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

---

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

Lovastatin inhibits 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase the rate limiting enzyme for synthesis of mevalonic acid, a precursor for cholesterol, farnesyl and geranylgeranyl pyrophosphate isoprenoids. Recent studies suggest it also has growth inhibitory properties. Posttranslational farnesyl or geranylgeranylation of low molecular weight GTP-binding proteins such as RAS and RHO are thought to be an essential step in activation of phosphorylation cascades such as the RAS-RAF-1-MEK-1-MAPK/ERK pathway which stimulate cell proliferation. In this study, we evaluated lovastatin effects on meningioma cell proliferation and activation of the MEK-1-MAPK/ERK pathway. The effect of lovastatin on cell proliferation was assessed in eight human meningioma cell cultures stimulated by platelet derived growth factor (PDGF)-BB, cerebrospinal fluid (CSF), and fetal bovine serum (FBS). Concomitant lovastatin effects on phosphorylation/activation of mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) kinase (MEK-1) and MAPK/ERK were assessed by Western blot. Whether lovastatin acts via a mevalonate-dependent mechanism was also evaluated. Coadministration of lovastatin completely blocked PDGF-BB, CSF, and FBS stimulation of [3H]-thymidine incorporation and cell proliferation. Lovastatin inhibited PDGF-BB's stimulatory effect in a dose dependent manner. Concomitant with its growth inhibitory effects, lovastatin reduced phosphorylation/activation of MEK-1/2 in five meningiomas and MAPK/ERK in seven. Coadministration of mevalonate with lovastatin partially restored PDGF's mitogenic effect. Lovastatin is a potent inhibitor of meningioma cell proliferation which may act in part by reducing activation of MEK-1-MAPK/ERK pathway. Additional studies are warranted to assess whether lovastatin and similar HMG-CoA reductase inhibitors represent a new adjunctive chemotherapy for recurrent meningiomas.
...
PMID:Lovastatin is a potent inhibitor of meningioma cell proliferation: evidence for inhibition of a mitogen associated protein kinase. 1199 14

The role of transforming growth factor-beta (TGF-beta) in regulation of meningioma growth and intracellular events transducing its signals are not established. In this study, we evaluated the effects of TGF-beta1 on basal meningioma cell proliferation in 10 primary human meningioma cell cultures and whether TGF-beta's signals are transduced by the Smad 2/3, MAPK/Erk kinase-1 (MEK-1)-mitogen-activated protein kinase (MAPK), Akt-p70(S6K) or p38-JUNK pathways in 5. We also tested whether neutralizing antibodies to TGF-beta alter CSF stimulation of meningioma cell proliferation. On average, TGF-beta reduced meningioma cell [3H]-thymidine incorporation to 58% of controls at 24% and to 61% of controls at 36 h. TGF-beta inhibition of meningioma cell proliferation was associated with a suggestion increased phosphorylation of Smad 2/3 in 2 cases and high basal phosphorylation in 3 but no change in activation of the MEK-1-MAPK, Akt-p70(S6K) or p38-JUNK pathways. As shown previously, CSF stimulated meningioma cell proliferation in the 3 cultures tested. Neutralizing antibody against TGF-beta augmented this stimulation in 2 of 3 cultures. These findings suggest that TGF-beta exerts a largely inhibitory effect on basal meningioma proliferation, perhaps in part through Smad 2/3.
...
PMID:Transforming growth factor-beta effects on meningioma cell proliferation and signal transduction pathways. 1501 65

The roles of growth factor receptors and numerous downstream growth regulatory pathways are of increasing interest in neuro-oncology. These pathways have been extensively studied in gliomas but only recently analyzed in meningiomas. This article reviews current research on the growth factor receptor-Ras-Raf-1-MEK-1-MAPK, PI3K-Akt/PKB, PLC-gamma1-PKC, phospholipase A2-cyclooxygenase, and TGF-beta receptor-Smad pathways that appear to regulate meningioma growth and inhibit apoptosis. Sites along these receptor/kinase cascades that might be targeted by novel therapies are also discussed.
...
PMID:Mitogenic signal transduction pathways in meningiomas: novel targets for meningioma chemotherapy? 1631 13

