ARID1A and endometrial cancer: 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.