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)

Two human neuroblastoma (NB) cell lines, SH-SY5Y and Kelly, were found to express the gene for erythropoietin (EPO) in an oxygen (O(2))-dependent manner. However, NB cells had maximal production of EPO with lower partial pressure of O(2) values than the well-characterized hepatoma cell line HepG2. This maximal EPO expression was preceded by accumulation of the O(2)-sensitive alpha subunit of the heterodimeric transcription-factor complex hypoxia-inducible factor 1 (HIF-1). Western blot analysis revealed that the amount of the beta subunit of HIF-1, identical to aryl hydrocarbon receptor nuclear translocator 1 (ARNT1), and the homolog ARNT2 increased in nuclear extracts from SH-SY5Y cells exposed to anoxia. In neuronal cells, ARNT1 and ARNT2 can form a heterodimer with HIF-1alpha, generating a functional HIF-1 complex. Using the hypoxia response element of the human EPO enhancer, we conducted electrophoretic mobility shift assays that showed accumulation and binding of HIF-1 complexes containing both ARNT1 and ARNT2 in NB cells. In addition to the HIF-1 complex, hepatocyte nuclear factor 4alpha (HNF4alpha) was found to be indispensable for hypoxia-induced EPO gene expression in hepatoma cells. Western blot analysis and polymerase chain reaction assessment showed that NB cells express neither HNF4alpha nor the splicing variant HNF4alpha7 and thus express EPO in an HNF4alpha-independent manner. Together, SH-SY5Y and Kelly cells may provide a new in vitro model for studying the mechanism of tissue-specific, hypoxia-inducible EPO gene expression.
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PMID:Hypoxia-inducible erythropoietin gene expression in human neuroblastoma cells. 1223 77

Hypoxia-Inducible Factor-1 (HIF-1) is the key transcription factor in control of the expression of hypoxia-inducible genes needed by cells to adapt to decreased oxygen availability. Herein, we investigated the HIF-1alpha-mediated gene expression of carbonic anhydrase 9 (CA9) in response to hypoxia and changes of intracellular calcium levels in the neuroblastoma cell line SH-SY5Y. Decreasing the intracellular calcium level by BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) induced HIF-1alpha nuclear accumulation and enhanced HIF-1 DNA binding within 1 h of incubation. Like hypoxia, BAPTA stimulated HIF-1-dependent transcription by increasing the activity of the C-terminal transactivation domain of HIF-1alpha and greatly enhanced expression of the HIF-1 target gene CA9. Detailed analysis of HIF-1alpha accumulation revealed that BAPTA attenuated the interaction of HIF-1alpha with von-Hippel-Lindau protein thus decreasing proteasomal degradation of HIF-1alpha. Knock down of HIF-1alpha mRNA and protein by small interference RNA for HIF-1alpha revealed that both hypoxia and the BAPTA-induced gene expression of CA9 were strictly dependent on HIF-1alpha. In contrast, elevation of cytosolic calcium level by thapsigargin reduced the BAPTA-mediated effects. Measurements of intracellular calcium under hypoxia revealed a change in the cellular calcium distribution. BAPTA-dependent induction of HIF-1 activity was not caused by its in vitro capability to chelate iron. Instead, effective chelation of cellular calcium caused the accumulation of HIF-1alpha protein through inhibition of HIF-prolyl hydroxylases and activated HIF-1-dependent gene expression under normoxic conditions.
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PMID:Chelation of cellular calcium modulates hypoxia-inducible gene expression through activation of hypoxia-inducible factor-1alpha. 1532 93

