The leukemia was attributed to the higher propensity of RV to integrate near gene promoters, and the viral enhancers in the long terminal repeats (LTR) of RV enhance gene expression of the transgene and surrounding genes ubiquitously; this resulted in overexpression of the proto-oncogene LIM domain-only 2 (LMO2), where the RV had integrated. This evidence concerns the gene LMO2 and leukemia.