Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Overexpression of mouse wild-type p53 (wt p53) in mouse Meth A tumor cells after transfection of wt p53 encoding vectors induced a strong growth-inhibitory response. Cells of only few of randomly selected surviving colonies contained and expressed the transfected wt p53 specific DNA. Despite expressing authentic wt p53, such cells (MethAp53wt) exhibited a similar phenotype as the parental Meth A cells. These cells overexpressed the mdm-2 (mouse double minute-2) gene, both at the RNA and at the protein level. Recently, the MDM-2 protein has been identified as a cellular target of p53, which can abolish its tumor suppressor activity. We, therefore, suggest that MDM-2 has mitigated the growth-inhibitory effect of wt p53 in MethAp53wt cells. Upregulation of mdm-2 expression in MethAp53wt cells was mediated by wt p53, as analysis of Meth A cells carrying a tsp53 (p53Val135) revealed a strict dependence of mdm-2 upregulation upon wt p53 expression. Our results propose that a balanced ratio of MDM-2 and p53 will allow cells to tolerate a limited expression of wt p53. This tolerance is not mediated by a direct inactivation of wt p53 via complex formation with MDM-2, as the majority of both MDM-2 and wt p53 in MethAp53wt cells was not complexed to each other.
 ...
PMID:Upregulation of mdm-2 expression in Meth A tumor cells tolerating wild-type p53. 836 69

We report that p53her, a chimeric protein consisting of the complete human wild-type p53 and the human estrogen receptor hormone-binding domain, strongly suppresses proliferation and induces characteristic morphological changes in Saos-2 human osteosarcoma cells when induced by 17 beta-estradiol. In contrast, p53her constitutively transactivates a p53-responsive promoter in transfection assays, so that transactivation is not regulated by estradiol. However, coexpression of p53her and oncoprotein MDM-2, which associates with and presumably inactivates p53, results in suppression of p53her-mediated transactivation in the absence, but not the presence, of estradiol. Similarly, p53her induces expression of an endogenous MDM-2 transcript only in the presence of estradiol. These results suggest a correlation between the growth suppressor function of p53her and release of a transactivation block mediated by MDM-2.
 ...
PMID:Modulation of cell proliferation and gene expression by a p53-estrogen receptor hybrid protein. 841 87

p53 is multifunctional. To assess exactly what function is critical for the prevention of neoplastic transformation has proven difficult. Mutants with substitutions at positions 22 and 23 promised to address the relevance of transcription transactivation since they seemed to be defective specifically for this function. We report here that p53 mutant Q22, S23 [p53 (22,23)] is not only impaired for transactivation but for the repression of the fos promoter and SV40 early promoter. Furthermore, whereas p53 (22,23) fails to efficiently transactivate reporter genes in two p53-negative cell lines, it stimulates reporters and suppresses proliferation in two wild-type (wt) p53-positive cell lines strongly above the levels induced by the transfection procedure alone. This transactivation is refractory to inhibition by MDM-2. Finally, p53 (22,23) expressed from large plasmid quantity (1 microg) is crippled for the mediation of apoptosis in p53-negative Hep3B hepatocarcinoma cells. Nevertheless, at a quantity of only 10 ng, both mutant and wt p53 plasmids but not control plasmid, are able to induce some cell death which is not inhibitable by MDM-2. Thus, a correlation exists between p53's functions to regulate promoters and to efficiently mediate apoptosis in Hep3B cells.
 ...
PMID:p53 transactivation domain mutant Q22, S23 is impaired for repression of promoters and mediation of apoptosis. 866 32

MDM-2 is a cellular oncoprotein that binds to the p53 protein and abrogates its growth-suppressing function. At least seven MDM-2 mRNAs and five proteins (p90, p85, p76, p74, and p57) have been reported in tissue culture. MDM-2 gene amplification occurs in human sarcomas and high-grade gliomas. MDM-2 overexpression without gene amplification has been reported in leukemias and lymphomas. Here we report MDM-2 mRNA overexpression in 24 (73%) out of 33 cases of human breast carcinoma as compared with normal breast tissue. The MDM-2 overexpression was seen in the absence of MDM-2 gene amplification. MDM-2 protein expression was studied by western blot analysis in 21 of these cases of carcinoma. We found complete concordance between MDM-2 mRNA overexpression and MDM-2 protein levels. MDM-2 proteins were overexpressed in 15 of 21 breast carcinoma tissue samples but not in normal breast tissue controls. Ten of these fifteen cases overexpressed MDM-2 p57 protein, two cases overexpressed both p57 and p90, and three cases overexpressed only p90. MDM-2 overexpression was confirmed by immunohistochemistry. p53 overexpression was also studied by immunohistochemistry, 69% of breast carcinomas that overexpressed the MDM-2 mRNA had detectable nuclear p53 protein. These findings demonstrate that MDM-2 oncoprotein expression is altered in primary human breast carcinomas at both mRNA and protein levels. In addition, our results suggest that MDM-2 p57 protein represents the main MDM-2 protein altered in breast carcinomas.
 ...
PMID:Abnormal expression of MDM-2 in breast carcinomas. 875 May 85

