Figure 5.

Methylation profiles of 227 B-ALL cases analyzed by Illumina 450k array. (A) A hierarchical clustering analysis using 500 most variable CpGs classifies the tumors into four distinct clusters. Some clusters are dominated by specific cytogenetic groups; cluster I by hyperdiploid, cluster II by others, cluster III by ETV6/RUNX1, and cluster IV by hyperdiploid/others. (B) Local regression of the methylation differences illustrates that each methylation cluster has different degrees of CGI methylation in each cytogenetics group. (C) Among the four methylation clusters, many DMRs are shared while some DMRs were cluster-specific. (D) Mean methylation at SUZ12-binding sites significantly correlates with mean expression of polycomb target genes (9) (r = −0.276; P = 0.020), suggesting a role of de novo methylation at polycomb sites for repressing their target genes.