Conversely, using preclinical mouse models, we and others demonstrated that ectopic DLL4 expression in hematopoietic stem cells (HSCs) or T cells leads to spontaneous T-ALL development 6, 7 that is preceded by accumulation of non-clonal double-positive CD4+CD8+ cells in the circulation 6, 7. The gene discussed is DLL4; the disease is acute lymphoblastic leukemia.