title: Elevated nuclear expression of the SMRT corepressor in breast cancer is associated with earlier tumor recurrence.
abstract: Silencing mediator of retinoic acid and thyroid hormone receptor (SMRT), also known as nuclear corepressor 2 (NCOR2) is a transcriptional corepressor for multiple members of the nuclear receptor superfamily of transcription factors, including estrogen receptor-α (ERα). In the classical model of corepressor action, SMRT binds to antiestrogen-bound ERα at target promoters and represses ERα transcriptional activity and gene expression. Herein SMRT mRNA and protein expression was examined in a panel of 30 breast cancer cell lines. Expression of both parameters was found to vary considerably amongst lines and the correlation between protein and mRNA expression was very poor (R                 (2) = 0.0775). Therefore, SMRT protein levels were examined by immunohistochemical staining of a tissue microarray of 866 patients with stage I-II breast cancer. Nuclear and cytoplasmic SMRT were scored separately according to the Allred score. The majority of tumors (67 %) were negative for cytoplasmic SMRT, which when detected was found at very low levels. In contrast, nuclear SMRT was broadly detected. There was no significant difference in time to recurrence (TTR) according to SMRT expression levels in the ERα-positive tamoxifen-treated patients (P = 0.297) but the difference was significant in the untreated patients (P = 0.01). In multivariate analysis, ERα-positive tamoxifen-untreated patients with high nuclear SMRT expression (SMRT 5-8, i.e., 2nd to 4th quartile) had a shorter TTR (HR = 1.94, 95 % CI, 1.24-3.04; P = 0.004) while there was no association with SMRT expression for ERα-positive tamoxifen-treated patients. There was no association between SMRT expression and overall survival for patients, regardless of whether they received tamoxifen. Thus while SMRT protein expression was not predictive of outcome after antiestrogen therapy, it may have value in predicting tumor recurrence in patients not receiving adjuvant tamoxifen therapy.
authors.affiliation: Department of Molecular & Cellular Biology, BCM130, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. carolyns@bcm.edu
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Smith
authors.forename: Ilenia
authors.initials: I
authors.lastname: Migliaccio
authors.forename: Vaishali
authors.initials: V
authors.lastname: Chaubal
authors.forename: Meng-Fen
authors.initials: MF
authors.lastname: Wu
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Pace
authors.forename: Ryan
authors.initials: R
authors.lastname: Hartmaier
authors.forename: Shiming
authors.initials: S
authors.lastname: Jiang
authors.forename: Dean P
authors.initials: DP
authors.lastname: Edwards
authors.forename: M Carolina
authors.initials: MC
authors.lastname: Gutiérrez
authors.forename: Susan G
authors.initials: SG
authors.lastname: Hilsenbeck
authors.forename: Steffi
authors.initials: S
authors.lastname: Oesterreich
mesh_terms: D001943:Breast Neoplasms / Q000188:drug therapy / Q000453:epidemiology / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009367:Neoplasm Staging; D056985:Nuclear Receptor Co-Repressor 2 / Q000235:genetics / Q000378:metabolism*; D016019:Survival Analysis; D013629:Tamoxifen / Q000008:administration & dosage; D046888:Tissue Array Analysis
chemical_list: C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D056985:Nuclear Receptor Co-Repressor 2; D013629:Tamoxifen