The analyses of leukemia genomes, however, uncovered that the most prominent group of genes to become defective in B cell precursor leukemia (B-cell precursor acute lymphoblastic leukemia [BCP-ALL] or B-lymphoid acute lymphoblastic leukemia [B-ALL]) are regulators of B cell development (40% in B-ALL and 66%–68% in high-risk B-ALL (Mullighan et al., 2007, Mullighan et al., 2009, Zhang et al., 2011)), with the transcription factors PAX5 and IKZF1 being altered in ∼32% and ∼29% of cases in high-risk B-ALL, respectively (Mullighan et al., 2009). Here, PAX5 is linked to acute lymphoblastic leukemia.