Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:5.99.1.2 (topoisomerase)
9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An actinomycin D selected, multidrug-resistant (MDR) hamster CHO subline showed strong expression of the P-glycoprotein and sorcin genes together with several other alterations such as a: (i) reduced growth rate, (ii) lowered topoisomerase II, (iii) lowered glutathione-S-transferase-P gene expression, and (iv) the emergence of a 15.5 kDa protein. Besides high resistances to adriamycin, actinomycin D, and vincristine, we observed a lowered sensitivity towards bleomycin, a rather hydrophilic drug usually not involved in P-glycoprotein associated MDR. Moreover, the MDR subline showed a pronounced collateral (enhanced) sensitivity towards the sterically pure dihydropyridine anticancer drug dexniguldipine-HCl (B859-35) preventing its characterization for MDR modulation here. At a non-cytotoxic dose (10 microM) the immunosuppressive cyclic peptide cyclosporin A completely abolished the resistance to vincristine, partially reversed the resistance to teniposide and strongly enhanced the sensitivity towards bleomycin, while not influencing the drug sensitivities of the parental cell line. Buthionine sulfoximine (BSO), an agent depleting cellular glutathione levels, distinctly increased the sensitivity towards teniposide at nontoxic doses (50 microM) exclusively in the MDR subline, while it did not alter vincristine or bleomycin cytotoxicity.
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PMID:MDR hamster cells exhibiting multiple altered gene expression: effects of dexniguldipine-HCl (B859-35), cyclosporin A and buthionine sulfoximine. 128 2

The two-year survival rate of patients with small cell lung cancer is less than 10%. The major reason for this poor outcome is the development of drug resistance. Panels of small cell lung cancer cell lines have been established, providing models for the study of drug resistance in this tumour. One such model is the doxorubicin-selected H69AR cell line. H69AR displays the typical multidrug resistance phenotype in that it is cross-resistant to anthracyclines, Vinca alkaloids (e.g., vinblastine) and epipodophyllotoxins (e.g., VP-16). However, H69AR cells do not overexpress P-glycoprotein, the membrane drug efflux pump frequently found on multidrug resistant cells. Some alterations in glutathione levels and associated enzyme activities were found but the data do not support the notion that enhanced drug detoxication is involved in H69AR cell resistance. Fewer drug-induced DNA strand breaks, reduced levels of topoisomerase II, and reduced formation of drug-stabilized DNA/topoisomerase II complexes were observed in H69AR cells. These data implicate topoisomerase II in the resistance phenotype of H69AR cells, but cannot explain H69AR cell resistance to the Vinca alkaloids, which do not have topoisomerase II as a target. Monoclonal antibodies against antigens overexpressed on H69AR cells have been derived and four have been characterized. Immunoscreening of an H69AR cDNA expression library has allowed the identification of one of these antigens as p36 (annexin II), a Ca2+/phospholipid binding protein. Chemosensitizers and novel xenobiotics have been examined for their ability to circumvent the drug resistance of H69AR cells. The limited success of these investigations suggests that innovative approaches may be required. In conclusion, the data obtained with H69AR and other models of small cell lung cancer indicate that multiple mechanisms contribute to drug resistance in this disease.
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PMID:The 1991 Merck Frosst Award. Multidrug resistance in small cell lung cancer. 131 57

