Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AT cells are extremely sensitive to ionizing radiation. Since the AT gene has homology to phosphatidylinositol 3 kinases (PI 3-kinases), wortmannin, a specific inhibitor of PI 3-kinase, was used to determine if PI 3-kinase activity regulates radiation sensitivity. Human and murine cells exposed to wortmannin alone did not display significant cytotoxicity. Wortmannin in combination with radiation was an effective radiosensitizer of murine NIH-3T3 fibroblasts, with a sensitizer enhancement ratio of 1.8 at 10% survival, and had a similar effect on the human tumor cell lines HeLa, SW480, and MCF-7. Wortmannin inhibited the induction of p53 DNA-binding activity by actinomycin D and radiation and blocked the transcriptional activation of a p53 CAT reporter gene by actinomycin D. Wortmannin radiosensitized both wild-type (NIH-3T3 and MCF-7) and mutant (SW480 and HeLa) p53 cells, indicating that p53 induction was not required for radiosensitization by wortmannin. The results suggest that a wortmannin-sensitive pathway, possibly involving PI 3-kinase activity, may regulate the response of the cells to DNA damage.
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PMID:The phosphatidylinositol 3-kinase inhibitor wortmannin sensitizes murine fibroblasts and human tumor cells to radiation and blocks induction of p53 following DNA damage. 854 74

The deoxyadenosine-resistant mouse leukemia L1210 cell line (Y8) has previously been shown to have phenotypic differences that appear unrelated to the altered properties observed at the level of ribonucleotide reductase (RR). In response to various stress factors, the parental wild-type (WT) L1210 cell line undergoes cell cycle arrest; Y8 cells become apoptotic. These responses are p53-independent. Cell cycle regulation also appears different between the two cell lines, suggesting that Y8 cells are more apoptotic because of alterations in their cell cycle compared to WT cells. In order to study the relationships between cell cycle regulation and apoptosis, the effects of 2-aminopurine (2-AP), wortmannin, and PD98059, were studied on WT and Y8 cells. 2-AP induced G2/M block in both WT and Y8 cells with differences in G0/G1 and S phase contents between the two cell lines. Wortmannin induced G0/G1 block in Y8 cells, while exhibiting no effect on WT cells. PD98059 had no effect on the cell cycle of either WT or Y8 cells. In response to each inhibitor, Y8 cells underwent apoptosis to a much greater extent than the parental WT cell line. These data suggest that the specific pathways that converge on the cell cycle are altered and may be involved in the differences between a tumor cell to block in cell cycle or to undergo apoptosis.
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PMID:Altered sensitivity of deoxyadenosine-resistant mouse leukemia L1210 cells to various kinase inhibitors. 1036 49

DNA-damaging agents induce phosphorylation of the p53 protein, resulting in its accumulation in the nucleus. To clarify the signal transduction pathway(s) involved in p53 protein accumulation in normal human embryo cells following X-irradiation, the effects of three protein kinase inhibitors were examined. Quercetin, an inhibitor of heat-shock response, dose dependently suppressed the p53 accumulation induced by X-rays at more than 100 microM. No suppression, however, was observed with calphostin-C, a specific inhibitor of protein kinase C, in the range of 0.05 to 0.25 microM. Wortmannin was the most potent inhibitor of p53 accumulation. Its suppressive effect appears within a few minutes of pretreatment with a dose of 25 microM, but posttreatment was less effective. Our findings suggest that PKC is not involved in X-ray-induced p53 accumulation in normal human embryo cells and that a wortmannin-sensitive pathway acts as a sensor of DNA damage.
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PMID:Effects of protein kinase inhibitors on the accumulation kinetics of p53 protein in normal human embryo cells following X-irradiation. 1040 75

