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)

Some anticancer agents induce cell cycle arrest. We analyzed the effect of anticancer agents on cell-cycle regulators, such as CDK. Our data suggested that arresting cells in the G2-phase of the cell cycle by cisplatin might be regulated by dephosphorylation of cdc2 kinase. Butyrolactone I inhibits both cdc2 and CDK2 kinase in the cell-free system. The cytotoxic effect of paclitaxel shows mainly in the M-phase of the cell cycle. Suramin inhibits cdc2 kinase. UCN-01, a protein kinase-C inhibitor, also inhibits both cdc2 and CDK2 kinase. Some anticancer agents induce apoptosis.
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PMID:[Cell cycle regulation by anticancer agent]. 757 1

7-Hydroxystaurosporine (UCN-01) is a potent inhibitor of protein kinase C (PKC) isozymes alpha, beta, and gamma [Seynaeve et al., Mol. Pharmacol, 45: 1207-1214, 1994] that also has antitumor effects in vivo. To determine whether inhibition of PKC can be related to inhibition of cell growth with induction of apoptosis, we compared the effects of UCN-01 to those of the highly selective bisindolylmaleimide PKC antagonist GF 109203X in leukemic T-cell lines. Both compounds potently inhibited PKC activity when added to T-cell membrane preparations and reversed phorbol ester-induced c-fos gene expression in intact cells. However, whereas UCN-01 potently inhibited growth of Jurkat, Molt-3, Molt-4, and Hut-78 cells (IC50 = 20-65 nM, irreversible after 24 h of exposure), GF 109203X had IC50s for cell growth of 3.6-5.0 muM. Less than 3 h after addition, UCN-01 but not GF 109203X-treated cells displayed loss of cells with G2-M DNA content, appearance of a hypodiploid DNA fraction, and evidence of internucleosomal DNA fragmentation. Six h after treatment, cells appeared to accumulate with S-phase DNA content. These effects correlated with selective UCN-01 but not GF 109203X-induced decrease in total and tyrosine phosphorylation of cyclin-dependent kinases (cdks) 1 and 2, and with increases in the histone H1 kinase activities of cdk1 and cdk2. UCN-01 was relatively less potent in inhibition of properly activated cdk1 and cdk2 when added in vitro to H1 kinase assays (IC50 = 1000 and 600 nM, respectively). We conclude that inhibition of PKC alone is not sufficient to account for the actions of UCN-01 and are led to the hypothesis that inappropriate cdk activation either correlates with or actually mediates cell growth inhibition with apoptosis in T lymphoblasts exposed to UCN-01.
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PMID:Apoptosis in 7-hydroxystaurosporine-treated T lymphoblasts correlates with activation of cyclin-dependent kinases 1 and 2. 854 21

UCN-01 (7-hydroxyl-staurosporine) was originally isolated as a Ca2+- and phospholipid-dependent protein kinase C selective inhibitor and now is being developed as an anticancer agent. Results from our and other laboratories have suggested that UCN-01 induces preferential G1-phase accumulation in several human tumor cell lines tested. To elucidate this mechanism, we examined the effects of UCN-01 on several cell cycle-regulatory proteins critical for G1-S-phase transition in p53-mutated human epidermoid carcinoma A431 cells. After 24 h exposure at around 50% growth-inhibitory concentrations (IC50s), 260 and 520 nM, UCN-01 induced the accumulation of pRb (the dephosphorylated retinoblastoma protein form). The protein expression of cyclin A but not cyclin E was markedly reduced and that of cyclin D1 was partially reduced under the same condition. UCN-01 also showed the concentration-dependent inhibitions of the activity of cyclin-dependent kinase 2 (CDK2) using histone H1 and pRb as substrates in vitro (IC50, 530 and 640 nM, respectively). In addition, CDK2 activities of the cells pretreated with UCN-01 for 24 h at 260 and 520 nM were markedly inhibited, giving IC50s of far less than 260 nM. When the same cell lysates were analyzed by Western blotting for CDK2, the lower band (e.g., active and phosphorylated CDK2) was remarkably reduced, in accordance with the reduced activity. Furthermore, UCN-01 induced the expression of the CDK inhibitor p21 protein and its complex formation with CDK2 after 24 h exposure at 260 and 520 nM, whereas the expression level was very low or undetectable in untreated or DNA-damaged cells. The increase of p21 mRNA levels was also induced under the same condition. UCN-01 further increased luciferase activities in A431 cells transiently transfected with p21 promoter-luciferase reporter plasmid after 24 h exposure at 260 and 520 nM. UCN-01 also increased the expression of the CDK inhibitor p27 protein after 24 h exposure at 260 and 520 nM. These results suggest that G1-phase accumulation induced by UCN-01 is associated with dephosphorylation of Rb and CDK2 proteins as well as induction of CDK inhibitors p21 and p27.
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PMID:G1 phase accumulation induced by UCN-01 is associated with dephosphorylation of Rb and CDK2 proteins as well as induction of CDK inhibitor p21/Cip1/WAF1/Sdi1 in p53-mutated human epidermoid carcinoma A431 cells. 910 51

