Moreover, beside BACH2 and STAT5B, it is unclear why genes such as LMO2, TAL1, CCND2, BMI1 and others, that are well-known players in spontaneously or vector-induced T cell leukemia in γ-retroviral vector-based HSC gene therapy patients36–39, are not among the culprits of HIV-mediated insertional mutagenesis. The gene discussed is STAT5B; the disease is T-cell leukemia.