Multidrug-resistant tumor cells remain sensitive to a recombinant interleukin-4-Pseudomonas exotoxin, except when overexpressing the multidrug resistance protein MRP1

Clin Cancer Res. 2003 Oct 15;9(13):5009-17.


Tumor cells may become resistant to conventional anticancer drugs through the occurrence of transmembrane transporter proteins such as P-glycoprotein (ABCB1), breast cancer resistance protein (ABCG2), or members of the multidrug resistance-associated protein family (MRP1-MRP5; ABCC1-ABCC5). In this report, we studied whether tumor cells that are cytostatic drug resistant because of overexpression of one of the above mentioned proteins are sensitive to a new anticancer agent, interleukin-4 toxin (IL-4 toxin). IL-4 toxin is a fusion protein composed of circularly permuted IL-4 and a truncated form of Pseudomonas exotoxin (PE) [IL-4(38-37)-PE38KDEL]. Ninety-six-h cytotoxicity assays and 10-day clonogenic assays showed that drug-selected multidrug resistant (MDR) tumor cells that overexpress P-glycoprotein or breast cancer resistance proteins are still sensitive to IL-4 toxin. Also, tumor cells transfected with cDNA for MRP2-5 showed no resistance, or marginal resistance, only to the toxin as compared with the parent cells. In contrast, MRP1-overexpressing cells, both drug selected and MRP1 transfected, are clearly resistant to IL-4 toxin with resistance factors of 4.3 to 8.4. MRP1-overexpressing cells were not resistant to PE itself. IL-4 toxin resistance in MRP1-overexpressing cells could be reversed by the MRP1 inhibitors probenecid or MK571 and were not affected by glutathione depletion by DL-buthionine-S,R-sulfoximine. In a transport assay using plasma membrane vesicles prepared from MRP1-overexpressing cells, IL-4 toxin and IL-4, but not PE, inhibited the translocation of the known MRP1 substrate 17beta-estradiol 17-(beta-D-glucuronide) (E(2)17betaG). These data suggest that MRP1-overexpressing cells are resistant to IL-4 toxin because of extrusion of this agent by MRP1. Still, the results of this study demonstrate that IL-4 toxin effectively kills most MDR tumor cells and, therefore, represents a promising anticancer drug.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism
  • Antimetabolites, Antineoplastic / pharmacology
  • Antineoplastic Agents / pharmacology
  • Bacterial Toxins / chemistry
  • Bacterial Toxins / metabolism
  • Buthionine Sulfoximine / pharmacology
  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • DNA, Complementary / metabolism
  • Dose-Response Relationship, Drug
  • Drug Resistance, Multiple*
  • Drug Resistance, Neoplasm*
  • Exotoxins / chemistry
  • Exotoxins / metabolism
  • Exotoxins / physiology*
  • Humans
  • Interleukin-4 / chemistry
  • Interleukin-4 / metabolism*
  • Interleukin-4 / physiology*
  • Leukotriene Antagonists / pharmacology
  • Multidrug Resistance-Associated Proteins / metabolism*
  • Probenecid / pharmacology
  • Propionates / pharmacology
  • Quinolines / pharmacology
  • Recombinant Proteins / metabolism*
  • Transfection
  • Uricosuric Agents / pharmacology


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antimetabolites, Antineoplastic
  • Antineoplastic Agents
  • Bacterial Toxins
  • DNA, Complementary
  • Exotoxins
  • Leukotriene Antagonists
  • Multidrug Resistance-Associated Proteins
  • Propionates
  • Quinolines
  • Recombinant Proteins
  • Uricosuric Agents
  • interleukin-4-Pseudomonas exotoxin
  • Interleukin-4
  • Buthionine Sulfoximine
  • verlukast
  • Probenecid
  • multidrug resistance-associated protein 1