Overexpression of GATA1 Confers Resistance to Chemotherapy in Acute Megakaryocytic Leukemia

John Timothy Caldwell,Yubin Ge,Steven A Buck,Jeffrey W Taub,Alan A Dombkowski,Holly Edwards,Larry H Matherly,Yves St-Pierre

doi:10.1371/journal.pone.0068601

Abstract

It has been previously shown that acute myeloid leukemia (AML) patients with higher levels of GATA1 expression have poorer outcomes. Furthermore, pediatric Down syndrome (DS) patients with acute megakaryocytic leukemia (AMKL), whose blast cells almost universally harbor somatic mutations in exon 2 of the transcription factor gene GATA1, demonstrate increased overall survival relative to non-DS pediatric patients, suggesting a potential role for GATA1 in chemotherapy response. In this study, we confirmed that amongst non-DS patients, GATA1 transcripts were significantly higher in AMKL blasts compared to blasts from other AML subgroups. Further, GATA1 transcript levels significantly correlated with transcript levels for the anti-apoptotic protein Bcl-xL in our patient cohort. ShRNA knockdown of GATA1 in the megakaryocytic cell line Meg-01 resulted in significantly increased cytarabine (ara-C) and daunorubicin anti-proliferative sensitivities and decreased Bcl-xL transcript and protein levels. Chromatin immunoprecipitation (ChIP) and reporter gene assays demonstrated that the Bcl-x gene (which transcribes the Bcl-xL transcripts) is a bona fide GATA1 target gene in AMKL cells. Treatment of the Meg-01 cells with the histone deacetylase inhibitor valproic acid resulted in down-regulation of both GATA1 and Bcl-xL and significantly enhanced ara-C sensitivity. Furthermore, additional GATA1 target genes were identified by oligonucleotide microarray and ChIP-on-Chip analyses. Our findings demonstrate a role for GATA1 in chemotherapy resistance in non-DS AMKL cells, and identified additional GATA1 target genes for future studies.

Highlights

In the pediatric population, acute myeloid leukemia (AML) has a relatively guarded prognosis with five-year survival rates of approximately 50%, despite intensive therapy
We found that the histone deacetylase (HDAC) inhibitor, valproic acid (VPA), can decrease GATA1 expression and synergize with ara-C in exerting antileukemic activities toward megakaryocytic leukemia cells
Overexpression of GATA1 in Acute megakaryocytic leukemia (AMKL) blasts is associated with chemotherapy resistance

Summary

Introduction

Acute myeloid leukemia (AML) has a relatively guarded prognosis with five-year survival rates of approximately 50% (www.seer.cancer.gov), despite intensive therapy. The blast cells of DS AMKL patients almost universally harbor a somatic mutation in exon 2 of the transcription factor GATA1 gene (localized to Xp11.23), resulting in the introduction of premature stop codons and the synthesis of a shorter GATA1 protein (designated GATA1s, 40-kDa) initiated from a downstream initiation site and distinguishable from the wildtype GATA1 (50-kDa) [9]. Both GATA1s and the wild-type GATA1 proteins show similar DNA binding abilities and interact with a partner protein named “friend of GATA1” (FOG1), though the GATA1s protein exhibits altered transactivation capacity due to the loss of the N-terminal activation domain [9]

Methods

Results

Conclusion