Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0026764 (multiple myeloma)
 36,148 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The occurrence of multidrug resistance (MDR) is one of the main obstacles in the successful chemotherapeutic treatment of cancer. MDR cell lines are resistant to the so-called naturally occurring anti-cancer drugs, such as anthracyclines, Vinca alkaloids and epipodophyllotoxins, but are not cross-resistant to alkylating agents, antimetabolites and cisplatin. So far, three separate forms of MDR have been characterized in more detail: classical MDR, non-Pgp MDR and atypical MDR. Although all three MDR phenotypes have much in common with respect to cross-resistance patterns, the underlying mechanisms certainly differ. Atypical MDR is associated with quantitative and qualitative alterations in topoisomerase II alpha, a nuclear enzyme that actively participates in the lethal action of cytotoxic drugs. Atypical MDR cells do not overexpress P-glycoprotein, and are unaltered in their ability to accumulate drugs. In this review we will focus on classical and non-Pgp MDR. The molecular mechanism of classical and non-Pgp MDR is transcriptional activation of membrane-bound transport proteins. These transport proteins belong to the ATP-binding cassette (ABC) superfamily of transport systems. The classical MDR phenotype is characterized by a reduced ability to accumulate drugs, due to activity of an energy-dependent uni-directional, membrane-bound, drug-efflux pump with broad substrate specificity. The classical MDR drug pump is composed of a transmembrane glycoprotein (P-glyco-protein-Pgp) with a molecular weight of 170 kD, and is, in man, encoded by the so-called multidrug resistance (MDR1) gene. Typically, non-Pgp MDR has no P-gly-coprotein expression, yet has about the same cross-resistance pattern as classical MDR. This non-Pgp MDR phenotype is caused by overexpression of the multidrug resistance-associated protein (MRP) gene, which encodes a 190 kD membrane-bound glycoprotein (MRP). MRP probably works by direct extrusion of cytotoxic drugs from the cell and/or by mediating sequestration of the drugs into intracellular compartments, both leading to a reduction in effective intracellular drug concentrations. For the classical MDR phenotype, evidence is accumulating that it plays a role indeed, in clinical drug resistance, especially in some hematological malignancies (acute myeloid leukemia, multiple myeloma and non-Hodgkin's lymphoma) and solid tumors (soft tissue sarcomas and neuroblastoma). The association of MRP with clinical drug resistance has not been elaborated, yet, and studies on MRP expression in human cancer have just begun. We found that overexpression of MRP, as determined by RNase protection assay as well as by immunohistochemistry, occurs in several human cancers, among which are cancer of the lung, esophagus, breast and ovary, and leukemias. Further studies are indicated to establish whether elevated MRP expression at diagnosis is an unfavorable prognostic factor for clinical outcome of chemotherapy.
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PMID:Molecular mechanisms of multidrug resistance in cancer chemotherapy. 888 Aug 78

A new human myeloma cell line, 8226/MDR10V, was selected from a P-glycoprotein-positive cell line, 8226/Dox40, in the continuous presence of doxorubicin and verapamil. MDR10V cells are 13-fold more resistant to doxorubicin and 4-fold more resistant to vincristine than the parent cell line, Dox40. Chemosensitizers are also less effective in reversing resistance in the MDR10V compared to the Dox40 cells. Despite higher resistance to cytotoxic agents, MDR10V expresses 40% less P-glycoprotein in the plasma membrane compared to Dox40; however, total cellular P-glycoprotein is the same in both cell lines. Confocal immunofluorescence microscopy shows 2.5-fold more P-glycoprotein in the cytoplasm of MDR10V cells as compared to Dox40 cells. The cytoplasmic location of P-glycoprotein in the MDR10V cells is associated with a redistribution of doxorubicin. In Dox40 cells, doxorubicin is concentrated in the nucleus, whereas in MDR10V cells, 90% of doxorubicin is found in the cytoplasm. In the presence of equivalent intracellular doxorubicin, there was a decrease in DNA-protein crosslinks in the MDR10V cell line compared to the Dox40 cell line. This finding is in agreement with the intracellular doxorubicin fluorescence studies showing less doxorubicin in the nuclei of MDR10V cells compared to Dox40 cells. Verapamil is less effective in increasing doxorubicin accumulation in the nuclei of MDR10V cells compared to Dox40 cells. Processing of P-glycoprotein from the endoplasmic reticulum to the medial Golgi was identical between the two cell lines as determined by endoglycosidase H sensitivity of newly sensitized P-glycoprotein. No mutations were found in MDR1 cDNA from MDR10V cells compared to Dox40 cells. These results suggest that resistance to chemosensitizing agents plus cytotoxic drugs is associated with a redistribution of P-glycoprotein from the plasma membrane to the cytoplasm, which in turn reduces the amount of cytotoxic drug reaching the nucleus.
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PMID:Evidence for cytoplasmic P-glycoprotein location associated with increased multidrug resistance and resistance to chemosensitizers. 896 98

