Abstract
BackgroundGATA3 is pivotal for the development of T lymphocytes. While its effects in later stages of T cell differentiation are well recognized, the role of GATA3 in the generation of early T cell precursors (ETP) has only recently been explored. As aberrant GATA3 mRNA expression has been linked to cancerogenesis, we investigated the role of GATA3 in early T cell precursor acute lymphoblastic leukemia (ETP-ALL).MethodsWe analyzed GATA3 mRNA expression by RT-PCR (n = 182) in adult patients with T-ALL. Of these, we identified 70 of 182 patients with ETP-ALL by immunophenotyping. DNA methylation was assessed genome wide (Illumina Infinium® HumanMethylation450 BeadChip platform) in 12 patients and GATA3-specifically by pyrosequencing in 70 patients with ETP-ALL. The mutational landscape of ETP-ALL with respect to GATA3 expression was investigated in 18 patients and validated by Sanger sequencing in 65 patients with ETP-ALL. Gene expression profiles (Affymetrix Human genome U133 Plus 2.0) of an independent cohort of adult T-ALL (n = 83) were used to identify ETP-ALL and investigate GATA3low and GATA3high expressing T-ALL patients. In addition, the ETP-ALL cell line PER-117 was investigated for cytotoxicity, apoptosis, GATA3 mRNA expression, DNA methylation, and global gene expression before and after treatment with decitabine.ResultsIn our cohort of 70 ETP-ALL patients, 33 % (23/70) lacked GATA3 expression and were thus defined as GATA3low. DNA methylation analysis revealed a high degree of GATA3 CpG island methylation in GATA3low compared with GATA3high ETP-ALL patients (mean 46 vs. 21 %, p < 0.0001). Genome-wide expression profiling of GATA3low ETP-ALL exhibited enrichment of myeloid/lymphoid progenitor (MLP) and granulocyte/monocyte progenitor (GMP) genes, while T cell-specific signatures were downregulated compared to GATA3high ETP-ALL. Among others, FLT3 expression was upregulated and mutational analyses demonstrated a high rate (79 %) of FLT3 mutations. Hypomethylating agents induced reversal of GATA3 silencing, and gene expression profiling revealed downregulation of hematopoietic stem cell genes and upregulation of T cell differentiation.ConclusionsWe propose GATA3low ETP-ALL as a novel stem cell-like leukemia with implications for the use of myeloid-derived therapies.Electronic supplementary materialThe online version of this article (doi:10.1186/s13045-016-0324-8) contains supplementary material, which is available to authorized users.
Highlights
GATA3 is pivotal for the development of T lymphocytes
Lack of GATA3 expression in early T cell precursors (ETP)-ALL We first assessed GATA3 mRNA expression by microarray analysis and found that mean expression of GATA3 was higher in T-ALL (4.88 ± 0.41, mean ± s.e., n = 83) than in other cohorts (NC 1.33 ± 0.11, n = 24; acute myeloid leukemia (AML) 0.57 ± 0.05, n = 130; and B cell precursor acute lymphoblastic leukemia (BCP-ALL) 3.28 ± 0.66, n = 81; all values are mean ± s.e., p < 0.001) (Fig. 1a)
GATA3 silencing is mediated by aberrant DNA methylation To explore the regulation of GATA3 expression, we investigated global DNA methylation on the Illumina HumanMethylation 450 k platform in 12 early T cell precursor acute lymphoblastic leukemia (ETP-ALL) samples (Fig. 2), which were selected according to GATA3 mRNA expression (GATA3low vs. GATA3high) and mutational status of DNMT3A
Summary
While its effects in later stages of T cell differentiation are well recognized, the role of GATA3 in the generation of early T cell precursors (ETP) has only recently been explored. As aberrant GATA3 mRNA expression has been linked to cancerogenesis, we investigated the role of GATA3 in early T cell precursor acute lymphoblastic leukemia (ETP-ALL). GATA3 is a transcription factor with a pivotal role in multiple developmental steps of T lymphopoiesis [1, 2], including the development of early T cell precursors (ETPs), a rare subpopulation of cells sharing characteristics with multipotent hematopoietic progenitors in the bone marrow [3]. GATA3 was required for the development of ETPs, whereas totipotent hematopoietic stem cells (HSCs) remained unaffected by in vivo manipulation of GATA3 expression levels. GATA3 was reported to restrain Notch activity, repress NK-cell fate and upregulate T cell lineage genes to facilitate T cell differentiation [7]
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