Multidrug resistance protein-mediated transport of chlorambucil and melphalan conjugated to glutathione

Br J Cancer. 1998;77(2):201-9. doi: 10.1038/bjc.1998.34.


The human multidrug resistance protein (MRP1) confers resistance of cells to a number of different cytostatic drugs and functions as an export pump for glutathione S-conjugates, glucuronides and other amphiphilic anions. The present study details for the first time MRP1-mediated ATP-dependent transport of various glutathione S-conjugates of the bifunctional alkylating agents chlorambucil and melphalan. In membrane vesicles prepared from cells expressing recombinant MRP1, the conjugates were transported at rates in the following order: monoglutathionyl chlorambucil > bisglutathionyl chlorambucil > monohydroxy monoglutathionyl chlorambucil and monoglutathionyl melphalan > monohydroxy monoglutathionyl melphalan. In addition, we show that membranes from chlorambucil-resistant GST-alpha-overexpressing CHO cells as well as from their parental cells express the hamster homologue of MRP1. With both CHO cell membrane preparations, we observed ATP-dependent transport of monoglutathionyl chlorambucil and of leukotriene C4, a glutathione S-conjugate and high-affinity substrate of MRP1. The transport rates measured in the resistant cells were only two- to three-fold higher than those measured in the control cells. These results together with cytotoxicity assays comparing MRP1-overexpressing cell pairs with the CHO cell pair indicate that, although MRP1-mediated transport is active, it may not be the rate-limiting step in chlorambucil resistance in these cell lines.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antineoplastic Agents, Alkylating / metabolism*
  • Biological Transport, Active
  • Buthionine Sulfoximine / pharmacology
  • CHO Cells
  • Cell Membrane / metabolism
  • Chlorambucil / metabolism*
  • Cricetinae
  • DNA-Binding Proteins / metabolism*
  • Drug Resistance
  • Glutathione / analogs & derivatives*
  • Glutathione / metabolism
  • HeLa Cells
  • Humans
  • Leukotriene C4 / metabolism
  • Mass Spectrometry / methods
  • Melphalan / metabolism*
  • Molecular Sequence Data
  • Multidrug Resistance-Associated Proteins*
  • MutS Homolog 3 Protein
  • Sequence Alignment
  • Tumor Cells, Cultured


  • Antineoplastic Agents, Alkylating
  • DNA-Binding Proteins
  • MSH3 protein, human
  • Multidrug Resistance-Associated Proteins
  • MutS Homolog 3 Protein
  • Chlorambucil
  • Leukotriene C4
  • Buthionine Sulfoximine
  • Glutathione
  • Melphalan
  • multidrug resistance-associated protein 1