Genetic mutational analysis of pediatric acute lymphoblastic leukemia from a single center in China using exon sequencing

BACKGROUND: Acute lymphoblastic leukemia (ALL), the most common childhood malignancy, is characterized by recurring structural chromosomal alterations and genetic alterations, whose detection is critical in diagnosis, risk stratification and prognostication. However, the genetic mechanisms that give rise to ALL remain poorly understood. METHODS: Using next-generation sequencing (NGS) in matched germline and tumor samples from 140 pediatric Chinese patients with ALL, we landscaped the gene mutations and estimated the mutation frequencies in this disease. RESULTS: Our results showed that the top driver oncogenes having a mutation prevalence over 5% in childhood ALL included KRAS (8.76%), NRAS (6.4%), FLT3 (5.7%) and KMT2D (5.0%). While the most frequently mutated genes were KRAS, NRAS and FLT3 in B cell ALL (B-ALL), the most common mutations were enriched in NOTCH1 (23.1%), FBXW7 (23.1%) and PHF6 (11.5%) in T cell ALL (T-ALL). These mutant genes are involved in key molecular processes, including the Ras pathway, the Notch pathway, epigenetic modification, and cell-cycle regulation. Strikingly, more than 50% of mutations occurred in the high-hyperdiploid (HeH) ALL existed in Ras pathway, especially FLT3 (20%). We also found that the epigenetic regulator gene KMT2D, which is frequently mutated in ALL, may be involved in driving leukemia transformation, as evidenced by an in vitro functional assay. CONCLUSION: Overall, this study provides further insights into the genetic basis of ALL and shows that Ras mutations are predominant in childhood ALL, especially in the high-hyperdiploid subtype in our research.