Discovery of Cis-Regulatory Mechanisms via Non-Coding Mutations in Acute Lymphoblastic Leukemia.

The non-coding genome, constituting 98% of human DNA, remains largely unexplored, yet holds potential for identifying new biomarkers and therapeutic targets in acute lymphoblastic leukemia (ALL). In this study, we conducted a systematic analysis of recurrent somatic non-coding single nucleotide variants (SNVs) in pediatric B-cell precursor (BCP) ALL. We leveraged whole genome sequencing (WGS) data from 345 pediatric BCP ALL cases, representing all major genetic subtypes and identified 346 mutational hotspots that harbored somatic SNVs in at least three cases. Through the integration of paired RNA sequencing along with published ChIP-seq and ATAC-seq data, we found 128 non-coding hotspots associated with differentially expressed genes nearby, which were enriched for cis-regulatory elements, demonstrating the effectiveness of multi-omics integration in distinguishing pathogenic mutations from passengers. We identified one mutational hotspot that was associated with increased expression of the leukemia-associated gene NRAS in three primary ALLs. Micro-C analysis in the leukemia cell line demonstrated interactions between the hotspot region and NRAS regulatory elements. Dual luciferase assays indicated that the mutations disrupted regulatory interactions and CRISPR-mediated deletion of the region significantly upregulated NRAS, confirming the hypothesized regulatory link. Altogether, we provide new insights into the functional roles of non-coding mutations in leukemia.