VX-710 or (S)-N[2-Oxo-2-(3,4,5-trimethoxyphenyl)acetyl]-piperidine-2-carboxylic acid 1,7-bis(3-pyridyl)-4-heptyl ester, a novel non-macrocyclic ligand of the FK506-binding protein FKBP12, was evaluated for its ability to reverse P-glycoprotein-mediated multidrug resistance in vitro. VX-710 at 0.5-5 microM restored sensitivity of a variety of multidrug resistant cells to the cytotoxic action of doxorubicin, vincristine, etoposide or paclitaxel, including drug-selected human myeloma and epithelial carcinoma cells, and human MDR1 cDNA-transfected mouse leukemia and fibroblast cells. Uptake experiments showed that VX-710 at 0.5-2.5 microM fully restored intracellular accumulation of [14C]doxorubicin in multidrug resistant cells, suggesting that VX-710 inhibits the drug efflux activity of P-glycoprotein. VX-710 effectively inhibited photoaffinity labeling of P-glycoprotein by [3H]azidopine or [125I]iodoaryl azidoprazosin with EC50 values of 0.75 and 0.55 microM. Moreover, P-glycoprotein was specifically labeled by a tritiated photoaffinity analog of VX-710 and unlabeled VX-710 inhibited analog binding with an EC50 of 0.75 microM. VX-710 also stimulated the vanadate-inhibitable P-glycoprotein ATPase activity 2- to 3-fold in a concentration-dependent manner with an apparent k(a) of 0.1 microM. These data indicate that a direct, high-affinity interaction of VX-710 with P-glycoprotein prevents efflux of cytotoxic drugs by the MDR1 gene product in multidrug resistant tumor cells.
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PMID:Cellular and biochemical characterization of VX-710 as a chemosensitizer: reversal of P-glycoprotein-mediated multidrug resistance in vitro. 907 9

The purpose of the present study was to evaluate whether intermittent exposure to a constant dose of doxorubicin selects for multidrug resistance (MDR) in RPMI 8226 human myeloma cells and, if so, to determine the molecular mechanism. In an attempt to approximate clinical doxorubicin treatment in vitro, cells were exposed to a fixed dose of doxorubicin for 4 d alternating with growth in drug-free medium for 17 d. An MDR subline emerged, termed 8226/DOXint5, which was 3-4-fold resistant to doxorubicin, etoposide and m-AMSA, and 1.6-fold resistant to vincristine. Sensitivity to docetaxel, melphalan and cisplatin was normal. Verapamil normalized vincristine sensitivity but had little effect on resistance to the other agents. Cellular uptake and retention of daunorubicin and vincristine were reduced by approximately 10%. The 8226/DOXint5 cells showed diminished DNA topoisomerase IIalpha expression and increased expression of the multidrug resistance protein MRP. Expression of MDR1/P-glycoprotein was not detected. Immunostaining showed 70% of the cells to over-express the lung-resistance protein LRP. This new MDR myeloma cell line may prove to be a useful model for the development of strategies to overcome low-level, multifactorial MDR, which might be a common phenomenon in clinical myeloma treated with doxorubicin.
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PMID:Intermittent exposure to doxorubicin in vitro selects for multifactorial non-P-glycoprotein-associated multidrug resistance in RPMI 8226 human myeloma cells. 913 43

