Whole genome sequencing reveals the mutational landscape from disease diagnosis to relapse in patients with childhood acute myeloid leukaemia

INTRODUCTION: Leukaemia is the most common cancer in children, however, there is still a big gap in knowledge about the genomic alterations in childhood acute myeloid leukaemia (AML) compared to adult AML. Relapsed AML remains as a leading cause of cancer deaths among children. This study aims to understand the molecular mechanisms of relapsed AML by elucidating the mutational landscape before and during relapse.

MATERIALS AND METHODS: Whole genome sequencing was performed on matched samples collected at diagnosis, remission and relapse from three patients of de novo childhood AML. Sanger sequencing was performed for validation in 47 patients' samples, followed by functional analysis.

RESULTS: Overall, we identified 312 somatic mutations including synonymous single nucleotide variants (SNVs), missense SNVs, deletions and insertion frameshifts, stopgains and splice sites. After prioritisation, only 46 variants were present at diagnosis (13-17 mutations per patient) and 49 variants at relapse (12-20 mutations per patient). Out of 81 variants, there were 35 new variants detected at relapse but not present at diagnosis. Six potential driver mutations (KIT, CDC73, HNF1A, RBM10, ZMYM4 and ETV6) were identified in predicting relapse for the 3 patients, with recurrent mutations of the ETV6 gene in 2 patients. Functional analysis of the ETV6 mutation showed that ETV6 lost its tumour suppressive function when both mutant ETV6 p.P25fs and ETV6 p.N75fs were tested in vitro.

CONCLUSION: This study has uncovered the mutational landscape in three local childhood AML patients and contributes to a better understanding of the molecular mechanisms of relapsed AML.