Estrogen-modulated genes and their co-expression in estrogen receptor-positive primary breast cancers. The log ratios of the four experimentally confirmed, estrogen-induced genes (a) LIV-1, (b) TFF1, (c) PGR and (d) AREG were plotted against ESR1 from the van't Veer and colleagues data . Data for genes shown to be repressed by estrogen treatment in MCF-7 cells  are also plotted against ESR1: (e) TGFβ2 and (f) NDRG1. The samples are colored by group, as in Figs 3 and 4. Only values for the five subgroups of sporadic tumors (n = 78) are plotted and used for the R 2 calculations. The data for the BRCA1/BRCA2 subgroup (dark green) are not shown.