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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To establish a new predictor of human cervical cancer radioresponse, we investigated the transactivational ability of p53 gene in tumor tissue for use as a marker of both pretreatment and postirradiation levels of mRNA of its downstream gene, WAF1. A total of 38 wild-type p53-bearing patients with histologically proved uterine cervical cancer were treated with definitive radiotherapy. Their p53 status was investigated using a single-strand conformation polymorphism analysis, and human papilloma virus 16, 18, 33, and 58 E6 was determined by polymerase chain reaction in pretreatment biopsy specimens. WAF1 mRNA was estimated by reverse transcriptase-polymerase chain reaction in both pretreatment specimens and those obtained after the administration of 10.8 Gy. Undetectable or low pretreatment levels of WAF1 mRNA were associated with complete response in the majority of cases, whereas only a few patients with a high pretreatment WAF1 level responded to treatment (P = .03). The increase in the postirradiation level of WAF1 mRNA positively correlated with better treatment response and long survival (P = .02). Although the human papilloma virus infection did not change the radiation response directly, it decreased the inducibility of WAF1. Consequently, the lower inducibility of WAF1 resulted in a poor treatment response. This is the first clinical report showing that the transactivational ability of p53 may be a determinant of the efficacy of cervical cancer radiotherapy.
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PMID:Determination of p53-mediated transactivational ability in radiation-treated cervical cancer. 1097 90

p53 tumour-suppressor gene is involved in cell growth control, arrest and apoptosis. Nevertheless cell cycle arrest and apoptosis induction can be observed in p53-defective cells after exposure to DNA-damaging agents such as 5-fluorouracil (5-FU) suggesting the importance of alternative pathways via p53-independent mechanisms. In order to establish relationship between p53 status, cell cycle arrest, Bcl-2/Bax regulation and 5-FU sensitivity, we examined p53 mRNA and protein expression and p53 protein functionality in wild-type (wt) and mutant (mt) p53 cell lines. p53 mRNA and p53 protein expression were determined before and after exposure to equitoxic 5-FU concentration in six human carcinoma cell lines differing in p53 status and displaying marked differences in 5-FU sensitivity, with IC(50)values ranging from 0.2-22.6 mM. 5-FU induced a rise in p53 mRNA expression in mt p53 cell lines and in human papilloma virus positive wt p53 cell line, whereas significant decrease in p53 mRNA expression was found in wt p53 cell line. Whatever p53 status, 5-FU altered p53 transcriptional and translational regulation leading to up-regulation of p53 protein. In relation with p53 functionality, but independently of p53 mutational status, after exposure to 5-FU equitoxic concentration, all cell lines were able to arrest in G1. No relationship was evidenced between G1 accumulation ability and 5-FU sensitivity. Moreover, after 5-FU exposure, Bax and Bcl-2 proteins regulation was under p53 protein control and a statistically significant relationship (r = 0.880, P = 0.0097) was observed between Bcl-2/Bax ratio and 5-FU sensitivity. In conclusion, whatever p53 status, Bcl-2 or Bax induction and Bcl-2/Bax protein ratio were correlated to 5-FU sensitivity.
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PMID:Bcl-2/Bax protein ratio predicts 5-fluorouracil sensitivity independently of p53 status. 1104 65

Treatment of haematopoietic BA/F3 cells with the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine (FUdR) activated apoptosis through a mechanism that required continuous protein synthesis and was inhibited by Bcl-2 over-expression. Analysis of p53 levels in cells treated with FUdR indicated a marked accumulation of this protein. Accumulation of p53 was also observed in cells over-expressing Bcl-2. In BA/F3 cells transfected with a cDNA coding for the human papilloma virus protein E6, p53 accumulation after FUdR treatment was inhibited markedly. However, apoptosis was induced in both control and E6 cells to a similar extent. The role of the CD95/CD95 ligand (CD95L) system in FUdR-induced apoptosis was also assessed. As determined by reverse transcriptase PCR, BA/F3 expressed a low constitutive level of CD95L mRNA, which decreased following FUdR treatment. Moreover, blocking CD95-CD95L interactions with antagonistic CD95 monoclonal antibody did not prevent drug-induced apoptosis. Furthermore, analysis of caspase involvement showed important differences in apoptosis induced by CD95-triggering or FUdR treatment. In summary, these results suggest that apoptosis induced by thymineless stress in haematopoietic BA/F3 cells occurs by a mechanism that does not require accumulation of p53 and which is independent of CD95-CD95L interactions.
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PMID:Apoptosis of haematopoietic cells upon thymidylate synthase inhibition is independent of p53 accumulation and CD95-CD95 ligand interaction. 1111 3

