title: Multidrug resistance protein 1 (MRP1, ABCC1) mediates resistance to mitoxantrone via glutathione-dependent drug efflux.
abstract: Based upon several previous reports, no consistent relationship between multidrug resistance protein 1 (MRP1, ABCC1) expression and cellular sensitivity to mitoxantrone (MX) toxicity can be ascertained; thus, the role of MRP1 in MX resistance remains controversial. The present study, using paired parental, MRP1-poor, and transduced MRP1-overexpressing MCF7 cells, unequivocally demonstrates that MRP1 confers resistance to MX cytotoxicity and that resistance is associated with reduced cellular accumulation of MX. This MRP1-associated reduced accumulation of MX was partially reversed by treatment of cells with 50 microM MK571 [3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid]-an MRP inhibitor that increased MX accumulation in MRP1-expressing MCF7 cells but had no effect on MRP-poor MCF7 cells. Moreover, in vitro experiments using inside-out membrane vesicles show that MRP1 supports ATP-dependent, osmotically sensitive uptake of MX. Unlike ABCG2 (breast cancer resistance protein, mitoxantrone-resistant protein), MRP1-mediated MX transport is dependent upon the presence of glutathione or its S-methyl analog. In addition, MX stimulates transport of [3H]glutathione. Together, these data are consistent with the interpretation that MX efflux by MRP1 involves cotransport of MX and glutathione. The results suggest that MRP1-like the alternative MX transporters ABCG2 and ABCB1 (MDR1, P-glycoprotein)-can significantly influence tumor cell sensitivity to and pharmacological disposition of MX.
authors.affiliation: Department of Biochemistry, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA. cmorrow@wfubmc.edu
authors.forename: Charles S
authors.initials: CS
authors.lastname: Morrow
authors.forename: Christina
authors.initials: C
authors.lastname: Peklak-Scott
authors.forename: Bimjhana
authors.initials: B
authors.lastname: Bishwokarma
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Kute
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Smitherman
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Townsend
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D008942:Mitoxantrone / Q000493:pharmacokinetics / Q000494:pharmacology*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000502:physiology*; D011422:Propionates / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology
chemical_list: D000255:Adenosine Triphosphate; D000970:Antineoplastic Agents; D005978:Glutathione; D008942:Mitoxantrone; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D011422:Propionates; D011804:Quinolines; C059141:verlukast; C421109:multidrug resistance-associated protein 1