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

Cancer is generally understood to be a genetic disease in the sense that somatic mutations are the cause of tumour initiation and development. Our knowledge of cancer-associated genes and gene products has evolved mainly over the past 20 years. The identification and characterization of tumour suppressor genes (TSGs) as normal growth-inhibiting or apoptosis-inducing genes have helped us to understand how mutations are tumorigenic. Various TSG encoding membrane-, cytosol-, or nuclear proteins have been identified. Tumor suppressor genes are often functionally inactive in cancer cells because of mutations of both parental gene copies. Many TSGs are associated with hereditary cancer diseases or syndromes caused by the existence of one mutant allele in the germ-line. Individuals who carry only one functional gene copy, are therefore at great risk of developing cancer. Several TSGs, such as TP53, RB1 and CDKN2A, encode proteins that are significant to the cell cycle. TP53 is the most frequently mutated gene in human cancer, showing changes in more than 50% of all solid tumours. Both DNA repair and apoptosis are stimulated by p53-induced transcription of genes involved in the two processes. The characterization of TSGs and their gene products has led to the identification of a number of new diagnostic and prognostic molecular genetic parameters in oncology. Furthermore, some TSGs are potentially among the most promising and important targets for gene therapy in cancer and other hyperproliferative diseases.
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PMID:[Tumor suppressors--genes and proteins]. 963 59

Tumor suppressor genes are generally viewed as being recessive at the cellular level, so that mutation or loss of both tumor suppressor alleles is a prerequisite for tumor formation. The tumor suppressor gene, p53, is mutated in approximately 50% of human sporadic cancers and in an inherited cancer predisposition (Li-Fraumeni syndrome). We have analyzed the status of the wild-type p53 allele in tumors taken from p53-deficient heterozygous (p53+/-) mice. These mice inherit a single null p53 allele and develop tumors much earlier than those mice with two functional copies of wild-type p53. We present evidence that a high proportion of the tumors from the p53+/- mice retain an intact, functional, wild-type p53 allele. Unlike p53+/- tumors which lose their wild-type allele, the tumors which retain an intact p53 allele express p53 protein that induces apoptosis following gamma-irradiation, activates p21(WAF1/CIP1) and Mdm2 expression, represses PCNA expression (a negatively regulated target of wild-type p53), shows high levels of binding to oligonucleotides containing a wild-type p53 response element and prevents chromosomal instability as measured by comparative genomic hybridization. These results indicate that loss of both p53 alleles is not a prerequisite for tumor formation and that mere reduction in p53 levels may be sufficient to promote tumorigenesis.
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PMID:Retention of wild-type p53 in tumors from p53 heterozygous mice: reduction of p53 dosage can promote cancer formation. 970 25

Patients with Barrett's columnar-lined esophagus are at increased risk of developing esophageal adenocarcinoma, the incidence of which has increased rapidly especially in the USA. Although the number of patients with Barrett's adenocarcinoma is fewer in Japan than in the USA, all gastroenterologist should know its multistep carcinogenic process. Tumor suppressor genes (p53, p16), oncogenes (c-erbB-2, H-ras, K-ras, cyclin D1, src), and growth factor/receptor (TGF-alpha, EGFR) seem to cause the malignant transformation of Barrett's esophagus. Because detection of these molecular alterations is feasible, more accurate diagnosis of Barrett's esophageal biopsy specimens should be made by adding the molecular examination to the conventional pathologic examination.
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PMID:[Molecular alterations in Barrett's esophagus and adenocarcinoma]. 1037 32

