-0126 or siRNA-CD147 and/or Ara-C for 24 h, and an in vitro invasion assay was performed. Although low-dose Ara-C had no obvious effect on cell proliferation, it upregulated the expression of MMP-2, MMP-9 and CD-147 and ERK activation. Low-dose Ara-C increased gastric cancer cell invasion. U-0126 and siRNA-CD-147 inhibited the induction of Ara-C in gastric cancer cell invasion. Therefore, Ara-C enhances the invasiveness of gastric cancer cells by expression of CD-147 /MMP-2 and MMP-9 via the ERK signaling pathway. The results are therefore useful in the prevention of Ara-C collateral damage associated with standard, conventional protocols of chemotherapy administration.

Topics: Basigin; Butadienes; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cytarabine; Gene Expression Regulation, Neoplastic; Humans; Jurkat Cells; MAP Kinase Signaling System; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Neoplasm Invasiveness; Nitriles; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Stomach Neoplasms; Up-Regulation

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), which has long been believed to be highly selective in inducing apoptosis in cancer cells, has turned out to be a molecule that induces a far more diverse range of effects. The aim of this study was to investigate whether or not ERK1/2 pathway is involved in antitumor effects of TRAIL on gastric cancer cells. In addition to activate the extrinsic and intrinsic apoptotic pathway, TRAIL also triggered the activation of ERK1/2. Inhibition of ERK1/2 signaling by MEK inhibitor U0126 promoted cell death via increased activation of caspases, drop in mitochondrial membrane potential and downregulation of XIAP, cIAP2 and Mcl-1. These results indicate that TRAIL-induced rapid activation of ERK1/2 may be a survival mechanism to struggle against TRAIL assault at the early stage, and inhibition of ERK1/2 signaling can sensitize gastric cancer cells to TRAIL-induced apoptosis.

Topics: Apoptosis; Apoptosis Regulatory Proteins; Baculoviral IAP Repeat-Containing 3 Protein; Butadienes; Cell Line, Tumor; Down-Regulation; Gene Expression Regulation, Neoplastic; Humans; Inhibitor of Apoptosis Proteins; MAP Kinase Kinase Kinases; MAP Kinase Signaling System; Myeloid Cell Leukemia Sequence 1 Protein; Nitriles; Stomach Neoplasms; TNF-Related Apoptosis-Inducing Ligand; Ubiquitin-Protein Ligases; X-Linked Inhibitor of Apoptosis Protein

Growth and inflammatory factors are associated with poor prognosis in gastric adenocarcinoma (GA); however, the additive effects of growth and inflammatory factors in GA remain unclear. In this study, we investigated the ability of epidermal growth factor (EGF) and interleukin (IL-1β) to activate extracellular signal-regulated kinase (ERK)1/2 in GA cells, and correlated the relationships between their roles with the metastatic potential both in GA cells and GA tissues. The effects of EGF, IL-1β and EGF plus IL-1β in AGS and MKN-45 GA cells were examined using western blotting, Transwell migration and invasion assays, immunocytochemical staining and an activator protein (AP)-1 luciferase reporter gene assay, and was further characterized in GA tissues by immunohistochemistry. The results exhibited that EGF and IL-1β additively activated ERK1/2, increased migration and invasion than either EGF or IL-1β alone in AGS and MKN-45 cells. The mechanisms were involved in upregulating MMP-9 expression through increasing AP-1 transcriptional activity via ERK1/2 pathway; these effects were dose-dependently inhibited by silencing ERK1/2 or using U0126. In vivo data also confirmed that the overexpression of p-ERK1/2 in GA tissues correlated well with the EGF, IL-1β, EGF plus IL-1β, and was associated with metastasis, which was well correlation with the expression of MMP-9 and c-fos (AP-1). The results demonstrate that growth and inflammatory factors play an important role in metastasis of GA by additively activating ERK-1/2 and AP-1, and upregulating MMP-9. As both cytokines contribute to the migration and invasion of GA cells, EGF/IL-1β/ERK1/2 pathways may be key pathways closely associated with GA progression.

