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Warner W, Palombo M, Cruz R, Callaghan R, Shemesh N, Jones DK, Dell'Acqua F, Ianus A, Drobnjak I. Temporal Diffusion Ratio (TDR) for imaging restricted diffusion: Optimisation and pre-clinical demonstration. Neuroimage 2023; 269:119930. [PMID: 36750150 PMCID: PMC7615244 DOI: 10.1016/j.neuroimage.2023.119930] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 01/12/2023] [Accepted: 02/02/2023] [Indexed: 02/07/2023] Open
Abstract
Temporal Diffusion Ratio (TDR) is a recently proposed dMRI technique (Dell'Acqua et al., proc. ISMRM 2019) which provides contrast between areas with restricted diffusion and areas either without restricted diffusion or with length scales too small for characterisation. Hence, it has a potential for informing on pore sizes, in particular the presence of large axon diameters or other cellular structures. TDR employs the signal from two dMRI acquisitions obtained with the same, large, b-value but with different diffusion gradient waveforms. TDR is advantageous as it employs standard acquisition sequences, does not make any assumptions on the underlying tissue structure and does not require any model fitting, avoiding issues related to model degeneracy. This work for the first time introduces and optimises the TDR method in simulation for a range of different tissues and scanner constraints and validates it in a pre-clinical demonstration. We consider both substrates containing cylinders and spherical structures, representing cell soma in tissue. Our results show that contrasting an acquisition with short gradient duration, short diffusion time and high gradient strength with an acquisition with long gradient duration, long diffusion time and low gradient strength, maximises the TDR contrast for a wide range of pore configurations. Additionally, in the presence of Rician noise, computing TDR from a subset (50% or fewer) of the acquired diffusion gradients rather than the entire shell as proposed originally further improves the contrast. In the last part of the work the results are demonstrated experimentally on rat spinal cord. In line with simulations, the experimental data shows that optimised TDR improves the contrast compared to non-optimised TDR. Furthermore, we find a strong correlation between TDR and histology measurements of axon diameter. In conclusion, we find that TDR has great potential and is a very promising alternative (or potentially complement) to model-based approaches for informing on pore sizes and restricted diffusion in general.
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Affiliation(s)
- William Warner
- Centre for Medical Image Computing (CMIC), Computer Science Department, University College London, United Kingdom
| | - Marco Palombo
- Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, United Kingdom; School of Computer Science and Informatics, Cardiff University, Cardiff, United Kingdom
| | - Renata Cruz
- Champalimaud Research, Champalimaud Foundation, Lisbon, Portugal
| | | | - Noam Shemesh
- Champalimaud Research, Champalimaud Foundation, Lisbon, Portugal
| | - Derek K Jones
- Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, United Kingdom
| | - Flavio Dell'Acqua
- NatBrainLab, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
| | - Andrada Ianus
- Champalimaud Research, Champalimaud Foundation, Lisbon, Portugal.
| | - Ivana Drobnjak
- Centre for Medical Image Computing (CMIC), Computer Science Department, University College London, United Kingdom.
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Kerkelä L, Nery F, Callaghan R, Zhou F, Gyori NG, Szczepankiewicz F, Palombo M, Parker GJM, Zhang H, Hall MG, Clark CA. Comparative analysis of signal models for microscopic fractional anisotropy estimation using q-space trajectory encoding. Neuroimage 2021; 242:118445. [PMID: 34375753 DOI: 10.1016/j.neuroimage.2021.118445] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 07/06/2021] [Accepted: 08/02/2021] [Indexed: 12/12/2022] Open
Abstract
Microscopic diffusion anisotropy imaging using diffusion-weighted MRI and multidimensional diffusion encoding is a promising method for quantifying clinically and scientifically relevant microstructural properties of neural tissue. Several methods for estimating microscopic fractional anisotropy (µFA), a normalized measure of microscopic diffusion anisotropy, have been introduced but the differences between the methods have received little attention thus far. In this study, the accuracy and precision of µFA estimation using q-space trajectory encoding and different signal models were assessed using imaging experiments and simulations. Three healthy volunteers and a microfibre phantom were imaged with five non-zero b-values and gradient waveforms encoding linear and spherical b-tensors. Since the ground-truth µFA was unknown in the imaging experiments, Monte Carlo random walk simulations were performed using axon-mimicking fibres for which the ground truth was known. Furthermore, parameter bias due to time-dependent diffusion was quantified by repeating the simulations with tuned waveforms, which have similar power spectra, and with triple diffusion encoding, which, unlike q-space trajectory encoding, is not based on the assumption of time-independent diffusion. The truncated cumulant expansion of the powder-averaged signal, gamma-distributed diffusivities assumption, and q-space trajectory imaging, a generalization of the truncated cumulant expansion to individual signals, were used to estimate µFA. The gamma-distributed diffusivities assumption consistently resulted in greater µFA values than the second order cumulant expansion, 0.1 greater when averaged over the whole brain. In the simulations, the generalized cumulant expansion provided the most accurate estimates. Importantly, although time-dependent diffusion caused significant overestimation of µFA using all the studied methods, the simulations suggest that the resulting bias in µFA is less than 0.1 in human white matter.
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Affiliation(s)
- Leevi Kerkelä
- UCL Great Ormond Street Institute of Child Health, University College London, London, UK.
| | - Fabio Nery
- UCL Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Ross Callaghan
- UCL Centre for Medical Image Computing, University College London, London, UK
| | - Fenglei Zhou
- UCL Centre for Medical Image Computing, University College London, London, UK; UCL School of Pharmacy, University College London, London, UK
| | - Noemi G Gyori
- UCL Centre for Medical Image Computing, University College London, London, UK; UCL Great Ormond Street Institute of Child Health, University College London, London, UK
| | - Filip Szczepankiewicz
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, US; Harvard Medical School, Boston, Massachusetts, US; Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Marco Palombo
- UCL Centre for Medical Image Computing, University College London, London, UK
| | - Geoff J M Parker
- UCL Centre for Medical Image Computing, University College London, London, UK; Bioxydyn Limited, Manchester, UK; UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Hui Zhang
- UCL Centre for Medical Image Computing, University College London, London, UK
| | - Matt G Hall
- UCL Great Ormond Street Institute of Child Health, University College London, London, UK; National Physical Laboratory, Teddington, UK
| | - Chris A Clark
- UCL Great Ormond Street Institute of Child Health, University College London, London, UK
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Callaghan R, Alexander DC, Zhang H, Palombo M. Contextual Fibre Growth to Generate Realistic Axonal Packing for Diffusion MRI Simulation. ACTA ACUST UNITED AC 2019. [DOI: 10.1007/978-3-030-20351-1_33] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
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Gatley JM, Sanches M, Callaghan R. Impacts of Canadian drinking age laws on sexual assault victimization of young women, 2009-2013. Eur J Public Health 2016. [DOI: 10.1093/eurpub/ckw167.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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5
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Roselló-Sastre E, Cerdá-Nicolás M, Callaghan R, Barcia JL, Llombart-Bosch A. Prognostic Significance of Histologic and Cytometric Factors in Supratentorial Astrocytomas. Int J Surg Pathol 2016. [DOI: 10.1177/106689699900700403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
There is no agreement in the literature on selecting the principal parameters that contribute to explain the different outcomes in supratentorial astrocytomas. Hence, we designed a global study using morphologic parameters and DNA quantification measured by flow cytometry (FCM) and image analysis (IA) on 116 tumors contrasting the results with patients' survival in a univariate and multivariate study. In the Kaplan-Meier study besides the necrosis (p<0.0001) there were other parameters with significant prognostic value such as nuclear atypia (p=0.0001), presence of anaplastic large cells (p=0.0003) and the morphology of the tumor vessels (p=0.009). Proliferative parameters like mitotic index, cell density, the cell fraction in S phase or G2/M phase, and the proliferative phase measured by image analysis (IA) or ploidy patterns did not influence the prognosis. In the Cox's proportional hazards model the presence of necrosis remained as the only prognostic predictor (p=0.001) and increased 5.9 times the risk of mortality in gliomas.
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Affiliation(s)
- E. Roselló-Sastre
- University Hospital Dr Peset, Valencia, Spain; Servicio de Anatomia Patologica, Hospital Dr Peset, Avda Gaspar Aguilar, 90, 46017-Valencia, Espana
| | | | - R. Callaghan
- Department of Pathology, Medical School of Valencia, Spain
| | - J. L. Barcia
- Department of Neurosurgery, Medical School of Valencia, Spain
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Stephen-Haynes J, Callaghan R, Wibaux A, Johnson P, Carty N. Clinical evaluation of a thin absorbent skin adhesive dressing for wound management. J Wound Care 2014; 23:532, 534, 536 passim. [DOI: 10.12968/jowc.2014.23.11.532] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- J. Stephen-Haynes
- Professional Development Unit, Birmingham City University
- Worcestershire Health and Care NHS Trust
| | | | - A. Wibaux
- Vancive Medical Technologies, an Avery Dennison business 20 N. Wacker Dr, Suite 2240, Chicago, IL 60606 USA
| | - P. Johnson
- Vancive Medical Technologies, an Avery Dennison business 20 N. Wacker Dr, Suite 2240, Chicago, IL 60606 USA
| | - N. Carty
- Vancive Medical Technologies, an Avery Dennison business 20 N. Wacker Dr, Suite 2240, Chicago, IL 60606 USA
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Chowdhury O, Woll P, Leonard J, Anderson K, Mizukami T, Mead A, Hellstrom-Lindberg E, Nilsson L, Callaghan R, Jacobsen S. 380 Characterisation and targeting of malignant stem cells in myelodysplastic syndromes. Leuk Res 2011. [DOI: 10.1016/s0145-2126(11)70382-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Modok S, Scott R, Alderden RA, Hall MD, Mellor HR, Bohic S, Roose T, Hambley TW, Callaghan R. Transport kinetics of four- and six-coordinate platinum compounds in the multicell layer tumour model. Br J Cancer 2007; 97:194-200. [PMID: 17579620 PMCID: PMC2360296 DOI: 10.1038/sj.bjc.6603854] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Four-coordinate (Pt(II)) platinum-based anticancer drugs are widely used in primary or palliative chemotherapy and produce considerable efficacy in certain clinical applications, for example testicular cancer. However, in many cancers the Pt(II) drugs are beset by poor efficacy mainly due to suboptimal pharmacokinetic properties. Consequently, the six-coordinate (Pt(IV)) class of Pt drugs were developed to improve platinum efficacy by (i) increasing stability, (ii) reducing reactivity, (iii) increasing lipophilicity, and (iv) nuclear targeting. However, comparatively little information is available on the pharmacokinetic properties of these compounds within solid tumour tissue. In the present study, the distribution and fluxes of [(14)C]-labelled [PtCl(2)(en)] (where en stands for ethane-1,2-diamine) and cis,trans-[PtCl(2)(OH)(2)(en)] drugs were determined in the multicell layer (MCL) tumour model comprising colon cancer cells. Flux data were analysed by mathematical modelling of drug diffusion and cellular uptake in the transport system. The flux of the Pt(IV) compound through the MCL was not significantly different to that of the Pt(II) drug nor were the diffusion coefficient or tissue uptake; the latter confirmed with elemental imaging analysis by synchrotron radiation induced X-ray emission. However, the flux of the Pt(IV) through the MCL was increased by hydrostatic pressure, thereby demonstrating the potential to target cancer cells further away from the vessels with six-coordinate platinum drugs.
