Recurrent DNMT3B gene rearrangements are associated with unfavorable outcome in dicentric (9;20)-positive pediatric BCP-ALL

The dicentric chromosome dic(9;20)(p11∼13;q11), occurs in 2% of pediatric acute lymphoblastic leukemia (ALL) cases. However, the prognostic significance of the dic(9;20) alterations and the mechanism in which these alterations drive leukemogenesis remains elusive. Our study describes the demographic, clinical, prognostic, and molecular characteristics of the dic(9;20)-positive ALL in a cohort of 57 pediatric BCP-ALL patients. Targeted RNA-seq and Array CGH analysis unraveled heterogeneous breakpoints on chromosomes 9 and 20 and frequent deletions of the IKZF1 gene. Together with the intrinsic susceptibility for deletions in CDKN2A, CDKN2B, and PAX5 genes in the dic(9;20)-positive ALL, these patients are eligible for treatment escalation in the AIEOP-BFM ALL 2017 clinical study. Survival analysis revealed poor 5-year event-free survival (pEFS) of 69% in dic(9;20)-positive ALL cases, compared to BCP-ALL patients enrolled in modern treatment studies. Strikingly, we identified six dic(9;20)-positive cases with rearrangements involving the DNMT3B gene, and poor 5-year pEFS of 25% (SE = 20%), compared to 79% (SE = 9%) for the remaining cohort (P = 0.011). Despite the loss of the methyltransferase domain of the DNMT3B gene in most cases with DNMT3B rearrangements, we did not observe major changes in the global methylation patterns. Differential gene expression analysis of DNMT3B-rearranged ALL unraveled a dysregulation of genes involved in hematopoiesis, lymphocyte maturation, and the PI3K/AKT signaling pathway. After confirmation in an independent cohort, DNMT3B-rearranged ALL cases should be considered high-risk for relapse and treated accordingly. We provide clinical data sets of Array CGH, targeted RNA-seq, total RNA-seq, whole genome bisulfite (WGBS) and whole genome DNA sequencing (WGS) obtained from bone marrow (BM) or peripheral blood (PB) mononuclear cells of 57 pediatric patients with dicentric chromosome dic(9;20) positive Acute lymphocytic leukemia (ALL), from which in 6 cases DNMT3B gene rearrangement was identified. This data is complemented by total RNA-seq and WGBS of samples from 4 additional ALL patients with a t(12;21) translocation and ETV6-RUNX1 gene fusion. DNA was isolated from BM or PB lymphocytes using Qiagen QIAamp DNA Blood Midi Kit to perform i) Array CGH of 58 dic(9;20) positive samples by hybridizing 500ng DNA using a Agilent 400K SurePrint G3 Custom CGH Human Genome Microarray (e-Array design 84704) ii) WGBS of 6 DNMT3B rearrangement positive samples and 4 ETV6-RUNX1 positive samples using Tecan TrueMethyl oxBS-Seq module for library preparation and Illumina NovaSeq 6000 platform to run 2x151 cycles iii) WGS of DNMT3B rearrangement positive samples using Illumina Lotus DNA Library Prep Kit followed by sequencing running 2x160 cycles on an Illumina NovaSeq 6000 platform. RNA was isolated from PB lymphocytes using the PerkinElmer Chemagic 360 instrument, followed by i) targeted RNA-seq of 56 dic(9;20) positive samples prepared using Illumina TruSight RNA Pan-Cancer Panel and sequenced on an Illumina MiSeq platform running 2x75 cycles ii) total RNA-seq of 6 DNMT3B rearrangement positive samples and 4 ETV6-RUNX1 positive samples utilizing TruSeq Stranded Total RNA Library Prep Gold kit and running 2x100 cycles on an Illumina NovaSeq 6000 platform.

• Type: Other
• Archiver: European Genome-Phenome Archive (EGA)