Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

MAPK signaling is required for retinoic acid (RA)-triggered G(0) cell cycle arrest and cell differentiation, but the mechanism is not well defined. In this study, RA is found to cause MAPK activation with sustained association of RAF to MEK or ERK, leading to a MAPK-dependent accumulation of p21(Waf1/Cip1) and binding to CDK2 blocking G(1)/S transition. BLR1, a chemokine receptor, was found to function as a critical component of RA-triggered MAPK signaling. Unlike wild-type parental cells, RA-treated BLR1 knock-out cells failed to show RAF and consequential MEK and ERK phosphorylation, failed to accumulate CDK inhibitors that control G(1)/S transition, and failed to differentiate and arrest in response to RA, whereas ectopically overexpressing BLR1 enhanced MAPK signaling and caused accelerated RA-induced differentiation and arrest. Ectopic overexpression of RAF enhanced BLR1 expression in response to RA, whereas inhibition of RAF or MEK by inhibitors or knockdown of RAF by short interfering RNA diminished RA-induced BLR1 expression and attenuated differentiation and growth arrest. Ectopic expression of the RAF CR3, the catalytically active domain, in the BLR1 knock-out restored RA-induced MAPK activation and the ability to differentiate and arrest, indicating that RAF effects MAPK signaling by BLR1 to propel differentiation/arrest. Taken together, RA induces cell differentiation and growth arrest through activation of a novel MAPK pathway with BLR1 as a critical component in a positive feedback mechanism that may contribute to the prolonged MAPK signaling propelling RA-induced cell cycle arrest and differentiation.
 ...
PMID:A MAPK-positive feedback mechanism for BLR1 signaling propels retinoic acid-triggered differentiation and cell cycle arrest. 1800 4

The present studies have determined whether interactions between the cyclin-dependent kinase inhibitor flavopiridol and the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA; vorinostat; Zolinza) occur in breast cancer cells. MDA-MB-231 and MCF7 cells were treated with flavopiridol (25-100 nmol/L) and vorinostat (125-500 nmol/L) in vitro, and mechanisms of cell killing were determined. Concurrent treatment of cells with flavopiridol and vorinostat or treatment of cells with flavopiridol followed by vorinostat promoted cell killing in a greater than additive fashion. Similar data were obtained with the CDK inhibitor roscovitine. Flavopiridol suppressed c-FLIP-l/s and BCL-xL expression, whereas vorinostat reduced expression of BCL-xL, and combined exposure to flavopiridol and vorinostat reduced MCL-1 and X-chromosome-linked inhibitor of apoptosis protein (XIAP) levels. Pharmacologic or genetic inhibition of caspase-8 reduced flavopiridol toxicity, but abolished killing by vorinostat and cell death caused by the vorinostat/flavopiridol regimen. Loss of BAX/BAK function or loss of BID function modestly reduced flavopiridol toxicity, but abolished vorinostat-mediated potentiation of flavopiridol toxicity, as did inhibition of caspase-9. Inhibition and/or deletion of cathepsin B function significantly attenuated vorinostat/flavopiridol lethality. Flavopiridol suppressed extracellular signal-regulated kinase 1/2 (ERK1/2) and AKT activity and expression of activated forms of AKT and mitogen-activated protein/ERK kinase 1 maintained c-FLIP-l/s, BCL-xL, and XIAP expression and protected cells against flavopiridol/vorinostat lethality. Overexpression of c-FLIP-s and BCL-xL abolished the lethality of flavopiridol/vorinostat. Collectively, these data argue that flavopiridol enhances the lethality of vorinostat in breast cancer cells in part through the inhibition of AKT and ERK1/2 function, leading to reduced expression of multiple inhibitors of the extrinsic and intrinsic apoptosis pathways, as well as activation of cathepsin protease-dependent pathways.
 ...
PMID:Extrinsic pathway- and cathepsin-dependent induction of mitochondrial dysfunction are essential for synergistic flavopiridol and vorinostat lethality in breast cancer cells. 1806 90

