Unknown,Transcriptomics,Genomics,Proteomics

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Under conditions of hormonal adjuvant treatment the estrogen receptor apoprotein supports breast cancer cell cycling through the retinoic acid receptor M-NM-11 apoprotein

ABSTRACT: Under conditions of hormonal adjuvant treatment the estrogen receptor apoprotein supports breast cancer cell cycling through the retinoic acid receptor M-NM-11 apoprotein. Basal proliferation persisted in estrogen-sensitive breast cancer cells grown in hormone depleted conditioned media without or with 4-hydroxytamoxifen (OH-Tam). Downregulating ER using siRNA inhibited basal proliferation by promoting cell cycle arrest. The basal expression of RARM-NM-11, the only RARM-NM-1 isoform that was expressed in breast cancer cell lines and in most breast tumors, was supported by apo-ER but was unaffected by OH-Tam. The overlapping tamoxifen-insensitive gene regulation by apo-ER and apo-RARM-NM-11 comprised activation of mainly genes promoting cell cycle and mitosis and suppression of genes involved in growth inhibition. Cells were plated at 20% confluence in low glucose phenol red free medium supplemented with 5% charcoal stripped FBS and glutamine 24h-48h prior to transfection. Treatment with vehicle, OH-Tam (100nM), or OH-Tam (500nM) was begun an additional 24h later. Cells were transfected with control siRNA, ERM-NM-1 siRNA or RARM-NM-1 siRNA.

ORGANISM(S): Homo sapiens

SUBMITTER: Robert Trumbly

PROVIDER: E-GEOD-26298 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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During hormone depletion or tamoxifen treatment of breast cancer cells the estrogen receptor apoprotein supports cell cycling through the retinoic acid receptor α1 apoprotein.

Salazar Marcela D MD Ratnam Maya M Patki Mugdha M Kisovic Ivana I Trumbly Robert R Iman Mohamed M Ratnam Manohar M

Breast cancer research : BCR 20110207 1

<h4>Introduction</h4>Current hormonal adjuvant therapies for breast cancer including tamoxifen treatment and estrogen depletion are overall tumoristatic and are severely limited by the frequent recurrence of the tumors. Regardless of the resistance mechanism, development and progression of the resistant tumors requires the persistence of a basal level of cycling cells during the treatment for which the underlying causes are unclear.<h4>Methods</h4>In estrogen-sensitive breast cancer cells the ef ...[more]

PMID: 21299862

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Project description:Breast cancer is a heterogeneous disease comprised of at least five major subtypes. Luminal subtype tumors confer a more favourable patient prognosis, which is in part, attributed to the Estrogen Receptor-alpha (ER) positivity and anti-hormone responsiveness of these tumors. Expression of the forkhead box transcription factor, FOXA1, also correlates with the luminal subtype and patient survival, but is present in a subset of ER-negative tumors. Similarly, FOXA1 is consistently expressed in luminal breast cancer cell lines even in the absence of ER. In contrast, basal breast cancer cell lines do not express FOXA1, and loss of FOXA1 in luminal cells increases migration and invasion, characteristics of the basal subtype. To delineate an ER-independent role for FOXA1 in maintaining the luminal phenotype, and hence a more favourable prognosis, we performed cDNA microarray analyses on luminal FOXA1-positive, ER-positive (MCF7, T47D) and FOXA1-positive, ER-negative (MDA-MB-453, SKBR3) cell lines in the presence or absence of transient FOXA1 silencing. This resulted in three FOXA1 transcriptomes: (1) a luminal-signature (consistent across cell lines), (2) an ER-positive signature (restricted to MCF7 and T47D) and (3) an ER-negative signature (restricted to MDA-MB-453 and SKBR3). Use of Gene Set Enrichment Analyses (GSEA) as a phenotyping tool revealed that FOXA1 silencing resulted in a transcriptome shift from luminal to basal gene expression signatures. FOXA1 binds to both luminal and basal genes within luminal breast cancer cells, suggesting that it not only transactivates luminal genes, but also represses basal-associated genes. From these results we conclude that FOXA1 controls plasticity between basal and luminal cells, playing a dominant role in repressing the basal phenotype, and thus tumor aggressiveness, in luminal breast cancer cells. Although it has been proposed that FOXA1-targeting agents may be useful for treating luminal tumors, these data suggest that this approach may promote transitions toward a more aggressive cancer. FOXA1 siRNA treated breast cell lines compared directly to nonspecific siRNA treated cell lines using Agilent 4X44 microarrays.

Dataset Information

Under conditions of hormonal adjuvant treatment the estrogen receptor apoprotein supports breast cancer cell cycling through the retinoic acid receptor M-NM-11 apoprotein

Publications

During hormone depletion or tamoxifen treatment of breast cancer cells the estrogen receptor apoprotein supports cell cycling through the retinoic acid receptor α1 apoprotein.

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