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)

Methylxantine derivative, caffeine, is known to prevent the p53-dependent apoptosis pathway via inhibition of ATM (ataxia telangiectasia mutated) kinase, which activates p53 by phosphorylation of the Ser-15 residue. In contrast, it has been reported that caffeine induces p53-mediated apoptosis through Bax protein in non-small-cell lung cancer cells. Therefore, the effects of caffeine on cellular growth in malignant cells are controversial. We investigated the effects of caffeine on cell proliferation, cell cycle progression, and induction of apoptosis in NB4 promyelocytic leukemia cells containing wild-type p53. Caffeine suppressed the cellular growth of NB4 cells in a dose- and time-dependent manner. Caffeine induced G(2)/M phase cell cycle arrest in NB4 cells in association with the induction of phosphorylation at the Ser-15 residue of p53 and induction of tyrosine phosphorylation of cdc2. Expression of Bax protein was increased in NB4 cells after treatment with caffeine. Interestingly, the antisense oligonucleotides for p53 significantly reduced p53 expression and caffeine-induced G(2)/M phase cell cycle arrest in NB4 cells. These results suggest that caffeine induces cell cycle arrest and apoptosis in association with activation of p53 by a novel pathway to phosphorylate the Ser-15 residue and induction of phosphorylation of cdc 2 in leukemic cells with normal p53.
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PMID:Caffeine induces G2/M arrest and apoptosis via a novel p53-dependent pathway in NB4 promyelocytic leukemia cells. 1281 20

Arsenic trioxide (As(2)O(3)), an effective drug for the treatment of acute promyelocytic leukemia (APL), can induce apoptosis and partial differentiation in APL cells in vitro and in vivo. However, As(2)O(3) also induces apoptosis in cancer cells other than APL with complex mechanisms, which seem to be cell type dependent. In this study, we report that APL cells (NB4 cell line) are arrested at early mitotic phase before the collapse of mitochondrial transmembrane potential (Deltavarphi(m)) and apoptosis after treatment with pharmacological concentrations (1.0-2.0 micro M) of As(2)O(3). We have also made the following new discoveries: (1) 0.5 micro M As(2)O(3) that fails to induce apoptosis has no effects on cell cycle distribution. (2) With inhibition of As(2)O(3)-induced Deltavarphi(m) collapse and apoptosis, dithiothreitol also effectively inhibits As(2)O(3)-induced mitotic arrest, suggesting that both As(2)O(3)-induced apoptosis and mitotic arrest involve proteins with thiol groups. (3) 1.5 mM caffeine that relieves cells from G(2)/M arrest also inhibits As(2)O(3)-induced Deltavarphi(m) collapse and apoptosis, (4) 1.0 micro M As(2)O(3) increases the expression of both cyclin B(1) and hCDC20 whereas it inhibits Tyr15 phosphorylation of p34(cdc2). In conclusion, our results strongly support that there is a tight link between As(2)O(3)-induced apoptosis and mitotic arrest, the latter being one of common mechanisms for As(2)O(3)-induced apoptosis in cancer cells.
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PMID:Arsenic trioxide-induced mitotic arrest and apoptosis in acute promyelocytic leukemia cells. 1283 21

Ataxia teleangiectasia mutated (ATM) kinase, ATM-Rad3-related (ATR) kinase and DNA-protein kinase (DNA-PK) belong to a subgroup of protein kinases which play a role in the DNA damage response. In this study, cisplatin was shown to increase ATR activity and decrease ATM and DNA-PK activity. Caffeine, a nonspecific inhibitor of ATR, enhanced the cytotoxic effect of cisplatin, modestly decreased the p53 and p21WAF-1 response to cisplatin, and affected the cdc2-p34/cyclin B1 complex by decreasing both cyclin B1 protein accumulation and cdc2-p34 tyrosine 15 phosphorylation. The observed alteration of several potential ATR downstream targets suggests that inhibition of ATR activity may be one of the mechanism by which caffeine regulates sensitivity to cisplatin.
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PMID:Inhibition of cisplatin-induced ATR activity and enhanced sensitivity to cisplatin. 1289 3

Timing of DNA replication initiation is dependent on S-phase-promoting kinase (SPK) activity at discrete origins and the simultaneous function of many replicons. DNA damage prevents origin firing through the ATM- and ATR-dependent inhibition of Cdk2 and Cdc7 SPKs. Here, we establish that modulation of ATM- and ATR-signalling pathways controls origin firing in the absence of DNA damage. Inhibition of ATM and ATR with caffeine or specific neutralizing antibodies, or upregulation of Cdk2 or Cdc7, promoted rapid and synchronous origin firing; conversely, inhibition of Cdc25A slowed DNA replication. Cdk2 was in equilibrium between active and inactive states, and the concentration of replication protein A (RPA)-bound single-stranded DNA (ssDNA) correlated with Chk1 activation and inhibition of origin firing. Furthermore, ATM was transiently activated during ongoing replication. We propose that ATR and ATM regulate SPK activity through a feedback mechanism originating at active replicons. Our observations establish that ATM- and ATR-signalling pathways operate during an unperturbed cell cycle to regulate initiation and progression of DNA synthesis, and are therefore poised to halt replication in the presence of DNA damage.
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PMID:ATR and ATM regulate the timing of DNA replication origin firing. 1523 85

