Acute myeloid leukemia (AML) remains the most common form of acute leukemia among adults and accounts for a large number of deaths. Mutation in FMS-like tyrosine kinase 3 (FLT3) is one of the most prevalent factor in this heterogeneous disease. The major mutations in FLT3 can be categories as internal tandem duplications (ITD) and point mutations. Recent studies suggest that ITDs are subdivided in to two groups depending on their location: the juxtamembrane domain (ITD-JM) and the tyrosine kinase domain (ITD-TDK). Although, ITD-JM has been characterized well the ITD-TKD has not yet been studied well due to its recent discovery. For this reason, we compared ITD mutations in TKD and JM, as well as the most frequently occurring point mutation located in the TKD, D835Y. The purpose of this study was to understand whether it is the mutation’s nature or location that plays the driving role in leukemogenesis. We used a cytokine-dependent mouse pro-B cell line, BaF3, to overexpress different FLT3 mutants. We first examined the colony formation capacity in semisolid cytokine- and serum-free medium. The assay resulted in indistinguishable number and size of colonies for both ITD-JM and ITD-TKD, while D835Y-TKD transfected cells failed to form colonies suggesting that the ITD-TKD mutations have stronger transforming potential than other TKD mutations. In addition to colony formation assays, cell proliferation and survival was significantly higher in ITD-TKD expressing cells compared to cells expressing D835Y-TKD. Finally, we showed that phosphorylation of STAT5 and AKT is increased in ITD-TKD, while other FLT3 downstream signaling remained unaffected. All together, our data suggest that ITD-TKD displays higher oncogenic potential than other TKD mutants.

Citation Format: Alissa Marhäll, Thomas Fischer, Florian Heidel, Julhash U. Kazi, Lars Rönnstrand. Insertion mutations in the tyrosine kinase domain of FLT3 display a higher oncogenic potential than the D835Y mutation in acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2380. doi:10.1158/1538-7445.AM2017-2380