Multiple myeloma is a disease which is generally considered responsive to chemotherapy; however, essentially all patients who respond to drug treatment will relapse and die of drug-resistant disease. This disease is therefore considered a paradigm for studying the development of acquired drug resistance in the clinic. Natural product agents are frequently used in the treatment of myeloma, especially vincristine and doxorubicin. Studies using human myeloma cell lines have shown that the MDR1 gene product, P-glycoprotein (Pgp), is responsible for conferring drug resistance to natural products and glucocorticoids. We have developed assays to measure the expression of MDR1/Pgp in human myeloma specimens. These assays include immunocytochemistry, flow cytometry, and RT/PCR. Human myeloma cell lines, 8226/Dox, that are resistant to natural product agents and overexpress MDR1/Pgp are important for standardizing results and offer a means of comparing inter- and intra-patient results. Assays which measure both the presence and function of Pgp are necessary to determine the role of Pgp in clinical drug resistance in patients with myeloma.
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PMID:Detection of multidrug resistance gene expression in multiple myeloma. 920 7

Approximately 15-30% of acute myeloid leukaemia (AML) patients are primarily resistant to chemotherapy, and 60-80% of patients who achieve complete remission will inevitably relapse and succumb to their disease. The multidrug resistant (MDR) phenotype has been suspected as a major mechanism of therapy failure in AML; it is one of the best understood mechanisms of resistance to anticancer drugs. The classical MDR phenotype is characterized by the reduced ability of cells to accumulate drugs as compared to normal cells. The increased drug efflux is due to the activity of a 170 kDa glycoprotein, the P-glycoprotein (Pgp), a unidirectional drug-efflux pump which is encoded by the MDR1 gene. While studies of myeloid leukaemia and myeloma have provided the best evidence for the potential association between Pgp expression and clinical outcome, the lack of standardized methods for MDR detection and perhaps even more importantly, inconsistencies in the interpretation of MDR expression data account for divergent results in the literature. The clinicians' strong interest in MDR stems from the availability of agents capable of interfering with MDR, at least in vitro. If these laboratory results were reproducible in vivo, reversal of MDR would offer a rare opportunity to incorporate laboratory experience into the clinical management of patients.
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PMID:Classical multidrug resistance in acute myeloid leukaemia. 923 13

Decreased topoisomerase II (Topo II) activity results in resistance to antineoplastic agents targeting this enzyme. Dox1V derived from human multiple myeloma RPMI 8226 demonstrated a 4-fold resistance to doxorubicin in the absence of MDR1 overexpression or topo II mutations (Futscher B.W., Foley N., Gleason-Guzman M., Meltzer P.S., Sullivan D.M., and Dalton W.S., Int'l. J. Cancer, 66: 520-5, 1996.). Consistent with its drug resistant phenotype, a 2- to 3-fold decrease in topo II expression was identified. To investigate the molecular basis for decreased topo II expression in Dox1V, a semi-quantitative analysis of Topo II activity, protein level and mRNA transcript were performed. The results demonstrated that reduced Topo II activity is due to a decreased mRNA level. Southern blot and sequencing experiments revealed wild-type sequence of the topo II promoter in the drug resistant cells. Transient gene expression assays demonstrated that topo II is transcriptionally down-regulated in Dox1V independent of the promoter sequence of the endogenous alleles. Instead, the activity of a ubiquitous transcription factor CP-1 (NF-Y) interacting with the topo II promoter is decreased. The decrease in CP-1/NF-Y activity in Dox1V is correlated well with the decrease in topo II transcriptional activity, transcript level, Topo II protein and enzyme activity. Therefore, transcriptional down-regulation resulted from a reduced CP-1/NF-Y activity is responsible for decreased topo II expression in Dox1V cells.
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PMID:Decreased CP-1 (NF-Y) activity results in transcriptional down-regulation of topoisomerase IIalpha in a doxorubicin-resistant variant of human multiple myeloma RPMI 8226. 926 89

