Unsupervised analysis shows clustering of primary samples into their biologic groups based on their HELP assay–determined methylome. Using raw data from the HELP assay, unsupervised analysis was performed on primary samples (Table 1). The MLL-r leukemia samples cluster together (black), the other (MLL-wt) ALL samples cluster together (white), and the normals cluster together (gray). This demonstrates that there are remarkable intragroup similarities and intergroup differences in promoter methylation patterns, and that these patterns are based on the underlying biology of the groups (determined primarily by recurrent cytogenetic abnormalities in the leukemias, or by lineage differentiation for the normals).