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

Effects of environmental carcinogens on DNA can be detected, because, while each carcinogenic agent is inherently different, its corresponding "fingerprint" is unique to a specific mutation pattern. The p53 tumor suppressor gene is of particular interest because the relationship between environmental factors and genetic alterations of carcinogenesis can be investigated. In this report, we compared the mutation patterns of the p53 gene in human colorectal tumors from Japanese patients with those from US patients. The results show different rates of transversion and transition among these two populations, which suggests a difference between Japan and the US in the etiological factors underlying colorectal tumorigenesis.
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PMID:Mutations of p53 gene in human colorectal tumor in Japan: molecular epidemiological aspects. 148 46

The cellular p53 protein is so called because of its molecular weight as determined by SDS-polyacrylamide gel electrophoresis. It was originally classified as a nuclear oncogene product when it was shown by DNA transfection experiments that p53 is able to extend the lifespan of primary rodent cell cultures and to cooperate with an activated ras oncogene to achieve complete transformation of primary cells. However, there is now conclusive evidence that loss of normal p53 expression may be an important step in cell transformation and tumorigenesis. Furthermore, it has been shown that mutant p53 was used for the experiments demonstrating the immortalizing and transforming capacity of p53. Wild-type p53 seems to negatively regulate cell growth and division. So far, the basic function of p53 is not known. Biochemical variability seems to be a key feature of p53 and an understanding of biochemical variations in the p53 protein may contribute to an understanding of how p53 is regulated or how p53 may regulate cell proliferation. Thus, the present review will focus on the biochemical properties of p53.
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PMID:Biochemical properties of the growth suppressor/oncoprotein p53. 150 81

Tumorigenesis is a multistep process involving mutations of dominantly acting proto-oncogenes and mutations and loss-of-function mutations of tumor suppressor genes. Some of these mutations may be inherited, but most of them are acquired. Models for the sequential steps of the genetic changes involved in tumor development have been proposed for certain cancers, such as colon cancer. In the case of ovarian cancer, relatively little is known about the genetic events associated with the initiation or subsequent progression and metastases of the tumor. Cytogenetic analysis has revealed a high incidence of both structural and numerical chromosome changes, and the extent of these changes seems to increase with tumor progression. Oncogene activations of the proto-oncogenes K-ras, c-myc and c-erbB-2 have been found more frequently in aggressive ovarian tumors and may be associated with poor survival. Tumor-specific allele loss involving putative tumor suppressor genes has been observed for loci at chromosomes 11p, 17p, and 17q,--loci commonly deleted in other cancers too. A relatively high incidence of allelic loss on chromosome 6q appears to be specific to ovarian carcinoma. Familial breast/ovarian cancer has been suggested to map to chromosome 8q. Recently we have found a germ-line mutation in the tumor suppressor gene p53 in a family with breast- and ovarian cancers, indicating that this is the predisposing gene in this family. Genetic changes important for the etiology of ovarian cancers seem to involve both somatic mutations of oncogenes and somatic or germ-line inactivation of tumor suppressor genes.
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PMID:Oncogenesis in ovarian cancer. 150 89

Increasing numbers of alterations have been found in protooncogenes (e.g., ras, myc), as well as tumor suppressor genes (e.g., p53, Rb) in various types of tumors. The multiple mutations cannot be explained by the spontaneous mutation rate. It has been suggested that mutator phenotypes leading to the accumulation of these mutations may be required in the early stages of tumorigenesis. To test this hypothesis, the entire coding region of DNA polymerase beta, a repair enzyme, mRNA from colorectal tumors, and corresponding normal mucosa were amplified by polymerase chain reaction, cloned, and sequenced. Mutations in the catalytic domain of DNA polymerase beta were detected in colorectal tumor specimens compared to the normal colorectal mucosa, placenta, and blood samples. Since these mutations changed the structure of polymerase beta, it is expected that the efficiency of the DNA repair system would be impaired and thus may account for the high mutation rate observed in colorectal carcinomas.
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PMID:DNA polymerase beta mutations in human colorectal cancer. 151 47

Tumorigenesis is thought to be a multistep process in which genetic alterations accumulate, ultimately producing the neoplastic phenotype. A model was proposed to explain the genetic basis of colorectal neoplasia that included several salient features. First, colorectal tumors appear to occur as a result of the mutational activation of oncogenes coupled with the inactivation of tumor-suppressor genes. Second, mutations in at least four or five genes are required to produce a malignant tumor. Third, although the genetic alterations often occur in a preferred sequence, the total accumulation of changes, rather than their chronologic order of appearance, is responsible for determining the tumor's biologic properties. Several different genetic alterations were identified that occur during colorectal tumorigenesis. Activational mutation of the ras oncogene was found in approximately 50% of colonic carcinomas and in a similar percentage of intermediate-stage and late-stage adenomas. Allelic deletions were discovered of specific portions of chromosomes 5, 17, and 18, which presumably harbor tumor-suppressor genes. The target of allelic loss events on chromosome 17 has been shown to be the p53 gene, which is mutated, not only in colonic cancer, but also in a large percentage of other human solid tumors. The gene dcc recently was identified; this candidate tumor-suppressor gene on chromosome 18 appears to be altered in colorectal carcinomas. The protein encoded by the dcc gene has significant sequence similarity to neural cell adhesion molecules and other related cell-surface glycoproteins. By mediating cell-cell and cell-substrate interactions, this class of molecules may have important functions in mediating cell growth and differentiation. Alterations of the dcc gene may interfere with maintenance of these controls and thus may play a role in the pathogenesis of colorectal neoplasia. Another candidate tumor-suppressor gene also was identified on chromosome 5, mcc (for mutated in colorectal cancers). The mcc genetic alterations include one tumor with somatic rearrangement of one mcc allele and several tumors with somatically acquired point mutations in the coding region. Studies currently are ongoing to (1) identify additional tumor-suppressor gene candidates, (2) increase our understanding of normal tumor-suppressor gene function, and (3) demonstrate the functional tumor-suppressor ability of these genes both in vivo and in vitro.
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PMID:Genetic alterations in the adenoma--carcinoma sequence. 151 27

