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)

Squamous intraepithelial lesions (SIL) and invasive cancer of the uterine cervix are thought to be a series of lesions derived from normal cervical squamous tissue. Infection by high risk human papillomavirus (HPV) and integration of viral DNA may initially lead normal cervical cells to become pre-malignant cells in SIL and result in cervical malignancies later on. High risk HPVs, including types 16 and 18, produce a viral protein, E6, which is required for viral replication in host cells. The E6 protein is able to bind to host p53 causing inactivation of its function through the mechanism of ubiquitin-dependent degradation. It has recently been reported that the extent of p53 dysfunction caused by HPVs depends on the status of a polymorphism at codon 72 of p53, Pro or Arg. In that study, it was demonstrated that a patient homozygous for the Arg allele had about a seven times higher risk of developing cervical cancer than a patient homozygous for Pro. In an attempt to confirm this result and elucidate whether this allelic deviation of the Arg genotype seen in invasive cervical cancer occurs in the pre-malignant lesion SIL, we analyzed 219 SIL and 101 invasive cancer samples from Japanese patients using a PCR-based assay. Samples from 88 SIL and 76 invasive cancers were identified as HPV-infected samples and used for further analyses. In these, the frequencies of Arg homozygotes were 31.8, 33.0 and 36.8% in controls, SIL and invasive cancer, respectively. The distributions of the different alleles of codon 72 (Pro/Pro, Pro/Arg and Arg/Arg) did not show significant differences between either control and SIL groups or control and invasive cancer groups. Also, no difference in the frequency of Arg/Arg genotype was detected even between the control and HSIL groups or control and invasive cancer infected with high risk HPVs groups. In conclusion, there was no obvious relationship between the Arg genotype at codon 72 of p53 and predisposition to HPV-associated cervical neoplasia.
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PMID:Codon 72 polymorphism of p53 as a risk factor for patients with human papillomavirus-associated squamous intraepithelial lesions and invasive cancer of the uterine cervix. 1046 18

Herpes simplex virus type 1 is capable of inhibiting host cell DNA synthesis following lytic infection. However, the mechanism and nature of potential effects on cell cycle progression have not been described. In this report, we characterize the dysregulation of the cell cycle following infection with the replication-incompetent virus d106, where immediate-early gene expression is restricted to infected-cell polypeptide 0 (ICP0) and the expression of all other viral genes is dramatically reduced or is not observed. Infection with d106 resulted in the accumulation of cells in both the G(1)/S and G(2)/M compartments, consistent with cell cycle arrest at both checkpoints. The isogenic variant d109, which does not express any viral proteins, failed to induce this phenotype, suggesting that the expression of ICP0 is crucial for cell cycle arrest. Analysis of global cellular gene expression patterns following infection with d106 and d109 revealed that a relatively small subset of cellular genes were induced as a consequence of ICP0 expression. A number of these genes induced in the presence of ICP0 are classically considered p53-responsive genes, including p21, gadd45, and mdm-2. However, infection with d106 of cells with both alleles of p53 deleted resulted in the same cell cycle arrest phenotype and similar cellular gene expression patterns, suggesting that the expression of ICP0 results in cell cycle arrest potentially via p53-dependent and p53-independent mechanisms. In addition, it was found that the effects of infection with d106 on viral and cellular gene expression were similar to the effects observed following treatment of cells with the histone deacetylase inhibitor trichostatin A.
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PMID:Perturbation of cell cycle progression and cellular gene expression as a function of herpes simplex virus ICP0. 1048 75

Specificity is an essential prerequisite for cancer gene therapy. Recently we described that apoptin, a protein of 121 amino acids which is derived from the chicken anemia virus, induces programmed cell death or apoptosis in transformed and malignant cells, but not in normal, diploid cells (Danen-van Oorschot AAAM et al, Proc Natl Acad Sci USA 1997; 94: 5843-5847). This protein has an intrinsic specificity that allows it to selectively kill tumor cells, irrespective of the p53 or Bcl-2 status of these cells. Hence, it is attractive to explore the use of the apoptin gene for therapeutic applications, viz cancer gene therapy. In this paper, we describe the generation and characterization of an adenovirus vector, AdMLPvp3, for the expression of apoptin. Despite the fact that apoptin ultimately induces apoptosis in the helper cells, which are transformed by the adenovirus type 5 early region 1 (E1), the propagation kinetics and yields of AdMLPvp3 are similar to those of control vectors. Infection with AdMLPvp3 of normal rat hepatocytes in cell culture did not increase the frequency of apoptosis. In contrast, in the hepatoma cell lines HepG2 and Hep3b, infection with AdMLPvp3, but not with control vectors, led to a rapid induction of programmed cell death. Experiments in rats demonstrated that AdMLPvp3 could be safely administered by intraperitoneal, subcutaneous or intravenous injection. Repeated intravenous doses of AdMLPvp3 were also well tolerated, indicating that the apoptin-expressing virus can be administered without severe adverse effects. In a preliminary experiment, a single intratumoral injection of AdMLPvp3 into a xenogeneic tumor (HepG2 cells in Balb/Cnu/nu mice) resulted in a significant reduction of tumor growth. Taken together, our data demonstrate that adenovirus vectors for the expression of the apoptin gene may constitute a powerful tool for the treatment of solid tumors.
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PMID:Specific tumor-cell killing with adenovirus vectors containing the apoptin gene. 1050 14

