title: Increased efflux of vincristine, but not of daunorubicin, associated with the murine multidrug resistance protein (MRP).
abstract: The multidrug resistance protein (MRP) is a membrane protein that mediates altered transport of cytotoxic drugs. Although MRP overexpression has been described in doxorubicin-selected human tumor cell lines, the murine PC-V10 and PC-V40 cell lines are members of the only reported series of vincristine-selected cell lines that overexpress mrp. Western blotting, using an antiserum developed against human MRP, demonstrated high-level expression of murine MRP primarily in the plasma membranes in each of the vincristine-selected cell lines. Only PC-V160, selected for high level resistance, demonstrated concomitant overexpression of the P-glycoprotein. As compared with parental cells, each of the drug-selected cell lines demonstrated an energy-dependent, decreased net accumulation of vincristine without any changes in the initial rates of vincristine influx. However, there was an enhanced rate of vincristine loss, 2.3-fold from the PC-V40 cell line and 3.9-fold from the PC-V160 cell line. Selective plasma membrane permeabilization with digitonin equalized vincristine accumulation among the parental, the PC-V40, and the PC-V160 cell lines. No intracellular pH differences were detected among the cell lines. Despite high-level MRP expression, daunorubicin accumulation and the rate of daunorubicin loss in the PC-V40 cells were the same as that observed in parental PC4 cells. Fluorescence microscopy demonstrated no difference in the pattern of subcellular daunorubicin accumulation between parental and PC-V40 cells. These studies demonstrate that murine MRP, overexpressed and found predominantly in the plasma membrane of vincristine-selected PC-V40 cells, is associated with an energy-dependent increased efflux of vincristine, but not with efflux or altered distribution of daunorubicin.
authors.affiliation: Center for Adaptation Genetics and Drug Resistance, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Slapak
authors.forename: R L
authors.initials: RL
authors.lastname: Martell
authors.forename: M
authors.initials: M
authors.lastname: Terashima
authors.forename: S B
authors.initials: SB
authors.lastname: Levy
mesh_terms: D019297:2,4-Dinitrophenol / Q000494:pharmacology; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics*; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics*; D001386:Azides / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003630:Daunorubicin / Q000493:pharmacokinetics*; D004072:Digitonin / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D051379:Mice; D019810:Sodium Azide; D013347:Subcellular Fractions / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology; D014750:Vincristine / Q000493:pharmacokinetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D000972:Antineoplastic Agents, Phytogenic; D001386:Azides; D014475:Uncoupling Agents; D014750:Vincristine; D019810:Sodium Azide; D004072:Digitonin; D019297:2,4-Dinitrophenol; D003630:Daunorubicin