Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P31749 (AKT)
 22,954 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumorigenesis of glioblastoma multiforme (GBM), the most aggressive primary intracranial neoplasm, is associated with aberrant PI3K/AKT/mTOR signaling. Inhibitors of mTOR, such as rapamycin (RAPA) or its analogs, have provided limited benefit. Here, we aim to decipher the signaling pathways involved in RAPA resistance. We found that RAPA induced a time-dependent activation of MAPK (pERK1/2) and MEK1/2. Inhibition of upstream kinase MEK1/2 by U0126 partially suppressed RAPA-induced ERK1/2 activation. Small interfering RNA suppression of mTOR resulted in higher pERK1/2 levels and pre-treatment with RAPA potentiated PDGF-induced activation of ERK1/2. Furthermore, nuclear localization of pERK1/2 was evident following RAPA, which was MEK1/2-dependent. Cell proliferation was significantly suppressed by combined MEK1/2 and mTOR inhibition compared to mTOR inhibition alone. These results demonstrate activation of a mitogenic pathway involving a feedback mechanism between mTOR and PI3K/ERK1/2 and support the basis for combined inhibitors in GBM treatment.
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PMID:Inhibition of mTOR Activates the MAPK Pathway in Glioblastoma Multiforme. 1999 30

Over the last two decades, significant advances have been made in percutaneous coronary intervention (PCI) for the treatment of atherosclerotic plaques. However, restenosis after PCI still challenges both vascular biologists and interventional cardiologists. In this study, we found that caffeic acid phenethyl ester (CAPE) displayed an inhibitory effect on human coronary smooth muscle cell (HCSMC) growth and migration. Flow cytometry analysis showed that the ratio of S phase increased after exposing cells to CAPE for 48-72 h. Pretreatment of cells with CAPE significantly suppressed Cyclin E, CDK2, Cyclin A, and proliferating-cell nuclear antibody expression. We demonstrated that CAPE inhibited AKT 1 and MEK1/2 activation. Using a local infusion system, CAPE was able to regress the intima thickening of the iliac artery in rabbits after balloon injury. The percentage of intimal thickening decreased significantly to 55.0 +/- 0.12 in the group after local CAPE infusion compared to the group after saline infusion (98.3 +/- 0.41%). In conclusion, CAPE can inhibit the proliferation and migration of HCSMCs by inducing cell cycle arrest. Decreased cell cycle genes and associated signaling pathway target gene expression may mediate anti-proliferative and anti-migration effects of CAPE. Furthermore, CAPE prevents intima thickening in rabbits after balloon angioplasty. These results indicate that CAPE may have therapeutic relevance for the prevention of restenosis during PCI in the treatment of coronary artery diseases.
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PMID:Caffeic acid phenethyl ester inhibits arterial smooth muscle cell proliferation and migration in vitro and in vivo using a local delivery system. 2000 10

Previously, we showed that mild heat shock modulates patterns of cell death in response to glucose deprivation (GD), a common characteristic of the tumor microenvironment, by switching necrosis to apoptosis through ERK-dependent suppression of reactive oxygen species production in A549 cells. In the present study, we further examined the molecular mechanism underlying mild heat shock-induced necrosis-to-apoptosis switch. We examined the possible implication of p53 and heat shock proteins (HSPs) in the mechanism. Inhibition of p53 by pifithrin-alpha or p53 siRNA markedly suppressed apoptosis induced by heat shock/GD. On the other hand, silencing of HSP27, but not of HSP70, reversed heat shock/GD-induced apoptosis to necrosis, and HSP27 overexpression suppressed GD-induced necrosis. We further demonstrate that mild heat shock activated AKT and ERK1/2 through phosphorylation. Prevention of PI3K by LY294002 blocked heat shock/GD-induced apoptosis without reversing the cell death mode to necrosis, while inhibition of MEK1/2 by U0126 reversed heat shock/GD-induced apoptosis to necrosis, indicating a different role(s) of PI3K and ERK1/2 in heat shock/GD-induced cell death mode determination. We also found that mild heat shock increased HSP27 and p53 protein levels dependent on PI3K and suppressed the GD-induced increase in RIPA-insoluble HSP27 and p53 protein levels dependent on PI3K and ERK1/2. In conclusion, these results indicate that PI3K-dependent HSP27 and p53 induction and PI3K- and ERK1/2-dependent inhibition of the GD-induced increase in RIPA-insoluble HSP27 and p53 protein levels by heat play a key role(s) in heat shock-mediated switch of GD-induced necrosis to apoptosis.
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PMID:Implication of PI3K-dependent HSP27 and p53 expression in mild heat shock-triggered switch of metabolic stress-induced necrosis to apoptosis in A549 cells. 2004 73

