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- Title
Enhanced BCR-ABL kinase inhibition does not result in increased inhibition of downstream signaling pathways or increased growth suppression in CML progenitors.
- Authors
Konig, H.; Holtz, M.; Modi, H.; Manley, P.; Holyoake, T. L.; Forman, S. J.; Bhatia, R.
- Abstract
The therapeutic success of imatinib in chronic myeloid leukemia (CML) is hampered by persistence of malignant stem cells. We investigated whether nilotinib, a more potent BCR-ABL kinase inhibitor could target CML primitive progenitors more effectively than imatinib. CML and normal progenitor cells were cultured with nilotinib or imatinib in growth factor supplemented medium. Nilotinib inhibited BCR-ABL kinase activity at lower concentrations than imatinib. Nilotinib inhibited mitogen-activated protein kinase (MAPK), AKT and STAT5 phosphorylation in CML CD34(+) cells in the absence of growth factors (GFs), but did not suppress AKT and STAT5 activity, and resulted in increased MAPK activity, in the presence of GFs. Nilotinib and imatinib resulted in similar suppression of CML primitive and committed progenitors in long-term culture-initiating cell and colony-forming cell assays. Inhibition of progenitor growth was related to marked reduction in proliferation, but only a modest increase in apoptosis. Nilotinib did not show increased efficacy in reducing nondividing CML progenitors compared with imatinib. These results indicate that more potent tyrosine kinase inhibitors by themselves will not be more effective in eliminating CML progenitors than imatinib and that additional mechanism required for maintenance of malignant stem cells need to be identified to improve targeting of leukemia stem cells.
- Subjects
PROTEIN kinases; TREATMENT of chronic myeloid leukemia; DRUG therapy; IMATINIB; STEM cells; GROWTH factors; PHOSPHORYLATION; APOPTOSIS; PROTEIN-tyrosine kinase inhibitors; THERAPEUTICS
- Publication
Leukemia (08876924), 2008, Vol 22, Issue 4, p748
- ISSN
0887-6924
- Publication type
journal article
- DOI
10.1038/sj.leu.2405086