The regions that, in wild-type cells, bind Cp190 but no CTCF (e.g., MCS, MCI, MCIS, and CIS) become systematically easier to cross (negative Δγ) only in the Cp190-KO (Fig. 4B) but not in the CTCF-KO cells (Fig. 4C). This evidence concerns the gene CTCF and in situ carcinoma.