Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

p53 binding protein 1 (53BP1), a protein proposed to function as a transcriptional coactivator of the p53 tumor suppressor, has BRCT domains with high homology to the Saccharomyces cerevisiae Rad9p DNA damage checkpoint protein. To examine whether 53BP1 has a role in the cellular response to DNA damage, we probed its intracellular localization by immunofluorescence. In untreated primary cells and U2OS osteosarcoma cells, 53BP1 exhibited diffuse nuclear staining; whereas, within 5-15 min after exposure to ionizing radiation (IR), 53BP1 localized at discreet nuclear foci. We propose that these foci represent sites of processing of DNA double-strand breaks (DSBs), because they were induced by IR and chemicals that cause DSBs, but not by ultraviolet light; their peak number approximated the number of DSBs induced by IR and decreased over time with kinetics that parallel the rate of DNA repair; and they colocalized with IR-induced Mre11/NBS and gamma-H2AX foci, which have been previously shown to localize at sites of DSBs. Formation of 53BP1 foci after irradiation was not dependent on ataxia-telangiectasia mutated (ATM), Nijmegen breakage syndrome (NBS1), or wild-type p53. Thus, the fast kinetics of 53BP1 focus formation after irradiation and the lack of dependency on ATM and NBS1 suggest that 53BP1 functions early in the cellular response to DNA DSBs.
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PMID:p53 binding protein 1 (53BP1) is an early participant in the cellular response to DNA double-strand breaks. 1113 68

p53 mutations are rare in neuroblastomas at diagnosis perhaps accounting for their initial response to therapy, but advanced neuroblastoma frequently relapses, and it is possible that p53 mutations develop later. Two neuroblastoma cell lines derived from the same patient before [SKNBE(1n)] and after [SKNBE(2c)] cytotoxic therapy were analyzed for the presence of chromosome 17 and p53 genes by fluorescent in situ hybridization, p53 mutations by DNA sequencing, and p53 function after irradiation by studying the transcription of p53-regulated genes, cell cycle arrest, and induction of apoptosis. The SKNBE(1n) cell line was wild-type for p53, had two p53 genes, two copies of chromosome arm 17p and showed functional p53 after irradiation. The SKNBE(2c) cell line derived from the same patient 5 months later at relapse had loss of an entire chromosome 17, resulting in hemizygosity for the p53 locus on 17p and a missense p53 mutation in exon 5, and p53 was not functional after irradiation. The appearance of a p53 mutation in a cell line derived from a relapsed neuroblastoma suggests that this may be a mechanism of resistance to therapy. If p53 mutations develop frequently in relapsed neuroblastoma, cytotoxic agents more sensitive to mutant p53 might be more effective at relapse.
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PMID:Evidence for the development of p53 mutations after cytotoxic therapy in a neuroblastoma cell line. 1119 2

Neuroblastoma-derived tumor cells, unlike cells from other tumor types, characteristically express a wildtype but cytoplasmically sequestered p53 protein. To ascertain whether the p53 in these cells retained any physiological activity, we inactivated it in SK-N-SH cells, a neuroblastoma-derived cell line, by introducing the human papilloma virus type 16 E6 expression plasmid. Parent SK-N-SH cell cultures are composed of two cell types exhibiting characteristic morphologies designated neuroblastic (N-type) or substrate-adherent fibroblastic (S-type) cells, both of which have been shown to spontaneously transdifferentiate or interconvert. We report here that down-regulation of p53 resulted in conversion of SK-N-SH cells to the substrate-adherent fibroblast-like S-type cells. The morphologic conversion was accompanied by a loss of neurofilament expression, a marker for the neuronal N-type cells, an increase in the expression of vimentin, and a lack of responsiveness to retinoic acid-induced neuronal differentiation. Importantly, we did not observe N-type cells in the E6-transfected cell population, suggesting that they were incapable of transdifferentiating to the N-type morphology. We also tested the ability of these E6-transfected S-type cells to form colonies in soft agar and observed a markedly reduced capacity of these cells to do so when compared with the parent and mutant E6-transfected cells. These results suggest that p53 is required for the maintenance of the neuroblastic tumorigenic phenotype.
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PMID:Morphologic conversion of a neuroblastoma-derived cell line by E6-mediated p53 degradation. 1120 42

p73, a recently identified gene showing high homology to p53 and mapping to 1p36.33, was presented as a candidate gene for neuroblastoma. In this study the authors evaluate the levels and allelic nature of p73 expression in primary neuroblastomas using reverse transcription-polymerase chain reaction-restriction fragment length polymorphism strategies based on intragenic polymorphisms. From 32 neuroblastoma patients, 11 were heterozygous for the p73 polymorphisms analyzed. p73 expression was found to be low in the correspondent tumors and while all 6 stages 1 and 2 tumors presented biallelic expression, 4 out of the 5 stage 4 tumors showed only one active p73 allele. Analysis of blood samples from 8 healthy donors and 4 neuroblastoma patients revealed much higher levels of p73 expression, and exclusively of biallelic nature. These results are supportive of a role for p73 in the biology of neuroblastoma, particularly in some advanced tumors. Nevertheless, the G81A/C91T polymorphism, previously implicated in regulating the expression of p73, did not show any significant association with neuroblastoma development.
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PMID:P73 expression in neuroblastoma: a role in the biology of advanced tumors? 1120 39

