Hierarchical clustering of samples from colorectal tumors and normal colon epithelia. On the right, you find the chromosomal localization of the genes and the official HUGO symbol or prospective Affymetrix cluster ID. On the top, the binary tree of tissue samples based on gene expression is given. The tissue denominators either contain TR for tumor or E for epithelium and a code reflecting the identity of each patient. In the center, the expression values after normalization have been color-coded: light blue means high expression, black means low (or no) expression. Note that only a representative fraction of the 514 genes is visualized here (white bars replace some portions of original heat map). The right cluster contains only samples from normal colon epithelia, the left cluster is composed primarily of tumors along with some interspersed normal epithelial samples. Note that misplaced normal tissue (E) samples often cluster along with matching tumor (TR) samples from the same patient.
Staub et al. Molecular Cancer 2006 5:37 doi:10.1186/1476-4598-5-37