title: Human head and neck squamous cell carcinoma cell lines are differentially radiosensitised by the honeybee product Propolis.
abstract: OBJECTIVE
  Propolis, a product of honeybees, has anti-tumoural, cytotoxic, anti-metastatic and anti-inflammatory properties. The aim of this study was the evaluation of the radiosensitising capacity of Propolis in human head and neck squamous cell carcinoma (HNSCC) cells.
  
  
  METHODS
  HNSCC cell lines (FaDu, UT-SCC15, UT-SCC45), fibroblasts (HSF2) and keratinocytes (HaCaT) were treated with Propolis (0-250 g/ml; 1, 4, 24 h) without and in combination with X-rays (0-6 Gy, single dose). Clonogenic survival, proliferation, apoptosis, expression and phosphorylation of different signalling proteins were determined. Liquid chromatography-mass spectrometry (LC-MS) was performed on Propolis.
  
  
  RESULTS
  Propolis significantly (P < 0.01) reduced cell growth and clonogenic survival in a time- and concentration-dependent manner. Propolis-induced apoptosis and Caspase 3 cleavage, increased phosphorylation of Extracellular signal Regulated Kinase 1/2 (ERK1/2), protein kinase B/Akt1 (Akt1) and Focal adhesion kinase (FAK). While a 1-h Propolis pretreatment was ineffective, a 3-h pretreatment significantly (P < 0.05) radiosensitised FaDu cells. LC-MS analysis identified 14 compounds of Propolis.
  
  
  CONCLUSIONS
  Our data show that Propolis exerts cytotoxicity in a concentration- and time-dependent manner. In one out of three HNSCC cell lines, Propolis also caused an enhancement of radiosensitivity. Future studies on Propolis will shed further light on its potential as an adjuvant to radiotherapy.
authors.affiliation: OncoRay-Center for Radiation Research in Oncology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, Dresden.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Hehlgans
authors.forename: Inga
authors.initials: I
authors.lastname: Lange
authors.forename: Iris
authors.initials: I
authors.lastname: Eke
authors.forename: Bernd
authors.initials: B
authors.lastname: Kammerer
authors.forename: Nils
authors.initials: N
authors.lastname: Cordes
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology; D017209:Apoptosis; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000473:pathology* / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D002470:Cell Survival; D002853:Chromatography, Liquid / Q000379:methods; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006258:Head and Neck Neoplasms / Q000188:drug therapy* / Q000473:pathology* / Q000532:radiotherapy*; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D010766:Phosphorylation; D011429:Propolis / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013997:Time Factors
chemical_list: D000890:Anti-Infective Agents; D011838:Radiation-Sensitizing Agents; D011429:Propolis; D048049:Extracellular Signal-Regulated MAP Kinases