Wortmannin is a potent inhibitor of phosphatidylinositol (PI) 3-kinase and PI 3-kinase-related proteins (e.g. ATM), but it does not inhibit the activity of purified calmodulin-dependent protein kinase II (CaMKII). In the present study, we compared the effects of wortmannin and the CaMKII inhibitor KN62 on the response of normal human dermal fibroblast cultures to gamma radiation. We demonstrate that wortmannin confers a phenotype on normal fibroblasts remarkably similar to that characteristic of cells homozygous for the ATM mutation. Thus wortmannin-treated normal fibroblasts exhibit increased sensitivity to radiation-induced cell killing, lack of temporary block in transition from G1 to S phase following irradiation (i.e. impaired G1/S checkpoint), and radioresistant DNA synthesis (i.e. impaired S phase checkpoint). Wortmannin-treated cultures display a diminished capacity for radiation-induced up-regulation of p53 protein and expression of p21WAF1, a p53-regulated gene involved in cell cycle arrest at the G1/S border; the treated cultures also exhibit decreased capacity for enhancement of CaMKII activity post-irradiation, known to be necessary for triggering the S phase checkpoint. We further demonstrate that KN62 confers a radioresistant DNA synthesis phenotype on normal fibroblasts and moderately potentiates their sensitivity to killing by gamma rays, without modulating G1/S checkpoint, p53 up-regulation and p21WAF1 expression following radiation exposure. We conclude that CaMKII is involved in the radiation responsive signalling pathway mediating S phase checkpoint but not in the p53-dependent pathway controlling G1/S checkpoint, and that a wortmannin-sensitive kinase functions upstream in both pathways.
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PMID:Effects of the protein kinase inhibitors wortmannin and KN62 on cellular radiosensitivity and radiation-activated S phase and G1/S checkpoints in normal human fibroblasts. 1057 51

Expression of the cyclin kinase inhibitor, p21, is regulated both transcriptionally and posttranscriptionally by the ubiquitin-proteasome degradation pathway. Recently, we reported that DNA damage is required for efficient p21 expression by demonstrating that enhanced p21 mRNA expression induced by DNA damage results in increased p21 protein, but enhanced p21 mRNA without DNA damage does not. In addition, we demonstrated that DNA damage suppressed the ubiquitination of p21. In this study, we analyze the link between p21 stabilization and DNA damage. Enhanced p21 protein expression in ML-1 cells resulting from 15 Gy gamma-irradiation was diminished by Wortmannin or LY294002 pretreatment of cells. However, the levels of p21 mRNA were not affected by inhibitor pretreatment. Wortmannin or LY294002 pretreatment reduces p53 expression after gamma-irradiation to a lesser degree than that of p21. In addition, we examined the involvement of DNA-PK, whose activity is inhibited by Wortmannin or LY294002, in p21 stabilization using the SCID fibroblast cell line and a DNA-PK targeting ML-1 cell line. Accumulation of p21 protein by gamma-irradiation was similar to that of DNA-PK intact cells and was reduced by Wortmannin or LY294002 pretreatment. Involvement of another DNA damage detecting enzyme, the ATM gene product, whose activity is also inhibited by Wortmannin or LY294002, was evaluated. ATM deficient cells induced p21 after gamma-irradiation, gamma-irradiation-induced p21 protein was diminished by pretreatment of cells with Wortmannin or LY294002. We conclude that the p21 stabilization mechanism functions after gamma-irradiation, was sensitive to Wortmannin or LY294002, and required neither DNA-PK nor ATM gene product for activity.
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PMID:Phosphatidylinositol 3-kinase inhibitors, Wortmannin or LY294002, inhibited accumulation of p21 protein after gamma-irradiation by stabilization of the protein. 1077 Oct 89

