Hierarchical clustering identifies similar clusters in an independent high-risk ALL cohort. Hierarchical clustering using 167 probe sets (provided in supplemental Table 7A) was used to identify clusters of patients with shared patterns of gene expression in a second cohort of high-risk ALL patients previously accrued to COG Trial CCG 1961. Rows indicate 99 patients from COG CCG 1961; and columns, 167 probe sets. Shades of red represent expression levels higher than the median; and green represents levels lower than the median. The cluster groups are prefixed by their method of probe set selection: H indicates high CV; C, COPA; and R, ROSE. (A) HC method for selection of probe sets. (B) COPA selection of probe sets. (C) ROSE selection of probe sets.