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

Acute irreparable UV-induced DNA damage leads to apoptosis of epidermal keratinocytes (KC) and the formation of sunburn cells, whereas less severely damaged cells survive but harbor the potential of tumor formation. Here we report that hepatocyte growth factor/scatter factor (HGF/SF) prevents UVB-induced apoptosis in primary KC cultured in vitro. When we analyzed the signaling pathways initiated by the HGF/SF receptor c-met, we found that the phosphatidylinositol (PI) 3-kinase and its downstream-element AKT and the mitogen-activated protein (MAP) kinase were activated. Inhibition of PI 3-kinase led to a complete abrogation of the anti-apoptotic effect of HGF/SF, whereas blockade of the MAP kinase pathway had no effect. In contrast to the observation with primary KC, HGF/SF could not enhance survival after UVB irradiation of HaCaT and A431 cell lines, despite the fact that in these cells the PI 3-kinase and MAP kinase pathways were also activated by HGF/SF. Cell cycle analysis of KC revealed a G(2)/M arrest after UVB irradiation and a complete loss of proliferating cells. Because HGF/SF in the skin is produced by dermal fibroblasts, our findings suggest that the HGF/SF-mediated rescue of KC from apoptosis represents an important paracrine loop by which UVB-damaged KC can be kept alive to maintain the epidermal barrier function but cannot further proliferate, thereby preventing the induction of epithelial skin tumors.
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PMID:Hepatocyte growth factor/scatter factor inhibits UVB-induced apoptosis of human keratinocytes but not of keratinocyte-derived cell lines via the phosphatidylinositol 3-kinase/AKT pathway. 1182 97

The SGK1 protein belongs to the AGC gene family of kinases that are regulated by phosphorylation mediated by PDK1. SGK1 regulation is accomplished by several pathways including growth-factor and stress-mediated signaling. We have expanded the analysis of SGK1 regulation in epithelial cells. We used HA-tagged SGK1 to transiently transfect MDCK cells and study the regulation of SGK1 upon stimulation with HGF, cAMP or upon adhesion of the cells to immobilized fibronectin. In addition, we studied the regulation of SGK1 activity by small GTP-binding proteins of the Rho family. Treatment of MDCK cells with HGF leads to a time-dependent activation of SGK1 that is blocked by wortmanin. This activation requires the conserved phosphorylation site present in the activation loop of the kinase (T256 in SGK1) and the phosphorylation site present in a hydrophobic domain at its C-terminus (S422 in SGK1), which are targets for PDK1/PDK2-mediated regulation of SGK1. We tested whether SGK1 could be activated by cAMP as it contains a putative PKA site. We were unable to demonstrate a significant activation of HA-SGK1 by cAMP stimulation under conditions where we detect cAMP-mediated phosphorylation of the transcription factor CREB. Cotransfection of SGK1 with activated small GTP-binding proteins revealed that Rac1, but not Rho or Rap1, induces activation of SGK1. However, this activation was wortmanin insensitive and dominant-negative Rac1 did not inhibit the HGF-mediated activation of SGK1. Adhesion of MDCK cells to immobilized fibronectin also leads to activation of SGK1. However, it appears that the integrin-mediated activation of HA-SGK1 differs from AKT activation in the fact that AKT phosphorylation was blocked by wortmanin (or LY294002) whereas HA-SGK1 was not. The adhesion-dependent activation, however, requires the intact phosphorylation sites of SGK1. Co-transfection of HA-SGK1 with RacV12 results in increased activity in adherent cells compared with HA-SGK1 alone. Since RacN17 failed to inhibit adhesion dependent-activation of SGK1, it suggests that integrin activation is achieved by a parallel Rac-independent pathway. The activation of SGK1 by HGF and integrin provides a link between HGF-mediated protection of MDCK from de-attachment induced apoptosis (anoikis). We demonstrate that dephosphorylation of the transcription factor FKRHL1 induced by cell de-attachment is prevented by activated SGK1, suggesting that SGK1 regulates cell survival pathways. In summary, we demonstrate that SGK1 activation could be achieved through signaling pathways involved in the regulation of cell survival, cell-cell and cell-matrix interactions. SGK1 activation can be accomplished via HGF, PI-3K-dependent pathways and by integrin-mediated, PI-3K independent pathways. In addition, activation of SGK1 by the small GTP-binding protein Rac1 has been observed.
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PMID:Activation of SGK1 by HGF, Rac1 and integrin-mediated cell adhesion in MDCK cells: PI-3K-dependent and -independent pathways. 1195 29

