CTCF haploinsufficiency also destabilises DNA methylation at epigenetically variable CpGs in normal tissues.25 It is not clear what specific effects this global epigenetic instability would have on endometrioid cells, but such deregulation may accelerate carcinogenesis, and is indeed recognised as an enabling factor in cancer.44 Paradoxically we show that knockdown of CTCF can have both pro-tumourigenic (deregulation of cellular polarity) and anti-tumourigenic (inhibition of clonogenicity) activities. This evidence concerns the gene CTCF and cancer.