H19 and cancer: A number of CTCF ZF mutations previously identified in isolated cancers were shown to inhibit CTCF binding to specific DNA binding sites such as CMYC and IGF2/H19 regulatory regions while binding to other sites such as the β-globin and APPβ regulatory regions was unaffected.10 In endometrial carcinoma these missense mutations appear to cluster within ZFs 4–5 of CTCF.