title: Characteristics of dasatinib- and imatinib-resistant chronic myelogenous leukemia cells.
abstract: OBJECTIVE
  Although dual src-family kinase/BCR/ABL inhibitor, dasatinib (BMS-354825), provides therapeutic advantages to imatinib-resistant cells, the mechanism of dasatinib resistance was not fully known.
  
  
  METHODS
  We used TF-1 BCR/ABL cells, by introducing the BCR/ABL gene into a leukemia cell line, TF-1 and K562, and established dasatinib- (BMS-R) and imatinib-resistant (IM-R) cells. We characterized chronic myelogenous leukemia drug-resistant cells and examined intracellular signaling.
  
  
  RESULTS
  The IC(50) of dasatinib was 0.75 nmol/L (TF-1 BCR/ABL), 1 nmol/L (K562), 7.5 nmol/L (TF-1 BCR/ABL IM-R), 10 nmol/L (K562 IM-R), 15 micromol/L (TF-1 BCR/ABL BMS-R), and 25 micromol/L (K562 BMS-R). The number of BCR/ABL copies in resistant cell lines was the same as the parental cell line by fluorescence in situ hybridization analysis. There was no mutation in Abl kinase. We found that protein levels of BCR/ABL were reduced in dasatinib-resistant cell lines. BCR/ABL protein was increased by treatment of an ubiquitin inhibitor. The Src kinase, Lck, as well as mitogen-activated protein kinase and Akt were activated, but p21(WAF), phosphatase and tensin homologue was reduced in K562 BMS-R cells. Removal of dasatinib from the culture medium of K562 BMS-R cells led to apoptosis, and activated caspase 3 and poly (ADP-ribose) polymerase.
  
  
  CONCLUSIONS
  These results suggest that the expression and protein activation signatures identified in this study provide insight into the mechanism of resistance to dasatinib and imatinib and may be of therapeutic chronic myelogenous leukemia value clinically.
authors.affiliation: First Department of Internal Medicine, Tokyo Medical University, 6-7-1 Nishi-shinjuku, Shinjuku-ku, Tokyo, Japan. okabe@tokyo-med.ac.jp
authors.forename: Seiichi
authors.initials: S
authors.lastname: Okabe
authors.forename: Tetsuzo
authors.initials: T
authors.lastname: Tauchi
authors.forename: Kazuma
authors.initials: K
authors.lastname: Ohyashiki
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001549:Benzamides; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D000069439:Dasatinib; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D006801:Humans; D000068877:Imatinib Mesylate; D020128:Inhibitory Concentration 50; D020014:K562 Cells; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy*; D010879:Piperazines / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D010879:Piperazines; D011743:Pyrimidines; D013844:Thiazoles; D000068877:Imatinib Mesylate; D011065:Poly(ADP-ribose) Polymerases; D053148:Caspase 3; D000069439:Dasatinib