p53 has been shown to suppress tumor growth by regulating the cell cycle and by triggering apoptosis. Acquired somatic mutations of the p53 gene have been observed in a variety of human malignancies, and these result in a loss of its tumor suppressor function. To examine the occurrence of p53 abnormalities in bone and soft tissue sarcomas, 113 tumors were subjected to molecular analysis and mutations were confirmed in 16 tumors. The frequency of p53 alterations varied among the different subtypes of bone and soft tissue sarcomas, being observed predominantly in osteosarcomas (8/34 cases), rhabdomyosarcomas (2/3 cases), Ewing's sarcomas (1/5 cases), and liposarcomas (3/21 cases). In contrast, p53 gene mutations were detected at a lower frequency in malignant fibrous histiocytomas (2/34 cases) and not at all in nine chondrosarcomas and five leiomyosarcomas. Immunohistochemical staining of p53 protein was performed on 69 cases and compared to the DNA results. For 64 cases the results were concordant: 56 sarcomas were considered to have wild-type p53 by both techniques. As well, increased p53 protein expression was observed in eight of the nine tumors with p53 gene mutations. However, positive p53 staining was also seen in four sarcomas which had no detectable p53 mutations in exons 5 through 9. Because some sarcomas exhibit amplification and overexpression of MDM-2, which may interact with p53 and cause stabilization of wild-type p53 protein, we examined these tumors for MDM-2 amplification. None of the tumors with MDM-2 amplification exhibited p53 immunopositivity. Very weak p53 reactivity was detected in four malignant fibrous histiocytomas that had received either chemotherapy or radiotherapy. Of 16 metastatic lesions examined, only one contained a p53 mutation. In addition, for five cases in which both the original lesion and its metastases were analyzed, p53 alterations were not observed in the metastases if the tumor was wild-type at presentation. These data suggest that p53 alterations occur at different frequencies in various subtypes of sarcoma and, although detected in metastatic lesions, are not associated more frequently with progression.
 ...
PMID:Molecular and immunohistochemical identification of p53 alterations in bone and soft tissue sarcomas. 882 48

Here we report the isolation of a cDNA encoding a new p53-associating protein. This new protein has been called MDMX on the basis of its structural similarity to MDM2, which is especially notable in the p53-binding domain. In addition, the putative metal binding domains in the C-terminal part of MDM2 are completely conserved in MDMX. The middle part of the MDMX and MDM2 proteins shows a low degree of conservation. We can show by co-immunoprecipitation that the MDMX protein interacts specifically with p53 in vivo. This interaction probably occurs with the N-terminal part of p53, because the activity of the transcription activation domain of p53 was inhibited by co-transfection of MDMX. Northern blotting showed that MDMX, like MDM2, is expressed in all tissues tested, and that several mRNAs for MDMX can be detected. Interestingly, the level of MDMX mRNA is unchanged after UV irradiation, in contrast to MDM2 transcription. This observation suggests that MDMX may be a differently regulated modifier of p53 activity in comparison with MDM2. Our study indicates that at least one additional member of the MDM protein family exists which can modulate p53 function.
 ...
PMID:MDMX: a novel p53-binding protein with some functional properties of MDM2. 889 79

The MDM-2 (murine double minute 2) gene codes for a cellular protein that can bind to the p53 tumor suppressor gene product, thereby functioning as a negative regulator of p53. In order to define the role of the MDM-2 gene in the pathogenesis of human acute myeloid leukemia, the expression and the sequence of the MDM-2 gene were examined in samples of bone marrow and/or peripheral mononuclear cells of 38 patients by using immunostaining, polymerase chain reaction (PCR), single strand conformation polymorphism, and sequencing. Immunohistochemical staining detected a weak accumulation of the MDM-2 protein in AML patients of FAB classification M4 and M5. RT-PCR analysis revealed a heterogeneous expression pattern of MDM-2 mRNA in AML samples of different FAB classification. An increased level of MDM-2 mRNA expression was observed in 17 of 38 AML patients when compared to normal controls. No structural changes in a 488 bp region extending from nucleotide 890 to 1378 of the MDM-2 cDNA were detected using RT-SSCP and sequence analysis. In addition, heterogeneous expression of p53 transcripts was found with the highest p53 mRNA levels in AML M4 and M5. Interestingly, there seems to be a correlation between the relative ratios of p53 and MDM-2 mRNA levels in AML M4 and M5: in 15 of 23 cases high p53 mRNA expression was directly associated with high levels of MDM-2 transcripts. An exclusively intranuclear p53 immunostaining pattern was found in 10 of 16 (58%) AML FAB M4 and M5, whereas the remaining AML samples tested were negative for p53 (0/10). Using RT-SSCP analysis and direct sequencing of the RT-PCR amplification products of p53 exon 5-8, we observed that only 1 of 38 AML patients showed a point mutation in the p53 gene. This missense mutation occurred in the evolutionary highly conserved region of p53 at codon 255 (Ile to Phe). These data indicated that structural alterations of the p53 gene do not play an important role in the initiation and progression of AML. However, abrogation of p53 tumor suppressor function due to MDM-2 overexpression may be an alternative molecular mechanism by which a subset of AMLs may escape from p53-regulated growth control.
 ...
PMID:Analysis of the p53 and MDM-2 gene in acute myeloid leukemia. 889 28