Human checkpoint kinase 1 (Chk1) is an essential kinase required to preserve genome stability. Here, we show that Chk1 inhibition by two distinct drugs, UCN-01 and CEP-3891, or by Chk1 small interfering RNA (siRNA) leads to phosphorylation of ATR targets. Chk1-inhibition triggered rapid, pan-nuclear phosphorylation of histone H2AX, p53, Smc1, replication protein A, and Chk1 itself in human S-phase cells. These phosphorylations were inhibited by ATR siRNA and caffeine, but they occurred independently of ATM. Chk1 inhibition also caused an increased initiation of DNA replication, which was accompanied by increased amounts of nonextractable RPA protein, formation of single-stranded DNA, and induction of DNA strand breaks. Moreover, these responses were prevented by siRNA-mediated downregulation of Cdk2 or the replication initiation protein Cdc45, or by addition of the CDK inhibitor roscovitine. We propose that Chk1 is required during normal S phase to avoid aberrantly increased initiation of DNA replication, thereby protecting against DNA breakage. These results may help explain why Chk1 is an essential kinase and should be taken into account when drugs to inhibit this kinase are considered for use in cancer treatment.
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PMID:Inhibition of human Chk1 causes increased initiation of DNA replication, phosphorylation of ATR targets, and DNA breakage. 1583 61

When the nucleus in G0/G1 phase is transferred to an enucleated oocyte by nuclear transfer (NT), its nuclear envelope is broken, followed by condensation of chromosome structure by maturation promoting factor (MPF). This morphological remodeling of the transferred interphase nucleus seems to be essential for subsequent development of NT embryos. In this study, we treated porcine NT embryos with caffeine, which has been reported to increase MPF activity, to keep their MPF level high during NT. When 2.5 mM caffeine was added to the handling medium, the proportion of NT embryos showing condensed chromosome increased significantly (P < 0.05). In NT embryos treated with caffeine, the activity of p34(cdc2) kinase was significantly (P < 0.05) higher than in those without caffeine at 3 h post-injection. In addition, the rate of development to the blastocyst stage after activation was significantly (P < 0.05) higher in NT embryos treated with caffeine. These results indicate that caffeine treatment can increase not only the rate of chromosome condensation but also the developmental rate to the blastocyst stage of porcine NT embryos. This action is most likely due to the support/increase of MPF activity throughout the process of NT.
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PMID:Caffeine promotes premature chromosome condensation formation and in vitro development in porcine reconstructed embryos via a high level of maturation promoting factor activity during nuclear transfer. 1612 42

Ataxia-telangiectasia mutated (ATM) and ATM- and Rad3-related (ATR) kinases, family members of the PI-3 kinase related proteins, play a key role in checkpoint activation and maintenance of genomic stability following DNA damage. We have used wild type (WT) and p38alpha-deficient mouse embryonic stem (ES) cells to investigate the role of ATR and ATM kinases during embryonic cell cycle. We have found that inhibition of ATR and ATM kinases with caffeine or Chk1 with UCN-01, results in activation of a p38-dependent intra-S-phase checkpoint and activation of apoptosis in ES cells. However, wortmannin at a concentration, that inhibits ATM kinase but not ATR kinase, did not affect cell cycle progression. Furthermore, the presence of caffeine results in activation of p38 kinase, accumulation of p21/Waf1 in a complex with Cdk2 and decrease of Cdk2 kinase activity. In contrast, caffeine-treated p38alpha-/- ES cells show less apoptosis, and fail to trigger an effective S-phase checkpoint and accumulation of p21/Waf1. We conclude that ATR kinase activity is essential for normal cell cycle progression of exponentially proliferating mouse ES cells even in the absence of exogenous DNA damage, and ATR deregulation triggers p38alpha-dependent cell-cycle checkpoint and apoptotic responses.
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PMID:Inhibition of the ATR/Chk1 pathway induces a p38-dependent S-phase delay in mouse embryonic stem cells. 1613 10

