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

Previous emphasis in cancer research has been placed on genes in which activating mutations are found in experimental systems and sometimes in human tumors, and many of these genes are the cellular homologs of retroviral oncogenes. Studies of genes whose functions are necessary for maintenance of the normal cellular state, but for which loss-of-function mutations lead to tumor development, are limited. The latter genes have been variously termed 'tumor suppressor genes', 'recessive oncogenes', and 'anti-oncogenes', and each term defines a specific aspect of their properties and may not always be applicable. The retinoblastoma (RB) gene is the first such gene to be identified, and was isolated based on its chromosome localization and on the recessive nature of the tumor phenotype. That is, both wild type RB alleles must be inactivated in a single cell for neoplastic transformation to occur, and deletions at the chromosomal locus now known to contain RB are often found in retinoblastoma cells. Candidate genes for Wilms' tumor and neurofibromatosis type I have also been identified recently, and loss of function of these genes seems to be indicated for these diseases. Allelic loss of chromosome 17p13 is frequently observed in many tumor types. The p53 gene was mapped to this chromosomal region and has been shown to be a tumor suppressor gene, and germ-line mutations of p53 recently were found to be correlated with Li-Fraumeni syndrome, a syndrome characterized by multiple neoplasms. Rapid progress in studies of tumor suppressor genes points to diverse mechanisms for their functioning in the negative regulation of cell growth. A scenario depicting cell growth control by positive and negative regulators, based on new and emerging findings, is the main focus of this review.
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PMID:Tumor suppressor genes: a new era for molecular genetic studies of cancer. 175 64

The TP53 gene is considered to be a negative regulator of cell growth whose inactivation is an important step in the development or progression of malignancies. Recently, germ line TP53 mutations have been detected in a familial cancer syndrome, the dominantly inherited Li-Fraumeni syndrome. Using single strand conformation polymorphism analysis of PCR products, we looked for TP53 mutations in DNA of patients with Fanconi anemia, an autosomal recessive disease characterized by increased predisposition to neoplasia. We did not find any TP53 mutation in 13 patients, suggesting that this tumor suppressor gene is not directly involved in the cancer susceptibility observed in Fanconi's anemia.
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PMID:Lack of mutations in the TP53 tumor suppressor gene exons 5 to 8 in Fanconi's anemia. 180 24

It has been well established that sometimes cancer clusters within specific families. This has suggested the possibility that some of those families might carry genetic defects which provide susceptibility to specific cancers. Retinoblastoma, an embryonal tumor of the eye represents an extreme example of a tumor which has a dramatic genetic component. Several studies have shown that inactivation at the retinoblastoma gene is probably both necessary and sufficient to initiate retinoblastoma formation. Patients who survive the inherited form of the disease are at risk of developing mesenchymal tumors, melanoma and brain tumors in as high as 10% of the patients before they are 40 years old. Because the product of the retinoblastoma gene, p105Rb, is expressed in all cell types, the obvious question is what accounts for these tissue specific differences in the role of p105Rb. Small cell lung carcinomas virtually all have associated mutations in the Rb gene and yet those tumors do not occur at a significantly increased frequency in patients with the hereditary form of retinoblastoma. In order to identify genes which might predispose to some of the more common adult malignancies, we have focused on one form of hereditary breast cancer. We chose a rare form of hereditary breast cancer which occurs in families with sarcomas (Li-Fraumeni Syndrome). By use of the candidate gene approach we tested which germ line p53 mutations were found in affected family members with Li-Fraumeni Syndrome (LFS). We have found that virtually all of the families with LFS have germ line p53 mutations, and that these tumors have undergone inactivation of the remaining wild-type p53 allele. In order to investigate the role of germ line p53 mutations outside of these rare families, we have begun to investigate other high risk groups. These results indicate that de novo germ line p53 mutations certainly occur in these high risk groups. These findings along with the recognition of the germ line p53 mutations in families with LFS provide clues about the importance of uncovering hidden susceptibilities from germ line tumor suppressor genes not only for the care of patients, but also for understanding the primary events that normally regulate the growth of cells in various tissue.
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PMID:Cancer risks from germ line tumor suppressor gene mutations. 184 52

