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

Mutations of the gene encoding p53, a 53-kilodalton cellular protein, are found frequently in human tumor cells, suggesting a crucial role for this gene in human oncogenesis. To model the stepwise mutation or loss of both p53 alleles during tumorigenesis, a human osteosarcoma cell line, Saos-2, was used that completely lacked endogenous p53. Single copies of exogenous p53 genes were then introduced by infecting cells with recombinant retroviruses containing either point-mutated or wild-type versions of the p53 cDNA sequence. Expression of wild-type p53 suppressed the neoplastic phenotype of Saos-2 cells, whereas expression of mutated p53 conferred a limited growth advantage to cells in the absence of wild-type p53. Wild-type p53 was phenotypically dominant to mutated p53 in a two-allele configuration. These results suggest that, as with the retinoblastoma gene, mutation of both alleles of the p53 gene is essential for its role in oncogenesis.
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PMID:Genetic mechanisms of tumor suppression by the human p53 gene. 227 89

Three lines of evidence suggest that the p53 gene and gene product may act as a negative regulator of growth or a tumor suppressor gene: (1) in several tumors of mice and humans, both of the p53 alleles have suffered mutations and in some cases large or complete deletions demonstrating a loss of function mutation. (2) The murine wild-type p53 gene can suppress transformation of rat embryo fibroblasts in cell culture by other oncogenes such as the adenovirus E1A plus ras genes. In rat embryo fibroblast cells transfected with the wild-type p53 gene, E1A and ras, the wild-type p53 gene either fails to express any RNA or only a mutant form of this p53 gene is selected for in culture. This is analogous (in cell culture) to the observations made in tumors (in vivo) discussed above. (3) Both the tumor suppressor gene, the retinoblastoma sensitivity gene or Rb and p53 are found in oligomeric protein complexes with the oncogene products of the DNA tumor viruses. Both the SV40 large T antigen and the adenovirus E1A plus E1B-55Kd proteins bind to, and presumably inactivate, these tumor suppressor activities which in turn contributes to cellular transformation. A set of point mutations, deletions or insertion mutations in the murine p53 gene localized between amino acid residues 120-270 (out of 390 amino acids) activate the p53 gene and gene product for cooperation with ras in transforming rat embryo fibroblast cells. The mutant p53 proteins produced by these transformed cells all have several properties in common; (1) a prolonged half-life, which is 20 min for the wild-type gene product to greater than 2 hr for the mutant proteins, (2) very high levels of p53 protein in these transformed cells, (3) a conformational change in the mutant p53 proteins, and (4) the binding of mutant p53 protein to the rat cellular heat shock protein, hsc70. These transformation activating mutations apparently act in a trans-dominant manner with the murine mutant p53, forming an oligomeric protein complex with the wild-type rat p53 proteins, resulting in the inactivation of the wild-type p53 function (rat p53).
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PMID:The p53 tumor suppressor gene and gene product. 248 33

Human cytomegalovirus (HCMV) infection stimulates cellular DNA synthesis and causes chromosomal damage. Because such events likely affect cellular proliferation, we investigated the impact of HCMV infection on key components of the cell cycle. Early after infection, HCMV induced elevated levels of cyclin E, cyclin E-associated kinase activity, and two tumor suppressor proteins, p53 and the retinoblastoma gene product (Rb). The steady-state concentration of Rb continued to rise throughout the infection, with most of the protein remaining in the highly phosphorylated form. At early times, HCMV infection also induced cyclin B accumulation, which was associated with a significant increase in mitosis-promoting factor activity as the infection progresses. In contrast, the levels of cyclin A and cyclin A-associated kinase activity increased only at late times in the infection, and the kinetics were delayed relative to those for cyclins E and B. Analysis of the cellular DNA content in the infected cells by flow cytometry showed a progressive shift of the cells from the G1 to the S and G2/M phases of the cell cycle, leading to an accumulation of aneuploid cells at late times. We propose that these HCMV-mediated perturbations result in cell cycle arrest in G2/M.
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PMID:Cytomegalovirus infection induces high levels of cyclins, phosphorylated Rb, and p53, leading to cell cycle arrest. 747 79

