title: [Cells of the tumor front : a potential therapeutic target in head and neck cancer therapy?].
abstract: BACKGROUND
  With a frequency of about 90 %, head and neck squamous cell carcinomas (HNSCCs) are the most common malignancies of the upper aerodigestive tract. The cancer stem cell (CSC) hypothesis postulates that CSCs are the dangerous part of the tumor and are relevant to metastasis, invasiveness and resistance to chemotherapy.
  
  
  METHODS
  Tissue samples taken from HNSCCs and normal mucosa were tested for the expression of several established CSC markers. The expression and activity of the matrix metalloproteinase MMP-9 was also investigated.
  
  
  RESULTS
  Cells of the invasive tumor front expressed the basal stem cell markers CD44, ALDH1 and CK14. However, in contrast to the noninvasive basal cell layer of normal mucosa, HNSCC samples were also positive for active MMP-9, which lends the tumor its gelatinolytic activity.
  
  
  CONCLUSIONS
  These observations suggest a model in which cells of the invasive front are derived from the basal cell layer of normal mucosa and harbour the CSCs. Future studies should thus focus on the cells of the invasive front in particular, since the activity of these cells may form the basis for tumor recurrence and therapy resistance.
authors.affiliation: Klinik für Hals-, Nasen- und Ohrenheilkunde, Universitätsklinikum Gießen und Marburg GmbH, Standort Marburg, Baldingerstr., 35033, Marburg, Deutschland, carolina.sterz@uk-koeln.de.
authors.forename: C
authors.initials: C
authors.lastname: Sterz
authors.forename: R
authors.initials: R
authors.lastname: Mandic
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology*; D006258:Head and Neck Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology*; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D000077195:Squamous Cell Carcinoma of Head and Neck; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D020780:Matrix Metalloproteinase 9