STAT5B and cancer: It is unclear why no oncogenesis events were ever found associated to HIV-mediated insertional mutagenesis despite the high number of HIV-infected patients studied thus far, the huge number of integration events occurring during years of infection in each patient and the roles in cell survival and proliferation of BACH2 and STAT5B. Indeed, these transcription factors control the function, homeostasis and development of several cell types of the immune system27, 28, and the overexpression of their wild-type forms alone has never been associated to cancer.