The large number of studies devoted to the effect of ultraviolet light on biological systems, contrasts with the lack of experimental data concerning the direct effects of visible light. It has been shown that blue light inhibited the growth of B16F10 melanoma cell lines and reduced the percentage of S phase cells. Yet these effects are poorly understood.
Materials and methods: Two cell lines and irradiation with blue light were used. Cell mortality and a possible mechanism of action were investigated.
Results: Exposure of B16F10 melanoma and bovine endothelial cells to blue light (wavelength 450 nm, 10 J/cm(2) from a Waldman lamp) induced a rapid and large reduction in viability followed by the death of virtually all the irradiated cells within 24 h. These results led us to expose a patient with haemorrhagic cutaneous melanoma metastasis to blue light. Irradiation led to an immediate arrest of haemorrhage, an inhibition of tumour growth and extensive tumour necrosis 24h after irradiation.
Conclusion: Exposure to blue light may offer new approaches to the treatment of superficial skin carcinomas in humans.