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)

The p53 gene was examined in primary lymphoblasts of 25 pediatric patients with acute lymphoblastic leukemia by the RNase protection assay and by single strand conformation polymorphism analysis in 23 of 25 cases. p53 mutations were found to occur, but at a low frequency (4 of 25). While all four mutations were identified by single strand conformation polymorphism, the comparative sensitivity of RNase protection was 50% (2 of 4). Heterozygosity was retained at mutated codons in 3 of 4 cases. One pedigree was consistent with the Li-Fraumeni syndrome, and bone marrow from both diagnosis and remission indicated a germline G to T transversion at codon 272 (valine to leucine). Although members of another family were affected with leukemia, a 2-bp deletion in exon 6 was nonhereditary. The other two nonhereditary p53 mutations included a T to G transversion at codon 270 (phenylalanine to cysteine) and a G to C transversion at codon 248 (arginine to proline). These data support the role of both hereditary and acquired p53 mutations in the pathogenesis and/or progression of some cases of childhood acute lymphoblastic leukemia.
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PMID:Hereditary and acquired p53 gene mutations in childhood acute lymphoblastic leukemia. 173 52

The wild-type (wt) p53 tumor suppressor gene is commonly inactivated in human malignancies, either by mutations or by loss of expression. An additional proposed mechanism for inactivation of wt-p53 is amplification of the murine double minute 2 (MDM2) gene and overexpression of the MDM2 protein, which binds to p53 and eliminates its tumor suppressor function. To investigate a potential role for MDM2 in the inactivation of wt-p53 in pediatric acute lymphoblastic leukemia (ALL), we examined the expression of MDM2 and p53, as well as the occurrence of p53 mutations and possible amplification of the MDM2 gene, in 19 pediatric ALL cell lines and one pediatric acute myelogenous leukemia (AML) line. Although we did not find significant amplification of the MDM2 gene in any of the leukemic lines, we detected overexpression of MDM2 in all 10 lines that expressed wt-p53. Of the 10 lines without overexpression of the MDM2 gene, six (including the AML line) did not express p53, and four expressed mutant p53 with single point mutations in exons 7 and 8. To determine whether primary leukemic cells showed a similar correlation, we analyzed the original cryopreserved leukemic bone marrow cells from seven patients from whom cell lines were established. We obtained similar results from both the primary leukemic cells and the corresponding cell lines: overexpression of MDM2 was present in primary cells that expressed wt-p53 but not in cells that lacked expression of wt-p53. These findings suggest an important role for MDM2 in the pathogenesis of pediatric ALL in which leukemic cells express wt-p53.
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PMID:Overexpression of the MDM2 gene by childhood acute lymphoblastic leukemia cells expressing the wild-type p53 gene. 788 79

Previous studies have indicated that p53 gene mutations were an uncommon event in acute lymphoblastic leukemia (ALL) in children. In one series of 330 patients, p53 mutations were seen in fewer than 3%. We analyzed bone marrow mononuclear cells derived from 10 children with ALL at diagnosis who subsequently failed to achieve a complete remission or who developed relapse within 6 months of attaining complete remission for p53 gene mutations and mdm-2 overexpression. We found that three children had p53 gene mutations, and four overexpressed mdm-2. Also, experiments comparing relative levels of mdm-2 RNA and protein in these patients demonstrated that mdm-2 overexpression can occur at the transcriptional and posttranscriptional level in primary leukemic cells. Although we were unable to link Waf-1 RNA expression with p53 status in childhood ALL, our data show potential p53 inactivation by multiple mechanisms in a large percentage of these patients and demonstrate that these alterations can be detected at diagnosis. Inactivation of the p53 pathway may, therefore, be important in children with ALL who fail to respond to treatment and may be useful for the early identification of children requiring alternative therapies.
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PMID:High incidence of potential p53 inactivation in poor outcome childhood acute lymphoblastic leukemia at diagnosis. 856 42