Cell signaling pathways induce Sp1 phosphorylation, which allows for the upregulation of Sp1-dependent genes that control cell growth, cell-cycle progression, survival and tumorigenesis. Sp1 activity is under constitutive repression through the sumoylation of Lysine-16, and Lysine-16 dependent N-terminal cleavage relieves this repression. The present investigation probes further into the mechanisms of Sp1 processing, desumoylation, and degradation to reveal that phosphorylation is the major driving force behind these coupled activities. The first 7 amino acid residues of Sp1 enhance the accessibility of Lysine-16 to the homologous modifiers SUMO-1 and ubiquitin; and Serine-7 specifically enhances ubiquitinylation. Our data show that Serine-59 regulates Sp1 proteolytic processing, and thereby provides a mechanism for the upregulation of Sp1-dependent transcription by CyclinA/cdk2 phosphorylation of Serine-59. Sp1 activators, forskolin and PMA, enhance Sp1 processing in MCFE cells through distinct signaling pathways. PKC, ERK, and ERBB2 kinase inhibitors suppress PMA induction of Sp1 and the specific isozyme PKCalpha enhances Sp1 cleavage. Sp1 contains several NFkappaB2-like proteolytic processing components including a functional phosphorylation-dependent beta-TrCP binding motif. From these data, we propose a model by which cell-cycle and mitotic kinases induce Sp1 proteolytic processing resulting in a desumoylated, derepressed and unstable Sp1 product.
 ...
PMID:Phosphorylation mediates Sp1 coupled activities of proteolytic processing, desumoylation and degradation. 1823 66

JNK and ERK MAP kinases regulate cellular responses to genotoxic stress in a cell type and cell context-dependent manner. However, the factors that determine and execute JNK- and ERK-controlled stress responses are only partly known. In this study, we investigate the roles of the AP-1 components ATF3 and Fra1 in JNK- and ERK-dependent cell cycle arrest and apoptosis. We show that the anti-cancer drug cisplatin or UV light activates both JNK and ERK in human glioblastoma cells lacking functional p53. Inhibition experiments of JNK or ERK activities revealed that the ERK pathway strongly promotes cisplatin- and UV-induced apoptosis in these glioblastoma cells. Furthermore, JNK but not ERK is required for ATF3 induction, and both ERK and JNK are necessary for post-transcriptional induction of Fra1 in response to cisplatin or UV. Knock-down of ATF3 and Fra1 results in increased and decreased cisplatin-induced apoptosis, respectively, indicating that ATF3 is an anti-apoptotic JNK effector and Fra1 is a pro-apoptotic ERK/JNK effector. Knock-down experiments also revealed that ATF3 and Fra1, respectively, enhance and reduce S-phase arrest through differential modulation of the Chk1-Cdk2 pathway. Thus, we identify novel reciprocal functions of ATF3 and Fra1 in JNK- and ERK-dependent DNA damage responses.
 ...
PMID:ATF3 and Fra1 have opposite functions in JNK- and ERK-dependent DNA damage responses. 1824 59

The cellular susceptibility of cancer cells to histone deacetylase (HDAC) inhibitors is increased by the etopic expression of oncogenic Ras. However, the ability of HDAC inhibitors to regulate the apoptotic pathway in human breast cancer cells is still not completely understood. In this study, the anti-proliferative effects of apicidin were compared in H-ras-transformed human breast epithelial (MCF10A-ras) and non-transformed epithelial (MCF10A) cells. MCF10A-ras cells showed a significantly higher growth rate than MCF10A cells. Apicidin significantly increased the levels of acetylated histone H3 and H4 in both cell lines. Western blot analysis and flow cytometry were used to determine if the anti-proliferative effects of apicidin in MCF10A and MCF10A-ras cells could be mediated by modulating the cell cycle. Apicidin attenuated the expression of cyclin E and CDK2 in MCF10A cells, decreased cyclin D1 and cyclin E levels in MCF10A-ras cells, and increased the levels of CDK inhibitors, p21WAF1/Cip1 and p27Kip1, in both cell lines. Notably, the levels of hyperphosphorylation of the Rb protein levels were lower in the MCF10A-ras cells after apicidin treatment. Studies on the regulation of apoptosis showed that apicidin induces the up-regulation of p53 and the downstream activation of ERK in MCF10A-ras cells. The up-regulation of p53 promoted Bax expression leading to activation of caspases-9 and -6, and eventually to apoptosis in MCF10A-ras cells. In addition, apicidin significantly increased the levels of ERK1/2 phosphorylation in MCF10A-ras cells. Therefore, the apicidin-mediated ERK pathway appears to play an important role in modulating the pro-apoptotic pathway in MCF10A-ras cells.
 ...
PMID:Effects of apicidin, a histone deacetylase inhibitor, on the regulation of apoptosis in H-ras-transformed breast epithelial cells. 1828 80

