title: Ultrasound hyperthermia induces apoptosis in head and neck squamous cell carcinoma: An in vitro study.
abstract: BACKGROUND
  Hyperthermia is considered an efficient complement in the treatment of head and neck squamous cell carcinoma (HNSCC). Hyperthermia induces cell apoptosis in a temperature- and time-dependent manner. However, the molecular mechanism of hyperthermia remains unclear. The aim of this study was to investigate the mechanism of apoptosis induced by ultrasound hyperthermia in HNSCC cell lines HN-30 and HN-13.
  
  
  METHODS
  We examined the dynamic changes of early apoptosis and secondary necrosis in HN-30 and HN-13 cells treated by hyperthermia at 42°C for 10 min. We further examined mitochondrial membrane potential in vitro by ultrasound hyperthermia for different heating temperatures (38-44°C, 10 min) and heating times (42°C, 10-50 min). After heating by ultrasound at 42°C for 10 min, the apoptosis index achieved its highest level at 8 h after treatment, decreased rapidly and remained constant at a reduced level at 12 h.
  
  
  RESULTS
  The level of secondary necrosis increased with the level of early apoptosis but remained at a higher level until 14 h. The level of secondary necrosis correlated with the level of early apoptosis (HN-13: r=0.7523, P=0.0030; HN-30: r=0.6510, P=0.016). The fractions of cells with low mitochondrial membrane potential (Δψ) in the heating-temperature grads group and heating-time grads group decreased significantly over time. Therefore, HN-30 and HN-13 cells developed apoptosis after ultrasound hyperthermia treatment with decreases in the mitochondrial transmembrane potential level.
  
  
  CONCLUSIONS
  Ultrasound hyperthermia induces apoptosis in HN-30 and HN-13 cells, possibly via the mitochondrial caspase pathway.
authors.affiliation: Department of Oral Maxillofacial-Head Neck Oncology, Shanghai 9th People's Hospital, No 639, Zhi Zao Ju Road, Shanghai 200011 PR China, huyayi@shsmu.edu.cn.
authors.forename: G
authors.initials: G
authors.lastname: Ren
authors.forename: H
authors.initials: H
authors.lastname: Jv
authors.forename: Z
authors.initials: Z
authors.lastname: Tian
authors.forename: S-R
authors.initials: SR
authors.lastname: Gvetadze
authors.forename: J
authors.initials: J
authors.lastname: Hu
authors.forename: M
authors.initials: M
authors.lastname: Zhao
authors.forename: G
authors.initials: G
authors.lastname: Zhou
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
mesh_terms: D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000628:therapy*; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000628:therapy*; D006801:Humans; D006979:Hyperthermia, Induced / Q000295:instrumentation / Q000379:methods; D000077195:Squamous Cell Carcinoma of Head and Neck; D014407:Tumor Cells, Cultured; D014464:Ultrasonic Therapy / Q000295:instrumentation