Signal transduction downstream HGF receptor (MET) activation involves multiple pathways that account for mitogenesis, motility and morphogenesis in a cell type-dependent fashion. MET receptor is aberrantly expressed in almost 100% of human osteosarcomas. We analyzed the effect of the MET receptor activation in five human osteosarcoma cell lines evaluating the levels of HGF-dependent activation of MAPK and PKB/AKT as biochemical readouts of mitogenic and invasive responses, respectively. All the cell lines tested expressed high levels of the MET proto-oncogene. Four cell lines showed activation of the MAPK cascade upon HGF stimulation, suggesting that this growth factor serves a common proliferative function in osteosarcomas. Two lines showed activation of PKB/AKT that is known to be involved in migration mediated by HGF receptor. Accordingly, cell lines where MAPK cascade was activated responded to HGF with increased proliferation, while induction and inhibition of PKB/AKT activity corresponded to acquisition or block of the invasive-motile response to HGF, respectively. Both the HGF dependent responses were reverted by the specific MET inhibitor K252a. These data show that HGF activates both the mitogen and motogen machinery in osteosarcoma cells and suggest that HGF might promote their malignant behavior by concomitant activation of different pathways and biological functions.
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PMID:Role of the MET/HGF receptor in proliferation and invasive behavior of osteosarcoma. 1270 13

Ionizing or ultraviolet radiation-induced cellular survival signaling pathways induce development of cancer and insensitivity of tumor cells to radiation therapy. Accumulating evidence suggests that the phosphatidylinositide 3-kinase (PI3K)/AKT signal pathway is a major contributor to radioresistance. In many cell types PI3K/AKT signaling is a key cytoprotective response downstream of the EGFR family receptors and mediated carcinogenesis. Cytokines, such as HGF, IGF-I, and IL-6 also protects cells against apoptosis induced by radiation through PI3K/AKT pathway. The mechanics by which PI3K/AKT signaling functions in radiation responses may include its regulation of mitochondrial proteins, transcription factors, translation machinery, and cell-cycle progression. In addition, cross-talk between the PI3K/AKT pathway and mitogen-activated protein kinases, protein kinase A, and protein kinase C signal pathway may also play an important role.
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PMID:Phosphatidylinositide 3-kinase/AKT in radiation responses. 1516 54

Recent studies have shown that selective cyclooxygenase-2 (COX-2) inhibitors induce growth inhibition and cell cycle arrest in hepatocellular carcinoma (HCC) cell lines. However, the mechanism by which COX-2 inhibitors regulate the cell cycle and whether or not growth signal pathways are involved in the growth inhibition remain unclear. In this study, we investigated the mechanisms of growth inhibition and cell cycle arrest by etodolac, a selective COX-2 inhibitor, in HCC cell lines, HepG2 and PLC/PRF/5, by studying cell cycle regulatory proteins, and the MAP kinase and PDK1-PKB/AKT signaling pathways. Etodolac inhibited growth and PCNA expression and induced cell cycle arrest in both HCC cell lines. Etodolac induced p21WAF1/Cip1 and p27Kip1 expression and inhibited CDK2, CDK4, CDC2, cyclin A and cyclin B1 expression, but did not affect cyclin D1 or cyclin E. HGF and 10% FBS induced ERK phosphorylation, but phosphorylation of p38, JNK and AKT was down-regulated by etodolac. PD98059, a selective inhibitor of ERK phosphorylation, induced growth inhibition, the expression of p27Kip1 and cell cycle arrest. In conclusion, p21WAF1/Cip1, p27Kip1, CDK2, CDK4, CDC2, cyclin A, cyclin B1 and the MAP kinase signaling pathway are involved in growth inhibition and cell cycle arrest by a selective COX-2 inhibitor in HCC cell lines.
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PMID:Involvement of cell cycle regulatory proteins and MAP kinase signaling pathway in growth inhibition and cell cycle arrest by a selective cyclooxygenase 2 inhibitor, etodolac, in human hepatocellular carcinoma cell lines. 1529 30