The mammalian target of rapamycin (mTOR) pathway plays a central role in regulating protein synthesis, ribosomal protein translation, and cap-dependent translation. Deregulations in mTOR signaling are frequently associated with tumorigenesis, angiogenesis, tumor growth and metastasis. This review highlights the role of the mTOR in anticancer drug resistance. We discuss the network of signaling pathways in which the mTOR kinase is involved, including the structure and activation of the mTOR complex and the pathways upstream and downstream of mTOR as well as other molecular interactions of mTOR. Major upstream signaling components in control of mTOR activity are PI3K/PTEN/AKT and Ras/Raf/MEK/ERK pathways. We discuss the central role of mTOR in mediating the translation of mRNAs of proteins related to cell cycle progression, those involved in cell survival such as c-myc, hypoxia inducible factor 1* (HIF-1*) and vascular endothelial growth factor (VEGF), cyclin A, cyclin dependent kinases (cdk1/2), cdk inhibitors (p21(Cip1) and p27(Kip1)), retinoblastoma (Rb) protein, and RNA polymerases I and III. We then discuss the potential therapeutic opportunities for using mTOR inhibitors rapamycin, CCI-779, RAD001, and AP-23573 in cancer therapy as single agents or in combinations to reverse drug resistance.
 ...
PMID:Role of mTOR in anticancer drug resistance: perspectives for improved drug treatment. 1844 Aug 54

Epidermal growth factor (EGF) stimulates freshly plated adult hepatocytes to synthesize DNA, but only after they pass through a lag phase of 40 h following EGF exposure. The longer the cells are maintained, they become more responsive to EGF and the lag phase shortens. Maximal EGF-mediated stimulation of DNA synthesis requires the induction of ErbB2, which is not normally expressed in adult hepatocytes. We used immunological methods to demonstrate increased expression during culture of two gene families required for EGF to stimulate hepatocyte DNA synthesis: Akt and ERK 1/2. Both families showed hyperexpression in culture particularly when cells were exposed to insulin and EGF. Unlike CDK-2 and cyclin D1, integral mediators of the G1/S phase transition, ERK 1/2 and Akt appeared in the absence of EGF, particularly when insulin was present. This hyperexpression, which high concentrations of dexamethasone reversed, increased basal and growth factor-stimulated phosphorylation of Akt and ERK 1/2. Pharmacological blockade of phosphatidylinositol kinase suppressed the Akt increase whereas pharmacological blockade or small interfering RNA downregulation of ErbB2 inhibited both Akt and ERK 1/2 expression. All three Akt isoforms contributed to the increase in total Akt. EGF but not insulin specifically upregulated Akt 2 and 3. Since Akt and ERK 1/2 are also hyperexpressed in poorly differentiated hepatomas, their dysregulation in cancer may involve transcriptional mechanisms normally operative in cultured hepatocytes. We hypothesize that the induction and activation of ErbB2 increases the expression of these kinases, enhancing the responsiveness of hepatocytes to EGF as they adapt to culture.
 ...
PMID:Cultured rat hepatocytes upregulate Akt and ERK in an ErbB-2-dependent manner. 1853 89

