title: mRNA and microRNA expression profiles in circulating tumor cells and primary tumors of metastatic breast cancer patients.
abstract: OBJECTIVE
  Molecular characterization of circulating tumor cells (CTC) holds great promise. Unfortunately, routinely isolated CTC fractions currently still contain contaminating leukocytes, which makes CTC-specific molecular characterization extremely challenging. In this study, we determined mRNA and microRNA (miRNA) expression of potentially CTC-specific genes that are considered to be clinically relevant in breast cancer.
  
  
  METHODS
  CTCs were isolated with the epithelial cell adhesion molecule-based CellSearch Profile Kit. Selected genes were measured by real-time reverse transcriptase PCR in CTCs of 50 metastatic breast cancer patients collected before starting first-line systemic therapy in blood from 53 healthy blood donors (HBD) and in primary tumors of 8 of the patients. The molecular profiles were associated with CTC counts and clinical parameters and compared with the profiles generated from the corresponding primary tumors.
  
  
  RESULTS
  We identified 55 mRNAs and 10 miRNAs more abundantly expressed in samples from 32 patients with at least 5 CTCs in 7.5 mL of blood compared with samples from 9 patients without detectable CTCs and HBDs. Clustering analysis resulted in 4 different patient clusters characterized by 5 distinct gene clusters. Twice the number of patients from cluster 2 to 4 had developed both visceral and nonvisceral metastases. Comparing transcript levels in CTCs with those measured in corresponding primary tumors showed clinically relevant discrepancies in estrogen receptor and HER2 levels.
  
  
  CONCLUSIONS
  Our study shows that molecular profiling of low numbers of CTCs in a high background of leukocytes is feasible and shows promise for further studies on the clinical relevance of molecular characterization of CTCs.
authors.affiliation: Department of Medical Oncology, Josephine Nefkens Institute and Cancer Genomics Centre, Rotterdam, The Netherlands.
authors.forename: Anieta M
authors.initials: AM
authors.lastname: Sieuwerts
authors.forename: Bianca
authors.initials: B
authors.lastname: Mostert
authors.forename: Joan
authors.initials: J
authors.lastname: Bolt-de Vries
authors.forename: Dieter
authors.initials: D
authors.lastname: Peeters
authors.forename: Felix E
authors.initials: FE
authors.lastname: de Jongh
authors.forename: Jacqueline M L
authors.initials: JM
authors.lastname: Stouthard
authors.forename: Luc Y
authors.initials: LY
authors.lastname: Dirix
authors.forename: Peter A
authors.initials: PA
authors.lastname: van Dam
authors.forename: Anne
authors.initials: A
authors.lastname: Van Galen
authors.forename: Vanja
authors.initials: V
authors.lastname: de Weerd
authors.forename: Jaco
authors.initials: J
authors.lastname: Kraan
authors.forename: Petra
authors.initials: P
authors.lastname: van der Spoel
authors.forename: Raquel
authors.initials: R
authors.lastname: Ramírez-Moreno
authors.forename: Carolien H M
authors.initials: CH
authors.lastname: van Deurzen
authors.forename: Marcel
authors.initials: M
authors.lastname: Smid
authors.forename: Jack X
authors.initials: JX
authors.lastname: Yu
authors.forename: John
authors.initials: J
authors.lastname: Jiang
authors.forename: Yixin
authors.initials: Y
authors.lastname: Wang
authors.forename: Jan W
authors.initials: JW
authors.lastname: Gratama
authors.forename: Stefan
authors.initials: S
authors.lastname: Sleijfer
authors.forename: John A
authors.initials: JA
authors.lastname: Foekens
authors.forename: John W M
authors.initials: JW
authors.lastname: Martens
mesh_terms: D014408:Biomarkers, Tumor / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D015815:Cell Adhesion Molecules / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D007962:Leukocytes; D035683:MicroRNAs / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D009362:Neoplasm Metastasis; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; D035683:MicroRNAs; D012333:RNA, Messenger