Although not lethal, the loss of heterozygosity at the CTCF locus is also detrimental to cellular homeostasis (14), and CTCF appears to act as an haploinsufficent tumor suppressor gene (15, 16), with its loss impacting hematopoietic tumor initiation in CTCF hemizygous mice (15). Here, CTCF is linked to neoplasm.