title: Dynamic changes in gene expression in vivo predict prognosis of tamoxifen-treated patients with breast cancer.
abstract: BACKGROUND
  Tamoxifen is the most widely prescribed anti-estrogen treatment for patients with estrogen receptor (ER)-positive breast cancer. However, there is still a need for biomarkers that reliably predict endocrine sensitivity in breast cancers and these may well be expressed in a dynamic manner.
  
  
  METHODS
  In this study we assessed gene expression changes at multiple time points (days 1, 2, 4, 7, 14) after tamoxifen treatment in the ER-positive ZR-75-1 xenograft model that displays significant changes in apoptosis, proliferation and angiogenesis within 2 days of therapy.
  
  
  RESULTS
  Hierarchical clustering identified six time-related gene expression patterns, which separated into three groups: two with early/transient responses, two with continuous/late responses and two with variable response patterns. The early/transient response represented reductions in many genes that are involved in cell cycle and proliferation (e.g. BUB1B, CCNA2, CDKN3, MKI67, UBE2C), whereas the continuous/late changed genes represented the more classical estrogen response genes (e.g. TFF1, TFF3, IGFBP5). Genes and the proteins they encode were confirmed to have similar temporal patterns of expression in vitro and in vivo and correlated with reduction in tumour volume in primary breast cancer. The profiles of genes that were most differentially expressed on days 2, 4 and 7 following treatment were able to predict prognosis, whereas those most changed on days 1 and 14 were not, in four tamoxifen treated datasets representing a total of 404 patients.
  
  
  CONCLUSIONS
  Both early/transient/proliferation response genes and continuous/late/estrogen-response genes are able to predict prognosis of primary breast tumours in a dynamic manner. Temporal expression of therapy-response genes is clearly an important factor in characterising the response to endocrine therapy in breast tumours which has significant implications for the timing of biopsies in neoadjuvant biomarker studies.
authors.affiliation: CRUK Cancer Research Centre and Academic Breast Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, Edinburgh, UK. Karen.Taylor1@ed.ac.uk
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Taylor
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Sims
authors.forename: Liang
authors.initials: L
authors.lastname: Liang
authors.forename: Dana
authors.initials: D
authors.lastname: Faratian
authors.forename: Morwenna
authors.initials: M
authors.lastname: Muir
authors.forename: Graeme
authors.initials: G
authors.lastname: Walker
authors.forename: Barbara
authors.initials: B
authors.lastname: Kuske
authors.forename: J Michael
authors.initials: JM
authors.lastname: Dixon
authors.forename: David A
authors.initials: DA
authors.lastname: Cameron
authors.forename: David J
authors.initials: DJ
authors.lastname: Harrison
authors.forename: Simon P
authors.initials: SP
authors.lastname: Langdon
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols; D014408:Biomarkers, Tumor / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D004958:Estradiol / Q000494:pharmacology; D004965:Estrogen Antagonists / Q000494:pharmacology*; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D020411:Oligonucleotide Array Sequence Analysis; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics; D011960:Receptors, Estrogen / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013629:Tamoxifen / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays
chemical_list: D014408:Biomarkers, Tumor; D004965:Estrogen Antagonists; D004967:Estrogens; D012333:RNA, Messenger; D011960:Receptors, Estrogen; D013629:Tamoxifen; D004958:Estradiol