UMLS:C0027819 - FACTA Search

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Query: UMLS:C0027819 (neuroblastoma)
27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In tumor specimens such as those from neuroblastoma, ovarian, and lung carcinoma patients, the prevalence of extrachromosomal circular DNA molecules harboring amplified genes has been well established. In some cases, the amplified genes have been identified as oncogenes, and their increased expression appears to contribute to the maintenance and progression of the malignancy. The aim of this study was to investigate the effect of fractionated radiation treatment, given in daily doses similar to those administered clinically, on the stability of extrachromosomal circular DNA molecules in cancer cells. Our studies were conducted with multidrug-resistant KB cells, which harbor extrachromosomal copies of the multidrug resistance gene (MDR1) almost exclusively on circular DNA molecules of approximately 750 and 1500 kb pairs. This size range is representative of extrachromosomal circular DNA molecules that have been shown to harbor amplified oncogenes in vivo. Exponentially growing MDR KB cells were exposed to 1400 and 2800 cGy ionizing radiation administered in 7 and 14 fractions, respectively, at 200 cGy per fraction/day. A statistically significant decrease in MDR1 extrachromosomal gene copy number was reproducibly detected in the irradiated cells compared with unirradiated cells passaged for the duration of the experiment in the absence of radiation treatment. This decrease was accompanied by a reduction in multidrug resistance and in P-glycoprotein levels, as determined by clonogenic dose-response assays and Western analyses, respectively. P-glycoprotein is a multidrug transporter encoded by the MDR1 gene. Fluorescence in situ hybridization studies further determined that extrachromosomal circular DNA loss correlated to the entrapment of these DNA molecules in radiation-induced micronuclei. These results indicate that radiation-induced loss of extrachromosomally amplified genes from tumor cells via their entrapment in micronuclei contributes to the improved therapeutic response observed for some cancers.
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PMID:Fractionated ionizing radiation accelerates loss of amplified MDR1 genes harbored by extrachromosomal DNA in tumor cells. 973 94

Overexpression of the trans-membrane drug efflux pump P-glycoprotein is one of the major mechanisms by which cancer cells develop multidrug resistance. We demonstrated previously that noncytotoxic doses of various genotoxic chemicals, particularly DNA cross-linking agents, preferentially altered expression of inducible genes. These effects occurred principally at the transcriptional level and were closely correlated temporally with DNA damage. Because the mdr1 gene coding for P-glycoprotein has been reported to be highly inducible, we were interested in the effects of genotoxic cancer chemotherapy agents on its expression. We report that the DNA cross-linking agent mitomycin C significantly suppressed mRNA and protein expression of P-glycoprotein and decreased the rate of drug efflux. Mitomycin C pretreatment also significantly increased the sensitivity of cancer cells to subsequent killing by the P-glycoprotein substrate doxorubicin, decreasing the ED50 by 5- to 10-fold. Suppression of P-glycoprotein expression was also observed with subtoxic doses of the DNA cross-linking agents cisplatin, BMS181174, and chromium(VI). These effects occurred in both human and rodent cell lines; in cell lines derived from colon, breast, leukemia, neuroblastoma, and hepatoma tumors; and under both monolayer and "spheroid" culture conditions. These results suggest the basis for novel clinical cancer chemotherapy regimens aimed at drug-resistant tumors, in which a sub-chemotherapeutic dose of a DNA cross-linking agent is used to modulate the multidrug resistance phenotype prior to treatment with a second cytotoxic agent.
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PMID:Suppression of P-glycoprotein expression and multidrug resistance by DNA cross-linking agents. 981 17

P-glycoprotein (P-gp) has a role in multidrug resistance (MDR) encountered in human cancers. In this study, we used the colchicine-resistant cell line BE(2)-C/CHCb(0.2), a strain of neuroblastoma cell line BE(2)-C, as a model to measure variations of P-gp expression in cells grown in vitro and in vivo. Cells were cultured in the medium supplemented with colchicine. At the beginning of the study the drug was withdrawn and, after 22 days, added back to the culture medium. Cells were harvested at various time points and xenografted in nude mice. P-gp content in cells was measured by self-competitive binding assay and in tumors, by quantitative autoradiography (QAR). Both assays were carried out using 125I-labeled monoclonal antibody MRK16, reactive with P-gp. Concentration of P-gp in cells varied from a maximum of 1,361 pmol/g in the presence of colchicine to a minimum of 374 pmol/g in the absence of colchicine in the culture medium. P-gp concentration in the tumors ranged from 929 to 188 pmol/g, which correlated with P-gp content in the cells at the time of their injection in the mice. QAR is an accurate and reliable method to quantify P-gp expression in tumors. Changes in colchicine concentration in the ambient medium of BE(2)-C/CHCb(0.2) cells growing in vitro resulted in a change in phenotype of P-gp expression, which was stable under conditions of in vivo growth over approximately 9 cell divisions in nude mice xenografts. Therefore, P-gp content in xenografts depends only on the level of resistance of the cells at the time of their injection in the mice.
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PMID:Measurement of P-glycoprotein expression in human neuroblastoma xenografts using in vitro quantitative autoradiography. 1009 99