We analyzed TP53 codon 72 polymorphism, HPV DNA in 32 subjects with oesophageal cancer and 57 healthy subjects with normal oesophageal cytology from an area of China with a high prevalence for this cancer (Linxian County, Henan Province). The frequency of the proline allele (0.63) was significantly higher in the Chinese population than in most European or American populations. No significant association was found between TP53 codon 72 genotype and cancer. We also found a low prevalence of HPV DNA (6.7%) in both cancer cases and healthy subjects. Our findings do not support the association between risk of oesophageal cancer, human papilloma virus infection, and TP53 codon 72 polymorphism in a Chinese population at high risk of oesophageal cancer.
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PMID:Absence of association between HPV DNA, TP53 codon 72 polymorphism, and risk of oesophageal cancer in a high-risk area of China. 1114 30

Neuroblastoma-derived tumor cells, unlike cells from other tumor types, characteristically express a wildtype but cytoplasmically sequestered p53 protein. To ascertain whether the p53 in these cells retained any physiological activity, we inactivated it in SK-N-SH cells, a neuroblastoma-derived cell line, by introducing the human papilloma virus type 16 E6 expression plasmid. Parent SK-N-SH cell cultures are composed of two cell types exhibiting characteristic morphologies designated neuroblastic (N-type) or substrate-adherent fibroblastic (S-type) cells, both of which have been shown to spontaneously transdifferentiate or interconvert. We report here that down-regulation of p53 resulted in conversion of SK-N-SH cells to the substrate-adherent fibroblast-like S-type cells. The morphologic conversion was accompanied by a loss of neurofilament expression, a marker for the neuronal N-type cells, an increase in the expression of vimentin, and a lack of responsiveness to retinoic acid-induced neuronal differentiation. Importantly, we did not observe N-type cells in the E6-transfected cell population, suggesting that they were incapable of transdifferentiating to the N-type morphology. We also tested the ability of these E6-transfected S-type cells to form colonies in soft agar and observed a markedly reduced capacity of these cells to do so when compared with the parent and mutant E6-transfected cells. These results suggest that p53 is required for the maintenance of the neuroblastic tumorigenic phenotype.
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PMID:Morphologic conversion of a neuroblastoma-derived cell line by E6-mediated p53 degradation. 1120 42

Although the mortality and incidence of cervical cancer have been decreasing, those of uterine-body, or endometrial, cancer have been increasing. The proportion of endometrial cancer was reported to have become 33.6% of primary uterine cancers in 1995. Infection with certain types of human papilloma virus (HPV) is considered to be etiologically important for the occurrence of cervical cancer. Because HPV is sexually transmitted, some risk factors for cervical cancer are associated with certain kinds of sexual behavior such as a young age at first intercourse, multiple partners, and infrequent use of barrier-type contraceptives such as condoms. Frequent conceptions and deliveries and histories of sexually transmitted diseases like infection with herpes simplex virus type 2 or chlamydia also have been suggested to be associated with the risk of cervical cancer. Smoking habits and infrequent intake of vegetables and fruits may be related to the increased risk of cervical cancer by supporting persistent infection of HPV through impaired immunological function. Although host factors such as a variant of a tumor suppressor gene like p53 have been assessed in terms of the risk of cervical cancer, these are not yet clearly elucidated. Estrogen stimulation of the endometrium unopposed by progesterone stimulation, namely, unopposed estrogen stimulation, is thought to be involved in the etiology of endometrial cancer. Frequent intake of animal fat, obesity or being overweight, infertility, and histories of diabetes mellitus, hypertension, and polycystic ovary syndrome have been reported to be risk factors for endometrial cancer, and they are thought to increase unopposed estrogen stimulation. Estrogen replacement therapy for postmenopausal symptoms, tamoxifen therapy for breast cancer, and taking sequential-type oral contraceptives have been shown to be exogenous risk factors for endometrial cancer in that they increase unopposed estrogen stimulation to endometrium.
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PMID:[Recent progress in epidemiologic research of uterine cancer]. 1124 42