High-throughput cellular profiling has successfully stimulated early drug discovery pipelines by facilitating targeted as well as opportunistic lead finding, hit annotation and SAR analysis. While automation-friendly universal assay formats exist to address most established drug target classes like GPCRs, NHRs, ion channels or Tyr-kinases, no such cellular assay technology is currently enabling an equally broad and rapid interrogation of the Ser/Thr-kinase space. Here we present the foundation of an emerging cellular Ser/Thr-kinase platform that involves a) coexpression of targeted kinases with promiscuous peptide substrates and b) quantification of intracellular substrate phosphorylation by homogeneous TR-FRET. Proof-of-concept data is provided for cellular AKT, B-RAF and CamK2delta assays. Importantly, comparable activity profiles were found for well characterized B-Raf inhibitors in TR-FRET assays relying on either promiscuous peptide substrates or a MEK1(WT) protein substrate respectively. Moreover, IC(50)-values correlated strongly between cellular TR-FRET assays and a gold standard Ba/F3 proliferation assay for B-Raf activity. Finally, we expanded our initial assay panel by screening a kinase-focused cDNA library and identified starting points for >20 cellular Ser/Thr-kinase assays.
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PMID:Cellular Ser/Thr-kinase assays using generic peptide substrates. 2016 28

We have explored the mechanism by which inhibition of multiple cytoprotective cell-signaling pathways enhance melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) toxicity toward invasive primary human glioblastoma multiforme (GBM) cells, and whether improving adenoviral infectivity/delivery of mda-7/IL-24 enhances therapeutic outcome in animals containing orthotopic xenografted GBM cells. The toxicity of a serotype 5 recombinant adenovirus to express MDA-7/IL-24 (Ad.5-mda-7) was enhanced by combined molecular or small molecule inhibition of mitogen-activated extracellular regulated kinase (MEK)1/2 and phosphatidyl inositol 3-kinase (PI3K) or AKT; inhibition of mammalian target of rapamycin (mTOR) and MEK1/2; and the HSP90 inhibitor 17AAG. Molecular inhibition of mTOR/PI3K/MEK1 signaling in vivo also enhanced Ad.5-mda-7 toxicity. In GBM cells of diverse genetic backgrounds, inhibition of cytoprotective cell-signaling pathways enhanced MDA-7/IL-24-induced autophagy, mitochondrial dysfunction and tumor cell death. Due partly to insufficient adenovirus serotype 5 gene delivery this therapeutic approach has shown limited success in GBM. To address this problem, we employed a recombinant adenovirus that comprises the tail and shaft domains of a serotype 5 virus and the knob domain of a serotype 3 virus expressing MDA-7/IL-24, Ad.5/3-mda-7. Ad.5/3-mda-7 more effectively infected and killed GBM cells in vitro and in vivo than Ad.5-mda-7. Future combinations of these approaches hold promise for developing an effective therapy for GBM.
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PMID:Inhibition of multiple protective signaling pathways and Ad.5/3 delivery enhances mda-7/IL-24 therapy of malignant glioma. 2017 72

