ZNF521 Enhances MLL-AF9-Dependent Hematopoietic Stem Cell Transformation in Acute Myeloid Leukemias by Altering the Gene Expression Landscape.

Emanuela Chiarella,Antonino Neri,Nicola Amodio,Daniela Lico,Emanuela G Cosentino,Katia Todoerti,Maria Mesuraca,Stefania Scicchitano,Heather Mandy Bond,Annamaria Aloisio

doi:10.3390/ijms221910814

Abstract

Leukemias derived from the MLL-AF9 rearrangement rely on dysfunctional transcriptional networks. ZNF521, a transcription co-factor implicated in the control of hematopoiesis, has been proposed to sustain leukemic transformation in collaboration with other oncogenes. Here, we demonstrate that ZNF521 mRNA levels correlate with specific genetic aberrations: in particular, the highest expression is observed in AMLs bearing MLL rearrangements, while the lowest is detected in AMLs with FLT3-ITD, NPM1, or CEBPα double mutations. In cord blood-derived CD34+ cells, enforced expression of ZNF521 provides a significant proliferative advantage and enhances MLL-AF9 effects on the induction of proliferation and the expansion of leukemic progenitor cells. Transcriptome analysis of primary CD34+ cultures displayed subsets of genes up-regulated by MLL-AF9 or ZNF521 single transgene overexpression as well as in MLL-AF9/ZNF521 combinations, at either the early or late time points of an in vitro leukemogenesis model. The silencing of ZNF521 in the MLL-AF9 + THP-1 cell line coherently results in an impairment of growth and clonogenicity, recapitulating the effects observed in primary cells. Taken together, these results underscore a role for ZNF521 in sustaining the self-renewal of the immature AML compartment, most likely through the perturbation of the gene expression landscape, which ultimately favors the expansion of MLL-AF9-transformed leukemic clones.

Highlights

Acute myeloid leukemias (AMLs) are characterized by chromosomal translocations involving the Mixed Lineage Leukemia (MLL) gene, which results in a variety of fusion oncogenes [1] derived from genes that are normally required during hematopoietic development; once fused, they induce epigenetic and transcription factor dysregulation [2]
Relatively low ZNF521 expression levels appeared to correlate with the t(8;21) translocation associated with the AML1-ETO fusion gene or the t(15;17) translocation generating the PML-RARα genes (Figure 1A,B)
When considering the FAB subgroups, the highest levels of ZNF521 mRNA expression were observed in M0, while the lowest amounts were expressed in M3 AMLs (p = 6.02 × 10−3 ), indicating that elevated ZNF521 expression correlates with minimally differentiated acute myeloblastic leukemia (M0-AML), a rare type of AML that is associated with poor prognosis (GSE6891) (Figure 1C)

Summary

Introduction

Acute myeloid leukemias (AMLs) are characterized by chromosomal translocations involving the Mixed Lineage Leukemia (MLL) gene, which results in a variety of fusion oncogenes [1] derived from genes that are normally required during hematopoietic development; once fused, they induce epigenetic and transcription factor dysregulation [2]. One of the most frequent MLL translocations leading to AML results from the chromosomal translocation of t(9;11) (p21–22;q23), which fuses the MLL gene with the AF9 gene ( known as MLLT3 or LTG9) and is considered an initiating factor for leukemogenesis [3,4,5]. MLL-AF9 target genes include transcription factors from the Hox family (HoxA9, HoxA10, HoxA5, ZNF532, HoxA7, Meis and PBX3) [15,16,17,18]. This set of target genes was confirmed in leukemias induced in mice transformed by MLL-AF9 (HoxA9, HoxA10, Evi (MECOM), HoxA2, HoxA7

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Discussion

Conclusion