Samples were obtrained from radical prostatectomy surgical procedures. Samples are labelled as ''tumors'' if they contain at least 90% of cancerous epithelial cells, and they were considered as ''non-tumor'' if they contain no tumor epithelium and are from the noncancerous region of the prostate. The later samples were labelled ''normals'' although the authors alert that some may contain dysplasia. In this dataset, Lapointe et al. have performed a gene expression profiling by using cDNA microarrays containing 26,260 different human genes (UniGene clusters). Using 50 mg of total RNA from prostate samples Cy5-labeled cDNA was prepared and Cy3-labeled cDNA used 1.5 mg of mRNA common reference, pooled from 11 human cell lines (see Ref. [792] ). The fluorescence ratios were subsequently normalized by mean centering genes for each array, a relatively standard procedure. In addition, to minimize potential print run specific bias, Lapointe et al. report that ratios were then mean centered for each gene across all arrays according to Ref. [793] . We have only used the genes that the authors report in their first figure, 5,153 genes that have been well measured and have significan variation in some of the samples. For the other details of their matrials and methods we refer the readers to the Supporting Notes and the Materials and Methods section of their original publication [44] .