title: Radiation-Induced Dedifferentiation of Head and Neck Cancer Cells Into Cancer Stem Cells Depends on Human Papillomavirus Status.
abstract: OBJECTIVE
  To test the hypothesis that the radiation response of cancer stem cells (CSCs) in human papillomavirus (HPV)-positive and HPV-negative head and neck squamous cell carcinoma (HNSCC) differs and is not reflected in the radiation response of the bulk tumor populations, that radiation therapy (RT) can dedifferentiate non-stem HNSCC cells into CSCs, and that radiation-induced dedifferentiation depends on the HPV status.
  
  
  METHODS
  Records of a cohort of 162 HNSCC patients were reviewed, and their outcomes were correlated with their HPV status. Using a panel of HPV-positive and HPV-negative HNSCC cell lines expressing a reporter for CSCs, we characterized HPV-positive and HPV-negative lines via flow cytometry, sphere-forming capacity assays in vitro, and limiting dilution assays in vivo. Non-CSCs were treated with different doses of radiation, and the dedifferentiation of non-CSCs into CSCs was investigated via flow cytometry and quantitative reverse transcription-polymerase chain reaction for re-expression of reprogramming factors.
  
  
  RESULTS
  Patients with HPV-positive tumors have superior overall survival and local-regional control. Human papillomavirus-positive HNSCC cell lines have lower numbers of CSCs, which inversely correlates with radiosensitivity. Human papillomavirus-negative HNSCC cell lines lack hierarchy owing to enhanced spontaneous dedifferentiation. Non-CSCs from HPV-negative lines show enhanced radiation-induced dedifferentiation compared with HPV-positive lines, and RT induced re-expression of Yamanaka reprogramming factors.
  
  
  CONCLUSIONS
  Supporting the favorable prognosis of HPV-positive HNSCCs, we show that (1) HPV-positive HNSCCs have a lower frequency of CSCs; (2) RT can dedifferentiate HNSCC cells into CSCs; and (3) radiation-induced dedifferentiation depends on the HPV status of the tumor.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California; Jonsson Comprehensive Cancer Center at UCLA, Los Angeles, California. Electronic address: evlashi@mednet.ucla.edu.
authors.forename: Erina
authors.initials: E
authors.lastname: Vlashi
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Allen M
authors.initials: AM
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Boyrie
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Garrett
authors.initials: G
authors.lastname: Yu
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Andrea
authors.initials: A
authors.lastname: Nguyen
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Brower
authors.affiliation: Department of Radiation Oncology, University of California Davis, Sacramento, California.
authors.forename: Clayton B
authors.initials: CB
authors.lastname: Hess
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine at UCLA, Los Angeles, California; Jonsson Comprehensive Cancer Center at UCLA, Los Angeles, California.
authors.forename: Frank
authors.initials: F
authors.lastname: Pajonk
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000821:virology; D054337:Cell Dedifferentiation / Q000502:physiology / Q000528:radiation effects*; D045744:Cell Line, Tumor; D065150:Cellular Reprogramming; D005434:Flow Cytometry; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy / Q000821:virology; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D016688:Mice, Inbred NOD; D009364:Neoplasm Recurrence, Local / Q000821:virology; D014411:Neoplastic Stem Cells / Q000166:cytology / Q000528:radiation effects / Q000821:virology; D050814:Octamer Transcription Factor-3 / Q000378:metabolism; D027383:Papillomaviridae; D011379:Prognosis; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D011829:Radiation Dosage; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D000077195:Squamous Cell Carcinoma of Head and Neck
chemical_list: D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; C489427:MYC protein, human; D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D016271:Proto-Oncogene Proteins c-myc; C527782:SOX2 protein, human; D055748:SOXB1 Transcription Factors