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)

Chemically-induced rodent tumor models help us to understand a series of genetic changes during carcinogenesis. In this study, we present N-nitroso-N-butylurea (NBU)-induced rat leukemia and compare it with the genetic alterations found in 7,12-dimethylbenz[a]anthracene (DMBA)-induced erythroblastic leukemias which consistently have an A to T transversion at the second base of codon 61 in N-ras. By continuous NBU treatment for 120-150 days, 14 primary leukemias were induced in Long-Evans rats. Myeloblastic leukemia cells predominantly increased in all rats except in one case which predominantly had erythroblastic leukemia cells. Point mutations of Ha-, Ki-, N-ras and p53 were determined after RNA was transcribed into cDNA and this cDNA was used as a substrate for polymerase chain reaction (PCR) which was eventually sequenced. No abnormalities in exons 1 and 2 of Ha-, Ki- and N-ras were detected in all leukemias. In the p53 gene, an A to C transition was found at the second base of codon 198 (Asn-Thr) in one leukemia, but others had no mutation. These results suggest that ras and p53 genes are infrequently involved in NBU-induced leukemias. The genetic target of NBU during leukemogenesis seemed to be different from that of DMBA.
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PMID:ras and p53 genes are infrequently involved in N-nitroso-N-butylurea (NBU)-induced rat leukemia. 950 Feb 11

The role of tumor suppressor genes and oncogenes in the development of Ewing's sarcoma has not yet been fully clarified. In this study, we analyzed the frequency of p53 tumor suppressor gene mutation in exons 4-8 by PCR-SSCP and direct sequencing, and the expression of p53-protein in Ewing's sarcoma (ES) by using immunohistochemistry. The overexpression of MDM2, which acts as a functional inactivator of p53, was studied by immunohistochemistry. In addition, a screening for point mutations in the hot spot regions codon 12 and 13 of exon 1 and codon 61 of exon 2 of ras-genes (H-ras, N-ras, K-ras) was performed. In one case, a p53 gene mutation could be confirmed in codon 238 of exon 7 (1/24). Overexpression of MDM2 was found in five cases; in ras-genes, no mutations were detected. Compared with other highly malignant mesenchymal pediatric tumors such as osteosarcomas, mutations of p53 and ras in Ewing's sarcomas are an extraordinarily rare event. However, their frequency is comparable to that of PNET, suggesting that the low incidence of these mutations in ES and PNET could be group-specific for tumors of neuroectodermal genesis.
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PMID:p53 and ras mutations in Ewing's sarcoma. 958 33

Ethylene oxide is a proven genotoxic chemical, and there is lots of evidence suggesting its carcinogenic effects in humans. The unexpected massive appearance of a certain tumorous cluster in personnel exposed to ethylene oxide in a Hungarian county hospital focused attention on the effects of this toxic gas. Since we had developed an animal model for the investigation of alterations in onco/suppressor gene expression due to external carcinogenic agents, and this model had already been used to evaluate the carcinogenic effects of cytostatic drugs in humans, an analysis of the effects of ethylene oxide exposure seemed to offer further information on the usefulness of gene expression as a biomarker. The main purpose of our study was to determine whether or not ethylene oxide exposure causes an elevated expression of onco/suppressor genes in the white blood cells of exposed people. Two different exposed groups and one control group were included in the study. The N-ras and p53 genes were chosen for the investigations of gene expression. N-ras is known to be activated in several tumor types, and p53 is also involved in carcinogenesis and plays an important role in the cellular answer mechanism to exogenous toxic effects. RNA was isolated from the white blood cells, slot blotted onto nitrocellulose membranes, and hybridized with chemoluminescently labeled gene probes. The results were detected on X-ray films and scanned into a computer, and relative risk for elevated gene expression was calculated in each group. Elevated N-ras and detectable p53 expressions were observed more frequently in both exposed groups compared with the control group (relative risks--N-ras: 1.57 [0.77-3.22] and 2.34 [1.21-4.52]; p53: 6.67 [2.35-18.92] and 6.06 [2.10-17.49]).
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PMID:Oncogene and suppressor gene expression as a biomarker for ethylene oxide exposure. 961 46

