CTCFL and cancer: However, mapping of CTCF and BORIS binding by ChIP-seq in human cancer and mouse germ cells revealed the existence of distinct classes of binding sites: 1xCTSes, containing a single motif and bound by CTCF alone (CTCF-only sites), and 2xCTSes, containing two or more clustered motifs and simultaneously bound by CTCF and BORIS (CTCF&BORIS sites) or BORIS alone (BORIS-only sites)30.