DUX4 and cancer: It is not known why DUX4 is preferentially expressed in advanced-stage cancers, though transient expression of DUX4 transcriptional regulators DPPA2 and DPPA4 has been detected in cases, along with loss-of-function mutations in likely DUX4 repressors [13, 37], and it is possible that increased telomeric shortening derepresses DUX4 in a manner similar to that observed in cleavage-stage embryos [39].