Effect of increased intracellular melanin concentration on survival of human melanoma cells exposed to different wavelengths of UV radiation

Purpose: To investigate the effect of intracellular melanin content on cell survival of G361 human melanoma cells following exposure to UV radiation. Materials and methods: Cells were cultured in medium containing elevated co ncentrations or L-tyrosine phosphate and L-glutamine to increase their mela nin content. Cell survival was assessed by colony-Forming ability in treate d and untreated cells following exposure to 254 nm germicidial UVC radiatio n (0-60 Jm(-2)) 311 nm UVB radiation (0-5 kJ m(-2)), or broadband UVA radia tion (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 concentrati on and an increased ratio of cumelanin to pheomelanin, were marginally more resistant than Untreated control cells to cell killing by 311 nm UVB radia tion, but treatment had no effect on killing by germicidal UVC or broadband UVA radiation. Conclusions : There was no evidence of any photosensitizing effect of incre ased melanin on human melanoma cell survival following exposure to UVC, UVB or broadband UVA radiation. The slight protective effect seen following ex posure to UVB radiation may have been due to increased scavenging of reacti ve-oxygen species, particularly by eumelanin, at this wavelength.