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Affiliation(s)
- S Modok
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, University of Oxford, Level 4, The John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - R Scott
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, University of Oxford, Level 4, The John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - R A Alderden
- Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | - M D Hall
- Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | - H R Mellor
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, University of Oxford, Level 4, The John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - S Bohic
- ESRF, Micro-Fluorescence/Imaging/Diffraction – ID22, 6, rue Jules Horowitz, BP 220, F-38043 Grenoble Cedex, France
| | - T Roose
- Oxford Centre for Industrial and Applied Mathematics and Centre for Mathematical Biology, Mathematical Institute, University of Oxford, 24-29 St Giles', Oxford OX1 3LB, UK
| | - T W Hambley
- Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | - R Callaghan
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, University of Oxford, Level 4, The John Radcliffe Hospital, Oxford OX3 9DU, UK
- E-mail:
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Callaghan R, Prabu A, Allan RB, Clarke AE, Sutcliffe N, Pierre YS, Gordon C, Bowman SJ. Direct healthcare costs and predictors of costs in patients with primary Sjogren's syndrome. Rheumatology (Oxford) 2007; 46:105-11. [PMID: 16728437 DOI: 10.1093/rheumatology/kel155] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES To analyse the healthcare usage, direct healthcare costs and predictors of cost in primary Sjögren's syndrome (PSS) in the UK and to compare the findings with the data from healthy control groups and rheumatoid arthritis (RA) patients. METHODS A total of 129 patients with PSS (American-European criteria), 91 with RA and 92 controls, were included in the study. All groups were age-matched females and all completed questionnaires on health status (SF-36) and healthcare utilization (economic component of the Stanford Health Assessment Questionnaire). Annual direct healthcare costs were calculated (and expressed in 2004 UK pound sterling) and predictors of costs for each patient group were determined by regression analyses. Age, health status, disease duration and anti-Ro/La antibody positivity were used as potential predictor variables. RESULTS Mean age was similar in the PSS (59.2 yrs, S.D. 11.6), RA (60.3 yrs, S.D. 10.5) and control groups (57.7 yrs, S.D. 12.5). The mean disease duration was 5.4 yrs (S.D. 4.8) in the PSS group and 13.4 yrs (S.D. 11.4) in the RA group. The mean annual total direct cost per patient [95% confidence interval (CI)] was 2188 pounds sterling (1831 and 2546 pounds sterling) in the PSS group, 2693 pounds sterling(2069 and 3428 pounds sterling) in the RA group and 949 pounds sterling (741 and 1156 pounds sterling) in the control group. The costs in the PSS group were greater than for the RA and control groups for visits to all healthcare professionals (total) as well as visits to the dentist, dental hospital and ophthalmologist. The costs in the PSS and RA groups were higher than in controls for diagnostic tests and visits to hospital and the accident and emergency (A&E) department. The PSS group also incurred higher costs than controls, but lower costs than the RA group, for visits to a rheumatologist, urine and blood tests, assistive devices and drug therapy. Regression analysis identified the SF-36 physical function subscale as the best predictor of costs in PSS patients as well as controls and the mental health subscale in RA patients. CONCLUSION This is the first study to evaluate direct healthcare costs in patients with PSS. PSS has a significant impact on the healthcare system, similar to that of RA, by more than doubling costs compared with control patients.
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Affiliation(s)
- R Callaghan
- Rheumatology Department, Division of Immunity and Infection, The University of Birmingham, UK.
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10
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Abstract
BACKGROUND & PURPOSE Drug-resistant cancer cells frequently display efflux pumps such as P-glycoprotein (P-gp), the multidrug resistance associated protein (MRP1) or the transporter ABCG2. These transporters are each capable of mediating the active efflux of numerous anticancer drugs and display relatively distinct substrate preferences. The last, most recently discovered member, ABCG2, plays a major role in resistance in several types of cancer and the precise pharmacology of this multidrug transporter remain unresolved as does the nature of substrate binding. EXPERIMENTAL APPROACH Plasma membranes from insect cells expressing ABCG2 were used to characterise binding of [3H]daunomycin to the multidrug transporter. The kinetics of association and dissociation for this substrate and several other compounds were also determined in this experimental system. KEY RESULTS The dissociation constant for [3H]daunomycin binding was 564 +/- 57 nM and a Hill slope of 1.4 suggested cooperative binding. Doxorubicin, prazosin and daunomycin completely displaced the binding of radioligand, while mitoxantrone and Hoechst 33342 produced only a partial displacement. Analysis of the dissociation rates revealed that [3H]daunomycin and doxorubicin bind to multiple sites on the transporter. CONCLUSIONS Both kinetic and equilibrium data support the presence of at least two symmetric drug binding sites on ABCG2, which is distinct from the asymmetry observed for P-gp. The data provide the first molecular details underlying the mechanism by which this transporter is capable of interacting with multiple substrates.
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Affiliation(s)
- R Clark
- Nuffield Department of Clinical Laboratory Sciences, University of OxfordUK
| | - I D Kerr
- Centre for Biochemistry and Cell Biology, School of Biomedical Sciences, University of NottinghamUK
| | - R Callaghan
- Nuffield Department of Clinical Laboratory Sciences, University of OxfordUK
- Author for correspondence:
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Ejtehadi HD, Freimanis GL, Ali HA, Bowman S, Alavi A, Axford J, Callaghan R, Nelson PN. The potential role of human endogenous retrovirus K10 in the pathogenesis of rheumatoid arthritis: a preliminary study. Ann Rheum Dis 2006; 65:612-6. [PMID: 16192292 PMCID: PMC1798125 DOI: 10.1136/ard.2004.031146] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2005] [Indexed: 11/03/2022]
Abstract
OBJECTIVE To examine whether human endogenous retrovirus K10 is associated with autoimmune rheumatic disease. DESIGN A novel multiplex reverse transcription polymerase chain reaction (RT-PCR) system was developed to investigate HERV-K10 mRNA expression in patients with rheumatoid arthritis. METHODS 40 patients with rheumatoid arthritis, 17 with osteoarthritis, and 27 healthy individuals were recruited and total RNA was extracted from peripheral blood mononuclear cells (PBMCs) and analysed using multiplex RT-PCR for the level of HERV-K10 gag mRNA expression. Southern blot and DNA sequencing confirmed the authenticity of the PCR products. RESULTS Using the histidyl tRNA synthetase (HtRNAS) gene as a housekeeping gene in the optimised multiplex RT-PCR, a significantly higher level of HERV-K10 gag mRNA expression was found in rheumatoid arthritis than in osteoarthritis (p = 0.01) or in the healthy controls (p = 0.02). CONCLUSION There is enhanced mRNA expression of the HERV-K10 gag region in rheumatoid arthritis compared with osteoarthritis or healthy controls. This could contribute to the pathogenesis of rheumatoid arthritis.
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Affiliation(s)
- H D Ejtehadi
- Molecular Immunology Research Group, Research Institute in Healthcare Sciences, University of Wolverhampton, Wulfruna Street, Wolverhampton WV1 1SB, UK.
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Alderden RA, Mellor HR, Modok S, Hambley TW, Callaghan R. Cytotoxic efficacy of an anthraquinone linked platinum anticancer drug. Biochem Pharmacol 2006; 71:1136-45. [PMID: 16458859 DOI: 10.1016/j.bcp.2005.12.039] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 12/19/2005] [Accepted: 12/20/2005] [Indexed: 11/28/2022]
Abstract
Platinum complexes are widely used in cancer chemotherapy; however, they are associated with toxicity, high "non-specific" reactivity and relatively poor pharmacokinetic profiles. In particular, their low cellular uptake and rapid metabolic inactivation means that the amount of "active" drug reaching the nuclear compartment is low. Our strategy to facilitate nuclear accumulation was to introduce a hydrophobic anthraquinone (1C3) moiety to the Pt-complex. Anthraquinones are known to readily intercalate into DNA strands and hence, the Pt-1C3 complex may represent an effective system for the delivery of the platinum moiety to nuclear DNA. Efficacy of the complex was determined by measuring the extent and potency of cytotoxicity in comparison to cisplatin and an anthraquinone based anticancer drug, doxorubicin. The Pt-1C3 complex generated higher levels of cytotoxicity than cisplatin, with a potency of 19 +/- 4 microM in the DLD-1 cancer cell line. However, this potency was not significantly different to that of the 1C3 moiety alone. To examine the reason for the apparent lack of platinum related cytotoxicity, the cellular distribution was characterised. Confocal fluorescence microscopy indicated that the Pt-1C3 complex was rapidly sequestered into lysosomes, in contrast to the nuclear localisation of doxorubicin. In addition, there was negligible DNA associated Pt following administration of the novel complex. Thus, the addition of a 1C3 moiety generated sequestration of the complex to lysosomes, thereby preventing localisation to the nucleus.
