The 4th EMBL Conference: Cancer Genomics (4 – 6 November 2019) brought together over 240 scientists in the field of cancer research to present the latest findings in cancer functional genomics, systems biology, cancer immunogenomics and epigenomics, as well as their translation and clinical impact.
123 posters were presented at the two poster sessions, out of which two were selected as the winners by popular vote.
Infinite sites violations during tumour evolution reveal local mutational determinants
Authors: Jonas Demeulemeester (1), Stefan C. Dentro (2), Moritz Gerstung (2), Peter Van Loo (1)
The infinite sites model of molecular evolution requires that every base in the genome is mutated at most once. It is a cornerstone of (tumour) phylogenetic analysis, and is often implied when calling, phasing and interpreting variants or studying the mutational landscape as a whole. It is unclear however, whether this assumption holds in practice for bulk tumour samples. Here we provide frameworks to model and detect infinite sites violations, identifying 24,459 in total, including 6 candidate biallelic driver events, in 700 bulk tumour samples (26.3%) from the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes project. Violations generally occur at mutational hotspots and their frequency and type can accurately be predicted from the overall mutation spectrum. In melanoma, their local sequence context evidences how not only ETS, but also NFAT-family transcription factor binding creates hotspots for UV-induced cyclobutane pyrimidine dimer formation. In colorectal adenocarcinoma, violations reveal hypermutable special cases of the trinucleotide mutational contexts identified in POLE-mutant tumours. Taken together, we reveal the infinite sites model breaks down at the bulk level for a considerable fraction of tumours. These results warrant a careful evaluation of current pipelines relying on the validity of the infinite sites assumption, especially when scaling up to larger sets of mutations and lineages in the future.
(1) The Francis Crick Institute, United Kingdom, (2) EMBL-EBI, United Kingdom
The other award-winning poster was:
Understanding the early impact of activating PIK3CA mutation on cellular and genetic heterogeneity presented by Evelyn Lau, UCL Cancer Institute, United Kingdom
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