CRLF2 and precursor B-cell acute lymphoblastic leukemia: Importantly, detection of Ikaros isoform6 (IK6), produced by the most common type of IKZF1 deletion, was statistically higher in the B-ALL patients with high CRLF2 expression (31.0% vs. 8.3%, P = 0.019)(Supplementary Table 1).