CTCF is encoded on chromosome 16, which is rarely gained2, whereas the core members of the cohesin complex are all encoded on commonly gained chromosomes (8q24 for RAD21, 10q25 for SMC3, Xp11 for SMC1A and Xq25 for STAG2); thus, the specific aneuploidy in high hyperdiploid ALL may cause relatively low expression of CTCF but not of cohesin. This evidence concerns the gene RAD21 and acute lymphoblastic leukemia.