Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cyclooxygenase-2 (COX-2) expression is a marker of poor prognosis in gastric cancer patients, and its inhibition suppresses gastric tumorigenesis in experimental animal models. The mechanism that leads to COX-2 overexpression in this tumor type is unknown. We have now shown that inhibition of phosphatidylinositol 3-kinase by LY294002 suppresses both basal and phorbol myristate acetate-induced COX-2 expression in TMK-1 and MKN-28 gastric cancer cells. Furthermore, inhibition of glycogen synthase kinase-3beta (GSK-3beta) by SB415286 induced expression of COX-2 mRNA and protein as well as the enzyme activity in the gastric cancer cells. The effect of SB415286 was confirmed by the use of two additional GSK-3beta inhibitors, lithium chloride and SB216763. SB415286 had a modest 1.6-fold stimulatory effect on a 2-kb COX-2 promoter reporter construct, but more importantly, it was shown to block the decay of COX-2 mRNA. In contrast to modulation of phosphatidylinositol 3-kinase/Akt/GSK-3beta pathway, inhibitors of mitogen-activated protein kinases (MEK 1/2, p38, JNK) or the mammalian target of rapamycin did not alter COX-2 expression in gastric cancer cells. Our data show that inhibition of GSK-3beta stimulates COX-2 expression in gastric cancer cells, which seems to be primarily facilitated via an increase in mRNA stability and to a lesser extent through enhanced transcription.
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PMID:Expression of cyclooxygenase-2 is regulated by glycogen synthase kinase-3beta in gastric cancer cells. 1637 52

The mammalian target of rapamycin (mTOR) has become an interesting target for cancer therapy through its influence on oncogenic signals, which involve phosphatidylinositol-3-kinase and hypoxia-inducible factor-1alpha (HIF-1alpha). Since mTOR is an upstream regulator of HIF-1alpha, a key mediator of gastric cancer growth and angiogenesis, we investigated mTOR activation in human gastric adenocarcinoma specimens and determined whether rapamycin could inhibit gastric cancer growth in mice. Expression of phospho-mTOR was assessed by immunohistochemical analyses of human tissues. For in vitro studies, human gastric cancer cell lines were used to determine S6K1, 4E-BP-1 and HIF-1alpha activation and cancer cell motility upon rapamycin treatment. Effects of rapamycin on tumor growth and angiogenesis in vivo were assessed in both a subcutaneous tumor model and in an experimental model with orthotopically grown tumors. Mice received either rapamycin (0.5 mg/kg/day or 1.5 mg/kg/day) or diluent per intra-peritoneal injections. In addition, antiangiogenic effects were monitored in vivo using a dorsal-skin-fold chamber model. Immunohistochemical analyses showed strong expression of phospho-mTOR in 60% of intestinal- and 64% of diffuse-type human gastric adenocarcinomas. In vitro, rapamycin-treatment effectively blocked S6K1, 4E-BP-1 and HIF-1alpha activation, and significantly impaired tumor cell migration. In vivo, rapamycin-treatment led to significant inhibition of subcutaneous tumor growth, decreased CD31-positive vessel area and reduced tumor cell proliferation. Similar significant results were obtained in an orthotopic model of gastric cancer. In the dorsal-skin-fold chamber model, rapamycin-treatment significantly inhibited tumor vascularization in vivo. In conclusion, mTOR is frequently activated in human gastric cancer and represents a promising new molecular target for therapy.
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PMID:Mammalian target of rapamycin is activated in human gastric cancer and serves as a target for therapy in an experimental model. 1723 May 6

