Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Drug resistance remains a formidable obstacle to the successful treatment of pediatric primitive neuroectodermal tumors. Resistance to chemotherapeutic agents may be related, in part, to expression of the multidrug resistance gene 1 (MDR1). The protein product of this gene, P-glycoprotein, confers resistance to multiple unrelated antineoplastic drugs. The cell line DAOY, derived from a primitive neuroectodermal tumor, was used as an in vitro model to examine the development of drug resistance. Cell lines resistant to actinomycin D were developed by the growth of DAOY in increasing concentrations of the drug. The IC50 (concentration of drug needed to induce a 50% reduction in cell growth) of the resultant lines to actinomycin D was more than 10 times that of the parental line. The resistant lines were cross-resistant to VP-16 (etoposide), despite lack of previous exposure to this drug. The resistance to actinomycin D was attenuated in the presence of verapamil, a known inhibitor of P-glycoprotein. The MDR1 gene was not expressed by the parental DAOY line at the messenger ribonucleic acid (RNA) and protein level. Expression of the MDR1 gene was documented in the resistant lines by RNA blot and immunoblot techniques. These results suggest that exposure to chemotherapeutic drugs can induce classical multidrug resistance in primitive neuroectodermal tumors.
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PMID:Development of multidrug resistance in a primitive neuroectodermal tumor cell line. 134 31

Pediatric primitive neuroectodermal tumor (PNET) is a malignancy of the central nervous system currently treated with surgery, radiation therapy, and chemotherapy. Despite aggressive management, tumors recur in almost one-half of all patients. Drug resistance of tumor cells may, in part, explain the poor outcome. Resistance to chemotherapeutic agents may be related to expression of the multidrug resistance gene (MDR1) and its protein product, P-glycoprotein. The role of MDR1 in 16 instances of PNET was investigated using Western blot analysis to detect the expression of P-glycoprotein, messenger ribonucleic acid (mRNA), polymerase chain reaction to detect MDR1 mRNA expression, and Southern blot analysis to assess gene amplification. Analysis of proteins extracted from 15 tumors revealed that two of the 15 patients expressed detectable levels of P-glycoprotein. Polymerase chain reaction of ribonucleic acid from 12 PNET's revealed that six of the 12 patients (four of 10 de novo tumors and both recurrent tumors) expressed MDR1 mRNA. Southern blot analysis of deoxyribonucleic acid from 16 PNET's revealed no evidence of MDR1 amplification in any tumor. This is the first report of MDR1 expression in pediatric brain tumors. These data suggest a possible role for MDR1 in de novo and acquired drug resistance in PNET's.
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PMID:Multidrug resistance gene expression in pediatric primitive neuroectodermal tumors of the central nervous system. 134 32

The authors evaluated P-glycoprotein expression in a total of 35 cases of Ewing's sarcoma and peripheral primitive neuroectodermal tumors (PNET). Fifteen cases had matched tumors before and after treatment. The 20 unmatched tumors included 14 pretreatment PNETs and Ewing's sarcomas and 6 posttreatment Ewing's sarcomas. Two antibodies, C219 and JSB-1, were used. Immunoreactivity was almost exclusively membranous. Variability in the number of positive cells and in staining intensity was noted within individual tumors. Among the 15 matched tumors, 7 were positive for P-glycoprotein before treatment; 6 of these remained positive after treatment. Four of the 8 that were negative for P-glycoprotein before treatment became positive after treatment. Of the unmatched tumors, 9 of 14 pretreatment and 3 of 6 posttreatment tumors were positive. When relapse-free survival time, based on the presence or absence of P-glycoprotein positivity in pretreatment tumor samples, was evaluated in this group, no significant difference was found (P2 = .92); however, the numbers are too small to draw definitive conclusions. The high incidence of positive primary tumors suggests that P-glycoprotein expression is probably intrinsic in Ewing's sarcoma and PNET and not necessarily induced by therapy.
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PMID:Immunohistochemical detection of P-glycoprotein in Ewing's sarcoma and peripheral primitive neuroectodermal tumors before and after chemotherapy. 791 75