701
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702
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Loo TW, Bartlett MC, Clarke DM. Drug binding in human P-glycoprotein causes conformational changes in both nucleotide-binding domains. J Biol Chem 2003; 278:1575-8. [PMID: 12421806 DOI: 10.1074/jbc.m211307200] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human multidrug resistance P-glycoprotein (P-gp, ABCB1) uses ATP to transport many structurally diverse compounds out of the cell. It is an ABC transporter with two nucleotide-binding domains (NBDs) and two transmembrane domains (TMDs). Recently, we showed that the "LSGGQ" motif in one NBD ((531)LSGGQ(535) in NBD1; (1176)LSGGQ(1180) in NBD2) is adjacent to the "Walker A" sequence ((1070)GSSGCGKS(1077) in NBD2; (427)GNSGCGKS(434) in NBD1) in the other NBD (Loo, T. W., Bartlett, M. C., and Clarke, D. M. (2002) J. Biol. Chem. 277, 41303-41306). Drug substrates can stimulate or inhibit the ATPase activity of P-gp. Here, we report the effect of drug binding on cross-linking between the LSGGQ signature and Walker A sites (Cys(431)(NBD1)/C1176C(NBD2) and Cys(1074)(NBD2)/L531C(NBD1), respectively). Seven drug substrates (calcein-AM, demecolcine, cis(Z)-flupentixol, verapamil, cyclosporin A, Hoechst 33342, and trans(E)-flupentixol) were tested for their effect on oxidative cross-linking. Substrates that stimulated the ATPase activity of P-gp (calcein-AM, demecolcine, cis(Z)-flupentixol, and verapamil) increased the rate of cross-linking between Cys(431)(NBD1-Walker A)/C1176C(NBD2-LSGGQ) and between Cys(1074)(NBD2-Walker A)/L531C(NBD1-LSGGQ) when compared with cross-linking in the absence of drug substrate. By contrast, substrates that inhibited ATPase activity (cyclosporin A, Hoechst 33342, and trans(E)-flupentixol) decreased the rate of cross-linking. These results indicate that interaction between the LSGGQ motifs and Walker A sites must be essential for coupling drug binding to ATP hydrolysis. Drug binding in the transmembrane domains can induce long range conformational changes in the NBDs, such that compounds that stimulate or inhibit ATPase activity must decrease and increase, respectively, the distance between the Walker A and LSGGQ sequences.
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Affiliation(s)
- Tip W Loo
- Canadian Institutes for Health Research Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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703
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Affiliation(s)
- John A Kellen
- Department of Laboratory Medicine and Pathobiology of Human Disease, University of Toronto, Toronto, Ont., Canada.
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704
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Jin J, Huang M, Wei HL, Liu GT. Mechanism of 5-fluorouracil required resistance in human hepatocellular carcinoma cell line Bel 7402. World J Gastroenterol 2002; 8:1029-34. [PMID: 12439919 PMCID: PMC4656374 DOI: 10.3748/wjg.v8.i6.1029] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the resistance mechanism of 5-fluorouracil (5-FU) in Bel7402/5-FU cells which was established in our lab by in vitro continuous stepwise exposure of human hepatocellular carcinoma (HCC) cell line Bel7402 to 5-FU.
METHODS: The expression of multidrug resistance-associated protein (MRP) and thymidylate synthase (TS) in Bel7402 cells was detected by immonocytochemistry. The fluorescein (FLU) accumulation, an index of MRP functional activity, was determined by flow cytometry. The distribution of FLU was observed by confocal laser scanning microscope. The spectrofluorometry was used to show the intracelluar content of glutathione (GSH). Cell growth inhibition was determined by MTT assay. The activity of glutathione S-transferases (GSTs) was determined by spectrophotometry.
RESULTS: A higher expression of MRP in the Bel7402/5-FU cells was observed by using monoclonal mouse anti-MRP antibody, MRPr-1, in comparison with Bel7402 cells. Bel7402/5-FU cells also showed a significant decrease of FLU accumulation. FLU mainly accumulated in the nucleus with a high nuclear/cytoplasmic ratio in Bel7402 cells, whereas there was no difference of FLU accumulation between the nucleus and cytoplasm in Bel7402/5-FU cells. The intracellular GSH content in Bel7402/5-FU cells was almost 3 folds higher than that in Bel7402 cells. Addition of D, L-buthione-S, R-sulfoximine (BSO) dose-dependently reduced the GSH content in Bel7402/ 5-FU cells, however, only a weak enhancement on the cytotoxicity of 5-FU and doxorubicin (Dox) to Bel7402/5-FU cells was observed. Bel7402/5-FU cells also exhibited 29.1% higher total GSTs activity than Bel7402 cells. Immunocytochemical staining by using anti-TS monoclonal antibody TS 106 showed that the level of TS in Bel7402/5-FU cells elevated markedly as compared with Bel7402 cells.
