While c-Jun is an oncogene overexpressed or amplified in different types of cancer, including sarcomas [61], it has been demonstrated that conditional JunB inactivation [62], [63] or PU.1 related downregulation of both JunB and c-Jun [64] provoke myeloproliferative disorders and different types of leukemia in mice. This evidence concerns the gene JUN and leukemia.