Infection with human papillomavirus type 16 (HPV-16) confers a high risk for the development of cervical neoplasia. Variants of this virus may interact differentially with host genetic factors, possibly altering the disease course. Thus, HPV-16 E6 variants may differ in their ability to degrade p53 whereas the polymorphic p53 alleles may provide more or less susceptible substrates for the viral oncogene product. Also, E6 variants may differ in immunogenicity by generating different peptides for presentation by polymorphic HLA molecules to specific T cells. This study examines HPV-16 E6 sequence variation in cervical carcinomas from the UK and its relationship to polymorphism of HLA and p53 and to clinical parameters. Sequence analysis of the HPV-16 E6 ORF from 77 tumour biopsies detected the viral prototype sequence in 38% of cases. The most common variation detected was a T to G transition at base pair 350, resulting in an amino acid change from a leucine to a valine. Overall, the frequencies of 350T and 350G sequences were similar (49. 4% and 50.6% respectively). Other mutations of lower frequencies were detected together with and independently of 350G. HPV-16 E6 sequence variation at base pair 350 did not correlate with HLA genotype or clinical outcome. There was no difference in the distribution of p53 proline and arginine alleles between HPV-16-positive cervical carcinoma patients and local controls, and no influence on clinical outcome; however, there was a trend for an increased frequency of p53 arginine homozygotes among the 350T carcinoma patients.
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PMID:Human papillomavirus type 16 E6 variants in cervical carcinoma: relationship to host genetic factors and clinical parameters. 1056 56

ONYX-015 is an E1B-deleted adenovirus that replicates in and causes lysis of p53-deficient cancer cells selectively. To study the efficiency of intratumoral (i.t.) spread by ONYX-015, we infected specific fractions of tumor cells (two p53-deficient tumor lines and one p53 functional line) in vitro before subcutaneous inoculation into nude mice. Infection of as few as 5% of p53- tumor cells prevented tumor development in all cases; infection of 1% of p53- tumor cells resulted in significant growth inhibition but did not prevent tumor formation. In contrast, infection with ONYX-015 had no significant effect on p53+ tumor formation. These data suggested that replication-dependent tumor cell lysis and spread was occurring, but that tumor destruction might be improved by increasing i.t. virus distribution. Two treatment parameters were then varied to determine whether virus distribution, and consequently efficacy, could be improved. Divided i.t. injections of virus were more efficacious than a single injection of the same total dose. Likewise, increasing the volume of the viral suspension for i.t. injection allowed better distribution within the tumor mass and increased efficacy. These results have implications for the treatment of cancer patients with viral agents.
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PMID:Efficacy of a replication-competent adenovirus (ONYX-015) following intratumoral injection: intratumoral spread and distribution effects. 1060 46

Transcription of the p53 gene can regulate progression of apoptosis in a wide variety of tissues. Three categories of human hepatocyte culture have been used to show the initiation of apoptosis after treatment with p53-bearing adenovirus. Chang liver cells are derived from normal liver tissue and express native p53, whereas hepatocellular carcinoma (HCC)-derived cell lines were Hep3B (p53-deleted) and PLC/PRF/5 (p53-mutant). Cultures were infected with Ad-p53 (15 particles per cell; 36 hours), and after treatment, morphological changes in all cell categories were observed by electron microscopy. Infection was evident in the cytoplasm of all treated cell types: after entry across the plasma membrane viruses translocated and came to rest surrounding and adjacent to nuclei, cytoplasm proximal to nuclear membranes became dense with virus- and membrane-derived debris, but intact viruses did not enter nuclei. Apoptosis, recognized morphologically by characteristic chromatin and cytoplasmic condensation, occurred more frequently in HCC-derived cells, and the ultimate fate of apoptotic bodies was phagocytosis and degradation by neighboring cells.
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PMID:Detection of adenovirus and initiation of apoptosis in hepatocellular carcinoma cells after Ad-p53 treatment. 1073 44