CONCLUSION: The continuous exposure of Bel7402 cells to 5-FU led to overexpression of TS and MRP, as well as increased intracellular GSH content and total GST activity.
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Affiliation(s)
- Jing Jin
- Department of Pharmacology, Institute of Materia Medica, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, People's Republic of China
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705
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Deferme S, Mols R, Van Driessche W, Augustijns P. Apricot extract inhibits the P-gp-mediated efflux of talinolol. J Pharm Sci 2002; 91:2539-48. [PMID: 12434397 DOI: 10.1002/jps.10262] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Within the framework of developing strategies to enhance the intestinal absorption of P-glycoprotein (P-gp) substrates, the modulatory effect of a standardized apricot extract on P-gp-related efflux carriers was investigated in the Caco-2 system, Ussing chambers and the rat in situ perfusion model using talinolol as a model substrate. Using the Caco-2 system, polarity in transport of talinolol could be observed, the absorptive transport being much lower than the secretory transport (P(app-abs) = 1.08 +/- 0.29 x 10(-6) cm/s and P(app-secr) = 11.74 +/- 0.80 x 10(-6) cm/s). Inclusion of apricot extract (1%) in the apical medium resulted in a statistically significantly diminished polarity (P(app-abs) = 4.88 +/- 0.96 x 10(-6) cm/s and P(app-secr) = 9.39 +/- 0.58 x 10(-6) cm/s, p < 0.05). In addition, the inhibitory effect of apricot extract on P-gp related efflux mechanisms was shown to be concentration (0% approximately 0.1% < 0.3% < 1%) and pH dependent. Experiments performed with the Ussing chambers resulted in similar observations. In the rat in situ perfusion model, inclusion of apricot extract (1%) in the perfusion medium resulted in a threefold increase of the amount of talinolol appearing in the collected blood compared to the reference condition (23.6 +/- 5.53 pmol/cm. min and 7.13 +/- 1.08 pmol/cm. min, respectively; p < 0.05). Coadministration of this standardized apricot extract might be a safe and useful strategy to enhance the intestinal absorption of P-gp substrates. The nature and structure of the compound(s) responsible for this inhibiting effect on P-gp-related efflux carriers remain to be elucidated, as well as the exact mechanism by which apricot extract exerts its inhibitory function.
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Affiliation(s)
- Sven Deferme
- Laboratory for Pharmacotechnology and Biopharmacy, Herestraat 49, Gasthuisberg, 3000 Leuven, Belgium
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706
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Loo TW, Clarke DM. Location of the rhodamine-binding site in the human multidrug resistance P-glycoprotein. J Biol Chem 2002; 277:44332-8. [PMID: 12223492 DOI: 10.1074/jbc.m208433200] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human multidrug resistance P-glycoprotein (P-gp) pumps a wide variety of structurally diverse compounds out of the cell. It is an ATP-binding cassette transporter with two nucleotide-binding domains and two transmembrane (TM) domains. One class of compounds transported by P-gp is the rhodamine dyes. A P-gp deletion mutant (residues 1-379 plus 681-1025) with only the TM domains retained the ability to bind rhodamine. Therefore, to identify the residues involved in rhodamine binding, 252 mutants containing a cysteine in the predicted TM segments were generated and reacted with a thiol-reactive analog of rhodamine, methanethiosulfonate (MTS)-rhodamine. The activities of 28 mutants (in TMs 2-12) were inhibited by at least 50% after reaction with MTS-rhodamine. The activities of five mutants, I340C(TM6), A841C(TM9), L975C(TM12), V981C(TM12), and V982C(TM12), however, were significantly protected from inhibition by MTS-rhodamine by pretreatment with rhodamine B, indicating that residues in TMs 6, 9, and 12 contribute to the binding of rhodamine dyes. These results, together with those from previous labeling studies with other thiol-reactive compounds, dibromobimane, MTS-verapamil, and MTS-cross-linker substrates, indicate that common residues are involved in the binding of structurally different drug substrates and that P-gp has a common drug-binding site. The results support the "substrate-induced fit" hypothesis for drug binding.