Bcl-2 and its homologue, Bcl-x1, encode membrane-associated proteins that protect neoplastic cells from DNA damage-induced apoptosis, whereas Bax is a Bcl-2 antagonist that promotes cell death. In the present study, we examined the expression and regulation of these genes at both the mRNA and protein level in 22 pediatric acute lymphoblastic leukemia (ALL) cell lines, as well as their sensitivity to apoptosis after exposure to ionizing radiation (IR). Eleven of 22 lines expressed wild-type (wt) p53, 4 expressed mutant p53, and 7 did not express p53 (p53-null). Nine of 22 (41%) lines expressed Bcl-2; of these, 8 were wt-p53+ and 1 expressed mutant p53. Bcl-2 was not expressed in any p53-null lines. In contrast, all 22 lines were positive for Bcl-x1 and Bax, although expression level varied. Treatment with IR (10 Gy) induced both downregulation of Bcl-2 and upregulation of Bax at 2 to 5 hours post-IR in 5 of 8 (63%) wt-p53+ lines, leading to apoptosis. Conversely, lines that failed to both downregulate Bcl-2 and upregulate Bax after IR were resistant to apoptosis. Although levels of Bcl-x1 expression varied among the 22 lines, high levels of Bcl-x1 were observed in 5 of 7 (71%) p53- lines. There were no obvious changes in the expression of Bcl-x1 in these lines after IR. However, among the p53-null lines, resistance to IR was observed only in those expressing high levels of Bcl-x1. These results suggest that expression of Bcl-2 but not Bcl-x1 is p53-dependent and that IR-induced downregulation of Bcl-2 and upregulation of Bax occur in most wt-p53+ lines and are associated with radiosensitivity. Furthermore, high-level expression of Bcl-x1 occurs predominantly in p53-null lines and is associated with resistance to IR-induced apoptosis in these lines, indicating differential expression and regulation of Bcl-2 and Bcl-x1 in pediatric ALL.
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PMID:Expression and regulation of Bcl-2, Bcl-xl, and Bax correlate with p53 status and sensitivity to apoptosis in childhood acute lymphoblastic leukemia. 910 19

Correlations between alterations of the p53 gene and clinical features were examined in childhood acute lymphoblastic leukemia (ALL). We analyzed 147 patients and 38 cell lines for p53 mutations within exons 5 to 9 (2 to 11 in some of them) by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis and direct sequencing. p53 gene mutations were found in 3 of 62 (5%) patients at diagnosis, 1 of 14 (7%) patients at relapse, and 13 of 20 (65%) cell lines in T-ALL, 2 of 20 (10%) patients at diagnosis, 4 of 4 (100%) patients at relapse, and 4 of 5 (80%) cell lines in t(1;19)-ALL, 1 of 23 (4%) patients at diagnosis, 2 of 22 (9%) patients at relapse, and 5 of 12 (42%) cell lines in common ALL other than t(1;19) or t(9;22)-ALL and 3 of 3 (100%) patients at diagnosis in B-ALL. In t(1;19)-ALL, p53 gene alterations were associated with a poor prognosis. The patients with p53 mutations had a trend towards poor prognosis in childhood ALL without B-ALL. p53 gene mutation is not always associated with the current prognostic factors. This alteration may become one of the important prognostic factors, if the detection of a small number of the leukemic cells with the p53 gene mutation would be possible.
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PMID:[Alterations of the p53 gene and clinical features in childhood acute lymphoblastic leukemia]. 936 61

The cyclin-dependent kinase inhibitors known as p15, p16, p18 and p19 have been suggested as candidates for tumor suppressor genes. The main genetic alterations are deletions (bi- or monoallelic) or 5' CpG island methylation of p15 and p16; very few cases or cell lines had p18 or p19 deletions or hypermethylation. Hypermethylation and homozygous deletions of tumor suppressor genes establish a new paradigm of inactivation by lack of expression, in contrast to the previously identified tumor suppressors which are predominantly inactivated by point mutations followed by loss of the wild-type allele. Here, the literature data on alterations of this gene family in more than 4700 primary cases of leukemia or lymphoma and some 320 continuous leukemia-lymphoma cell lines are summarized. Among hematopoietic malignancies, the highest frequencies of p15del and p16del were seen in acute lymphoblastic leukemia (ALL) (>30%) with striking rates in T-ALL (>50%), but also high rates in B cell precursor (BCP)-ALL (>20%); the rates of deletions in chronic lymphoid leukemia (CLL), multiple myeloma, acute and chronic myeloid leukemia (AML and CML), and myelodysplastic syndromes (MDS) were rather low, only some B cell and T cell lymphomas showed increased frequencies. Results are quite different with regard to the second mode of inactivation, hypermethylation of the promoter region. Here, p15 is most often inactivated, at particularly high frequencies in the disorders lacking any p15/p16 deletions: 40-80% p15met in AML, MDS and multiple myeloma. Also p15met rates in BCP- and T-ALL cases were high (c. 40%). There is controversy concerning the prognostic impact of p15 and p16 aberrations with some studies describing a significant correlation between inactivation of these genes and poor prognosis, while most others did not detect any prognostic relevance, at least in pediatric ALL; there may be a worse prognosis for adults with B or T cell lymphomas. Despite the small number of cases studied, paired sequential analyses suggested that disease progression is associated with loss of p15/p16 activity in a certain percentage of adult patients. p15del/p16del and p15met/p16met were also detected in the large panel of leukemia-lymphoma cell lines studied. In general, the results in cell lines reproduce the data seen in primary cells with the important difference that the rates of p15/p16 inactivation are clearly higher in the cultured cells compared with the freshly explanted cells. Retrovirus- or electroporation-mediated ectopic gene transfer of p16 wild-type into p16-deficient cell lines led to growth inhibition, arrest in G1 (without apoptosis) and occasionally to differentiation, suggesting that the malignant phenotype of p16-/- cell lines can, at least partially, be reversed by restoring p16 gene expression. A striking inverse correlation between the absence of p16 (due to deletion) and presence of wild-type retinoblastoma gene was observed in cell lines confirming a common growth suppressor pathway; no comparable relationship of p16 inactivation with p53 was detected. Paired analysis of cell lines and corresponding primary cell material showed that in all instances tested both populations carried the same gene configuration of p15 and p16. Thus, p15del or p16del did not occur during establishment of the cell lines or during prolonged culture. It is likely that p15 or p16 deletions already acquired in vivo provide a dramatic growth advantage for the immortalization process in vitro, thus increasing the success rate for cell line establishment which is commonly extremely difficult. In conclusion, the present review suggests an involvement of the p15 and p16 tumor suppressor genes in leukemo- and lymphomagenesis. Future studies will determine their exact role in the development and progression of hematopoietic neoplasms. These genes may represent interesting targets for new therapeutic strategies.
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PMID:Review of alterations of the cyclin-dependent kinase inhibitor INK4 family genes p15, p16, p18 and p19 in human leukemia-lymphoma cells. 963 10

