Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The tyrosine kinase receptor c-Met and its ligand HGF/SF, ezrin, and splice variants of CD44 have independently been identified as tumor metastasis-associated proteins. We now show that these proteins cooperate. A CD44 isoform containing variant exon v6 sequences is strictly required for c-Met activation by HGF/SF in rat and human carcinoma cells, in established cell lines as well as in primary keratinocytes. CD44v6-deficient tumor cells were unable to activate c-Met unless they were transfected with a CD44v6-bearing isoform. Antibodies to two v6-encoded epitopes inhibited autophosphorylation of c-Met by interfering with the formation of a complex formed by c-Met, CD44v6, and HGF/SF. In addition, signal transduction from activated c-Met to MEK and Erk required the presence of the cytoplasmic tail of CD44 including a binding motif for ERM proteins. This suggests a role for ERM proteins and possibly their link to the cortical actin cytoskeleton in signal transfer.
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PMID:CD44 is required for two consecutive steps in HGF/c-Met signaling. 1246 36

Air-liquid interface (ALI) is a microenvironment of aerodigestive tract. In our previous study, ALI promoted invasive growth of laryngeal squamous cell carcinoma (SCC); but its mechanism was unclear. Hypoxia is also related to cancer spread. Here we show that ALI with or without hypoxia accelerated invasive growth of laryngeal SCC cells, using collagen gel invasion assay. Submerged condition (SMC) without ALI did not induce the invasion with or without hypoxia. ALI enhanced expression of the following growth-, invasion-, and motility-related molecules in the cells with or without hypoxia more greatly than SMC: c-Met, Ras, mitogen-activated protein kinase cascade proteins (Raf-1, MEK-1, and ERK-1/2), matrix metalloproteinase-1, and filamin A. The data indicate that ALI promotes invasive growth of SCC cells by enhancement of the invasive growth-related molecules above, through mechanisms that differ from hypoxia, suggesting that ALI microenvironment should be taken into account for the study of cancer biology.
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PMID:Air-liquid interface promotes invasive growth of laryngeal squamous cell carcinoma with or without hypoxia. 1560 49

Biological responses of hepatocyte growth factor (HGF) are mediated by the Met receptor tyrosine kinase. Although HGF is a potent mitogen for a variety of cells, the signals required for cell-cycle progression by the Met/HGF receptor are poorly defined. In this study, we have used the Xenopus oocyte system to define the role of various Met proximal-binding partners and downstream signaling pathways in cell-cycle regulation. We show that cell-cycle progression and activation of MAPK and JNK mediated by the oncogenic Met receptor, Tpr-Met, are dependent on its kinase activity and the presence of the twin phosphotyrosine (Y482 & Y489) residues in its C-terminus, but that the recruitment of Grb2 and Shc adaptor proteins is dispensable, implicating other signaling molecules. However, using Met receptor oncoproteins engineered to recruit specific signaling proteins, we demonstrate that recruitment of Grb2 or Shc adaptor proteins is sufficient to induce cell-cycle progression and activation of MAPK and JNK, while the binding of phospholipase-Cgamma or phosphatidylinositol 3-kinase alone fails to elicit these responses. Using various means to block phosphatidylinositol 3-kinase, phospholipase-Cgamma, MEK, JNK, Mos, and Raf1 activity, we show that unlike the fibroblast growth factor receptor, MEK-dependent and independent signaling contribute to Met receptor-mediated cell-cycle progression, but phospholipase-Cgamma or JNK activity and Mos synthesis are not critical. Notably, we demonstrate that Raf1 and phosphatidylinositol 3-kinase signaling are required for cell-cycle progression initiated by the Met receptor, a protein frequently deregulated in human tumors.
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PMID:Oncogenic Met receptor induces cell-cycle progression in Xenopus oocytes independent of direct Grb2 and Shc binding or Mos synthesis, but requires phosphatidylinositol 3-kinase and Raf signaling. 1633 88