Chemokines participate in cellular processes associated with tumor proliferation, migration, and angiogenesis. We previously demonstrated that stromal cell-derived factor 1 (SDF1) exerts a mitogenic activity in glioblastomas through the activation of its receptor CXCR4. Here we studied the expression of this chemokine in human meningiomas and its possible role in cell proliferation. Reverse transcriptase-PCR analysis for CXCR4 and SDF1 was performed on 55 human meningiomas (47 WHO grade I, 5 WHO II, and 3 WHO III). Immunolabeling for CXCR4 and SDF1 was performed on paraffin-embedded sections of these tumors. [(3)H]Thymidine uptake and Western blot analyses were performed on primary meningeal cell cultures of tumors to evaluate the proliferative activity of human SDF1alpha (hSDF1alpha) in vitro and the involvement of extracellular signal-regulated kinase 1/2 (ERK1/2) activation in this process. CXCR4 mRNA was expressed by 78% of the tumor specimens and SDF1 mRNA by 53%. CXCR4 and SDF1 were often detected in the same tumor tissues and colocalized with epithelial membrane antigen immunostaining. In 9 of 12 primary cultures from meningiomas, hSDF1alpha induced significant cell proliferation that was strongly reduced by the mitogen-activated protein kinase kinase inhibitor PD98059, involving ERK1/2 activation in the proliferative signal of hSDF1alpha. In fact, CXCR4 stimulation led to ERK1/2 phosphorylation/activation. In addition, the hSDF1alpha-induced cell proliferation was significantly correlated with the MIB1 staining index in the corresponding surgical specimen. In conclusion, we found that human meningiomas express CXCR4 and SDF1 and that hSDF1alpha induces proliferation in primary meningioma cell cultures through the activation of ERK1/2.
...
PMID:CXCR4 and SDF1 expression in human meningiomas: a proliferative role in tumoral meningothelial cells in vitro. 1710 64

Recent evidence indicates that cancer cells express chemokine (CK) receptors and that their signaling is crucial for tumor proliferation, migration, and angiogenesis. The profiles of expression of CXC CK receptors (CXCR1-5) and their main ligands (growth-related oncogene, GRO1-2-3/CXCL1-2-3; interleukin 8, IL-8/CXCL8; monokine-induced gamma-interferon MIG/CXCL9; gamma-interferon-inducible-protein-10, IP-10/CXCL10; stromal cell-derived factor-1, SDF1/CXCL12; B-cell activating CK-1, BCA-1/CXCL13) were analyzed by reverse transcription polymerase chain reaction (RT-PCR) in surgical samples of human meningiomas. All the five receptors displayed high percentages of positive cases: 92% CXCR1, 89% CXCR2, 83% CXCR3, 78% CXCR4, and 94% CXCR5. Conversely, their ligands showed a lower pattern of expression: 40% IL-8, 42% GRO1-3, 42% IP-10, 28% MIG, 53% SDF1, and 3% BCA-1. SDF1/CXCR4 interaction plays a pivotal role in cancer proliferation. Thus, the signaling mechanisms activated by the exclusive binding between SDF1 and CXCR4 was investigated in 12 primary cultures from meningioma tissues. CXCR4 was functionally coupled as demonstrated by the significant increase of DNA synthesis in meningioma cells in response to SDF1, measured by [3H]-thymidine uptake. In three primary cultures, the SDF1-dependent mitogenic activity was associated with a marked phosphorylation of extracellular signal-regulated kinase (ERK1/2) as evaluated by Western blots. PD98059 (a MEK inhibitor) significantly reduced ERK1/2 activation, thus linking the SDF1/CXCR4 pathway to meningioma cell proliferation via ERK1/2 signal transduction. We demonstrate, for the first time in human meningiomas, the simultaneous expression of CXCR1-5 and their CKs and the mitogenic activity of SDF1/CXCR4, suggesting a pivotal role of these receptor-ligand pairs in meningeal tumors.
...
PMID:CXC receptor and chemokine expression in human meningioma: SDF1/CXCR4 signaling activates ERK1/2 and stimulates meningioma cell proliferation. 1738 78

