BMC Genomics 2007, 8:117 http://www.biomedcentral.com/1471-2164/8/117 FGilgoubraletr2anscriptional relationships among tissue samples and cell lines indicate high reproducibility of replicates Global transcriptional relationships among tissue samples and cell lines indicate high reproducibility of repli- cates. A: Hierarchical clustering of samples by their expression profiles. Labels with "a" and "b" represent technical replicates, whereas numbered labels represent biological replicates. The primary separation occurs between cell lines (dashed bar) and cervical tissue (solid bar). All GOG samples and CHTN samples #1, 2, 8, 12 and 13 were invasive cervical cancer biopsies. CHTN samples #6, 10, and 11 were normal cervix. Most replicates clustered together, indicating the data was of high quality. Spots present on the microarray that had a median intensity over background of at least 150 and were present in 80% of the arrays were included in the analysis, resulting in 8,338 genes. B: Singular value decomposition of transcriptional profiles reveals general relationships among the samples, positioned here as the projections among the first 3 singular components (accounting for 40% of the variance, [see Additional file 6]. Again, cell lines were separated from cervical tissue. Page 5 of 13 (page number not for citation purposes)