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)

The human lymphoblastoid cell lines TK6 (normal p53) and WI-L2-NS or WTK1 (mutant p53) differ in sensitivity to killing and induction of gene mutations and chromosome aberrations by ionizing radiation. This may be related to decreased apoptosis in the cells with mutated p53, such that more damaged cells survive. We compared the response of the two cell types to various chemicals. First, to ensure that the thymidine kinase deficiency does not increase the sensitivity of TK6 tk+/- cells to mutagens, we demonstrated that they were not hypersensitive to aberration induction by altered DNA precursor pools or DNA synthesis inhibition, by aphidicolin (APC), methotrexate, hydroxyurea (HU), cytosine arabinoside and thymidine. TK6 cells were then compared with WI-L2-NS or WTK1 cells. With APC, HU, methyl methanesulfonate (MMS), ethyl nitrosourea (ENU) and etoposide (etop), TK6 cells had more apoptosis in the first two days after treatment. Fewer aberrations were seen in normal p53 TK6 cells than the mutant p53 WI-L2-NS cells, ranging from very little difference between the two cell types with MMS to very large differences with ENU and etop. For MMS and ENU we followed cultures for several days, and found that WI-L2-NS cells underwent delayed apoptosis 3 to 5 days after treatment, in parallel with published observations with ionizing radiation. WI-L2-NS cells also had a delayed increase in aberrations (up to 5 days post-treatment) when no aberrations remained in TK6 cells. Colony forming efficiency was measured for APC, MMS and ENU, and was greater in the p53 mutant cells. Our results show that normal p53 function is required for rapid and efficient apoptosis in these lymphoblastoid cells with DNA synthesis inhibitors, alkylating agents and a topoisomerase II inhibitor, and support the hypothesis that induced levels of aberrations are higher in p53 mutant cells because of a failure to remove damaged cells by apoptosis.
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PMID:Fewer chromosome aberrations and earlier apoptosis induced by DNA synthesis inhibitors, a topoisomerase II inhibitor or alkylating agents in human cells with normal compared with mutant p53. 963 70

Expression of 18 genes was examined at 8 different time points between 1 h and 28 days following cryogenic rat brain injury. The genes include thymidine kinase (TK), p53 tumor suppressor, c-fos, renin, myelin basic protein (MBP), proteolipid protein (PLP), transferrin, transferrin receptor, platelet-derived growth factor A (PDGF A), platelet-derived growth factor B (PDGF B), platelet-derived growth factor receptor alpha (PDGF alpha receptor), platelet-derived growth factor receptor beta (PDGF beta receptor), glial fibrillary acidic protein (GFAP), transforming growth factor-beta 1 (TGF-beta 1), basic fibroblast growth factor (bFGF), fibroblast growth factor receptor-1 (FGF-R1), insulin-like growth factor-1 (IGF-1), and somatostatin. Time courses of gene expression were determined for RNAs derived from hippocampus and cortex. Genes were divided into categories based upon those in which statistically significant changes in expression were first observed at or before 24 h (early genes) and those in which changes were first observed at or after 72 h (late genes). In the present model, many genes demonstrate elevated RNA levels in the cortex prior to hippocampus, following injury. RNAs transcribed from late genes tend to be elevated concurrently in cortex and hippocampus.
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PMID:Temporal changes in gene expression following cryogenic rat brain injury. 964 55

Two obstacles limiting the efficacy of nearly all cancer gene therapy trials are low gene transduction efficiencies and the lack of tumor specificity. Recently, a replication-competent, E1B-attenuated adenovirus (ONYX-015) was developed that could overcome these limitations, because it was capable of efficiently and selectively destroying tumor cells lacking functional p53. In an attempt to improve both the efficacy and safety of this approach, we constructed a similar adenovirus (FGR) containing a cytosine deaminase (CD)/herpes simplex virus type-1 thymidine kinase (HSV-1 TK) fusion gene, thereby allowing for the utilization of double-suicide gene therapy, which has previously been demonstrated to produce significant antitumor effects and potentiate the therapeutic effects of radiation. The FGR virus exhibited the same tumor cell specificity and replication kinetics as the ONYX-015 virus in vitro. Importantly, both the CD/5-FC and HSV-1 TK/GCV suicide gene systems markedly enhanced the tumor cell-specific cytopathic effect of the virus, and, as expected, sensitized tumor cells to radiation. By contrast, neither the FGR virus nor either suicide gene system showed significant toxicity to normal human cells. Both suicide gene systems could be used to suppress viral replication effectively, thereby providing a means to control viral spread. The results support the thesis that the three-pronged approach of viral therapy, suicide gene therapy, and radiotherapy may represent a powerful and safe means of selectively destroying tumor cells in vivo.
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PMID:A novel three-pronged approach to kill cancer cells selectively: concomitant viral, double suicide gene, and radiotherapy. 965 Jun 10

