title: Effects of the Bcr/abl kinase inhibitors STI571 and adaphostin (NSC 680410) on chronic myelogenous leukemia cells in vitro.
abstract: The adenosine triphosphate binding-site-directed agent STI571 and the tyrphostin adaphostin are undergoing evaluation as bcr/abl kinase inhibitors. The current study compared the effects of these agents on the survival of K562 cells, bcr/abl-transduced FDC-P1 cells, and myeloid progenitors from patients with chronic myelogenous leukemia (CML) compared with healthy donors. Treatment of K562 cells with 10 microM adaphostin resulted in decreased p210(bcr/abl) polypeptide levels in the first 6 hours, followed by caspase activation and accumulation of apoptotic cells in less than 12 hours. By 24 hours, 90% of the cells were apoptotic and unable to form colonies. In contrast, 20 microM STI571 caused rapid inhibition of bcr/abl autophosphorylation without p210(bcr/abl) degradation. Although this was followed by the inhibition of Stat5 phosphorylation and the down-regulation of Bcl-x(L) and Mcl-1, only 7% +/- 3% and 25% +/- 9% of cells were apoptotic at 16 and 24 hours, respectively. Instead, the cytotoxic effects of STI571 became more pronounced with prolonged exposure, with IC90 values greater than 20 microM and 1.0 +/- 0.6 microM after 24 and 48 hours, respectively. Consistent with these results, 24-hour adaphostin exposure inhibited CML granulocyte colony-forming units (CFU-G) (median IC50, 12 microM) but not normal CFU-G (median IC50, greater than 20 microM), whereas 24-hour STI571 treatment had no effect on CML or normal CFU-G. Additional experiments revealed that STI571-resistant K562 cells remained sensitive to adaphostin. Moreover, the combination of STI571 + adaphostin induced more cytotoxicity in K562 cells and in CML CFU-G than either agent alone did. Collectively, these results identify adaphostin as a mechanistically distinct CML-selective agent that retains activity in STI571-resistant cell lines.
authors.affiliation: Division of Hematology, Department of Internal Medicine, Mayo Clinic, Rochester, MN 55901, USA.
authors.forename: Benjamin M F
authors.initials: BM
authors.lastname: Mow
authors.forename: Joya
authors.initials: J
authors.lastname: Chandra
authors.forename: Phyllis A
authors.initials: PA
authors.lastname: Svingen
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Hallgren
authors.forename: Ellen
authors.initials: E
authors.lastname: Weisberg
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kottke
authors.forename: Ven L
authors.initials: VL
authors.lastname: Narayanan
authors.forename: Mark R
authors.initials: MR
authors.lastname: Litzow
authors.forename: James D
authors.initials: JD
authors.lastname: Griffin
authors.forename: Edward A
authors.initials: EA
authors.lastname: Sausville
authors.forename: Ayalew
authors.initials: A
authors.lastname: Tefferi
authors.forename: Scott H
authors.initials: SH
authors.lastname: Kaufmann
mesh_terms: D000218:Adamantane / Q000031:analogs & derivatives / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism; D004357:Drug Synergism; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016044:Fusion Proteins, bcr-abl / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology*; D000068877:Imatinib Mesylate; D020014:K562 Cells / Q000187:drug effects* / Q000201:enzymology; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000201:enzymology / Q000235:genetics / Q000473:pathology*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011506:Proteins / Q000235:genetics; D011743:Pyrimidines / Q000494:pharmacology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015843:Serpins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects; D014410:Tumor Stem Cell Assay; D014764:Viral Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein
chemical_list: D001549:Benzamides; D004791:Enzyme Inhibitors; D006873:Hydroquinones; C404397:NSC 680410; D010879:Piperazines; D011506:Proteins; D011743:Pyrimidines; D011993:Recombinant Fusion Proteins; D015843:Serpins; D014764:Viral Proteins; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D000068877:Imatinib Mesylate; C074641:interleukin-1beta-converting enzyme inhibitor; D016044:Fusion Proteins, bcr-abl; C506433:CASP9 protein, human; D053453:Caspase 9; D020169:Caspases; D000218:Adamantane