title: Targeting cancer stem cell plasticity through modulation of epidermal growth factor and insulin-like growth factor receptor signaling in head and neck squamous cell cancer.
abstract: Emerging data suggest that cancer stem cells (CSCs) exist in equilibrium with differentiated cells and that stochastic transitions between these states can account for tumor heterogeneity and drug resistance. The aim of this study was to establish an in vitro system that recapitulates stem cell plasticity in head and neck squamous cell cancers (HNSCCs) and identify the factors that play a role in the maintenance and repopulation of CSCs. Tumor spheres were established using patient-derived cell lines via anchorage-independent cell culture techniques. These tumor spheres were found to have higher aldehyde dehydrogenase (ALD) cell fractions and increased expression of Kruppel-like factor 4, SRY (sex determining region Y)-box 2, and Nanog and were resistant to γ-radiation, 5-fluorouracil, cisplatin, and etoposide treatment compared with monolayer culture cells. Monolayer cultures were subject to single cell cloning to generate clones with high and low ALD fractions. ALDHigh clones showed higher expression of stem cell and epithelial-mesenchymal transition markers compared with ALDLow clones. ALD fractions, representing stem cell fractions, fluctuated with serial passaging, equilibrating at a level specific to each cell line, and could be augmented by the addition of epidermal growth factor (EGF) and/or insulin. ALDHigh clones showed increased EGF receptor (EGFR) and insulin-like growth factor-1 receptor (IGF-1R) phosphorylation, with increased activation of downstream pathways compared with ALDLow clones. Importantly, blocking these pathways using specific inhibitors against EGFR and IGF-1R reduced stem cell fractions drastically. Taken together, these results show that HNSCC CSCs exhibit plasticity, with the maintenance of the stem cell fraction dependent on the EGFR and IGF-1R pathways and potentially amenable to targeted therapeutics.
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Hui Sun
authors.initials: HS
authors.lastname: Leong
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Fui Teen
authors.initials: FT
authors.lastname: Chong
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Pui Hoon
authors.initials: PH
authors.lastname: Sew
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Dawn P
authors.initials: DP
authors.lastname: Lau
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Bernice H
authors.initials: BH
authors.lastname: Wong
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore.
authors.forename: Bin-Tean
authors.initials: BT
authors.lastname: Teh
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore gopaliyer@yahoo.com Daniel.tan.s.w@nccs.com.sg.
authors.forename: Daniel S W
authors.initials: DS
authors.lastname: Tan
authors.affiliation: Cancer Therapeutics Research Laboratory, Laboratory of Cancer Epigenome, Department of Medical Oncology, and Department of Surgical Oncology, National Cancer Centre Singapore, Singapore gopaliyer@yahoo.com Daniel.tan.s.w@nccs.com.sg.
authors.forename: N Gopalakrishna
authors.initials: NG
authors.lastname: Iyer
mesh_terms: D000328:Adult; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006258:Head and Neck Neoplasms / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D000090062:Kruppel-Like Factor 4; D008297:Male; D008875:Middle Aged; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D000077195:Squamous Cell Carcinoma of Head and Neck
chemical_list: C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; C512478:EGFR protein, human; D066246:ErbB Receptors; D017526:Receptor, IGF Type 1
keywords: Aldehyde dehydrogenase; Cancer stem cell; Epidermal growth factor receptor; Head and neck squamous cell cancer; Insulin-like growth factor-1 receptor