ERG is an oncogene that is over-expressed or translocated in cancer: ERG is indeed fused to TMPRSS2 promoter region in >50% of prostate cancer [360], to EWS in 10–15% of Ewing sarcoma [361] and to FUS/TLS or ELF4 in different subtypes of leukemia [362,363] and overexpressed in leukemia where it is associated with poor prognosis [364]. This evidence concerns the gene ELF4 and leukemia.