Meningioma is a well-known tumor of the central nervous system, and is treated by surgical resection and/or radiation. Recently, ionizing radiation has been shown to enhance invasiveness of surviving tumor cells, and several proteolytic enzyme molecules, including urokinase plasminogen activator (uPA), seem to be upregulated after radiation. uPA and its receptor (uPAR) have been strongly implicated in tumor invasion, angiogenesis and progression. Hence, the tumor-associated uPA-uPAR system is considered a potential target for cancer therapy. In the present study, we show that radiation increases uPA levels in the IOMM-Lee meningioma cells, and subsequently, increases tumor invasion, migration and angiogenesis in vitro. Studies with signaling molecule inhibitors AG1478, U0126 and SB203580 (specific inhibitors of EGFR, MEK1/2 and p38 respectively) showed inhibition of uPA levels in both basal and irradiated-IOMM-Lee cells. The PI3K inhibitor (LY294002) and the AKT inhibitor (AKT inhibitor IV) also partially decreased uPA expression, whereas SP600125, a JNK inhibitor, did not affect uPA levels in either radiated or non-radiated cells. Further, a bicistronic plasmid construct with small interfering RNA (siRNA) against uPA and its receptor inhibited tumor invasion, migration and angiogenesis in radiation-treated IOMM-Lee cells. In addition, siRNA against uPA and its receptor inhibited subcutaneous tumor growth in athymic nude mice in combination with radiation in a synergistic manner. Thus, the specific targeting of proteases via RNA interference could augment the therapeutic effect of radiation and prevent the adverse effects resulting from tumor cells that receive sublethal doses of radiation within the tumor mass.
...
PMID:uPA/uPAR downregulation inhibits radiation-induced migration, invasion and angiogenesis in IOMM-Lee meningioma cells and decreases tumor growth in vivo. 1894 56

Both genetic and epigenetic mechanisms contribute to meningioma development by altering gene expression and protein function. To determine the relative contribution of each mechanism to meningioma development, we used an integrative approach measuring copy number and DNA methylation changes genomewide. We found that genetic alterations affected 1.9%, 7.4%, and 13.3% of the 691 loci studied, whereas epigenetic mechanisms affected 5.4%, 9.9%, and 10.3% of these loci in grade I, II, and III meningiomas, respectively. Genetic and epigenetic mechanisms rarely involved the same locus in any given tumor. The predilection for epigenetic rather than genetic silencing was exemplified at the 5' CpG island of WNK2, a serine-threonine kinase gene on chromosome 9q22.31. WNK2 is known to negatively regulate epidermal growth factor receptor signaling via inhibition of MEK1 (mitogen-activated protein kinase kinase 1), and point mutations have been reported in WNK1, WNK2, WNK3, and WNK4. In meningiomas, WNK2 was aberrantly methylated in 83% and 71% of grade II and III meningiomas, respectively, but rarely in a total of 209 tumors from 13 other tumor types. Aberrant methylation of the CpG island was associated with decreased expression in primary tumors. WNK2 could be reactivated with a methylation inhibitor in IOMM-Lee, a meningioma cell line with a densely methylated WNK2 CpG island and lack of WNK2 expression. Expression of exogenous WNK2 inhibited colony formation, implicating it as a potential cell growth suppressor. These findings indicate that epigenetic mechanisms are common across meningiomas of all grades and that for specific genes such as WNK2, epigenetic alteration may be the dominant, grade-specific mechanism of gene inactivation.
...
PMID:Epigenetic silencing of the kinase tumor suppressor WNK2 is tumor-type and tumor-grade specific. 1900 26

The intracellular events promoting meningioma cell proliferation in high grade tumors are not established. In this study we compared 45 WHO grade I and 35 grade II or III meningiomas by Western blot or immunohistochemistry for phosphorylation/activation of the MEK-1-MAPK, PI3 K-Akt-mTOR-PRAS40 and STAT3 pathways. By Western blot, STAT3 activation was detected in 75% of grade I compared to 100% of grade II and III meningiomas. By immunohistochemistry p-STAT3 was detected in 28% of grade I compared to 65 or 66% of grade II and III meningiomas, respectively. Phosphorylated MEK-1 and p-MAPK were activated in nearly all grade I, II and III tumors. Phosphorylated Akt was also detected in the majority of meningiomas of each grade although downstream pathway component activation was less widespread. These findings suggest that there is increased STAT3 activation in WHO grade II and III meningiomas compared with grade I tumors. Moreover, each of the three major growth regulatory pathways is concomitantly activated in higher grade meningiomas.
...
PMID:Increased STAT-3 and synchronous activation of Raf-1-MEK-1-MAPK, and phosphatidylinositol 3-Kinase-Akt-mTOR pathways in atypical and anaplastic meningiomas. 1903 85

