Unknown,Transcriptomics,Genomics,Proteomics

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Effect of tamoxifen on early gene expression in MDA-MB-231 cells

ABSTRACT: Tamoxifen is the treatment of choice in estrogen receptor alpha breast cancer patients. However, ~50% of ERM-NM-1-positive tumors exhibit intrinsic or rapidly acquire resistance to endocrine treatment, requiring chemotherapy. M-NM-^Yt 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 manufacturerM-bM-^@M-^Ys 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.

ORGANISM(S): Homo sapiens

SUBMITTER: George Notas

PROVIDER: E-GEOD-60879 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:ERM-NM-117p is a synthetic peptide corresponding to the sequence P295LMIKRSKKNSLALSLT311 of the estrogen receptor alpha (ERM-NM-1) and initially synthesized to mimic its calmodulin binding site. ERM-NM-117p was subsequently found to elicit estrogenic responses in E2-deprived ERM-NM-1-positive breast cancer cells, increasing proliferation and E2-dependent gene transcription. Surprisingly, in E2-supplemented media, ERM-NM-117p induced apoptosis and modified the actin network, influencing thereby cell motility. Here, we report that ERM-NM-117p induces a massive early (3h) transcriptional activity in breast cancer cell lines SKBR3). Remarkably, about 75% of the significantly modified transcripts were also modified by E2, confirming the pro-estrogenic profile of ERM-NM-117p. The different ER spectra of the used cell lines allowed us to extract a specific ERM-NM-117p signature related to ERM-NM-1 and its variant ERM-NM-136. With respect to ERM-NM-1, the peptide activates nuclear (cell cycle, cell proliferation, nucleic acid and protein synthesis) and extranuclear signaling pathways. In contrast, through ERM-NM-136 it exerts inhibitory events on inflammation and cell cycle and inhibition of EGFR signaling. This is the first work reporting ERM-NM-136 specific transcriptional effects. The fact that a number ERM-NM-117p-induced transcripts is different from those activated by E2 revealed that the apoptosis and actin modifying effects of ERM-NM-117p are independent from the ER-related actions of the peptide. Cells after a 4h incubation with medium containing 10% charcoal stripped FBS were incubated with or without E2 (10-6M) or ERa17p 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 manufacturerM-bM-^@M-^Ys 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.

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Effect of tamoxifen on early gene expression in MDA-MB-231 cells

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