Hepatocyte growth factor (HGF), also known as scatter factor (SF), and its receptor, the c-Met tyrosine kinase, play roles in cancer invasion and metastasis in a wide variety of tumor cells. Clinical observations suggest that HGF can promote metastasis of hepatoma cells while stimulating tumor invasiveness. We use HGF as an invasive inducer of human hepatoma HepG2 cells to investigate the effect of flavonoids on anti-invasion. In our preliminary study, we investigated the effect of flavonoids including luteolin, quercetin, baicalein, genistein, taxifolin and catechin on HGF-mediated migration and invasion of HepG2 cells. We found that luteolin presented the most potent potential on anti-migration and anti-invasion by Boyden chamber assay. Furthermore, luteolin inhibited HGF-induced cell scattering and cytoskeleton change such as filopodia and lamellipodia was determined by both phase-contrast and fluorescence microscopy studies. In addition, Western blotting and immunoprecipitation were performed to confirm luteolin suppressed the phosphorylation of c-Met, the membrane receptor of HGF, as well as ERK1/2 and Akt, but not JNK1/2, which is activated by HGF. Our investigation demonstrated that luteolin similar to PD98059, which acts as a specific inhibitor of MEK, an up stream kinase regulating ERK1/2, and wortmannin, a PI3K inhibitor, inhibited the invasiveness induced by HGF. In conclusion, the luteolin inhibited HGF-induced HepG2 cell invasion involving both MAPK/ERKs and PI3K-Akt pathways.
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PMID:Inhibitory effect of luteolin on hepatocyte growth factor/scatter factor-induced HepG2 cell invasion involving both MAPK/ERKs and PI3K-Akt pathways. 1645 70

The regulatory mechanisms for the proliferation and the particular invasive phenotypes of stomach cancers are not still fully understood. Up-regulations of hepatocytes growth factor (HGF), its receptor (c-Met), and urokinase-type plasminogen activator (uPA) are correlated with the development and metastasis of cancers. In order to investigate roles of HGF/c-Met signaling in tumor progression and metastasis in stomach cancers, we determined effects of a specific MEK1 inhibitor (PD098059) and a p38 kinase inhibitor (SB203580) on HGF-mediated cell proliferation and uPA expression in stomach cancer cell lines (NUGC-3 and MKN-28). HGF treatment induced the phosphorylations of ERK and p38 kinase in time- and dose- dependent manners. Pre-treatment with PD098059 reduced HGF-mediated cell proliferation and uPA secretion. In contrast, SB203580 pre-treatment enhanced cell proliferation and uPA secretion due to induction of ERK phosphorylation. Stable expression of dominant negative-MEK1 in NUGC-3 cells showed a decrease in HGF-mediated uPA secretion. These results suggest that interaction of a MEK/ERK and a p38 kinase might play an important role in proliferation and invasiveness of stomach cancer cells.
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PMID:Regulation of hepatocyte growth factor-mediated urokinase plasminogen activator secretion by MEK/ERK activation in human stomach cancer cell lines. 1652 May 50

Growth factors accelerate G0 to S progression in the cell cycle, however, the roles of growth factors in other cell cycle phases are largely unknown. Here, we show that treatment of HeLa cells with hepatocyte growth factor (HGF) at G2 phase induced the G2/M transition delay as evidenced by FACS analysis as well as by mitotic index and time-lapse analyses. Growth factors such as epidermal growth factor (EGF) and fibroblast growth factor (FGF) also induced G2/M transition delay like HGF. HGF treatment at G2 phase causes a delayed activation of cyclin B1-associated kinase and a diminished nuclear translocation of cyclin B1. Either U0126, a MAPK kinase (MEK) inhibitor, or kinase-dead mutant of ribosomal S6 kinase (RSK) abolished the delay. Additionally, knockdown of RSK1, but not RSK2, with siRNA abrogated the delay, indicating that the extracellular-regulated protein kinase (ERK)-RSK1 mediates the HGF-induced delay. We further found that the delay in G2/M transition of cells expressing oncogenic HGF receptor, M1268T, was abolished by RSK1 knockdown. Intriguingly, we observed that HGF induced chromosomal segregation defects, and depletion of RSK1, but not RSK2, aggravated these chromosomal aberrations. Taken together, the ERK-RSK1 activation by growth factors delays G2/M transition and this might be required to maintain genomic integrity during growth factor stimulation.
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PMID:The ERK-RSK1 activation by growth factors at G2 phase delays cell cycle progression and reduces mitotic aberrations. 1845 Apr 23

