By contrast, constitutive activation of the IL-7/IL-7R axis can induce T-cell leukemogenesis [14], as evidenced by studies showing that transgenic mice overexpressing Il7 spontaneously develop T-cell lymphomas [15], that IL-7 induces proliferation and survival of human T-ALL cells [16–19] and that IL-7 accelerates disease progression in xenotransplant models of human T-ALL [20]. This evidence concerns the gene IL7R and acute lymphoblastic leukemia.