Imaging with technetium-99m sestamibi offers a non-invasive approach to detect the presence of functional P-glycoprotein (Pgp), one of the major causes of multidrug resistance, in human malignancies. A clinical role for Pgp has been suggested in the subpopulation of primary neuroblastoma without amplification of the proto-oncogene MYCN. We wanted to evaluate the usefulness of 99mTc-sestamibi scintigraphy in the screening of neural crest tumours for the presence of Pgp. In ten children suffering from MYCN-negative neuroblastoma, ganglioneuroblastoma or ganglioneuroma, 99mTc-sestamibi imaging was performed at initial diagnosis. All patients underwent planar imaging 20-30 min and 3.5-4 h after intravenous injection of 740 MBq/1.73 m2 99mTc-sestamibi. Tumour to normal tissue ratios, as well as washout rates, were determined and compared with in vitro flow cytometric analysis of Pgp expression and function. Pgp expression was analysed flow cytometrically with the monoclonal antibodies 4E3 and MRK16, and Pgp function was evaluated by means of rhodamine 123 uptake and efflux either in the absence or in the presence of the Pgp inhibitor verapamil. In nine of ten patients, we found that the intratumoral 99mTc-sestamibi activity was comparable to the background activity, which might be suggestive of Pgp presence. This was confirmed flow cytometrically in all but one patient. 99mTc-sestamibi enhancement was seen in the primary tumour and the bone marrow metastases of one of the ten patients, and this result was concordant with a negative Pgp status. The findings presented suggest that 99mTc-sestamibi imaging results might correlate with the presence of functional Pgp in neural crest tumours without MYCN amplification.
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PMID:Technetium-99m sestamibi imaging in paediatric neuroblastoma and ganglioneuroma and its relation to P-glycoprotein. 1019 46

S-Adenosylmethionine (AdoMet) synthetase (EC 2.5.1.6), which catalyzes the synthesis of AdoMet from methionine and ATP, is the major methyl donor for transmethylation reactions and propylamino donor for the biosynthesis of polyamines in biological systems. We have reported previously that wild-type C-1300 murine neuroblastoma (wMNB) cells, made resistant to the nucleoside analogue (Z)-5'-fluoro-4',5'-didehydro-5'-deoxyadenosine (MDL 28,842), an irreversible inhibitor of S-adenosylhomocysteine (AdoHcy) hydrolase (EC 3.3.1.1), express increased AdoMet synthetase activity (M. R. Hamre et al., Oncol. Res., 7: 487-492, 1995). In the present study, immunoblot analyses of AdoMet Synthetase with isoform-specific (MATII) antibodies demonstrated an elevation in the AdoMet synthetase immunoprotein in nucleoside analogue-resistant MNB cells (rMNB-MDL) when compared to wild-type, nonresistant MNB cells. An increase of 2.1-fold was observed in the alpha2/alpha2' catalytic subunit, which differed significantly from the much smaller increment in the noncatalytic beta-subunit of AdoMet synthetase. Densitometric analyses revealed that an increased expression of AdoMet synthetase in rMNB-MDL cells was due to overexpression of the alpha2 (Mr 53,000; 2.6-fold) and alpha2' (Mr 51,000; 1.8-fold) subunits. AdoMet synthetase mRNA expression in rMNB-MDL cells was remarkably greater than wMNB cells, as determined by quantitative competitive reverse transcription-PCR (QC-PCR) analysis. DNA (cytosine) methyl transferase expression, measured by reverse transcription-PCR analysis, was also elevated significantly in rMNB-MDL cells. In contrast, Western blot analyses demonstrated down-regulation (1.6-fold) of AdoMet synthetase in doxorubicin-resistant human leukemia cells (HL-60-R) expressing multidrug resistance protein when compared with wild-type, nonresistant HL-60 cells. The resistance of rMNB-MDL cells to nucleoside analogue inhibitors of S-adenosylhomocysteine hydrolase correlates directly with overexpression of the alpha2/alpha2' subunits of AdoMet synthetase. Cellular adaptation allows sufficient AdoMet to be synthesized, so that viability of the MNB cells can be maintained even in the presence of high AdoHcy concentrations. This novel mechanism of drug resistance does not appear to require multidrug resistance protein (P-glycoprotein) overexpression.
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PMID:S-adenosylmethionine synthetase is overexpressed in murine neuroblastoma cells resistant to nucleoside analogue inhibitors of S-adenosylhomocysteine hydrolase: a novel mechanism of drug resistance. 1021 91