PURPOSE. To describe how developing amacrine cells and retinal ganglion cells (RGCs) differ in survival signaling and global gene expression. METHODS. Amacrine cells were immunopurified and processed for gene microarray analysis. For survival studies, purified amacrine cells were cultured at low density in serum-free medium, with and without peptide trophic factors and survival pathway inhibitors. The differences in gene expression between amacrine cells and RGCs were analyzed by comparing the transcriptomes of these two cell types at the same developmental ages. RESULTS. The amacrine cell transcriptome was very dynamic during development. Amacrine cell gene expression was remarkably similar to that of RGCs, but differed in several gene ontologies, including polarity- and neurotransmission-associated genes. Unlike RGCs, amacrine cell survival in vitro was independent of cell density and the presence of exogenous trophic factors, but necessitated Erk activation via MEK1/2 and AKT signaling. Finally, comparison of the gene expression profile of amacrine cells and RGCs provided a list of polarity-associated candidate genes that may explain the inability of amacrine cells to differentiate axons and dendrites as RGCs do. CONCLUSIONS. Comparison of the gene expression profile between amacrine cells and RGCs may improve our understanding of why amacrine cells fail to differentiate axons and dendrites during retinal development and of what makes amacrine cells differ in their resistance to neurodegeneration. Switching RGCs to an amacrine cell-like state could help preserve their survival in neurodegenerative diseases like glaucoma, and amacrine cells could provide a ready source of replacement RGCs in such optic neuropathies.
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PMID:Amacrine cell gene expression and survival signaling: differences from neighboring retinal ganglion cells. 2044 9

Pancreatic ductal epithelial cells (PDECs) were induced to differentiate into insulin-producing cells by hepatocyte growth factor (HGF) in our previous study, but the mechanism through which this induction occurs is still unknown. HGF is a ligand that activates a tyrosine kinase encoded by the c-Met proto-oncogene. This activation is followed by indirect activation of multiple downstream signal transduction pathways (including MAPKs and the PI3K/AKT signaling pathways) that initiate various biological effects. Therefore, we speculated that the differentiation of PDECs is through either the MAPK signaling pathway or the PI3K/AKT signaling pathway. To test this hypothesis, isolated PDECs from adult rats were stimulated by adding HGF to their medium for 28days. Then, the expression levels of several protein kinases, including MAPKs (ERK1/2, p38, and JNK) and AKT, were determined by Western blotting to determine if specific protein kinases are activated in these pathways. Subsequently, re-isolated from adult rats and cultured PDECs were pre-treated with specific inhibitors of proteins shown to be activated in these signaling pathways; these cells were then induced to differentiate by the addition of HGF. The expression levels of protein kinases were determined by Western blotting, and the differentiation rate of insulin-positive cells was determined by flow cytometry. The change of PDEC differentiation rates were compared between the groups in which cells with or without inhibitors pretreatment to determine the specific signaling pathway(s) that may be involved in HGF-induced differentiation of PDECs. After isolating PDECs and stimulating them with HGF for 28days, the expression levels of phosphorylated ERK1/2 as well as total and phosphorylated AKT of cultured cells were significantly increased compared to the normal control group (p<0.05), suggesting that the signaling pathways involving ERK1/2 and Akt (MEK-ERK and PI3K-AKT) are activated during HGF-induced PDEC differentiation. MEK1/2 or PI3K inhibitors were separately added to the culture medium of PDECs pre-treated with HGF. These results show that compared to the HGF-treated group, the differentiation rate of insulin-positive cells was significantly decreased in the HGF/LY294002 (PI3K inhibitor) group (13.47+/-1.57% vs. 33.47+/-1.34%, p<0.05); however, the differentiation rate of insulin-positive cells was not significantly different in the HGF/PD98059 (MEK1/2 inhibitor) group. These data suggest that HGF induces PDECs to differentiate into insulin-producing cells through the PI3K/AKT signaling pathway.
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PMID:Mechanisms of hepatocyte growth factor-mediated signaling in differentiation of pancreatic ductal epithelial cells into insulin-producing cells. 2059 23

The co-expression of KIT receptor and its ligand stem cell factor (SCF) has been reported in biopsy specimens of Merkel cell carcinoma (MCC). However, the functional role of SCF/KIT in the pathogenesis of this aggressive tumor has not been elucidated. The present study reports expression and effects of SCF and KIT in the Merkel cell carcinoma cell line MCC-1 in vitro. SCF and KIT were endogenously co-expressed in MCC-1 cells. Exogenous soluble SCF modulated KIT receptor mRNA and protein expression, stimulated growth of MCC-1 cells, upregulated endogenous activation of KIT, AKT, and of extracellular signal-regulated kinase (ERK) 1/2 signaling pathway. On the contrary, an inhibitory antibody that neutralized the KIT ligand binding site, reduced growth of MCC-1 cells, as did high doses of the KIT kinase inhibitors imatinib and nilotinib. Also, inhibitors of KIT downstream effectors, U0126 that blocks MEK1/2 as well as wortmannin and LY294002 that inhibit phosphatidylinositol 3-kinase-dependent AKT phosphorylation, inhibited the proliferation of MCC-1 cells. These data support the hypothesis that KIT is activatable by paracrine or autocrine tumor cell-derived SCF and stimulates growth of Merkel cell carcinoma in vitro. Blockade of KIT and the downstream signaling cascade at various levels results in inhibition of Merkel cell carcinoma growth in vitro, suggesting targets for therapy of this cancer.
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PMID:KIT receptor activation by autocrine and paracrine stem cell factor stimulates growth of merkel cell carcinoma in vitro. 2085 9

