FLT3 K663Q is a novel AML-associated oncogenic kinase: determination of biochemical properties and sensitivity to Sunitinib (SU11248)

Abstract

Somatic mutations of FLT3 resulting in constitutive kinase activation are the most common acquired genomic abnormality found in acute myeloid leukemia (AML). The majority of these mutations are internal tandem duplications (ITD) of the juxtamembrane region (JM). In addition, a minority of cases of AML are associated with mutation of the FLT3 activation loop (AL), typically involving codons D835 and/or I836. We hypothesized that other novel mutations of FLT3 could also contribute to leukemogenesis. We genotyped 109 cases of AML and identified two novel gain-of-function mutations. The first mutation, N841 H, is similar to previously described mutations involving amino-acid substitutions of codon 841. The other novel mutation, FLT3 K663Q, is the first AML-associated gain-of-function mutation located outside the JM and AL domains. Of note, this mutation was potently inhibited by Sunitinib (SU11248), a previously described FLT3 kinase inhibitor. Sunitinib reduced the proliferation and induced apoptosis of transformed Ba/F3 cells expressing FLT3 K663Q. The potency of Sunitinib against FLT3 K663Q was similar to its potency against FLT3 ITD mutations. We conclude that FLT3 mutations in AML can involve novel regions of the TK1. Future studies are needed to define the incidence and prognostic significance of FLT3 mutations outside the well-established JM and AL regions.

Exome sequencing identifies putative drivers of progression of transient myeloproliferative disorder to AMKL in infants with Down syndrome

“…In any case, this variant is of potential interest in the context of tumorigenesis, since in the literature a somatic mutation in the same codon of FLT3 (K663Q) was described in AML and was confirmed to result in a constitutively activated protein. 35 Altogether these data suggest that GATA1 mutation is the primary event in DS TMDs and is mostly seen in neonatal TMD samples in the absence of any other mutation. However, in some cases, progression of the disease is characterized by accumulation of additional driver mutations occurring in different subpopulations of megakaryoblasts, resulting in competition between clones.…”

Crenolanib is a potent inhibitor of FLT3 with activity against resistance-conferring point mutants

“…Crenolanib has no activity against the F691 point mutations, which also emerged during quizartinib, albeit at a lower frequency than the D835 mutations, and we did not test the drug exhaustively against all of the other relatively uncommon FLT3 point mutations that have been reported previously. 18,25,[27][28][29] It is likely that as this field progresses, a number of compounds will emerge that have overlapping activity against FLT3 variants, 30,31 similar to the case with inhibitors of BCR-ABL. However, FLT3/ITD and FLT3/D835 mutations, arising either spontaneously or in response to treatment with a FLT3TKI, constitute the vast bulk of clinically important FLT3-activating mutations, and we have demonstrated here that crenolanib not only has in vitro activity against them, but that oral dosing of the drug can achieve inhibitory concentrations against these mutations in AML patients.…”

An FLT3 gene-expression signature predicts clinical outcome in normal karyotype AML

“…Because FLT3-TKD mutations were not observed among these cases and there was no significant difference in FLT3 mRNA levels, other alterations in FLT3 or other genes would have to account for the FLT3 pathway activation signature. Other alterations in FLT3 might include JM domain point mutations [34][35][36] as well as a recently identified mutation in the N-terminal lobe of the TKD (K663Q), 37 which have similar signaling characteristics, at least in vitro. Alterations in other genes might include recently described CBL-inactivating mutations, resulting in up-regulated wild-type FLT3 receptor signaling in AML.…”