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Affiliation(s)
- R A Alderden
- Centre for Heavy Metals Research, School of Chemistry, The University of Sydney, NSW, Australia
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Mellor HR, Davies LA, Caspar H, Pringle CR, Hyde SC, Gill DR, Callaghan R. Optimising non-viral gene delivery in a tumour spheroid model. J Gene Med 2006; 8:1160-70. [PMID: 16807955 DOI: 10.1002/jgm.947] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Our current understanding of how the unique tumour microenvironment influences the efficacy of gene delivery is limited. The current investigation systematically examines the efficiency of several non-viral gene transfer agents to transfect multicellular tumour spheroids (MCTS), an in vitro model that displays a faithful three-dimensional (3D) representation of solid tumour tissue. METHODS Using a luciferase reporter assay, gene transfer to MCTS was optimised for 22 kDa linear and 25 kDa branched polyethyleneimine (PEI), the cationic lipids Lipofectamine(trade mark) and DCChol : DOPE, and the physical approach of tissue electroporation. Confocal microscopy was used to take optical tissue slices to identify the tissue localisation of green fluorescent protein (GFP) reporter gene expression and the distribution of fluorescently labelled complexes. A MCTS model of quiescent tumour regions was used to establish the influence of cellular proliferation status on gene transfer efficiency. RESULTS Of the polyplexes tested, 22 kDa linear PEI provided optimal gene delivery, with gene expression peaking at 46 h. Despite being the optimal vector tested, PEI-mediated transfection was limited to cells at the MCTS periphery. Using fluorescent PEI, it was found that complexes could only penetrate the outer 3-5 proliferating cell layers of the MCTS, sparing the deeper quiescent cells. Gene delivery in an MCTS model comprised entirely of quiescent cells demonstrated that in addition to being inaccessible to the vector, quiescent tumour regions are inherently less susceptible to PEI-mediated transfection than proliferating regions. This 'resistance' to transfection observed in quiescent cells was overcome through the use of electroporation. Despite the improved efficacy of electroporation in quiescent tissue, the gene expression was still confined to the outer regions of MCTS. The results suggest that limited access to central regions of an MCTS remain a significant barrier to gene delivery. CONCLUSIONS This data provides new insights into tumour-specific factors affecting non-viral gene transfer and highlights the difficulties in delivering genes to avascular tumour regions. The MCTS model is a useful system for the initial screening of future gene therapy strategies for solid tumours.
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Affiliation(s)
- H R Mellor
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK
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Mellor HR, Snelling S, Hall MD, Modok S, Jaffar M, Hambley TW, Callaghan R. The influence of tumour microenvironmental factors on the efficacy of cisplatin and novel platinum(IV) complexes. Biochem Pharmacol 2005; 70:1137-46. [PMID: 16139250 DOI: 10.1016/j.bcp.2005.07.016] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 07/15/2005] [Accepted: 07/20/2005] [Indexed: 11/26/2022]
Abstract
The chemotherapeutic drug cisplatin is an important treatment for many types of solid tumours, in particular non-small cell lung cancer (NSCLC). Platinum(IV) complexes offer several advantages to cisplatin due to their requirement for reduction to the active platinum(II) form to elicit cytotoxicity. This should minimise non-specific effects and facilitate higher amounts of the active complexes reaching the target DNA. Hypoxia and a quiescent cell population are features of the tumour microenvironment known to lead to resistance to many chemotherapeutic agents. It is unclear how these microenvironmental factors will impact on the efficacy of novel platinum(IV) complexes. Consequently, the cytotoxicities of several platinum drugs were determined in monolayer and tumour spheroid cultures derived from NSCLC lines. Platinum(IV) reduction potential correlated well with cytotoxicity. The complex containing a chloro axial ligand demonstrated the greatest potency and the drug with the hydroxy ligand was the least effective. Although drug cytotoxicity was not enhanced under hypoxic conditions, both cisplatin and the platinum(IV) complexes retained full potency. In addition, all of the platinum drugs retained the ability to evoke apoptosis in quiescent cells. In summary, unlike many anticancer drugs, the platinum(IV) complexes retain cytotoxic potency under resistance-inducing tumour microenvironmental conditions and warrant further investigation as more selective alternatives to current platinum-based therapy for the treatment of solid tumours.
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Affiliation(s)
- H R Mellor
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, UK
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15
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Abstract
The quiescent cell population of tumours poses a barrier to the success of many cancer therapies. Most chemotherapeutic drugs target proliferating cells, but the growth fraction of many tumours is low. Based on the multicellular tumour spheroid model, a system was developed using human colon adenocarcinoma (DLD-1) cells to mimic the microenvironment of quiescent microregions of solid tumours. The quiescent tumour spheroids (TS(Q)) showed decreased expression of the proliferation marker Ki-67 and increased expression of the quiescence marker p27(kip1) compared to proliferating spheroids (TS(P)). The quiescent status of the TS(Q) was confirmed by long-term growth assessment. The quiescence was completely reversible demonstrating that the TS(Q) retained the ability to proliferate and morphological assessment by light microscopy confirmed the absence of significant apoptosis. When the efficacy of widely used chemotherapeutic drugs was determined, vinblastine, doxorubicin, cisplatin and 5-fluorouracil (5-FU) all produced significant cell death in the TS(P). However, while still effective, the potencies of doxorubicin and cisplatin were significantly reduced in TS(Q). In contrast, 5-FU and vinblastine did not produce cell death in the TS(Q). In summary, TS(Q) show considerable resistance to a panel of established chemotherapeutic agents and represent a useful model for evaluating the efficacy of drugs and other cancer therapies in quiescent tumours.
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Affiliation(s)
- H R Mellor
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK
| | - D J P Ferguson
- Ultrastructural Morphology Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK
| | - R Callaghan
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK
- Oxford Drug Resistance Group, Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DU, UK. E-mail:
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Lopez-Gines C, Cerda-Nicolas M, Gil-Benso R, Pellin A, Lopez-Guerrero JA, Callaghan R, Benito R, Roldan P, Piquer J, Llacer J, Barbera J. Association of chromosome 7, chromosome 10 and EGFR gene amplification in glioblastoma multiforme. Clin Neuropathol 2005; 24:209-18. [PMID: 16167544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023] Open
Abstract
Glioblastoma multiforme (GBM) is characterized by intratumoral heterogeneity in both histomorphological and genetic changes, displaying a wide variety of numerical chromosome aberrations, the most common of which are trisomy 7 and monosomy 10. The amplification of the epidermal growth factor receptor (EGFR) gene is the most frequently reported genetic abnormality. The associations between these parameters and their implication in the tumoral progression are poorly understood. We performed simultaneous fluorescence in situ hybridization (FISH) with centromeric DNA probes for chromosomes 7 and 10 in smear preparations, and EGFR gene amplification by PCR from 25 cases of GBM. Trisomy/ polysomy for chromosome 7 was present in 76% of cases and monosomy 10 in 68%. Both alterations were associated in 56% of cases. The EGFR gene was amplified in 52% of tumors; in 44% associated with trisomy/ polysomy 7, and in 36% with monosomy 10. The three parameters were associated together in 28% of cases. Kaplan-Meier survival rate analysis demonstrated lower survival rates in patients with monosomy 10, trisomy 7, and monosomy associated with trisomy 7. The other combinations were not different in frequency in relation to survival. In the present study, trisomy/polysomy 7 and monosomy 10 have been found to be frequently associated. The combination of both anomalies is probably important in the tumorigenesis of glioblastoma. Moreover, this association is apparently independent of EGFR gene amplification, which could be a later event in this process.
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Affiliation(s)
- C Lopez-Gines
- Department of Pathology, Medical School, University of Valencia, Spain.
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17
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Price-Forbes AN, Callaghan R, Allen ME, Rowe IF. A regional audit of the use of COX-2 selective non-steroidal anti-inflammatory drugs (NSAIDs) in rheumatology clinics in the West Midlands, in relation to NICE guidelines. Rheumatology (Oxford) 2005; 44:921-4. [PMID: 15827035 DOI: 10.1093/rheumatology/keh642] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES Whilst all non-steroidal anti-inflammatory drugs (NSAIDs) can cause adverse gastrointestinal events, COX-2-selective inhibitors (COX-2) may have improved gastrointestinal safety compared with non-selective NSAIDs (NSNSAIDs). In 2001, the National Institute for Clinical Excellence (NICE) published guidance on the use of the COX-2 agents celecoxib, rofecoxib, meloxicam and etodolac for rheumatoid arthritis (RA) and osteoarthritis (OA). This study aimed to audit the appropriateness of NSAID use in relation to NICE guidance in rheumatology out-patients. METHODS Questionnaires were completed for all patients attending clinics in 18 rheumatology units in the West Midlands over a 2-week period. Data collected included patient demographics, NSAID type, indications, duration of use (> or =3 months was considered prolonged), and concomitant prescription of corticosteroids, warfarin and gastroprotective agents. RESULTS Data were collected on 2846 patients; 1164 (41%) were taking NSAIDs (791 NSNSAIDs, 373 COX-2). Of the 1164 NSAID users, 753 (65%) had a diagnosis of RA or OA (483 NSNSAIDs, 270 COX-2). Overall, 37% of NSAID prescriptions were appropriate. Of the NSNSAID users, 92% had at least one risk factor for adverse gastrointestinal events and were therefore inappropriately treated. Prolonged use (in 89%) and age > or =65 yr (in 23%) were the most frequent risk factors identified. Of the COX-2 users, 97% had one or more risk factors and were appropriately treated. Analysis of the RA/OA subgroup revealed similar findings. Thirty-six per cent were taking NSAIDs appropriately; 97% of NSNSAID use was inappropriate and 97% of COX-2 use was appropriate treatment. In the whole cohort, gastroprotective agents were used in 26% of NSNSAID users, 56% of gastroprotective agents being proton pump inhibitors. CONCLUSIONS Ninety-two per cent of patients attending rheumatology clinics who were taking NSNSAIDs should have been prescribed a COX-2-selective agent in relation to NICE guidance. Duration of use and age > or =65 yr emerged numerically as the most important risk factors. Significant numbers of patients taking NSNSAIDs may be at risk from adverse gastrointestinal events and clinicians may wish to review their prescribing patterns. Conversely, 97% of patients taking COX-2 agents were treated appropriately. Although practice overall conformed poorly with NICE guidance, NSAID prescribing also needs to be considered in the context of recent concerns regarding the cardiovascular risks of COX-2 agents.
