Targeting BTK for the treatment of FLT3-ITD mutated acute myeloid leukemia.

Genevra Pillinger,David J Macewan,Stuart A Rushworth,Kristian M Bowles,Amina Abdul-Aziz,Matthew Lawes,Lyubov Zaitseva

doi:10.1038/srep12949

Abstract

Approximately 20% of patients with acute myeloid leukaemia (AML) have a mutation in FMS-like-tyrosine-kinase-3 (FLT3). FLT3 is a trans-membrane receptor with a tyrosine kinase domain which, when activated, initiates a cascade of phosphorylated proteins including the SRC family of kinases. Recently our group and others have shown that pharmacologic inhibition and genetic knockdown of Bruton’s tyrosine kinase (BTK) blocks AML blast proliferation, leukaemic cell adhesion to bone marrow stromal cells as well as migration of AML blasts. The anti-proliferative effects of BTK inhibition in human AML are mediated via inhibition of downstream NF-κB pro-survival signalling however the upstream drivers of BTK activation in human AML have yet to be fully characterised. Here we place the FLT3-ITD upstream of BTK in AML and show that the BTK inhibitor ibrutinib inhibits the survival and proliferation of FLT3-ITD primary AML blasts and AML cell lines. Furthermore ibrutinib inhibits the activation of downstream kinases including MAPK, AKT and STAT5. In addition we show that BTK RNAi inhibits proliferation of FLT3-ITD AML cells. Finally we report that ibrutinib reverses the cyto-protective role of BMSC on FLT3-ITD AML survival. These results argue for the evaluation of ibrutinib in patients with FLT3-ITD mutated AML.

Highlights

Acute myeloid leukaemia (AML) is primarily a disease of the elderly with a median age at diagnosis of 72 years
We report how ibrutinib synergises in combination with daunorubicin, and how ibrutinib functions in part by reducing the cyto-protection provided to FMS-like tyrosine kinase-3 receptor (FLT3)-internal tandem duplication (ITD) acute myeloid leukaemia (AML) cells by bone marrow stromal cells
We looked to characterise whether FLT3-ITD mutated primary AML and AML cell lines, which accounts for approximately 20% of all AML14, responds to Bruton’s tyrosine kinase (BTK) inhibition by ibrutinib treatment

Summary

Introduction

Acute myeloid leukaemia (AML) is primarily a disease of the elderly with a median age at diagnosis of 72 years. A number of receptor and non-receptor tyrosine kinases have been identified as functionally important in the biology of acute myeloid leukaemia (AML)[5,6,7]. Protein Kinase B (AKT), phosphatidylinositol 3-kinase isoform p110delta (P13-K), Signal Transducer and Activator of transcription 5 (STAT5), Mitogen-Activated Protein Kinase (MAPK) and Bruton’s tyrosine Kinase (BTK), have all been shown to be part of pathways that regulate AML survival[8,9,10,11]. Various receptor tyrosine kinase mutations have been identified in AML patients. The activating FLT3-ITD mutations in AML regulate downstream pro-leukaemic pathways[15] making FLT3 an attractive drugable target in this disease[16]. We provide a biologic rationale for the targeting of BTK in FLT3 mutated AML

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Results

Conclusion