title: Gene expression preferentially regulated by tamoxifen in breast cancer cells and correlations with clinical outcome.
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.
authors.affiliation: Department of Molecular and Integrative Physiology and Cell and Developmental Biology, University of Illinois and College of Medicine, Urbana, Illinois 61801-3704, USA.
authors.forename: Jonna
authors.initials: J
authors.lastname: Frasor
authors.forename: Edmund C
authors.initials: EC
authors.lastname: Chang
authors.forename: Barry
authors.initials: B
authors.lastname: Komm
authors.forename: Chin-Yo
authors.initials: CY
authors.lastname: Lin
authors.forename: Vinsensius B
authors.initials: VB
authors.lastname: Vega
authors.forename: Edison T
authors.initials: ET
authors.lastname: Liu
authors.forename: Lance D
authors.initials: LD
authors.lastname: Miller
authors.forename: Johanna
authors.initials: J
authors.lastname: Smeds
authors.forename: Jonas
authors.initials: J
authors.lastname: Bergh
authors.forename: Benita S
authors.initials: BS
authors.lastname: Katzenellenbogen
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D015331:Cohort Studies; D047628:Estrogen Receptor alpha / Q000235:genetics; D047629:Estrogen Receptor beta / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006801:Humans; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D020845:Selective Estrogen Receptor Modulators / Q000494:pharmacology*; D013629:Tamoxifen / Q000494:pharmacology*; D016896:Treatment Outcome
chemical_list: D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D020845:Selective Estrogen Receptor Modulators; D013629:Tamoxifen