The phytoestrogen, genistein, is a naturally occurring isoflavone found in soy products. On a biochemical basis, genistein is a competitive inhibitor of tyrosine kinases and the DNA synthesis-related enzyme, topoisomerase-II (topo-II). Exposure of mammalian cells to genistein results in DNA damage that is similar to that induced by the topo-II inhibitor and chromosomal mutagen, m-amsa. In order to determine the potential genotoxicity of genistein, human lymphoblastoid cells which differ in the functional status of the tumor suppressor gene, p53, were exposed to genistein and the induction of micronuclei quantified by microscopic analysis. In addition, the mutant fraction at the thymidine kinase (tk) locus (both the normal-growth and slow-growth phenotypes) was determined by resistance to trifluorothymidine (TFT) and at the hypoxanthine phosphoribosyl transferase (hprt) locus by resistance to 6-thioguanine (6-TG). Flow cytometric analysis of the percentage of viable, apoptotic and degenerating cells was utilized to determine the rate and kinetics of cell death after genistein exposure. The detection of micronuclei in both cell lines indicated that genistein-induced damage had occurred in both AHH-1 tk+/- and L3. Linear regression analysis detected a significant increase in the number of 6-TG-resistant clones in both AHH-1 tk+/- (p53+/-) and L3 (p53+/+). A comparison of slopes revealed no difference between the lines. In contrast, a significant, concentration-dependent increase in the number of TFT-resistant clones with the slow-growth phenotype was detected in AHH-1 tk+/- (mutant p53), but not in L3 (wild-type p53). Cell death occurred primarily by apoptosis in both cell lines; however, a concentration-dependent decrease in the percentage of viable cells was detected immediately after exposure in L3, but not until 32 h after exposure in AHH-1 tk+/-. A comparison of the slopes of the concentration-response curves for the percentage of viable cells revealed no difference between the cell lines in the effect of genistein on cell viability. Our results may be interpreted that genistein is a chromosomal mutagen and that p53 functional status affects the recovery of chromosomal mutants, possibly by signalling cells into the apoptosis pathways.
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PMID:p53, mutations, and apoptosis in genistein-exposed human lymphoblastoid cells. 972 67

The mechanisms by which cytotoxic agents perturb the normal cell biology and cell cycle progression of cancer cells were explored using B16F10 cells genetically modified to express the Herpes Simplex Virus-thymidine kinase gene. Culture in the presence of the nucleoside analogue ganciclovir induced a profound morphological change that required entry of treated cells into S phase and was dependent on prenylated proteins such as those of the rho gene family. Cell cycle arrest occurred in late S phase or G2 phase due to the activation of the G2-M DNA damage checkpoint. This checkpoint control operated at the level of inhibition of the activity of Cdc2/cyclin B and occurred by two mechanisms: (a) p53-mediated up-regulation of p21CIP/WAF1 expression and its association with Cdc2/cyclin B; and (b) prevention of the dephosphorylation of tyrosine 15 of Cdc2. These events occurred in vitro and in vivo, and were shown to mediate bystander killing in this model. The mechanism of cell death seemed to be due to the irreversible cell cycle arrest at the G2-M checkpoint, rather than induction of apoptosis. These data link DNA damage checkpoints with cytoskeletal signaling pathways and the core cell cycle machinery and may represent a general mechanism of cytotoxicity of this class of nucleoside analogues.
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PMID:Irreversible G2-M arrest and cytoskeletal reorganization induced by cytotoxic nucleoside analogues. 973 95