Topics: Adenocarcinoma; Butadienes; Cell Line, Tumor; Cell Movement; Enzyme Inhibitors; Epidermal Growth Factor; Female; Humans; Interleukin-1beta; Male; MAP Kinase Signaling System; Matrix Metalloproteinase 9; Middle Aged; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Neoplasm Invasiveness; Nitriles; Phosphorylation; Stomach Neoplasms; Transcription Factor AP-1

Thymosin beta-4 (Tβ4), actin-sequestering protein, plays important roles in many cellular functions including cancer cell migrations. Glycogen synthase kinase (GSK) in Wnt signaling pathway is a key molecule to control intercellular interaction. Here, we investigated whether GSK-3 activity is regulated by Tβ4 and it is associated with Tβ4-mediated migration in gastric cancer cells. Various expression level of Tβ4 was observed in human gastric tumor tissues. Migration in gastric cancer cells, SNU638 and SNU668, was dependent on a relative expression level of Tβ4. Cell migration was higher in SNU668 with a higher expression level of Tβ4 than that in SNU638 with a lower Tβ4. Although the level of phosphorylated(p)-GSK-3α (inactive), β-catenin, E-cadherin and E-cadherin:β-catenin complex was relatively higher, p-GSK-3β (inactive) was lower in SNU638 compared to those in SNU668 cells. LiCl, GSK-3α/β inhibitor, reduced lung metastasis of B16F10 mouse melanoma cells and SNU668 cell migration. Small interference (si)RNA of GSK-3α increased SNU638 cell migration in accordance with the reduction of E-cadherin:β-catenin complex formation through a decrease in β-catenin and E-cadherin. Expression level of GSK-3α/β, β-catenin and E-cadherin in SNU668 and SNU638 was reversed by Tβ4-siRNA and by the treatment with acetylated-serine-aspartic acid-lysine-proline (SDKP) tetrapeptide of Tβ4, respectively. E-cadherin expression in SNU638 cells was decreased by β-catenin-siRNA. PD98059, MEK inhibitor, or U0126, ERK inhibitor, reduced SNU668 cell migration accompanying an increase in p-GSK-3α, β-catenin and E-cadherin. Taken together, data indicated that the expression of GSK-3α, β-catenin and E-cadherin could be negatively regulated by Tβ4-induced ERK phosphorylation. It suggests that Tβ4 could be a novel regulator to control Wnt signaling pathways.

Topics: Animals; beta Catenin; Butadienes; Cadherins; Calcium-Calmodulin-Dependent Protein Kinases; Cell Line, Tumor; Cell Movement; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Female; Flavonoids; Glycogen Synthase Kinase 3; Humans; Lithium Chloride; Lung Neoplasms; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Nitriles; Peptides; Phosphorylation; RNA Interference; RNA, Small Interfering; Stomach Neoplasms; Thymosin; Wnt Signaling Pathway

Ursodeoxycholic acid (UDCA) has been regarded as a suppressor of gastrointestinal cancer, but the mechanisms underlying its antitumor effects are not fully understood. Previously, we reported the antitumor effect of UDCA by demonstrating that UDCA induces apoptosis of gastric cancer cells. Bile acids are known to activate the ERK pathway and ERK is a representative oncogenic kinase in cancer cells. Here, we investigated the role of ERK in UDCA-induced gastric cancer cell apoptosis. We found that UDCA enhanced the phosphorylation of ERK1/2 and MEK1/2. The prevention of MEK by the pharmacologic inhibitors PD98059 and U0126, resulted in decreased UDCA-induced apoptosis as shown by the reduction of apoptotic body formation, caspase-8 activity, and caspase-3, -6 and PARP cleavage, indicating that ERK exerts pro-apoptotic activity upon exposure to UDCA. In addition, U0126 reduced UDCA-triggered TNF-related apoptosis-inducing ligand receptor 2 (TRAIL-R2/DR5) expression. In gene silencing studies, we observed that RNA interference of ERK2 decreased apoptosis and reduced DR5 overexpression. Lipid raft disrupting agent, methyl-β-cyclodextrin, blunted the phosphorylation of ERK1/2, indicating that ERK activation is regulated in a lipid raft-dependent manner. On the other hand, tumor-promoting bile acid, deoxycholic acid (DCA), also phosphorylated ERK in SNU601 cells. However, the DCA-triggered ERK pathway exerted anti-apoptotic function in the cells. Suppression of the ERK pathway enhanced DCA-induced apoptosis, and ERK activation was observed to be lipid raft-independently controlled. These results indicated that UDCA and DCA may cause differential responses in gastric cancer cells through the ERK signaling molecule. Thus, ERK activation may be a possible mechanism by which UDCA and DCA represent differential activities in gastrointestinal cancer.

