The antiangiogenic protein kinase inhibitors SU5416 and SU6668 inhibit the SCF receptor (c-kit) in a human myeloid leukemia cell line and in acute myeloid leukemia blasts.
SU5416 and SU6668 are potent antiangiogenic small-molecule inhibitors of receptor tyrosine kinases, including those of the vascular endothelial growth factor and platelet-derived growth factor receptor families. The stem cell factor (SCF) receptor, c-kit, is structurally related to these receptors and, although not expressed on mature peripheral blood cells, is expressed in leukemic blasts derived from 60% to 80% of acute myeloid leukemia (AML) patients. The c-kit kinase inhibitory activity of SU5416 and SU6668 was evaluated in MO7E cells, a human myeloid leukemia cell line. Tyrosine autophosphorylation of the receptor, induced by SCF, was inhibited in these cells by SU5416 and SU6668 in a dose-dependent manner (inhibitory concentration of 50% [IC(50)] 0.1-1 microM). Inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, a signaling event downstream of c-kit activation, was also inhibited in a dose-dependent manner. Both compounds also inhibited SCF-induced proliferation of MO7E cells (IC(50) 0.1 microM for SU5416; 0.29 microM for SU6668). Furthermore, both SU5416 and SU6668 induced apoptosis in a dose- and time-dependent manner as measured by the increase in activated caspase-3 and the enhanced cleavage of its substrate poly(ADP-ribose) polymerase. These findings with MO7E cells were extended to leukemic blasts from c-kit(+) patients. In patient blasts, both SU5416 and SU6668 inhibited SCF-induced phosphorylation of c-kit and ERK1/2 and induced apoptosis. These studies indicate that SU5416 and SU6668 inhibit biologic functions of c-kit in addition to exhibiting antiangiogenic properties and suggest that the combination of these activities may provide a novel therapeutic approach for the treatment of AML.
Smolich
B D
BD
Preclinical Therapeutics, Sugen, South San Francisco, CA 94080, USA. beverly-smolich@sugen.com
Yuen
H A
HA
West
K A
KA
Giles
F J
FJ
Albitar
M
M
Cherrington
J M
JM
D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007951:Leukemia, Myeloid / Q000188:drug therapy / Q000473:pathology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000078183:Oxindoles; D010766:Phosphorylation / Q000187:drug effects; D011422:Propionates; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D019009:Proto-Oncogene Proteins c-kit / Q000187:drug effects*; D011758:Pyrroles / Q000494:pharmacology; D019089:Stem Cell Factor / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000187:drug effects
D020533:Angiogenesis Inhibitors; D007211:Indoles; D000078183:Oxindoles; D011422:Propionates; D011758:Pyrroles; D019089:Stem Cell Factor; C116890:Semaxinib; C412603:orantinib; D011505:Protein-Tyrosine Kinases; D019009:Proto-Oncogene Proteins c-kit; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases