Clinical resistance to the kinase inhibitor PKC412 in acute myeloid leukemia by mutation of Asn-676 in the FLT3 tyrosine kinase domain.
Activating mutations in the FLT3 tyrosine kinase (TK) occur in approximately 35% of patients with acute myeloid leukemia (AML). Therefore, targeting mutated FLT3 is an attractive therapeutic strategy, and early clinical trials testing FLT3 TK inhibitors (TKI) showed measurable clinical responses. Most of these responses were transient; however, in a subset of patients blast recurrence was preceded by an interval of prolonged remission. The etiology of clinical resistance to FLT3-TKI in AML is unclear but is of major significance for the development of future therapeutic strategies. We searched for mechanisms of resistance in 6 patients with AML who had relapses upon PKC412 treatment. In an index AML patient, an algorithm of analyses was applied using clinical material. In vivo and in vitro investigation of primary blasts at relapse revealed persistent TK phosphorylation of FLT3 despite sufficient PKC412 serum levels. Through additional molecular analyses, we identified a single amino acid substitution at position 676 (N676K) within the FLT3 kinase domain as the sole cause of resistance to PKC412 in this patient. Reconstitution experiments expressing the N676K mutant in 32D cells demonstrated that FLT3-ITD-N676K was sufficient to confer an intermediate level of resistance to PKC412 in vitro. These studies point out that a genetically complex malignancy such as AML may retain dependence on a single oncogenic signal.
Heidel
Florian
F
3rd Medical Department, Johannes Gutenberg University Mainz Langenbeckstrasse 1, 55101 Mainz, Germany.
Solem
Fian K
FK
Breitenbuecher
Frank
F
Lipka
Daniel B
DB
Kasper
Stefan
S
Thiede
M H
MH
Brandts
Christian
C
Serve
Hubert
H
Roesel
Johannes
J
Giles
Francis
F
Feldman
Eric
E
Ehninger
Gerhard
G
Schiller
Gary J
GJ
Nimer
Stephen
S
Stone
Richard M
RM
Wang
Yanfeng
Y
Kindler
Thomas
T
Cohen
Pamela S
PS
Huber
Christoph
C
Fischer
Thomas
T
D000208:Acute Disease; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004789:Enzyme Activation / Q000235:genetics; D006801:Humans; D007951:Leukemia, Myeloid / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics*; D020125:Mutation, Missense; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011505:Protein-Tyrosine Kinases / Q000235:genetics; D012008:Recurrence; D019311:Staurosporine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D051941:fms-Like Tyrosine Kinase 3 / Q000235:genetics*
D047428:Protein Kinase Inhibitors; C497970:FLT3 protein, human; D011505:Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; D011493:Protein Kinase C; D019311:Staurosporine; C059539:midostaurin