High Frequency of GATA1 Mutations in Childhood Non-Down Syndrome Acute Megakaryoblastic Leukemia
Authors: Reinhardt Katarina , Zwaan C. Michel , Dworzak Michael , de Rooij Jasmijn D.E. , Kaspers Gertjan , Lehrnbecher Thomas , Hasle Henrik , Bernig Toralf , Cavuela Jean-Michel , Kolenova Alexandra , Harbott Jochen , Bourquin Jean-Pierre , Stary Jan , Creutzig Ursula , Reinhardt Dirk 
Published: October 2019

Abstract
Abstract 888

Introduction:
Pediatric acute megakaryoblastic leukemia (AMKL) occurred in 6.6% (84/1271) of the children enrolled to the AML-BFM98 and 2004 studies.
Despite a similar phenotype in morphology and immunophenotype, AMKL shows a heterogenous cytogenetic distribution (normal karyotype 23%, complex karyotype 21%, t(1;22) 9%; MLL-rearrangement 8%; monosomy 7 5%, trisomy 8 5%; other aberrations 29%).
Mutations of the hematopoietic transcription factor GATA1 have been identified in almost all children suffering myeloid leukemia of Down syndrome (ML-DS). In addition, GATA1 mutations (GATA1mut) could be identified in children with trisomy 21 mosaic.
Here, AMKL without evidence of Down syndrome or Down syndrome mosaic were analyzed for mutations in exon 1, 2 or 3 of the transcription factor GATA1.

Patients:
Seventy-one children from the AML-BFM Study group (n=51; 2000–2011), the Netherlands (n=10), France (n=3) and Scandinavia (n=7) were included.
Within the AML-BFM Group the 51 analyzed patients showed similar characteristics compared to the total cohort of 84 children with AMKL of the AML-BFM 98 and 2004 studies.
AMKL was confirmed according to the WHO classification by genetics (t(1;22)); morphology and immunophenotyping. Table 1a) summarizes the patientxs characteristics and b) the cytogenetic results.

Methods:
For GATA1 mutation screening genomic DNA was amplified by PCR reaction for exon 1, 2, and 3. PCR amplicons were analyzed by direct sequencing or following denaturing high-performance liquid chromatography (WAVE).

Results:
Seven different GATA1 mutations were detected in 8 children (11.1%; table 2).
In all GATA1mut leukemia, a trisomy 21 within the leukemic blasts could be detected.
Seven out of these 8 children and all other 64 AMKL patients have been treated with intensive chemotherapy regimens according the study group protocols. The results are given in table 2. All achieved continuous complete remission (CCR; 0.4 to 4.2 years).
In one newborn with typical morphology and immunophenotype a GATA1mut associated transient leukemia was supposed. The child achieved CCR (follow-up 6 years).
In total, allogeneic stem cell transplantation in 1st CR was performed in 6 children with AMKL (GATA1mut leukemia n=1).

Conclusions:
GATA1 mutations occurred in 11% of children with AMKL without any symptoms or evidence of trisomy 21 or trisomy 21 mosaic. GATA1 mutations are associated with a trisomy 21 within the leukemic blasts. Although non-response occurred, prognosis was significant better compared to other AMKL. Therefore, analysis of GATA1 mutation in infant AMKL is strongly recommended. Whether treatment reduction similar to ML-DS Down syndrome is feasible needs to be confirmed.

Disclosures:
No relevant conflicts of interest to declare.