Topics: Apoptosis; Butadienes; Caspases; Cell Line, Tumor; Enzyme Activation; Flavonoids; Humans; MAP Kinase Kinase 1; MAP Kinase Kinase 2; MAP Kinase Signaling System; Membrane Microdomains; Nitriles; Phosphorylation; Protein Kinase Inhibitors; Receptors, TNF-Related Apoptosis-Inducing Ligand; Stomach Neoplasms; Ursodeoxycholic Acid

For gastric cancers, the antineoplastic activity of cannabinoids has been investigated in only a few reports and knowledge regarding the mechanisms involved is limited. We have reported previously that treatment of gastric cancer cells with a cannabinoid agonist significantly decreased cell proliferation and induced apoptosis. Here, we evaluated the effects of cannabinoids on various cellular mediators involved in cell cycle arrest in gastric cancer cells. AGS and MKN-1 cell lines were used as human gastric cancer cells and WIN 55,212-2 as a cannabinoid agonist. Cell cycles were analyzed by flow cytometry and western blotting. Treatment with WIN 55,212-2 arrested the cell cycle in the G0/G1 phase. WIN 55,212-2 also upregulated phospho-ERK1/2, induced Kip1/p27 and Cip1/WAF1/p21 expression, decreased cyclin D1 and cyclin E expression, decreased Cdk 2, Cdk 4, and Cdk 6 expression levels, and decreased phospho-Rb and E2F-1 expression. ERK inhibitor decreased the proportion of G0/G1 phase which was induced by WIN 55,212-2. Inhibition of pAKT led to cell cycle arrest in gastric cancer cells. Cell cycle arrest preceded apoptotic response. Thus, this cannabinoid agonist can reduce gastric cancer cell proliferation via G1 phase cell cycle arrest, which is mediated via activation of the MAPK pathway and inhibition of pAKT.

Topics: Apoptosis; Benzoxazines; Blotting, Western; Butadienes; Calcium Channel Blockers; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Cyclin-Dependent Kinases; Cyclins; Dose-Response Relationship, Drug; E2F1 Transcription Factor; Enzyme Inhibitors; Flow Cytometry; G1 Phase; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Morpholines; Naphthalenes; Nitriles; Phosphorylation; Proto-Oncogene Proteins c-akt; Resting Phase, Cell Cycle; Retinoblastoma Protein; Stomach Neoplasms

Helicobacter pylori-cytotoxin-associated protein A (CagA) and gastrin are believed to play an important role in gastric carcinogenesis, but their interaction has been incompletely clear.. We constructed a eukaryotic expression vector pcDNA3.1/cagA and a luciferase reporter vector pGL/gastrin promoter, and then co-transfected them into gastric cancer AGS and SGC-7901 cells. The two kinds of gastric cancer cells were, respectively, infected with cagA-positive H. pylori NCTC11637, and then the gastrin promoter activity and gastrin mRNA level were detected with a Dual-Luciferase reporter assay system and quantitative reverse transcription polymerase chain reaction (RT-PCR), respectively. Next, after the MEK/ERK and JAK2-signaling pathway inhibitors, U0126 and AG490, were used to treat the two cell lines, or the ERK1 and JAK2 genes were knocked down by siRNAs (small interference RNAs) in the two cell lines, the gastrin promoter activity and gastrin mRNA level were observed again.. The results indicated that CagA could activate the gastrin promoter and up-regulate gastrin mRNA expression in AGS and SGC-7901 cells, but these effects could be inhibited by the inhibitors U0126 and AG490, and the CagA-induced gastrin mRNA expression was down-regulated in the cells whose ERK1 or JAK2 gene was knocked down.. Gastrin promoter may be the transcriptional target of CagA, and CagA activates the gastrin promoter to up-regulate gastrin mRNA expression through the MEK/ERK and JAK1-signaling pathway in gastric cancer cells.