Solid tumors are frequently necrotic and hypoxic due to poor vascularization. Tumor cells adapt to hypoxia by modulating their phenotype. Key players in this process are the hypoxia-inducible factors (HIF-1alpha to 3alpha). HIFs are also expressed during normal development; for example, HIF-2alpha is specifically expressed and appears to be involved in the development of the murine sympathetic nervous system (SNS). Here, we demonstrate that HIF-2alpha protein is selectively present in human fetal week 8.5 SNS paraganglia. Neuroblastoma is derived from SNS precursors. In a subset of neuroblastomas, a spontaneous neuronal to neuroendocrine differentiation occurs in areas adjacent to necrotic zones. As HIF-2alpha activity has been associated not only with hypoxic but also with hypoglycemic conditions, we have investigated putative effects of hypoxia, glucose depletion, and HIF-2alpha on the neuroblastoma phenotype. HIF-2alpha was detected in hypoxic and in well-oxygenized neuroblastoma cells and tissue, presumably reflecting their embryonic features. With regard to differentiation, hypoxic cells lost their neuronal/neuroendocrine features and gained marker gene expression associated with an immature, neural crest-like phenotype. Low glucose potentiated the effect of hypoxia. These findings suggest that poorly vascularized neuroblastomas become immature and maintain a more aggressive phenotype, which possibly could involve a sustained stabilization and activation of HIF-2alpha.
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PMID:HIF-2alpha expression in human fetal paraganglia and neuroblastoma: relation to sympathetic differentiation, glucose deficiency, and hypoxia. 1565 56

The extent of angiogenesis and/or vascular endothelial growth factor (VEGF) expression in neuroblastoma tumors correlates with metastases, N-myc amplification, and poor clinical outcome. Understanding the mechanisms regulating VEGF expression in neuroblastoma cells provides additional therapeutic options to control neuroblastoma tumor growth. VEGF mRNA is controlled by growth factors and hypoxia via the transcription factor hypoxia-inducible factor (HIF-1alpha). HIF-1alpha protein levels are regulated by the von Hippel Lindau tumor suppressor gene, VHL, which targets HIF-1alpha degradation. To determine whether the levels of VEGF in neuroblastomas are due to mutations in VHL, we evaluated genomic DNA from 15 neuroblastoma cell lines using PCR. We found no mutations in exons 1, 2, or 3 of the VHL gene. VEGF mRNA levels in neuroblastoma cells cultured in serum-free medium increased after 8 to 16 hours in serum, insulin-like growth factor-I (IGF-I), epidermal growth factor, or platelet-derived growth factor. Serum/IGF-I induced increases in HIF-1alpha protein that temporally paralleled increases in VEGF mRNA, whereas HIF-1beta levels were unaffected. VEGF and HIF-1alpha levels were blocked by inhibitors of phosphatidylinositol 3-kinase and mammalian target of rapamycin. Furthermore, we confirmed that HIF-1alpha mediates approximately 40% of the growth factor activity stimulating VEGF protein expression. Topotecan blocked the IGF-I-stimulated increase in HIF-1alpha but not HIF-1beta, and this resulted in a decrease in VEGF in four neuroblastoma cell lines tested. These data indicate that growth factors in an autocrine or paracrine manner play a major role in regulating VEGF levels in neuroblastoma cells and that targeted therapies to phosphatidylinositol 3-kinase, mammalian target of rapamycin, and/or HIF-1alpha have the potential to inhibit VEGF expression and limit neuroblastoma tumor growth.
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PMID:Topotecan blocks hypoxia-inducible factor-1alpha and vascular endothelial growth factor expression induced by insulin-like growth factor-I in neuroblastoma cells. 1593 Feb 97

Hypoxia is widespread in solid tumors as a consequence of poorly structured tumor-derived neovasculature. Direct measurement of low oxygen levels in a range of adult tumor types has correlated tumor hypoxia with advanced stage, poor response to chemotherapy and radiotherapy, and poor prognosis. Little is known about the importance of hypoxia in pediatric tumors; therefore, we evaluated the effects of hypoxia on the response of the neuroblastoma cell lines SH-EP1 and SH-SY5Y to the clinically relevant drugs, vincristine, etoposide, and cisplatin. Short periods of hypoxia (1% O2) of up to 16 hours had no effect on drug-induced apoptosis or clonogenic survival. Prolonged hypoxia of 1 to 7 days leads to reduction in vincristine- and etoposide-induced apoptosis in SH-SY5Y and SH-EP1 cells, and this was reflected in increased clonogenic survival under these conditions. Neither short-term nor prolonged hypoxia had any effect on the clonogenic response to cisplatin in SH-SY5Y cells. Hypoxia-inducible factor-1 (HIF-1) alpha was stabilized in these cell lines within 2 hours of hypoxia but was no longer detectable beyond 48 hours of hypoxia. Up-regulation of carbonic anhydrase IX showed HIF-1alpha to be transcriptionally active. Down-regulation of HIF-1alpha by short hairpin RNA interference and the small-molecule 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole reduced hypoxia-induced drug resistance. These results suggest that prolonged hypoxia leads to resistance to clinically relevant drugs in neuroblastoma and that therapies aimed at inhibiting HIF-1alpha function may be useful in overcoming drug resistance in this tumor.
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PMID:Chronic hypoxia promotes hypoxia-inducible factor-1alpha-dependent resistance to etoposide and vincristine in neuroblastoma cells. 1698 58