How cyclic AMP (cAMP) could positively or negatively regulate G1 phase progression in different cell types or in cancer cells versus normal differentiated counterparts has remained an intriguing question for decades. At variance with the cAMP-dependent mitogenesis of normal thyroid epithelial cells, we show here that cAMP and cAMP-dependent protein kinase activation inhibit S-phase entry in four thyroid carcinoma cell lines that harbor a permanent activation of the Raf/ERK pathway by different oncogenes. Only in Ret/PTC1-positive TPC-1 cells did cAMP markedly inhibit the Raf/ERK cascade, leading to mTOR pathway inhibition, repression of cyclin D1 and p21 and p27 accumulation. p27 knockdown did not prevent the DNA synthesis inhibition. In the other cells, cAMP little affected these signaling cascades and levels of cyclins D or CDK inhibitors. However, cAMP differentially inhibited the pRb-kinase activity and T172-phosphorylation of CDK4 complexed to cyclin D1 or cyclin D3, whereas CDK-activating kinase activity remained unaffected. At variance with current conceptions, our studies in thyroid carcinoma cell lines and previously in normal thyrocytes identify the activating phosphorylation of CDK4 as a common target of opposite cell cycle regulations by cAMP, irrespective of its impact on classical mitogenic signaling cascades and expression of CDK4 regulatory partners.
 ...
PMID:Cyclic AMP inhibits the proliferation of thyroid carcinoma cell lines through regulation of CDK4 phosphorylation. 1879 15

The differentiation capacity of mesenchymal stem cells has been extensively studied, but little is known on cell cycle-related events in the proliferation and differentiation phases of these cells. Here, we demonstrate that exposure to cAMP-increasing agents inhibits proliferation of adipose stem cells (ASCs). This antiproliferative effect is associated with both reduced cdk2 activity and pRB phosphorylation. Concomitantly, however, the level of cyclin E markedly increases upon cAMP induction, indicating that cyclin E may have cdk2-independent functions in these cells besides its role as a cdk2 activator. Indeed, we found indications of a cdk2-independent role of cyclin E in DNA damage-induced apoptosis. 8-CPT-cAMP sensitizes ASCs to gamma-irradiation-induced apoptosis, an effect abolished by knockdown of cyclin E. Moreover, cAMP induces early activation of ERK, leading to reduced degradation of cyclin E. The cAMP-mediated up-regulation of cyclin E was blocked by knockdown of ERK or by an inhibitor of the ERK kinase MEK. We conclude that cAMP inhibits cdk2 activity and pRB phosphorylation, leading to reduced ASC proliferation. Concomitant with this growth inhibition, however, cyclin E levels are increased in a MEK/ERK-dependent manner. Our results suggest that cyclin E plays an important, cdk2-independent role in genotoxic stress-induced apoptosis in mesenchymal stem cells.
 ...
PMID:cAMP-mediated induction of cyclin E sensitizes growth-arrested adipose stem cells to DNA damage-induced apoptosis. 1879 28

An aromatic fatty acid, phenylacetate (PA), has been shown to have cytostatic, antitumor and cell differentiation-inducing effects on various kinds of tumors. Previously, we have demonstrated cell growth inhibition, malignant phenotype reduction and cell differentiation effects of sodium phenylacetate (NaPA) treatment in a canine mammary tumor cell line. To clarify the molecular mechanism of these effects, we examined the expression of Ras/MAPK signaling pathway-related molecules in human and canine breast cancer cell lines, and found that the level of c-Raf-1 protein was reduced by 5, 10 and 20 mM of NaPA treatments, though Ras activation was maintained. Dephosphorylation of c-Raf-1 at Serine (Ser) 259, Ser 338, and Ser 621 were also seen in NaPA-treated cells. Downstream factors in the pathway, such as mitogen-activated protein kinase/ERK kinase (MEK)1/2 and ERK1/2, showed decreased activity, and accordingly, expressions of cyclinD1, c-myc, and inactivation of p90 ribosomal S6 kinase (RSK), which are MAPK targets, were reduced. We also observed the reduction of cell-cycle-promoted molecules, such as cdc1/cdk2, cdk4, PCNA cyclin A, and cyclin B, and the increased expression of p27kip1. Furthermore, expression of an epithelial marker, E-cadherin, was increased by NaPA treatment. These results suggest that one of the molecular targets of NaPA treatment was the reduction of c-Raf-1 protein, and that its reduction results in the decrease of malignant characteristics of tumor cells through blockage of the Ras/MAPK signaling pathway.
 ...
PMID:Sodium phenylacetate inhibits the Ras/MAPK signaling pathway to induce reduction of the c-Raf-1 protein in human and canine breast cancer cells. 1895 52


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>