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)

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

Colorectal cancer is one of the most common cancers in the Western World. Although 50% of patients are cured by surgery alone, the outcome is poor in high-risk patients (Dukes stages B2 and C) despite adjuvant chemotherapy with 5-fluorouracil (5-FU)-based regimens. CPT-11 (irinotecan) is a promising new agent for the treatment of colorectal cancer with a unique mechanism of action. CPT-11 is a DNA topoisomerase I inhibitor, which has not demonstrated susceptibility to the P-glycoprotein-mediated multidrug-resistant phenotype. Phase II studies with CPT-11 have demonstrated definite activity against colorectal cancer in both chemotherapy-naive and pretreated patients (response rates of 15-32% observed) even with clinical evidence of resistance to 5-FU. The response rate appears to be consistent, reproducible and equivalent to that achieved with 5-FU plus folinic acid in chemotherapy-naive patients.
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PMID:CPT-11 (irinotecan) in the treatment of colorectal cancer. 757 37

We have previously described a mitoxantrone-resistant human breast carcinoma cell line, MCF7/MX, in which resistance was associated with a defect in the energy-dependent accumulation of mitoxantrone in the absence of P-glycoprotein overexpression (M. Nakagawa et al., Cancer Res. 52: 6175-6181, 1992). We now report that this cell line is highly cross-resistant to the camptothecin analogues topotecan (180-fold), 9-aminocamptothecin (120-fold), CPT-11 (56-fold), and SN38 (101-fold), but is only mildly cross-resistant to the parent compound camptothecin (3.2-fold) and 10,11-methylenedioxy-camptothecin (2.9-fold). Topotecan accumulation was decreased in MCF7/MX cells compared to parental MCF7/WT cells, and there was a corresponding reduction in topotecan-mediated stimulation of the enzyme/DNA complex formation in MCF7/MX cells compared to MCF7/WT cells. No overexpression of the multidrug resistance-associated protein was detected compared to parental MCF7/WT cells. Furthermore, both sensitive MCF7/WT and mitoxantrone-resistant MCF7/MX cells contain equal amounts of DNA topoisomerase I protein, and DNA relaxation activities were equal in both cell lines and inhibited to the same extent by topotecan and camptothecin. Thus, these results suggest a novel mechanism of resistance to topoisomerase I inhibitors in cancer cells.
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PMID:Cross-resistance to camptothecin analogues in a mitoxantrone-resistant human breast carcinoma cell line is not due to DNA topoisomerase I alterations. 766 72

Over the past decade, DNA topoisomerase I and II appeared to be the targets of some antitumor agents: CPT-11 and Topotecan derived from Camptothecin which interact with topoisomerase I; Actinomycin D, Adriamycin and Daunorubicin, Elliptinium Acetate, Mitoxantrone, Etoposide and Teniposide, Amsacrine which interact with topoisomerase II. The multiple functions of these enzymes are important as they play a role during replication, transcription, recombination, repair and chromatine organisation. Particularly, they relax torsional constraints which appear when intertwined DNA strands are separated while replication fork or RNA polymerases are moving. To some extent, topoisomerase I and II are structurally and functionally different. Moreover, topoisomerase I is not indispensable for a living cell whereas topoisomerase II is. Drug-topoisomerase interaction which probably leads to antitumoral effect of the compounds studied in this review is not a trivial inhibition of the enzyme but rather a poisoning due to stabilization of cleavable complexes between the enzyme and DNA. These stabilized complexes are likely to induce apoptosis-like programmed cell death, which is characterised by DNA fragmentation. However, it appears that it is the collision of the replication fork with the drug-stabilized cleavable complex that is responsible for the cytotoxicity of the drug: poisoning of topoisomerases by antitumor agents leads to a new concept of "dynamic toxicity". Although they interact with a common target, topoisomerase II poisons have differential effects on macromolecules syntheses, cell cycle and chromosome fragmentation; a few compounds may produce free radicals. Because of these differential effects in addition to quantitative and qualitative variations of stabilized cleavable complexes, in particular DNA sequences on which topoisomerase II is stabilized, these antitumor agents do not resemble each other. Cellular resistance to topoisomerases poisons results of two principal types of alteration: target and/or drug transport modification. Decreased ability to form the cleavable complex in resistant cells may be the consequence of both decreased amount of topoisomerase or altered enzyme. On the other hand, overexpression of membrane P-glycoprotein, which pumps drugs out of the cell by an energy dependent process provokes a decreased accumulation of these drugs. Cross resistances to other drugs are mainly under control of these two different mechanisms of resistance. A complete knowledge of their individual effects and mechanisms of resistance would allow a better clinical use of topoisomerases poisons, especially when administered in combination chemotherapy.
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PMID:[Poisons of DNA topoisomerases I and II]. 808 Oct 34

