Hypermethylated genes in leukemic cell lines belong to many functional groups. (A) Myeloid leukemia cell lines have increased CpG site methylation levels (β-values), and a high frequency of aberrantly methylated CpG sites, compared with normal CD34⁺ hematopoietic cells. The vertical boxes delineate the interquartile range in β-values; T bars, 95% range of values. The horizontal line in the boxes indicates the median values and the plus sign indicates the mean. The asterisk indicates significant β-value difference with CD34⁺ cells in a Tukey Studentized Range t test. The numbers below the graph are the number of aberrantly methylated loci (compared with normal CD34⁺ control). The text explains why the frequency of aberrant methylation may be underestimated if only β-values are analyzed. (B) Heat-map analysis showing the methylation β-values of 58 CpG loci that were concordantly hypermethylated in all 6 leukemia cell lines. Red, black, and green correspond to high, medium, and low methylation levels, respectively. Genes were grouped according to their functions: group I, apoptosis and cell cycle; group II, cell development; group III, cell proliferation and adhesion; group IV, cell differentiation; group V, chromosome architecture; group VI, signal transduction; and group VII, other.