IKZF1 and acute lymphoblastic leukemia: To further studies on the function of Ik-6, we characterized the IKZF1 transcript pattern in lymphoblastic leukemia cell lines and identified SUP-B15 as an Ik-6 bearing line that also shows an IKZF1 transcript with a C-terminal 14 bp frameshift insertion in exon 8 and produces only a truncated IKZF1 protein with no wild-type IKZF1 protein.