Soft tissue sarcomas are relatively rare tumors that are generally treated with a multimodality approach including surgery, chemotherapy, and radiation therapy. Despite this aggressive tri-modality therapy, greater than 50% of soft tissue tumors will recur and result in diffuse metastatic spread of disease and ultimately death of the patient. It is this clinical scenario that drives the development of preclinical experimental studies designed to explore alternative treatments or enhance the effectiveness of existing therapies. Rapid developments in the field of molecular biology have led to the understanding of basic cellular processes governed by oncogenes and tumor suppressor genes. These cellular genes are sometimes overexpressed, mutated or even deleted from tumor cells. Cytogenetic analysis has led to the discovery of sarcoma fusion genes which encode for oncoproteins peculiar to specific subtypes of soft tissue sarcomas. These fusion genes have proved to be helpful in terms of diagnostic dilemmas and are now being used as targets in treatment strategies aimed at suppression of the cellular expression and action of these oncoproteins. Tumor suppressor genes such as p53 and the retinoblastoma tumor suppressor play important roles in growth inhibition and cell cycle progression. These tumor suppressors are often mutated or deleted in soft tissue sarcomas. Using gene therapy strategies, p53 can be reintroduced into sarcoma cells and has been shown to result in a dramatic decrease in cell survival. It also appears that p53 may sensitize these tumor cells to radiation and chemotherapy agents. Strategies which can drive tumor cells into programmed cell death pathways are also showing promise as novel treatment approaches to soft tissue sarcomas. This review will highlight some of the current research exploring novel treatment strategies aimed at molecular targets. Further development of these and other preclinical experimental programs are important in improving the outcome for patients with these rare soft tissue tumors.
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PMID:Preclinical experimental therapeutic approaches in soft tissue sarcoma. 1040 41

Tumor suppressor genes p53 and Rb are important in cell cycle control. Necessity of wild type p53 is implicated in irradiation-induced apoptosis. Numerous tumor cells carry p53 mutations and yet are sensitive to irradiation or chemotherapeutic agents. Therefore p53-and Rb-independent pathways must exist to account for irradiation-induced apoptosis. We evaluated the apoptotic response of a p53- and Rb-mutated, Human Papilloma Virus (HPV) negative cervical cancer cell line (C33a), and C33a cell lines infected with HPV 18 oncoproteins E6, E7, and E6&7 using recombinant retrovirus to various apoptosis-inducing agents including gamma irradiation, mitomycin C (MMC), and staurosporine (SSP). Apoptosis was measured by avidinebiotin tunnel staining method. Our results showed significant apoptosis in C33a cell lines in response to gamma-irradiation, MMC, and SSP. Moreover, apoptosis was enhanced when HPV 18 E6, and E6&7 infected C33a cell lines were treated with irradiation, MMC, and SSP. HPV 18 E7 infected C33a cell lines enhanced the apoptotic response to irradiation and to MMC, but not to SSP. In conclusion, our results imply the presence of a p53- and Rb-independent pathway in irradiation-induced apoptosis in cervical cancer cell lines: this effect is even more evident in HPV oncoprotein infected cell lines. The radiosensitizing effects of HPV oncoproteins may lead to new perspectives in the treatment of cervical cancer.
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PMID:Human papillomavirus 18 oncoproteins E6 and E7 enhance irradiation- and chemotherapeutic agent-induced apoptosis in p53 and Rb mutated cervical cancer cell lines. 1041 Aug 76

Paraffin-embedded samples from cervical adenocarcinomas, 19 cases from Irish patients and 19 cases from Swedish patients, were analyzed by polymerase chain reaction for the presence of infection with human papillomavirus (HPV). The results were compared with DNA ploidy, proliferation activity, and p53 and p21/WAF1 expression. The studies were performed to discover whether high-risk HPV infection in adenocarcinomas of the uterine cervix is associated with an increased proliferative activity and genomic instability. The results show that the majority (84.6%) of patients 59 years of age or younger showed HPV infection. The overall prevalence of HPV DNA was 60.5%, with the high-risk types, 16 and 18, the most frequent. HPV-16 had a prevalence of 23.7% (9 of 38), and HPV-18 had a prevalence of 26.3% (10 of 38). The HPV-positive tumors predominantly showed a tetraploid DNA distribution pattern, whereas HPV-negative tumors more frequently showed highly scattered aneuploid DNA profiles. Both HPV-positive and HPV-negative cases displayed high proliferative activity, as indicated by high Ki-67 and cyclin A immunoreactivity. Tumor suppressor gene analysis detected low p53 expression and high p21/WAF1 expression in HPV-positive patients and high p53 expression without simultaneously increased p21/WAF1 (indicative of mutated p53) in HPV-negative cases in the groups of women older than 59 years of age.
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PMID:Adenocarcinoma of the uterine cervix in Ireland and Sweden: human papillomavirus infection and biologic alterations. 1043 Feb 71

