Using high-resolution single-nucleotide polymorphism (SNP) arrays and genomic DNA sequencing, Mullighan et al. [7–10] and other groups revealed that alterations in genes encoding transcriptional regulators of B-lymphocyte development and differentiation, including PAX5, EBF1, and IKZF1, were observed in approximately 40% of patients with BCP-ALL. Here, IKZF1 is linked to acute lymphoblastic leukemia.