Measurement of dicentric chromosomes in human lymphocytes has been applied to assess dose received by potentially overexposed people and estimate risk for health effects. Since the dicentrics in exposed people decrease with time, the introduction of fluorescent in situ hybridisation enables to measure stable translocations for biodosimetry and address old or long-term exposures. In addition, premature chromosome condensation, which enables analysis in interphase, offers several advantages for biodosimetry. However, dose and risk estimates derived using cytogenetics and adequate calibration curves are based on the assumption that all individuals respond equally to radiation. Since increased radiosensitivity has been associated with cancer proneness, there is particular interest for risk assessment at the individual level. Towards this end, the efficiency of dynamics that govern DNA repair and apoptosis, as well as the conserved cellular processes that have evolved to facilitate DNA damage recognition using signal transduction pathways to activate cell cycle arrest and preserve genomic integrity, are being investigated. Recent work in cancer cytogenetics and on the modulation of radiation effects at the chromosome level using changes in gene expression associated with proteins or factors such as caffeine or amifostine treatment during G(2) to M-phase transition, reconfirmed the importance of G(2) chekpoint in determining radiosensitivity and of the cdk1/cyclin-B activity in the conversion of DNA damage into chromatid breaks. G(2)-chromosomal radiosensitivity may offer, therefore, a basis for the identification or testing of key genetic targets for modulation of radiation effects and the establishment of a screening method to detect intrinsic radiosensitivity.
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PMID:Cytogenetic methods for biodosimetry and risk individualisation after exposure to ionising radiation. 1716 46

We recently reported that gallic acid is a major active agent responsible for grape seed extract activity in DU145 human prostate carcinoma cells. The present study was conducted to examine its efficacy and associated mechanism. Gallic acid treatment of DU145 cells resulted in a strong cell growth inhibition, cell cycle arrest, and apoptotic death in a dose- and time-dependent manner, together with a decrease in cyclin-dependent kinases and cyclins but strong induction in Cip1/p21. Additional mechanistic studies showed that gallic acid induces an early Tyr(15) phosphorylation of cell division cycle 2 (cdc2). Further upstream, gallic acid also induced phosphorylation of both cdc25A and cdc25C via ataxia telangiectasia mutated (ATM)-checkpoint kinase 2 (Chk2) activation as a DNA damage response evidenced by increased phospho-histone 2AX (H2A.X) that is phosphorylated by ATM in response to DNA damage. Time kinetics of ATM phosphorylation, together with those of H2A.X and Chk2, was in accordance with an inactivating phosphorylation of cdc25A and cdc25C phosphatases and cdc2 kinase, suggesting that gallic acid increases cdc25A/C-cdc2 phosphorylation and thereby inactivation via ATM-Chk2 pathway following DNA damage that induces cell cycle arrest. Caffeine, an ATM/ataxia telangiectasia-rad3-related inhibitor, reversed gallic acid-caused ATM and H2A.X phosphorylation and cell cycle arrest, supporting the role of ATM pathway in gallic acid-induced cell cycle arrest. Additionally, gallic acid caused caspase-9, caspase-3, and poly(ADP)ribose polymerase cleavage, but pan-caspase inhibitor did not reverse apoptosis, suggesting an additional caspase-independent apoptotic mechanism. Together, this is the first report identifying gallic acid efficacy and associated mechanisms in an advanced and androgen-independent human prostate carcinoma DU145 cells, suggesting future in vivo efficacy studies with this agent in preclinical prostate cancer models.
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PMID:Gallic acid causes inactivating phosphorylation of cdc25A/cdc25C-cdc2 via ATM-Chk2 activation, leading to cell cycle arrest, and induces apoptosis in human prostate carcinoma DU145 cells. 1717 33

The spindle assembly checkpoint arrests cells in mitosis when defects in mitotic spindle assembly or partitioning of the replicated genome are detected. This checkpoint blocks exit from mitosis until the defect is rectified or the cell initiates apoptosis. In this study we have used caffeine to identify components of the mechanism that signals apoptosis in mitotic checkpoint-arrested cells. Addition of caffeine to spindle checkpoint-arrested cells induced >40% apoptosis within 5 h. It also caused proteasome-mediated destruction of cyclin B1, a corresponding reduction in cyclin B1/cdk1 activity, and reduction in MPM-2 reactivity. However, cells retained MAD2 staining at the kinetochores, an indication of continued spindle checkpoint function. Blocking proteasome activity did not block apoptosis, but continued spindle checkpoint function was essential for apoptosis. After systematically eliminating all known targets, we have identified p21-activated kinase PAK1, which has an anti-apoptotic function in spindle checkpoint-arrested cells, as a target for caffeine inhibition. Knockdown of PAK1 also increased apoptosis in spindle checkpoint-arrested cells. This study demonstrates that the spindle checkpoint not only regulates mitotic exit but apoptosis in mitosis through the activity of PAK1.
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PMID:Caffeine promotes apoptosis in mitotic spindle checkpoint-arrested cells. 1718 11


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