Clinical studies have suggested that both MDR1 and MRP may play a significant role in the chemosensitivity and outcome of neuroblastoma. To clarify the nature of multidrug resistance (MDR) in this tumour a series of six neuroblastoma cell lines have been characterized with regard to P-glycoprotein, MRP and LRP expression using immunocytochemistry and expression of MDR1, MRP, LRP and topoisomerase II genes using reverse transcription polymerase chain reaction (RT-PCR). By RT-PCR, all lines expressed MRP, five expressed LRP and four expressed MDR1, but protein levels of each of these were variable. Chemosensitization to a range of MDR-associated drugs (vincristine, doxorubicin, etoposide, taxotere, topotecan) and non-MDR-associated drugs (cisplatin, melphalan) by three modulating agents, cyclosporin A, PSC 833 and the novel Biricodar (VX-710; Incel), was evaluated using a colourimetric cytotoxicity assay (MTS). Alteration of daunorubicin efflux by these agents was evaluated using FACS analysis. Clonogenic assay was used to study the influence of these chemosensitizers on vincristine cytotoxicity. Marked sensitization to vincristine was observed in MDR1-positive lines, and a similar but less consistent effect was seen with taxotere, doxorubicin and etoposide. With MRP-positive, MDR-negative lines, only VX-710 caused consistent sensitization. These data confirm MDR1 and MRP expression as contributory factors in chemoresistance in neuroblastoma and indicate that VX-710 may be a useful modulator of both mechanisms and worthy of clinical evaluation in this tumour.
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PMID:BIRICODAR (VX-710; Incel): an effective chemosensitizer in neuroblastoma. 1037 71

In a series of 40 neuroblastomas we analyzed the relative mRNA levels of the MDR associated genes encoding MDR1/P-glycoprotein (MDR1), multidrug resistance associated protein (MRP), lung cancer resistance related protein (LRP) and topoisomerase IIalpha (TOPO IIalpha) by cDNA-PCR. Cyclin A (CYCA) was included to examine cellular proliferation activity. MYCN gene expression was analyzed as it was recently shown to be associated with enhanced MRP gene expression in neuroblastomas. We found that tumors with MYCN gene amplification exhibit significantly increased MYCN and MRP gene expression levels. Tumors with an allelic loss of the chromosomal 1p region showed significant (P<0.05) lower MDR1 gene expression (MDR1: 50+/-29, n=4) than tumors without (MDR1: 117+/-81, P<0.05, n=36). Moreover, significant positive correlations were found for MYCN/TOPO IIalpha (P<0.0001), MYCN/CYCA (P<0.05), TOPO IIalpha/CYCA (P<0.01), MRP/CYCA (P<0.0001) and MRP/LRP (P<0.05). Our results give evidence that MDR in neuroblastomas might be caused by multiple resistance factors and that a higher proliferation rate of neuroblastoma cells possibly based on altered MYCN gene expression is associated with enhanced MRP, CYCA and TOPO IIalpha gene expression.
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PMID:Expression analysis of multidrug resistance associated genes in neuroblastomas. 1042 16