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Affiliation(s)
- A N Price-Forbes
- Department of Rheumatology, Highfield Unit, Worcestershire Royal Hospital NHS Trust, Charles Hastings Way, Worcester WR5 1DD, UK
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18
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Walker J, Martin C, Callaghan R. Inhibition of P-glycoprotein function by XR9576 in a solid tumour model can restore anticancer drug efficacy. Eur J Cancer 2004; 40:594-605. [PMID: 14962729 DOI: 10.1016/j.ejca.2003.09.036] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2003] [Revised: 09/18/2003] [Accepted: 09/18/2003] [Indexed: 11/22/2022]
Abstract
Resistance to cancer chemotherapy involves both altered drug activity at the designated target and modified intra-tumour pharmacokinetic properties (e.g. uptake, metabolism). The membrane transporter P-glycoprotein (P-gp) plays a major role in pharmacokinetic resistance by preventing sufficient intracellular accumulation of several anticancer agents. Whilst inhibiting P-gp has great potential to restore chemotherapeutic effectiveness in blood-borne cancers, the situation in solid tumours is less clear. Therefore, the degree of resistance tumours pose to the cytotoxicity of vinblastine and doxorubicin was characterised using the multicellular tumour spheroid model. Tumour spheroids were generated from either drug-sensitive MCF7(WT) breast cancer cells or a resistant P-gp-expressing variant (NCI/ADR(Res)). Drug-induced cytotoxicity in tumour spheroids was measured using an outgrowth assay and compared with that observed in monolayer cultures. As anticipated, the 3-D organisation of MCF7(WT) in tumour spheroids was associated with a reduction in the potency of doxorubicin and vinblastine-i.e. the inherent multicellular resistance phenomenon. In contrast, tumour spheroids from NCI/ADR(Res) cells did not display multicellular resistance. However their constitutive expression of P-gp reduced the potency of both anticancer drugs. Moreover, the highly potent P-gp inhibitor, the anthranilic acid derivative, XR9576, was able to restore the cytotoxic efficacy of both drugs in tumour spheroids comprising NCI/ADR(Res) cells. The results suggest that inhibition of P-gp in solid tumours is achievable and that generation of potent inhibitors will provide a significant benefit towards restoration of chemotherapy in solid tissues.
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Affiliation(s)
- J Walker
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 8PA, UK
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19
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Abstract
BACKGROUND Autopsy studies suggest that Wernicke-Korsakoff Syndrome (WKS) is not a rare disorder, particularly in individuals who abuse alcohol. Thiamine has been established as the treatment of choice for over 50 years, but there is uncertainty about appropriate dosage and duration. Current practice guidelines are based on case reports and clinical experience. OBJECTIVES To determine the quality of evidence for the efficacy of thiamine in preventing and treating the manifestations of WKS as a consequence of alcohol excess, and if so in which form it should be given, at what dose and for how long. SEARCH STRATEGY Trials were identified from the latest updated search of the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group on 3 February 2003 using the terms "(thiamin* or aneurin*) and (Korsakoff* or Wernicke* or alcohol*). The CDCIG Specialized register contains up-to-date records from all major health care databases (Medline, Embase, PsycInfo, Cinahl and others) as well as from many trials databases. SELECTION CRITERIA All randomized trials in which treatment with thiamine or thiamine-containing products was administered and compared with alternative interventions for people with, or at risk of developing, WKS secondary to alcohol abuse. DATA COLLECTION AND ANALYSIS All abstracts were independently inspected by two reviewers (ED & PB) and relevant papers were retrieved and assessed for methodological quality using Cochrane Reviewers' Handbook criteria. MAIN RESULTS Two studies were identified that met the inclusion criteria, but only one contained sufficient data for quantitative analysis. Ambrose (2001) randomized participants (n=107) to one of five doses of intramuscular thiamine and measured outcomes after 2 days of treatment. We compared the lowest dose (5mg/day) with each of the other four doses. There was a significant difference in favour of the 200mg/day compared with the 5 mg/day dose in the number of trials taken to reach criterion on a delayed alternation test (MD -17.90, 95% CI -35.4 to -0.40, p=0.04). No significant differences emerged in comparing the other doses with 5 mg/day. The pattern of results did not present a simple dose-response relationship. The study had methodological shortcomings in design and the presentation of results that limited further analysis. REVIEWER'S CONCLUSIONS There is insufficient evidence from randomized controlled clinical trials to guide clinicians in the dose, frequency, route or duration of thiamine treatment for prophylaxis against or treatment of WKS due to alcohol abuse.
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Affiliation(s)
- E Day
- Department of Psychiatry, University of Birmingham, Queen Elizabeth Psychiatric Hospital, Mindelsohn Way, Birmingham, UK, B15 2QZ
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20
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Affiliation(s)
- R Callaghan
- Rheumatology Department, Walsgrave Hospital, Clifford Bridge Road, Coventry CV2 2DX, UK.
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21
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Martin C, Walker J, Rothnie A, Callaghan R. The expression of P-glycoprotein does influence the distribution of novel fluorescent compounds in solid tumour models. Br J Cancer 2003; 89:1581-9. [PMID: 14562035 PMCID: PMC2394330 DOI: 10.1038/sj.bjc.6601300] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Solid tumours display a complex drug resistance phenotype that involves inherent and acquired mechanisms. Multicellular resistance is an inherent feature of solid tumours and is known to present significant barriers to drug permeation in tumours. Given this barrier, do acquired resistance mechanisms such as P-glycoprotein (P-gp) contribute significantly to resistance? To address this question, the multicellular tumour spheroid (MCTS) model was used to examine the influence of P-gp on drug distribution in solid tissue. Tumour spheroids (TS) were generated from either drug-sensitive MCF7(WT) cells or a drug-resistant, P-gp-expressing derivative MCF7(Adr). Confocal microscopy was used to measure time courses and distribution patterns of three fluorescent compounds; calcein-AM, rhodamine123 and BODIPY-taxol. These compounds were chosen because they are all substrates for P-gp-mediated transport, exhibit high fluorescence and are chemically dissimilar. For example, BODIPY-taxol and rhodamine 123 showed high accumulation and distributed extensively throughout the TS(WT), whereas calcein-AM accumulation was restricted to the outermost layers. The presence of P-gp in TS(Adr) resulted in negligible accumulation, regardless of the compound. Moreover, the inhibition of P-gp by nicardipine restored intracellular accumulation and distribution patterns to levels observed in TS(WT). The results demonstrate the effectiveness of P-gp in modulating drug distribution in solid tumour models. However, the penetration of agents throughout the tissue is strongly determined by the physico-chemical properties of the individual compounds.
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Affiliation(s)
- C Martin
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9OU, UK
| | - J Walker
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9OU, UK
| | - A Rothnie
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9OU, UK
| | - R Callaghan
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9OU, UK
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford OX3 9OU, UK. E-mail:
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22
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Siiman O, Bumm LA, Callaghan R, Blatchford CG, Kerker M. Surface-enhanced Raman scattering by citrate on colloidal silver. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100229a020] [Citation(s) in RCA: 167] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Callaghan R, Siiman O. Raman and resonance Raman studies of bis(3,5-dimethyl-1,2-dithiolylium) tetrachloroferrate(II) and -manganate(II). Inorg Chem 2002. [DOI: 10.1021/ic50220a021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Martin C, Higgins CF, Callaghan R. The vinblastine binding site adopts high- and low-affinity conformations during a transport cycle of P-glycoprotein. Biochemistry 2001; 40:15733-42. [PMID: 11747450 DOI: 10.1021/bi011211z] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Conceptually one may envisage that substrate binding sites on the ABC transporter P-gp cycle between high- and low-affinity conformations in response to signals arising from nucleotide hydrolysis to effect active transport. A radioligand binding assay was used to characterize the interaction of [3H]vinblastine with P-gp and determine how drug binding site parameters are altered during a catalytic cycle of P-gp. In the absence of nucleotide, we show that [3H]vinblastine interacts with a single class of binding site with high affinity (K(d) = 80 +/- 18 nM). In the presence of the nonhydrolyzable ATP analogue AMP-PNP, the drug binding site was in a low-affinity conformation, manifest by a 9-fold increase in K(d) (K(d) = 731 +/- 20 nM). There was no alteration in the binding capacity, reflecting a complete shift in the high-affinity site to a low-affinity form. The posthydrolytic (Mg-ADP-V(i) bound) form of P-gp also exhibited low-affinity substrate binding (K(d) = 446 +/- 57 nM). Restoration of the high-affinity drug binding site conformation (K(d) = 131 +/- 32 nM) did not occur until release of phosphate from the posthydrolysis P-gp-Mg-ADP-P(i). complex. Our results suggest that alteration of the affinity of the vinblastine binding site involves only one nucleotide binding domain per transport cycle. The binding of ATP provides the signal to instigate this change, while release of phosphate post-ATP hydrolysis returns the transporter to its original state to complete the cycle.
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Affiliation(s)
- C Martin
- Nuffield Department of Clinical Laboratory Sciences, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK
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26
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Rothnie A, Theron D, Soceneantu L, Martin C, Traikia M, Berridge G, Higgins CF, Devaux PF, Callaghan R. The importance of cholesterol in maintenance of P-glycoprotein activity and its membrane perturbing influence. Eur Biophys J 2001; 30:430-42. [PMID: 11718296 DOI: 10.1007/s002490100156] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In tumour cell lines that display multidrug resistance, expression of P-glycoprotein (P-gp) alters many aspects of biomembrane organization in addition to its well-characterized drug transport activity. We have developed a reconstitution system to directly investigate the effect of purified P-gp on the biophysical properties of lipid bilayers. Using a mixed detergent system it was possible to efficiently reconstitute P-gp at lipid:protein ratios as low as 2.5 (w/w) by removal of detergent using adsorption to SM-2 BioBeads. P-gp was able to alter many biophysical parameters associated with lipid organization within bilayers. For example, the changes in overall fluidity and excimer formation by lipid analogues indicate modified packing organization of bilayer constituents. Surprisingly, given its role in conferring drug resistance, P-gp insertion into bilayers also caused significantly increased permeability to aqueous compounds, also reflecting a modified phospholipid environment. Translocation of various phospholipid species between leaflets of the bilayer was increased in the presence of P-gp; however, the effect was not dependent on ATP hydrolysis by the protein. Physiological concentrations of cholesterol modified P-gp function and the degree to which it perturbed bilayer organization. The basal ATPase activity of P-gp was increased in a dose-dependent fashion by the incorporation of cholesterol in PC:PE liposomes. In addition, the degree to which the modulator verapamil was able to stimulate this basal ATPase activity was reduced by the presence of cholesterol in proteoliposomes. However, the potency of verapamil was unaltered, suggesting a specific effect, not simply caused by lower drug penetration into the cholesterol containing bilayers. In summary, P-gp is able to cause perturbation in the organization of bilayer constituents. Cholesterol imparted "stability" to this perturbation of bilayer organization by P-gp and moreover this led to altered protein function.
