Prognostic Analysis of GATA2 Mutations in CEBPA-Mutated Acute Myeloid Leukemia

Background

CEBPA mutations are found in approximately 10% of acute myeloid leukemia (AML). Recent studies revealed an association between CEBPA and GATA2 mutations. GATA2 gene encodes a transcription factor involved in hematopoiesis. In two recent studies (Grossmann et al., BJH 2013; Fasan et al., Leukemia 2013), GATA2 mutations appeared to be associated specifically with double CEBPA mutations and improved overall survival (OS). In contrast, another study failed to show any impact on OS (Green et al., BJH 2013). The aim of our study was to investigate the prognostic significance of GATA2 mutations in a large cohort of patients with CEBPA-mutated AML.

Patients and methods

We studied a cohort of 128 patients with CEBPA-mutated AML treated with intensive chemotherapy. The entire coding region of CEBPA, NPM1 exon 12, and GATA2 exons 4 to 6 (that encode the two multifunctional zinc finger domains of the protein) were screened on genomic DNA by PCR and direct Sanger sequencing. FLT3 internal tandem duplications (FLT3-ITD) were screened on genomic DNA by PCR and fragment analysis. Additionally, transcriptome analysis was performed with Affymetrix HG U133 Plus 2.0 array in pre-treatment samples from 72 patients for which RNA was available.

Results

Median age at AML diagnosis in the whole cohort was 50 years (range, 3-80). Almost all patients belonged to the intermediate cytogenetic risk-group (n=117), of which 90 had a normal karyotype. The remaining patients had favorable (n=1) or adverse cytogenetics (n=4). CEBPA mutations were distributed as follows: 29 single-mutated (sm) cases with N-terminal (N-ter) mutations, 12 sm cases with C-terminal (C-ter) mutations, 80 double-mutated (dm) cases with both N-ter and C-ter mutations, 2 cases with homozygous N-ter and 5 cases with homozygous C-ter mutations. GATA2 mutations were found in 29/128 patients (23%) and were significantly associated with CEBPA dm cases (4/41 sm vs 25/87 dm: Fisher's exact test p=0.022). NPM1 mutations were detected in 12 patients. They were specifically associated with CEBPA sm cases (12/40 sm vs 0/78 dm, p<0.001) and mutually exclusive with GATA2 mutations (12/93 GATA2 wild-type vs 0/25 GATA2 mutated cases, p<0.001). In contrast with previous studies, FLT3-ITD and GATA2 mutations did co-occur in our cohort, with 3 GATA2 mutants identified in 10 FLT3-ITD positive patients. Transcriptome analysis revealed that GATA2 mutations were not associated with a specific gene expression signature. As previously described, we found that CEBPA dm AML harbored a specific gene expression profile distinct from CEBPA sm cases. Since AML with homozygous CEBPA mutations were found to have a similar gene expression signature as CEBPA dm AML, we decided to pool them together for prognostic analysis. Overall, complete remission was achieved in 113 patients (88%), of whom 36 relapsed (estimated cumulated incidence of relapse [CIR] at 3 and 5 years, 39%). Neither age nor karyotype or gene mutations (including NPM1, FLT3, GATA2 and type of CEBPA mutation) significantly influenced CIR in multivariate analysis. Five-year OS was estimated at 58% in the whole cohort, with longer OS in cases with normal karyotype (p=0.05) and double CEBPAmutations (sm vs dm, p=0.03). In multivariate analysis, younger age (p=0.020) and normal karyotype (p=0.029) remained the only factors significantly associated with a longer OS.

Conclusions

This study confirmed the strong association between GATA2 mutations and CEBPA double mutations, in line with previous studies. However, we did not find any prognostic impact of GATA2 mutations in our cohort of CEBPA-mutated AML.