Presented by Dr. Jayne Barbour (University of Hong Kong) Mutations acquired in cancer genomes form distinct patterns. CTCF-cohesin binding sites (CBS), or DNA loop anchors, and are vulnerable to accumulating mutations. To explore why CBS are vulnerable to mutagenesis we performed analysis of somatic mutation densities in CBS on 1980 whole-genome sequenced cancer samples. We found three groups of samples with enriched CBS mutations densities: skin, gastrointestinal and XPD mutant bladder cancers. XPD is a DNA helicase that is part of TFIIH and mutated in about 10% of bladder cancer. XPD mutant samples displayed elevated mutation densities in accessible chromatin and at transcriptionally active CBS. In a separate project, we tested if a germline mutation in a specific CBS in the CDKN2B locus is important in melanoma. Dermal fibroblasts from a family of sporadic melanoma harbouring this variant were cultured and we performed CTCF ChIP-seq, HiC and RNA-seq. We observed allele-specific loss of CTCF binding suggesting the variant is functional.