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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Flavopiridol (L86-8275), a N-methylpiperidinyl, chlorophenyl flavone, can inhibit cell cycle progression in either G1 or G2 and is a potent cyclin-dependent kinase (CDK) 1 inhibitor. In this study, we used MCF-7 breast carcinoma cells that are wild type for p53 and pRb positive and contain CDK4-cyclin D1 and MDA-MB-468 breast carcinoma cells that are mutant p53, pRb negative, and lack CDK4-cyclin D1 to investigate the G1 arrest produced by Flavopiridol. Recombinant CDK4-cyclin D1 was inhibited potently by Flavopiridol (Kiapp, 65 nM), competitive with respect to ATP. Surprisingly, CDK4 immunoprecipitates derived from Flavopiridol-treated MCF-7 cells (3 h, 300 nM Flavonolpiridol) had an approximately 3-fold increased kinase activity compared with untreated cells. Cyclin D and CDK4 levels were not different at 3 hr, but cyclin D levels and CDK4 kinase activity decreased thereafter. The phosphorylation state of pRb was shifted from hypercoincident to hypocoincident with the development of G1 arrest. Asynchronous MDA-MB-468 cells were inhibited in cell cycle progression at both G1 and G2 by Flavopiridol. Flavopiridol inhibited the in vitro kinase activity of CDK2 using an immune complex kinase assay (IC50, 100 nM at 400 microM ATP). Immunoprecipitated CDK2 kinase activity from either MCF-7 or MDA-MB-468 cells exposed to Flavopiridol (300 nM) for increasing time showed an initial increased activity (approximately 1.5-fold at 3 h) compared with untreated cells, followed by a loss of kinase activity to immeasurable levels by 24 h. This increased immunoprecipitated kinase activity was dependent on the Flavopiridol concentration added to intact cells and was associated with a reduction of CDK2 tyrosine phosphorylation. Cyclin E and A levels were not altered to the same extent as cyclin D, and neither CDK4 nor CDK2 levels were changed in response to Flavopiridol. Inhibition of the CDK4 and/or CDK2 kinase activity by Flavopiridol can therefore account for the G1 arrest observed after exposure to Flavopiridol.
...
PMID:Flavopiridol induces G1 arrest with inhibition of cyclin-dependent kinase (CDK) 2 and CDK4 in human breast carcinoma cells. 867 31

Here, we compare the pathways by which DNA-damaging agents, NGF deprivation, and superoxide dismutase 1 (SOD1) depletion evoke apoptosis of sympathetic neurons. Previous work raised the hypothesis that cell cycle signaling plays a required role in neuronal apoptosis elicited by NGF deprivation and the DNA-damaging agent camptothecin. To test this hypothesis, we extended our investigation of DNA-damaging agents to cytosine arabinoside (AraC) and UV irradiation. As with NGF deprivation and camptothecin treatment, the cyclin-dependent kinase inhibitors flavopiridol and olomoucine protected neurons from apoptosis induced by AraC and UV treatment. These observations support the model that camptothecin, AraC, and UV treatment cause DNA damage, which leads to apoptosis by a mechanism that, as in the case of NGF deprivation, includes activation of cell cycle components. Flavopiridol and olomoucine, however, had no effect on death induced by SOD1 depletion, suggesting that CDKs do not play a role in this paradigm of neuronal death. To compare further the mechanisms of death evoked by NGF withdrawal, SOD1 depletion, and DNA-damaging agents, we investigated their responses to inhibitors of cysteine aspartases, elements of apoptotic pathways. The V-ICEinh and BAF, two peptide inhibitors of cysteine aspartases, protected neurons in all three death paradigms. In contrast, the cysteine aspartase inhibitory peptide zVAD-fmk conferred protection from NGF withdrawal and SOD1 depletion, but not DNA-damaging agents, whereas acYVAD-cmk protected only from SOD1 depletion. Taken together, these findings indicate that three different apoptotic stimuli activate separate pathways of death in the same neuron type.
...
PMID:Multiple pathways of neuronal death induced by DNA-damaging agents, NGF deprivation, and oxidative stress. 943 5

Flavopiridol, a synthetic flavone that inhibits tumor growth in vitro and in vivo, is a potent cyclin-dependent kinase (cdk) inhibitor presently in clinical trials. In the present study, the effect of 100-500 nM flavopiridol on a panel of non-small cell lung cancer cell lines was examined. All express a wild-type retinoblastoma susceptibility protein and lack p16INK4A, and only A549 cells are known to express wild-type p53. During 72 h of treatment, flavopiridol was shown to be cytotoxic to all seven cell lines, as measured by trypan blue exclusion, regardless of whether cells were actively cycling. In most cycling cells, cytotoxicity was preceded or accompanied by cell cycle arrest. Cell death resulted in the appearance of cells with a sub-G1 DNA content, suggestive of apoptosis, which was confirmed by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and by demonstration of cleavage of caspase targets including poly(ADP-ribose) polymerase, p21Waf1, and p27Kip1. At doses at or below 500 nM, maximal cytotoxicity required 72 h of exposure. Although flavopiridol resulted in the accumulation of p53 in A549 cells, flavopiridol-mediated apoptosis was p53 independent because it occurred to the same degree in A549 cells in which p53 was targeted for degradation by HPV16E6 expression. The data indicate that flavopiridol has activity against non-small cell lung cancers in vitro and is worthy of continued clinical development in the treatment of this disease.
...
PMID:Flavopiridol induces cell cycle arrest and p53-independent apoptosis in non-small cell lung cancer cell lines. 1053 62