A senescence-like growth arrest is induced in mouse primary embryo fibroblasts by inhibitors of phosphoinositide 3-kinase (PI3K). We observed that senescence-like growth arrest is correlated with an increase in p27(Kip1) but that down-regulation of other cyclin-dependent kinase (CDK) inhibitors, including p15(INK4b), p16(INK4a), p19( INK4d), and p21(Cip1) as well as other negative cell cycle regulators such as p53 and p19(ARF), implies that this senescence-related growth arrest is independent of the activity of p53, p19(ARF), p16(INK4a), and p21(Cip1), which are associated with replicative senescence. The p27(Kip1) binds to the cyclin/CDK2 complexes and causes a decrease in CDK2 kinase activity. We demonstrated that ectopic expression of p27(Kip1) can induce permanent cell cycle arrest and a senescence-like phenotype in wild-type mouse embryo fibroblasts. We also obtained results suggesting that the kinase inhibitors LY294002 and Wortmannin arrest cell growth and induce a senescence-like phenotype, at least partially, through inhibition of PI3K and protein kinase B/Akt, activation of the forkhead protein AFX, and up-regulation of p27(Kip1)expression. In summary, these observations taken together suggest that p27(Kip1) is an important mediator of the permanent cell cycle arrest induced by PI3K inhibitors. Our data suggest that repression of CDK2 activity by p27(Kip1) is required for the PI3K-induced senescence, yet mouse embryo fibroblasts derived from p27(Kip1-/-) mice entered cell cycle arrest after treatment with LY294002. We show that this is due to a compensatory mechanism by which p130 functionally substitutes for the loss of p27(Kip1). This is the first description that p130 may have a role in inhibiting CDK activity during senescence.
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PMID:Inhibition of the phosphoinositide 3-kinase pathway induces a senescence-like arrest mediated by p27Kip1. 1079 51

Genistein, a natural isoflavone found in soybeans, exerts a number of biological actions suggesting that it may have a role in cancer prevention. We have previously shown that it potently inhibits OCM-1 melanoma cell proliferation by inducing a G(2) cell cycle arrest. Here we show that genistein exerts this effect by impairing the Cdc25C-dependent Tyr-15 dephosphorylation of Cdk1, as the overexpression of this phosphatase allows the cells to escape G(2) arrest and enter an abnormal chromatin condensation stage. Caffeine totally overrides the genistein-induced G(2) arrest, whereas the block caused by etoposide is not bypassed and that caused by adriamycin is only partially abolished. We also report that genistein activates the checkpoint kinase Chk2 as efficiently as the two genotoxic agents and that caffeine may counteract the activation of Chk2 by genistein but not by etoposide. In contrast, caffeine abolishes the accumulation of p53 caused by all the compounds. Wortmannin does not suppress the Chk2 activation in any situation, suggesting that the ataxia telangiectasia-mutated kinase is not involved in this regulation. Finally, unlike etoposide and adriamycin, genistein induces only a weak response in terms of DNA damage in OCM-1 cells. Taken together, these results suggest that the G(2) checkpoints activated by genistein and the two genotoxic agents involve different pathways.
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PMID:Distinct Chk2 activation pathways are triggered by genistein and DNA-damaging agents in human melanoma cells. 1080 72

DNA damage response pathways coordinate the cellular response to DNA damage. To investigate the roles of tumor suppressor genes in these pathways, human lymphoblastoid cells (wild-type, p53-/-, ATM-/-) were treated for 1 h with 0-3 microg/ml of the radiomimetic compound bleomycin (BLM), and cells treated in G(2) were analyzed for chromatid aberrations. BLM-induced aberration frequencies were significantly increased, to the greatest extent in the ATM-/- cells and, to a lesser extent, in the p53-/- cells compared to wild-type cells. These observations are consistent with p53 and ATM acting in a damage response pathway activated by DNA strand breaks. The consequences of disrupting this pathway were further investigated by studies using wortmannin, a PI-3 kinase and DNA repair inhibitor. Wortmannin significantly increased the BLM-induced aberration frequencies in all but the ATM-/- cells, elevating the sensitivity of p53-/- cells to ATM-/- levels and that of wild-type cells to intermediate levels. These differential sensitivities suggest that the ATM phenotype is the result of dual cellular defects, one involving p53 and the other a wortmannin-sensitive component. Similar studies in Brca1+/- and Brca2+/- human lymphoblasts showed no increased sensitization to BLM in the absence of inhibitor, and differential sensitization by wortmannin. To determine if there was any substrate specificity for p53- and ATM-mediated DNA damage responses, chromatid aberrations were assessed in wild-type, p53-/-, and ATM-/- cells exposed to 0-0.4 microg/ml neocarzinostatin (NCS) for 1 h. In contrast to results with BLM, the p53-/- cells exhibited a low sensitivity to NCS-induced aberrations, similar to wild-type, while ATM-/- cells remained highly sensitive. This suggests that the response to BLM- and NCS-induced lesions involves different mechanisms.
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PMID:Increased sensitivity to chromatid aberration induction by bleomycin and neocarzinostatin results from alterations in a DNA damage response pathway. 1100 7

