Estradiol and Selective Estrogen Receptor Modulators Differentially Regulate Target Genes with Estrogen Receptors and □D

Estrogens and selective estrogen receptor modulators (SERMs) interact with estrogen receptor (ER) and to activate or repress gene transcription. To understand how estrogens and SERMs exert tissue-specific effects, we performed microarray analysis to determine whether ER or ER regulate different target genes in response to estrogens and SERMs. We prepared human U2OS osteosarcoma cells that are stably transfected with a tetracycline-inducible vector to express ER or ER . Western blotting, immunohistochemistry, and immunoprecipitation studies confirmed that U2OS-ER cells synthesized only ER and that U2OS-ER cells expressed exclusively ER . U2OS-ER and U2OS-ER cells were treated either with 17 -estradiol (E2), raloxifene, and tamoxifen for 18 h. Labeled cRNAs were hybridized with U95Av2 GeneChips (Affymetrix). A total of 228, 190, and 236 genes were significantly activated or repressed at least 1.74-fold in U2OS-ER and U2OS-ER cells by E2, raloxifene, and tamoxifen, respectively. Most genes regulated in ER cells in response to E2, raloxifene, and tamoxifen were distinct from those regulated in ER cells. Only 38 of the 228 (17%) genes were regulated by E2 in both U2OS-ER and U2OS-ER cells. Raloxifene and tamoxifen regulated only 27% of the same genes in both the ER and ER cells. A subset of genes involved in bone-related activities regulated by E2, raloxifene, and tamoxifen were also distinct. Our results demonstrate that most genes regulated by ER are distinct from those regulated by ER in response to E2 and SERMs. These results indicate that estrogens and SERMs exert tissue-specific effects by regulating unique sets of targets genes through ER and ER .