title: Effect of increased intracellular melanin concentration on survival of human melanoma cells exposed to different wavelengths of UV radiation.
abstract: OBJECTIVE
  To investigate the effect of intracellular melanin content on cell survival of G361 human melanoma cells following exposure to UV radiation.
  
  
  METHODS
  Cells were cultured in medium containing elevated concentrations of L tyrosine phosphate and L glutamine to increase their melanin content. Cell survival was assessed by colony-forming ability in treated and untreated cells following exposure to 254 nm germicidal UVC radiation (0-60 J m(-2)), 311 nm UVB radiation (0-5 kJ m(-2)), or broadband UVA radiation (Sellamed 4000, maximum output between 350 and 450 nm) (0-1.2 MJ m(-2)).
  
  
  RESULTS
  Treated cells, with a 2-fold increase in total melanin concentration and an increased ratio of eumelanin to pheomelanin, were marginally more resistant than untreated control cells to cell killing by 311 nm UVB radiation, but treatment had no effect on killing by germicidal UVC or broadband UVA radiation.
  
  
  CONCLUSIONS
  There was no evidence of any photosensitizing effect of increased melanin on human melanoma cell survival following exposure to UVC, UVB or broadband UVA radiation. The slight protective effect seen following exposure to UVB radiation may have been due to increased scavenging of reactive-oxygen species, particularly by eumelanin, at this wavelength.
authors.affiliation: National Radiological Protection Board, Chilton, Didcot OX11 ORQ, UK. christine.kowalczuk@nrpb.org.uk
authors.forename: C
authors.initials: C
authors.lastname: Kowalczuk
authors.forename: M
authors.initials: M
authors.lastname: Priestner
authors.forename: C
authors.initials: C
authors.lastname: Baller
authors.forename: A
authors.initials: A
authors.lastname: Pearson
authors.forename: N
authors.initials: N
authors.lastname: Cridland
authors.forename: R
authors.initials: R
authors.lastname: Saunders
authors.forename: K
authors.initials: K
authors.lastname: Wakamatsu
authors.forename: S
authors.initials: S
authors.lastname: Ito
mesh_terms: D002470:Cell Survival / Q000502:physiology / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D016166:Free Radical Scavengers / Q000378:metabolism; D006801:Humans; D008543:Melanins / Q000378:metabolism*; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy; D017319:Photosensitizing Agents / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D014466:Ultraviolet Rays
chemical_list: D016166:Free Radical Scavengers; D008543:Melanins; D017319:Photosensitizing Agents; C018362:pheomelanin; C041877:eumelanin