Drugs that interfere with the action of P-glycoprotein (P-gp), the membrane efflux pump responsible for multidrug resistance (MDR), should be valuable in the treatment of patients with drug-resistant cancer. We have used one class of drug, the phenothiazines, to study the structural features required for optimum interference with the function of P-gp. The structure-activity relationships revealed three important components including the hydrophobicity of the tricyclic ring, the length of the alkyl bridge and the charge on the terminal amino group. Trans-flupenthixol is a lead compound that conforms to these structural requirements and demonstrates significant activity as a sensitizer of MDR cell lines to drugs affected by the MDR phenotype. Based on these data, we have proposed a model for the binding of modulators to P-gp and have speculated on the structure of the drug-binding domain. We have developed pre-clinical models of MDR that may help predict clinical activity of chemo-modulators. L1210/VMDRC.06 is a murine lymphocytic leukemia line transformed by a retroviral expression vector containing a full-length cDNA for the human mdr1 gene. K562/VBL1-3 are clones of human myeloid blast cells that were transformed with the same vector. Resistance in these lines is not complicated by changes in the cellular content of glutathione or alterations in topoisomerase II. The transformed L1210 line grows in mice as a slowly proliferating non-metastatic peritoneal implant. Both MDR lines are restored to sensitivity by cyclosporin A or trans-flupenthixol, and the K562 clones are induced to differentiate by hemin. These lines should provide simple, sensitive screens for new drugs for use against cancers expressing P-gp. We have proposed a model to explain how the pumping activity of P-gp is activated in response to toxic drugs. In this schema, basal activity of P-gp is modulated through phosphorylation/dephosphorylation reactions mediated by protein kinase C (PKC) and calcium sensitive phosphatases. In response to the activation of phospholipase C by toxic drugs and the local production of 1,2-diacylglycerol, PKC is translocated to the cell membrane where it phosphorylates P-gp. Following the extrusion of drug from the cell membrane, phospholipase C activity returns to baseline, diacylglycerol is metabolized, PKC returns to the cytosol and serine/threonine phosphatases dephosphorylate P-gp returning it to the basal state.
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PMID:Rational design and pre-clinical pharmacology of drugs for reversing multidrug resistance. 134 93

A non-P-glycoprotein-mediated mechanism of multidrug resistance (non-Pgp MDR) has been identified in doxorubicin-selected sublines of the human non-small cell lung carcinoma cell line SW-1573. These sublines are cross-resistant to daunorubicin, VP16-213, Vinca alkaloids, colchicine, gramicidin D, and 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA). They accumulate less drug than the parental cells and their resistance is not due to the MDR1-encoded P-glycoprotein, as the resistant cell lines have lost the low amount of MDR1 mRNA detectable in parental cells. Here we show that the resistant cell lines also contain less topoisomerase II mRNA and enzyme activity than the parental cells. This might contribute to the resistance of these lines to drugs interacting with topoisomerase II, such as doxorubicin, daunorubicin, and VP16-213, but cannot account for the resistance to the other drugs. We have tested whether all properties of the non-Pgp MDR cell lines cosegregate in somatic cell fusions between lethally gamma-irradiated, resistant donor cells and drug-sensitive acceptor cells. Whereas a MDR phenotype with reduced drug accumulation and the loss of MDR1 P-glycoprotein mRNA were cotransferred to the acceptor cells, the decrease in topoisomerase II gene expression was not. We conclude that the MDR phenotype, the reduced drug accumulation, and the loss of MDR1 P-glycoprotein mRNA are genetically linked. They might be due to a single dominant mutation, which does not cause the alteration in topoisomerase II.
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PMID:Genetic transfer of non-P-glycoprotein-mediated multidrug resistance (MDR) in somatic cell fusion: dissection of a compound MDR phenotype. 134 62

N-Benzyladriamycin-14-valerate (AD 198) is a highly lipophilic analogue of Adriamycin with novel cytotoxic mechanisms, greater in vivo antitumor activity, and the ability to circumvent multidrug resistance due to P-glycoprotein-mediated drug efflux or decreased topoisomerase II activity. To identify the mechanism(s) which may confer AD 198 resistance, J774.2 mouse macrophage-like cells were selected for growth in cytotoxic levels of AD 198 (AD 198R). AD 198R cells exhibited over-expression of the mdr1b (P-glycoprotein) gene, cross-resistance to Adriamycin and vinblastine, and potentiation of drug cytotoxicity by verapamil. However, net intracellular accumulation of AD 198 in AD 198R cells was unchanged compared to parental cells, while Adriamycin and vinblastine accumulations were reduced 40% and 95%, respectively. AD 198 was localized in the perinuclear region of the cytoplasm in both parental and AD 198R cells, with additional vesicular compartmentalization in AD 198R cells. Verapamil-induced reversal of AD 198 resistance coincided with some drug redistribution from cytoplasmic vesicles, but without redistribution of AD 198 into the nucleus. These results suggest that AD 198 resistance was not conferred through a P-glycoprotein-mediated reduction in intracellular drug accumulation but through other cytoplasmic mechanisms, including, but not limited to, drug compartmentalization.
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PMID:Resistance to N-benzyladriamycin-14-valerate in mouse J774.2 cells: P-glycoprotein expression without reduced N-benzyladriamycin-14-valerate accumulation. 135 Jul 53