AFP-producing gastric carcinoma (AFPGC) is a highly malignant variant of gastric cancer. An effective chemotherapy is needed to improve on the poor outcome of this disease. Survival signals activated by intracellular kinase networks could be involved in chemoresistance in malignant tumors. We investigated the role of a pivotal kinase pathway, the mammalian target of rapamycin complex 1 (mTORC1) pathway, in the effectiveness of chemotherapeutic agents in three AFPGC cell lines (GCIY, FU97 and Takigawa) as well as in four cell lines of conventional-type gastric carcinoma (CGC). AFPGC cells were generally resistant to multiple chemotherapeutic agents, including cisplatin, while CGC cells were generally sensitive. Downstream targets of mTORC1, including p70S6K and 4EBP1, were phosphorylated in all cell lines. Interestingly, cisplatin virtually abolished phosphorylation of p70S6K and 4EBP1 in CGC cells, while phosphorylation was maintained in cisplatin-treated AFPGC cells. The addition of rapamycin, an inhibitor of mTORC1, diminished the remaining activity of mTORC1 and significantly intensified the cytotoxic action of cisplatin in AFPGC cells. These results suggested that persistent activity of mTORC1 signals in cisplatin-treated AFPGC cells is involved in the mechanisms of cisplatin resistance in AFPGC. Finally, combined treatment of rapamycin and cisplatin significantly suppressed the subcutaneously implanted GCIY cells. In conclusion rapamycin may be a potential supplemental agent for the treatment of AFPGC when used in combination with cisplatin.
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PMID:Possible involvement of persistent activity of the mammalian target of rapamycin pathway in the cisplatin resistance of AFP-producing gastric cancer cells. 1756 86

Matrine, from Sophora flavescens, could remarkably inhibit tumor growth and induce apoptosis in various cancer cells in vitro. eIF4E and its inhibitor 4E-BP1 play key roles in regulating mRNA translation and cell proliferation. However, it remained elusive whether matrine inhibited cancer cells growth through attenuating the activity of 4E-BP1. In this study, we analyzed the effects of matrine on 4E-BP1 and eIF4E in gastric cancer MKN45 cells. Immunoblots showed that matrine inhibited the activity of eIF4E through dephosphorylation of 4E-BP1 in a dose- and time-dependent manner. We found that matrine inactivated Erk1/2, an upstream regulator of 4E-BP1 and eIF4E, and remarkably reduced the phosphorylation level of 4E-BP1 and eIF4E, whereas 4E-BP1 was little influenced by JNK, p38 or Akt/mTOR. Inactivation of PP2A obviously decreased the phosphorylation of 4E-BP1 in matrine-treated cells. These findings suggested that matrine inhibits the activity of eIF4E by dephosphorylating 4E-BP1, which partly counts for the growth inhibition in gastric MKN45 cells.
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PMID:Matrine inhibits the activity of translation factor eIF4E through dephosphorylation of 4E-BP1 in gastric MKN45 cells. 1782 71

Macrophage inhibitory cytokine-1 (MIC-1) is a member of the transforming growth factor-beta superfamily, which is overexpressed in a variety of human cancers, including breast and gastric cancer. The function of MIC-1 in cancer remains controversial and its signaling pathways remain poorly understood. In this study, we demonstrate that MIC-1 induces the transactivation of ErbB2 in SK-BR-3 breast and SNU-216 gastric cancer cells. MIC-1 induced a significant phosphorylation of Akt and ERK-1/2, and also effected an increase in the levels of tyrosine phosphorylation of ErbB1, ErbB2 and ErbB3 in SK-BR-3 and SNU-216 cells. The treatment of these cells with AG825 and AG1478, inhibitors specific for ErbB2 tyrosine kinase, resulted in the complete abolition of MIC-1-induced Akt and ERK-1/2 phosphorylation. Furthermore, the small-interfering RNA-mediated downregulation of ErbB2 significantly reduced not only the phosphorylation of Akt and ERK-1/2 but also the invasiveness of the cells induced by MIC-1. Our results show that ErbB2 activation performs a crucial function in MIC-1-induced signaling pathways. Further investigations revealed that MIC-1 induced the expression of the hypoxia inducible factor-1alpha protein and the expression of its target genes, including vascular endothelial growth factor, via the activation of the mammalian target of rapamycin (mTOR) signaling pathway. Stimulation of SK-BR-3 with MIC-1 profoundly induces the phosphorylation of mTOR and its downstream substrates, including p70S6K and 4E-BP1. Collectively, these results show that MIC-1 may participate in the malignant progression of certain human cancer cells that overexpress ErbB2 through the transactivation of ErbB2 tyrosine kinase.
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PMID:Macrophage inhibitory cytokine-1 activates AKT and ERK-1/2 via the transactivation of ErbB2 in human breast and gastric cancer cells. 1825 6