The wild type p53 tumor suppressor protein is rapidly degraded in normal cells by MDM2, the ubiquitin ligase that serves as the key regulator of p53 function by modulating protein stability. Cellular exposure to genotoxic stress triggers the stabilization of p53 by multiple pathways that converge upon interference with MDM2 function. In this study, we first investigated the ability of HDM2 (MDM2 human homologue) to degrade endogenous p53 in neuroblastoma (NB). Although the p53 protein in NB has been reported to be constitutively stabilized, we find that HDM2 in NB is functional and facilitates the rapid turnover of p53 in nonstressed cells via the proteasome pathway. Second, we examined the relationship between p53 and HDM2 in the adriamycin-mediated stabilization of p53 in NB. We demonstrate that while p53 stabilization depends neither upon the phosphorylation of specific N-terminal sites nor upon dissociation from HDM2, it requires inactivation of functional HDM2. In support of this notion, p53 stabilization following adriamycin resulted in an inhibition of both p53 ubiquitination and HDM2 ligase activity. Taken together, these data implicate a requirement for enzymatic inactivation of HDM2 as a novel mechanism for p53 stabilization in the DNA damage response pathway.
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PMID:Requirement for HDM2 activity in the rapid degradation of p53 in neuroblastoma. 1127 10

The amplification of the N-myc gene and a gain of the chromosome 17q arm correlate with an unfavorable outcome in patients with neuroblastoma. In this study, we determined the gene dosage of the N-myc gene (located at 2p24) and Survivin gene (located at 17q25) using the p53 gene (located at 17p13) as the internal control gene by the TaqMan polymerase chain reaction (PCR)-based gene dosage analysis in 25 neuroblastoma samples. Based on the assumption that the gene dosages of each gene of a normal individual lymphocytes are 1.0, 11 of the 25 cases with a corrected gene dosage of N-myc (N-myc/p53) of more than 2.0 had a more unfavorable prognosis than the 14 cases with a N-myc gene dosage of less than 2.0 (5-year survival rate: 18 vs. 71%, P<0.01). Ten of 25 cases with a corrected Survivin gene dosage (Survivin/p53) of more than 2.0 had a more unfavorable prognosis than the 15 cases with a Survivin gene dosage of less than 2.0 (5-year survival rate: 10 vs. 67%, P<0.01). This quantitative PCR system is considered to be useful for quickly and accurately evaluating the degree of malignancy of neuroblastoma in order to select the optimal treatment.
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PMID:Quick quantitative analysis of gene dosages associated with prognosis in neuroblastoma. 1129 91

The neurotoxin 6-hydroxydopamine has been used to induce selective dopaminergic cell death in animal models of Parkinson's disease. The response of neurons to this toxin has been shown to be greatly influenced by astrocytes. Our laboratory reported previously that human neuroblastoma SH-SY5Y cells became more resistant to the toxicity of 6-hydroxydopamine when co-cultured with mouse astrocytes. This enhanced tolerance required direct and specific adhesion between SH-SY5Y cells and astrocytes. We hypothesized that this interaction led to biochemical changes in SH-SY5Y cells, thereby protecting these cells from toxicity. To study these changes, we again co-cultured SH-SY5Y cells with astrocytes and treated them with 6-hydroxydopamine. An optimized condition of trypsin treatment was employed to separate SH-SY5Y cells from astrocytes quickly. Western blot analysis demonstrated that 6-hydroxydopamine significantly increased p53 protein in monolayer SH-SY5Y cells grown in either regular medium or conditioned medium from astrocytes. This change, however, was not observed in the group co-cultured with astrocytes. Data obtained from the ribonuclease protection assay indicated that similar changes also occurred at the transcriptional level. The enhanced resistance of the co-cultured SH-SY5Y cells to the toxicity of 6-hydroxydopamine is attributed to the ability of astrocytes to prevent the increase of p53 induced by this toxin. This study demonstrates the significance of the interaction between astrocytes and neurons when they are exposed to neurotoxins.
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PMID:Inhibition of 6-hydroxydopamine-induced p53 expression and survival of neuroblastoma cells following interaction with astrocytes. 1131 93