Germ line p53 point mutations have been reported for some families with Li-Fraumeni syndrome, a syndrome characterized by a dominantly inherited increased susceptibility for the development of early age of onset neoplasms of diverse origin in multiple family members. All of the initially reported p53 germ line mutations have been found exclusively within a single conserved, nonpolymorphic region of the gene between condons 245 and 258. The restricted distribution of these inherited mutations has led to speculation that germ line p53 mutations have unique properties [B. Vogelstein, Nature (Lond.), 348: 681-682, 1990]. We report here on the identification of a p53 germ line mutation at codon 133 (ATG----ACG) in nine members of an extended Li-Fraumeni syndrome family. This mutation leads to an amino acid substitution in the protein and is shown to completely cosegregate with Li-Fraumeni syndrome associated cancer in this family. Its location extends the region of the p53 gene where inherited mutations predisposing to cancer are observed and suggests that their distribution may be diverse.
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PMID:A germ line mutation in exon 5 of the p53 gene in an extended cancer family. 193 2

Familial cancer syndromes have helped to define the role of tumor suppressor genes in the development of cancer. The dominantly inherited Li-Fraumeni syndrome (LFS) is of particular interest because of the diversity of childhood and adult tumors that occur in affected individuals. The rarity and high mortality of LFS precluded formal linkage analysis. The alternative approach was to select the most plausible candidate gene. The tumor suppressor gene, p53, was studied because of previous indications that this gene is inactivated in the sporadic (nonfamilial) forms of most cancers that are associated with LFS. Germ line p53 mutations have been detected in all five LFS families analyzed. These mutations do not produce amounts of mutant p53 protein expected to exert a trans-dominant loss of function effect on wild-type p53 protein. The frequency of germ line p53 mutations can now be examined in additional families with LFS, and in other cancer patients and families with clinical features that might be attributed to the mutation.
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PMID:Germ line p53 mutations in a familial syndrome of breast cancer, sarcomas, and other neoplasms. 843 45

Tumour suppressor genes, whose usual function seems to be controlling normal cell proliferation, have been implicated in many inherited and sporadic forms of malignancies Much evidence supports the concept of tumour formation by loss-of-function mutations in suppressor genes, as predicted by the two-hit model of Knudson and DeMars. The suppressor gene, p53, is affected in such a manner by numerous mutations, which occur in a variety of human tumours. These mutations usually represent the loss of one allele and the substitution of a single base in the other. We have now analysed the p53 gene in a family affected by Li-Fraumeni syndrome, a rare autosomal dominant syndrome characterized by the occurrence of diverse mesenchymal and epithelial neoplasms at multiple sites. In some instances the neoplasms seem to be related to exposure to carcinogens, including ionizing radiation. The Li-Fraumeni family that we studied had noncancerous skin fibroblasts (NSF) with an unusual radiation-resistant phenotype. DNA derived from the NSF cells of four family members, spanning two generations, had the same point mutation in codon 245 (GGC----GAC) of the p53 gene. This mutation leads to substitution of aspartic acid for glycine in one of the regions identified as a frequent target of point mutations in p53. The NSF cell lines with the mutation also retained the normal p53 allele. This inherited p53 mutation may predispose the members of this family to increased susceptibility to cancer.
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PMID:Germ-line transmission of a mutated p53 gene in a cancer-prone family with Li-Fraumeni syndrome. 225 80

Cultured cells from patients inheriting the rare cancer-prone and radiotherapy-sensitive disorder ataxia-telangiectasia (A-T) exhibit anomalies in cell cycle control and protein kinase C (PKC)-mediated upregulation of p53 protein following exposure to ionizing radiation. It remains unclear, however, as to whether this irregularity in a p53-dependent signal transduction pathway controlling the G1/S checkpoint is causally linked to the most consistent molecular hallmark of A-T-namely, marked attenuation in the inhibition of replicative DNA synthesis at early times (< or = 2 h) after irradiation [radioresistant DNA synthesis (RDS)]. We report here that treatment of normal human fibroblast strains with inhibitors of calmodulin (CaM) (i.e. W7 and W13) and CaM-dependent protein kinases II and IV (i.e. KN62) prior to radiation exposure elicits an 'A-T-like' RDS phenotype, whereas treatment with PKC inhibitors (e.g. staurosporine) does not produce this response. Moreover, at 1 h post-gamma irradiation A-T fibroblasts undergo normal induction of p53 protein while exhibiting the RDS trait. At later times (e.g. 4 h) following irradiation, however, these A-T cells contain abnormally low levels of p53 protein, as do their lymphoblastoid cell line counterparts during the entire post-gamma ray incubation period. On the other hand, human cells which either lack the p53 gene completely (i.e. HL60 leukemia cells) or harbor a germline mutation in the gene (i.e. Li-Fraumeni syndrome cells) shut down their DNA replication machinery normally upon sustaining radiation damage. We thus conclude that the transitory delay in DNA synthesis routinely experienced by human cells in the face of radiation injury is mediated through a CaM-dependent regulatory cascade which involves neither PKC nor p53 protein. Accordingly, A-T cells appear to be malfunctional in at least two distinct radiation-responsive signalling pathways, one regulating the G1/S checkpoint and governed by p53 and PKC and another controlling passage through S phase and requiring CaM.
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PMID:Characterization of the signal transduction pathway mediating gamma ray-induced inhibition of DNA synthesis in human cells: indirect evidence for involvement of calmodulin but not protein kinase C nor p53. 747 84

