MLL-rearranged infant ALL versus pediatric precursor B-ALL (HU133plus2.0). (A) Heatmap showing the separation of MLL-rearranged infant ALL (n = 59) from pediatric precursor B-ALL (n = 16) samples based on the 100 probe sets most significantly discriminative between both patient groups as attained in our analyses using HU133plus2.0 GeneChips. Columns represent patient samples, and rows represent the gene names corresponding to the probe sets. Normalized gene expression is depicted in red (high expression) or blue (low expression). The top 50 probe sets are relatively overexpressed and the bottom 50 probe sets relatively underexpressed in MLL-rearranged infant ALL (which include t(4;11) (n = 29), t(11;19) (n = 22), and t(9;11)-positive (n = 8) cases). (B) Graphic representation of PCA based on this gene expression signature, separating the MLL-rearranged infant ALL (red dots) from pediatric precursor B-ALL (blue dots) samples.