Acquired resistance to chloroquine in human CEM T cells is mediated by multidrug resistance-associated protein 1 and provokes high levels of cross-resistance to glucocorticoids

Ruud Oerlemans, Joost van der Heijden, Josefien Vink, Ben A C Dijkmans, Gertjan J L Kaspers, Willem F Lems, George L Scheffer, Ilan Ifergan, Rik J Scheper, Jacqueline Cloos, Yehuda G Assaraf, Gerrit Jansen

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OBJECTIVE: To explore the onset and molecular mechanism of resistance to the antimalarial disease-modifying antirheumatic drug (DMARD) chloroquine (CQ) in human CEM T cells.

METHODS: Human CEM cells were used as an in vitro model system to study the development of CQ resistance by growing cells in stepwise increasing concentrations of CQ.

RESULTS: Over a period of 6 months, CEM cell lines developed 4-5-fold resistance to CQ. CQ resistance was associated with the specific overexpression of multidrug resistance-associated protein 1 (MRP-1), an ATP-driven drug efflux pump. This was illustrated by 1) overexpression of MRP-1 by Western blotting and 2) the complete reversal of CQ resistance by the MRP-1 transport inhibitors MK571 and probenecid. Importantly, CQ-resistant CEM cells retained full sensitivity to other DMARDs, including methotrexate, leflunomide, cyclosporin A, and sulfasalazine, but exhibited a high level of cross-resistance (>1,000-fold) to the glucocorticoid dexamethasone. The mechanistic basis for the latter was associated with aberrant signaling via the cAMP-protein kinase A pathway, since the cAMP-inducing agent forskolin reversed dexamethasone resistance. Finally, CQ-resistant CEM cells displayed a markedly reduced capacity to release proinflammatory cytokines (tumor necrosis factor alpha) and chemokines (interleukin-8).

CONCLUSION: Induction of overexpression of the multidrug resistance efflux transporter MRP-1 can emerge after long-term exposure to CQ and results in CQ resistance and collateral resistance to dexamethasone. These findings warrant further detailed investigations into the possible role of MRP-1 and other members of the superfamily of drug efflux pumps in diminishing the efficacy of DMARDs in rheumatoid arthritis treatment.

Original languageEnglish
Pages (from-to)557-568
Number of pages12
JournalArthritis & Rheumatism
Issue number2
Publication statusPublished - Feb 2006


  • Antirheumatic Agents/pharmacology
  • Blotting, Western
  • Cell Line
  • Chloroquine/pharmacology
  • Dose-Response Relationship, Drug
  • Drug Resistance, Multiple/drug effects
  • Glucocorticoids/pharmacology
  • Humans
  • Multidrug Resistance-Associated Proteins/metabolism
  • T-Lymphocytes/drug effects

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