Recent studies suggest that HIV-1 protease inhibitors may have anti-neoplastic effects on some malignancies. The anti-neoplastic effects of lopinavir have not been established or studied in brain tumors. Primary cultures of three fetal leptomeninges and 18 meningiomas were treated with lopinavir alone or with PDGF-BB. DNA synthesis was assessed by CyQUANT. Lopinavir effects on basal and PDGF-stimulated phosphorylation of the Akt-mTOR, MEK1/2-MAPK and STAT3 pathways, phosphorylation of Rb, Caspase 3 activation and reductions in survivin were assessed by Western blots. Lopinavir produced a significant reduction in PDGF-BB stimulation of DNA synthesis in a leptomeningeal culture (P = 0.0013) and 1 of 6 WHO grade I and 1 of 4 grade II meningiomas at 24 h and in 3 of 6 WHO grade I, 4 of 4 grade II and 1 of 1 grade III cell cultures (P = 0.0001) at 72 h. Lopinavir reduced PDGF-BB stimulation of phosphorylation/activation of MAPK in the 22 week fetal leptomeningeal cell cultures and in cells from 1 grade I meningioma at 24 h, but in none of 4 grade I and 5 grade II meningiomas at 6 h. Lopinavir had no notable effect on basal or PDGF-stimulated p-mTOR, p-MEK1/2, or p-STAT3, activation of Caspase 3 or survivin levels. Lopinavir treatment for 24 h had no effect on basal Rb phosphorylation but reduced Rb phosphorylation in all four meningioma cultures. These studies suggest that lopinavir may inhibit meningioma growth, and does so in part by cell cycle arrest. Additional evaluation of lopinavir as a potential adjunct chemotherapy is warranted.
...
PMID:Lopinavir inhibits meningioma cell proliferation by Akt independent mechanism. 2059 51

The role of cerebrospinal fluid (CSF) in the pathogenesis of meningiomas is unknown. Cell cultures from three human leptomeninges, five WHO grade I and seven grade II meningiomas were treated with remnant CSF from 22 patients with no central nervous system disease and normal cell indices. Cells were evaluated by CyQUANT for DNA synthesis/cell proliferation and by western blots for phosphorylation/activation of growth regulatory pathways activated in meningiomas including JAK1-STAT3, MEK1-p44/42MAPK, Akt-mTOR and Rb. Analysis of Caspase 3 activation and survivin was also performed. Finally, the effects of PDGF neutralizing antibody and cucurbitacin, a STAT3 inhibitor on CSF stimulation were tested. Compared to controls and the mitogen PDGF-BB, various CSF samples significantly stimulated DNA synthesis/cell proliferation in 20 and 22 week leptomeningeal cultures and all of the grade I and II meningioma cells tested. Collectively CSF samples, from multiple different patients, stimulated DNA synthesis in tests of 23 of 32 grade I and 18 of 28 grade II meningioma cells. CSF stimulated phosphorylation/activation of STAT3 and reduced p44/42 MAPK in the leptomeningeal, all three grade I and 1 of three grade II meningioma cells. CSF did not affect Caspase 3 activity or survivin levels. PDGF neutralizing antibody had no effect on CSF stimulation but cucurbitacin blocked PDGF and CSF stimulation. While there are limitations to the CSF available since they were not from "normal" volunteers, the studies suggest that, in some settings, CSF is potentially mitogenic to leptomeningeal and meningioma cells and may act, in part, via activation of STAT3.
...
PMID:Cerebrospinal fluid stimulates leptomeningeal and meningioma cell proliferation and activation of STAT3. 2197 37


1 2 Next >>

---