Mutant FLT3: a direct target of sorafenib in acute myelogenous leukemia.
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.


CONCLUSIONS
Sorafenib may have therapeutic efficacy in AML patients whose cells harbor FLT3-ITD mutations.
Zhang
Weiguo
W
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, Houston, TX 77030, USA.
Konopleva
Marina
M
Shi
Yue-xi
YX
McQueen
Teresa
T
Harris
David
D
Ling
Xiaoyang
X
Estrov
Zeev
Z
Quintás-Cardama
Alfonso
A
Small
Donald
D
Cortes
Jorge
J
Andreeff
Michael
M
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001557:Benzenesulfonates / Q000494:pharmacology* / Q000627:therapeutic use; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005455:Fluorescent Antibody Technique; D006801:Humans; D015151:Immunoblotting; D053208:Kaplan-Meier Estimate; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy* / Q000235:genetics; D051379:Mice; D016513:Mice, SCID; D009154:Mutation; D009360:Neoplastic Cells, Circulating / Q000187:drug effects*; D009536:Niacinamide / Q000031:analogs & derivatives; D010671:Phenylurea Compounds; D016133:Polymerase Chain Reaction; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D011725:Pyridines / Q000494:pharmacology* / Q000627:therapeutic use; D000077157:Sorafenib; D014183:Transplantation, Heterologous; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics*
D000970:Antineoplastic Agents; D001557:Benzenesulfonates; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D009536:Niacinamide; D000077157:Sorafenib; C497970:FLT3 protein, human; C497971:Flt3 protein, mouse; D051941:fms-Like Tyrosine Kinase 3