title: Pre-clinical validation of early molecular markers of sensitivity to aromatase inhibitors in a mouse model of post-menopausal hormone-sensitive breast cancer.
abstract: BACKGROUND
  Changes in breast cancer cell biology following hormonal treatment have been claimed as promising predictor markers of clinical benefit even outperforming clinical response. From previous work we selected 10 genes showing both a well known regulation by oestrogen and a high level of early transcriptional regulation following therapy with aromatase inhibitors. Here we use an animal breast cancer model to explore the feasibility of the determination of their expression in minimally invasive samples and to further assess the magnitude of their regulation by letrozole. ANIMAL AND METHODS: Aromatase inhibitor sensitive breast cancer tumours were grown in athymic mice under supplement with androstenedione. Following initial tumour growth animals were assigned to a control group or to receive letrozole at two different dosages. Fine needle aspirates were obtained at the moment of treatment assignation and one week later. Expression of the following genes at both time points was determined: Ki-67, Cyclin D1, pS2, Trefoil Factor 3, PDZ domain containing 1, Ubiquitin-conjugating enzyme E2C, Stanniocalcin 2, Topoisomerase 2 alfa, MAN1A1 and FAS.
  
  
  RESULTS
  Fine needles aspirates were found to be a feasible and reproducible technique for RNA extraction. Trefoil Factor 3, pS2, Cyclin D1 and Stanniocalcin 2 were significantly downregulated by letrozole. Among them pS2 appears to be most sensitive to aromatase inhibitor treatment even differentiating sub-optimal from optimal letrozole dosage.
  
  
  CONCLUSIONS
  We present pre-clinical evidence to justify the exploration in clinical trials of pS2, Trefoil factor 3, Cyclin D1 and Stanniocalcin as dynamic markers of oestrogen-driven pathway activation.
authors.affiliation: Translational Research Laboratory, Institut Català d'Oncologia, IDIBELL, Gran via s/n, km 2.7, L'Hospitalet de Llobregat, Barcelona, 08907, Spain. anderu@iconcologia.net
authors.forename: Ander
authors.initials: A
authors.lastname: Urruticoechea
authors.forename: Helena
authors.initials: H
authors.lastname: Aguilar
authors.forename: Xavier
authors.initials: X
authors.lastname: Solé
authors.forename: Gabriel
authors.initials: G
authors.lastname: Capellà
authors.forename: Lesley-Ann
authors.initials: LA
authors.lastname: Martin
authors.forename: Mitch
authors.initials: M
authors.lastname: Dowsett
authors.forename: Josep Ramon
authors.initials: JR
authors.lastname: Germà-Lluch
mesh_terms: D000818:Animals; D047072:Aromatase Inhibitors / Q000494:pharmacology*; D014408:Biomarkers, Tumor / Q000032:analysis; D001707:Biopsy, Needle; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D056741:Cyclin D; D016213:Cyclins / Q000032:analysis; D004195:Disease Models, Animal; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D019394:Ki-67 Antigen / Q000032:analysis; D000077289:Letrozole; D051379:Mice; D009570:Nitriles / Q000494:pharmacology*; D010455:Peptides / Q000032:analysis; D017698:Postmenopause; D011960:Receptors, Estrogen / Q000032:analysis; D000071163:Trefoil Factor-1; D014230:Triazoles / Q000494:pharmacology*
chemical_list: D047072:Aromatase Inhibitors; D014408:Biomarkers, Tumor; D056741:Cyclin D; D016213:Cyclins; D019394:Ki-67 Antigen; D009570:Nitriles; D010455:Peptides; D011960:Receptors, Estrogen; C472724:Tff1 protein, mouse; D000071163:Trefoil Factor-1; D014230:Triazoles; D000077289:Letrozole