An etoposide-resistant subline, SBC-3/ETP, from a human small cell lung cancer cell line, SBC-3, was developed by continuous exposure to increasing concentrations of etoposide in culture. The SBC-3/ETP was 52.1-fold more resistant to etoposide than the parent cell line. The SBC-3/ETP was highly cross-resistant to teniposide, adriamycin, vinca alkaloids, 4-hydroperoxycyclophosphamide, CPT-11 and mitomycin C, and marginally cross-resistant to cisplatin, while the subline showed a collateral sensitivity to bleomycin. Topoisomerase I activity in the SBC-3/ETP was reduced to an extent of one half and topoisomerase II activity to an extent of one eighth in comparison with those of the SBC-3. Intracellular accumulation of [3H]-etoposide in the SBC-3/ETP was significantly lower in comparison to the SBC-3. An overexpression of MDR1 mRNA, and the presence of its product, P-glycoprotein, were detected in the SBC-3/ETP by Northern blotting and flowcytometry using a monoclonal antibody of the protein, MRK16. These results indicate that a decreased activity of topoisomerase II is the major factor for the development of etoposide resistance, and that an overexpression of the MDR1 gene is responsible, in part, for the development of resistance to the drug and some structurally unrelated compounds such as adriamycin and vinca alkaloids.
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PMID:Establishment and characterization of an etoposide-resistant human small cell lung cancer cell line. 135 8

Thirty human renal cell carcinomas and 94 non-small cell lung carcinomas of previously untreated patients were analyzed for the presence of P-glycoprotein, glutathione S-transferase-pi and topoisomerase II by means of immunohistochemistry. In the renal cell carcinomas investigated, two resistance markers were seen in 53% and three resistance markers in 36% of the cases. In only three tumors was one resistance mechanism observed. In the 94 non-small cell lung carcinomas 34% had two and 20% three resistance mechanisms, whereas 24% of the tumors revealed only one resistance mechanism. For determining the resistance of the tumors against drugs an in vitro short-term test was used. Only 12% of the sensitive lung tumors had more than one resistance mechanism, whereas 70% of the resistant tumors did. Thus a significant relationship exists between the resistance measured in vitro and the overexpression of P-glycoprotein or glutathione S-transferase-pi and the down-regulation of topoisomerase II.
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PMID:Expression of several resistance mechanisms in untreated human kidney and lung carcinomas. 135 30

In a variety of adult and childhood leukaemia cell samples collected at different states of the disease, we analysed in a series of sequentially performed slot-blot or Northern-blot hybridisation experiments the expression of genes possibly involved in multiple drug resistance (MDR) (mdr1/P-glycoprotein, DNA topoisomerase II, glutathione-S-transferase pi), and the expression of the DNA topoisomerase I and histone 3.1 genes. Occasionally, P-glycoprotein gene expression was additionally examined by indirect immunocytofluorescence using the monoclonal antibody C219. No significant difference in mdr1/P-glycoprotein mRNA levels between primary and relapsed state acute lymphocytic leukaemias (ALL) was seen on average. Second or third relapses, however, showed a distinct tendency to an elevated expression of this multidrug transporter gene (up to 10-fold) in part well beyond the value seen in the moderately cross-resistant T-lymphoblastoid CCRF-CEM subline CCRF VCR 100. Increased mdr1/P-glycoprotein mRNA levels were also found in relapsed state acute myelogenous leukaemias (AML), and in chronic lymphocytic leukaemias (CLL) treated with chlorambucil and/or prednisone for several years. Topoisomerase I and topoisomerase II mRNA levels were found to be very variable. Whereas in all but one case of CLL topoisomerase II mRNA was not detected by slot-blot hybridizations, strong topoisomerase I and topoisomerase II gene expression levels, frequently exceeding the levels monitored in the CCRF-CEM cell line, were seen in many cell samples of acute leukaemia. If topoisomerase II mRNA was undetectable, expression of topoisomerase I was clearly visible throughout. These observations might be valuable considering the possible treatment with specific topoisomerase I or topoisomerase II inhibitors. Significant positive correlations were found (i) for topoisomerase I and histone 3.1 gene expression levels in general (P less than 0.001), and (ii) in the CLL samples additionally for the expression levels of the mdr1 gene, and the histone 3.1, topoisomerase I, and glutathione-S-transferase pi genes, respectively.
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PMID:Mdr1/P-glycoprotein, topoisomerase, and glutathione-S-transferase pi gene expression in primary and relapsed state adult and childhood leukaemias. 135 60

