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)

Amifostine (AMF), a phosphorylated aminothiol, has been used to treat myelodysplastic syndrome (MDS), where it produces a stimulatory effect on hematopoiesis in bone marrow. To determine if AMF also produced a direct effect on human MDS cells, we planned a study to evaluate the effect of a continuous exposure to AMF on a human MDS cell line. AMF was shown to have a growth-inhibitory effect on MDS cells, with an IC(50) of 14 microM after a 5 day exposure. Cell cycle analysis revealed that a 5 day exposure to 20 microM AMF increased the percentage of cells in G0/G1 and this was accompanied by a decrease in the percentage of cells in S phase. Cytoflorometric and agarose-gel electrophoretic analysis revealed that this effect correlated with cell membrane alterations and DNA fragmentation consistent with an induction of apoptosis without affecting the expression of p53 protein or inducing any lymphoid or myeloid differentiation in the MDS cell line. We conclude that the continuous exposure of a human MDS cell line to AMF is cytotoxic and associated with an induction of apoptosis independent of alterations in p53 expression.
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PMID:Amifostine cytotoxicity and induction of apoptosis in a human myelodysplastic cell line. 1078 87

Many p53 mutants found in human cancer have an altered ability to bind DNA and transactivate gene expression. Re-expression of functional p53 in cells in which the endogenous TP53 gene is inactivated has been demonstrated to restore a non-tumorigenic phenotype. Pharmacological modulation of p53 mutant conformation may therefore represent a mechanism to reactivate p53 function and consequently improve response to radio- and chemotherapy. We have recently reported that the radio- and chemoprotector Amifostine (WR2721, Ethyol) activates wild-type p53 in cultured mammalian cells. In the present study, we have used a yeast functional assay to investigate the effect of WR2721 on the transcriptional activity of p53. WR2721 restored this activity in a temperature-sensitive mutant V272M (valine to methionine at codon 272) expressed at the non-permissive temperature and it also partially restored the transcriptional activity of several other conformationally flexible p53 mutants. The results indicate that the yeast functional assay may be used to identify compounds that modulate p53 activity, with potential therapeutic implications.
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PMID:Amifostine (WR2721) restores transcriptional activity of specific p53 mutant proteins in a yeast functional assay. 1142

Human lymphocytes, p53 protein-deficient acute promyelocytic leukemia cell line HL-60, murine pro-B lymphoid cell line BaF3 and its TEL/ABL-transformed clone cells were exposed to idarubicin with and without pre-treatment with amifostine. Idarubicin at 0.5-5 microM evoked DNA damage measured by the Comet assay. Amifostine at 14 mM decreased DNA-damaging effect of idarubicin in human lymphocytes and BaF3 cells, but increased the effect in TEL/ABL-transformed cells. Amifostine had no influence on the action of idarubicin in HL-60 cells. Our results suggest that the reaction of the cell to DNA damage may contribute to its diverse response to amifostine combined with anticancer drugs and that p53 and fusion tyrosine kinases may be involved in this diversity.
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PMID:Amifostine differentially modulates DNA damage evoked by idarubicin in normal and leukemic cells. 1244 81

Amsacrine is an acridine derivative drug applied in haematological malignancies. It targets topoisomerase II enhancing the formation of a cleavable DNA-enzyme complex and leading to DNA fragmentation in dividing cancer cells. Little is known about other modes of the interaction of amsacrine with DNA, by which it could affect also normal cells. Using the alkaline comet assay, we showed that amsacrine at concentrations from the range 0.01 to 10 microM induced DNA damage in normal human lymphocytes, human promyelocytic leukemia HL-60 cells lacking the p53 gene and murine pro-B lymphoid cells BaF3 expressing BCR/ABL oncogene measured as the increase in percentage tail DNA. The effect was dose-dependent. Treated cells were able to recover within a 120-min incubation. Amifostine at 14 mM decreased the level of DNA damage in normal lymphocytes, had no effect on the HL-60 cells and potentiated the DNA-damaging effect of the drug in BCR/ABL-transformed cells. Vitamin C at 10 and 50 microM diminished the extent of DNA damage in normal lymphocytes, but had no effect in cancer cells. Pre-treatment of the cells with the nitrone spin trap, N-tert-butyl-alpha-phenylnitrone or ebselen, which mimics glutathione peroxidase, reduced the extent of DNA damage evoked by amsacrine in all types of cells. The cells exposed to amsacrine and treated with endonuclease III and 3-methyladenine-DNA glycosylase II, the enzymes recognizing oxidized and alkylated bases, respectively, displayed greater extent of DNA damage than those not treated with these enzymes. The results obtained suggest that free radicals may be involved in the formation of DNA lesions induced by amsacrine. The drug can also methylate DNA bases. Our results indicate that the induction of secondary malignancies should be taken into account as diverse side effects of amsacrine. Amifostine may potentate DNA-damage effect of amsacrine in cancer cells and decrease this effect in normal cells and Vitamin C can be considered as a protective agent against DNA damage in normal cells.
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PMID:Free radical scavengers can differentially modulate the genotoxicity of amsacrine in normal and cancer cells. 1254 80