Analysis of H-, K- and N-ras genes for point mutations by PCR-SSCP and direct sequencing of 46 oral SCCs that were previously analyzed for p53 mutations revealed that 9 (20%) had point mutations in either the H-ras or the N-ras. A novel mutation at codon 59 (GCC-ACC) of H-ras thus far reported only in v-H-ras of Harvey murine sarcoma virus was observed in a tumor of the cheek. Majority (8/9) of these mutations were observed in H-ras, one in N-ras and none in K-ras. This study indicated that the ras gene mutation was relatively high in oral cancers associated with tobacco chewing and the ras and p53 mutational events seem to be independent and mutually exclusive.
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PMID:Detection of a rare point mutation at codon 59 and relatively high incidence of H-ras mutation in Indian oral cancer. 977 88

Two molecular pathways leading to cancer are known. Common-type cancers arise from the 'tumour suppressor' pathway, characterized by gross chromosomal changes and allelic losses (LOH) in an average of 25 per cent or more of randomly chosen chromosomal loci. The 'mutator pathway' has been recognized in a subset of cancers, characterized by widespread microsatellite DNA instability and rarity of chromosomal losses. The present study has investigated 20 pancreatic endocrine tumours (PETs) for loss of heterozygosity (LOH) at seven chromosomal loci (3p14, 7q31-32, 11q13, 13q14, 18q21, 17p13, and 17q21); microsatellite instability; and Ki-ras, N-ras, and p53 gene mutations. LOH was found in an average of 24 per cent of the chromosomal loci analysed. No tumour showed microsatellite instability. Ki-ras and p53 mutations were each found in one case. The frequency of losses was higher in malignant (40 per cent) than in benign (17 per cent) tumours (p = 0.009), and the specific chromosome 17p13 LOH was associated with extrapancreatic extension of disease (p = 0.007), high proliferative activity (p = 0.001), and absence of progesterone receptors (p = 0.01). A common deleted region on chromosome 17p13 and the rarity of p53 gene mutations suggest the existence of a novel tumour suppressor gene involved in the pathogenesis of PETs in this chromosomal area.
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PMID:Pancreatic endocrine tumours: evidence for a tumour suppressor pathogenesis and for a tumour suppressor gene on chromosome 17p. 987 39

Although most gallbladder carcinomas evolve from dysplasia and carcinoma in situ, the role of gallbladder adenomas in the pathogenesis of gallbladder carcinoma is still controversial. A series of molecular changes including loss of heterozygosity (LOH) at 17p (TP53 gene), 13q (RB gene), 18q (DCC gene), and 9p21 (CDKN2a gene) chromosomal regions have been identified in dysplasias, carcinomas in situ, and invasive carcinomas of the gallbladder, whereas mutations in K- and N-ras genes are rare. To determine whether the molecular abnormalities of adenomas are similar to those found in carcinomas, we obtained extracted DNA from precisely microdissected tissue from 16 gallbladder adenomas (14 pyloric and 2 intestinal-type). We determined the presence of mutations in TP53, K- and N-ras genes, and LOH at five chromosomal regions (5q22 APC-MCC region, RB, TP53, DCC and 9p21-CDKN2a). For the TP53 mutation study, single strand conformational polymorphism (SSCP) analysis in exons 4 to 8 were performed. K- and N-ras mutations detection was performed by designed restriction fragment length polymorphism (RFLP) method and sequencing. Only a single LOH (at 5q22) was detected in a gallbladder adenoma of intestinal type. No mutations at the TP53 were detected. Four adenomas (25%) showed K-ras mutations (two in codon 12 and two in codon 61). We conclude that gallbladder adenoma lacks the molecular changes frequently detected in dysplasia, carcinoma in situ, and invasive carcinoma of the gallbladder. Likewise the occurrence of K-ras mutations at codon 12 and 61 in 25% of adenomas strongly suggests that these lesions are not precursors of invasive gallbladder carcinoma.
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PMID:Gallbladder adenomas have molecular abnormalities different from those present in gallbladder carcinomas. 992 22

Four case reports of mesenchymal neoplasms showing chromosomal abnormalities are presented. In a case of hemangiopericytoma trisomy 2 and centric fusion 19;21 were present. In a mastocytoma a deleted chromosome 35 was seen. A homogeneously staining region (HSR) on chromosome 1 was detected in a histiocytoma. Trisomy 5 and monosomy 31 were observed in a case of granulocytic sarcoma (chloroma). The lack of mutations in exons 1 and 2 of oncogenes N-ras, K-ras, and H-ras and exons 5, 6, 7, and 8 of tumor suppressor gene p53 in these four patients and in a larger series of investigated dogs (25 hemangiopericytomas, 12 mastocytomas, and 8 histiocytomas) is highlighted.
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PMID:Cytogenetic, ras, and p53: studies in cases of canine neoplasms (hemangiopericytoma, mastocytoma, histiocytoma, chloroma). 998 18

