Synergistic activity of imatinib and 17-AAG in imatinib-resistant CML cells overexpressing BCR-ABL--Inhibition of P-glycoprotein function by 17-AAG

Leukemia. 2005 Jul;19(7):1198-206. doi: 10.1038/sj.leu.2403764.


Overexpression of BCR-ABL and P-glycoprotein (Pgp) are two of the known mechanisms of imatinib resistance. As combination therapy may allow to overcome drug resistance, we investigated the effect of combination treatment with imatinib and 17-allylamino-17-demethoxygeldanamycin (17-AAG), a heat-shock protein 90 (Hsp90) inhibitor, on different imatinib-sensitive and imatinib-resistant CML cell lines. In imatinib-sensitive cells, combination index (CI) values obtained using the method of Chou and Talalay indicated additive (CI=1) or marginally antagonistic (CI>1) effects following simultaneous treatment with imatinib and 17-AAG. In imatinib-resistant cells both drugs acted synergistically (CI<1). In primary chronic-phase CML cells additive or synergistic effects of the combination of imatinib plus 17-AAG were discernible. Annexin V/propidium iodide staining showed that the activity of imatinib plus 17-AAG is mediated by apoptosis. Combination treatment with imatinib plus 17-AAG was more effective in reducing the BCR-ABL protein level than 17-AAG alone. Monotherapy with 17-AAG decreased P-glycoprotein activity, which may increase intracellular imatinib levels and contribute to the sensitization of CML cells to imatinib. The results suggest that combination of imatinib and 17-AAG may be useful to overcome imatinib resistance in a clinical setting.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / drug effects*
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / physiology
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Apoptosis / drug effects
  • Benzamides
  • Benzoquinones
  • Cell Proliferation / drug effects
  • Drug Synergism
  • Fusion Proteins, bcr-abl / biosynthesis*
  • Fusion Proteins, bcr-abl / genetics
  • Gene Expression Regulation, Leukemic / drug effects
  • Humans
  • Imatinib Mesylate
  • In Situ Hybridization, Fluorescence
  • Lactams, Macrocyclic
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / genetics
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
  • Phosphorylation
  • Piperazines / pharmacology*
  • Protein-Tyrosine Kinases / analysis
  • Protein-Tyrosine Kinases / biosynthesis*
  • Pyrimidines / pharmacology*
  • RNA, Messenger / genetics
  • Rifabutin / analogs & derivatives*
  • Rifabutin / pharmacology
  • Tumor Stem Cell Assay


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Benzamides
  • Benzoquinones
  • Lactams, Macrocyclic
  • Piperazines
  • Pyrimidines
  • RNA, Messenger
  • Rifabutin
  • tanespimycin
  • Imatinib Mesylate
  • Protein-Tyrosine Kinases
  • Fusion Proteins, bcr-abl