OPN1SW and acute lymphoblastic leukemia: MLPA analysis revealed that among the 109 Philadelphia negative pediatric BCP-ALL patients tested, 17 (15.6%) patients harbor an IKZF1 deletion whereas one patient (0.9%) showed a gain of IKZF1. We generated kinase activity profiles of 31 IKZF1 wild type patients and 14 patients with an IKZF1 alteration (13 patients with an IKZF1 deletion and 1 patient with a gain of IKZF1).