Epstein-Barr virus nuclear antigen leader protein (EBNA-LP) is important for primary B-lymphocyte growth transformation. We now demonstrate that the W repeat-encoded domain of EBNA-LP significantly associates with proteins of the heat shock protein 70 family (hsp72/hsc73). hsp72/hsc73 may mediate the previously observed interaction between EBNA-LP and the retinoblastoma protein or p53.
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PMID:The Epstein-Barr virus nuclear antigen leader protein associates with hsp72/hsc73. 749 44

With a brother and sister, osteosarcoma developed at the age of 11 and 14 respectively. With both there was no previous retinoblastoma or other bone disease with a proclivity to develop osteosarcoma. We discuss possible explanations for familial aggregation of osteosarcoma, citing external or genetic factors. We suggest that it is the retinoblastoma gene RB and the tumor suppressor gene p53 which play an important part in the development of osteosarcoma.
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PMID:[Osteosarcoma in 2 siblings. A case report]. 750 Jun 7

Cancers in which mutations have been identified in putative tumor suppressor genes, such as the TP53 gene, the retinoblastoma (RBI) gene, the adenomatous polyposis coli (APC) gene, and the Wilms tumor (WTI) gene, frequently show loss of the corresponding allele on the homologous chromosome. To identify locations of tumor suppressor genes involved in uterine cancer, we examined loss of heterozygosity (LOH) by using genomic probes detecting RFLPs in 35 uterine cancers at 29 loci throughout the genome, and with highly informative microsatellite markers in 21 uterine cancers at nine putative or known tumor suppressor gene loci. High frequencies of allelic loss found at loci on 3p (71%), 9q (38%), 10q (35%), and 17p (35%) suggest that tumor suppressor genes involved in uterine carcinogenesis exist in these regions. There were no significant differences in frequencies of LOH between cancers of the uterine cervix and cancers of the uterine endometrium at any of the loci tested.
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PMID:Allelotype of uterine cancer by analysis of RFLP and microsatellite polymorphisms: frequent loss of heterozygosity on chromosome arms 3p, 9q, 10q, and 17p. 751 41

Although recurrent chromosome abnormalities have been identified in several histologic subtypes of sarcomas, no consistent rearrangement has yet been found in osteosarcomas. Cytogenetic analyses of nine cases of osteosarcoma are reported, including seven newly diagnosed tumors and two recurrent tumors. There were seven high-grade osteosarcomas, one periosteal osteosarcoma, and one well-differentiated sarcoma. All tumors were studied in short-term primary culture. Modal number ranged from near diploid to near triploid. Seven tumors had complex karyotypes with multiple structural abnormalities; two had only normal karyotypes. The retinoblastoma gene on chromosome 13 and the TP53 gene on chromosome 17 have been involved in osteosarcoma. Five tumors had loss of a whole copy of chromosome 13, and three of these also had a loss of a whole copy of chromosome 17. However, these losses were observed in the setting of numerous other chromosome losses. Numerous structural abnormalities were observed, many involving additions of unidentified material, unbalanced translocations, or deletions. Structural abnormalities with similar breakpoints involving 6q, 8q, 9q, and 14p were seen in two or three tumors each. When the tumors in this series were added to the 18 published cases, the pericentromeric regions of chromosomes 1, 3, and 14, and segments 6q15-21, 8q24, 9q34, 12p13, 17p13, and 19q13, were found to be involved in five or more structural rearrangements. Molecular analyses of these chromosome regions may yield genes important in the pathogenesis of osteosarcoma.
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PMID:Chromosome analysis of nine osteosarcomas. 751 49

Immunocytochemical methods are important tools for identifying antigens in tissue sections and cell smears. Some antigens were retrieved in formalin-fixed and paraffin-embedded tissues by means of a microwave technique. This method also increased the sensitivity of the immunohistochemical detection of several other antigens. Altogether, microwave boiling of the tissue sections in citrate buffer clearly improved the immunoreactivity for cytokeratin 18, oestrogen receptor, Ki-67 protein, PCNA, p53 protein, retinoblastoma gene protein and c-erbB-2 protein. This new technique, which can be applied in every pathology laboratory, will facilitate the application of immunohistochemical methods for research and diagnostic work.
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PMID:[Microwave oven in immunohistochemistry. An important tool for determination of antigens in formalin-fixed and paraffin-embedded tissue]. 752 43

