Therefore we set out to determine the molecular regulation of HSCs by Stat5 and understand whether the context of defective hematopoiesis in the absence of Stat5 could predispose toward initiation or progression of a classic non-Stat5 dependent Eμ-Myc/H2K-Bcl-2 driven murine B-lymphoblastic leukemia (B-ALL). This evidence concerns the gene STAT5A and precursor B-cell acute lymphoblastic leukemia.