AZD6244 (ARRY-142886) is an inhibitor of MEK1/2 and can inhibit cell proliferation or induce apoptosis in a cell-type dependent manner. The precise molecular mechanism of AZD6244-induced apoptosis is not clear. To investigate mechanisms of AZD6244 induced apoptosis in human lung cancer, we determined the molecular changes of two subgroups of human lung cancer cell lines that are either sensitive or resistant to AZD6244 treatment. We found that AZD6244 elicited a large increase of Bim proteins and a smaller increase of PUMA and NOXA proteins, and induced cell death in sensitive lung cancer cell lines, but had no effect on other Bcl-2 related proteins in those cell lines. Knockdown of Bim by siRNA greatly increased the IC(50) and reduced apoptosis for AZD6244 treated cells. We also found that levels of endogenous p-Thr32-FOXO3a and p-Ser253-FOXO3a were lower in AZD6244-sensitive cells than in AZD6244-resistant cells. In the sensitive cells, AZD6244 induced FOXO3a nuclear translocation required for Bim activation. Moreover, the silencing of FOXO3a by siRNA abrogated AZD6244-induced cell apoptosis. In addition, we found that transfection of constitutively active AKT up-regulated p-Thr32-FOXO3a and p-Ser253-FOXO3a expression and inhibited AZD6244-induced Bim expression in sensitive cells. These results show that Bim plays an important role in AZD6244-induced apoptosis in lung cancer cells and that the PI3K/AKT/FOXO3a pathway is involved in Bim regulation and susceptibility of lung cancer cells to AZD6244. These results have implications in the development of strategies to overcome resistance to MEK inhibitors.
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PMID:Apoptosis induction by MEK inhibition in human lung cancer cells is mediated by Bim. 2088 57

The majority of melanomas show constitutive activation of the RAS-RAF-MAP/ERK kinase (MEK)-mitogen-activated protein kinase (MAPK) pathway. AZD6244 is a selective MEK1/2 inhibitor that markedly reduces tumor P-MAPK levels, but it produces few clinical responses in melanoma patients. An improved understanding of the determinants of resistance to AZD6244 may lead to improved patient selection and effective combinatorial approaches. The effects of AZD6244 on cell growth and survival were tested in a total of 14 Braf-mutant and 3 wild-type human cutaneous melanoma cell lines. Quantitative assessment of phospho-protein levels in the Braf-mutant cell lines by reverse phase protein array (RPPA) analysis showed no significant association between P-MEK or P-MAPK levels and AZD6244 sensitivity, but activation-specific markers in the phosphoinositide 3-kinase (PI3K)-AKT pathway correlated with resistance. We also identified resistant cell lines without basal activation of the PI3K-AKT pathway. RPPA characterization of the time-dependent changes in signaling pathways revealed that AZD6244 produced durable and potent inhibition of P-MAPK in sensitive and resistant Braf-mutant cell lines, but several resistant lines showed AZD6244-induced activation of AKT. In contrast, sensitive cell lines showed AZD6244 treatment-induced upregulation of PTEN protein and mRNA expression. Inhibition of AKT, TORC1/2, or insulin-like growth factor I receptor blocked AZD6244-induced activation of AKT and resulted in synergistic cell killing with AZD6244. These findings identify basal and treatment-induced regulation of the PI3K-AKT pathway as a critical regulator of AZD6244 sensitivity in Braf-mutant cutaneous melanoma cells and the novel regulation of PTEN expression by AZD6244 in sensitive cells, and suggest new combinatorial approaches for patients.
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PMID:Basal and treatment-induced activation of AKT mediates resistance to cell death by AZD6244 (ARRY-142886) in Braf-mutant human cutaneous melanoma cells. 2095 81


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