To determine the role of p53 protein on the cellular effects of amifostine, we used molecularly engineered HCT116 colon cancer cells in which the p53 gene was inactivated by targeted homologous recombination or p53 protein was degraded by high-level expression of papillomavirus E6 protein. Amifostine induced a G1 arrest and protected against paclitaxel toxicity in p53-proficient but not in p53-deficient cells. In the absence of p53 protein, amifostine enhanced the cytotoxicity of paclitaxel. In addition, treatment of HCT116 cells with amifostine alone resulted in apoptotic cell death. Compared with p53-deficient cells, p53-proficient cells exhibited low-level resistance to amifostine-induced apoptosis. Amifostine induced the expression of p53 protein in p53-proficient cells and the expression of p21 protein in both p53-proficient and -deficient cells. These findings indicate that amifostine-induced G1 arrest and cytoprotection are mediated via a pathway that is dependent on p53 protein and that amifostine-induced expression of p21 protein is not sufficient to sustain a G1 arrest or to mediate cytoprotection. In addition, these findings identify p53 protein as a mechanism of resistance to amifostine-induced apoptosis.British
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PMID:p53 protein regulates the effects of amifostine on apoptosis, cell cycle progression, and cytoprotection. 1261 86

Specific radioprotection of normal tissue represents a promising approach to improve radiotherapy. The ultimate feature of a normal tissue selective radioprotector is that tumor tissue is excluded from protection. Radioprotectors of the current generation, such as Ethyol, are not explicit normal tissue specific. In contrast, the Bowman Birk protease inhibitor, which is known to prevent in vitro and in vivo radiation-induced carcinogenesis, was found to be normal tissue specific. Moreover, the molecular restrictions for this specificity were identified. The radioprotective effect is dependent upon the presence of a functional wt. TP53. Since a high amount of tumors have lost TP53 function during tumor development, the clinical application of BBI to protect normal tissue from radiation damage would effectively improve the therapeutic outcome of radiation therapy. We succeeded to identify stimulation of DNA-repair mechanisms, such as nucleotide excision repair (NER) and nonhomologous end joining (NHEJ), as molecular mode of action. These results are in good agreement with the observations that BBI concomitantly exhibits anticarcinogenic effect and radioprotective effects. Taken together, BBI is recommended as a radioprotector for normal tissue expressing wild type TP53 during treatment of tumors characterized by a mutant TP53.
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PMID:Radioprotection of normal tissue to improve radiotherapy: the effect of the Bowman Birk protease inhibitor. 1287 Oct 82

Amifostine is used as a cytoprotective agent in cancer treatments. Amifostine protects from apoptosis in some models and has been used as hematopoiesis stimulator in myeloid malignancies. As the apoptosis induced by many antitumoral agents is mediated by p53, we studied the effect of amifostine on p53-mediated apoptosis. We used human myeloid leukemia K562 and NB4 cells expressing the temperature-conditional p53-Val(135) mutant. Both cell lines undergo apoptosis at 32 degrees C due to the presence of p53 in wild-type conformation. We found that amifostine dramatically reduced apoptosis by p53 in both cell lines, as assessed by cell morphology, annexin V binding, fraction of sub-G(1) cells, and DNA laddering. To explore the mechanism responsible for this apoptosis protection, we tested the effect of amifostine on p53 transcriptional activity. We found that amifostine reduced p53-mediated transactivation of target promoters in NB4 and K562. Macroarray analysis confirmed that several p53 target genes as p21(Waf1), mdm2, gadd45, pig8, and pig3 were down-regulated at the mRNA level by amifostine in NB4 and K562. Also, c-myc was up-regulated by amifostine in K562 in the presence of p53, consistently with the impairment of p53-mediated apoptosis exerted by c-Myc in these cells. We conclude that amifostine impairs p53-dependent apoptosis of myeloid leukemia cells by reducing the activation of apoptosis-related genes. Our results open the possibility that amifostine could reduce the effectiveness of antitumoral treatments when it is dependent on active p53.
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PMID:Amifostine impairs p53-mediated apoptosis of human myeloid leukemia cells. 1455 8

