title: Analysis of circulating tumor cells in patients with non-small cell lung cancer using epithelial marker-dependent and -independent approaches.
abstract: BACKGROUND
  Epithelial circulating tumor cells (CTCs) are detectable in patients with non-small cell lung cancer (NSCLC). However, epithelial to mesenchymal transition, a widely reported prerequisite for metastasis, may lead to an underestimation of CTC number. We compared directly an epithelial marker-dependent (CellSearch) and a marker-independent (isolation by size of epithelial tumor cells [ISET]) technology platform for the ability to identify CTCs. Molecular characteristics of CTCs were also explored.
  
  
  METHODS
  Paired peripheral blood samples were collected from 40 chemonäive, stages IIIA to IV NSCLC patients. CTCs were enumerated by Epithelial Cell Adhesion Molecule-based immunomagnetic capture (CellSearch, Veridex) and by filtration (ISET, RareCell Diagnostics). CTCs isolated by filtration were assessed by immunohistochemistry for epithelial marker expression (cytokeratins, Epithelial Cell Adhesion Molecule, epidermal growth factor receptor) and for proliferation status (Ki67).
  
  
  RESULTS
  CTCs were detected using ISET in 32 of 40 (80%) patients compared with 9 of 40 (23%) patients using CellSearch. A subpopulation of CTCs isolated by ISET did not express epithelial markers. Circulating tumor microemboli (CTM, clusters of ≥ 3 CTCs) were observed in 43% patients using ISET but were undetectable by CellSearch. Up to 62% of single CTCs were positive for the proliferation marker Ki67, whereas cells within CTM were nonproliferative.
  
  
  CONCLUSIONS
  Both technology platforms detected NSCLC CTCs. ISET detected higher numbers of CTCs including epithelial marker negative tumor cells. ISET also isolated CTM and permitted molecular characterization. Combined with our previous CellSearch data confirming CTC number as an independent prognostic biomarker for NSCLC, we propose that this complementary dual technology approach to CTC analysis allows more complete exploration of CTCs in patients with NSCLC.
authors.affiliation: Clinical and Experimental Pharmacology Group, Paterson Institute for Cancer Research, University of Manchester, United Kingdom.
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Krebs
authors.forename: Jian-Mei
authors.initials: JM
authors.lastname: Hou
authors.forename: Robert
authors.initials: R
authors.lastname: Sloane
authors.forename: Lee
authors.initials: L
authors.lastname: Lancashire
authors.forename: Lynsey
authors.initials: L
authors.lastname: Priest
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nonaka
authors.forename: Tim H
authors.initials: TH
authors.lastname: Ward
authors.forename: Alison
authors.initials: A
authors.lastname: Backen
authors.forename: Glen
authors.initials: G
authors.lastname: Clack
authors.forename: Andrew
authors.initials: A
authors.lastname: Hughes
authors.forename: Malcolm
authors.initials: M
authors.lastname: Ranson
authors.forename: Fiona H
authors.initials: FH
authors.lastname: Blackhall
authors.forename: Caroline
authors.initials: C
authors.lastname: Dive
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000378:metabolism / Q000473:pathology*; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000378:metabolism / Q000473:pathology*; D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation; D002469:Cell Separation; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009360:Neoplastic Cells, Circulating / Q000378:metabolism / Q000473:pathology*; D011379:Prognosis; D011446:Prospective Studies
chemical_list: D014408:Biomarkers, Tumor