T-LAK cell-originated protein kinase presents a novel therapeutic target in FLT3-ITD mutated acute myeloid leukemia.

Houda Alachkar,Naofumi Takamatsu,Gordana Raca,Gregory Malnassy,Alex Woods,Noreen Fulton,Martin Mutonga,Olatoyosi Odenike,Takashi Miyamoto,Liping Meng,Jae-Hyun Park,Yo Matsuo,Yusuke Nakamura,Wendy Stock,Justin Kline

doi:10.18632/oncotarget.5418

Abstract

Gain-of-function mutations of FLT3 (FLT3-ITD), comprises up to 30% of normal karyotype acute myeloid leukemia (AML) and is associated with an adverse prognosis. Current FLT3 kinase inhibitors have been tested extensively, but have not yet resulted in a survival benefit and novel therapies are awaited. Here we show that T-LAK cell-originated protein kinase (TOPK), a mitotic kinase highly expressed in and correlated with more aggressive phenotype in several types of cancer, is expressed in AML but not in normal CD34+ cells and that TOPK knockdown decreased cell viability and induced apoptosis. Treatment of AML cells with TOPK inhibitor (OTS514) resulted in a dose-dependent decrease in cell viability with lower IC50 in FLT3-mutated cells, including blasts obtained from patients relapsed after FLT3-inhibitor treatment. Using a MV4-11-engrafted mouse model, we found that mice treated with 7.5 mg/kg IV daily for 3 weeks survived significantly longer than vehicle treated mice (median survival 46 vs 29 days, P < 0.001). Importantly, we identified TOPK as a FLT3-ITD and CEBPA regulated kinase, and that modulating TOPK expression or activity resulted in significant decrease of FLT3 expression and CEBPA phosphorylation. Thus, targeting TOPK in FLT3-ITD AML represents a novel therapeutic approach for this adverse risk subset of AML.

Highlights

Gain-of-function mutations of the tyrosine kinase (TK) receptor encoding FMS-like tyrosine kinase-3 (FLT3) have been observed in approximately 30% of cytogenetically normal acute myeloid leukemia (AML)
Annexin/ propidium iodide (PI) staining assessed by flow cytometry showed that T-LAK celloriginated protein kinase (TOPK) knock-down resulted in a dramatic increase in apoptosis in MV4-11 cells; less effect on apoptosis was observed in U937 cells (Figure 1C)
Having shown that TOPK knock-down resulted in enhancement of apoptosis and decrease in cell viability, we examined whether targeting TOPK kinase activity with a recently developed TOPK inhibitor OTS514 [41] would result in a cytotoxic effect in AML cells

Summary

Introduction

Gain-of-function mutations of the tyrosine kinase (TK) receptor encoding FMS-like tyrosine kinase-3 (FLT3) have been observed in approximately 30% of cytogenetically normal acute myeloid leukemia (AML). The FLT3-ITD and overexpression of FLT3 constitutively activate several pathways like MAPK/ERK, PI3K/AKT, NF-κB and STAT5 [7,8,9,10], and repress important transcription factors involved in myeloid differentiation, PU. and CEBPA [7, 11, 12]. The clinical impact of these compounds has not yet fulfilled the promise, possibly due to their insufficient inhibition of FLT3, lack of specificity, and the rapid emergence of resistance mechanisms in addition to pharmacokinetic limitations [16,17,18,19]. A recent study indicates that an ERK signaling pathway is likely to play a role in the mechanism of resistance to FLT3 inhibition conferred by stroma and FL ligand [20]. Some www.impactjournals.com/oncotarget alternative approaches for targeting FLT3-mutated AML have been focused on targeting downstream pathways (ERK1/2, CDK1, STAT5) that are activated by FLT3-ITD [11, 12, 21, 22]

Methods

Results

Conclusion