Association of elevated gene expression of CRLF2 with JAK mutations and IKZF1 alteration in high-risk B-progenitor ALL. (A) CRLF2 expression levels generated by Affymetrix gene expression profiling (circles) in 207 high-risk B-precursor ALL patients. y-axis represents CRLF2 intensity; x-axis, 207 ALL patients ordered from lowest to highest CRLF2 expression levels. Red circles represent samples with CRLF2 rearrangement; blue circles, patients with no detectable CRLF2 rearrangements; and yellow triangles, patients with IKZF1 alterations. Dashed box highlights samples with CRLF2 expression levels more than 10-fold higher than the median level. (B) Expanded view of the 29 ALL cases with CRLF2 rearrangement showing the association of CRLF2 rearrangement with IKZF1 alterations (yellow triangles), and mutations in JAK1 (orange diamonds) or JAK2 (blue diamonds). Detailed information on each of the 29 cases may be found in Table 2.