GSE120166
Somatic mutation distributions in cancer genomes vary with three-dimensional chromatin structure
Somatic mutations arise during the life history of a cell. Mutations occurring in cancer driver genes may ultimately lead to the development of clinically detectable disease. Nascent cancer lineages continue to acquire somatic mutations throughout the neoplastic process and during cancer evolution. Extrinsic and endogenous mutagenic factors contribute to the accumulation of these somatic mutations. Understanding the underlying causes of mutations is critical for developing potential preventions and tailoring the clinical treatments. Earlier studies have revealed that DNA replication timing and chromatin modifications are associated with variations in mutational density. In order to understand the interplay between spatial genome organization and individual mutational processes, we report here a study of more than 3000 whole genome datasets from 50 different cancer studies. Our analyses revealed that different mutational processes lead to distinct somatic mutation distributions between chromatin folding domains. APOBEC- or MSI-related mutations are enriched in transcriptionally-active domains while mutations occurring due to tobacco-smoke and ultraviolet (UV) light exposure or a gastric flux-related mutational signature (signature 17) enrich predominantly in transcriptionally-inactive domains. Active mutational processes dictate the mutation distributions in cancer genomes, therefore mutational distributions could shift during cancer evolution upon mutational processes switch. Moreover, a dramatic instance of extreme chromatin structure in humans, that of the unique folding pattern of the inactive X-chromosome leads to distinct somatic mutation distribution on X chromosome in females compared to males in various cancer types. Overall, the interplay between three-dimensional genome organization and active mutational processes has a substantial influence on the large-scale mutation rate variations observed in human cancer. Overall design: Profiling chromatin conformation dynamics in 4 cancer cell lines.