CTCF and cancer: CTCF binding sites are among the most common TFBSs in the genome (S1 Dataset), and we found the CTCF-motif to be recurrently mutated at position 9 across cancer types (Fig 3A), a pattern that was previously seen in CTCF-TFBSs identified via Chip-exo of CTCF in a colorectal cell line [10].