It is well recognized that the majority of cancer related deaths is caused by metastatic diseases. Therefore, there is an urgent need for the development of therapeutic intervention specifically targeted to the metastatic process. In the last decade, significant progress has been made in this research field, and many new concepts have emerged that shed light on the molecular mechanism of metastasis cascade which is often portrayed as a succession of six distinct steps; localized invasion, intravasation, translocation, extravasation, micrometastasis and colonization. Successful metastasis is dependent on the balance and complex interplay of both the metastasis promoters and suppressors in each step. Therefore, the basic strategy of our interventions is aimed at either blocking the promoters or potentiating the suppressors in this disease process. Toward this goal, various kinds of antibodies and small molecules have been designed. These include agents that block the ligand-recepter interaction of metastasis promoters (HGF/c-Met), antagonize the metastasis-promoting enzymes (AMF, uPA and MMP) and inhibit the transcriptional activity of metastasis promoter (beta-Catenin). On the other hand, the intriguing roles of metastasis suppressors and their signal pathways have been extensively studied and various attempts have been made to potentiate these factors. Small molecules have been developed to restore the expression or mimic the function of metastasis-suppressor genes such as NM23, E-cadherin, Kiss-1, MKK4 and NDRG1, and some of them are under clinical trials. This review summarizes our current understanding of the molecular pathway of tumor metastasis and discusses strategies and recent development of anti-metastatic drugs.
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PMID:Drug development against metastasis-related genes and their pathways: a rationale for cancer therapy. 1869 17

We previously described the novel zinc finger protein ZKSCAN3 as a new "driver" of colon cancer progression. To investigate the underlying mechanism and because the predicted structural features (tandem zinc fingers) are often present in transcription factors, we hypothesized that ZKSCAN3 regulates the expression of a gene(s) favoring tumor progression. We employed unbiased screening to identify a DNA binding motif and candidate downstream genes. Cyclic amplification and selection of targets using a random oligonucleotide library and ZKSCAN3 protein identified KRDGGG as the DNA recognition motif. In expression profiling, 204 genes were induced 2-29-fold, and 76 genes reduced 2-5-fold by ZKSCAN3. To enrich for direct targets, we eliminated genes under-represented (<3) for the ZKSCAN3 binding motif (identified by CAST-ing) in 2 kilobases of regulatory sequence. Up-regulated putative downstream targets included genes contributing to growth (c-Met-related tyrosine kinase (MST1R), MEK2; the guanine nucleotide exchanger RasGRP2, insulin-like growth factor-2, integrin beta 4), cell migration (MST1R), angiogenesis (vascular endothelial growth factor), and proteolysis (MMP26; cathepsin D; PRSS3 (protease serine 3)). We pursued integrin beta 4 (induced up to 6-fold) as a candidate target because it promotes breast cancer tumorigenicity and stimulates phosphatidyl 3-kinase implicated in colorectal cancer progression. ZKSCAN3 overexpression/silencing modulated integrin beta 4 expression, confirming the array analysis. Moreover, ZKSCAN3 bound to the integrin beta 4 promoter in vitro and in vivo, and the integrin beta 4-derived ZKSCAN3 motif fused upstream of a tk-Luc reporter conferred ZKSCAN3 sensitivity. Integrin beta 4 knockdown by short hairpin RNA countered ZKSCAN3-augmented anchorage-independent colony formation. We also demonstrate vascular endothelial growth factor as a direct ZKSCAN3 target. Thus, ZKSCAN3 regulates the expression of several genes favoring tumor progression including integrin beta 4.
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PMID:Unbiased screening for transcriptional targets of ZKSCAN3 identifies integrin beta 4 and vascular endothelial growth factor as downstream targets. 1894 Aug 3