BBR3464 is a new platinum-based drug non cross-resistant with cisplatin. To characterise the cellular basis of BBR3464 cytotoxicity as opposed to cisplatin, we performed a comparative study of the two drugs in cisplatin-resistant neuroblastoma and astrocytoma cells. In both model systems, BBR3464 proved to be more potent than cisplatin and was able to overcome cisplatin resistance. The higher potency exhibited by BBR3464 correlated with an increased cellular platinum accumulation and DNA-adduct formation. At equitoxic doses, BBR3464 induced apoptosis to a lesser extent than cisplatin and failed to overcome the decreased susceptibility to cisplatin-induced apoptosis in cisplatin-resistant cells. Cell cycle analysis showed a dose-dependent G2/M arrest by BBR3464. In astrocytoma cells, cisplatin treatment resulted in the upregulation of p53, p21 and bax, while only p21 induction was observed after BBR3464 treatment. In cisplatin-resistant cells, the reduced sensitivity to cisplatin paralleled a resistance to the induction of p53/p21 pathway by cisplatin, while the same doses of BBR3464 induced p21 to a similar extent in the resistant cells as in the parental cells. In conclusion, BBR3464 induces a cellular response that is different from cisplatin, supporting the view that the two drugs act through different mechanisms. Our data indicate that BBR3464 may be a promising agent in the treatment of tumours unresponsive to cisplatin and with a non-functional p53.
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PMID:The novel trinuclear platinum complex BBR3464 induces a cellular response different from cisplatin. 1131 83

Neuroblastoma (NB) cells reportedly accumulate wild-type p53 exclusively in the cytoplasm. However, immunofluorescence assays with five different antibodies showed that p53 accumulates in the nucleus of up to 10% of NB cells. PAb1801 detected cytoplasmic 'punctate structures' which were also found in p53-null cells, rendering this antibody unsuitable for p53 detection. A comparison of DO-1 and PAb1801 staining in NB tissue sections confirmed the results obtained with NB cells. Nuclear accumulation of p53 was induced in NB cells using substances which disturb p53's tertiary structure at its zinc finger motif, or by treatment with mitomycin C. Constitutive nuclear accumulation was observed in an SK-N-SH variant, AW-1, which has a point mutation in p53 at Cys176>Ser, disturbing the same motif. Even though p53 showed DNA-binding capability after mitomycin C treatment of NB cells, the target gene products MDM2 and p21(WAF1,CIP1,SDI1) were not synthesized and no p53 transactivating activity measured in a reporter gene assay. Therefore we suggest that p53 in NB cells might be predominantly in a conformation refractory to integration into the transcriptional complex, resulting in at least partial transcriptional inactivity, hyperactive nuclear export and resistance to degradation by exogenously expressed MDM2.
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PMID:Evidence that wild-type p53 in neuroblastoma cells is in a conformation refractory to integration into the transcriptional complex. 1131 75

p73 has recently been identified as a structural and functional homolog of the tumor suppressor protein p53. Overexpression of p53 activates transcription of p53 effector genes, causes growth inhibition and induced apoptosis. We describe here the effects of a tumor-derived truncated transcript of p73alpha (p73Deltaexon2) on p53 function and on cell death. This transcript, which lacks the acidic N-terminus corresponding to the transactivation domain of p53, was initially detected in a neuroblastoma cell line. Overexpression of p73Deltaexon2 partially protects lymphoblastoid cells against apoptosis induced by anti-Fas antibody or cisplatin. By cotransfecting p73Deltaexon2 with wild-type p53 in the p53 null line Saos 2, we found that this truncated transcript reduces the ability of wild-type p53 to promote apoptosis. This anti-apoptotic effect was also observed when p73Deltaexon2 was co-transfected with full-length p73 (p73alpha). This was further substantiated by suppression of p53 transactivation of the effector gene p21/Waf1 in p73Deltaexon2 transfected cells and by inhibition of expression of a reporter gene under the control of the p53 promoter. Thus, this truncated form of p73 can act as a dominant-negative agent towards transactivation by p53 and p73alpha, highlighting the potential implications of these findings for p53 signaling pathway. Furthermore, we demonstrate the existence of a p73Deltaexon2 transcript in a very significant proportion (46%) of breast cancer cell lines. However, a large spectrum of normal and malignant tissues need to be surveyed to determine whether this transdominant p73 variant occurs in a tumor-specific manner.
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PMID:Transactivation-deficient p73alpha (p73Deltaexon2) inhibits apoptosis and competes with p53. 1131 82


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