DNA microarray analysis identifies a homogeneous p53-dependent gene expression response of CLL cells to treatment with fludarabine in vivo. Changes in gene expression are depicted for each gene relative to its pretreatment level (black squares). Shades of red and green indicate up- or down-regulation of a given gene according to the color scheme shown below. Sequence-verified Lymphochip clones are labeled with an asterisk (*). For unnamed genes IMAGE clone numbers (IM) are given. Unnamed genes without sequence verification are labeled with a Lymphochip (LC) number.