title: Electronic cigarettes induce DNA strand breaks and cell death independently of nicotine in cell lines.
abstract: OBJECTIVE
  Evaluate the cytotoxicity and genotoxicity of short- and long-term e-cigarette vapor exposure on a panel of normal epithelial and head and neck squamous cell carcinoma (HNSCC) cell lines.
  
  
  METHODS
  HaCaT, UMSCC10B, and HN30 were treated with nicotine-containing and nicotine-free vapor extract from two popular e-cigarette brands for periods ranging from 48 h to 8 weeks. Cytotoxicity was assessed using Annexin V flow cytometric analysis, trypan blue exclusion, and clonogenic assays. Genotoxicity in the form of DNA strand breaks was quantified using the neutral comet assay and γ-H2AX immunostaining.
  
  
  RESULTS
  E-cigarette-exposed cells showed significantly reduced cell viability and clonogenic survival, along with increased rates of apoptosis and necrosis, regardless of e-cigarette vapor nicotine content. They also exhibited significantly increased comet tail length and accumulation of γ-H2AX foci, demonstrating increased DNA strand breaks.
  
  
  CONCLUSIONS
  E-cigarette vapor, both with and without nicotine, is cytotoxic to epithelial cell lines and is a DNA strand break-inducing agent. Further assessment of the potential carcinogenic effects of e-cigarette vapor is urgently needed.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Vicky
authors.initials: V
authors.lastname: Yu
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Mehran
authors.initials: M
authors.lastname: Rahimy
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Avinaash
authors.initials: A
authors.lastname: Korrapati
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Yinan
authors.initials: Y
authors.lastname: Xuan
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Angela E
authors.initials: AE
authors.lastname: Zou
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Aswini R
authors.initials: AR
authors.lastname: Krishnan
authors.affiliation: Division of Pulmonary and Critical Care, University of California, San Diego, La Jolla, California, United States.
authors.forename: Tzuhan
authors.initials: T
authors.lastname: Tsui
authors.affiliation: Department of Radiation Medicine and Applied Sciences, Moores Cancer Center, University of California, San Diego, La Jolla, California, United States.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Aguilera
authors.affiliation: Department of Radiation Medicine and Applied Sciences, Moores Cancer Center, University of California, San Diego, La Jolla, California, United States.
authors.forename: Sunil
authors.initials: S
authors.lastname: Advani
authors.affiliation: Division of Pulmonary and Critical Care, University of California, San Diego, La Jolla, California, United States; Pulmonary and Critical Care Section, VA San Diego Healthcare System, La Jolla, California, United States.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Crotty Alexander
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Kevin T
authors.initials: KT
authors.lastname: Brumund
authors.affiliation: Department of Pathology, VA San Diego Healthcare System, La Jolla, California, United States.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wang-Rodriguez
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, University of California, San Diego, La Jolla, California, United States.
authors.forename: Weg M
authors.initials: WM
authors.lastname: Ongkeko
mesh_terms: D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor / Q000187:drug effects*; D004249:DNA Damage / Q000187:drug effects*; D066300:Electronic Nicotine Delivery Systems / Q000009:adverse effects*; D004847:Epithelial Cells / Q000187:drug effects*; D006258:Head and Neck Neoplasms / Q000378:metabolism; D006801:Humans; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D014835:Volatilization
chemical_list: D018722:Nicotinic Agonists; D009538:Nicotine
keywords: DNA damage; Electronic cigarettes; Head and neck squamous cell carcinoma (HNSCC); Nicotine; Oral cancer; Smoking; Strand breaks