In our search for potential partners of IK, we discovered that 15 transcripts representing 12 IK-regulated lymphoid priming genes were significantly upregulated in human lymphocyte precursor cells from primary bone marrow specimens of pediatric patients with B-lineage ALL expressing high levels of both IKZF1/IK and BTK genes (Figure S1 in File S1). This evidence concerns the gene BTK and acute lymphoblastic leukemia.