• The CBFA2T3-GLIS2 fusion transcript is common in pediatric cytogenetically normal AML and not restricted to FAB M7 subtype.• The CBFA2T3-GLIS2 fusion transcript is associated with poor prognosis in pediatric patients with AML.Pediatric cytogenetically normal acute myeloid leukemia (CN-AML) is a heterogeneous subgroup of myeloid clonal disorders that do not harbor known mutations. To investigate the mutation spectrum of pediatric CN-AML, we performed whole-transcriptome massively parallel sequencing on blasts from 7 CN-AML pediatric patients. In 3 patients we identified a recurrent cryptic inversion of chromosome 16, encoding a CBFA2T3-GLIS2 fusion transcript. In a validation cohort of 230 pediatric CN-AML samples we identified 17 new cases. Among a total of 20 patients with CBFA2T3-GLIS2 fusion transcript out of 237 investigated (8.4%), 10 patients (50%) did not belong to the French-American-British (FAB) M7 subgroup. The 5-year event-free survival for these 20 children was worse than that for the other CN-AML patients (27.4% vs 59.6%; P 5 .01). These data suggest that the presence of CBFA2T3-GLIS2 fusion transcript is a novel common feature of pediatric CN-AML, not restricted to the FAB M7 subtype, predicting poorer outcome. (Blood. 2013;121(17):3469-3472) IntroductionPediatric acute myeloid leukemia (AML) is a molecularly heterogeneous disease that arises from genetic alterations of pathways that regulate self-renewal and myeloid differentiation. While the majority of patients carry recurrent chromosomal translocations, almost 20% of childhood AMLs do not show any recognizable cytogenetic alteration and are defined as cytogenetically normal AML (CN-AML). 1Many genetic abnormalities have been identified in AML with normal karyotype, with the most frequent affecting genes such as NPM1, FLT3, CEBPA, and WT1. 1-5Genome-wide analyses have been used with the aim of determining the full array of genetic lesions of CN-AML. Recent studies have provided new insight into the molecular genetics and biology of AML, confirming both the complexity and the heterogeneity of this disease.6 Novel lesions such as mutations in IDH1 and DNMT3A have been identified. 7,8 However, these alterations are rare in pediatric AML, with IDH1/IDH2 accounting for 2% to 4% of cases 9,10 and DNMT3A not even being found mutated in childhood AML.11 Recently, 2 studies identified a novel recurrent translocation involving CBFA2T3 and GLIS2 in about 30% of children with non-Down syndrome acute megakaryoblastic leukemia (non-DS AMKL, AML French-American-British [FAB] M7).12,13 Nevertheless, there are many children with CN-AML in whom no genetic abnormality has been detected. The identification of the different genetic profiles characterizing this subgroup is a primary objective to be pursued. To this end, we performed whole-transcriptome massively parallel sequencing of 7 cases of pediatric CN-AML with the aim of identifying recurrent somatic mutations or genomic rearrangements. Subsequently, we validated our findings in a larger cohort of 230 pedi...

Approximately 10%-15% of gastrointestinal stromal tumors (GISTs) in adults do not harbor any mutation in the KIT or PDGFRA genes (ie, KIT/PDGFRA wild-type GISTs). Recently, mutations in SDHB and SDHC (which encode succinate dehydrogenase subunits B and C, respectively) but not in SDHA and SDHD (which encode subunits A and D, respectively) were identified in KIT/PDGFRA wild-type GISTs. To search for novel pathogenic mutations, we sequenced the tumor transcriptome of two young adult patients who developed sporadic KIT/PDGFRA wild-type GISTs by using a massively parallel sequencing approach. The only variants identified as disease related by computational analysis were in SDHA. One patient carried the homozygous nonsense mutation p.Ser384X, the other patient was a compound heterozygote harboring a p.Arg31X nonsense mutation and a p.Arg589Trp missense mutation. The heterozygous nonsense mutations in both patients were present in germline DNA isolated from peripheral blood. Protein structure analysis indicates that all three mutations lead to functional inactivation of the protein. This is the first report, to our knowle dge, that identifies SDHA inactivation as a common oncogenic event in GISTs that lack a mutation in KIT and PDGFRA.