title: Global microRNA expression profiling of high-risk ER+ breast cancers from patients receiving adjuvant tamoxifen mono-therapy: a DBCG study.
abstract: OBJECTIVE
  Despite the benefits of estrogen receptor (ER)-targeted endocrine therapies in breast cancer, many tumors develop resistance. MicroRNAs (miRNAs) have been suggested as promising biomarkers and we here evaluated whether a miRNA profile could be identified, sub-grouping ER+ breast cancer patients treated with adjuvant Tamoxifen with regards to probability of recurrence.
  
  
  METHODS
  Global miRNA analysis was performed on 152 ER+ primary tumors from high-risk breast cancer patients with an initial discovery set of 52 patients, followed by two independent test sets (N = 60 and N = 40). All patients had received adjuvant Tamoxifen as mono-therapy (median clinical follow-up: 4.6 years) and half had developed distant recurrence (median time-to-recurrence: 3.5 years). MiRNA expression was examined by unsupervised hierarchical clustering and supervised analysis, including clinical parameters as co-variables.
  
  
  RESULTS
  The discovery set identified 10 highly significant miRNAs that discriminated between the patient samples according to outcome. However, the subsequent two independent test sets did not confirm the predictive potential of these miRNAs. A significant correlation was identified between miR-7 and the tumor grade. Investigation of the microRNAs with the most variable expression between patients in different runs yielded a list of 31 microRNAs, eight of which are associated with stem cell characteristics.
  
  
  CONCLUSIONS
  Based on the large sample size, our data strongly suggests that there is no single miRNA profile predictive of outcome following adjuvant Tamoxifen treatment in a broad cohort of ER+ breast cancer patients. We identified a sub-group of Tamoxifen-treated breast cancer patients with miRNA-expressing tumors associated with cancer stem cell characteristics.
authors.affiliation: Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark. mlyng@health.sdu.dk
authors.forename: Maria B
authors.initials: MB
authors.lastname: Lyng
authors.forename: Anne-Vibeke
authors.initials: AV
authors.lastname: Lænkholm
authors.forename: Rolf
authors.initials: R
authors.lastname: Søkilde
authors.forename: Karina H
authors.initials: KH
authors.lastname: Gravgaard
authors.forename: Thomas
authors.initials: T
authors.lastname: Litman
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Ditzel
mesh_terms: D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D016000:Cluster Analysis; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism; D013629:Tamoxifen / Q000378:metabolism / Q000627:therapeutic use*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D035683:MicroRNAs; D011960:Receptors, Estrogen; D013629:Tamoxifen