Genomic Profiling of Adult and Pediatric B-cell Acute Lymphoblastic Leukemia

Highlights

• The genomic landscapes of adult and pediatric B-ALL were defined by next-generation sequencing of patient samples.

• MEF2D and ZNF384 fusions could perturb B-cell differentiation or induce leukemia in mice and exhibited clinical relevance.

• Adult patients showed greater enrichment for alterations of genes linked to epigenetic modification and B-cell development.

This study comprehensively addressed the genomic signatures of adult versus pediatric B-ALL. The identification of distinct MEF2D and ZNF384 fusions expands the existing knowledge about molecular subtypes of B-ALL in both age groups. RNA-seq data allowed most of the B-ALL cases to be clustered into 8 subgroups related to genetic abnormalities. Notably, adult patients have more cooperative sequence variation mutations than pediatric patients, especially in genes involved in epigenetic regulation and B-cell development. These findings may improve our understanding of leukemogenesis in B-ALL, leading to a more precise genetic classification and the further development of targeted therapy in this disease.

Abstract

Genomic landscapes of 92 adult and 111 pediatric patients with B-cell acute lymphoblastic leukemia (B-ALL) were investigated using next-generation sequencing and copy number alteration analysis. Recurrent gene mutations and fusions were tested in an additional 87 adult and 93 pediatric patients. Among the 29 newly identified in-frame gene fusions, those involving MEF2D and ZNF384 were clinically relevant and were demonstrated to perturb B-cell differentiation, with EP300-ZNF384 inducing leukemia in mice. Eight gene expression subgroups associated with characteristic genetic abnormalities were identified, including leukemia with MEF2D and ZNF384 fusions in two distinct clusters. In subgroup G4 which was characterized by ERG deletion, DUX4-IGH fusion was detected in most cases. This comprehensive dataset allowed us to compare the features of molecular pathogenesis between adult and pediatric B-ALL and to identify signatures possibly related to the inferior outcome of adults to that of children. We found that, besides the known discrepancies in frequencies of prognostic markers, adult patients had more cooperative mutations and greater enrichment for alterations of epigenetic modifiers and genes linked to B-cell development, suggesting difference in the target cells of transformation between adult and pediatric patients and may explain in part the disparity in their responses to treatment.