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Affiliation(s)
- Tip W Loo
- Canadian Institutes of Health Research Group in Membrane Biology, Department of Medicine, University of Toronto, Ontario M5S 1A8, Canada
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707
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Tseng E, Kamath A, Morris ME. Effect of organic isothiocyanates on the P-glycoprotein- and MRP1-mediated transport of daunomycin and vinblastine. Pharm Res 2002; 19:1509-15. [PMID: 12425469 DOI: 10.1023/a:1020460700877] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE Organic isothiocyanates (ITCs), or mustard oils, are non-nutrient components present in the diet, especially in cruciferous vegetables. The purpose of this investigation was to examine the effect of ITCs on P-glycoprotein (P-gp)- and multidrug resistance-associated Protein (MRP1)-mediated transport in multidrug resistant (MDR) human cancer cell lines. METHODS The direct effect of ITCs on the 2-h cellular accumulation of daunomycin (DNM) and vinblastine (VBL), substrates for both P-gp and MRP1, were measured in sensitive and resistant MCF-7 cells and in PANC-1 cells. Resistant MCF-7 cells (MCF-7/ADR) overexpress P-gp whereas PANC-1 cells overexpress MRP1. The following compounds were evaluated: allyl-, benzyl-(BITC), hexyl-, phenethyl-(PEITC), phenyl-, 1-naphthyl-(NITC), phenylhexyl-, phenylpropyl-, and phenylbutyl-ITC, sulforaphane, erucin, and erysolin. RESULTS NITC significantly increased the accumulation of DNM and VBL in both resistant cell lines, but had no effect on DNM accumulation in sensitive MCF-7 cells. VBL accumulation in resistant MCF-7 cells was increased 40-fold by NITC whereas that in PANC-1 cells was increased 5.5-fold. Significant effects on the accumulation of DNM and VBL in resistant MCF-7 cells were also observed with benzyl-isothiocyanate whereas PEITC, erysolin, phenylhexyl-ITC, and phenylbutyl-ITC increased the accumulation of DNM and/or VBL in PANC-1 cells. Overall, the inhibitory activities of these compounds in MCF-7 cells and PANC-1 cells were significantly correlated (r2 = 0.77 and 0.86 for DNM and VBL, respectively). Significant effects on accumulation were generally observed with the ITCs at 50 microM concentrations, but not at 10 microM concentrations. CONCLUSIONS One strategy to enhance the effectiveness of cancer chemotherapy is to reverse the MDR phenomena. Our results indicate that certain dietary ITCs inhibit the P-gp- and the MRP1-mediated efflux of DNM and VBL in MDR cancer cells and suggest the potential for diet-drug interactions.
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708
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Deferme S, Van Gelder J, Augustijns P. Inhibitory effect of fruit extracts on P-glycoprotein-related efflux carriers: an in-vitro screening. J Pharm Pharmacol 2002; 54:1213-9. [PMID: 12356275 DOI: 10.1211/002235702320402053] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
In this study, standardized food extracts were screened for their possible inhibitory effect on the P-glycoprotein (P-gp)-mediated efflux of 3H-ciclosporin A (CsA) using the in-vitro Caco-2 model. CsA is commonly used as a substrate for P-gp-related efflux carriers and is characterized by a polarity in transport, the absorptive transport being much lowerthan the secretorytransport (polarityfactor: PF approximately 7). Of the 68 tested, nine extracts showed a decreased efflux of CsA (< 75% of the reference value) and were retained for further experiments on the bidirectional transport of CsA across Caco-2 monolayers. Results of these experiments showed that strawberry, orange, apricot and mint extract exert an inhibitory effect on intestinal P-gp-related functionality (PF < 4.2). The effect of apricot extract was also studied on the bidirectional transport of talinolol, a specific P-gp substrate; inclusion of 1%, v/v, in the apical compartment of Caco-2 monolayers resulted in a significantly reduced polarity in the transport of talinolol (PF reference = 15.5; PF in the presence of apricot extract = 2.5). This study suggests that co-administration of fruit extracts might be a conceptually safe and useful strategy to enhance the intestinal absorption of P-gp substrates. More research is necessary to characterize the impact of this inhibition on P-gp-related efflux mechanisms in other absorption models (in-vitro and in-vivo) and to identify the compounds that are responsible for this inhibitory effect.
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Affiliation(s)
- Sven Deferme
- Laboratory for Pharmacotechnology and Biopharmacy, Gasthuisberg, Leuven, Belgium
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709
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Hugger ED, Audus KL, Borchardt RT. Effects of poly(ethylene glycol) on efflux transporter activity in Caco-2 cell monolayers. J Pharm Sci 2002; 91:1980-90. [PMID: 12210045 DOI: 10.1002/jps.10175] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Poly(ethylene glycol) (PEG) is an excipient commonly used in pharmaceutical formulations to increase the aqueous solubility of drugs intended for oral administration. High concentrations of PEG are often used to solubilize drug candidates for in vitro experiments in cell culture (e.g., Caco-2 cell permeability studies) and/or for in vivo pharmacokinetic and safety studies in animals. Although PEG is often deemed safe in these studies based on gross morphological studies, changes on a molecular level may be overlooked. The purpose of this study was to determine the possible effects of PEG on efflux transporter activity in Caco-2 cell monolayers, an in vitro model of the intestinal mucosa. In these studies, relatively high, yet clinically achievable, concentrations of PEG-300 did not significantly change the passive paracellular or transcellular permeation of model solutes across Caco-2 cell monolayers. More importantly, PEG-300 inhibited efflux transporter activity in Caco-2 cell monolayers, which is probably mediated by P-gp and/or MRP. Such PEG-induced inhibition of efflux transporter activity is most likely caused by changes in the microenvironment of the Caco-2 cell membranes, which perturbs the ability of these transporters to efflux substrates such as taxol and doxorubicin.
