Gene Set: FRASOR_TAMOXIFEN_RESPONSE_DN

Standard name FRASOR_TAMOXIFEN_RESPONSE_DN
Systematic name M5082
Brief description Genes preferentially down-regulated in MCF-7 cells (breast cancer) by tamoxifen [PubChem=5376] but not by estradiol or fulvestrant (ICI 182780) [PubChem=5757;3478439].
Full description or abstract The beneficial effect of the selective estrogen receptor (ER) modulator tamoxifen in the treatment and prevention of breast cancer is assumed to be through its ability to antagonize the stimulatory actions of estrogen, although tamoxifen can also have some estrogen-like agonist effects. Here, we report that, in addition to these mixed agonist/antagonist actions, tamoxifen can also selectively regulate a unique set of >60 genes, which are minimally regulated by estradiol (E2) or raloxifene in ERalpha-positive MCF-7 human breast cancer cells. This gene regulation by tamoxifen is mediated by ERalpha and reversed by E2 or ICI 182,780. Introduction of ERbeta into MCF-7 cells reverses tamoxifen action on approximately 75% of these genes. To examine whether these genes might serve as markers of tamoxifen sensitivity and/or the development of resistance, their expression level was examined in breast cancers of women who had received adjuvant therapy with tamoxifen. High expression of two of the tamoxifen-stimulated genes, YWHAZ/14-3-3z and LOC441453, was found to correlate significantly with disease recurrence following tamoxifen treatment in women with ER-positive cancers and hence seem to be markers of a poor prognosis. Our data indicate a new dimension in tamoxifen action, involving gene expression regulation that is tamoxifen preferential, and identify genes that might serve as markers of tumor responsiveness or resistance to tamoxifen therapy. This may have a potential effect on the choice of tamoxifen versus aromatase inhibitors as adjuvant endocrine therapy.
Collection C2: curated gene sets
      CGP: chemical and genetic perturbations
Source publication Pubmed 16849584   Authors: Frasor J,Chang EC,Komm B,Lin CY,Vega VB,Liu ET,Miller LD,Smeds J,Bergh J,Katzenellenbogen BS
Exact source Table 1BS
Related gene sets (show 1 additional gene sets from the source publication)

(show 31 gene sets from the same authors)
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Organism Homo sapiens
Contributed by Arthur Liberzon (Broad Institute)
Source platform HG-U133A
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Compendia expression profiles Human tissue compendium (Novartis)
NCI-60 cell lines (National Cancer Institute)
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Version history 3.0: First introduced

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