title: EpCAM-Independent Enrichment of Circulating Tumor Cells in Metastatic Breast Cancer.
abstract: Circulating tumor cells (CTCs) are the potential precursors of metastatic disease. Most assays established for the enumeration of CTCs so far-including the gold standard CellSearch-rely on the expression of the cell surface marker epithelial cell adhesion molecule (EpCAM). But, these approaches may not detect CTCs that express no/low levels of EpCAM, e.g. by undergoing epithelial-to-mesenchymal transition (EMT). Here we present an enrichment strategy combining different antibodies specific for surface proteins and extracellular matrix (ECM) components to capture an EpCAMlow/neg cell line and EpCAMneg CTCs from blood samples of breast cancer patients depleted for EpCAM-positive cells. The expression of respective proteins (Trop2, CD49f, c-Met, CK8, CD44, ADAM8, CD146, TEM8, CD47) was verified by immunofluorescence on EpCAMpos (e.g. MCF7, SKBR3) and EpCAMlow/neg (MDA-MB-231) breast cancer cell lines. To test antibodies and ECM proteins (e.g. hyaluronic acid (HA), collagen I, laminin) for capturing EpCAMneg cells, the capture molecules were first spotted in a single- and multi-array format onto aldehyde-coated glass slides. Tumor cell adhesion of EpCAMpos/neg cell lines was then determined and visualized by Coomassie/MitoTracker staining. In consequence, marginal binding of EpCAMlow/neg MDA-MB-231 cells to EpCAM-antibodies could be observed. However, efficient adhesion/capturing of EpCAMlow/neg cells could be achieved via HA and immobilized antibodies against CD49f and Trop2. Optimal capture conditions were then applied to immunomagnetic beads to detect EpCAMneg CTCs from clinical samples. Captured CTCs were verified/quantified by immunofluorescence staining for anti-pan-Cytokeratin (CK)-FITC/anti-CD45 AF647/DAPI. In total, in 20 out of 29 EpCAM-depleted fractions (69%) from 25 metastatic breast cancer patients additional EpCAMneg CTCs could be identified [range of 1-24 CTCs per sample] applying Trop2, CD49f, c-Met, CK8 and/or HA magnetic enrichment. EpCAMneg dual-positive (CKpos/CD45pos) cells could be traced in 28 out of 29 samples [range 1-480]. By single-cell array-based comparative genomic hybridization we were able to demonstrate the malignant nature of one EpCAMneg subpopulation. In conclusion, we established a novel enhanced CTC enrichment strategy to capture EpCAMneg CTCs from clinical blood samples by targeting various cell surface antigens with antibody mixtures and ECM components.
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Helen
authors.initials: H
authors.lastname: Schneck
authors.affiliation: NMI Natural and Medical Sciences Institute at the University of Tuebingen, Reutlingen, Germany.
authors.forename: Berthold
authors.initials: B
authors.lastname: Gierke
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Frauke
authors.initials: F
authors.lastname: Uppenkamp
authors.affiliation: Department of General, Visceral and Pediatric Surgery, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Bianca
authors.initials: B
authors.lastname: Behrens
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Niederacher
authors.affiliation: Department of General, Visceral and Pediatric Surgery, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Nikolas H
authors.initials: NH
authors.lastname: Stoecklein
authors.affiliation: NMI Natural and Medical Sciences Institute at the University of Tuebingen, Reutlingen, Germany.
authors.forename: Markus F
authors.initials: MF
authors.lastname: Templin
authors.affiliation: NMI Natural and Medical Sciences Institute at the University of Tuebingen, Reutlingen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Pawlak
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Fehm
authors.affiliation: Department of Obstetrics and Gynecology, University Hospital and Medical Faculty of the Heinrich-Heine University Duesseldorf, Duesseldorf, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Neubauer
mesh_terms: D000328:Adult; D000368:Aged; D000911:Antibodies, Monoclonal / Q000378:metabolism*; D000951:Antigens, Neoplasm / Q000097:blood; D000954:Antigens, Surface / Q000097:blood / Q000276:immunology*; D014408:Biomarkers, Tumor / Q000097:blood / Q000276:immunology; D001943:Breast Neoplasms / Q000097:blood* / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D015815:Cell Adhesion Molecules / Q000097:blood; D045744:Cell Line, Tumor; D055028:Comparative Genomic Hybridization; D000071858:Epithelial Cell Adhesion Molecule; D016326:Extracellular Matrix Proteins / Q000097:blood; D005260:Female; D006801:Humans; D061986:MCF-7 Cells; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009360:Neoplastic Cells, Circulating / Q000378:metabolism*; D059010:Single-Cell Analysis
chemical_list: D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D014408:Biomarkers, Tumor; D015815:Cell Adhesion Molecules; C499379:EPCAM protein, human; D000071858:Epithelial Cell Adhesion Molecule; D016326:Extracellular Matrix Proteins