Nonproliferating CML CD34+ progenitors are resistant to apoptosis induced by a wide range of proapoptotic stimuli

Leukemia. 2005 Jun;19(6):1034-41. doi: 10.1038/sj.leu.2403724.


Imatinib mesylate, a Bcr-Abl kinase inhibitor, has been very successful in the treatment of chronic myelogenous leukemia (CML). However, the majority of patients achieving cytogenetic remissions with imatinib treatment have molecular evidence of persistent disease, and residual BCR/ABL(+) progenitors can be detected. There is a need to develop new approaches that enhance elimination of malignant progenitors in imatinib-treated patients. Here we show that CML CD34(+) progenitors are sensitive to several apoptosis-inducing stimuli including the chemotherapeutic agents Ara-C and VP-16, radiation, arsenic trioxide, ceramide, growth factor withdrawal, and the death receptor activators TNFalpha and TRAIL. Bcr-Abl kinase inhibition by imatinib did not enhance sensitivity of CML progenitors to Ara-C, VP-16, ceramide, radiation or TRAIL-induced apoptosis but did enhance arsenic and TNFalpha-induced apoptosis. We further demonstrate that apoptosis was restricted to dividing cells, whereas nonproliferating BCR/ABL(+) CD34(+) cells were resistant to apoptosis induced by imatinib, Ara-C or arsenic, either alone or in combination. Resistance of quiescent CML progenitors to imatinib-induced apoptosis could contribute to persistence of residual malignant progenitors in imatinib-treated patients. Combination treatment with Ara-C or arsenic may not enhance targeting of nonproliferating CML progenitors. The assay described here may be useful for identifying agents targeting quiescent CML progenitors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Aged
  • Antigens, CD34 / metabolism
  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Benzamides
  • Cell Division / drug effects
  • Cell Division / physiology
  • Female
  • Fusion Proteins, bcr-abl / antagonists & inhibitors
  • Fusion Proteins, bcr-abl / genetics
  • Gene Expression Regulation, Leukemic / drug effects
  • Hematopoietic Stem Cells / cytology
  • Hematopoietic Stem Cells / drug effects*
  • Hematopoietic Stem Cells / metabolism
  • Humans
  • Imatinib Mesylate
  • In Vitro Techniques
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
  • Male
  • Middle Aged
  • Piperazines / pharmacology*
  • Pyrimidines / pharmacology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology


  • Antigens, CD34
  • Antineoplastic Agents
  • Benzamides
  • Piperazines
  • Pyrimidines
  • Imatinib Mesylate
  • Fusion Proteins, bcr-abl