ArrayExpress Uploader0human3 hours with 0.1% Ethanol3 hours with 10-6M estradiol3 hours with 10-6M tamoxifen4812arrayexpress_sid4Tamoxifen is the treatment of choice in estrogen receptor alpha breast cancer patients. However, ~50% of ERα-positive tumors exhibit...E-GEOD-60878/profile/8773/arrayexpressuploader13breastbreast cancercancercellestrogenlineDec.12, 2014Falseeffect-of-tamoxifen-on-early-gene-expression-in-t4E-GEOD-60878_A-AFFY-44Effect of tamoxifen on early gene expression in T47D cellsSep.21, 2014Tamoxifen is the treatment of choice in estrogen receptor alpha breast cancer patients. However, ~50% of ERα-positive tumors exhibit intrinsic or rapidly acquire resistance to endocrine treatment, requiring chemotherapy. Ιt has been difficult to predict de novo resistance to endocrine therapy and/or assess the likelihood of early relapse, while no concrete mechanism regulating the acquisition and the maintenance of endocrine resistance has been identified. We have performed a whole transcriptome analysis of an ER-positive (T47D) and a triple-negative (MDA-MBA-231) breast cancer cell line exposed to tamoxifen for a short time frame (hours) in order to study resistance mechanisms that are initiated early after initiation of tamoxifen treatment. Cells after a 4h incubation with medium containing 10% charcoal stripped FBS were incubated with vehicle, E2 (10-6M) or tamoxifen (10-6M) in RPMI 1640 supplemented with 10% charcoal stripped FBS, for 3 hours. Total RNA was isolated using Nucleospin II columns (Macheray-Nagel, Dttren, Germany), according to the manufacturer’s instructions. RNA was labeled and hybridized according to the Affymetrix protocol (Affymetrix Gene-Chip Expression Analysis Technical Manual), using the HGU133A plus 2 chip, analyzing a total of 54675 transcripts. Signals were detected by an Affymetrix microarray chip reader.http://www.ebi.ac.uk/arrayexpress/experiments/E-GEOD-60878http://www.ebi.ac.uk/arrayexpress/experiments/E-GEOD-60878/samples/