The combination of FLT3 and SYK kinase inhibitors is toxic to leukaemia cells with CBL mutations

J Cell Mol Med. 2020 Feb;24(3):2145-2156. doi: 10.1111/jcmm.14820. Epub 2020 Jan 14.


Mutations in the E3 ubiquitin ligase CBL, found in several myeloid neoplasms, lead to decreased ubiquitin ligase activity. In murine systems, these mutations are associated with cytokine-independent proliferation, thought to result from the activation of hematopoietic growth receptors, including FLT3 and KIT. Using cell lines and primary patient cells, we compared the activity of a panel of FLT3 inhibitors currently being used or tested in AML patients and also evaluated the effects of inhibition of the non-receptor tyrosine kinase, SYK. We show that FLT3 inhibitors ranging from promiscuous to highly targeted are potent inhibitors of growth of leukaemia cells expressing mutant CBL in vitro, and we demonstrate in vivo efficacy of midostaurin using mouse models of mutant CBL. Potentiation of effects of targeted FLT3 inhibition by SYK inhibition has been demonstrated in models of mutant FLT3-positive AML and AML characterized by hyperactivated SYK. Here, we show that targeted SYK inhibition similarly enhances the effects of midostaurin and other FLT3 inhibitors against mutant CBL-positive leukaemia. Taken together, our results support the notion that mutant CBL-expressing myeloid leukaemias are highly sensitive to available FLT3 inhibitors and that this effect can be significantly augmented by optimum inhibition of SYK kinase.

Keywords: AML; FLT3; leukaemia; mutant CBL; tyrosine kinase.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Humans
  • Leukemia, Myeloid / drug therapy
  • Leukemia, Myeloid / genetics*
  • Mice
  • Mutation / drug effects
  • Mutation / genetics*
  • Proto-Oncogene Proteins c-cbl / genetics*
  • Signal Transduction / drug effects
  • Signal Transduction / genetics
  • Staurosporine / analogs & derivatives
  • Staurosporine / pharmacology
  • Syk Kinase / genetics*
  • fms-Like Tyrosine Kinase 3 / genetics*


  • Proto-Oncogene Proteins c-cbl
  • FLT3 protein, human
  • fms-Like Tyrosine Kinase 3
  • SYK protein, human
  • Syk Kinase
  • Staurosporine
  • midostaurin