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Affiliation(s)
- A Rothnie
- Nuffield Department of Clinical Laboratory Science, John Radcliffe Hospital, University of Oxford, UK
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27
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Gil-Benso R, Martinez-Lorente A, Pellin-Perez A, Navarro-Fos S, Gregori-Romero MA, Carda C, Callaghan R, Peydro-Olaya A, Llombart-Bosch A. Characterization of a new rat cell line established from 2'AAF-induced combined hepatocellular cholangiocellular carcinoma. In Vitro Cell Dev Biol Anim 2001. [PMID: 11249201 DOI: 10.1290/1071-2690(2001)037%3c0017:coanrc%3e2.0.co;2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A rat cell line-nominated CC-62 derived from a combined hepatocellular and cholangiocellular carcinoma obtained by administration of 2-acetylaminofluorene to male Wistar rats, has been established. Using light and electron microscopy it was determined that morphologically the tumor consisted of a mixed population of hepatocytes and cholangiolar neoplastic cells, intermingled with small, undifferentiated oval-like cells. The CC-62 line has been maintained through 90 passages in culture adopting a paving stone arrangement. Doubling time at the 12th passage was 23 h. Immunostaining with a panel of antisera was performed to identify the cytological profiles of the cell line. There was no k-ras or p53 expression by immunohistochemistry, and molecular biology failed to detect mutations. Molecular analysis by reverse transcriptase-polymerase chain reaction revealed transcripts for c-met but no expression of HGF messenger ribonucleic acid. Three cell lines cloned from CC-62 showed the same immunohistochemical and molecular pattern as the parental line. Cytogenetic analysis revealed a chromosome number ranging from 74 to 82 with a modal number of 79 but no clonal structural abnormalities were found. Deoxyribonucleic acid ploidy analysis showed an aneuploid peak. CC-62 caused tumors 1 mo after subcutaneous transplantation into nude mice, with morphological patterns of mucosecretory solid and spindle-shaped carcinoma. This cell line is the first established from a primary rat combined hepatocellular and cholangiocellular neoplasm. The resulting cells expressed biological and morphological markers of hepatocytes and cholangiolar cells. Therefore this cell line may contribute to a better understanding of the histogenesis of liver cancer.
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Affiliation(s)
- R Gil-Benso
- Department of Pathology, Medical School, University of Valencia, Spain
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28
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Gil-Benso R, Martinez-Lorente A, Pellin-Perez A, Navarro-Fos S, Gregori-Romero MA, Carda C, Callaghan R, Peydro-Olaya A, Llombart-Bosch A. Characterization of a new rat cell line established from 2'AAF-induced combined hepatocellular cholangiocellular carcinoma. In Vitro Cell Dev Biol Anim 2001; 37:17-25. [PMID: 11249201 DOI: 10.1290/1071-2690(2001)037<0017:coanrc>2.0.co;2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A rat cell line-nominated CC-62 derived from a combined hepatocellular and cholangiocellular carcinoma obtained by administration of 2-acetylaminofluorene to male Wistar rats, has been established. Using light and electron microscopy it was determined that morphologically the tumor consisted of a mixed population of hepatocytes and cholangiolar neoplastic cells, intermingled with small, undifferentiated oval-like cells. The CC-62 line has been maintained through 90 passages in culture adopting a paving stone arrangement. Doubling time at the 12th passage was 23 h. Immunostaining with a panel of antisera was performed to identify the cytological profiles of the cell line. There was no k-ras or p53 expression by immunohistochemistry, and molecular biology failed to detect mutations. Molecular analysis by reverse transcriptase-polymerase chain reaction revealed transcripts for c-met but no expression of HGF messenger ribonucleic acid. Three cell lines cloned from CC-62 showed the same immunohistochemical and molecular pattern as the parental line. Cytogenetic analysis revealed a chromosome number ranging from 74 to 82 with a modal number of 79 but no clonal structural abnormalities were found. Deoxyribonucleic acid ploidy analysis showed an aneuploid peak. CC-62 caused tumors 1 mo after subcutaneous transplantation into nude mice, with morphological patterns of mucosecretory solid and spindle-shaped carcinoma. This cell line is the first established from a primary rat combined hepatocellular and cholangiocellular neoplasm. The resulting cells expressed biological and morphological markers of hepatocytes and cholangiolar cells. Therefore this cell line may contribute to a better understanding of the histogenesis of liver cancer.
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MESH Headings
- 2-Acetylaminofluorene
- Aneuploidy
- Animals
- Bile Duct Neoplasms/chemistry
- Bile Duct Neoplasms/pathology
- Bile Duct Neoplasms/ultrastructure
- Bile Ducts, Intrahepatic
- Carcinoma, Hepatocellular/chemically induced
- Carcinoma, Hepatocellular/pathology
- Carcinoma, Hepatocellular/ultrastructure
- Cholangiocarcinoma/chemically induced
- Cholangiocarcinoma/pathology
- Cholangiocarcinoma/ultrastructure
- DNA, Neoplasm/analysis
- Genes, ras
- Hepatocyte Growth Factor/metabolism
- Immunohistochemistry
- Karyotyping
- Liver Neoplasms/chemically induced
- Liver Neoplasms/pathology
- Liver Neoplasms/ultrastructure
- Male
- Mice
- Mice, Nude
- Microscopy, Electron
- Proto-Oncogene Proteins c-met/metabolism
- Rats
- Rats, Wistar
- Reverse Transcriptase Polymerase Chain Reaction
- Transplantation, Heterologous
- Tumor Cells, Cultured/cytology
- Tumor Cells, Cultured/ultrastructure
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- R Gil-Benso
- Department of Pathology, Medical School, University of Valencia, Spain
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29
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Martin C, Berridge G, Mistry P, Higgins C, Charlton P, Callaghan R. Drug binding sites on P-glycoprotein are altered by ATP binding prior to nucleotide hydrolysis. Biochemistry 2000; 39:11901-6. [PMID: 11009602 DOI: 10.1021/bi000559b] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
P-glycoprotein (P-gp) confers multiple drug resistance on cancer cells by acting as a plasma membrane localized ATP-dependent drug efflux pump. Currently, there is little information on the nature of the communication between the energy-providing nucleotide binding domains (NBDs) and the drug binding sites of P-gp to generate transport of substrate. Many substrates and modulators cause alterations in ATP hydrolysis, but what effect do the various stages of the catalytic cycle have on drug interaction with P-gp? Vanadate trapping of Mg.ADP caused a reversible decrease in the binding capacity of the transported substrate [(3)H]-vinblastine and the nontransported modulator [(3)H]XR9576 to P-gp in CH(r)B30 cell membranes. The non-hydrolyzable nucleotide analogue ATP-gamma-S also caused a reduction in the binding capacity of [(3)H]-vinblastine but not for the modulator [(3)H]XR9576. This indicates that signaling to the NBDs following binding of a nontransported modulator is different to that transmitted upon interaction of a transported substrate. Second, it appears that the binding of nucleotide, rather than its hydrolysis, causes the initial conformational shift in the drug-binding site during a transport cycle.
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Affiliation(s)
- C Martin
- Nuffield Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, Oxford, U.K
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30
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Abstract
P-glycoprotein, a member of the ATP-binding cassette transporter family, is able to confer resistance on tumors against a large number of functionally and chemically distinct cytotoxic compounds. Several recent investigations suggest that P-glycoprotein contains multiple drug binding sites rather than a single site of broad substrate specificity. In the present study, radioligand-binding techniques were used to directly characterize drug interaction sites on P-glycoprotein and how these multiple sites interact. The drugs used were classified as either 1) substrates, which are known to be transported by P-glycoprotein (e.g., vinblastine) or 2) modulators, which alter P-glycoprotein function but are not themselves transported by the protein (e.g., XR9576). Drug interactions with P-glycoprotein were either competitive, at a common site, or noncompetitive, and therefore at distinct sites. Based on these data, we can assign a minimum of four drug binding sites on P-glycoprotein. These sites fall into two categories: transport, at which translocation of drug across the membrane can occur, and regulatory sites, which modify P-glycoprotein function. Intriguingly, however, some modulators interact with P-glycoprotein at a transport site rather than a regulatory site. The pharmacological data also demonstrate that both transport and regulatory sites are able to switch between high- and low-affinity conformations. The multiple sites on P-glycoprotein display complex allosteric interactions through which interaction of drug at one site switches other sites between high- or low-affinity conformations. The data are discussed in terms of a model for the mechanism of transport by P-glycoprotein.