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Affiliation(s)
- Erin D Hugger
- Department of Pharmaceutical Chemistry, The University of Kansas, 2095 Constant Avenue, Lawrence, Kansas 66047, USA.
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710
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Boumendjel A, Di Pietro A, Dumontet C, Barron D. Recent advances in the discovery of flavonoids and analogs with high-affinity binding to P-glycoprotein responsible for cancer cell multidrug resistance. Med Res Rev 2002; 22:512-29. [PMID: 12210557 DOI: 10.1002/med.10015] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
P-glycoprotein (P-gp) is a plasma membrane glycoprotein that confers multidrug resistance on cells by virtue of its ability to exclude cytotoxic drugs in an ATP-dependent manner. The most commonly considered hypothesis is that P-gp acts as an ATP-driven drug-export pump, the mechanism of which is not understood in detail. Therefore, a tremendous effort is being made to find out modulator molecules to inhibit P-gp. We have been developing flavonoid derivatives as a new class of promising modulators using a new in vitro rational-screening assay based on measurements of the binding-affinity toward the C-terminal nucleotide-binding domain (NBD2) of P-gp. This review is focused on our results obtained with a variety of flavonoids. Structure-activity relationships of flavonoids as potential MDR modulators are reported.
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Affiliation(s)
- Ahcène Boumendjel
- Département de Pharmacochimie Moléculaire, UMR-CNRS 5063, UFR de Pharmacie de Grenoble, 38706 La Tronche, France.
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711
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Padua RA, McGlynn A, McGlynn H. Molecular, cytogenetic and genetic abnormalities in MDS and secondary AML. Cancer Treat Res 2002; 108:111-57. [PMID: 11702597 DOI: 10.1007/978-1-4615-1463-3_8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Myelodysplasia (MDS) is a clonal disease, which increases with age, suggesting that multiple steps are required for the evolution of the condition. Approximately 30% of MDS evolve into acute myelogenous leukemia (AML). In this review, we intend to delineate the genetic events, which may drive this sequence and therefore we will focus primarily on cytogenetic abnormalities where the genes have been identified and oncogenes and suppressor genes that have been implicated. In terms of the biological mechanisms, which characterise this process, it is generally thought that the MDS cell has impaired differentiation, and has increased apoptosis. As the disease progresses in addition, the cells have increased proliferation. As the disease evolves, the population of cells, which predominate remain immature, have decreased apoptosis and in many cases, upregulate anti-apoptotic genes and have deregulated proliferation as the number of blast cells increase. Etiological factors, which contribute to the development of leukemia, include therapeutic agents administered for a primary malignancy. The cytogenetic abnormalities, predisposition factors and genes involved in secondary leukemia will also be reviewed.
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MESH Headings
- Acute Disease
- Aneuploidy
- Apoptosis/genetics
- Biomarkers, Tumor
- Chromosome Aberrations
- Chromosome Deletion
- Chromosome Painting
- Chromosomes, Human/genetics
- Chromosomes, Human/ultrastructure
- Clone Cells/pathology
- Disease Progression
- Genes, Tumor Suppressor
- Genetic Predisposition to Disease
- Genetic Therapy
- Growth Substances/genetics
- Hematopoietic Stem Cells/pathology
- Humans
- Karyotyping
- Leukemia, Myeloid/etiology
- Leukemia, Myeloid/genetics
- Leukemia, Myeloid/pathology
- Multigene Family
- Myelodysplastic Syndromes/genetics
- Myelodysplastic Syndromes/pathology
- Myelodysplastic Syndromes/therapy
- Neoplasm Proteins/genetics
- Neoplastic Stem Cells/pathology
- Oncogenes
- Preleukemia/genetics
- Preleukemia/pathology
- Receptors, Growth Factor/genetics
- Signal Transduction/genetics
- Transcription, Genetic/genetics
- Translocation, Genetic
- Trisomy
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Affiliation(s)
- R A Padua
- Hematology Department, University of Wales College of Medicine, Cardiff, UK
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712
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Teodori E, Dei S, Scapecchi S, Gualtieri F. The medicinal chemistry of multidrug resistance (MDR) reversing drugs. FARMACO (SOCIETA CHIMICA ITALIANA : 1989) 2002; 57:385-415. [PMID: 12058813 DOI: 10.1016/s0014-827x(02)01229-6] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Multidrug resistance (MDR) is a kind of resistance of cancer cells to multiple classes of chemotherapic drugs that can be structurally and mechanistically unrelated. Classical MDR regards altered membrane transport that results in lower cell concentrations of cytotoxic drug and is related to the over expression of a variety of proteins that act as ATP-dependent extrusion pumps. P-glycoprotein (Pgp) and multidrug resistance protein (MRP1) are the most important and widely studied members of the family that belongs to the ABC superfamily of transporters. It is apparent that, besides their role in cancer cell