The thymidine kinase locus (Tk1) in Tk(+/-)-3.7.2C mouse lymphoma cells is widely used to identify mutagenic agents. Because Trp53 (the mouse homolog of human TP53) is located with Tk1 on chromosome 11 and is critical in regulating cellular responses following exposure to DNA damaging agents, we wanted to determine if these mouse lymphoma cells harbor mutations in Trp53. Single-stranded conformation polymorphism (SSCP) analysis of PCR-amplified exons 4-9 of Trp53 indicated mutations in both exons 4 and 5. We sequenced exons 4-9 from isolated clones of Tk(+/-)-3.7.2C cells and a Tk-/- mutant (G4). Mutant G4 has two copies of the chromosome carrying the Tk1- allele and no copy of the chromosome carrying the Tk1+ allele and thus could establish linkage of the individual Trp53 and Tk1 alleles. DNA sequence analysis revealed no mutations in exons 6-9 in any Tk(+/-)-3.7.2C or G4 clones. As suggested by SSCP, there was a nonsense mutation in exon 4 at bp 301 (codon 101) in one Trp53 allele. Tk(+/-)-3.7.2C clones have both mutant and wild-type sequences at bp 301; G4 clones have wild-type exon 4 sequence. These data allow assignment of the Trp53 exon 4 mutated allele to chromosome 11 carrying the Tk1+ allele. The exon 4 mutation leads to a stop codon early in translation, thus functionally deleting the Trp53 allele on the Tk1(+)-bearing chromosome. As previously reported, we find a missense mutation in exon 5 at bp 517 (codon 173) in one Trp53 allele. Using the G4 clones we determined that the exon 5 mutation is linked to the Tk1- allele. Thus the Tk +/-(-)3.7.2C mouse lymphoma cells have two mutant Trp53 alleles, likely accounting for their rapid cell growth and contributing to their ability to detect the major types of mutational damage associated with the etiology of tumor development. This ability to integrate across the mutational events seen in the multiple stages of tumor development further supports the use of the assay in chemical and drug safety studies and its recommendation as part of the required screening battery for regulatory agency submissions.
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PMID:Identification and chromosomal assignment of two heterozygous mutations in the Trp53 gene in L5178Y/Tk(+/-)-3.7.2C mouse lymphoma cells. 980 Jan 87

Local gene transfer into the vascular wall offers a promising alternative to treat atherosclerosis-related diseases at cellular and molecular levels. Blood vessels are among the easiest targets for gene therapy because of novel percutaneous, catheter-based treatment methods. On the other hand, gene transfer to the artery wall can also be accomplished from adventitia, and in some situations intramuscular gene delivery is also a possibility. In most conditions, such as postangioplasty restenosis, only a temporary expression of the transfected gene will be required. Promising therapeutic effects have been obtained in animal models of restenosis with the transfer of genes for vascular endothelial growth factor, fibroblast growth factor, thymidine kinase, p53, bcl-x, nitric oxide synthase and retinoblastoma. Also, growth arrest homeobox gene and antisense oligonucleotides against transcription factors or cell cycle regulatory proteins have produced beneficial therapeutic effects. Angiogenesis is an emerging new target for gene therapy of ischemic diseases. In addition, hyperlipoproteinemias may be improved by transferring functional lipoprotein-receptor genes into hepatocytes of affected individuals. First experiences of gene transfer methods in the human vascular system have been reported. However, further studies regarding gene delivery methods, vectors and safety of the procedures are needed before a full therapeutic potential of gene therapy in vascular diseases can be evaluated.
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PMID:Vascular gene transfer for the treatment of restenosis and atherosclerosis. 981 1