Fas (APO-1/CD95) is a cell-surface protein that can mediate apoptosis upon specific ligand or antibody binding. The Bcl-2 protein may function as a modulator of Fas-induced apoptosis by blocking a downstream activation step, and Bcl-2 expression in acute lymphoblastic leukemia (ALL) cells appears to depend partly on expression of a wild-type (wt) p53 tumor suppressor gene (Findley et al, Blood 1997; 89: 2986). We therefore investigated the relationship between sensitivity to Fas-mediated apoptosis and (1) Fas expression, (2) p53 status, and (3) Bcl-2 protein levels in pediatric ALL cell lines and primary leukemic cells. Cell lines included 21 B cell precursor (BCP)-ALL and four T-ALL lines; in five cases, cryopreserved primary leukemic cells from which these lines were established were also examined. Additionally, we evaluated the effect of anti-Fas monoclonal antibody on the activation of protease CPP32 and induction of apoptosis in these lines. By SSCP analysis and DNA sequencing, we detected p53 mutations (mt) in eight out of 25 ALL cell lines (exon-7, codon 248 n=6; exon-8, codon 273, n=2). The expression of Fas and Bcl-2 was examined by immunofluorescence staining and quantified as the number of molecules of equivalent soluble fluorochrome (MESF). Elevated levels of Fas were expressed in all six lines with a mutation of p53 in codon 248 (1500 to 10800 MESF). Although Fas was detectable in seven of the 17 lines with wt-p53, expression was lower (150-900 MESF) compared with mt-p53+ lines. Bcl-2 was expressed in 10 of the 25 lines. Most (9/10) wt-p53+ lines expressed Bcl-2, whereas only one of eight mt-p53+ lines and no p53-null lines expressed this protein. Treatment of Fas-positive lines with anti-Fas monoclonal antibody (200 ng/ml) for 6 h induced activation of CPP32 and apoptosis in eight of 13 Fas+ lines. Sensitivity to Fas-mediated apoptosis was associated with a mt-p53 phenotype and absence of Bcl-2 expression. Six of eight Fas+/Fas-sensitive (S) lines were mt-53+/Bcl-2-, whereas only two Fas+/Fas-S lines were wt-p53+/Bcl-2+; both of these latter lines expressed low levels of Bcl-2 compared to Fas-resistant lines. In contrast, four of five Fas+/Fas-resistant (R) lines were wt-p53+/Bcl-2+; the exception was p53-null/Bcl-2- but expressed a low level of Fas (150 MESF). Activation of the cysteine protease CPP32 and cleavage of its substrate poly(ADP-ribose)polymerase (PARP) was also detected in Fas-S but not Fas-R lines. We obtained similar results from both the primary leukemic cells and the corresponding cell lines in five cases: overexpression of Fas and Fas-sensitivity were present in mt-p53+/Bcl-2- but not wt-p53+/Bcl-2+ cells. These results suggest that some pediatric ALL cells expressing mt-p53+ may be sensitive to Fas-mediated apoptosis due to high levels of Fas expression and lack of Bcl-2, and further suggest that molecular methods of activating Fas may be useful for therapy of refractory ALL with the Fas+/mt-p53+ phenotype.
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PMID:Sensitivity to Fas-mediated apoptosis in pediatric acute lymphoblastic leukemia is associated with a mutant p53 phenotype and absence of Bcl-2 expression. 982 51

