Differential gene expression in cancerous samples. (a) Box plot of fold changes in expression levels from genes in list L863. A red line represents the average; a black line, the median. The 1st quartiles, 3rd quartiles, minimum and maximum values are indicated; the ratios are shown in absolute values. (b) Venn diagram representation of the co-occurring genes with differential expressions computed through statistical comparisons of subgroups of colon tumors (T), liver metastases (M) or both cancerous tissues together (T&M) (α = 0.01). The number of clones representing genes that were found significantly differentially expressed between chemo-sensitive and resistant states is indicated. (c) Clustering analysis on cancerous samples of the expression profiles of the genes in list L863. Genes (row) and samples (columns) are clustered independently using Pearson correlation. The top color patch represents primary drug responses, either chemo-sensitive (in blue) or resistant (in red). The top-ranked relevant gene clusters selected using t statistics with permutation-based adjustment (n = 10,000; α = 0.05) are indicated by color bars.