Researchers at George Washington University’s School of Medicine and Health Sciences (SMHS) have demonstrated, for the first time, that UV-induced melanin formation (tanning), which has traditionally been thought to protect against skin cancer, is directly involved in melanoma formation in mammals.
Under the direction of lead author Edward C. De Fabo, PhD, the team in George Washington’s SMHS used a mammalian model to investigate melanoma that formed in response to precise, spectrally-defined UV wavelengths and biologically relevant doses. According to the results of the study published in Nature Communications, “melanoma induction by ultraviolet A (320–400 nm) requires the presence of melanin pigment and is associated with oxidative DNA damage within melanocytes.” The abstract continues: “In contrast, ultraviolet B radiation (280–320 nm) initiates melanoma in a pigment-independent manner associated with direct ultraviolet B DNA damage.”
According to the researchers, this study identified two UV wavelength-dependent pathways for the induction of malignant melanoma of the skin; it also describes an unexpected and significant role for melanin within the melanocyte in melanoma genesis.
“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,” explains Dr. De Fabo, a professor emeritus at SMHS. “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.”
Dr. De Fabo says the discovery about melanoma induction in UVA versus UVB waves is especially important because “melanoma formation has been correlated with sunbed 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.”
