Gene expression signatures of estrogen regulation in vitro and in vivo. (a) Expression data matrix of genes showing either induction or repression by E2 in vitro (p < 0.01 at 4, 8, 12, or 24 hour time points). Each row represents a gene; each column represents a sample. The level of expression of each gene in each sample is represented using a yellow-blue color scale (yellow, high expression); gray indicates missing data. Shown alongside our in vitro time course dataset are the expression values for the corresponding genes in two independent mRNA profile datasets of E2-treated breast cells ('Rae' dataset from  of cell lines MCF-7, BT-474, and T47-D; 'Finlin' dataset from  of MCF-7). (b) Alongside the in vitro datasets are the corresponding values for MCF-7 xenografts with or without E2 supplementation (E2 withdrawn for 24 hours and 48 hours in the -E2 group). Genes in cluster 'B' (a) that show significant up-regulation by E2 in each of the four datasets are listed (an asterisk indicates positively correlated (p < 0.05) with age-correlation ERα expression (Figure 2); bold type indicates having higher expression in ERα+ compared to ERα- breast tumors (p < 0.01) according to the 'van't Veer' dataset from ); italics indicates having higher expression in ERα- compared to ERα+ breast tumors). (c) Genes MYB (c-myb) and MYBL1 (A-MYB) are regulated by E2 in vivo. Expression patterns for genes from (b) were validated by RT-PCR. Shown are the mean and standard deviation of individual samples assayed in triplicate. Tumor volumes (expressed in mm3) are shown above each bar.