MiR-17 deregulates a core RUNX1-miRNA mechanism of CBF acute myeloid leukemia.

John Adams Fischer,Stefano Rossetti,Nicoletta Sacchi,Alessandro Beghini,Arani Datta,Kevin Hasegawa Eng

doi:10.1186/s12943-014-0283-z

John Adams Fischer, Stefano Rossetti + Show 4 more

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https://doi.org/10.1186/s12943-014-0283-z

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Abstract

BackgroundCore Binding Factor acute myeloid leukemia (CBF-AML) with t(8;21) RUNX1-MTG8 or inv(16) CBFB-MYH11 fusion proteins often show upregulation of wild type or mutated KIT receptor. However, also non-CBF-AML frequently displays upregulated KIT expression. In the first part of this study we show that KIT expression can be also upregulated by miR-17, a regulator of RUNX1, the gene encoding a CBF subunit. Interestingly, both CBF leukemia fusion proteins and miR-17, which targets RUNX1-3′UTR, negatively affect a common core RUNX1-miRNA mechanism that forces myeloid cells into an undifferentiated, KIT-induced, proliferating state. In the second part of this study we took advantage of the conservation of the core RUNX1-miRNA mechanism in mouse and human, to mechanistically demonstrate in a mouse myeloid cell model that increased KIT-induced proliferation is per se a mechanism sufficient to delay myeloid differentiation.MethodsHuman (U937) or mouse (32D) myeloid clonal lines were used, respectively, to test: 1) the effect of RUNX1-MTG8 and CBFB-MYH11 fusion proteins, or upregulation of miR-17, on KIT-induced proliferation and myeloid differentiation, and 2) the effect of upregulation of KIT-induced proliferation per se on myeloid cell differentiation.ResultsIn the first part of this study we found that stable miR-17 upregulation affects, like the CBF-AML fusion proteins (RUNX1-MTG8 or CBFB-MYH11), a core RUNX1-miRNA mechanism leading to KIT-induced proliferation of differentiation-arrested U937 myeloid cells. In the second part of the study we harnessed the conservation of this core mechanism in human and mouse to demonstrate that the extent of KIT upregulation in 32D mouse myeloid cells with wild type RUNX1 can per se delay G-CSF-induced differentiation. The integrated information gathered from the two myeloid cell models shows that RUNX1 regulates myeloid differentiation not only by direct transcriptional regulation of coding and non-coding myeloid differentiation functions (e.g. miR-223), but also by modulating KIT-induced proliferation via non-coding miRNAs (e.g. miR-221).ConclusionsThe novelty of this study is dual. On the one hand, miRNAs (e.g. miR-17) can mimic the effects of CBF-AML fusion proteins by affecting a core RUNX1-miRNA mechanism of KIT-induced proliferation of undifferentiated myeloid cells. On the other hand, the extent of KIT-induced proliferation itself can modulate myeloid differentiation of cells with wild type RUNX1 function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-014-0283-z) contains supplementary material, which is available to authorized users.

Highlights

Core Binding Factor acute myeloid leukemia (CBF-AML) with t(8;21) RUNX1-MTG8 or inv(16) CBFB-MYH11 fusion proteins often show upregulation of wild type or mutated KIT receptor
The CBFBMYH11 fusion protein derived from the inv(16) rearrangement would interfere with the wild type RUNX1 function both by depleting the nucleus of RUNX1 through sequestration into the cytoplasm and by exerting a dominant negative action over wild type RUNX1 (Figure 1A, right, based on [8,9])
Transient transfection of human U937 myeloid cells with a luciferase reporter driven by the miR-221 promoter shows that RUNX1, alone or in combination with CBFB, induces miR-221 transcription, while both RUNX1-MTG8 and CBFB-MYH11 repress miR-221 promoter (Figure 1B)

Summary

Introduction

Core Binding Factor acute myeloid leukemia (CBF-AML) with t(8;21) RUNX1-MTG8 or inv(16) CBFB-MYH11 fusion proteins often show upregulation of wild type or mutated KIT receptor. In the first part of this study we show that KIT expression can be upregulated by miR-17, a regulator of RUNX1, the gene encoding a CBF subunit Both CBF leukemia fusion proteins and miR-17, which targets RUNX1-3′UTR, negatively affect a common core RUNX1-miRNA mechanism that forces myeloid cells into an undifferentiated, KIT-induced, proliferating state. We found that the miR-222/221 gene cluster, involved in the regulation of the KIT receptor by targeting KIT-3'UTR [16], is a direct RUNX1-target, whose transcription is repressed by the dominant negative t(8;21) RUNX1-MTG8 fusion protein [17]

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