To elucidate the molecular basis for endocrine tumorigenesis, p53 mutations in human endocrine tumors were analyzed by using polymerase chain reaction-single strand conformation polymorphism. Exons 5 through 10 of the p53 gene were studied in genomic DNAs from 134 primary endocrine tumors and 6 human endocrine cancer-derived cell lines. Mutations were detected and identified in 4 endocrine tumors, including one parathyroid adenoma and three thyroid carcinoma cell lines. The sites of these mutations were in exons 5 (codon 151 and 152) and 7 (codon 248 and 255). In all of three tumor cell lines, but not in a parathyroid adenoma, the normal allele encoding the p53 gene was lost. However, p53 mutations were not found in any other endocrine tumors or cell lines. Based upon these results, we concluded that the p53 gene may play a role in the tumorigenesis of a limited number of parathyroid adenoma and thyroid cancers, and that the p53 mutation with an allelic loss of the p53 gene is an important factor in malignant tumorigenesis of the thyroid gland.
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PMID:Role of p53 mutations in endocrine tumorigenesis: mutation detection by polymerase chain reaction-single strand conformation polymorphism. 151 62

The p53 gene encodes a nuclear phosphoprotein and is now considered as a tumor suppressor gene. Mutations of the p53 gene have frequently been observed in several types of solid tumors and are believed to be implicated in the development of these tumors. Recent studies have shown that the p53 gene is altered in chronic myelogenous leukemia (CML) in blast crisis. In CML, alterations of the p53 gene may play an important role in the development of blast crisis. More recently, p53 mutations have been reported in other types of hematologic neoplasms, such as acute leukemia, adult T-cell leukemia, and malignant lymphoma. These observations suggest that inactivation of the p53 gene is involved in the tumorigenesis of various types of hematologic neoplasms.
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PMID:[Mutations of the p53 gene in hematologic neoplasms]. 151 57

The fifth base in human DNA, 5-methylcytosine, is inherently mutagenic. This has led to marked changes in the distribution of the CpG methyl acceptor site and an 80% depletion in its frequency of occurrence in vertebrate DNA. The coding regions of many genes contain CpGs which are methylated in sperm and serve as hot spots for mutation in human genetic diseases. Fully 30-40% of all human germline point mutations are thought to be methylation induced even though the CpG dinucleotide is under-represented and efficient cellular repair systems exist. Importantly, tumor suppressor genes such as p53 also contain methylated CpGs and these serve as hot spots for mutations in some, but not all, human cancers. Comparison of the spectrum of mutations present in this gene in different human cancers allows for predictions to be made on the molecular mechanisms of tumorigenesis.
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PMID:Methylation, mutation and cancer. 154 79

Mutations in the p53 tumour-suppressor gene are the most frequently observed genetic lesions in human cancers. To investigate the role of the p53 gene in mammalian development and tumorigenesis, a null mutation was introduced into the gene by homologous recombination in murine embryonic stem cells. Mice homozygous for the null allele appear normal but are prone to the spontaneous development of a variety of neoplasms by 6 months of age. These observations indicate that a normal p53 gene is dispensable for embryonic development, that its absence predisposes the animal to neoplastic disease, and that an oncogenic mutant form of p53 is not obligatory for the genesis of many types of tumours.
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PMID:Mice deficient for p53 are developmentally normal but susceptible to spontaneous tumours. 155 40

Recent studies have provided the first clues as to the molecular mechanisms responsible for bladder carcinogenesis. Cytogenetic and molecular studies have demonstrated nonrandom changes of chromosomes 1, 5, 7, 9, 11, and 17. The finding of monosomy of chromosome 9 in early noninvasive lesions has initiated a search for a bladder-specific gene responsible for bladder oncogenesis. Activation of ras and erbB oncogenes has been reported, although the role that these changes play in bladder cancer is not yet understood. Inactivation of two well-characterized tumor suppressor genes, p53 and Rb, also appears to be important in the pathogenesis of bladder cancer, and evidence suggests that inactivation of p53 correlates with the acquisition by bladder cancer cells of the invasive phenotype. Although the picture is far from complete, it is clear that for the first time an understanding of the molecular events responsible for bladder cancer is possible, and that this information will have clinical impact on patients in the near future.
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PMID:Molecular biology of bladder cancer. 155 51


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