A cellular isogenic system, in which wt-p53 expression level is challenged through human papilloma virus 16-E6 gene transfection, was previously developed in our laboratory. As an average trend, cancer lines bearing an inactivated p53 have a general tendency toward an increased resistance to chemotherapeutic agents. However, using the above isogenic system, the transfected line (A2780-N9) was found to be more sensitive to taxol than the parental one (A2780-WT). In a NCI meta-analysis study the average trend is that altered p53 status is related to cellular resistance to topoisomerase II inhibitors, while it is irrelevant in determining sensitivity/resistance to mitotic spindle poisons. We report that our E6 transfected line, previously shown to be hypersensitive to taxol, is also clearly hypersensitive to a topoisomerase II inhibitor (mitoxantrone). Differences in cytotoxicity are more evident after a shorter/more intense exposure, than after a milder/longer exposure, being A2780-WT 27-fold more resistant than the transfected clone in the former case. These differences seem to be related to the different activities ("cross-talks") of E6 protein, among which shortening of p53 half-life is only one aspect. After mitoxantrone treatment A2780-N9 cells display also an increased propensity to apoptosis. In addition, a literature survey of E6 effects in transfected cancer cell lines, seems to suggest that chemosensitization to different classes of antineoplastic agents is the rule rather than the exception in these E6-based isogenic systems.
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PMID:HPV16-E6 enhances mitoxantrone sensitivity in a human ovarian cancer line: an isolated instance or a trend? 1125 Nov 71

The tumor suppressor PTEN is one of the most commonly inactivated genes in human cancer. Glioblastoma multiforme cells harboring mutant PTEN have abnormally high levels of 3' phosphoinositides and elevated protein kinase B activity. Expression of wild-type PTEN in glioma cells, containing endogenous mutant PTEN, reduces 3' phosphoinositides levels, inhibits PKB activity, and induces G1 cell cycle arrest. We investigated the mechanism of the PTEN-induced growth arrest in glioma cell lines. Expression of PTEN is associated with increased expression of p27Kip1, decreased expression of cyclins A and D3, inhibition of cdk2 activity, and dephosphorylation of pRb. Inactivation of p53, by the human papilloma virus E6 oncoprotein, does not prevent PTEN-induced G1 arrest, implying that p53 is not required for G1 arrest. In contrast, p27Kip1 antisense oligonucleotides abrogated the growth arrest induced by PTEN. Furthermore, blocking p27Kip1 expression prevented the PTEN-induced reduction of cyclin-dependent kinase 2 activity, indicating that p27Kip1 functions upstream of cyclin-dependent kinase 2 in the PTEN regulatory cascade. These results implicate p27Kip1 as a critical mediator of PTEN-induced G1 arrest.
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PMID:p27Kip1 is required for PTEN-induced G1 growth arrest. 1128 Jul 73

In higher eukaryotic cells, the p53 protein is degraded by the ubiquitin-26S proteasome system mediated by Mdm2 or the human papilloma virus E6 protein. Here we show that COP9 signalosome (CSN)-specific phosphorylation targets human p53 to ubiquitin-26S proteasome-dependent degradation. As visualized by electron microscopy, p53 binds with high affinity to the native CSN complex. p53 interacts via its N-terminus with CSN subunit 5/Jab1 as shown by far-western and pull-down assays. The CSN-specific phosphorylation sites were mapped to the core domain of p53 including Thr155. A phosphorylated peptide, Deltap53(145-164), specifically inhibits CSN-mediated phosphorylation and p53 degradation. Curcumin, a CSN kinase inhibitor, blocks E6-dependent p53 degradation in reticulocyte lysates. Mutation of Thr155 to valine is sufficient to stabilize p53 against E6-dependent degradation in reticulocyte lysates and to reduce binding to Mdm2. The p53T155V mutant accumulates in both HeLa and HL 60 cells and exhibits a mutant (PAb 240+) conformation. It induces the cyclin-dependent inhibitor p21. In HeLa and MCF-7 cells, inhibition of CSN kinase by curcumin or Deltap53(145-164) results in accumulation of endogenous p53.
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PMID:COP9 signalosome-specific phosphorylation targets p53 to degradation by the ubiquitin system. 1128 27

The human TR2 orphan receptor (TR2), initially isolated from testis and prostate cDNA libraries, is a member of the steroid receptor superfamily. TR2 can regulate several target genes via binding to a consensus response element (AGGTCA) in direct repeat orientation (AGGTCAX((n))AGGTCA, n = 0-6). Here we show that TR2 is able to induce the expression of human papilloma virus type 16 (HPV-16) genes via binding to a DR4 response element in the long control region of HPV-16. Additionally, one of the HPV-16 gene products, the E6 oncogene, regulates TR2 gene expression. A likely mechanism for this regulation involves E6-mediated degradation of the tumor suppressor p53, a protein known to suppress TR2 expression. Together our data provide evidence for feedback regulation between TR2 and HPV-16, which represents a novel regulatory pathway involving a member of the steroid receptor superfamily and the HPV-16 DNA tumor virus.
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PMID:Feedback regulation between orphan nuclear receptor TR2 and human papilloma virus type 16. 1135 73


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