(a) Two-dimensional hierarchical cluster analysis of differentially expressed transcripts. A total of 306 probe sets (columns) were identified using one-way analysis of variance (ANOVA) according to drug treatment (rows; two replicate cultures for each condition are denoted #1 and #2) at a 0.001 P-value threshold (expected number of false positives, 12). The hierarchical cluster dendrogram was calculated using Pearson's correlation as a distance metric and the Centroid linkage method, as implemented in dChip software. Signal intensities of each probe set were normalized across samples and color-coded according to standard deviations above (red) or below (blue) the mean. (b) Venn diagrams of differentially expressed transcripts in Kasumi-1 cells after equivalent low-dose treatment with 5AC, DAC or Zeb. The number in each area of the diagrams indicates probe set targets that were differentially expressed between treated and untreated cells (left diagram, upregulated; right diagram, downregulated). Transcripts that showed a response also to treatment with AraC were excluded to account for cytotoxic effects unrelated to DNA methyltransferase inhibition.