Treatment of childhood acute lymphoblastic leukemia has included glucocorticosteroids for almost 50 years. Glucocorticoids are the subject of renewed interest. In one randomized trial, deferral of glucocorticosteroids from the initial month of induction therapy to the second month of therapy decreased event free survival despite preservation of remission induction rate. Dexamethasone in induction and maintenance provides a better event free survival than prednisone for standard risk patients in an isotoxic comparison even though all patients received dexamethasone in Delayed Intensification (protocol II). In a third report, patients with prior glucocorticosteroid therapy who achieved remission with subsequent multiagent therapy had a relapse rate similar to that of patients in second remission after failure of multiagent therapy. In vitro and in vivo response of leukemic cells to glucocorticosteroids is highly predictive of outcome. At relapse, loss of in vitro sensitivity to glucocorticosteroids is common and out of proportion to the loss of sensitivity to other agents. Glucocorticoid induced cell kill does not require p53 function. Investigation of leukemic cell lines finds that glucocorticosteroid resistance is most commonly linked to altered receptor number or function. Not all ligands are equivalent. Cortivazol, a pyrazolosteroid, may bind to altered receptor in some cases and induce apoptosis in dexamethasone resistant leukemic cells. Host response to exogenous glucocorticosteroid also varies. Associations between host sensitivity, disease sensitivity, and glucocorticosteroid side effects like avascular necrosis of bone remain to be investigated.
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PMID:Glucocorticosteroid therapy in childhood acute lymphoblastic leukemia. 1050 Aug 39

The role of p53 as a determinant of sensitivity of ten childhood acute lymphoblastic leukemia (ALL) cell lines to Adriamycin (ADR) was investigated. ADR-sensitive cell lines were found to have wild-type (wt) p53, whereas resistant cell lines contained point mutations in the gene. The basal level of wt p53 protein in sensitive cells was lower than that of mutant p53 in resistant cells, however, after ADR treatment a 6- to 20-fold dose-dependent increase in wt p53 was observed, whereas mutant p53 increased only twofold. The percentage of apoptotic cells in ADR-sensitive lines with wt p53 ranged from 43 to 93% following ADR treatment, whereas that in resistant lines with mutant p53 was only 8-13%. The ratio of constitutive levels of Bax/Bcl-2 was significantly higher in cells containing wt p53 than in cells with mutant p53. These results suggest that p53 gene status and the ability of p53 to induce apoptosis may be determinants of sensitivity to ADR in childhood ALL cells.
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PMID:p53 gene status and chemosensitivity of childhood acute lymphoblastic leukemia cells to adriamycin. 1057 31

MDM2 overexpression by pediatric ALL cells at initial diagnosis has been linked to poor response to therapy. In the present study, we evaluated the incidence of MDM2 overexpression by ALL cells from pediatric patients at first relapse and compared MDM2 protein levels with in vitro response to adriamycin and with duration of initial complete remission (CR1). Since an important role of MDM2 in enhancing cell proliferation and survival appears to be inhibition of p53 activity, we also evaluated the status of p53 in these patients' leukemic cells. MDM2 protein levels were determined by Western blot analysis of leukemic bone marrow cells obtained from 42 patients with B cell precursor (BCP) ALL who relapsed during or following therapy on standard POG ALL protocols. Twelve of 42 (29%) cases have MDM2 levels >/=10-fold higher than those detected in normal bone marrow mononuclear (NMMC) cells, which express relatively low levels of protein. Thirty cases (71%) expressed MDM2 at levels <10-fold those in NMMC, including 24 MDM2-negative cases (57%). P53 mutations were detected by single-strand conformation polymorphism analysis in two cases. Overexpression of MDM2 (>/=10-fold) was significantly correlated with adriamycin resistance and decreased duration of CR1. Eight of 12 (75%) overexpressers showed high levels of in vitro resistance to adriamycin, compared to four of 30 (13%) non-overexpressers (P < 0.005). The median CR1 for MDM2 overexpressers was 20.5 months (range: 3-75 months) compared to 41 months (range: 8-98 months) for non-overexpressers (P < 0.01). Four of 42 patients failed to achieve CR following re-induction: leukemic cells from three of these patients either overexpressed MDM2 or contained a mutant p53. These results indicate that overexpression of MDM2 plays a significant role in refractory pediatric ALL and is associated with early relapse, adriamycin resistance, and failure to respond to re-induction therapy. Leukemia (2000) 14, 61-67.
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PMID:Incidence and prognostic significance of MDM2 oncoprotein overexpression in relapsed childhood acute lymphoblastic leukemia. 1063 78


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