Blood Journal
Leading the way in experimental and clinical research in hematology

Stat3 signaling in acute myeloid leukemia: ligand-dependent and -independent activation and induction of apoptosis by a novel small-molecule Stat3 inhibitor

  1. Michele S. Redell1,
  2. Marcos J. Ruiz1,
  3. Todd A. Alonzo2,3,
  4. Robert B. Gerbing3, and
  5. David J. Tweardy4
  1. 1Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX;
  2. 2University of Southern California Keck School of Medicine, Los Angeles, CA;
  3. 3Children's Oncology Group, Arcadia, CA; and
  4. 4Department of Medicine, Baylor College of Medicine, Houston, TX


Acute myeloid leukemia (AML) is an aggressive malignancy with a relapse rate approaching 50%, despite aggressive chemotherapy. New therapies for AML are targeted at signal transduction pathways known to support blast survival, such as the Stat3 pathway. Aberrant activation of Stat3 has been demonstrated in many different malignancies, including AML, and this finding is frequently associated with more aggressive disease. The objectives of this study were: (1) to characterize Stat3 signaling patterns in AML cells lines and primary pediatric samples; and (2) to test the efficacy and potency of a novel Stat3 inhibitor in inducing apoptosis in AML cells. We found that Stat3 was constitutively activated in 6 of 7 AML cell lines and 6 of 18 primary pediatric AML samples. Moreover, constitutively phosphorylated Stat3 was frequent in samples with normal karyotype but uncommon in samples with t(8;21). Most cell lines and primary samples responded to G-CSF stimulation, although the sensitivity and magnitude of the response varied dramatically. Our novel small-molecule Stat3 inhibitor, C188-9, inhibited G-CSF–induced Stat3 phosphorylation, induced apoptosis in AML cell lines and primary samples, and inhibited AML blast colony formation with potencies in the low micromolar range. Therefore, Stat3 inhibition may be a valuable strategy for targeted therapies for AML.

  • Submitted April 16, 2010.
  • Accepted March 8, 2011.
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