resistance, these proteins have multiple physiological functions as well, since they are expressed also in many important non-tumoural tissues and are largely present in prokaryotic organisms. A number of drugs have been identified which are able to reverse the effects of Pgp, MRPI and sister proteins, on multidrug resistance. The first MDR modulators discovered and studied in clinical trials were endowed with definite pharmacological actions so that the doses required to overcome MDR were associated with unacceptably high side effects. As a consequence, much attention has been focused on developing more potent and selective modulators with proper potency, selectivity and pharmacokinetics that can be used at lower doses. Several novel MDR reversing agents (also known as chemosensitisers) are currently undergoing clinical evaluation for the treatment of resistant tumours. This review is concerned with the medicinal chemistry of MDR reversers, with particular attention to the drugs that are presently in development.
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Affiliation(s)
- E Teodori
- Dipartimento di Scienze Farmaceutiche, Universita' di Firenze, Florence, Italy
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713
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Riley RS, Massey D, Jackson-Cook C, Idowu M, Romagnoli G. Immunophenotypic analysis of acute lymphocytic leukemia. Hematol Oncol Clin North Am 2002; 16:245-99, v. [PMID: 12094473 DOI: 10.1016/s0889-8588(02)00004-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Acute lymphoblastic leukemia (ALL) is one of the most common hematologic malignancies. Flow cytometry is an integral part of ALL diagnosis and also provides significant patient prognostic information. This article is a practical review of the basic principles of the flow cytometric evaluation of acute leukemias, the interpretation of flow cytometric data, and the management of practical problems such as aberrant antigen, hematogones, bone marrow regeneration, and minimal residual disease.
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Affiliation(s)
- Roger S Riley
- Department of Pathology, Medical College of Virginia, Hospitals of Virginia Commonwealth University, 403 North 13th Street, Richmond, VA 23298-0250, USA.
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714
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Stouch TR, Gudmundsson O. Progress in understanding the structure-activity relationships of P-glycoprotein. Adv Drug Deliv Rev 2002; 54:315-28. [PMID: 11922950 DOI: 10.1016/s0169-409x(02)00006-6] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Efflux out of cells by P-glycoprotein (P-gp) represents a serious liability for pharmaceuticals, particularly for anti-cancer drugs. Consequently, identification of compounds as potential substrates is important for understanding their bioavailability. Also, the development of agents which reverse this multi-drug resistance phenotype has received considerable attention. Assays for determining these activities are reviewed. Recent literature and studies into the structure-activity relationships (SAR) of the resulting data are discussed. Multiple binding sites and other complicating factors have prevented the development of a truly general, conclusive SAR either for substrate or inhibitory activities. Consequently, many models have tended to address only very general properties, such as lipophilicity and size. However, progress has been made in the last few years toward more specific SAR suggesting well-defined structural features responsible for both activities. The future of understanding the details of P-gp SAR lies in more specific assays that target specific binding sites and mechanisms of action.
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Affiliation(s)
- Terry R Stouch
- P.O. Box 4000, Bristol-Myers Squibb, Princeton, NJ 08543, USA.
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715
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Bush JA, Li G. Cancer chemoresistance: the relationship between p53 and multidrug transporters. Int J Cancer 2002; 98:323-30. [PMID: 11920581 DOI: 10.1002/ijc.10226] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Extensive studies indicate that both p53 and multidrug transporters play important roles in chemoresistance. Since the initial reports a decade ago demonstrating a transcriptional dependence of the ABCB1 gene (MDR) promoter by p53, much data have been accumulated. However, despite being the subject of intense study, this p53-MDR relationship remains unclear in human cancers. The data are confounded by variable and contrasting results when considering the in vitro regulation and attempting to draw parallels in tissue specimens. The original model suggested that wild-type p53 downregulates the ABCB1 promoter, whereas mutant p53 increases expression of ABCB1. This review summarizes the data for and against this hypothesis. What emerges from these studies is a complex picture, where data have been obtained in support of this hypothesis, but there are also many circumstances where it is not supported. Taken together, these data suggest that the relationship between p53 and multidrug transporters is conditional. It is dependent on cellular environment, the drug used, and the nature of the p53 mutation.
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Affiliation(s)
- Jason A Bush
- Division of Dermatology, Department of Medicine, Vancouver Hospital and Health Sciences Centre, University of British Columbia, Vancouver, British Columbia, Canada
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716
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Poland J, Schadendorf D, Lage H, Schnölzer M, Celis JE, Sinha P. Study of therapy resistance in cancer cells with functional proteome analysis. Clin Chem Lab Med 2002; 40:221-34. [PMID: 12005211 DOI: 10.1515/cclm.2002.037] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Different types of cancer are naturally resistant to many anticancer drugs. Additionally, these tumours develop acquired drug resistance, which includes the classical multidrug resistance (MDR) accompanied by the synthesis of P-glycoprotein, a member of the superfamily of ATP-binding cassette (ABC) transporters. Furthermore, atypical MDR is mediated by several different, some unknown, mechanisms. To overcome chemoresistance problems, antineoplastic drugs are often combined with other modes of therapy, e.g. hyperthermia, where good response has been reported in several experimental tumour models and in advanced cancer patients. The success of this combined anticancer treatment may be limited by an increase in chemoresistance and thermoresistance. A model system to study resistance phenomena is the use of chemoresistant and thermoresistant cancer cell lines. We have established chemoresistant cancer cell lines (gastric and pancreatic carcinoma, fibrosarcoma, melanoma) and now thermoresistant cell lines derived from gastric and pancreatic carcinoma cells and their counterparts that were resistant towards daunorubicin (classical MDR) and mitoxantrone (atypical MDR). Using proteomics, in this paper we evaluate the drug resistance of chemoresistant melanoma cells (parental cell line MeWo and sublines exhibiting drug resistance towards etoposide, cisplatin, fotemustine and vindesine) as a paradigm for analysis of drug resistance phenomena. Additionally, we investigate heat resistance and the interaction of chemoresistance and thermoresistance to identify common pathways using the parental and drug resistant stomach cancer cell lines EPG85-257, EPG85-257RNOV, EPG85-257RDB and their thermoresistant counterparts. Possible implications of differential protein expression will be discussed.
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Affiliation(s)
- Julia Poland
- Institut für Laboratoriumsmedizin und Pathobiochemie, Universitätsklinikum Charité, Berlin, Germany
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717
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Ecker GF, Csaszar E, Kopp S, Plagens B, Holzer W, Ernst W, Chiba P. Identification of ligand-binding regions of P-glycoprotein by activated-pharmacophore photoaffinity labeling and matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry. Mol Pharmacol 2002; 61:637-48. [PMID: 11854445 DOI: 10.1124/mol.61.3.637] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Energy dependent efflux pumps confer resistance to anticancer, antimicrobial, and antiparasitic drugs. P-glycoprotein (Pgp, ABCB1) mediates resistance to a broad spectrum of antitumor drugs. Compounds that themselves are nontoxic to cells have been shown to act as inhibitors of Pgp. The mechanism of binding and transport of low-molecular-mass ligands by Pgp is still incompletely understood. This study introduces a series of propafenone-related photoaffinity ligands, which combine high specificity and selectivity for Pgp with high labeling efficiency. Molecules are intrinsically photoactivatable in the arylcarbonyl group, which represents a pharmacophoric substructure for this group of ligand molecules. A detailed study of the structure-activity relationship for this type of photoligand is presented. In subsequent experiments, these ligands were used to characterize the drug-binding domain of propafenone-type analogs. Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry shows that propafenone-type ligands preferentially label fragments assigned to putative transmembrane segments 3, 5, 6, 8, 10, 11, and 12. Labeled fragments are also identified in a highly charged region of 15 amino acids in the second cytoplasmic loop. This region corresponds to the so-called EAA-like motif, which has been proposed to play a role in the interaction between transmembrane domain and nucleotide binding domain of peroxisomal ATP-binding cassette transporters. In addition, a region in cytoplasmic loop 3 and between TM12 and the N terminus of the Walker A sequence of NBD2 are labeled by the ligands. Therefore, a number of confined protein regions contribute to the drug-binding domain of propafenone-type analogs.