Small cell lung cancer (SCLC) is a difficult disease to treat and sometimes has overexpression or mutation of c-Met receptor tyrosine kinase. The effects of c-Met/hepatocyte growth factor (c-Met/HGF, ligand for c-Met) on activation of reactive oxygen species (ROS) was determined. HGF stimulation of c-Met-overexpressing H69 SCLC cells (40 ng/ml, 15 min) resulted in an increase of ROS, measured with fluorescent probe 2'-7'-dichlorofluorescein diacetate (DCFH-DA) or dihydroethidine (DHE) but not in c-Met-null H446 cells. ROS was increased in juxtamembrane (JM)-mutated variants (R988C and T1010I) of c-Met compared with wild-type c-Met-expressing cells. ROS was significantly inhibited by preincubation of SCLC cells with pyrrolidine dithiocarbamate (PDTC, 100 microM) and/or SU11274 (small molecule c-Met tyrosine kinase inhibitor, 2 microM) for 3 h. PDTC and SU11274 also abrogated the HGF proliferative signal and cell motility in a cooperative fashion. H(2)O(2) treatment of SCLC cells (over 15 min) led to phosphorylation of c-Met receptor tyrosine kinase and further upregulated downstream phosphorylation of phospho-AKT, ERK1/2, and paxillin in a dose-dependent manner (125 microM to 500 microM). c-Met is an important target in lung cancer, and the pathways responsible for ROS generation together may provide novel therapeutic intervention.
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PMID:Activation of HGF/c-Met pathway contributes to the reactive oxygen species generation and motility of small cell lung cancer cells. 1732 84

Uterine leiomyomas (fibroids) are benign tumors that are prevalent in women of reproductive age. Research suggests that activated receptor tyrosine kinases (RTKs) play an important role in the enhanced proliferation observed in fibroids. In this study, a phospho-RTK array technique was used to detect RTK activity in leiomyomas compared with myometrial tissue. We found that fifteen out of seventeen RTKs evaluated in this study were highly expressed (P < 0.02-0.03) in the leiomyomas, and included the IGF-I/IGF-IR, EGF/EGFR, FGF/FGF-R, HGF/HGF-R, and PDGF/PDGF-R gene families. Due to the higher protein levels of IGF-IR observed in leiomyomas by us in earlier studies, we decided to focus on the activation of the IGF-IR, its downstream effectors, and MAPKp44/42 to confirm our earlier findings; and validate the significance of the increased IGF-IR phosphorylation observed by RTK array analysis in this study. We used immunolocalization, western blot, or immunoprecipitation studies and confirmed that leiomyomas overexpressed IGF-IRbeta and phosphorylated IGF-IRbeta. Additionally, we showed that the downstream effectors, Shc, Grb2, and MAPKp44/42 (P < 0.02-0.001) were also overexpressed and involved in IGF-IR signaling in these tumors, while IRS-I, PI3K, and AKT were not. In vitro studies showed that IGF-I (100 ng/mL) increased the proliferation of uterine leiomyoma cells (UtLM) (P < 0.0001), and that phosphorylated IGF-IRbeta, Shc, and MAPKp44/42 were also overexpressed in IGF-I-treated UtLM cells (P < 0.05), similar to the tissue findings. A neutralizing antibody against the IGF-IRbeta blocked these effects. These data indicate that overexpression of RTKs and, in particular, activation of the IGF-IR signaling pathway through Shc/Grb2/MAPK are important in mediating uterine leiomyoma growth. These data may provide new anti-tumor targets for noninvasive treatment of fibroids.
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PMID:Differential expression of receptor tyrosine kinases (RTKs) and IGF-I pathway activation in human uterine leiomyomas. 1823 72

Metastatic cancer is a complex positive feedback loop system. Such as system has a tendency to acquire extreme robustness. Signaling pathways controlling that robustness can fail completely if an essential element from the signaling is removed. That element is a locus of fragility. Targeting that locus represents the best way to target the cancer robustness. This prospect presents another locus of fragility in signaling complex system network, controlling the cell cycle progression through the PI3K/AKT/mTOR/RAN pathway and cell migration and angiogenesis through the VEGF/PI3K/AKT/NO/ICAM-1 pathway. The locus of fragility of these pathways is AKT, which is regulated by a balance of catalase/H2O2 or by AKT inhibitor. Tiny and trivial perturbations such as change in redox state in the cells by antioxidant enzyme catalase, scavenging H2O2 signaling molecule, regulates robust signaling molecule AKT, abolishing its phosporilation and inducing cascading failure of robust signaling pathways for cell growth, proliferation, migration, and angiogenesis. An anticancer effect of the antioxidant is achieved through the AKT locus, by abolishing signals from growth factors VEGF, HGF, HIF-1alpha and H2O2. Previously reported locus of fragility nitric oxide (NO) and locus AKT are close in the complex signaling interactome network, but they regulate distinct signaling modules. Simultaneously targeted loci represents new principles in cancer robustness chemotherapy by blocking cell proliferation, migration, angiogenesis and inducing rather slow then fast apoptosis leading to slow eradication of cancer.
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PMID:AKT as locus of fragility in robust cancer system. 1842 70