In melanoma, the relationship between sun exposure and the origin of mutations in either the N-ras oncogene or the p53 tumour-suppressor gene is not as clear as in other types of skin cancer. We have previously shown that mutations in the N-ras gene occur more frequently in melanomas originating from sun-exposed body sites, indicating that these mutations are UV induced. To investigate whether sun exposure also affects p53 in melanoma, we analysed 81 melanoma specimens for mutations in the p53 gene. The mutation frequency is higher than thus far reported: 17 specimens (21%) harbour one or more p53 mutations. Strikingly, 17 out of 22 mutations in p53 are of the C:G to TA or CC:GG to TT:AA transitional type, strongly suggesting an aetiology involving UV exposure. Interestingly, the p53 mutation frequency in metastases was much lower than in primary tumours. In the case of metastases, a role for sun exposure was indicated by the finding that the mutations are present exclusively in skin metastases and not in internal metastases. Together with a relatively frequent occurrence of silent third-base pair mutations in primary melanomas, this indicates that the p53 mutations, at least in these tumours, have not contributed to melanomagenesis and may have originated after establishment of the primary tumour.
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PMID:p53 mutations in human cutaneous melanoma correlate with sun exposure but are not always involved in melanomagenesis. 1007 Aug 91

We have examined 63 methylcholanthrene (MCA)-induced mouse sarcomas for possible correlations of mutations involving the c-myc, ras and p53 genes. The c-myc gene was found to be amplified in 18 of these sarcomas (29%). Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis and subsequent direct sequencing identified 18 cases carrying K-ras mutation at codons 12, 13 and 61 (29%). No mutation was detected in the H-ras and N-ras genes. Mutations of the p53 gene in exons 5 to 8 were found in 45 cases (71%). Comparison of these mutations revealed that out of 18 cases with c-myc gene amplifications, 10 carried K-ras mutations (56%) and 14 carried p53 mutations (78%). In contrast, among 45 cases of sarcomas without c-myc gene amplification, 8 were found to have K-ras mutations (18%). The same 45 cases were found to have 31 p53 mutations (69%). The present study suggests a strong correlation between c-myc gene amplification and K-ras gene mutation (P < 0.01). p53 gene mutation was frequently found among MCA-induced mouse sarcomas, indicating the importance of this mutation in the etiology of these tumors. However, p53 mutations were present in sarcomas regardless of the state of c-myc amplification and K-ras mutation. Therefore, a defect in the p53 gene is independent of amplification of the c-myc gene or point mutation of the K-ras gene.
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PMID:Analysis of the c-myc, K-ras and p53 genes in methylcholanthrene-induced mouse sarcomas. 1007 63

Relapse is a major cause of treatment failure in acute myeloid leukaemia (AML), and is usually accompanied by resistance to chemotherapy. To study whether relapse is accompanied by genetic alterations, we compared N-ras, p53 and FLT3 gene mutations in paired samples obtained at initial diagnosis and first relapse. 28 patients with relapsed AML were studied, and their duration of complete remission ranged from 133 to 989 d (mean 318 d). Karyotype changes were observed at relapse in 11 patients. Point mutations of the N-ras gene were positive at both stages (+/+) in three patients, positive at initial diagnosis and negative at relapse (+/-) in three patients, and negative at initial diagnosis and positive at relapse (-/+) in two patients. Internal tandem duplications of the FLT3 gene (FLT3/ITD) were +/+ in five patients, +/- in one patient, and -/+ in six patients. The p53 gene mutations were +/+ in two patients, +/- in one patient, and -/- in 25 patients. FLT3/ITD and mutant p53 at relapse were associated with short survival after relapse. These results indicate that relapse is frequently accompanied by molecular alterations that include the loss and/or acquisition of mutations. Thus relapse can be understood as clonal shift or collateral succession rather than clonal progression.
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PMID:Molecular evolution of acute myeloid leukaemia in relapse: unstable N-ras and FLT3 genes compared with p53 gene. 1019 23


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