7-hydroxystaurosporine (UCN-01) is a more selective protein kinase C inhibitor than staurosporine. UCN-01 exhibits antitumor activity in experimental tumor models and is presently in clinical trials. Our study reveals that human myeloblastic leukemia HL60 and K562 and colon carcinoma HT29 cells undergo internucleosomal DNA fragmentation and morphological changes characteristic of apoptosis after UCN-01 treatment. These three cell lines lack functional p53, and K562 and HT29 cells are usually resistant to apoptosis. DNA fragmentation in HT29 and K562 cells occurred after 1 day of treatment while it took less than 4 h in HL60 cells. Cycloheximide prevented UCN-01-induced DNA fragmentation in HT-29 cells, but not in HL60 and K562 cells, suggesting that macromolecular synthesis is selectively required for apoptotic DNA fragmentation in HT29 cells. UCN-01-induced DNA fragmentation was preceded by activation of cyclin B1/cdc2 kinase. Further studies in HL60 cells showed that UCN-01-induced apoptosis was associated with degradation of CPP32, PARP, and lamin B and that the inhibitor of caspases (ICE/CED-3 cysteine proteases), Z-VAD-FMK, and the serine protease inhibitor, DCI, protected HL60 cells from UCN-01-induced DNA fragmentation. However, only DCI and TPCK, but not Z-VAD-FMK, inhibited DNA fragmentation in the HL60 cell-free system, suggesting that serine protease(s) may play a role in the execution phase of apoptosis in HL60 cells treated with UCN-01. Z-VAD-FMK and DCI also inhibited apoptosis in HT29 cells. These data demonstrate that the protein kinase C inhibitor and antitumor agent, UCN-01 is a potent apoptosis inducer in cell lines that are usually resistant to apoptosis and lack p53 and that caspases and probably serine proteases are activated during UCN-01-induced apoptosis.
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PMID:7-Hydroxystaurosporine (UCN-01) induces apoptosis in human colon carcinoma and leukemia cells independently of p53. 926 Sep 9

When cells are exposed to ionizing radiation, they initiate a complex response that includes the arrest of cell cycle progression in G1 and G2, apoptosis and DNA repair. DNA is an important subcellular target of ionizing radiation, but oxydative damage to plasma membrane lipids initiates signal transduction pathways that activate apoptosis and that may play a role in cell cycle regulation. How is DNA damage converted into intracellular signals for cell cycle arrest? The ataxia telangectasia mutant (ATM) protein and/or the DNA-dependent protein kinase (DNA-PK), that are both activated by DNA damage, may initiate cell cycle arrest by activating the p53 tumor suppressor protein. The p53 protein acts as a transcription factor and regulates expression of several components implicated in pathways that regulate cell cycle progression. The best known, p21WAF1/CIP1 protein, is an inhibitor of cyclin-dependent kinases (CDK), a family of protein kinases known as key regulators of cell cycle progression. p21WAF1/CIP1 was shown to be able to inhibit several CDK, but is most effective toward G1/S cyclins. Other CDK inhibitors, p27KIP1 and p15INK4b are activated by irradiation and contribute to the G1 arrest. Moreover, radiation-induced G2 arrest was shown to require inhibitory phosphorylation of the kinase cdc2 via an ATM-dependent pathway. Mutations in cell cycle regulatory genes are common in human cancer and cell cycle regulatory deficiency can lead to increase resistance to ionizing radiation in cancer cells. The major function of p53-dependent G1 arrest may be elimination of cells containing DNA damage whereas G2 arrest following radiation has been shown to be important in protecting cells from death. Cell cycle checkpoints offer a new set of potential targets for chemotherapeutic compounds, especially the G2 checkpoint. Thus, abrogation of the G2 checkpoint with methylxanthines such as caffeine or protein kinase inhibitors such as staurosporine and UCN-01 (7-hydroxystaurosporine) was found to sensitize cells to ionizing radiation. These data did not lead to clinical applications, but confirm targeting of the G2 checkpoint may be an important strategy for cancer therapy.
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PMID:[Cell cycle regulation after exposure to ionizing radiation]. 1034 40

