CTCF has been established as a tumour suppressor gene due to its ability to suppress cancer cell growth.15, 17, 25 Along with PTEN, TP53, PIK3CA, CTNNB1 and ARID1A, CTCF has been classified as a significantly mutated gene in endometrial cancer.8Ctcf haploinsufficient mice, which are tumour prone, also develop endometrial cancers.25 These observations firmly implicate CTCF mutation and haploinsufficiency in endometrial carcinoma pathogenesis. Here, ARID1A is linked to cancer.