title: Erythropoietin promotes resistance against the Abl tyrosine kinase inhibitor imatinib (STI571) in K562 human leukemia cells.
abstract: Chronic myeloid leukemia is characterized by the Philadelphia chromosome translocation that causes expression of Bcr-Abl, a deregulated tyrosine kinase. Imatinib mesylate (STI571, Gleevec), a therapeutically used inhibitor of Bcr-Abl, causes apoptosis of Bcr-Abl-positive cells. In the leukemia cell line K562, we observed spontaneous resistance to imatinib at very low frequencies when cells were exposed to the drug (1 micro M) for more than 4 weeks. Surprisingly, in the presence of erythropoietin (Epo), K562 cells were temporarily able to sustain proliferation in the presence of imatinib, and imatinib-resistant clones could be isolated with high frequencies. From such imatinib-resistant, Epo-dependent clones, sublines could be established that were resistant to imatinib in the absence of Epo. Mitogen-activated protein (MAP) kinase activity was inhibited by imatinib treatment but could be partially restored by Epo. Inhibition of MAP kinase or phosphatidylinositol 3-kinase blocked the protective effect of Epo. The data suggest that K562 cells acquire factor dependency under imatinib/Epo treatment, allowing them to escape from imatinib-induced, immediate cell death. This pool of cells provides the basis for the outgrowth of imatinib-resistant clones of unlimited proliferative capacity. Thus, Epo, an endogenous regulator of hematopoiesis, promotes the development of resistance to imatinib.
authors.affiliation: Institute of Pharmacology, University of Bern, Bern, Switzerland.
authors.forename: Karin M
authors.initials: KM
authors.lastname: Kirschner
authors.forename: Kurt
authors.initials: K
authors.lastname: Baltensperger
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004921:Erythropoietin / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology; D016044:Fusion Proteins, bcr-abl; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D000068877:Imatinib Mesylate; D007377:Interleukin-3 / Q000494:pharmacology; D020014:K562 Cells; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010879:Piperazines / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011743:Pyrimidines / Q000494:pharmacology*; D019089:Stem Cell Factor / Q000494:pharmacology; D013997:Time Factors
chemical_list: D001549:Benzamides; D002867:Chromones; D004791:Enzyme Inhibitors; D004921:Erythropoietin; D005419:Flavonoids; D016044:Fusion Proteins, bcr-abl; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D000068877:Imatinib Mesylate; D007377:Interleukin-3; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010879:Piperazines; D011505:Protein-Tyrosine Kinases; D011743:Pyrimidines; D019089:Stem Cell Factor; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one