In fact, the oncogene EVI1 was first identified as a murine retroviral insertion site causing myeloid leukemia in mice as a result of Evi1 overexpression.100–103 In this particular setting, the recombinant vector integrated within the vicinity of the Evi1 promoter, resulting in the powerful enhancer elements encoded in the viral long terminal repeats driving expression of the Evi1 transcript. This evidence concerns the gene MECOM and myeloid leukemia.