Bovine seminal ribonuclease (BS-RNase) is a homologue of RNase A with specific antitumor activity. The cytotoxic action of this agent was examined in human neuroblastoma (NB) cell lines (SK-N-SH and UKF-NB-4) possessing the multidrug resistance (MDR) phenotype and NB cell lines (IMR-32, UKF-NB-1, UKF-NB-2 and UKF-NB-3) without MDR. Although MDR cells expressed large amounts of mdr-1 mRNA, contained functional P-glycoprotein and had 20- to 105-fold lower sensitivities to doxorubicin and vincristine than cells with non-MDR phenotypes, BS-RNase was equally toxic to all NB cells at concentrations employed (0.2 to 100 microg/ml). BS-RNase showed high selectivity for NB cells and was non-toxic to normal fibroblasts and epithelial cells. Ultrastructural investigation and annexin V assay showed that BS-RNase is a powerful inductor of apoptosis. The antitumoral effects of BS-RNase were also demonstrated in vivo using established subcutaneous xenografts in athymic (nude) mice of the MDR-1-bearing UKF-NB-4 cell line. Intratumoral injections (12.5 mg/kg) of BS-RNase over four weeks resulted in complete tumor regression and absence of tumor regrowth over a two-week observation period after cessation of treatment. The results show that BS-RNase selectively kills NB cells by inducing apoptosis and that this agent is active against mdr-1 expressing cells both in vitro and in vivo. BS-RNase fulfills important criteria for a candidate antitumor agent in NB patients with advanced disease.
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PMID:Bovine seminal ribonuclease selectively kills human multidrug-resistant neuroblastoma cells via induction of apoptosis. 1053 85

In this study, we investigated prospectively the diagnostic role of 99Tcm-MIBI for staging and for predicting the therapeutic response of stage IV neuroblastoma compared with 131I-MIBG imaging and 99Tcm-MDP bone scintigraphy. Nine patients (4 girls and 5 boys aged 1-7 years) with suspected or proven stage IV neuroblastoma were studied with 99Tcm-MIBI at initial diagnosis and after 12-18 months of multidrug therapy. After the injection of 80 MBq.kg-1 99Tcm-MIBI, early (10 min) and delayed (1 h) images were obtained. The data were correlated with 131I-MIBG scans, bone scintigraphy, ultrasound, computed tomography and/or magnetic resonance imaging, and bone marrow biopsy. Eight of nine primary tumours and 41 metastatic lesions were detected by 131I-MIBG scintigraphy. None of the primary lesions demonstrated significant 99Tcm-MIBI accumulation. Sestamibi was positive in 16 of 41 MIBG-avid metastatic lesions. After six courses of multidrug chemotherapy, 30 131I-MIBI-avid neuroblastoma metastases that were 99Tcm-MIBI-negative at the time of diagnosis still did not show significant sestamibi accumulation. Follow-up demonstrated that all lesions that were 99Tcm-MIBI-avid at the time of diagnosis remained negative. Of these 16 lesions, seven were positive for 131I-MIBG accumulation with no reduction in size, and nine showed resolution after therapy. New metastatic foci detected by MIBG scintigraphy did not accumulate 99Tcm-MIBI. Clinical evaluation of patients with no 99Tcm-MIBI uptake in primary and secondary sites of neuroblastoma confirmed that they were resistant to multidrug chemotherapy. All 99Tcm-MIBI-positive lesions, irrespective of clinical outcome, demonstrated significant clearance of tracer on the delayed images. We conclude that 99Tcm-MIBI has no role in the staging of neuroblastoma. Sestamibi is a well-documented transport substrate for P-glycoprotein-related multidrug resistance and serial imaging may provide prognostic information on the therapeutic value of chemotherapy.
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PMID:The role of 99Tcm-sestamibi scintigraphy in the staging and prediction of the therapeutic response of stage IV neuroblastoma: comparison with 131I-MIBG and 99Tcm-MDP scintigraphy. 1057 8

Rifampicin, an antibiotic widely used in tuberculosis therapy, is known to exert psychotropic side effects in some patients. Recently, rifampicin has been reported to activate the glucocorticoid receptor (GR) in human hepatocytes. Because there is evidence that increased levels of glucocorticoids may induce cognitive impairment, sometimes culminating in depression, the side effects of rifampicin may result from GR activation in central nerve cells. Therefore, we used reporter gene assays to determine whether rifampicin displays glucocorticoid-like effects in human neuroblastoma SK-N-MC cells or mouse hippocampal HT22 cells. Rifampicin was unable to elicit any detectable transactivation of GR in both cell types, whereas cortisol or dexamethasone led to a potent transcriptional response. Rifampicin was also inactive in the same HepG2 cell line that was originally used to demonstrate the effect of rifampicin on GR. Moreover, rifampicin was unable to compete with dexamethasone for binding to GR. Finally, by blocking the multidrug resistance P-glycoprotein transporter (a xenobiotic extrusion pump) with verapamil or cyclosporin A, we excluded the possibility that the lack of effect by rifampicin was due to its export from the cell. Our results establish that rifampicin does not activate GR, and rule out the hypothesis that the psychotropic side effects of rifampicin treatment are a consequence of GR activation.
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PMID:Rifampicin is not an activator of glucocorticoid receptor. 1072 19

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