title: Elevation in 5-FU-induced apoptosis in head and neck cancer stem cells by a combination of CDHP and GSK3β inhibitors.
abstract: BACKGROUND
  Cancer stem cells (CSCs) are involved in both tumourigenesis and in tumour recurrence after therapy. In head and neck squamous cell carcinoma (HNSCC), there are two biologically different CSC phenotypes both of which express high levels of CD44 but differ in their expression levels of epithelial-specific antigen (ESA). One phenotype is CD44(high)/ESA(high) and has epithelial features (Epi-CSCs), while the other is CD44(high) /ESA(low), has undergone epithelial to mesenchymal transition (EMT-CSCs), has mesenchymal features and is migratory (Biddle et al., 2011). CSCs are resistant to therapeutically induced apoptosis but the molecular mechanisms by which they develop apoptotic resistance remains unclear. However, glycogen synthase kinase 3β (GSK3β) contributes to regulation of both the self-renewal and switching of these two CSC phenotypes (Shigeishi et al., 2013).
  
  
  METHODS
  CD44(high) /ESA(low), CD44(high) /ESA(high) and CD44(low) cells were FACS sorted from the HNSCC cell line LUC4, and 5-FU-induced apoptosis was analysed by Annexin V staining followed by flow cytometry analysis.
  
  
  RESULTS
  CD44(high) /ESA(low) cells exhibited marked resistance to 5-FU-induced apoptosis and had high expression of dihydropyrimidine dehydrogenase (DPD). The DPD inhibitor, 5-chloro-2, 4-dihydroxypyridine (CDHP) significantly enhanced 5-FU-induced apoptosis of CD44(high)/ESA(low) cells. Inhibition of GSK3β induced CD44(high) /ESA(low) cells to undergo mesenchymal-to-epithelial transition (MET) to CD44(high)/ESA(high) cells and pre-existing CD44(high) /ESA(high) cells to differentiate. Apoptosis induced by 5-FU was thus facilitated. Combination of both CDHP and GSK3β inhibitors markedly enhanced 5-FU-induced apoptosis of CD44(high) /ESA(low) cells.
  
  
  CONCLUSIONS
  Our results suggest potentially new approaches for the elimination of the therapy resistant HNSCC CSC population.
authors.affiliation: Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK; Department of Oral and Maxillofacial Surgery, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Shigeishi
authors.forename: Adrian
authors.initials: A
authors.lastname: Biddle
authors.forename: Luke
authors.initials: L
authors.lastname: Gammon
authors.forename: Camila O
authors.initials: CO
authors.lastname: Rodini
authors.forename: Miho
authors.initials: M
authors.lastname: Yamasaki
authors.forename: Sayaka
authors.initials: S
authors.lastname: Seino
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugiyama
authors.forename: Masaaki
authors.initials: M
authors.lastname: Takechi
authors.forename: Ian C
authors.initials: IC
authors.lastname: Mackenzie
mesh_terms: D000951:Antigens, Neoplasm / Q000032:analysis; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D014408:Biomarkers, Tumor / Q000032:analysis; D017252:CD3 Complex / Q000032:analysis; D015815:Cell Adhesion Molecules / Q000032:analysis; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002469:Cell Separation / Q000379:methods; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000032:analysis / Q000037:antagonists & inhibitors; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D000071858:Epithelial Cell Adhesion Molecule; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects; D004848:Epithelium / Q000473:pathology; D005434:Flow Cytometry / Q000379:methods; D005472:Fluorouracil / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors*; D000071679:Glycogen Synthase Kinase 3 beta; D006258:Head and Neck Neoplasms / Q000473:pathology*; D006801:Humans; D018960:Hyaluronan Receptors / Q000032:analysis; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000473:pathology; D011725:Pyridines / Q000494:pharmacology*
chemical_list: C417063:5-chlorodihydroxypyridine; D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; D014408:Biomarkers, Tumor; D017252:CD3 Complex; C497483:CD44 protein, human; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D018960:Hyaluronan Receptors; D011725:Pyridines; D042943:Dihydrouracil Dehydrogenase (NADP); C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; D038362:Glycogen Synthase Kinase 3; D005472:Fluorouracil
keywords: 5-FU; GSK3β; cancer stem cell; head and neck squamous cell carcinoma