Blood Journal
Leading the way in experimental and clinical research in hematology

Low-dose arsenic trioxide sensitizes glucocorticoid-resistant acute lymphoblastic leukemia cells to dexamethasone via an Akt-dependent pathway

  1. Beat C. Bornhauser1,
  2. Laura Bonapace1,
  3. Dan Lindholm2,
  4. Rodrigo Martinez2,
  5. Gunnar Cario3,
  6. Martin Schrappe3,
  7. Felix K. Niggli1,
  8. Beat W. Schäfer1, and
  9. Jean-Pierre Bourquin1
  1. 1Department of Oncology, Children's Hospital, University of Zurich, Zurich, Switzerland;
  2. 2Department of Neuroscience, Biomedical Center, University of Uppsala, Uppsala, Sweden;
  3. 3Department of Pediatrics, University Hospital Schleswig-Holstein, Campus Kiel, Kiel, Germany

Abstract

Incorporation of apoptosis-inducing agents into current therapeutic regimens is an attractive strategy to improve treatment for drug-resistant leukemia. We tested the potential of arsenic trioxide (ATO) to restore the response to dexamethasone in glucocorticoid (GC)–resistant acute lymphoblastic leukemia (ALL). Low-dose ATO markedly increased in vitro GC sensitivity of ALL cells from T-cell and precursor B-cell ALL patients with poor in vivo response to prednisone. In GC-resistant cell lines, this effect was mediated, at least in part, by inhibition of Akt and affecting downstream Akt targets such as Bad, a proapoptotic Bcl-2 family member, and the X-linked inhibitor of apoptosis protein (XIAP). Combination of ATO and dexamethasone resulted in increased Bad and rapid down-regulation of XIAP, while levels of the antiapoptotic regulator Mcl-1 remained unchanged. Expression of dominant-active Akt, reduction of Bad expression by RNA interference, or overexpression of XIAP abrogated the sensitizing effect of ATO. The inhibitory effect of XIAP overexpression was reduced when the Akt phosphorylation site was mutated (XIAP-S87A). These data suggest that the combination of ATO and glucocorticoids could be advantageous in GC-resistant ALL and reveal additional targets for the evaluation of new antileukemic agents.

  • Submitted December 1, 2006.
  • Accepted May 24, 2007.
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