Patients with advanced gastric carcinoma, especially peritoneal dissemination, have a poor prognosis even after any treatment. Chemokines are now known to play an important role in cancer growth and metastasis. We recently reported that the chemokine CXCL12 plays an important role in the development of peritoneal carcinomatosis from gastric carcinoma. In this study, we investigated signalling pathway involved in the peritoneal carcinomatosis induced by chemokine CXCL12. Akt was rapidly and strongly phosphorylated by chemokine CXCL12. CXCL12 also induced the activation of p70S6K (S6K) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1) included in mammalian target of rapamycin (mTOR) pathways which are located downstream of Akt, resulting in enhancements of metastatic properties such as MMP production, cell migration and cell growth in peritoneal disseminated gastric cancer, NUGC4 cells. Furthermore, mTOR inhibitor rapamycin not only drastically inhibited migration and MMP production, but also induced type II programmed cell death, autophagic cell death. In the present study, we have shown for the first time that the mTOR pathway plays a central role in the development of peritoneal carcinomatosis, and blocking this pathway induces autophagic cell death in disseminated gastric cancer. Therefore, blocking on the CXCR4/mTOR signalling pathway may be useful for the future development of a more effective therapeutic strategy for gastric cancer involved in peritoneal dissemination.
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PMID:Blocking on the CXCR4/mTOR signalling pathway induces the anti-metastatic properties and autophagic cell death in peritoneal disseminated gastric cancer cells. 1837 14

Cysteine-rich 61 (Cyr61/CCN1), one of the members of CCN family, has been implicated in the progression of human malignancies. Previously, our studies have demonstrated that Cyr61/CCN1 has a role in promoting gastric cancer cell invasion, but the mechanism is not clear yet. Here, we found that hypoxia-inducing factor-1alpha (HIF-1alpha) protein, but not mRNA, expression was significantly elevated in gastric cancer cells overexpressing Cyr61. Supportively, a profound reduction of endogenous HIF-1alpha protein was noted in one highly invasive cell line, TSGH, when transfected with antisense Cyr61. By comparison, the induction kinetics of HIF-1alpha protein by recombinant Cyr61 (rCyr61) was distinct from that of insulin-like growth factor-1 and CoCl(2) treatment, both well known for induction of HIF-1alpha. Using cycloheximide and MG132, we demonstrated that the Cyr61-mediated HIF-1alpha up-regulation was through de novo protein synthesis, rather than increased protein stability. rCyr61 could also activate the PI3K/AKT/mTOR and ERK1/2 signaling pathways, both of which were essential for HIF-1alpha protein accumulation. Blockage of HIF-1alpha activity in Cyr61-expressing cells by transfecting with a dominant negative (DN)-HIF-1alpha strongly inhibited their invasion ability, suggesting that elevation in HIF-1alpha protein is vital for Cyr61-mediated gastric cancer cell invasion. In addition, several HIF-1alpha-regulated invasiveness genes were examined, and we found that only plasminogen activator inhibitor-1 (PAI-1) showed a significant increase in mRNA and protein levels in cells overexpressing Cyr61. Treatment with PAI-1-specific antisense oligonucleotides or function-neutralizing antibodies abolished the invasion ability of the Cyr61-overexpressing cells. Transfection with dominant negative-HIF-1alpha to block HIF-1alpha activity also effectively reduced the elevated PAI-1 level. In conclusion, our data provide a detailed mechanism by which Cyr61 promoted gastric cancer cell invasive ability via an HIF-1alpha-dependent up-regulation of PAI-1.
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PMID:Involvement of hypoxia-inducing factor-1alpha-dependent plasminogen activator inhibitor-1 up-regulation in Cyr61/CCN1-induced gastric cancer cell invasion. 2803 33