Topics: Antigens, Bacterial; Bacterial Proteins; Binding Sites; Butadienes; Enzyme Inhibitors; Gastrins; Gene Expression Regulation, Neoplastic; Helicobacter pylori; Humans; Janus Kinase 2; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 3; Nitriles; Promoter Regions, Genetic; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Stomach Neoplasms; Tumor Cells, Cultured; Tyrphostins; Up-Regulation

Integrins play an important role in tumor metastasis induced by vascular endothelial growth factor (VEGF). However, in the case of gastric cancer, the precise role of VEGF in regulating integrin alphavbeta6 is unclear. In this study, we found that most of the alphavbeta6 integrin-positive gastric cancer tissues were also VEGF-positive. Furthermore, when gastric carcinoma cells were exposed to VEGF, expression of alphavbeta6 integrin was up-regulated and the extracellular signal-related kinase (ERK) pathway was activated. When integrin alphavbeta6 was blocked either with beta6 siRNA or anti-alphavbeta6 antibody, the migration of tumor cells normally induced by VEGF, as well as the activation of ERK, were markedly inhibited. Blocking the ERK signaling pathway significantly inhibited cell mobility. Taken together, the data suggest that VEGF is critical to the invasive process in human gastric cancer and that this occurs via up-regulation of integrin alphavbeta6 expression and activation of ERK.

Topics: Antibodies; Antigens, Neoplasm; Butadienes; Carcinoma; Cell Line, Tumor; Cell Movement; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; Humans; Integrins; Matrix Metalloproteinase 9; Neoplasm Invasiveness; Nitriles; Protein Kinase Inhibitors; Recombinant Proteins; RNA Interference; RNA, Messenger; Stomach Neoplasms; Transfection; Vascular Endothelial Growth Factor A

We previously demonstrated that hypoxia increased the hypoxia-inducible factor (HIF-1)-dependent MGr1-Ag/37LRP expression, which enhanced adhesion of gastric cancer cells to laminin, inhibited drug-induced apoptosis and caused cell adhesion-mediated drug resistance (CAM-DR). Here, we investigated the role of extracellular-regulated kinase (ERK) 1/2 in the signaling mechanisms underlying these events. We found that hypoxia activated ERK activity in vitro and in vivo. Overexpression of mitogen-activated protein kinase (MAPK) kinase (MEK), which preferentially activated ERK, mimics, in a nonadditive way, hypoxia-induced activity of MGr1-Ag/37LRP promoter and expression of MGr1-Ag/37LRP. Furthermore, U0126, the MEK inhibitor, inhibited hypoxia- and MEK-induced MGr1-Ag/37LRP promoter activity in a dose-dependent manner. MEK inhibition also reversed hypoxia- and MEK-induced HIF-1 protein and its activity in a dose-dependent manner. We also investigated reactive oxygen species signaling this response. Exogenous addition of H(2)O(2) was sufficient to activate ERK in a dose-dependent profile. Reactive oxygen species scavengers of H(2)O(2) significantly inhibited hypoxia-induced ERK or HIF-1 activation and sequential expression of MGr1-Ag/37LRP. We also investigated the signaling in hypoxia-induced cell adhesion and apoptosis induced by vincristine. Hypoxia significantly enhanced adhesion of SGC7901 cells to laminin in a time-dependent manner, which might be inhibited by the MEK inhibitor U0126 and MGr1-Ag/37LRP siRNA. Consistent with results of adhesion assay, hypoxia-resistant apoptosis might be reversed by U0126 in a dose-dependent manner. Our results suggest that hypoxia-elicited MGr1-Ag/37LRP expression activated by HIF-1 depends on ERK activation. These events are dependent of reactive oxygen intermediates.

Topics: Animals; Antigens, Neoplasm; Apoptosis; Blotting, Western; Butadienes; Cell Adhesion; Cell Movement; Dose-Response Relationship, Drug; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Humans; Hydrogen Peroxide; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Mice; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Oxidants; Phosphorylation; Promoter Regions, Genetic; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Stomach Neoplasms; Tumor Cells, Cultured