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Affiliation(s)
- Gerhard F Ecker
- Institute of Pharmaceutical Chemistry, University of Vienna, Austria
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718
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Mayer LD, Lim KT, Hartley D. Identification of two distinct intracellular sites that contribute to the modulation of multidrug resistance in P388/ADR cells expressing P-glycoprotein. JOURNAL OF EXPERIMENTAL THERAPEUTICS AND ONCOLOGY 2002; 2:107-20. [PMID: 12415627 DOI: 10.1046/j.1359-4117.2002.1009x.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Although the ability of chemosensitizers to modulate P-glycoprotein (PGP)-based multidrug resistance (MDR) has been extensively studied, relatively little is known about the cellular pharmacology of the PGP inhibitors themselves in MDR cells. The studies described here have correlated the in vitro accumulation and retention properties of verapamil (VRP) in murine P388 (sensitive) and P388/ADR (MDR) cells with doxorubicin (DOX) uptake and cytotoxicity modulation characteristics in order to better understand VRP-tumor cell interactions that give rise to MDR modulation. VRP is rapidly taken up by DOX-sensitive and -resistant P388 cells where greater than 50% maximal VRP uptake occurs within 10 min of initial exposure at 37 degrees C. Whereas chemosensitization and DOX uptake in P388/ADR cells increase with increasing VRP concentration until a plateau is achieved at approximately 5 microM VRP, cellular modulator levels increase proportionally with increasing VPR concentrations beyond 20 microM. Subsequent to removal of noncell-associated modulator, VRP levels in both sensitive and resistant cells rapidly fall below 10% of those obtained at uptake equilibrium. However, a residual amount of VRP remains associated with the cells for extended time periods after the cells are washed. Pulse exposures of P388/ADR cells to high concentrations of VRP (50-100 microM) are capable of providing extended cell-associated VRP levels comparable to those obtained with continuous exposure at biologically active VRP concentrations (1-3 microM) and this leads to chemosensitization. These results are consistent with the existence of high- and low-affinity intracellular VRP pools in P388 MDR cells, both of which can contribute to the reversal of drug resistance. It is suggested that these properties should be taken into consideration during the design and evaluation of preclinical in vivo MDR models where pulsed exposure to high concentrations of resistance modulators often occurs. Special attention must be given to whether such high concentration pulses are desirable and/or achievable in relevant clinical settings.
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Affiliation(s)
- Lawrence D Mayer
- Department of Advanced Therapeutics, British Columbia Cancer Agency, 600 West 10th Ave. Vancouver, BC V5Z 4E6
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719
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Fu LW, Zhang YM, Liang YJ, Yang XP, Pan QC. The multidrug resistance of tumour cells was reversed by tetrandrine in vitro and in xenografts derived from human breast adenocarcinoma MCF-7/adr cells. Eur J Cancer 2002; 38:418-26. [PMID: 11818209 DOI: 10.1016/s0959-8049(01)00356-2] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Multidrug resistance (MDR) is one of the main obstacles limiting the efficacy of chemotherapy treatment of tumours. One of the main causes of MDR is linked to the overexpression of P-glycoprotein (P-gp). This study aimed to characterise tetrandrine (Tet), a potent inhibitor of P-gp mediated MDR. Cytotoxicity was determined by the tetrazolium (MTT) assay. A MCF-7/adr cell xenograft model was established to investigate the effect of Tet on reversing MDR in vivo. Mechanistic experiments were conducted to examine the uptake, efflux and accumulation of doxorubicin (Dox) and Fura-2, and to assess lipid membrane fluidity. Tet potentiated the cytotoxicity of Dox; a 20.4-fold reversal of resistance was achieved in the presence of 2.5 micromol/l of Tet. Accumulation and efflux studies with the P-gp substrates, Dox and Fura-2, demonstrated that Tet inhibited the P-gp-mediated drug efflux. In addition, Tet lowered cell membrane fluidity in a concentration-dependent manner. In mice bearing the MDR MCF-7/adr cell xenografts, coadministration of Tet potentiated the antitumour activity of doxorubicin without a significant increase in toxicity. Tet was an extremely potent MDR modulator both in vitro and in vivo, without apparently enhancing the toxicity of the co-administered drugs. Hence, Tet holds great promise as a MDR modulator for the treatment of P-gp-mediated MDR cancers.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/antagonists & inhibitors
- ATP Binding Cassette Transporter, Subfamily B, Member 1/drug effects
- Adenocarcinoma/drug therapy
- Alkaloids/therapeutic use
- Animals
- Antineoplastic Agents/therapeutic use
- Antineoplastic Agents, Phytogenic/therapeutic use
- Benzylisoquinolines
- Breast Neoplasms/drug therapy
- China
- Dose-Response Relationship, Drug
- Doxorubicin/therapeutic use
- Drug Resistance, Multiple
- Drug Resistance, Neoplasm
- Female
- Humans
- Mice
- Mice, Nude
- Neoplasm Transplantation
- Transplantation, Heterologous
- Tumor Cells, Cultured
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Affiliation(s)
- L W Fu
- Cancer Center, Sun Yat-Sen University of Medical Sciences, 510060, Guangzhou, China.