We have investigated the effects of flavopiridol, a novel protein kinase inhibitor that is selective for cyclin-dependent kinases, on hypoxia-induced vascular endothelial growth factor (VEGF) expression in human monocytes. We found that hypoxia induces a time-dependent increase of VEGF mRNA expression and protein levels in human monocytes. Flavopiridol showed a minimal effect on the constitutive levels of VEGF mRNA but completely blocked hypoxia-induced VEGF mRNA and protein expression. The inhibitory effects of flavopiridol on VEGF mRNA induction also occurred in the presence of cycloheximide. The transcriptional activation of either a VEGF promoter-luciferase construct or a hypoxia-inducible factor 1 reporter plasmid was not affected by addition of flavopiridol in transient transfection experiments. In contrast, actinomycin D experiments demonstrated that flavopiridol dramatically decreased VEGF mRNA stability. These data provide the first evidence that flavopiridol can affect gene expression by altering mRNA stability. We propose that flavopiridol may interfere with one or more signaling events, leading to hypoxia-induced, protein kinase-modulated, RNA protein binding activity. An important clinical implication of our results is that flavopiridol, presently under investigation in clinical trials, might have antiangiogenic as well as direct antiproliferative effects.
...
PMID:Flavopiridol, a protein kinase inhibitor, down-regulates hypoxic induction of vascular endothelial growth factor expression in human monocytes. 1055 12

Cyclin dependent kinases (CDKs) along with the complementary cyclins form key regulatory checkpoint controls on the cell cycle. Flavopiridol is a synthetic flavone that shows potent and selective cyclin-dependent kinase inhibitory activity. In this paper, we report modifications of the 3-hydroxy-1-methylpiperidinyl (D ring) of flavopiridol and their effect on CDK inhibitory activity.
...
PMID:Structure-activity relationship studies of flavopiridol analogues. 1084 11

Flavopiridol (L86-8275, HMR1275) is a cyclin-dependent kinase (Cdk) inhibitor that is in clinical trials as a cancer treatment because of its antiproliferative properties. We found that the flavonoid potently inhibited transcription by RNA polymerase II in vitro by blocking the transition into productive elongation, a step controlled by P-TEFb. The ability of P-TEFb to phosphorylate the carboxyl-terminal domain of the large subunit of RNA polymerase II was inhibited by flavopiridol with a K(i) of 3 nm. Interestingly, the drug was not competitive with ATP. P-TEFb composed of Cdk9 and cyclin T1 is a required cellular cofactor for the human immunodeficiency virus (HIV-1) transactivator, Tat. Consistent with its ability to inhibit P-TEFb, flavopiridol blocked Tat transactivation of the viral promoter in vitro. Furthermore, flavopiridol blocked HIV-1 replication in both single-round and viral spread assays with an IC(50) of less than 10 nm.
...
PMID:Flavopiridol inhibits P-TEFb and blocks HIV-1 replication. 1090 20

Flavopiridol (L86-8275, HMR1275) is a cyclin-dependent kinase (Cdk) inhibitor in clinical trials as a cancer therapy that has been recently shown to block human immunodeficiency virus Tat transactivation and viral replication through inhibition of positive transcription elongation factor b (P-TEFb). Flavopiridol is the most potent P-TEFb inhibitor reported and the first Cdk inhibitor that is not competitive with ATP. We examined the ability of flavopiridol to inhibit P-TEFb (Cdk9/cyclin T1) phosphorylation of both RNA polymerase II and the large subunit of the 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor and found that the IC(50) determined was directly related to the concentration of the enzyme. We concluded that the flavonoid associates with P-TEFb with 1:1 stoichiometry even at concentrations of enzyme in the low nanomolar range. These results indicate that the apparent lack of competition with ATP could be caused by a very tight binding of the drug. We developed a novel immobilized P-TEFb assay and demonstrated that the drug remains bound for minutes even in the presence of high salt. Flavopiridol remained bound in the presence of a 1000-fold excess of the commonly used inhibitor DRB, suggesting that the immobilized P-TEFb could be used in a simple screening assay that would allow the discovery or characterization of compounds with binding properties similar to flavopiridol. Finally, we compared the ability of flavopiridol and DRB to inhibit transcription in vivo using nuclear run-on assays and concluded that P-TEFb is required for transcription of most RNA polymerase II molecules in vivo.
...
PMID:Flavopiridol inactivates P-TEFb and blocks most RNA polymerase II transcription in vivo. 1143 68