Reduced drug accumulation is the most common functional change accompanying development of P-glycoprotein-associated multidrug resistance. One of our laboratories showed earlier that the anthracycline analogue 4'-deoxy-4'-iododoxorubicin (DIDOX) was accumulated to identical levels in Ehrlich ascites tumor (EHR2) and daunorubicin (DNR)-resistant EHR2/DNR+ cells (E. Friche, P. B. Jensen, T. Skovsgaard, and N. I. Nissen, J. Cell. Pharmacol., 1:57-65, 1990). In this communication, we show that weekly treatment of EHR2-bearing mice with 4, 8, or 12 mg of DIDOX/kg/week led to the development of three DIDOX-resistant cell lines, EHR2/DIDOX-1, EHR2/DIDOX-2, and EHR2/DIDOX-3. The levels of DIDOX accumulation and retention and its outward transport were similar in the drug-sensitive and three drug-resistant cell lines. By contrast, the accumulation of the active DIDOX metabolite, 13-dihydro-DIDOX (13-OH-DIDOX), the parent compound doxorubicin, and daunorubicin were all decreased in proportion to the resistance of the cells. In EHR2/DIDOX-3 cells, the reduction in daunorubicin accumulation coincided with the development of P-glycoprotein as demonstrated by Western blot and flow cytometry with C219 antibody. DIDOX had no effect on the photolabeling of P-glycoprotein by [3H]azidopine, whereas 13-OH-DIDOX inhibited this labeling in a concentration-dependent manner. Subsequent analysis of topoisomerase II activities and amounts in EHR2/DIDOX-3 cells revealed decreased DNA topoisomerase II catalytic activity. The amounts of immunoreactive DNA topoisomerase II from EHR2/DIDOX-1, EHR2/DIDOX-2, and EHR2/DIDOX-3 cells were about 89%, 73%, and 52%, respectively, of that seen in the drug-sensitive cells. We also found that teniposide stabilized DNA-protein complexes in EHR2/DIDOX-3 but they never reached the level seen in EHR2 cells. Because it has been reported that DIDOX is rapidly metabolized to 13-OH-DIDOX, we postulate that the development of resistance to DIDOX in vivo is due in part to its metabolite, 13-OH-DIDOX, which is a substrate for plasma membrane glycoprotein, and in part to DIDOX, which is an inhibitor of topoisomerase II.
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PMID:Characterization of tumor cell resistance to 4'-deoxy-4'-iododoxorubicin developed in Ehrlich ascites cells in vivo. 135 19

A mitoxantrone-resistant human MCF-7 breast cancer subline (MCF/MX) which is approximately 4000-fold resistant to mitoxantrone was isolated by serial passage of the parental wild-type MCF-7 cells (MCF/WT) in stepwise increasing concentrations of drug. MCF/MX cells were also approximately 10-fold cross-resistant to doxorubicin and etoposide but were not cross-resistant to vinblastine. Intracellular accumulation of radiolabeled mitoxantrone was markedly reduced in MCF/MX cells relative to that in the drug-sensitive MCF/WT cells. This decrease in intracellular drug accumulation into MCF/MX cells was associated with enhanced drug efflux, which was reversed when cells were incubated in the presence of sodium azide and 2, 4-dinitrophenol, suggesting an energy-dependent process. Incubation of MCF/MX cells with verapamil did not affect either the accumulation of mitoxantrone or the level of resistance in these cells. Furthermore, RNase protection and Western blot analyses failed to detect the expression of the mdr1 RNA or P-glycoprotein, a drug efflux pump known to be associated with the development of multidrug resistance in vitro. However, a polyclonal antibody directed against a synthetic peptide corresponding to the putative ATP binding domain of P-glycoprotein reacted with two (M(r) 42,000 and 85,000) membrane proteins from MCF/MX cells which were not found in MCF/WT. Functional assays and Western blot analysis for topoisomerase II revealed no differences in topoisomerase II activity or protein levels in MCF/MX cells. Thus, resistance in this cell line is apparently associated with enhanced drug efflux involving a pathway distinct from the mdr1-encoded multidrug transporter P-glycoprotein.
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PMID:Reduced intracellular drug accumulation in the absence of P-glycoprotein (mdr1) overexpression in mitoxantrone-resistant human MCF-7 breast cancer cells. 135 31


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