In order to clarify the mechanism of drug resistance in human myeloma cells, we investigated the expressions of DNA topoisomerase I and topoisomerase II gene and the genes possibly related to drug resistance; multi-drug resistant gene 1 (MDR-1), glutathione S-transferase class pi gene (GST-pi), by Northern blotting. Myeloma cells in eight of 15 cases prior to chemotherapy expressed topoisomerase I mRNA considerably, while the expression of topoisomerase II mRNA was detected weakly in only one of 16 myeloma patients. There was not any correlation between expression of topoisomerase I mRNA and clinical drug resistance. Significant expression of MDR-1 mRNA and P-glycoprotein was not detected in 25 cases of multiple myeloma prior to chemotherapy and even after several courses of VAD (vincristine, adriamycin and dexamethasone) therapy by Northern blotting and immunostaining using monoclonal anti-P-glycoprotein antibody (MRK-16), respectively. On the other hand, 16 of 21 myeloma cases showed significant expression of GST-pi protein and GST-pi mRNA with the various strengths, but there was no apparent correlation between GST-pi mRNA expression and clinical response. Therefore these data suggest that expression of the genes we tested may not determine the level of drug resistance in multiple myeloma, but lower or no significant expression of topoisomerase II mRNA in most myeloma cells indicates the possibility that topoisomerase II inhibitors such as VP-16 and topoisomerase II-mediated cytotoxic drugs such as adriamycin, are not so effective for the treatment of multiple myeloma.
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PMID:Expressions of DNA topoisomerase I and II gene and the genes possibly related to drug resistance in human myeloma cells. 809 26

The development of camptothecin-like compounds as inhibitors of DNA topoisomerase I for the treatment of solid tumors has generated clinical excitement in this new class of drugs. We have discovered, developed, and entered into clinical trial a novel, potent, and water-soluble camptothecin analog with significant antitumor activity. This compound, Gl147211C [7-(4-methylpiperaziinomethylene)-10, 11-ethylenedioxy-20(S)-camptothecin hydrochloride] is a specific inhibitor of DNA topoisomerase I. Compared to topotecan, Gl147211C is approximately three times as potent in the cleavable complex assay and approximately twice as soluble in aqueous medium. Human tumor cell line cytotoxicity assays indicated that Gl147211C was approximately 3- to 5-fold more potent than topotecan, while both compounds were relatively insensitive to the multidrug resistance P-glycoprotein. The in vivo preclinical antitumor activity of Gl147211C was compared to topotecan in an array of human tumor xenograft models in nude mice. In general, Gl147211C was able to induce regression of established tumors whereas topotecan was not. Microscopic evaluation of necropsied tissues indicated that drug-induced toxicity was mild, primarily limited to the gastrointestinal tract, and was comparable for both Gl147211C and topotecan. Based on these observations, Gl147211C moved through preclinical development and subsequently into Phase I clinical trial. A summary of Phase I trial results to date is provided.
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PMID:Topoisomerase I inhibition by the camptothecin analog Gl147211C. From the laboratory to the clinic. 899 13

The expression of different genes potentially involved in DNA repair and in cell responses to chemotherapy was evaluated in 33 previously untreated ovarian cancer patients. In biopsies of the same patients the expression of repair genes O6-methylguanine DNA methyltransferase (MGMT), 3-methyladenine DNA glycosylase (MAG), ERCC1, MDR-1, DNA topoisomerase I, DNA topoisomerase IIalpha, and glutathione S-transferase-pi (GST-pi) was assessed by Northern blot analysis. No direct statistical correlation was found between the expression of these genes and the response to chemotherapy (mainly platinum-based with or without doxorubicin and cyclophosphamide). Univariate analysis showed a weak negative correlation (P = 0.037) between the expression of ERCC1 and mortality, whereas no statistically significant correlation was found for other parameters. The MDR-1 gene encoding for the P-glycoprotein P-170 was mostly undetectable in these patients (as assessed by Northern blotting), whereas relatively high levels of MAG and MGMT were found in the majority of patients. A statistically significant correlation was found between the expression of DNA topoisomerase I and the expression of either ERCC1 (P = 0.0026) or GST-pi (P = 0.0279).
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PMID:Expression of genes of potential importance in the response to chemotherapy and DNA repair in patients with ovarian cancer. 910 2