As a result of substantial advances in recent cancer biology, cell cycle regulation in the G1 phase has attracted a great deal of attention as a promising target for the research and treatment of cancer. Many of the important genes associated with G1 regulation have been shown to play a key role in proliferation, differentiation and oncogenic transformation and programmed cell death (apoptosis). Currently, a variety of "cytostatic" agents that affects G1 progression and/or G1/S transition are being evaluated in clinical trials. Flavopiridol is a potent inhibitor of cyclin-dependent kinases (CDKs). UCN-01 was originally found to be a PKC-selective protein kinase antagonist. More recent studies have revealed that this agent can also inhibit several CDKs and the checkpoint kinase CHK1. FR901228, MS-27-275 and SAHA are histone deacetylase inhibitors that induce changes in the transcription of specific genes via the hyperacetylation of histones. The proteasome inhibitor PS-341 disrupts the degradation process of intracellular proteins, including cell cycle regulatory proteins such as cyclins. R115777, SCH66336 and BMS-214662 are non-peptidic farnesyl transferase inhibitors that prevent p21 ras oncogene activation. Rapamycin derivative CCI-779 downregulates signals through S6 kinase and FRAP (FKBP-rapamycin associating protein), affecting the expression levels of mRNAs important for progression from G1 to S phase. 17-Allylaminogeldanamycin targets the Hsp-90 (heat shock protein-90) family of cellular chaperones regulating the function of signaling proteins. TNP-470 (AGM-1470), a fumagillin derivative shows antiangiogenic action through binding to MetAP-2 (methionine aminopeptidase-2). The antitumor sulfonamide E7070, causing a cellular accumulation in the G1 phase, has been shown to suppress the activation of CDK2 and cyclin E expression in HCT116 colorectal cancer cell line highly sensitive to the drug. With respect to several growth factor receptors such as EGFR, PDGFR, bFGFR and VEGFR, potent and specific inhibitors of receptor tyrosine kinases have been also examined as hopeful drug candidates. In this report, we review the current status of extensive efforts directed towards the discovery and development of new chemotherapeutic anticancer agents targeting cell cycle regulation in the G1 phase, with particular focus on the compounds undergoing clinical investigations.
...
PMID:Cell cycle regulation in the G1 phase: a promising target for the development of new chemotherapeutic anticancer agents. 1156 78

The glomerular lesions of HIV-associated nephropathy (HIVAN) are associated with the expression of HIV-1 in podocytes. Infected podocytes proliferate and lose several differentiation markers in vivo and in vitro, which suggests that HIV-1 gene expression induces these changes. Flavopiridol and roscovitine, newly identified inhibitors of cyclin-dependent kinase-9, markedly decrease HIV-1 promoter activity in cell lines of various lineages. In this study, the inhibitors were used to determine whether suppression of HIV-1 transcription in infected podocytes correlated with an inhibition of proliferation and a return to the differentiated phenotype. Dose-response analysis showed that both flavopiridol and roscovitine reversibly suppressed HIV-1 transcription in podocytes in vitro at an IC(50) of 25 nM and 3 microM, respectively. Despite equivalent suppression of HIV-1 transcription, roscovitine was a more effective inhibitor of podocyte proliferation than flavopiridol. Suppression of HIV-1 transcription by flavopiridol or roscovitine was marked by re-expression of the podocyte differentiation markers, synaptopodin and podocalyxin. These results suggest that inhibition of HIV-1 transcription decreases podocyte proliferation and permits the reexpression of differentiation markers. Thus, suppression of HIV-1 transcription by selective cyclin-dependent kinase-9 inhibitors may be a useful therapeutic strategy for the treatment of HIVAN.
...
PMID:Suppression of HIV-1 expression by inhibitors of cyclin-dependent kinases promotes differentiation of infected podocytes. 1172 53

Trypanosoma cruzi CRK3 gene encodes a Cdc2p related protein kinase (CRK). To establish if it has a role in the regulation of the parasite cell cycle we studied CRK3 expression and activity throughout three life cycle stages. CRK3 from epimastigote soluble extracts interacted with p13(suc1)-beads. Endogenous CRK3 phosphorylated histone H1 and this activity was inhibited by specific CDK inhibitors: Olomoucine, Flavopiridol and Roscovitine. Flavopiridol partially inhibited the growth of T. cruzi epimastigotes at 50 nM, the lowest concentration used, but even with the highest (5 microM), cell growth was not completely arrested. CRK3 from Flavopiridol-inhibited epimastigote extracts exhibited a dose dependent inhibition of histone H1 phosphorylation. T. cruzi p13(suc1)-binding CRK displayed the same inhibition profile. This suggests that CRK3 is the enzyme responsible for the majority of the kinase activity associated with p13(suc1). CRK3 activity of hydroxyurea (HU) synchronized epimastigotes peaked in G2/M boundary while the kinase activity associated to p13(suc1)-beads increased at the same time point but remained high until late G2/M. In addition, CRK3 expression was constant during the cell cycle. This is a common pattern of CDK activity regulation. Taken together, these results support the idea that CRK3 is involved in control of the cell cycle in T. cruzi.
...
PMID:Evidence for CRK3 participation in the cell division cycle of Trypanosoma cruzi. 1203 56


1 2 3 4 Next >>

---