In neuroblastoma specimens, HIF-2alpha but not HIF-1alpha is strongly expressed in well-vascularized areas. In vitro, HIF-2alpha protein was stabilized at 5% O2 (resembling end capillary oxygen conditions) and, in contrast to the low HIF-1alpha activity at this oxygen level, actively transcribed genes like VEGF. Under hypoxia (1% O2), HIF-1alpha was transiently stabilized and primarily mediated acute responses, whereas HIF-2alpha protein gradually accumulated and governed prolonged hypoxic gene activation. Knockdown of HIF-2alpha reduced growth of neuroblastoma tumors in athymic mice. Furthermore, high HIF-2alpha protein levels were correlated with advanced clinical stage and high VEGF expression and predicted poor prognosis in a clinical neuroblastoma material. Our results demonstrate the relevance of HIF-2alpha in neuroblastoma progression and have general tumor biological implications.
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PMID:Recruitment of HIF-1alpha and HIF-2alpha to common target genes is differentially regulated in neuroblastoma: HIF-2alpha promotes an aggressive phenotype. 1709 63

Neurotrophins and their cognate receptors play a pivotal role in the development and function of the nervous system. High expression levels of the neurotrophin receptor TrkB and its ligands in neuroblastomas are associated with an unfavorable outcome. We report here that NTRK2, which encodes the TrkB receptor tyrosine kinase, is an oxygen-regulated gene, whose expression is stimulated by the hypoxia-inducible factor-1 (HIF-1). TrkB mRNA and protein levels were elevated nearly 30-fold in neuroblastoma-derived Kelly cells in hypoxia (1% O(2)) versus normoxia (21% O(2)). A luciferase reporter construct containing approximately 2.1 kilobases of the human TrkB promoter was activated about 6-fold both in hypoxia and after stimulation with the hypoxia mimetic 2,2'-dipyridyl (100 microm) at 21% O(2). Luciferase activity in the presence of 2,2'-dipyridyl was reduced significantly upon small interfering RNA knockdown of HIF-1alpha but not of HIF-2alpha. Accordingly, hypoxia failed to stimulate the TrkB promoter in mouse embryonic fibroblasts that lacked HIF-1alpha. The hypoxia-responsive promoter region could be mapped to three HIF-1 binding elements that were located between -923 and -879 bp relative to the transcription start site. The migration of cultured neuroblastoma cells was increased approximately 2-fold upon incubation at 1 versus 21% O(2). This effect of hypoxia was abrogated with the tyrosine kinase inhibitor K252a (200 nm). Our findings indicate that transcription of the NTRK2 gene is stimulated at low oxygen tension through a HIF-1-dependent mechanism. In conclusion, enhanced expression of TrkB could represent a critical switch for the previously reported dedifferentiation of neuroblastoma cells under hypoxic conditions.
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PMID:Hypoxia-inducible factor-1 (HIF-1) is a transcriptional activator of the TrkB neurotrophin receptor gene. 1737 10

