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

White blood cells from a total of 19 patients diagnosed as having acute lymphoblastic (ALL) or acute myeloid (AML) leukaemia were analysed (36 samples) for amplification and expression of the mdr1 and mdr3 genes. Nine of the patients had samples analysed at presentation and at subsequent stages of the disease (24 samples, including 4 at second relapse). Patients received standard MRC UK Trial remission-induction treatment protocols appropriate to disease and age. No amplification of either the mdr1 or mdr3 gene was found in any of the samples, and neither were mdr3 transcripts detected by dot-blot analysis using gene-specific probes. Transcripts of the mdr1 gene were found in only 2 ALL samples (of 10). However, mdr1 transcripts were detected in all AML patients and there was a significant increase in the transcript levels in these patients who went on to first and second relapse, compared with levels measured at presentation (P < 0.001). The results support the hypothesis that P-glycoprotein-mediated drug resistance may be a significant factor in tumour cell resistance to chemotherapy at relapse following initial induction-remission therapy for acute myeloid leukemia.
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PMID:Analysis of MDR1 and MDR3 multidrug resistance gene expression and amplification in consecutive samples in patients with acute leukaemias. 857 59

We have used a combination of flow cytometric assays to define multidrug resistance (MDR) positive and negative blasts in cryopreserved samples from 47 MRC trial patients with acute myeloblastic leukaemia (AML). Our primary test is a standardized assay for daunorubicin accumulation. Confirmatory assays for MDR comprised the cyclosporin modulation assay for rhodamine-123 uptake as a measure of functional P-glycoprotein and the measurement of lung resistance protein and multidrug resistance associated protein (with LRP-56 and MRPr1 respectively). 57% of samples had both low accumulation and at least one positive confirmatory test. 32% were MDR negative in all four assays. 15% of patients had primary chemo-resistant disease. Resistant disease rates were 22% for confirmed MDR-positive patients and 0% for confirmed MDR-negative patients (P=0.07). Complete remission was achieved in 74% of patients, with rates of 63% in confirmed MDR-positive patients and 93% in confirmed MDR-negative patients (P=0.06). The use of a standardized method for daunorubicin uptake, combined with the use of confirmatory tests, should reduce the uncertainty that is currently characteristic of MDR evaluation in leukaemia. In comparison with daunorubicin uptake, p-gp expression, measured using MRK-16 antibody, was more closely associated with remission rates (P =0.01). This suggests an additional role for p-glycoprotein in mediating drug resistance beyond that of a drug efflux pump.
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PMID:Use of standardized flow cytometric determinants of multidrug resistance to analyse response to remission induction chemotherapy in patients with acute myeloblastic leukaemia. 1005 Jul 13

In order to bring MDR analysis into a clinical setting, reproducible assays with clear cut off points to define MDR positivity must be used. Sensitivity can also be increased by combining the results of more than one assay. We have used a combination of flow cytometric assays to define MDR positive and negative blasts in 47 AML patients entered into MRC trials. Our primary test is a standardised and reproducible assay for anthracycline accumulation in which we use carboxylate microspheres to bind the fluorescent drug daunorubicin (dnr). Cells and beads are incubated concurrently with dnr. Cellular dnr accumulation is quantified as a cell:bead fluorescence ratio. Confirmatory assays for MDR comprise the cyclosporin modulation assay for rhodamine 123 uptake and also measurement of lung resistance protein and multidrug resistance associated protein (with LRP-56 and MRPr1 respectively). 27/47 (57%) samples had both low and accumulation and at least one positive confirmatory test (a modulated functional assay and/or protein overexpression) and were categorised as "confirmed MDR". 15/47 patients (32%) were MDR negative in all 4 assays. 5/47 (11%) patients had unconfirmed low dnr accumulation. None of the patients in this cohort had high dnr accumulation alongside overexpressed LRP or MRP or functional P-glycoprotein. We believe that this approach to MDR analysis enhances the value of the highly reproducible functional assays. The use of a primary and confirmatory tests is also likely to improve specificity.
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PMID:Reproducible flow cytometric methodology for measuring multidrug resistance in leukaemic blasts. 1050 Jul 83

The phytochemical study of Euphorbia pedroi led to the isolation of a new tetracyclic triterpenoid with an unusual spiro scaffold, spiropedroxodiol (1), along with seven known terpenoids (2-8). Aiming at obtaining compounds with improved multidrug-resistance (MDR) reversal activity, compound 8, an ent-abietane diterpene, was derivatized by introducing nitrogen-containing and aromatic moieties, yielding compounds 9-14. The structures of compounds were characterized by detailed spectroscopic analysis, including 2D NMR experiments (COSY, HMQC/HSQC, HMBC, and NOESY). Compounds 1-14 were evaluated for their MDR-reversing activity on human ABCB1 gene transfected mouse lymphoma cells (L5178Y-MDR) through a combination of functional and chemosensitivity assays. The natural compounds 1-8 were further evaluated on resistant human colon adenocarcinoma cells (Colo320), and, additionally, their cytotoxicity was assessed on noncancerous mouse (NIH/3T3) and human (MRC-5) embryonic fibroblast cell lines. While spiropedroxodiol (1) was found to be a very strong MDR reversal agent in both L5178Y-MDR and Colo320 cells, the chemical modifications of helioscopinolide E (8) at C-3 positively contributed to increase the MDR reversal activity of compounds 10, 12, and 13. Furthermore, in combination assays, compounds 1 and 7-14 enhanced synergistically the cytotoxicity of doxorubicin. Finally, by means of molecular docking, the key residues and binding modes by which compounds 1-14 may interact with a murine P-glycoprotein model were identified, allowing additional insights on the efflux modulation mechanism of these compounds.
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PMID:Terpenoids from Euphorbia pedroi as Multidrug-Resistance Reversers. 3019 57