Hodgkin's disease (HD) is characterized by the presence of the typical, clonal malignant Hodgkin and Reed-Sternberg (H-RS) cells in a hyperplastic background of normal reactive lymphocytes, plasma cells, histiocytes, neutrophils, eosinophils and stromal cells. The neoplastic nature of HD is based on aggressive clinical progression, presence of the proliferating and atypical H-RS cells, aneuploidy and cellular clonality. Immunophenotypical studies have demonstrated frequent expression of lymphoid "activation markers' including CD15, CD25, CD30, CD40, CD54, CD70, CD71, CD80, CD86 and MHC class II and less frequent expression of T- or B-cell-associated antigens by the neoplastic H-RS cells. The clonality of H-RS cells is demonstrated by clonal EBV integration, clonal cytogenetic abnormalities including p53 mutations and clonal immunoglobulin rearrangements in some HD cases. There is involvement of diverse molecules with oncogenic potential, including presence of viruses (Epstein-Barr virus and human herpes virus-6) and/or oncogenes/tumour suppressor genes (bcl-2/bcl-x, p53/MDM-2, c-myc, c-fms, N-ras, lck). The histopathological presentation and characteristic clinical features of HD correlate with an unbalanced production of multiple cytokines and define HD as a tumour of cytokine-producing cells. The proportion of malignant H-RS cells to reactive cellular components and fibrosis is dependent on the production of particular cytokines and allows subtyping of HD cases. The combined use of immunohistochemical, biochemical and molecular techniques has thus allowed recognition that HD represents more than one clinico-pathological entity with different types of H-RS cells. The defined mechanism for the biological nature, origin and oncogenesis of H-RS cells remains not fully understood, but is susceptible to further analysis using modern technology.
 ...
PMID:Pathophysiology of Hodgkin's disease: functional and molecular aspects. 892 38

The MDM-2 oncoprotein exists in an autoregulatory feedback loop with the tumor suppressor protein p53. Therefore, intracellular levels of these two proteins may play important roles in cell proliferation and tumorigenesis. Several MDM-2 proteins (Mr 35-100 Kd) have been demonstrated in human cell lines. We report here the expression profile of MDM-2 and p53 proteins in 87 cases of chronic lymphocytic leukemia (CLL) as detected by immunoblot analysis. The MDM-2 proteins (p57, p59, p67, and p90) were found to be overexpressed in different combinations in 56/87 (64%) of cases of CLL when compared with normal volunteers. The MDM-2 protein p57 was predominantly overexpressed 46/87 (53%) in CLL. In 22/87 (25%) cases of CLL p57 was overexpressed alone, and in 24/87 (28%) cases it was co-overexpressed with other MDM-2 proteins p59/p67/p90. Six of the 87 cases of CLL showed overexpression of the tumor suppressor protein p53 by immunoblot analysis, and five of those cases also co-overexpress MDM-2 protein p57. No statistically significant correlation of MDM-2 protein overexpression to clinical disease stage and history of previous chemotherapy of CLL patients has been found. However, considering the oncogenic potential of overexpressed MDM-2 proteins, a possible role of MDM-2 proteins in the promotion of CLL disease remains to be evaluated.
 ...
PMID:Expression profile of MDM-2 proteins in chronic lymphocytic leukemia and their clinical relevance. 906 96

MDM-2 is one of the target genes of the p53 tumor suppressor protein. Its best characterized function is found in the inhibition of p53's ability to modulate transcription. Deregulated expression of MDM-2 could thus at least partially substitute for p53 mutation in the process of tumorigenesis. We show here that MDM-2 is highly expressed in biopsies of normal human skin or in vitro reconstituted human skin. The protein is detected in the nucleus of keratinocytes throughout the different layers of the epidermis and in reconstituted skin as early as the two to three cell layer stage. The 90 kiloDalton (kD) protein is one of the major forms detected in Western blot experiments. MDM-2 is detected in skin reconstituted from keratinocytes in which p53 is inactivated by mutation or degradation by E6 protein, providing evidence that MDM-2 expression in the skin can occur in the absence of wild type p53. Moreover, we found no correlation between the p53 status and MDM-2 expression levels in a series of basal and squamous cell carcinomas or Bowen diseases. Our data provide first evidence for the expression of MDM-2 in a differentiated adult tissue.
 ...
PMID:MDM-2 protein is expressed in different layers of normal human skin. 907 Jun 62


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>