Two p53-related genes, p73 and p51, were recently identified as structural homologues of the p53 tumor suppressor gene, suggesting that the roles of these two genes may be similar to those of p53, including growth suppression and induction of apoptosis. Here we show that introduction of p73 or p51 cDNAs into cultured human cancer cells suppressed colony formation in the presence of G418. We then examined the ability of various isoforms of p73 and p51 to activate transcription of a reporter gene. This assay showed that p73beta and p51A activated transcription through a consensus p53 binding sequence, while p73alpha and p51B isoforms minimally transactivated the p53 reporter gene. To characterize further the biological functions of the p53-related genes, we constructed recombinant adenoviruses containing the p73 and p51 cDNAs. Ad-p73beta and Ad-p51A induced endogenous p21 gene expression more effectively than Ad-p73alpha and Ad-p51B, respectively. To evaluate the mode of cell death induced by p53-related genes, Ad-p73 and Ad-p51 were used to infect human cancer cells. Infection of Ad-p73beta, Ad-p51A or Ad-p51B resulted in DNA fragmentation in a subset of cancer cell lines more efficiently than did infection of Ad-p53. We then examined the combined effect of each p53-related gene and the E1A oncogene in the induction of apoptosis. The E1A oncogene cooperated with p51 as well as p53 to induce apoptosis, while p73 resulted in a weak induction of apoptosis by E1A. Overall, apoptosis induction by p51B and p73alpha isoforms may be due to mechanisms other than transcriptional activation of p53-target genes. Our results suggest that p53-related genes are both similar to and different from p53 in their pathways leading to growth suppression.
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PMID:Adenovirus-mediated transfer of p53-related genes induces apoptosis of human cancer cells. 1076 4

Productive high-titer infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile reverse transcripts and lack of viral progeny formation. An interplay between Tat and p53 has previously been reported, where Tat inhibited the transcription of the p53 gene, which may aid in the development of AIDS-related malignancies, and p53 expression inhibited HIV-1 long terminal repeat transcription. Here, by using a well-defined and -characterized stress signal, gamma irradiation, we find that upon gamma irradiation, HIV-1-infected cells lose their G(1)/S checkpoints, enter the S phase inappropriately, and eventually apoptose. The loss of the G(1)/S checkpoint is associated with a loss of p21/Waf1 protein and increased activity of a major G(1)/S kinase, namely, cyclin E/cdk2. The p21/Waf1 protein, a known cyclin-dependent kinase inhibitor, interacts with the cdk2/cyclin E complex and inhibits progression of cells into S phase. We find that loss of the G(1)/S checkpoint in HIV-1-infected cells may in part be due to Tat's ability to bind p53 (a known activator of the p21/Waf1 promoter) and sequester its transactivation activity, as seen in both in vivo and in vitro transcription assays. The loss of p21/Waf1 in HIV-1-infected cells was specific to p21/Waf1 and did not occur with other KIP family members, such as p27 (KIP1) and p57 (KIP2). Finally, the advantage of a loss of the G(1)/S checkpoint for HIV-1 per se may be that it pushes the host cell into the S phase, which may then allow subsequent virus-associated processes, such as RNA splicing, transport, translation, and packaging of virion-specific genes, to occur.
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PMID:Loss of G(1)/S checkpoint in human immunodeficiency virus type 1-infected cells is associated with a lack of cyclin-dependent kinase inhibitor p21/Waf1. 1079 78

Infection with hepadnaviruses and exposure to aflatoxin B1 (AFB1) are considered to be major risk factors in the development of hepatocellular carcinoma (HCC) in humans. A high rate of p53 mutations at codon 249 has been reported in these tumors. The tree shrew (Tupaia belangeri chinensis) is a useful animal model for the development of HCC after human hepatitis B virus (HBV) infection or AFB1 treatment. Therefore, it was of particular interest to determine whether the p53 gene in tree shrew HCCs associated with HBV infection and/or with exposure to AFB1 is affected in the same manner as in human HCCs. We determined the tree shrew p53 wild-type nucleotide sequences by RT-PCR and automatic DNA-sequencing. Tree shrew wild-type p53 sequence showed 91.7 and 93.4% homologies with human p53 nucleotide and amino acids sequences, respectively, while it showed 77.2 and 73.7% homologies in mice. One HCC and normal liver tissue from AFB1 treated and one HCC from AFB1- and HBV-treated tree shrew showed no change in p53 sequences, while three HCCs from AFB1- and HBV-treated tree shrews showed point mutations in p53 sequences. One HCC showed point mutations at codon 275, which is on the DNA-binding domain of p53 gene, which might be a cause of gain-of-function during the development of HCC. As a result, our finding indicates that tree shrews exposed to AFB1 and/or HBV had neither codon 249 mutations nor significant levels of other mutations in the p53 gene, as is the case with humans.
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PMID:Mutations in the p53 tumor suppressor gene in tree shrew hepatocellular carcinoma associated with hepatitis B virus infection and intake of aflatoxin B1. 1086 98

Infection by adenovirus 12, transfection with the Ad12 E1B 55 kDa gene, or activation of p53 cause metaphase fragility of four loci (RNU1, PSU1, RNU2, and RN5S) each containing tandemly repeated genes for an abundant small RNA (U1, U2, and 5S RNA). We now show that loss of the Cockayne syndrome group B protein (CSB) or overexpression of the p53 carboxy-terminal domain induces fragility of the same loci; moreover, p53 interacts with CSB in vivo and in vitro. We propose that CSB functions as an elongation factor for transcription of structured RNAs, including some mRNAs. Activation of p53 would inhibit CSB, stalling transcription complexes and locally blocking chromatin condensation. Impaired transcription elongation may also explain the diverse clinical features of Cockayne syndrome.
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PMID:Activation of p53 or loss of the Cockayne syndrome group B repair protein causes metaphase fragility of human U1, U2, and 5S genes. 1088 16


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