Mice with disrupted germline p53 alleles have been engineered by us and others and have been shown to have enhanced susceptibility to spontaneous tumors of various types. We monitored a large number of p53-deficient mice (p53+/- and p53-/-) and their wild-type littermates (p53+/+) of two different genetic backgrounds (129/Sv and mixed C57BL/6 x 129/Sv) up to 2 yr of age. p53+/- and p53-/- 129/Sv mice show accelerated tumorigenesis rates compared with their p53-deficient counterparts of mixed C57BL/6 x 129/Sv genetic background. The tumor spectra of the two strains of mice are similar except that almost half of 129/Sv p53-/- males develop malignant teratomas, whereas these tumors are rarely observed in C57BL/6 x 129/Sv mice and never in 129/Sv p53+/- males. In the study reported here, we further characterized the lymphomas that arose in the p53-nullizygous mice and found that over three-quarters of the lymphomas were of thymic origin and contained primarily immature (CD4+/CD8+) T-cells, whereas the remainder originated in the spleen and peripheral lymph nodes and were of B-cell type. The high incidence of early-onset lymphomas in the nullizygous mice makes these animals a good lymphoma model, whereas the heterozygous mice may be a useful model for Li-Fraumeni syndrome, a human inherited cancer predisposition.
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PMID:Effects of genetic background on tumorigenesis in p53-deficient mice. 754 19

A number of genes are known to be involved in inherited susceptibility to breast and/or ovarian cancer. In the context of high-risk families the most important genes are BRCA1 on chromosome 17q, which is associated with a high penetrance of both breast and ovarian cancer, and BRCA2 on chromosome 13q, which causes a high risk of breast cancer but a lower risk of ovarian cancer. Other high-risk cancer genes that confer increased risks of breast or ovarian cancer in addition to other cancers include the hereditary non-polyposis colorectal cancer genes and the TP53 gene, which causes breast cancer as part of the Li-Fraumeni syndrome. The predisposing mutations in these genes are relatively rare in the population. More common genes which are associated with an increased, but lower, risk of breast cancer are the ataxiatelangiectasia gene and the HRAS1 gene. This paper reviews recent progress in mapping and cloning of these susceptibility genes, and provides estimates of the cancer risks associated with each gene and the frequency of predisposing mutations.
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PMID:The genetics of breast and ovarian cancer. 754 24

We investigated whether mutations in the p53 tumor suppressor gene alter UV sensitivity and/or repair of UV-induced DNA damage in primary human skin fibroblasts from patients with Li-Fraumeni syndrome, heterozygous for mutations in one allele of the p53 gene (p53 wt/mut) and sublines expressing only mutant p53 (p53 mut). The p53 mut cells were more resistant than the p53 wt/mut cells to UV cytotoxicity and exhibited less UV-induced apoptosis. DNA repair analysis revealed reduced removal of cyclobutane pyrimidine dimers from overall genomic DNA in vivo in p53 mut cells compared with p53 wt/mut or normal cells. However, p53 mut cells retained the ability to preferentially repair damage in the transcribed strands of expressed genes (transcription-coupled repair). These results suggest that loss of p53 function may lead to greater genomic instability by reducing the efficiency of DNA repair but that cellular resistance to DNA-damaging agents may be enhanced through elimination of apoptosis.
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PMID:Li-Fraumeni syndrome fibroblasts homozygous for p53 mutations are deficient in global DNA repair but exhibit normal transcription-coupled repair and enhanced UV resistance. 756 35


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