SDZ PSC 833 is a novel compound able to reverse the resistance to chemotherapy of cancer cells with the multidrug resistance (MDR) phenotype by inhibiting the 170 kd P-glyco-protein (P-gp). In vitro studies show that SDZ PSC 833 directly interacts with, but is not transported by P-gp, although the exact mechanism of action has not yet been defined. In cells with the MDR phenotype, intracellular concentration of various P-gp-transported anticancer drugs is restored to the same level as in sensitive cells by SDZ PSC 833 concentrations of 0.8 microM to 3.0 microM. In vivo SDZ PSC 833 was highly active in potentiating the anti-tumour activity of all tested anticancer drugs (ACs) in both sensitive and MDR tumours. Sensitivity of non-MDR tumours was increased by SDZ PSC 833 through pharmacokinetic interactions, that result in enhanced area-under-the-curve (AUC) of P-gp-transported ACs. However, an increased AC bioavailability is not sufficient to explain the therapeutic benefit of SDZ PSC 833 co-treatment in MDR tumour-bearing mice: in these animals, no survival increase could be achieved with the AC alone by simply increasing the cytotoxin dosage up to doses that were severely toxic for the non-tumour-bearing mice. In a series of phase I/II studies, the recommended doses of SDZ PSC 833 were established at: 10 mg/kg/day i.v. as a 24-hour continuous infusion after a 2 mg/kg loading dose as a 2-hour infusion; 20 mg/kg orally divided four times daily in solid tumours or 16 mg/kg orally divided four times daily in multiple myeloma. The dose limiting toxicity of SDZ PSC 833 is ataxia, which appears to be reversible and dose-related. Moreover, a predictable change in pharmacokinetic parameters of concomitantly administered P-gp-transported AC(s) which usually necessitate a 30-60% reduction from the standard dose of the AC in order to maintain the same time-exposure and dose-related toxicity of the cytotoxic drug alone. The results of experiments both in vitro and in vivo suggested that adequate blood levels (i.e. > or = 1.0 microM) of SDZ PSC 833 must be reached before and maintained during the administration of concomitant AC(s), in order to maximally reverse MDR. At the recommended doses, blood concentrations exceeding 1000 ng/mL (1.0 microM) can be achieved after both i.v. and oral administration. Indeed, SDZ PSC 833 concentrations that fully reverse MDR in vitro are achievable in vivo, plasma samples from patients treated with SDZ PSC 833 restored the sensitivity of MDR human sarcoma cells to paclitaxel, etoposide and doxorubicin. Clinical studies completed so far aimed first to determine the dose of both SDZ PSC 833 and the concomitant AC(s) to be used in ongoing pivotal trials. These studies accrued advanced stage cancer patients, however, tumour responses have been observed in both solid and hematological tumours. The in vitro finding that treatment with SDZ PSC 833 may suppress the activation of the MDR1 gene and prevent the emergence of resistant cancer cell clones with the MDR phenotype might support the use of this MDR modulator in earlier stages of disease.
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PMID:[SDZ PSC 833: a novel modulator of MDR]. 944 55

A 46-year-old female presented with acute myeloid leukemia during complete remission of multiple myeloma after extensive treatment with alkylating agents. Leukemic blasts expressed CD34, platelet esterase and gp IIIa. RT-PCR analyses of peripheral blood cells detected a p190 type BCR-ABL rearrangement and high levels of MDR1. The patient expired during neutropenia shortly after induction chemotherapy. Autopsy revealed persistent blasts in the bone marrow, spleen and liver. 'Secondary' acute myeloid leukemia with megakaryoblastic features and p190-type BCR-ABL rearrangement has not previously been reported. The possibility that the combination of a BCR-ABL rearrangement with overexpression of MDR1 may have contributed to the treatment-refractory course is discussed.
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PMID:Drug resistance of secondary acute myeloid leukemia with megakaryoblastic features and p190 BCR-ABL rearrangement. 978 5

RT-PCR method was used to detect the expression level of multi-drug resistance gene (MDR1) and multi-drug resistance associated protein (MRP) in patients with malignant blood disease, including 19 cases of acute leukemia and 6 cases of multiple myeloma. The results showed: expression level of MDR1 in patients with known clinical drug resistance elevated obviously and was significantly associated with clinical drug resistance (r = 0.612, P < 0.01), which indicated that expression of MDR1 was the main mechanism of clinical drug resistance. There is no obvious relationship between expression level of MDR1 and MRP (r = 0.035, P > 0.05).
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PMID:[Expression level of MDR1, and MRP in patients with malignant blood disease and its clinical significance]. 986 94


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