Tumor suppressor genes are implicated in cell cycle progression. Inactivation of these genes predominantly occurs through mutations and/or allelic loss that involves both alleles. With inactivation by multiple mutations in a single gene, cloning of the amplified gene is necessary to determine whether the mutations reside on one or both alleles. Using pyrosequencing, a recently developed approach based on sequencing-by-synthesis, we studied genetic variability in the p53 tumor suppressor gene and could quantify the ratio between the mutated and wild-type amplified fragments. Furthermore, this sequencing technique also allows allelic determination of adjacent mutations with no cloning of amplified fragments.
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PMID:Analysis of the p53 tumor suppressor gene by pyrosequencing. 1064 85

Twelve well-differentiated villoglandular adenocarcinomas (WDVAs) of the uterine cervix were retrospectively analyzed for the presence and specific genotype of human papillomavirus (HPV), tumor suppressor loss (p53, MCC, APC, BRCA1), cancer gene mutation (K-ras-2, exons 1 and 2, p53 exons 5 to 8), and oncogene amplification (c-erbB-2/HER-2/neu, int-2). Tissue for genetic evaluation was obtained by microdissection, using 4-micron-thick histology sections of archival, formalin-fixed, paraffin-embedded specimens. Genotyping involved nucleic acid amplification and DNA sequencing with gene-specific oligonucleotides and L1 region consensus primers for common strains of HPV. Point mutation and HPV strain determination were accomplished by DNA sequence analysis. Tumor suppressor gene loss and oncogene amplification were performed by allelic imbalance analysis in informative subjects based on DNA sequence and microsatellite-length polymorphisms. HPV was present in all tumors and consisted of type 16 (n = 5, 42%) and type 18 (n = 7, 58%) strains, which have been closely associated with cervical neoplasia. K-ras-2 and p53 genes did not manifest point mutational damage. There was no evidence of oncogene amplification or tumor suppressor gene loss. The presence of HPV in all 12 tumors supports the role of HPV infection in the molecular pathogenesis of this uncommon neoplasm. The absence of associated oncogene or tumor suppressor gene damage is consistent with indolent biological behavior and the favorable prognosis of this unusual tumor.
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PMID:Well-differentiated villoglandular adenocarcinoma of the uterine cervix: oncogene/tumor suppressor gene alterations and human papillomavirus genotyping. 1078 6

Carcinoma of the larynx is responsible for 1% of all tumors and for 25% of oncologic disease of the head and neck. Tumor suppressor genes control cell proliferation by suppressing specific mechanisms that stimulate the proliferative response. Rb and p53, both nuclear, are the most studied tumor suppressor genes. We evaluated the immunoexpression of these markers in 72 carcinomas of the larynx and correlated it with patients' clinical parameters: age, sex, occupation, tobacco and alcohol use, marital status, etc. Biological and anatomopathological parameters (tumor stage, histological type, degree of local invasion, and lymph node metastases) also were studied. Statistically significant differences were found in mean immunostaining for the Rb gene with respect to histological grade, lymph node enlargement, and smoking. We observed no positive correlation between p53 and the classic clinical-pathological parameters, although important trends were evident, as well as relatively frequent immunostaining (about 40%) of the total neoplastic population.
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PMID:[Immunohistochemical expression of P53 suppressor genes and retinoblastoma in laryngeal carcinoma]. 1080 15

This study was designed to elucidate the mechanism underlying the inhibition of endothelial cell growth by laminar shear stress. Tumor suppressor gene p53 was increased in bovine aortic endothelial cells subjected to 24 h of laminar shear stress at 3 dynes (1 dyne = 10 microN)/cm(2) or higher, but not at 1.5 dynes/cm(2). One of the mechanisms of the shear-induced increase in p53 is its stabilization after phosphorylation by c-Jun N-terminal kinase. To investigate the consequence of the shear-induced p53 response, we found that prolonged laminar shear stress caused increases of the growth arrest proteins GADD45 (growth arrest and DNA damage inducible protein 45) and p21(cip1), as well as a decrease in phosphorylation of the retinoblastoma gene product. Our results suggest that prolonged laminar shear stress causes a sustained p53 activation, which induces the up-regulation of GADD45 and p21(cip1). The resulting inhibition of cyclin-dependent kinase and hypophosphorylation of retinoblastoma protein lead to endothelial cell cycle arrest. This inhibition of endothelial cell proliferation by laminar shear stress may serve an important homeostatic function by preventing atherogenesis in the straight part of the arterial tree that is constantly subjected to high levels of laminar shearing.
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PMID:Molecular mechanism of endothelial growth arrest by laminar shear stress. 1092 Feb 9


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