To study the regulatory effect of Helicobacter pylori CagA protein on gastrin promoter and the related signaling pathways as to further elucidate the mechanism of the development and progression of human gastric carcinoma.. After pcDNA3.1ZEO(-)/CagAand PGL/GP were identified by double restriction enzyme digestion, PCR and sequencing, the gastric cancer cell lines AGS and SGC-7901 cells were co-transfected with pcDNA3.1ZEO(-)/CagA and PGL/GP for 48 h. Alternatively, AGS and SGC-7901 cells were transfected by PGL/GP for 36 h later, and infected with Helicobacter pylori for additional 12 h. Meanwhile, the transfected and infected cells were treated using the JAK2 signaling pathway inhibitor AG490 and the ERK signaling pathway inhibitor U0126. The untreated cells and empty-vector-transfected cells were used as the control. Finally, luciferase activity was detected using the luciferase reporter assay system in transfected and infected cells. The levels of gastrin mRNA was determined by TaqMan® real-time quantitative PCR.. After co-transfection with pcDNA3.1ZEO(-)/CagA and PGL/GP, the activities of luciferase were increased by 251.3, 106.1 and 2.4 times in AGS cells and 35.8, 22.7 and 13.4 times in SGC-7901 cells, respectively, as compared with that of the control, pcDNA3.1 ZEO(-)/CagA + PGL3/Basic and pcDNA3.1 ZEO(-) + PGL/GP groups. The activities of luciferase in PGL/GP transfection and HP infection group were also increased by 1673.2, 33.5, 1.4 times in AGS cells and 1180.2, 72.2 and 1.5 times in SGC-7901 cells, respectively, as compared with that of the control, PGL3/Basic + HP and PGL/GP groups. There were statistically significant differences between them (P < 0.05), which suggested that the transcription activity of gastrin promoter increased significantly. But after adding the inhibitor AG490 and U0126, respectively, the activities of luciferase were significantly decreased by 95.7% (U0126) and 33.0% (AG490) in co-transfected AGS cells and 94.8% (U0126) and 86.2% (AG490) in co-transfected SGC-7901 cells with pcDNA3.1ZEO(-)/CagA and PGL/GP (P < 0.05). In the PGL/GP transfection and HP infection group, the activities of luciferase were significantly decreased by 24.6% (U0126) and 25.8% (AG490) in AGS cells and 57.3% (U0126) and 14.1% (AG490) after adding the inhibitor AG490 and U0126, respectively (P < 0.05). The results showed that the gastrin promoter activities were significantly inhibited. The gastrin mRNA levels were 3.0 and 4.5 times higher in HP-infected AGS and SGC-7901 cells, respectively, than that in the control groups. In the cells transfected with pcDNA3.1ZEO(-)/CagA, the gastrin mRNA levels were raised 10.8 and 2.3 times (AGS cells) and 10.9 and 16.2 times (SGC-7901 cells), respectively, as compared with that of control and pcDNA3.1ZEO(-) groups. All of the differences were statistically significant (P < 0.05).. These results suggest that CagA may activate the gastrin promoter and up-regulate the expression of gastrin gene, and CagA is one of the important proteins in regulating gastrin gene expression. The ERK/MAPK and JAK/STAT signaling pathways may be involved in the controlling of gastrin gene expression by CagA.

Topics: Antigens, Bacterial; Antineoplastic Agents; Bacterial Proteins; Butadienes; Cell Line, Tumor; Enzyme Inhibitors; Gastrins; Gene Expression Regulation, Neoplastic; Genetic Vectors; Helicobacter Infections; Helicobacter pylori; Humans; Nitriles; Promoter Regions, Genetic; RNA, Messenger; Stomach Neoplasms; Transfection; Tyrphostins; Up-Regulation

Breast cancer resistance protein (BCRP)/ABCG2 is a drug efflux pump responsible for multidrug resistance in cancer cells. We report that dephosphorylation of extracellular signal-regulated kinase (ERK) by treatment with mitogen-activated protein kinase/ERK kinase (MEK) inhibitors causes two opposing effects, transcriptional upregulation and prompted protein degradation of endogenous BCRP in breast cancer MCF-7 cells. Endogenous BCRP was eventually found to be upregulated. Conversely, treatment with epidermal growth factor was associated with its downregulation in the cells. MEK inhibitors also caused prompted degradation of exogenous BCRP in MCF-7 and gastric cancer NCI-N87 cells that express exogenous BCRP without affecting its transcriptional levels, and potentiated anticancer agents in the cells. A lysosomal inhibitor abolished this prompted degradation of exogenous BCRP, but a proteasome inhibitor did not. Inhibition of p90 ribosomal protein S6 kinase (RSK), one of the downstream effectors of ERK, resulted in transcriptional upregulation of endogenous BCRP but did not affect the protein degradation of exogenous BCRP. The data suggest that BCRP expression is differentially regulated downstream of the MEK-ERK pathway, transcriptionally upregulated through the inhibition of the MEK-ERK-RSK pathway, and posttranscriptionally downregulated through the inhibition of the MEK-ERK-non-RSK pathway. Although the immediate downstream effector of ERK remains to be elucidated, the data provide new insights into regulatory mechanisms of BCRP activity and may assist the development of BCRP-specific expression modulators.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily G, Member 2; ATP-Binding Cassette Transporters; Breast Neoplasms; Butadienes; Cell Line, Tumor; DNA Primers; Enzyme Inhibitors; Epidermal Growth Factor; Extracellular Signal-Regulated MAP Kinases; Female; Gene Expression Regulation, Neoplastic; Genes, myc; Humans; Neoplasm Proteins; Nitriles; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stomach Neoplasms; Up-Regulation