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720
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Fricker G, Miller DS. Relevance of multidrug resistance proteins for intestinal drug absorption in vitro and in vivo. PHARMACOLOGY & TOXICOLOGY 2002; 90:5-13. [PMID: 12005113 DOI: 10.1034/j.1600-0773.2002.900103.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Multidrug resistance proteins (p-glycoprotein and mrps) are becoming increasingly important to explain the pharmacokinetics and action of drugs. Located in epithelial and endothelial cells of the gastrointestinal tract, liver, kidney, blood brain barrier, choroid plexus and other organs, they are critical determinants for the movement of a large number of commonly prescribed drugs across cellular barriers. Here we provide a brief overview of the role of multidrug resistance proteins in drug absorption from the gastrointestinal tract. We address the different types of multidrug resistance proteins involved, describe experimental models to study the influence of these proteins on transcellular transport and discuss the impact of multidrug resistance proteins on overall drug bioavailability in vivo.
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Affiliation(s)
- Gert Fricker
- Institute for Pharmaceutics and Biopharmacy, University of Heidelberg, Germany.
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721
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Pariante CM, Makoff A, Lovestone S, Feroli S, Heyden A, Miller AH, Kerwin RW. Antidepressants enhance glucocorticoid receptor function in vitro by modulating the membrane steroid transporters. Br J Pharmacol 2001; 134:1335-43. [PMID: 11704655 PMCID: PMC1573058 DOI: 10.1038/sj.bjp.0704368] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Previous data demonstrate that the tricyclic antidepressant, desipramine, induces glucocorticoid receptor (GR) translocation from the cytoplasm to the nucleus in L929 cells and increases dexamethasone-induced GR-mediated gene transcription in L929 cells stably transfected with the mouse mammary tumour virus-chloramphenicol acetyltransferase (MMTV-CAT) reporter gene (LMCAT cells) (Pariante et al., 1997). 2. To extend these findings, the present study has investigated the effects of 24 h coincubation of LMCAT cells with dexamethasone and amitriptyline, clomipramine, paroxetine, citalopram or fluoxetine. 3. All antidepressants, except fluoxetine, enhanced GR-mediated gene transcription, with clomipramine having the greatest effect (10 fold increase). Twenty-four hours coincubation of cells with desipramine, clomipramine or paroxetine, also enhanced GR function in the presence of cortisol, but not of corticosterone. 4. It is proposed that these effects are due to the antidepressants inhibiting the L929 membrane steroid transporter, which actively extrudes dexamethasone and cortisol from the cell, but not corticosterone. This is further confirmed by the fact that clomipramine failed to enhance GR-mediated gene transcription in the presence of dexamethasone when the membrane steroid transporter was blocked by verapamil. 5. The membrane steroid transporters that regulate access of glucocorticoids to the brain in vivo, like the multiple drug resistance p-glycoprotein, could be a fundamental target for antidepressant action.
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Affiliation(s)
- C M Pariante
- Section of Clinical Neuropharmacology, Institute of Psychiatry, King's College London, London SE5 8AF.
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722
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723
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Sinha P, Poland J, Schnölzer M, Celis JE, Lage H. Characterization of the differential protein expression associated with thermoresistance in human gastric carcinoma cell lines. Electrophoresis 2001; 22:2990-3000. [PMID: 11565793 DOI: 10.1002/1522-2683(200108)22:14<2990::aid-elps2990>3.0.co;2-f] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Resistance to chemotherapeutic agents is one of the major problems faced during palliative therapy of tumor cells. Thus, chemotherapy is frequently combined with other modes of therapy such as radiation therapy and/or hyperthermia. Tumor cells respond to heat stress with development of thermotolerance and the interactions between chemo- and thermoresistance phenomena are not clearly understood. In this paper, we analyze the differential protein expression in vitro in human stomach cancer cells, their chemoresistant and thermoresistant counterparts using proteomics. The immediate aim was to identify sets of proteins that may lead to the development of thermoresistance. Based on these results, we aim to develop functional tests and methods for the modulation of thermoresistance and chemoresistance phenomena that may assist the therapy of inoperable cancers.
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MESH Headings
- ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism
- Blotting, Western
- Carcinoma/metabolism
- Carcinoma/pathology
- Drug Resistance, Neoplasm/genetics
- Electrophoresis, Gel, Two-Dimensional
- Gene Expression Profiling
- Gene Expression Regulation, Neoplastic
- Hot Temperature
- Humans
- Hyperthermia, Induced
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Neoplasm Proteins/physiology
- Proteome
- Silver Staining
- Stomach Neoplasms/metabolism
- Stomach Neoplasms/pathology
- Tumor Cells, Cultured/chemistry
- Tumor Cells, Cultured/drug effects
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Affiliation(s)
- P Sinha
- Institut für Laboratoriumsmedizin und Pathobiochemie, Universitätsklinikum Charité, Berlin, Germany.
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