The HGF/Met signaling pathway is deregulated in majority of cancers and is associated with poor prognosis in breast cancer. Delphinidin, present in pigmented fruits and vegetables possesses potent anti-oxidant, anti-inflammatory and anti-angiogenic properties. Here, we assessed the anti-proliferative and anti-invasive effects of delphinidin on HGF-mediated responses in the immortalized MCF-10A breast cell line. Treatment of cells with delphinidin prior to exposure to exogenous HGF resulted in the inhibition of HGF-mediated (i) tyrosyl-phosphorylation and increased expression of Met receptor, (ii) phosphorylation of downstream regulators such as FAK and Src and (iii) induction of adaptor proteins including paxillin, Gab-1 and GRB-2. In addition, delphinidin treatment resulted in significant inhibition of HGF-activated (i) Ras-ERK MAPKs and (ii) PI3K/AKT/mTOR/p70S6K pathways. Delphinidin was found to repress HGF-activated NFkappaB transcription with a decrease in (i) phosphorylation of IKKalpha/beta and IkappaBalpha, and (ii) activation and nuclear translocation of NFkappaB/p65. Inhibition of HGF-mediated membrane translocation of PKCalpha as well as decreased phosphorylation of STAT3 was further observed in delphinidin treated cells. Finally, decreased cell viability of Met receptor expressing breast cancer cells treated with delphinidin argues for a potential role of the agent in the prevention of HGF-mediated activation of various signaling pathways implicated in breast cancer.
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PMID:Delphinidin inhibits cell proliferation and invasion via modulation of Met receptor phosphorylation. 1849 6

Recurrent/metastatic head and neck cancer remains a devastating disease with insufficient treatment options. We investigated the MET receptor tyrosine kinase as a novel target for the treatment of head and neck squamous cell carcinoma (HNSCC). MET/phosphorylated MET and HGF expression was analyzed in 121 tissues (HNSCC/normal) by immunohistochemistry, and in 20 HNSCC cell lines by immunoblotting. The effects of MET inhibition using small interfering RNA/two small-molecule inhibitors (SU11274/PF-2341066) on signaling, migration, viability, and angiogenesis were determined. The complete MET gene was sequenced in 66 head and neck cancer tissue samples and eight cell lines. MET gene copy number was determined in 14 cell lines and 23 tumor tissues. Drug combinations of SU11274 with cisplatin or erlotinib were tested in SCC35/HN5 cell lines. Eighty-four percent of the HNSCC samples showed MET overexpression, whereas 18 of 20 HNSCC cell lines (90%) expressed MET. HGF overexpression was present in 45% of HNSCC. MET inhibition with SU11274/PF-2341066 abrogated MET signaling, cell viability, motility/migration in vitro, and tumor angiogenesis in vivo. Mutational analysis of 66 tumor tissues and 8 cell lines identified novel mutations in the semaphorin (T230M/E168D/N375S), juxtamembrane (T1010I/R988C), and tyrosine kinase (T1275I/V1333I) domains (incidence: 13.5%). Increased MET gene copy number was present with >10 copies in 3 of 23 (13%) tumor tissues. A greater-than-additive inhibition of cell growth was observed when combining a MET inhibitor with cisplatin or erlotinib and synergy may be mediated via erbB3/AKT signaling. MET is functionally important in HNSCC with prominent overexpression, increased gene copy number, and mutations. MET inhibition abrogated MET functions, including proliferation, migration/motility, and angiogenesis. MET is a promising, novel target for HNSCC and combination approaches with cisplatin or EGFR inhibitors should be explored.
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PMID:The MET receptor tyrosine kinase is a potential novel therapeutic target for head and neck squamous cell carcinoma. 1931 76


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