title: 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.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Ruud
authors.initials: R
authors.lastname: Oerlemans
authors.forename: Joost
authors.initials: J
authors.lastname: van der Heijden
authors.forename: Josefien
authors.initials: J
authors.lastname: Vink
authors.forename: Ben A C
authors.initials: BA
authors.lastname: Dijkmans
authors.forename: Gertjan J L
authors.initials: GJ
authors.lastname: Kaspers
authors.forename: Willem F
authors.initials: WF
authors.lastname: Lems
authors.forename: George L
authors.initials: GL
authors.lastname: Scheffer
authors.forename: Ilan
authors.initials: I
authors.lastname: Ifergan
authors.forename: Rik J
authors.initials: RJ
authors.lastname: Scheper
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Cloos
authors.forename: Yehuda G
authors.initials: YG
authors.lastname: Assaraf
authors.forename: Gerrit
authors.initials: G
authors.lastname: Jansen
mesh_terms: D018501:Antirheumatic Agents / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D002738:Chloroquine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000378:metabolism*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism
chemical_list: D018501:Antirheumatic Agents; D002738:Chloroquine; D005938:Glucocorticoids; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C421109:multidrug resistance-associated protein 1