We previously reported that nicotine promoted gastric cancer cell growth via upregulation of cyclooxygenase 2 (COX-2). In the present study, we further investigated whether beta-adrenoceptors, protein kinase C (PKC), and extracellular signal-regulated kinase-1/2 (ERK1/2) were involved in the modulation of COX-2 expression and cell proliferation by nicotine in AGS, a human gastric adenocarcinoma cell line. Results showed that nicotine dose dependently increased the phosphorylation of EKR1/2 and the expression of AP-1 subunits c-fos and c-jun. In this connection, the ERK1/2 inhibitor U0126 abrogated the upregulation of AP-1 and COX-2 as well as cell proliferation induced by nicotine. Moreover, nicotine induced the translocation of PKC-betaI from cytosol to membrane and increased the total levels of PKC expression. Inhibition of PKC by staurosporine attenuated nicotine-induced ERK1/2 phosphorylation and COX-2 expression. Furthermore, atenolol and ICI 118,551, a beta1- and beta2-adrenoceptor antagonist, respectively, reversed the stimulatory action of nicotine on the expression of PKC, ERK1/2 phosphorylation, and COX-2 together with cell proliferation. Collectively, these results suggest that nicotine stimulates gastric cancer cell growth through the activation of beta-adrenoceptors and the downstream PKC-betaI/ERK1/2/COX-2 pathway.

Topics: Adenocarcinoma; Adrenergic beta-Antagonists; Atenolol; Butadienes; Cell Line, Tumor; Cell Proliferation; Cyclooxygenase 2; Dose-Response Relationship, Drug; Enzyme Induction; Extracellular Signal-Regulated MAP Kinases; Humans; Membrane Proteins; Mitogens; Nicotine; Nitriles; Phosphorylation; Propanolamines; Protein Kinase C; Protein Kinase C beta; Protein Kinase Inhibitors; Protein Transport; Receptors, Adrenergic, beta; Signal Transduction; Staurosporine; Stomach Neoplasms; Transcription Factor AP-1

Diallyl disulfide (DADS) is a major constituent of garlic. Previously, we found that DADS both inhibited proliferation in human gastric cancer cells in vitro and in vivo, and induced G2/M arrest. In this study, we investigated whether this differentiation effect was induced by DADS in human gastric cancer MGC803 cells, and whether it was related to an alteration in ERK activity. The results showed that the growth of MGC803 cells was inhibited by DADS. Cells treated with DADS displayed a lower nucleocytoplasmic ratio and tended to form gland and intercellular conjunction structures. The ConA-mediated cell agglutination ratio and cells' ALP specific activity decreased. In MGC803 cells, dye transfer was limited to a few cells neighbouring the dye-injected cell and to a depth of 1-2 layers beneath the scrape site. However, after treatment with DADS, the LY (Lucifer Yellow) was transferred to several cells immediately neighbouring the microinjected cell and to a depth of 2-4 cell layers from the scrape site. This indicated that DADS induced differentiation in MGC803 cells. Western blot analysis revealed that although DADS did not influence the quantity of ERK1/2 protein expressed, it did decrease its phosphorylation in a concentration-dependent manner, compared with the controls. At 30 mg x L(-1), DADS inhibited the activation of ERK1/2 in 15-30 min. These results suggested that the DADS-induced differentiation of MGC803 cells involved an alteration of the ERK1/2 signaling pathway.