Prolyl 4-hydroxylases (P4Hs) act on collagens (C-P4Hs) and the oxygen-dependent degradation domains (ODDDs) of hypoxia-inducible factor alpha subunits (HIF-P4Hs) leading to degradation of the latter. We report data on a human P4H possessing a transmembrane domain (P4H-TM). Its gene is also found in zebrafish but not in flies and nematodes. Its sequence more closely resembles those of the C-P4Hs than the HIF-P4Hs, but it lacks the peptide substrate-binding domain of the C-P4Hs. P4H-TM levels in cultured cells are increased by hypoxia, and P4H-TM is N-glycosylated and is located in endoplasmic reticulum membranes with its catalytic site inside the lumen, a location differing from those of the HIF-P4Hs. Despite this, P4H-TM overexpression in cultured neuroblastoma cells reduced HIF-alpha ODDD reporter construct levels, and its small interfering RNA increased HIF-1alpha protein level, in the same way as those of HIF-P4Hs. Furthermore, recombinant P4H-TM hydroxylated the two critical prolines in HIF-1alpha ODDD in vitro, with a preference for the C-terminal proline, whereas it did not hydroxylate any prolines in recombinant type I procollagen chains.
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PMID:An endoplasmic reticulum transmembrane prolyl 4-hydroxylase is induced by hypoxia and acts on hypoxia-inducible factor alpha. 1772 31

Selenium (Se) is an essential micronutrient as well as a toxic trace element in animal and human nutrition. The effects of Se in the immune system and some diseases are well documented. The objective of the present study was to examine the role of Se in reducing the hypoxia induced apoptosis in neuroblastoma cell line. Hypoxia showed an enhanced cytotoxicity, increased free radical production and apoptosis (p<0.001) which was measured in terms of DNA break down by comet assay. Hypoxia has decreased reduced Glutathione (GSH) content, Glutathione Reductase (GR), Glutathione peroxidase (GPx) and Superoxide Dismutase (SOD) activities as compared to control cells. During hypoxic condition the expression of cytochrome C, pro and active caspase-3 levels were enhanced significantly followed by nonsignificant upregulation of Bcl-2. But, the Se supplementation inhibited the cytotoxicity, free radical generation and stabilized the HIF-1alpha accumulation in cells under hypoxia. The GSH content, GR, GPx and SOD activities increased significantly in Se-treated hypoxic cells, as compared to control. Further there was an appreciable inhibition of apoptosis by upregulation of Bcl-2 proteins, in the presence of Se under hypoxia. Selenium supplementation to cells significantly inhibited the hypoxia induced DNA fragmentation and restored the antioxidant status back to control levels. This study suggests that Se supplementation prevented the cells from hypoxia induced apoptosis by triggering upregulation of Bcl-2 protein and reducing the oxidative stress.
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PMID:Selenium protects the hypoxia induced apoptosis in neuroblastoma cells through upregulation of Bcl-2. 1840 86

Erythropoietin (Epo) expression is regulated via hypoxia-inducible factor (HIF)-1alpha-directed gene transcription. Activation of the erythropoietin receptor (EpoR) by Epo leads to elevated expression of the anti-apoptotic protein, bcl-2, which has recently been shown to promote angiogenesis in malignant tumors. Expression of HIF-1alpha, Epo, EpoR, and bcl-2 was studied by immunohistochemistry in a series of 20 olfactory neuroblastoma (ONB) samples. Data were correlated with microvessel density, proliferative activity, and apoptosis in the specimens and survival analysis was performed to investigate the prognostic value of the examined factors. Immunohistochemical analysis revealed robust expression of HIF-1alpha, Epo, EpoR, and bcl-2 in ONB. Ninety percent of the samples showed HIF-1alpha immunoreactivity and in 60% of the cases, bcl-2 immunoreactivity was observed. A significant positive correlation between the expression levels of HIF-1alpha and bcl-2 and the microvessel density was found. Survival analysis did not reveal any prognostic significance for the tested factors. Expression of HIF-1alpha, Epo, Epo-R, and bcl-2 may play a functional role in ONB pathogenesis. Our data suggest that bcl-2 may act as a stimulator of angiogenesis in ONB, and thus represents a novel target for anti-angiogenic treatment strategies in the therapy of ONB.
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PMID:Expression of bcl-2 is associated with microvessel density in olfactory neuroblastoma. 1843 43


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