Non-P-glycoprotein-mediated multidrug-resistant C-A120 cells that overexpressed multidrug resistance protein (MRP) were 10.8- and 29. 6-fold more resistant to 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11) and SN-38, respectively, than parental KB-3-1 cells. To see whether MRP is involved in CPT-11 and SN-38 resistance, MRP cDNA was transfected into KB-3-1 cells. The transfectant, KB/MRP, which overexpressed MRP, was resistant to both CPT-11 and SN-38. 2-[4-Diphenylmethyl)-1-piperazinyl]ethyl-5-(trans-4,6-dimethyl-1,3 , 2-dioxaphosphorinan-2-yl)-2, 6-dimethyl-4-(3-nitrophenyl)-3-pyridinecarboxylate P-oxide (PAK-104P) and MK571, which reversed drug resistance in MRP overexpressing multidrug-resistant cells, significantly increased the sensitivity of C-A120 and KB/MRP cells, but not of KB-3-1 cells, to CPT-11 and SN-38. The accumulation of both CPT-11 and SN-38 in C-A120 and KB/MRP cells was lower than that in KB-3-1 cells. The treatment with 10 microM PAK-104P increased the accumulation of CPT-11 and SN-38 in C-A120 and KB/MRP cells to a level similar to that found in KB-3-1 cells. The ATP-dependent efflux of CPT-11 and SN-38 from C-A120 and KB/MRP cells was inhibited by PAK-104P. DNA topoisomerase I expression, activity, and sensitivity to SN-38 were similar in the three cell lines. Furthermore, the conversion of CPT-11 to SN-38 in KB-3-1 and C-A120 cell lines was similar. These findings suggest that MRP transports CPT-11 and SN-38 and is involved in resistance to CPT-11 and SN-38 and that PAK-104P reverses the resistance to CPT-11 and SN-38 in tumors that overexpress MRP.
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PMID:ATP-Dependent efflux of CPT-11 and SN-38 by the multidrug resistance protein (MRP) and its inhibition by PAK-104P. 1022 May 71

Pyrazoloacridine (PZA) is the first of a new class of rationally synthesized acridine derivatives to undergo clinical testing as an anticancer agent. Recent studies suggest that PZA might be a dual inhibitor of DNA topoisomerase I and DNA topoisomerase II that exerts its effects by diminishing the formation of topoisomerase-DNA adducts. Consistent with this unique mechanism of action, PZA exhibits broad spectrum antitumor activity in preclinical models in vivo. In addition, this agent displays several unique properties including solid tumor selectivity, activity against hypoxic cells, and cytotoxicity in noncycling cells. PZA also retains full activity against cells that are resistant to other agents on the basis of overexpression of P-glycoprotein or the multidrug resistance-associated protein (MRP). PZA has been studied in phase I trials in adults and children, and is currently undergoing broad phase II trials in a number of tumor types. No significant anti-tumor activity has been seen in gastrointestinal malignancies and prostate cancer. Results from ongoing or recently completed trials are awaited before the utility of this agent in our current armamentarium can be defined. Because of its unique properties, combination studies with other antineoplastic agents are warranted.
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PMID:Current status of pyrazoloacridine as an anticancer agent. 1055 21

We have previously described a mitoxantrone-resistant MCF7 cell line that is cross-resistant to topotecan, 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxy-camptothecin (CPT-11), and 9-aminocamptothecin, but not to camptothecin. A novel mechanism that resulted in decreased topotecan accumulation in MCF7/MX cells was proposed (Yang et al. Cancer Res 55: 4004-4009, 1995). We now have developed a topotecan-resistant cancer cell line from wild-type MCF7 cells. MCF7/TPT300 cells were 68.9-fold resistant to topotecan, 68.3-fold to 10-hydroxy-7-ethylcamptothecin (SN-38), and 116-fold to mitoxantrone, but only 4.1-fold to camptothecin. Topotecan efflux was increased in MCF7/TPT300 cells compared with MCF7/WT cells, and this increase was reversed upon ATP depletion by sodium azide, suggesting an energy-dependent drug efflux mechanism. However, MCF7/TPT300 cells did not overexpress P-glycoprotein or the multidrug resistance-associated protein (MRP1). In contrast, overexpression of the breast cancer resistance protein (BCRP/MXR/ABCP) was observed in MCF7/TPT300 cells as well as DNA topoisomerase I down-regulation. Our data suggest that enhanced topotecan efflux contributes partly to topotecan resistance in MCF7/TPT300 cells, possibly mediated by BCRP/MXR/ABCP.
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PMID:BCRP/MXR/ABCP expression in topotecan-resistant human breast carcinoma cells. 1093 May 38


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