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Affiliation(s)
- C Martin
- Department of Clinical Laboratory Sciences, John Radcliffe Hospital, University of Oxford, United Kingdom
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31
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Ferry D, Boer R, Callaghan R, Ulrich WR. Localization of the 1,4-dihydropyridine drug acceptor of P-glycoprotein to a cytoplasmic domain using a permanently charged derivative N-methyl dexniguldipine. Int J Clin Pharmacol Ther 2000; 38:130-40. [PMID: 10739116 DOI: 10.5414/cpp38130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
INTRODUCTION P-glycoprotein (P-gp) is a 170 kDa ATPase which can transport a wide range of natural product cytotoxic drugs out of cells, thus conferring the multidrug resistance (MDR) phenotype. METHODS In this paper we used the 1,4-dihydropyridine (1,4-DHP) MDR-reversing agent dexniguldipine (DN), and a derivative with a quaternary nitrogen which is permanently charged, N-methyl-DN, to explore the sidedness of block of [3H]-vinblastine transport by P-gp. RESULTS In cytotoxicity assays, 1 microM DN sensitized MCF7 ADR cells, causing a 13-fold decrease in the EC50 of vinblastine from 400 +/- 80 nM to 30 +/- 25 nM. In marked contrast, N-methyl-DN was without effect. In intact MCF7 ADR cells, DN reversed the [3H]vinblastine uptake deficit with an EC50 of 445 +/- 100 nM, again, N-methyl-DN was inactive. In photoaffinity labelling studies using the arylazide [3H]-B9209-005 in whole cells, DN potently inhibited incorporation of the photoaffinity label into P-gp whilst N-methyl-DN was without effect. However, in photoaffinity labelling studies in membrane fragments, both DN and N-methyl-DN potently inhibited [3H]-B9209-005 photoaffinity labelling of P-gp. Furthermore, in membrane fragments [3H]-vinblastine binding to P-glycoprotein was potently inhibited by both N-methyl-DN (Ki 10.7 +/- 4.9 nM) and DN (Ki 11.2 +/- 3.8 nM), and both N-methyl-DN and DN blocked ATP-dependent [3H]-vinblastine transport into inside-out vesicles. Thus, in intact cells the permanently charged 1,4-dihydropyridine, N-methyl-DN is unable to reverse the MDR phenotype or photoaffinity labelling of P-gp. However, in cell fragments and inside-out vesicles, N-methyl-DN binds avidly to P-gp and this binding blocks [3H]-vinblastine transport. CONCLUSION These data are consistent with the hypothesis that 1,4-DHPs block [3H]-vinblastine binding, and thereby transport by P-gp, by acting at a domain accessible only from the cytoplasm.
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Affiliation(s)
- D Ferry
- CRC Institute for Cancer Studies, University of Birmingham, Edgbaston, UK
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Taylor JC, Ferry DR, Higgins CF, Callaghan R. The equilibrium and kinetic drug binding properties of the mouse P-gp1a and P-gp1b P-glycoproteins are similar. Br J Cancer 1999; 81:783-9. [PMID: 10555746 PMCID: PMC2374293 DOI: 10.1038/sj.bjc.6690764] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/1999] [Revised: 05/27/1999] [Accepted: 06/03/1999] [Indexed: 01/28/2023] Open
Abstract
The gene encoding the multidrug resistance P-glycoprotein (P-gp) is duplicated in rodent species and the functional basis for this remains unresolved. Despite a high sequence similarity, the mouse P-gp1a and P-gp1b isoforms show distinct patterns of tissue distribution which suggest a specific role of the P-gp1b isoform in steroid transport. In the present study possible biochemical differences between the isoforms were directly investigated at the level of drug interaction. There was no detectable difference in the affinity or binding capacity of the two isoforms towards [3H]vinblastine at equilibrium. Similarly, the rate at which [3H]vinblastine associates with P-gp was indistinguishable between the two isoforms. Some modest differences were observed in the relative abilities of the multidrug-resistant (MDR) reversing agents CP100-356, nicardipine and verapamil to displace equilibrium [3H]vinblastine binding to P-gp1a and P-gp1b. The steroid hormone progesterone displayed a low affinity (Ki = 1.2 +/- 0.2 microM for P-gp1a and 3.5 +/- 0.5 microM for P-gp1b), suggesting an unlikely role as a physiological substrate. Thus the mouse isoforms do not appear to exhibit functional differences at the level of initial substrate interaction with protein.
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Affiliation(s)
- J C Taylor
- Nuffield Department of Clinical Biochemistry & Cellular Science, University of Oxford, John Radcliffe Hospital, UK
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Dale IL, Tuffley W, Callaghan R, Holmes JA, Martin K, Luscombe M, Mistry P, Ryder H, Stewart AJ, Charlton P, Twentyman PR, Bevan P. Reversal of P-glycoprotein-mediated multidrug resistance by XR9051, a novel diketopiperazine derivative. Br J Cancer 1998; 78:885-92. [PMID: 9764579 PMCID: PMC2063130 DOI: 10.1038/bjc.1998.597] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
XR9051 (N-(4-(2-(6,7-Dimethoxy-1,2,3,4-tetrahydro-2-isoquinolyl)ethyl)phe nyl)-3-((3Z,6Z)-6-benzylidene-1-methyl-2,5-dioxo-3-pipera zinylidene) methylbenzamide) was identified as a potent modulator of P-glycoprotein-mediated multidrug resistance (MDR) following a synthetic chemistry programme based on a natural product lead compound. The activity of XR9051 was determined using a panel of human and murine drug-resistant cell lines (H69/LX4, 2780AD, EMT6/AR 1.0, MC26 and P388/DX Johnson). XR9051 was able to reverse resistance to a variety of cytotoxic drugs, including doxorubicin, etoposide and vincristine, which are associated with classical MDR. At a concentration of 0.3-0.5 microM, XR9051 was able to fully sensitize resistant cells to cytotoxics, whereas little or no effect was observed on the corresponding parental cell lines. No effect of XR9051 was observed on the response of cells to non-MDR cytotoxics such as methotrexate and 5-fluorouracil. XR9051 was consistently more potent than cyclosporin A (CsA) and verapamil (Vpm) in all assays used. XR9051 inhibited the efflux of [3H]daunorubicin from preloaded cells and, unlike CsA and Vpm, remained active for several hours after removal of resistance-modifying agent. In photoaffinity labelling experiments employing [3H]azidopine, XR9051 was able to displace binding to P-glycoprotein. In binding studies using [3H]vinblastine, XR9051 was shown to be a potent inhibitor of the binding of the cytotoxic to P-glycoprotein (EC50 = 1.4 +/- 0.5 nM). Taken together, the results indicate that XR9051 reverses the MDR phenotype through direct interaction with P-glycoprotein.
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van Veen HW, Callaghan R, Soceneantu L, Sardini A, Konings WN, Higgins CF. A bacterial antibiotic-resistance gene that complements the human multidrug-resistance P-glycoprotein gene. Nature 1998; 391:291-5. [PMID: 9440694 DOI: 10.1038/34669] [Citation(s) in RCA: 181] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bacteria have developed many fascinating antibiotic-resistance mechanisms. A protein in Lactococcus lactis, LmrA, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane. Unlike other known bacterial multidrug-resistance proteins, LmrA is an ATP-binding cassette (ABC) transporter. The human multidrug-resistance P-glycoprotein, encoded by the MDR1 gene, is also an ABC transporter, overexpression of which is one of the principal causes of resistance of human cancers to chemotherapy. We expressed lmrA in human lung fibroblast cells. Surprisingly, LmrA was targeted to the plasma membrane and conferred typical multidrug resistance on these human cells. The pharmacological characteristics of LmrA and P-glycoprotein-expressing lung fibroblasts were very similar, and the affinities of both proteins for vinblastine and magnesium-ATP were indistinguishable. Blockers of P-glycoprotein-mediated multidrug resistance also inhibited LmrA-dependent drug resistance. Kinetic analysis of drug dissociation from LmrA expressed in plasma membranes of insect cells revealed the presence of two allosterically linked drug-binding sites indistinguishable from those of P-glycoprotein. These findings have implications for the reversal of antibiotic resistance in pathogenic microorganisms. Taken together, they demonstrate that bacterial LmrA and human P-glycoprotein are functionally interchangeable and that this type of multidrug-resistance efflux pump is conserved from bacteria to man.
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Affiliation(s)
- H W van Veen
- Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Haren, The Netherlands.
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Martin C, Berridge G, Higgins CF, Callaghan R. The multi-drug resistance reversal agent SR33557 and modulation of vinca alkaloid binding to P-glycoprotein by an allosteric interaction. Br J Pharmacol 1997; 122:765-71. [PMID: 9375975 PMCID: PMC1564986 DOI: 10.1038/sj.bjp.0701429] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. The interaction of the indolizin sulfone SR33557 with the multidrug resistance P-glycoprotein (P-gp), was used to explore the nature of drug binding site(s) on this transporter. The steady-state accumulation of [3H]-vinblastine in P-gp expressing CHrB30 cells was increased by SR33557 with greater potency than verapamil. Furthermore, SR33557 potentiated the affinity of verapamil to modulate vinblastine transport when added simultaneously. 2. Verapamil elicited a 1.5 to 2.5 fold stimulation of basal ATPase activity in CHrB30 membranes, whereas SR33557 and vinblastine inhibited activity, but only at relatively high concentrations. However, SR33557 and vinblastine decreased the Vmax but not the Km for verapamil stimulation of ATPase activity. This is indicative of a non-competitive interaction, most likely at distinct sites. 3. The specific [3H]-vinblastine binding to P-gp in CHrB30 cell membranes was displaced by SR33557 with an IC50 of 8.3 +/- 4.5 nM. Moreover, SR33557 caused a 3 fold increase in the dissociation rate of vinblastine binding to P-gp indicating a negative allosteric effect on the vinca alkaloid acceptor site. 4. These results demonstrate that SR33557 interacts with a site on P-gp which is distinct from, but allosterically linked to the vinca alkaloid site. The apparent broad substrate specificity displayed by P-gp may be explained by a multiple drug binding site model.
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Affiliation(s)
- C Martin
- Nuffield Department of Clinical Biochemistry, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital
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Callaghan R, Berridge G, Ferry DR, Higgins CF. The functional purification of P-glycoprotein is dependent on maintenance of a lipid-protein interface. Biochim Biophys Acta 1997; 1328:109-24. [PMID: 9315609 DOI: 10.1016/s0005-2736(97)00079-5] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
P-Glycoprotein (P-gp) is a 180-kDa membrane-bound transporter which can confer the multi-drug resistance phenotype on tumor cells. We have examined the factors required to preserve activity of P-gp during its purification. The starting material for purification was plasma membranes from Chinese hamster ovary (CHrB30) cells, overexpressing P-glycoprotein. These membranes displayed drug stimulated ATPase activity (Vm = 897 +/- 55 nmol min(-1) mg(-1); Km = 1.8 +/- 0.4 mM) and high affinity binding of [3H]vinblastine (Kd = 36 +/- 5 nM; Bm = 161 +/- 11 pmol/mg). Several non-ionic detergents which readily solubilized P-glycoprotein significantly inhibited ATPase activity and drug binding at concentrations well below their respective CMC values. This inactivation was prevented by excess crude lipid mixtures, with the greatest protection afforded against dodecyl-maltoside. Furthermore, the significantly reduced binding affinity and capacity of solubilized P-gp was partly reversed by the addition of lipids. A combination of anion-exchange and hydroxyapatite chromatography were used to purify P-gp with high yield to greater than 90%. The purified, reconstituted P-gp displayed high ATPase activity (Vm = 2137 +/- 309; Km = 2.9 +/- 0.9 mM) which was stimulated by verapamil (EC50 = 3.8 +/- 0.6 microM) and inhibited by orthovanadate (3.1 +/- 0.8 microM). Pure P-gp also displayed high affinity vinblastine binding (Kd = 64 +/- 9 nM) with a capacity of 2320 +/- 192 pmol/mg. This purification scheme yields the highest P-gp activity reported to date, and indicates a dependence of function on maintaining a lipid-protein interface.
