Investigations had revealed frequent lentiviral vector integration into proto-oncogenes at sites such as MECOM (resulting in increased expression of EVI1) and presence of somatic mutations (KRAS, NRAS, WT1, CDKN2A or CDKN2B, or RUNX1) in 6 out of 7 patients with leukaemia, while one patient had chromosome 7 monosomy. This evidence concerns the gene RUNX1 and leukemia.