title: Direct Comparison of Metastasis-Related miRNAs Expression Levels in Circulating Tumor Cells, Corresponding Plasma, and Primary Tumors of Breast Cancer Patients.
abstract: BACKGROUND
  Circulating tumor cells (CTCs) and microRNAs (miRNAs) are important in liquid biopsies in which peripheral blood is used to characterize the evolution of solid tumors. We evaluated the expression levels of miR-21, miR-146a, miR-200c, and miR-210 in CTCs of breast cancer patients with verified metastasis and compared their expression levels in corresponding plasma and primary tumors.
  
  
  METHODS
  Expression levels of the miRNAs were quantified by quantitative reverse transcription PCR (RT-qPCR) in (a) 89 primary breast tumors and 30 noncancerous breast tissues and (b) CTCs and corresponding plasma of 55 patients with metastatic breast cancer and 20 healthy donors. For 30 of these patients, CTCs, corresponding plasma, and primary tumor tissues were available.
  
  
  RESULTS
  In formalin-fixed, paraffin-embedded tissues, these miRNAs were differentially expressed between primary breast tumors and noncancerous breast tissues. miR-21 (P < 0.001) and miR-146a (P = 0.001) were overexpressed, whereas miR-200c (P = 0.004) and miR-210 (P = 0.002) were underexpressed. In multivariate analysis, miR-146a overexpression was significantly [hazard ratio 2.969 (1.231-7.157), P = 0.015] associated with progression-free survival. In peripheral blood, all miRNAs studied were overexpressed in both CTC and corresponding plasma. There was a significant association between miR-21 expression levels in CTCs and plasma for 36 of 55 samples (P = 0.008). In plasma, ROC curve analysis revealed that miR-21, miR-146a, and miR-210 could discriminate patients from healthy individuals.
  
  
  CONCLUSIONS
  Metastasis-related miRNAs are overexpressed in CTCs and corresponding plasma; miR-21 expression levels highly correlate in CTCs and plasma; and miR-21, miR-146a, and miR-210 are valuable plasma biomarkers for discriminating patients from healthy individuals.
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece; athina_markoy@yahoo.gr.
authors.forename: Athina
authors.initials: A
authors.lastname: Markou
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece;
authors.forename: Martha
authors.initials: M
authors.lastname: Zavridou
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece;
authors.forename: Ioanna
authors.initials: I
authors.lastname: Sourvinou
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada;
authors.forename: George
authors.initials: G
authors.lastname: Yousef
authors.affiliation: Oncology Unit and Pathology Department, Helena Venizelou Hospital, Athens, Greece;
authors.forename: Sofia
authors.initials: S
authors.lastname: Kounelis
authors.affiliation: Oncology Unit and Pathology Department, Helena Venizelou Hospital, Athens, Greece;
authors.forename: Nikos
authors.initials: N
authors.lastname: Malamos
authors.affiliation: Department of Medical Oncology, University General Hospital of Heraklion, Heraklion, Greece.
authors.forename: Vasilis
authors.initials: V
authors.lastname: Georgoulias
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemistry, University of Athens, Athens, Greece;
authors.forename: Evi
authors.initials: E
authors.lastname: Lianidou
mesh_terms: D001943:Breast Neoplasms / Q000097:blood* / Q000235:genetics* / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D035683:MicroRNAs / Q000097:blood* / Q000235:genetics*; D009360:Neoplastic Cells, Circulating / Q000378:metabolism* / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D035683:MicroRNAs