Journal of the National Cancer Institute Advance Access originally published online on January 29, 2008
JNCI Journal of the National Cancer Institute 2008 100(3):184-198; doi:10.1093/jnci/djm328
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© The Author 2008. Published by Oxford University Press.
ARTICLES |
Mutant FLT3: A Direct Target of Sorafenib in Acute Myelogenous Leukemia
Affiliations of authors: Section of Molecular Hematology and Therapy, Department of Stem Cell Transplantation and Cellular Therapy (WZ, MK, YxS, TM, XL, MA), and Leukemia Department (DH, ZE, AQC, JC, MA), The University of Texas M. D. Anderson Cancer Center, Houston, TX; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD (DS)
Correspondence to: Michael Andreeff, MD, PhD, Section of Molecular Hematology and Therapy, Department of Stem Cell Transplantation and Cellular Therapy, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd, Unit 448, Houston, TX 77030 (e-mail: mandreef{at}mdanderson.org).
Background: Internal tandem duplication (ITD) mutations in the juxtamembrane domain–coding sequence of the Fms-like tyrosine kinase 3 (FLT3) gene have been identified in 30% of acute myeloid leukemia (AML) patients and are associated with a poor prognosis. The kinase inhibitor sorafenib induces growth arrest and apoptosis at much lower concentrations in AML cell lines that harbor FLT3-ITD mutations than in AML cell lines with wild-type FLT3.
Methods: The antileukemic activity of sorafenib was investigated in isogenic murine Ba/F3 AML cell lines that expressed mutant (ITD, D835G, and D835Y) or wild-type human FLT3, in primary human AML cells, and in a mouse leukemia xenograft model. Effects of sorafenib on apoptosis and signaling in AML cell lines were investigated by flow cytometry and immunoblot analysis, respectively, and the in vivo effects were determined by monitoring the survival of leukemia xenograft–bearing mice treated with sorafenib (groups of 15 mice). In a phase 1 clinical trial, 16 patients with refractory or relapsed AML were treated with sorafenib on different dose schedules. We determined their FLT3 mutation status by a polymerase chain reaction assay and analyzed clinical responses by standard criteria. All statistical tests were two-sided.
Results: Sorafenib was 1000- to 3000-fold more effective in inducing growth arrest and apoptosis in Ba/F3 cells with FLT3-ITD or D835G mutations than in Ba/F3 cells with FLT3-D835Y mutant or wild-type FLT3 and inhibited the phosphorylation of tyrosine residues in ITD mutant but not wild-type FLT3 protein. In a mouse model, sorafenib decreased the leukemia burden and prolonged survival (median survival in the sorafenib-treated group vs the vehicle-treated group = 36.5 vs 16 days, difference = 20.5 days, 95% confidence interval = 20.3 to 21.3 days; P = .0018). Sorafenib reduced the percentage of leukemia blasts in the peripheral blood and the bone marrow of AML patients with FLT3-ITD (median percentages before and after sorafenib: 81% vs 7.5% [P = .016] and 75.5% vs 34% [P = .05], respectively) but not in patients without this mutation.
Conclusion: Sorafenib may have therapeutic efficacy in AML patients whose cells harbor FLT3-ITD mutations.
| CONTEXT AND CAVEATS Prior knowledge The kinase inhibitor sorafenib induces growth arrest and apoptosis at much lower concentrations in acute myeloid leukemia (AML) cell lines that harbor Fms-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD) mutations than in AML cell lines with wild-type FLT3. Study design In vitro assays in isogenic murine AML cell lines that expressed mutant (ITD, D835G, or D835Y) or wild-type human FLT3 and in primary human AML cells, in vivo mouse leukemia xenograft model, and correlative studies in an ongoing phase 1 trial of the therapeutic efficacy of sorafenib in 16 AML patients with known FLT3 gene mutation status. Contribution Sorafenib preferentially induced growth arrest and apoptosis of FLT3-ITD mutant murine AML cells, prolonged survival of mice bearing FLT3-ITD xenografts, and reduced the percentage of leukemia blasts in the peripheral blood and bone marrow of AML patients harboring FLT3-ITD mutations. Implications Sorafenib may have therapeutic efficacy in AML patients whose cells harbor FLT3-ITD mutations. Limitations Discontinuation of sorafenib administration led to AML recurrence. Long-term culture in vitro with low doses of sorafenib might induce resistance to this compound. The bone marrow microenvironment might reduce the proapoptotic efficacy of sorafenib in AML cells.
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W. Zhang, M. Konopleva, and M. Andreeff designed the experiments; W. Zhang, Y.-x. Shi, T. McQueen, and D. Harris performed the research; D. Small and X. Ling contributed new reagents and/or analytic tools; J. Cortes and A. Quintás-Cardama conducted the phase 1 clinical trial and analyzed the data; and W. Zhang, M. Konopleva, Z. Estrov, and M. Andreeff analyzed and interpreted the data.
We thank Wenjing Chen, Ellen Jackson, and Sheela V. Mathews for valued assistance in the collection of the patient clinical information and Betty L. Notzon and Vickie J. Williams for critical review of the manuscript.
The study sponsor had no role in the design of the study; the collection, analysis, interpretation of the data; the writing of the manuscript; or the decision to submit the manuscript for publication.
Manuscript received May 30, 2007; revised November 27, 2007; accepted December 26, 2007.
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