7-Hydroxystaurosporine (UCN-01), which was originally identified as a protein kinase C selective inhibitor, is currently in clinical trials as an anti-cancer drug. We previously showed that UCN-01 induced preferential G1-phase accumulation in tumor cells and this effect was associated with the retinoblastoma (Rb) protein and its regulatory factors, such as cyclin-dependent kinase 2 (CDK2) and CDK inhibitors p21Cip1/WAF1 and p27Kip1. We demonstrate here that G1-phase accumulation was induced by UCN-01 in Rb-proficient cell lines (WiDr and HCT116 human colon carcinomas and WI-38 human lung fibroblast), and it was accompanied by dephosphorylation of Rb. In addition, UCN-01-induced G1-phase accumulation was also demonstrated in a Rb-defective cell line (Saos-2 human osteosarcoma), but not in a simian virus 40 (SV40)-transformed cell line (WI-38 VA13). Apoptosis was induced by UCN-01 in the two Rb-deficient cell lines, but not in the other Rb-proficient cell lines. These observations suggest that G1-checkpoint function might be important for cell survival during UCN-01 treatment. In addition, there may be a UCN-01-responsive factor in the G1-checkpoint machinery other than Rb which is targeted by SV40. Further studies revealed a correlation between UCN-01-induced G1-phase accumulation and reduction of cellular CDK2 kinase activity. This reduction was strictly dependent on down-regulation of the Thr160-phosphorylated form of CDK2 protein, and coincided in part with up-regulation of p27Kip1, but it was independent of the level of the p21Cip1/WAF1 protein. These results suggest that G1-checkpoint function, including a CDK2-regulatory pathway, may be a significant determinant of the sensitivity of tumor cells to UCN-01.
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PMID:G1-checkpoint function including a cyclin-dependent kinase 2 regulatory pathway as potential determinant of 7-hydroxystaurosporine (UCN-01)-induced apoptosis and G1-phase accumulation. 1066 55

Five human cancer cell lines (MKN 45, HT-29, WiDr, PAN-3-JCK, and CRL 1420) were used to evaluate the antitumor spectrum of UCN-01, which suppressed the growth of these digestive cancer cell lines. A human pancreatic cancer xenograft (CRL 1420) and breast cancer xenograft (MX-1) were used to determine their sensitivity to UCN-01, in nude mice. UCN-01 significantly suppressed the tumor growth of CRL 1420 at a dose of 10 mg/kg in a schedule of (qd x 5) x 2, but was ineffective for MX-1. While p21 protein expression was induced by UCN-01 in both CRL 1420 and MX-1, an accumulation of dephosphorylated ppRb was observed only in CRL 1420, resulting in G1 block as detected by flow cytometric analysis. The CDK 2 activity of MX-1 was almost 6 times higher than that of CRL 1420, which might account for the resistance of MX-1 to UCN-01 in spite of the induction of p21 in this strain. We conclude that the determinant of sensitivity to UCN-01 lies in the balance of CDK 2 kinase activity and p21 protein induction.
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PMID:[Sensitivity of UCN-01 lies in the balance of CDK 2 kinase and p21]. 1094 25

The deoxyadenosine-resistant mouse leukemia L1210 cell line (Y8) has previously been shown to be more sensitive to apoptosis induced by DNA damaging agents and by protein synthesis inhibitors than the parental wild-type L1210 (WT) cells. These responses occur independently of p53 as both cell lines lack wild-type p53 function. Recent evidence suggests that a serine/threonine kinase is involved in the divergent cellular responses of the WT and Y8 cells. In the present study, the effects of 7-hydroxystaurosporine (UCN-01), a relatively specific serine/threonine kinase inhibitor, were examined in the WT and Y8 cells. Both cell lines were equally sensitive to the growth inhibitory effects of UCN-01. However, the Y8 cells accumulated in G0/G1 and became apoptotic. Apoptosis induced by UCN-01 in the Y8 cells was mediated by a caspase-3-like activity which could be partially blocked by Ac-DEVD-CHO, a caspase-3 inhibitor. UCN-01 did not alter the phosphorylation status of cdc2 nor cyclin B1 and cdc2 protein levels in either cell line.
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PMID:Altered sensitivity of deoxyadenosine-resistant mouse leukemia L1210 cells to apoptosis induced by 7-hydroxystaurosporine. 1099 94