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Affiliation(s)
- R Callaghan
- Nuffield Department of Clinical Biochemistry, John Radcliffe Hospital, University of Oxford, UK.
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Abstract
In order to elucidate the mechanism by which the multidrug resistance P-glycoprotein extrudes cytotoxic drugs from the cell, and particularly the number and nature of the drug binding site(s), knowledge of the structure of P-gp is essential. A considerable body of genetic and biochemical data has accrued which gives insights into P-gp structure and function. These data are critically reviewed, particularly in relation to the low resolution structure of P-gp which has recently been determined by electron microscopy. P-gp is one of the best characterised of the ABC transporters and these structure-function studies may have more general implications.
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Affiliation(s)
- C F Higgins
- Nuffield Department of Clinical Biochemistry, University of Oxford, John Radcliffe Hospital, UK
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Rosenberg MF, Callaghan R, Ford RC, Higgins CF. Structure of the multidrug resistance P-glycoprotein to 2.5 nm resolution determined by electron microscopy and image analysis. J Biol Chem 1997; 272:10685-94. [PMID: 9099718 DOI: 10.1074/jbc.272.16.10685] [Citation(s) in RCA: 259] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
P-glycoprotein (P-gp) is a member of the ATP binding cassette superfamily of active transporters and can confer multidrug resistance on cells and tumors by pumping chemotherapeutic drugs from the cytoplasm. P-gp was purified from CHrB30 cells and retained the ability to bind substrates and hydrolyze ATP. Labeling of P-gp with lectin-gold particles suggested it is monomeric. An initial structure of purified P-gp was determined to 2.5 nm resolution by electron microscopy and single particle image analysis of both detergent-solubilized and lipid-reconstituted protein. The structure was further refined by three dimensional reconstructions from single particle images and by Fourier projection maps of small two-dimensional crystalline arrays (unit cell parameters: a, 14.2 nm; b, 18.5 nm; and gamma, 91.6 degrees ). When viewed from above the membrane plane the protein is toroidal, with 6-fold symmetry and a diameter of about 10 nm. There is a large central pore of about 5 nm in diameter, which is closed at the inner (cytoplasmic) face of the membrane, forming an aqueous chamber within the membrane. An opening from this chamber to the lipid phase is present. The projection of the protein perpendicular to the membrane is roughly rectangular with a maximum depth of 8 nm and two 3-nm lobes exposed at the cytoplasmic face of the membrane, likely to correspond to the nucleotide binding domains. This study provides the first experimental insight into the three-dimensional architecture of any ATP binding cassette transporter.
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Affiliation(s)
- M F Rosenberg
- Department of Biochemistry and Applied Molecular Biology, University of Manchester Institute of Science and Technology, P. O. Box 88, Manchester M60 1QD, United Kingdom
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Goodfellow HR, Sardini A, Ruetz S, Callaghan R, Gros P, McNaughton PA, Higgins CF. Protein kinase C-mediated phosphorylation does not regulate drug transport by the human multidrug resistance P-glycoprotein. J Biol Chem 1996; 271:13668-74. [PMID: 8662768 DOI: 10.1074/jbc.271.23.13668] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
P-glycoprotein (P-gp) is an active transporter that can confer multidrug resistance by pumping cytotoxic drugs out of cells and tumors. P-gp is phosphorylated at several sites in the "linker" region, which separates the two halves of the molecule. To examine the role of phosphorylation in drug transport, we mutated P-gp such that it could no longer be phosphorylated by protein kinase C (PKC). When expressed in yeast, the ability of the mutant proteins to confer drug resistance, or to mediate [3H]vinblastine accumulation in secretory vesicles, was indistinguishable from that of wild type P-gp. A matched pair of mammalian cell lines were generated expressing wild type P-gp and a non-phosphorylatable mutant protein. Mutation of the phosphorylation sites did not alter P-gp expression or its subcellular localization. The transport properties of the mutant and wild type proteins were indistinguishable. Thus, phosphorylation of the linker of P-gp by PKC does not affect the rate of drug transport. In light of these data, the use of agents that alter PKC activity to reverse multidrug resistance in the clinic should be considered with caution.
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Affiliation(s)
- H R Goodfellow
- Imperial Cancer Research Laboratories, Nuffield Department of Clinical Biochemistry, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom
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Abstract
The effect of several opiate compounds on I- efflux was investigated in cultured cell lines. I- efflux was evoked by two distinct stimuli, namely cell swelling and elevation of cellular cAMP levels by prostaglandin E2. Cells expressing the multidrug resistance P-glycoprotein were found to have increased I- efflux in response to hypo-osmotic challenge. This increased I- efflux in P-glycoprotein containing cells was reduced to levels found in parental cells by the opiates morphine, pentazocine and naloxone. Addition of prostaglandin E2 to T84 cells resulted in elevated cellular cAMP levels and a significant I- efflux. This cAMP stimulated efflux was also inhibited by several opiates. None of the opiates was able to alter cAMP levels or protein kinase A mediated phosphorylation of immunoprecipitated cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel in T84 cells. The ability of opiates to alter ion conductances is discussed in relation to the anti-diarrheal effects of these compounds.
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Affiliation(s)
- R Callaghan
- Hospital for Sick Children, Department of Biochemistry, University of Toronto, Ontario, Canada
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Callaghan R, Riordan JR. Collateral sensitivity of multidrug resistant cells to narcotic analgesics is due to effects on the plasma membrane. Biochim Biophys Acta 1995; 1236:155-62. [PMID: 7794945 DOI: 10.1016/0005-2736(95)00042-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
It has previously been demonstrated that opiates interact directly with P-glycoprotein in drug resistant Chinese hamster ovary (CHO) cells (Callaghan, R. and Riordan, J.R. (1993) J. Biol. Chem. 268, 16059-16064). In this study we have examined the effects of several opiates on the growth of drug sensitive and resistant CHO and human MCF7 cell lines. The growth of P-glycoprotein expressing cells was inhibited by the opiates pentazocine, pethidine and naloxone to a greater extent than in drug sensitive cells. Since P-glycoprotein is localised at the plasma membrane the effects of opiates on membrane biophysical properties were investigated. The opiates caused a fluidizing effect in membranes from P-glycoprotein expressing cells and decreased the basal level of P-glycoprotein phosphorylation. In addition, they were able to increase the leakage of the membrane impermeant compound 6-carboxyfluorescein entrapped in model membrane vesicles. The ability to alter membrane biophysical properties correlated with the inhibitory effects on growth of drug resistant cells. These results suggest that the collateral sensitivity of P-glycoprotein expressing cell lines to opiates is mediated by the drugs' effects on the plasma membrane.
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Affiliation(s)
- R Callaghan
- Research Institute Hospital for Sick Children, Toronto, Ontario, Canada
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Abstract
Tamoxifen is an anti-oestrogen which is currently being assessed as a prophylactic for women at high risk of breast cancer. Taxoxifen has also been shown to reverse multidrug resistance in P-glycoprotein (P-gp)-expressing cells, although the mechanism of action is unknown. In this study we demonstrate that tamoxifen interacts directly with P-gp. Plasma membranes from P-gp-expressing cells bound [3H]tamoxifen in a specific and saturable fashion. A 180 kDa membrane protein in these membranes, labelled by the affinity analogue tamoxifen aziridine and azidopine, was shown to be P-gp. Tamoxifen reduced the binding of vinblastine and azidopine to P-gp, and tamoxifen increased [3H]vinblastine accumulation in P-gp-expressing cells to levels approaching those in non-P-gp-expressing cells. However, the cellular accumulation of [3H]tamoxifen itself was not influenced by the presence of P-gp. Thus, tamoxifen appears to reverse multidrug resistance by binding to P-gp and inhibiting the transport of cytotoxic drugs, but does not itself appear to be transported by the protein.
