title: CD66c is a novel marker for colorectal cancer stem cell isolation, and its silencing halts tumor growth in vivo.
abstract: BACKGROUND
  Despite the well recognized expression of the cell surface markers cluster of differentiation 44 (homing cell adhesion molecule) and CD133 (Prominin 1) on human colorectal cancer stem cells (CCSCs), these molecules do not appear to be effective targets for stem cell-directed therapies. Because the surface marker CD66c (also known as carcinoembryonic antigen-related cell adhesion molecule 6) has demonstrated promise as a therapeutic target in pancreatic malignancy, the authors evaluated its potential as a target for stem cell-directed treatment of colorectal cancer.
  
  
  METHODS
  First, the authors characterized CD66c expression by flow cytometry and immunohistochemistry in colon cancer samples and in normal colon tissues. Then, the coexpression of CD66c and CD133 was evaluated on putative CCSCs. CD66c expression also was measured in stem cell-enriched colon spheres. Finally, the effects of small-interfering RNA-mediated CD66c silencing on the in vitro and in vivo growth of Caco2 colon cancer cells were evaluated.
  
  
  RESULTS
  CD66c expression was significantly higher in colon cancers than in contiguous normal colon tissues and paralleled cancer stage. CD66c was absent in CD133-positive cells that were isolated from normal colon, whereas its expression was brightest (CD66c(bright) ) in CD133-positive cells from colon cancer samples. In vitro experiments demonstrated that colon spheres were considerably enriched in a CD66c(bright) population in a fashion comparable to the enrichment observed in fresh liver metastases. In vitro proliferation and clonogenic potential were hampered when CD66c was silenced in Caco2 cells. Finally, in vivo xenograft experiments demonstrated that CD66c silencing almost completely abrogated the tumorigenic potential of Caco2 cells.
  
  
  CONCLUSIONS
  CD66c(bright) expression was associated with colon cancer stem cells and CD66c silencing blocked tumor growth, thereby opening the way to a potential new treatment for colon cancer.
authors.affiliation: CEINGE-Advanced Biotechnology, Naples, Italy.
authors.forename: Marica
authors.initials: M
authors.lastname: Gemei
authors.forename: Peppino
authors.initials: P
authors.lastname: Mirabelli
authors.forename: Rosa
authors.initials: R
authors.lastname: Di Noto
authors.forename: Claudia
authors.initials: C
authors.lastname: Corbo
authors.forename: Antonino
authors.initials: A
authors.lastname: Iaccarino
authors.forename: Anna
authors.initials: A
authors.lastname: Zamboli
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Troncone
authors.forename: Gennaro
authors.initials: G
authors.lastname: Galizia
authors.forename: Eva
authors.initials: E
authors.lastname: Lieto
authors.forename: Luigi
authors.initials: L
authors.lastname: Del Vecchio
authors.forename: Francesco
authors.initials: F
authors.lastname: Salvatore
mesh_terms: D000071916:AC133 Antigen; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism; D018938:Caco-2 Cells; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002469:Cell Separation / Q000379:methods; D003106:Colon / Q000378:metabolism; D015179:Colorectal Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D005260:Female; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism; D020868:Gene Silencing; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D014411:Neoplastic Stem Cells / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D012016:Reference Values; D023041:Xenograft Model Antitumor Assays
chemical_list: D000071916:AC133 Antigen; D015703:Antigens, CD; D014408:Biomarkers, Tumor; C504117:CEACAM6 protein, human; D015815:Cell Adhesion Molecules; D058851:GPI-Linked Proteins; D006023:Glycoproteins; C000606023:PROM1 protein, human; D010455:Peptides; C000606024:Prom1 protein, mouse