The purpose of this paper is to investigate the effect of wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), on TP53 (formerly known as p53) signal transduction initiated by ionizing radiation and radiosensitization in isogenic derivatives of human glioblastoma cells differing in TP53 status. Wortmannin inhibited the accumulation of TP53 and CDKN1A (formerly known as WAF1) after 6 Gy irradiation in A-172/neo cells bearing wild-type TP53. In A-172/Trp248 cells carrying mutant TP53, X-rays induced no significant accumulation of TP53 and slight increase of CDKN1A. There were, consequently, little differences in the expression of TP53 and CDKN1A between A-172/Trp248 cells exposed to 6 Gy alone and wortmannin plus 6 Gy. However, wortmannin sensitized both A-172/neo and A-172/Trp248 cells to radiation. These studies indicate that wortmannin inhibits TP53 upregulation, but this suppression does not account for the radiosensitization by this drug. These results indicate that inhibitors of PI3K-related kinases may present a new class of radiosensitizers, regardless of the TP53 status of tumor cells.
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PMID:Wortmannin sensitizes human glioblastoma cell lines carrying mutant and wild type TP53 gene to radiation. 1109 Sep 62

Arsenic compounds are potent human carcinogens. Accumulated evidence has shown that arsenite-induced cytogenetic alterations are associated with the carcinogenicity of arsenic. Because p53 plays a guarding role in maintaining genome integrity and accuracy of chromosome segregation, the mechanistic effects of arsenite on p53 activation were analyzed. In the present study, arsenite-induced DNA strand breaks were confirmed by alkaline single-cell gel electrophoresis (comet assay) in human fibroblast (HFW) cells. Accompanying the appearance of DNA strand breaks was a significant accumulation of p53 in arsenite-treated HFW cells, as demonstrated by immunoblotting and immunofluorescence techniques. p53 downstream proteins, such as p21 and the human homologue of murine double minute-2, were also significantly induced by arsenite treatment. Cell cycle retardation and G2-M arrest were observed in 5-bromo-2'-deoxyuridine pulse-labeled HFW cells by flow cytometry. Wortmannin, an inhibitor of phosphatidylinositol 3-kinases, inhibited arsenite- or X-ray irradiation-induced p53 accumulation but did not alter UV irradiation- or N-acetyl-Leu-Leu-norleucinal-induced p53 accumulation. p53 phosphorylation on serine 15 was also confirmed by immunoblotting technique in arsenite- and X-ray-treated HFW cells but was not observed in UV- or N-acetyl-Leu-Leu-norleucinal-treated HFW cells. These results suggest the involvement of a phosphatidylinositol 3-kinase-related protein kinase in arsenite-induced p53 accumulation. For confirmation, we demonstrated that arsenite treatment, similar to X-ray irradiation, did not induce p53 accumulation in GM3395 fibroblasts derived from a patient with ataxia telangiectasia. In contrast, UV irradiation did cause p53 accumulation in these cells. Together, these findings infer that arsenite-induced DNA strand breaks may lead to p53 phosphorylation and accumulation through an ataxia telangiectasia mutated-dependent pathway in HFW cells.
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PMID:Arsenite induces p53 accumulation through an ATM-dependent pathway in human fibroblasts. 1110 96


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