The irradiated fibroblast-induced response of non-irradiated neighboring cells is called 'radiation-induced bystander effect', but it is unclear in non-irradiated human squamous cell carcinoma (SCC) cells. The present study shows that irradiated fibroblasts promoted the invasive growth of T3M-1 SCC cells, but not their apoptosis, more greatly than non-irradiated fibroblasts, using collagen gel invasion assay, immunohistochemistry and Western blot. The number of irradiated fibroblasts decreased to about 30% of that of non-irradiated fibroblasts, but irradiated fibroblasts increased the growth marker ki-67 display of SCC cells more greatly than non-irradiated fibroblasts. Irradiated fibroblasts did not affect the apoptosis marker ss-DNA expression of SCC cells. Irradiated fibroblasts enhanced the display of the following growth-, invasion- and motility-related molecules in SCC cells more greatly than non-irradiated fibroblasts: c-Met, Ras, mitogen-activated protein kinase (MAPK) cascade (Raf-1, MEK-1 and ERK-1/2), matrix metalloproteinase-1 and -9, laminin 5 and filamin A. Irradiated fibroblasts, but not non-irradiated ones, formed irradiation-induced foci (IRIF) of the genomic instability marker p53-binding protein 1 (53BP1) and expressed transforming growth factor-beta1 (TGF- beta1). Irradiated fibroblasts in turn enabled SCC cells to enhance 53BP1 IRIF formation more extensively than non-irradiated fibroblasts. Finally, effects of irradiated fibroblasts on growth and apoptosis of another HEp-2 SCC cell type were similar to those of T3M-1. These results suggest that irradiated fibroblasts promotes invasion and growth of SCC cells by enhancement of invasive growth-related molecules above through TGF- beta1-mediated bystander mechanism, in which irradiated fibroblast-induced genomic instability of SCC cells may be involved.
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PMID:Irradiated fibroblast-induced bystander effects on invasive growth of squamous cell carcinoma under cancer-stromal cell interaction. 1901 71

Scatter factor (SF) (hepatocyte growth factor) is a pleiotrophic cytokine that accumulates in tumors, where it may induce invasion, angiogenesis, and chemoresistance. We have studied the mechanisms by which SF and its receptor (c-Met) protect cells against the DNA-damaging agent adriamycin (ADR) as a model for chemoresistance of SF/c-Met-overexpressing tumors. Previous studies identified a phosphatidylinositol 3-kinase/c-Akt/Pak1/NF-kappaB cell survival pathway in DU-145 prostate cancer and Madin-Darby canine kidney epithelial cells. Here we studied Src signaling pathways involved in SF cell protection. Src enhanced basal and SF stimulated NF-kappaB activity and SF protection against ADR, in a manner dependent upon its kinase and Src homology 3 domains; and endogenous Src was required for SF stimulation of NF-kappaB activity and cell protection. The ability of Src to enhance SF stimulation of NF-kappaB activity was due, in part, to its ability to stimulate Akt and IkappaB kinase activity; and Src-mediated stimulation of NF-kappaB was due, in part, to a Rac1/MKK3/6/p38 pathway and was Akt-dependent. SF caused the activation of Src and the Rac1 effector Pak1. Furthermore, SF induced activating phosphorylations of MKK3, MKK6, and p38 within the c-Met signalsome in an Src-dependent manner. The NF-kappaB-inducing kinase was found to act downstream of TAK1 (transforming growth factor-beta-activated kinase 1) as a mediator of SF- and Src-stimulated NF-kappaB activity. Finally, the Src/Rac1/MKK3/6/p38 and Src/TAK1/NF-kappaB-inducing kinase pathways exhibited cross-talk at the level of MKK3. These findings delineate some novel signaling pathways for SF-mediated resistance to ADR.
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PMID:Role of Src signal transduction pathways in scatter factor-mediated cellular protection. 1904 46


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