De Fabo, am emeritus professor at SMHS comments:
"This is the first time that UV-induced melanin formation (tanning), traditionally thought to protect against skin cancer, is shown to be directly involved in melanoma formation in mammals. Skin melanoma is the most lethal of the skin cancers.
Our study shows that we were able to discover this new role for melanin by cleanly separating UVA from UVB and exposing our experimental melanoma animal model with these separated wavebands using our unique UV light system designed and set up at GW. Dermatologists have been warning for years there is no such thing as a safe tan and this new data appears to confirm this."
The team decided to examine how melanoma formed in response to accurately, spectrally defined ultraviolet wavelengths and biologically relevant doses in mammals.
Unlike ultraviolet B radiation (280-320 nm), which initiates the development of melanoma in a pigment-independent manner linked to direct ultraviolet B DNA damage, ultraviolet A (320-400 nm) requires the presence of melanin pigment and is linked to oxidative DNA damage within melanocytes.
The team discovered two ultraviolet pathways that depended on a certain wavelength for the induction of CMM, and found that melanin played an important and unexpected role in the melanocyte in melanoma genesis.
De Fabo declares:
"Also new is our discovery that UV induction of melanin, as a melanoma-causing agent, works when skin is exposed only to UVA and not UVB radiation. This is especially important since melanoma formation has been correlated with sun bed use as many epidemiological studies have shown. One possible reason for this is that tanning lamps are capable of emitting UVA radiation up to 12 times, or higher, the UVA intensity of sunlight at high noon. Melanin plus UVA is known to cause photo-oxidation, a suspected, but still to be proved, mechanism for the formation of melanoma as we describe in our study."
Written by Grace Rattue