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Affiliation(s)
- R Callaghan
- Imperial Cancer Research Fund Laboratories, Institute for Molecular Medicine, Oxford, UK
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Krouskop TA, Randall C, Davis J, Garber S, Williams S, Callaghan R. Evaluating the long-term performance of a foam-core hospital replacement mattress. J Wound Ostomy Continence Nurs 1994; 21:241-6. [PMID: 7704131 DOI: 10.1097/00152192-199411000-00010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Many hospitals have begun replacing their standard mattresses with pressure-reducing foam mattresses to eliminate the costly overlays that have been used for comfort and to protect patients at risk for development of pressure ulcers. Although researchers have tested the performance of new mattresses and have shown that many may be of use with patients at high risk, no information is available on the pressure-reducing capabilities of used mattresses. This study was designed to evaluate changes with use in the support characteristics of foam-core hospital replacement mattresses. In the first part of the study, interface pressure measurements were made at regular intervals over an extended period of use. Sixty mattresses were randomly selected from 750 mattresses currently in use at St. Luke's Episcopal Hospital, Texas Medical Center, Houston. The mattresses were labeled and marked at three selected points, and interface pressures under a standard load were measured at approximately 3-month intervals for 12 months. In the second part of the study, the stiffness of the foam, a measure of the foam's ability to support a weight, was measured at selected points on the mattresses. Patient reports of discomfort in the sacral area and of "sinking" into the middle of the mattress prompted this phase of the study. The stiffness profiles of 25 new mattresses were compared with those of 25 randomly selected mattresses that had been in regular use for at least 24 months. Data analyzed from part one showed trends that indicated that the interface pressures increased at each site during the course of the study; however, an analysis of variance indicated that the changes were not statistically significant during the time frame of the study.(ABSTRACT TRUNCATED AT 250 WORDS)
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Callaghan R, Paull P, Desmond PV, Mashford ML. Factors affecting the hepatic elimination of oxidized and of glucoronidated high clearance drugs following acute administration of carbon tetrachloride. J Hepatol 1994; 20:742-9. [PMID: 7930474 DOI: 10.1016/s0168-8278(05)80144-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The factors affecting drug elimination following acute administration of carbon tetrachloride (CCl4) were investigated using a perfused rat liver system. Morphine and pethidine were used as markers of hepatic glucuronidation and oxidation, respectively. Hepatoxicity of CCl4 was indicated by widespread cellular necrosis and raised serum asparatate aminotransferase levels. At a perfusion rate of 10 ml/min, the extraction ratio of morphine in the normal liver was 0.67 +/- 0.18 and fell to 0.48 +/- 0.03 (p < 0.001) in the acutely damaged livers. The hepatic clearance of morphine fell from 6.7 +/- 0.2 ml/min in controls to 4.7 +/- 0.3 (p < 0.005) in the treated livers. Similar changes were seen at perfusion rates of 7 and 12 ml/min. Intrinsic clearances calculated according to both the venous equilibrium and the undistributed sinusoidal models were independent of perfusion rate and were also lower in the damaged livers. Perfusion rate was a dominant factor in determining morphine elimination in control livers. However, in the damaged livers, the fall in intrinsic clearance resulted in the elimination of morphine being mixed, i.e. both capacity and flow limited. At a perfusion rate of 10 ml/min, the extraction ratio of pethidine was 0.97 +/- 0.01 in control livers and was reduced to 0.91 +/- 0.02 (p < 0.005) in damaged livers. The hepatic clearance also fell at each perfusion rate in the damaged livers. As for morphine, the intrinsic clearances of pethidine calculated by both venous equilibrium and undistributed sinusoidal models gave qualitatively similar results and were lower in the damaged livers than controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R Callaghan
- Department of Clinical Pharmacology, St Vincent's Hospital, Fitzroy, Victoria, Australia
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Abstract
The effect of a choline-deficient diet on the hepatic glucuronidation of morphine was investigated using a rat perfused liver system. Rats fed a choline-deficient diet developed a fatty liver with minimal necrosis. Despite the morphological changes, neither hepatic extraction ratio (0.51 +/- 0.02 in control; 0.45 +/- 0.04 in the choline-deficient rats) nor intrinsic clearance (0.85 +/- 0.05 in control; 0.77 +/- 0.09 in choline-deficient rats) were affected by this injury model. This finding suggests that glucuronidation is relatively resistant to this chronic liver injury.
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Affiliation(s)
- R Callaghan
- Department of Clinical Pharmacology, St Vincent's Hospital, Fitzroy, Victoria, Australia
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Callaghan R, Riordan JR. Synthetic and natural opiates interact with P-glycoprotein in multidrug-resistant cells. J Biol Chem 1993; 268:16059-64. [PMID: 8101846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The ability of P-glycoprotein (P-gp) to transport naturally occurring and synthetic opiate analgesics was investigated. Multidrug-resistant Chinese hamster ovary cells (B30) were found to accumulate significantly lower amounts of morphine than their drug-sensitive counterparts (B1). This decreased accumulation was reversed upon depletion of cellular stores of ATP. In addition, morphine bound to plasma membranes from B30 cells in a specific, saturable fashion. Verapamil and vinblastine, compounds transported by P-gp, were able to increase accumulation and displace the binding of morphine in B30 cells. In turn, the synthetic opiates meperidine, pentazocine, and methadone were able to increase the accumulation of vinblastine in resistant cells. These compounds were also able to displace the specific binding of vinblastine and the photoaffinity labeling of P-gp in plasma membranes by the radioiodinated anthracycline, iodomycin. The implications of these findings in relation to the distribution, tolerance, and gastrointestinal side effects of opiates are discussed.
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Affiliation(s)
- R Callaghan
- Departments of Biochemistry and Clinical Biochemistry, University of Toronto, Ontario, Canada
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Callaghan R, Desmond PV, Paull P, Mashford ML. Hepatic enzyme activity is the major factor determining elimination rate of high-clearance drugs in cirrhosis. Hepatology 1993; 18:54-60. [PMID: 8325621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
The relative importance of alterations in hepatic enzyme activity, blood flow and drug binding to drug elimination in patients with liver disease remains controversial. In addition, liver disease appears to selectively impair drug oxidation pathways while leaving glucuronidation preserved. These studies using isolated perfused rat livers were designed to examine the effects of liver disease on the hepatic extraction and clearance and intrinsic clearance of morphine, a glucuronidated drug, and meperidine, an oxidized drug, under controlled blood flow and drug-binding conditions. We chose chronic carbon tetrachloride-induced cirrhosis as the liver disease. At a flow rate of 12 ml/min, the extraction of meperidine was reduced from 0.91 +/- 0.02 ml/min in controls to 0.76 +/- 0.04 ml/min (p < 0.05) in cirrhosis, hepatic clearance was reduced from 10.9 +/- 0.3 ml/min in controls to 9.15 +/- 0.48 ml/min (p < 0.05) in cirrhosis and intrinsic hepatic clearance was reduced from 179 +/- 35 ml/min in controls to 69 +/- 14 ml/min (p < 0.05) in cirrhosis. In contrast, for morphine we saw no significant changes: extraction ratio, 0.59 +/- 0.02 in controls and 0.49 +/- 0.04 in cirrhosis; hepatic clearance, 7.02 +/- 0.26 ml/min in controls and 6.04 +/- 0.42 ml/min in cirrhosis; and hepatic intrinsic clearance, 15.4 +/- 1.2 ml/min in controls and 13.9 +/- 2.3 ml/min in cirrhosis. Regression analysis of hepatic clearance vs. hepatic blood flow and hepatic clearance vs. hepatic intrinsic clearance demonstrate that in normal livers the elimination of both morphine and meperidine is mainly dependent on blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- R Callaghan
- Department of Clinical Pharmacology, St. Vincent's Hospital, Fitzroy, Victoria, Australia
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Callaghan R, Stafford A, Epand RM. Increased accumulation of drugs in a multidrug resistant cell line by alteration of membrane biophysical properties. Biochim Biophys Acta 1993; 1175:277-82. [PMID: 8435444 DOI: 10.1016/0167-4889(93)90217-d] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Growth of CHRC5 multidrug resistant cells in media enriched in a saturated C-17 fatty acid, heptadecanoic acid, resulted in these cells accumulating vinblastine at a rate and to an extent comparable to that of the parental cell line AB1. The fatty acid-enriched growth media had no effect on the ability of AB1 cells to take up vinblastine. The action of amphiphiles on the uptake of rhodamine dyes by CHRC5 cells was compared with the increased dye accumulation affected by verapamil. Membrane rigidifying agents, such as the saturated fatty acid stearic acid, or the cholesterol derivatives, cholesteryl hemisuccinate and cholesteryl phosphorylcholine, as well as a membrane fluidizing unsaturated fatty acid, linoleic acid, could significantly increase dye uptake, although not as well as verapamil. These results taken in conjunction with other reports in the literature, demonstrate that multidrug resistance is sensitive to alterations of membrane properties. They suggest that perturbation of the membrane to either increased or to decreased membrane fluidity can lower the level of resistance.
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Affiliation(s)
- R Callaghan
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Canada
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Callaghan R, van Gorkom LC, Epand RM. A comparison of membrane properties and composition between cell lines selected and transfected for multi-drug resistance. Br J Cancer 1992; 66:781-6. [PMID: 1358166 PMCID: PMC1977978 DOI: 10.1038/bjc.1992.360] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Cell lines selected (CHRC5) and transfected (LR-73-1A) for multi-drug resistance have total lipid compositions which are indistinguishable between resistant and parental cells. Lipid composition was evaluated by 1H NMR and the total fatty acid content by GLC. No change in surface hydrophobicity, as measured with the fluorescent probe dansyl-PE, was observed as a result of transfection of CHO cells with the mdr1 gene. However, the selected cell line, CHRC5, showed a decreased surface hydrophobicity. This decreased surface hydrophobicity was indicated by an 8 nm increase in the fluorescence emission of dansyl-PE in the CHRC5 cell line compared with the AB1. Both resistant cell lines showed an increase in the polarisation of the fluorescent probe, TMA-DPH in the plasma membranes corresponding to a 14% and a 24% change in fluorescence polarisation for the selected and transfected cell lines, respectively. This is indicative of reduced mobility of the acyl chains in the resistant cell lines. Both the CHRC5 and the transfected cell lines showed almost a 2-fold increase in the initial rate of membrane cycling. The membrane cycling could be inhibited by a known bilayer stabiliser, the N-carbobenzoxy-D-Phe-L-Phe-Gly. These results indicate that the properties of the plasma membrane from resistant cells are altered compared with their parental cell line.
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Affiliation(s)
- R Callaghan
- Department of Biochemistry, McMaster University Health Sciences Centre, Hamilton, Ontario, Canada
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Gil R, Callaghan R, Boix J, Pellin A, Llombart-Bosch A. Morphometric and cytophotometric nuclear analysis of altered hepatocyte foci induced by N-nitrosomorpholine (NNM) and aflatoxin B1 (AFB1) in liver of Wistar rats. Virchows Arch B Cell Pathol Incl Mol Pathol 1987; 54:341-9. [PMID: 2897742 DOI: 10.1007/bf02899232] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The progressive morphological changes in the liver during neoplastic transformation have been studied by histological, cytophotometric and morphometric methods in male Wistar rats treated with two carcinogens: N-nitrosomorpholine (NNM) and aflatoxin B1 (AFB1). Cytophotometric and morphometric analysis of hepatocyte nuclei using Feulgen-stained tissue sections were performed in morphologically normal hepatic parenchyma and in early preneoplastic foci composed of altered hepatocytes. Foci of clear cells, mixed cells and large basophilic cells possessed a ploidy distribution similar to the surrounding non-transformed parenchyma, while the small hyperbasophilic cell foci were predominantly diploid. These findings confirm that the foci composed of PAS-negative, small hyperbasophilic cells with an unique diploid content may represent one of the earliest stages in the neoplastic transformation.
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Affiliation(s)
- R Gil
- Department of Pathology, Medical School, University of Valencia, Spain
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