CTCF and cancer: One possible hallmark of CTCF-altered endometrial cancers is the downregulation of tumour suppressor genes including PIK3CA, CDKN2A, CDH6 and IGF2BP2. The tumour suppressor PIK3CA is ranked fifth after CTCF in the most frequently mutated genes in UCEC [6] whilst CDKN2A is downregulated in POLE, MSI, and copy-number low cancers compared to high-copy number cancers [28].