We have hypothesized that adenoviral vectors might mediate gene transfer into cell lines derived from human lymphocytic malignancies, such as lymphoma, lymphocytic leukemia, and myeloma. A panel of 33 cell lines was studied for their ability to be transduced by an adenoviral (AD) vector encoding the Escherichia coli beta-galactosidase gene (AD-betagal). A cytochemical assay and a flow cytometry assay both demonstrated that a subset of lymphocytic cell lines can be efficiently transduced by adenoviral vectors. In particular, three of three anaplastic large cell lymphoma lines, two of two Hodgkin's disease cell lines, two of seven Burkitt's lymphoma cell lines, and three of five myeloma cell lines exhibited efficient gene transfer. The ability of an AD vector expressing the thymidine kinase (tk) gene from herpes simplex virus-1 (AD-tk) followed by ganciclovir (GCV) to kill 11 of these lymphocytic cell lines was studied. In eight of the cell lines tested, more than 68% of the cells were killed by AD-tk/GCV. Similar results were obtained using an adenoviral vector expressing the wild-type p53 tumor suppressor gene (AD-p53). Thus, AD-tk/GCV and AD-p53 both demonstrated efficient killing of these cell lines. These data document that adenoviral vectors are valuable reagents for the introduction of genes into selected lymphocytic cell lines. These data also suggest that adenoviral vectors might be useful for gene therapy of subsets of lymphocytic malignancy.
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PMID:Adenoviral vectors efficiently target cell lines derived from selected lymphocytic malignancies, including anaplastic large cell lymphoma and Hodgkin's disease. 981 92

Induced cell cycle delays were among the first described cellular responses to ionizing radiation (IR). To understand the sensitivity and the molecular events involved in the response to low doses of IR and to examine the role of p53 and its downstream effector p21Waf1, we measured changes in expression of genes postulated to be involved in the cellular response to IR. Expression levels were examined in normal human diploid fibroblasts irradiated and maintained in quiescent density-inhibited growth up to 24-48 h after exposure to X-ray doses as low as 0.1-0.3 Gy, which have negligible effects on cell survival. Among 31 genes analyzed, we observed down-regulation in response to IR of the mRNA levels of CDC2, cyclin A, cyclin B, thymidine kinase, topoisomerase IIalpha, and RAD51. A similar reduction in the expression levels of these genes occurred when irradiated cells were released from confluence and allowed to proliferate. This was not observed in cells in which p53 function was defective and up-regulation of p21Waf1 levels either did not occur (E6 transfected normal human fibroblasts and Li-Fraumeni fibroblasts) or was delayed (ataxia telangiectasia fibroblasts) after irradiation. Down-regulation was also absent in p21Waf1-null mouse embryo fibroblasts (MEFs) but occurred at a lower level in p53-null MEFs, due to slight increases in p21Waf1 levels by a p53-independent pathway. These findings indicate that the down-regulation of these cell cycle regulated genes in irradiated cells is p53-dependent and involves its effector p21Waf1. Although no down-regulation in the expression of genes involved in G2-M was observed in p53 or in p21Waf1-null MEFs, these cells showed a G2-M delay after irradiation, indicating that the expression levels of these genes does not regulate the G2-M delay.
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PMID:Regulation by ionizing radiation of CDC2, cyclin A, cyclin B, thymidine kinase, topoisomerase IIalpha, and RAD51 expression in normal human diploid fibroblasts is dependent on p53/p21Waf1. 983 Dec 41

The herpes simplex virus thymidine kinase gene (HSV-tk) was stably transfected into rat C6 glioma cells (C6tk) in order to characterize the mechanisms underlying cell toxicity induced in vitro by the guanosine analog ganciclovir (GCV). The results demonstrate the efficiency of the HSV-tk/GCV system in ablating most of the tumoral cells within 7 to 8 days of treatment with 20 mivroM GCV; however, a few cells still survive. C6tk cells arrest in the S phase of the cell cycle after 2 days of drug treatment before undergoing cell death. Microscopic analysis reveals dying cells with ultrastructural characteristics consistent with apoptosis; we cannot rule out, however, that necrotic cell death may also be occurring. The cytotoxicity induced by GCV is not associated with changes in the expression of p53 protein, suggesting that cell cycle arrest and cell death may occur through a p53-independent pathway. C6tk cells constitutively express Bcl-xL and Bax proteins; when exposed to GCV, Bcl-xL levels do not change but Bax accumulation is rapidly induced. These findings suggest that the balance between Bcl-xL and Bax proteins may be of importance in determining the sensitivity of tumoral cells to GCV.
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PMID:Increased bax expression is associated with cell death induced by ganciclovir in a herpes thymidine kinase gene-expressing glioma cell line. 1009 11


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