We describe the properties of a physiological cell death (PCD)-resistant subline of WEHI-231 generated from the PCD-susceptible WEHI-231.7 JM cell line maintained in our laboratory. The PCD-resistant WEHI-231.7 JMRE subline was uniquely resistant to anti-immunoglobulin (Ig)M-induced PCD but not to irradiation and etoposide. In these sublines, we compared the expression of genes implicated in regulating PCD. Northern analysis of c-myc, c-fos, egr-1, Fas, p53 and retinoblastoma revealed similar basal levels of expression in all sublines tested and comparable responses to anti-IgM treatment. Similarly, the expression of bcl-2, bcl-x, bax and IL-1 beta converting enzyme did not correlate with susceptibility to anti-IgM-induced PCD. Next, we systematically studied signal transduction events including: tyrosine phosphorylation, Ca++ flux, and ceramide production in the Jm and JMRE sublines. The tyrosine phosphorylation patterns and the Ca++ influx generated following sIgM engagement were very similar in the JM and JMRE sublines. In contrast, the generation of ceramide differed in the PCD-resistant and PCD-susceptible sublines. Ceramide is produced following cross-linking sIgM on WEHI-231.7 JM cells and causes PCD. Ceramide levels in anti-IgM-treated WEHI-231.7 JMRE cells are low and appear to be insufficient to induce PCD.
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PMID:Resistance to anti-IgM-induced apoptosis in a WEHI-231 subline is due to insufficient production of ceramide. 753 68

Differentiation and luteinization of granulosa cells are induced by gonadotrophic hormones and other substances elevating intracellular levels of cyclic AMP (cAMP). We have investigated the correlation between the potency of these substances to enhance steroidogenesis and to induce apoptosis in primary granulosa cell cultures obtained from rat preovulatory follicles. The cAMP analog, 8-Br cAMP, induced apoptosis in more than 90% of the cell population within 15 h of incubation at 37 degrees C in serum-free medium. The physiological stimulants of these cells, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which caused a moderate cAMP response in these cells, followed by a desensitization period, increased progesterone production by fourfold with no apparent effect on cell death. In contrast, forskolin, a potent activator of adenylate cyclase, stimulated both the cAMP and steroidogenic response by an order of magnitude greater than the gonadotropin stimulation, concomitantly with a pronounced increase in cell death (25%). Moreover, blocking of the cellular phosphodiesterase activity in forskolin-stimulated cells by isobutylmethylxanthine (IBMX), which maintains high levels of intracellular cAMP, led to further enhancement of cell death following 40 h of incubation (50%). Basic fibroblast growth factor (bFGF) and gonadotropin-releasing hormone (GnRH), which stimulated steroidogenesis in these cells in a cAMP-independent manner, did not promote cell death. Moreover, costimulation of the cells with forskolin and bFGF led to a substantial decrease in the incidence of apoptosis relative to forskolin alone. In order to examine whether the expression of tumor suppressor genes is involved in granulosa cell differentiation and apoptosis induced by cAMP, we examined the effect of cAMP in SV40 transformed granulosa cells, in which T-antigen expression is expected to block the activity of p53 as well as of the retinoblastoma gene product (pRB) and its related proteins. Cultures of three different cell lines established by SV40 transformation demonstrated resistance to 8-Br-cAMP- or forskolin plus IBMX-induced apoptosis, in contrast to the severe apoptotic response in primary cells. We suggest that stimulation of primary granulosa cells by high levels of cAMP catalyzes programmed cell death, while stimulation of the cells by gonadotropic hormones, which result in a moderate cAMP response, followed by desensitization to further stimulation, can prolong the lifespan of the luteinized granulosa cells. Moreover, one or more tumor suppressor proteins may mediate the cAMP generated signal leading to cell death.
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PMID:cAMP-mediated signals as determinants for apoptosis in primary granulosa cells. 753 93


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