The majority of hematopoietic malignancies have aberrancies in the retinoblastoma (Rb) pathway. Loss in Rb function is, in most cases, a result of the phosphorylation and inactivation of Rb by the cyclin-dependent kinases (cdks), main regulators of cell cycle progression. Flavopiridol, the first cdk modulator tested in clinical trials, is a flavonoid that inhibits several cdks with evidence of cell cycle block. Other interesting preclinical features are the induction of apoptosis, promotion of differentiation, inhibition of angiogenic processes and modulation of transcriptional events. Initial clinical trials with infusional flavopiridol demonstrated activity in some patients with non-Hodgkin's lymphoma, renal, prostate, colon and gastric carcinomas. Main side-effects were secretory diarrhea and a pro-inflammatory syndrome associated with hypotension. Phase 2 trials with infusional flavopiridol in CLL and mantle cell lymphoma, other schedules and combination with standard chemotherapies are ongoing. The second cdk modulator tested in clinical trials, UCN-01, is a potent protein kinase C inhibitor that inhibits cdk activity in vitro as well. UCN-01 blocks cell cycle progression and promotes apoptosis in hematopoietic models. Moreover, UCN-01 is able to abrogate checkpoints induced by genotoxic stress due to modulation in chk1 kinase. The first clinical trial of UCN-01 demonstrated very prolonged half-life (approximately 600 h), 100 times longer than the half-life observed in preclinical models. This effect is due to high binding affinity of UCN-01 to the human plasma protein alpha-1-acid glycoprotein. Main side-effects in this trial were headaches, nausea/vomiting, hypoxemia and hyperglycemia. Clinical activity was observed in patients with melanoma, non-Hodgkin's lymphoma and leiomyosarcoma. Of interest, a patient with anaplastic large cell lymphoma refractory to high-dose chemotherapy showed no evidence of disease after 3 years of UCN-01 therapy. Trials of infusional UCN-01 in combination with Ara-C or gemcitabine in patients with acute leukemia and CLL, respectively, have commenced. In conclusion, flavopiridol and UCN-01 are cdk modulators that reach biologically active concentrations effective in modulating CDK in vitro, and show encouraging results in early clinical trials in patients with refractory hematopoietic malignancies. Although important questions remain to be answered, these positive experiences will hopefully increase the therapeutic modalities in hematological malignancies.
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PMID:Development of cyclin-dependent kinase modulators as novel therapeutic approaches for hematological malignancies. 1124 75

Temozolomide (TMZ) produces O(6)-methylguanine in DNA, which in turn mispairs with thymine, triggering futile DNA mismatch repair (MMR) and ultimately cell death. We found previously that in p53-proficient human glioma cells, TMZ-induced futile DNA MMR resulted not in apoptosis but rather in prolonged, p53- and p21-associated G(2)-M arrest and senescence. Additionally, p53-deficient cells were relatively more TMZ resistant than p53-deficient glioma cells, which underwent only transient G(2)-M arrest before death by mitotic catastrophe. These results suggested that prolonged G(2)-M arrest might protect cells from TMZ-induced cytotoxicity. In the present study, we therefore focused on the mechanism by which TMZ induces G(2)-M arrest and on whether inhibition of such G(2)-M arrest might sensitize glioma cells to TMZ-induced toxicity. U87MG glioma cells treated with TMZ underwent G(2)-M arrest associated with Chk1 activation and phosphorylation of both cdc25C and cdc2. These TMZ-induced effects were inhibited by the Chk1 kinase inhibitor UCN-01. Although not in itself toxic, UCN-01 increased the cytotoxicity of TMZ 5-fold, primarily by inhibiting cellular senescence and increasing the percentage of cells bypassing G(2)-M arrest and undergoing mitotic catastrophe. In addition to enhancing TMZ-induced cytotoxicity in p53-proficient cells, UCN-01 also blocked TMZ-induced Chk1 activation and transient G(2)-M arrest in p53-deficient U87MG-E6 cells and similarly enhanced TMZ-induced mitotic catastrophe and cell death. Taken together, these results indicate that Chk1 links TMZ-induced MMR to G(2)-M arrest. Furthermore, inhibition of the cytoprotective G(2) arrest pathway sensitizes cells to TMZ-induced cytotoxicity and may represent a novel, mechanism-based means of increasing TMZ efficacy in both p53 wild-type and p53 mutant glioma cells.
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PMID:Abrogation of the Chk1-mediated G(2) checkpoint pathway potentiates temozolomide-induced toxicity in a p53-independent manner in human glioblastoma cells. 1147 24


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