Topics: Agglutination; Alkaline Phosphatase; Allyl Compounds; Butadienes; Cell Differentiation; Cell Line, Tumor; Cell Survival; Concanavalin A; Disulfides; Humans; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Nitriles; Phosphoproteins; Phosphorylation; Stomach Neoplasms

Epidemiological studies have demonstrated a strong association between Helicobacter pylori infection and gastric cancer. However, there have been few detailed studies on the mechanism of cellular proliferation by H. pylori. Thus, we examined activation of the proto-oncogene c-fos to elucidate the underlying mechanism of cell proliferation caused by H. pylori. Activation of c-fos was evaluated in human gastric cancer cells (TMK1) by Northern blot and reporter assays with deletion analysis of the c-fos transcriptional control region. c-fos promoter activation and transcription were enhanced when cocultured with cag-positive strains. H. pylori-mediated c-fos promoter activation was inhibited by MEK1/2 inhibitor (U0126). The deletion analysis indicated that serum response element (SRE) was required for the activation of c-fos by H. pylori. In conclusion, c-fos promoter activation and transcription were enhanced through the activation of extracellular signal-regulated kinases (ERK)/mitogen-activated protein kinase (MAPK) cascade in gastric cancer cells when cocultured with H. pylori possessing intact cag PAI. SRE is required for the activation of c-fos by H. pylori. These results suggest a direct involvement of H. pylori infection in cellular proliferation, which may play a role in neoplastic transformation.

Topics: Adult; Aged; Butadienes; DNA Mutational Analysis; Enzyme Inhibitors; Female; Gene Expression Regulation, Neoplastic; Genes, Reporter; Helicobacter pylori; Humans; Male; Middle Aged; Mitogen-Activated Protein Kinase Kinases; Nitriles; Promoter Regions, Genetic; Proto-Oncogene Mas; Proto-Oncogene Proteins c-fos; RNA, Neoplasm; Sequence Deletion; Serum Response Element; Stomach Neoplasms; Transcriptional Activation; Tumor Cells, Cultured

Helicobacter pylori infection induces expression of proinflammatory cytokines such as interleukin (IL)-8 and tumour necrosis factor alpha (TNF-alpha) in gastric mucosa, and their genes have AP-1 binding sites in the promoter region. c-Fos is important for transactivation of AP-1 which has SRE in the promoter region. We conducted this study to confirm H pylori induced transactivation of these binding sites.. Transactivation of SRE and AP-1 was evaluated in human gastric cancer cells TMK1 and MKN45 by luciferase reporter assay in transient transfection. We compared the effects of coculture with four H pylori strains, a cag pathogenicity island (PAI) positive strain TN2, its isogenic vacA negative (TN2-DeltavacA) or cagE negative (TN2-DeltacagE) mutants, and a cag PAI negative clinical isolate T68. Phosphorylation of ERK1/2, JNK, and c-Jun was measured by immunoblot, induction of IL-8 secretion by ELISA, and the effects of MEK by inhibitor U0126.. Both SRE and AP-1 were transactivated by coculture with TN2. Although TN2-DeltavacA induced comparable transactivation, TN2-DeltacagE and T68 showed decreased transactivation of SRE (65% and 51%) and AP-1 (71% and 54%, respectively, of TN2). Heat killed TN2 or indirect contact using a permeable membrane inhibited transactivation. Levels of phosphorylated ERK1/2, JNK, and c-Jun were increased by coculture with TN2. MEK inhibitor U0126 reduced TN2 induced transactivation of SRE and AP1, as well as secretion of IL-8, by 83%, 87%, and 53%, respectively, of TN2.. Transactivation of SRE and AP-1, through ERK/MAPK and JNK/SAPK cascades, respectively, was found in gastric cancer cells cocultured with H pylori. Direct contact with viable bacteria possessing intact cag PAI is a prerequisite for the onset of intracellular signalling leading to AP-1 transactivation.

Topics: Animals; Bacterial Proteins; Butadienes; CpG Islands; DNA-Binding Proteins; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Fungal Proteins; GATA Transcription Factors; Genes, jun; Helicobacter pylori; Humans; Immunoblotting; Interleukin-8; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase Kinases; Nitriles; Phosphorylation; Stomach Neoplasms; Transcriptional Activation; Tumor Cells, Cultured