E2 increased sellectchem the expression of 897 genes by 1. 5 fold in MCF7 EGFR cells after 6 hr, while a similar number of Inhibitors,Modulators,Libraries genes was 1. 5 fold lower expressed compared to controls. The number of genes induced or decreased by EGF was slightly higher. As expected, TAM greatly reduced the number of genes 1. 5 fold up or down regulated by E2. TAM hardly affected the number of EGF regulated genes. TAM, however, had a significant effect on the number of genes regulated by combined E2 EGF exposure due to down regulation of E2 responsive genes. In order to further characterize the inhibitory effect of TAM on E2 regulated genes, we calculated the percentage of inhibition by TAM for each gene. The inhibition by TAM of E2 induced genes was large the expression of more than 65% of E2 up regulated genes was inhibited by TAM by 50%.

Interestingly, the effect of TAM on genes up regulated by Inhibitors,Modulators,Libraries E2 under Inhibitors,Modulators,Libraries the condition of combined E2 EGF exposure was almost as big as with exposure to E2 alone. This indicates that the inhibitory effect of TAM is only slightly affected by exposure of the cells to EGF. In general, similar observations were made for the inhibitory effect of TAM on E2 down regulated genes as for E2 up regulated genes. Further analysis of the E2 and EGF regulated genes showed that the identity of E2 and EGF induced genes are different most genes up regulated by E2 are not induced by EGF. Many known E2 regulated genes such as TFF1, PGR, GREB1 and MYC belong to this class. Similarly, the majority of EGF induced genes is not induced by E2. However, there is number of genes that is up regulated 1.

5 fold by both E2 and EGF, and for part of these, there is a synergistic effect of E2 and EGF. Analysis with Metacore software suggests that the most important transcription factors for these genes are AR, c JUN, c MYC, EGR1, ESR1, HIF1A, p53 and SP1, which is consistent with the cell proliferation pathways activated by E2 and EGF. Furthermore, there is a relatively Inhibitors,Modulators,Libraries large number of genes induced by combined E2 EGF exposure that is not induced by E2 or EGF Inhibitors,Modulators,Libraries alone. This most likely is also due to a synergistic effect of E2 and EGF because 60% of these genes are already induced by E2 or EGF alone but just below the threshold of 1. 5 fold. Conversely, there is also an antagonistic effect because best some of the E2 up regulated genes are down regulated by EGF, and visa versa. In conclusion, the majority of genes are uniquely induced by either E2 or EGF and only for a limited number of genes there is an agonistic or antagonistic effect. Similar conclusions can be drawn for E2 and EGF down regulated genes.