Despite the numerous efforts of randomized studies on advanced gastric cancer, no globally accepted standard regimen has yet been established. Two triplet regimens have already demonstrated significant survival prolongation in Western studies. However, the benefit seems to be marginal, and these regimens may be replaced by recently published newer generation regimens for which favorable survival is reported. At present, the combination of 5-fluorouracil (5-FU) and platinum analog is still the most widely accepted standard regimen worldwide: 5-FU can be replaced by S-1 or capecitabine, and cisplatin by oxaliplatin. In Japan, S-1 plus cisplatin is the most reasonable first-line standard, based on recent randomized studies. Some early clinical studies using molecular targeting agents have shown promising activity, particularly in combination with cytotoxic agents for gastric cancer. Several targeting agents such as trastuzumab, bevacizumab, and lapatinib are now under investigation in international randomized studies, including in Japan. These agents have shown a survival benefit in other tumor types. The next-generation targeting agents, including mammalian target of rapamycin inhibitor and a c-Met tyrosine kinase inhibitor, are also being evaluated in early clinical studies in association with biology research. Such agents can be advantageously used in gastric cancer studies, which, because of the ease with which tumor tissues can be obtained by endoscopy and the high incidence of gastric cancer in Japan, might advance the frontiers of biologic therapy. These efforts should result not only in further clinical advances but also in tailored medicine.
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PMID:Chemotherapy for metastatic gastric cancer: past, present, and future. 1845 40

The present study aimed to evaluate the relationship between mTOR signaling pathway and DNA methylation in cell survival, cell cycle, gene expression and protein level on human gastric cancer cells. Human gastric cancer cell lines, MKN45 and SGC7901 were treated with 5-aza-dC, rapamycin and/or LY294002. Cell viability was analyzed by MTT. Cell cycle distribution was evaluated by flow cytometry (FCM). The transcription level of PTEN and p27 ( Kip1 ) genes was detected by using real-time PCR. Protein expressions were detected by Western blotting. We found that cell viability was moderately reduced when treated with 5-aza-dC alone, but remarkably reduced when mTOR pathway was inhibited together (P<0.01). mTOR inhibition enhances the effects of 5-aza-dC on arresting cell cycle at G2 phase in human gastric cancer cell lines. The expression of PTEN and p27 ( Kip1 ) mRNA was remarkably increased in the gastric cancer cells treated with combind drugs (P<0.01). Phosphorylation of Akt, p70S6K and 4E-BP1 were significantly reduced in the cells treated with LY294002 or RAPA (P<0.01), but we failed to find that 5-aza-dC enhance these effects. We suggested that mTOR inhibition could enhance the effects of 5-aza-dC on suppressing cell proliferation and arresting cell cycle in human gastric cancer cell lines, which might be a potential target for tumor therapy.
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PMID:Mammalian target of rapamycin pathway inhibition enhances the effects of 5-aza-dC on suppressing cell proliferation in human gastric cancer cell lines. 1862 47

The mammalian target of rapamycin (mTOR), a Ser/Thr protein kinase that mediates intracellular signalling related to cell growth, proliferation, and differentiation, has received considerable interest as a possible target for cancer treatment. We evaluated the correlation of mTOR expression with clinicopathological features, outcomes, and the expression of Akt, an upstream regulator of mTOR, in gastric cancer. Tumour samples were obtained from 109 patients with gastric adenocarcinomas who underwent a radical gastrectomy. The expressions of phosphorylated mTOR (p-mTOR) and phosphorylated Akt (p-Akt) in the cytoplasm and in the nucleus were analysed by immunohistochemical staining. Cytoplasmic p-mTOR expression positively correlated with the depth of tumour invasion (T1 vs T2-4, P=0.003), involved lymph nodes (P=0.010), and tumour stage (I vs II-IV, P=0.002). In contrast, nuclear p-mTOR expression negatively correlated with these variables (P<0.001,=0.035, and <0.001). Cytoplasmic p-mTOR expression was associated with significantly poorer relapse-free survival (RFS, P=0.037) and overall survival (OS, P=0.024), whereas nuclear p-mTOR expression was associated with better RFS and OS (P=0.029, 0.059). Neither cytoplasmic nor nuclear p-Akt expression was associated with any clinicopathological factor or with survival. Localisation of p-mTOR may play an important role in tumour progression and outcomes in patients with gastric cancer.
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PMID:Relation between outcomes and localisation of p-mTOR expression in gastric cancer. 1922 2


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