title: Biophysical characterization of MDR breast cancer cell lines reveals the cytoplasm is critical in determining drug sensitivity.
abstract: Dielectrophoresis (DEP) was used to examine a panel of MCF-7 cell lines comprising parental MCF-7 cells and MDR derivatives: MCF-7TaxR (paclitaxel-resistant, P-glycoprotein (P-gp) positive), MCF-7DoxR (doxorubicin-resistant MRP2 positive) plus MCF-7MDR1 (MDR1 transfected, P-gp positive). MCF-7DoxR and MCF-7MDR1 were broadly cross-resistant to natural product anticancer agents, whereas MCF-7TaxR cells were not, contrary to P-gp expression. Whilst DEP revealed modest membrane changes in MDR sub-lines, we saw significant changes in their cytoplasmic conductivity: MCF-7TaxR<MCF-7<MCF-7MDR1<MCF-7DoxR (range 0.14-0.40 S/m). Cytoplasmic conductivity is affected by the movement of molecules e.g. as in intracellular trafficking MCF-7TaxR showed a reduced membrane potential, whereas MCF-7DoxR and MCF-7MDR1 showed an increase. Thus, altered membrane potential is associated with an MDR phenotype, but in a complex manner. DEP data suggest a model whereby relative increases in cytoplasmic conductivity are correlated with MDR, whilst relative decreases equate with a sensitised phenotype e.g. MCF-7TaxR. Moreover, extent of anthracycline accumulation was inversely related to cytoplasmic conductivity. These data are representative of a model where drug sensitivity is associated with low ionic conductance (reduced cellular trafficking and ion transport) and substantial anthracycline accumulation. For classical MDR i.e. MCF-7MDR1, we saw the reverse picture. Thus, the drug resistance phenotypes of this panel of MCF-7 lines can be delineated by assessment of cytoplasmic biophysical properties using DEP.
authors.affiliation: Division of Oncology, Postgraduate Medical School, School, University of Surrey, Guildford, Surrey GU2 7WG, UK. h.coley@surrey.ac.uk
authors.forename: Helen M
authors.initials: HM
authors.lastname: Coley
authors.forename: Fatima H
authors.initials: FH
authors.lastname: Labeed
authors.forename: Hilary
authors.initials: H
authors.lastname: Thomas
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hughes
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D018943:Anthracyclines / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002232:Carbocyanines; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002945:Cisplatin / Q000494:pharmacology; D003078:Colchicine / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects* / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004586:Electrophoresis / Q000379:methods; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005456:Fluorescent Dyes; D006801:Humans; D020128:Inhibitory Concentration 50; D008564:Membrane Potentials / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D017239:Paclitaxel / Q000494:pharmacology; D010641:Phenotype
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D018943:Anthracyclines; D000970:Antineoplastic Agents; D002232:Carbocyanines; D002945:Cisplatin; D003078:Colchicine; D004317:Doxorubicin; D005047:Etoposide; D005456:Fluorescent Dyes; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D017239:Paclitaxel; C000715087:ABCC2 protein, human; C116614:ABCG2 protein, human; C018528:3,3'-dipentyl-2,2'-oxacarbocyanine; C421109:multidrug resistance-associated protein 1