The underlying primary damage to the seminiferous epithelium caused by chemotherapeutic regimens at childhood is largely unknown. The present investigation was designed to identify acute cytotoxic events in the testis caused by a single dose of doxorubicin. Male rats at 6, 16, and 24 days of age were injected with doxorubicin (3 mg/kg, i.p.) or vehicle (saline) alone and 24 and 48 hours later, the germ cell types and apoptotic cells in the seminiferous epithelium were examined. As indicated by microscopy and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling staining, an 8-fold increase in the number of apoptotic germ cells in the testes of 6-day-old rats was observed 48 hours after doxorubicin treatment. Spermatogonia migrating to the basement membrane were the primary cell type undergoing this induced apoptosis. A single dose of amifostine (200 mg/kg) administered i.p. 15 minutes before injection of doxorubicin provided no protection against this enhanced apoptosis. Under the same conditions, testicular levels of p53 and activated caspase 8 were elevated, whereas the level of murine double minute-2 was lowered. In contrast, doxorubicin treatment did not result in any significant change in the physiologic, stage-specific germ cell apoptosis occurring in the testes of 16- and 24-day-old rats. These observations suggest that the initiation phase of spermatogenesis is highly sensitive to doxorubicin-induced apoptosis. Gonocytes and early spermatogonia are the cell types that are vulnerable to this p53-trigged apoptosis, which results in a decrease in the size of the pool of germ-line stem cells. Amifostine fails to protect the germ cells against this cytotoxic insult.
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PMID:Doxorubicin induces apoptosis in germ line stem cells in the immature rat testis and amifostine cannot protect against this cytotoxicity. 1626 25

Adenoviral delivery of the p53 gene is a potential therapeutic approach for the treatment of lung cancer. Furthermore, amifostine is a cytoprotective agent and recent reports have described its potentiation of chemotherapy's antitumor activity in lung cancer. Therefore, we wished to investigate the ability of amifostine both alone and in combination with p53-based therapy to induce apoptosis, and to understand the mechanisms by which this apoptosis occurs. Using p53 null and wild-type p53 human lung cancer cells and normal human bronchial epithelial cells, we evaluated the effects of amifostine on proliferation and apoptosis. We then analyzed Adp53 in combination with amifostine and performed isobologram analysis. Expression of p53, p21(WAF1), Bax, Bak, bcl-2, as well as total and phosphorylated Cdc2 in the absence and presence of olomoucine, a phosphorylated Cdc2 kinase inhibitor, was then determined. Amifostine-induced apoptosis in human lung cancer cells in a dose-dependent fashion. The combination of amifostine and Adp53 significantly enhanced, with a supra-additive effect, the inhibition of proliferation of lung cancer cells. This enhancement of apoptosis by amifostine was associated with activation of p53 and dephosphorylation of Cdc2 proteins. Notably, olomoucine effectively prevented amifostine and/or Adp53-induced Cdc2 kinase activation and subsequent apoptosis. Our data shows that amifostine alone can induce apoptosis of human lung cancer cells, and that the combination of Adp53 with amifostine resulted in significantly higher levels of apoptosis. In addition, it appears that Cdc2 kinase plays an important role in the induction of apoptosis by amifostine and Adp53.
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PMID:Induction of apoptosis in human lung cancer cells following treatment with amifostine and an adenoviral vector containing wild-type p53. 1662 27

The p53 gene is often mutated during cancer development. Frequency and functional consequences of these mutations vary in different tumor types. We analysed conformation and temperature dependency of 23 partially inactivating temperature-dependent (td) p53 mutants derived from various human tumors in yeast. We found considerable differences in transactivation capabilities and discriminative character of various p53 mutants. No correlations in transactivation rates and conformations of the td p53 proteins were detected. Amifostine-induced p53 reactivation occurred only in 13 of 23 td mutants, and this effect was temperature dependent and responsive element specific. The most of the p53 mutations (10/13) reactivated by amifostine were located in the part of the p53 gene coding for hydrophobic beta-sandwich structure of the DNA-binding domain.
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PMID:Analysis of transactivation capability and conformation of p53 temperature-dependent mutants and their reactivation by amifostine in yeast. 1772 67


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