Ultraviolet A and melanoma: A review

The incidence and mortality rates of melanoma have risen for many decades i n the United States. Increased exposure to ultraviolet (UV) radiation is ge nerally considered to be responsible. Sunburns, a measure of excess sun exp osure, have been identified as a risk factor for the development of melanom a. Because sunburns are primarily due to UVB (280-320 nm) radiation, UVB ha s been implicated as a potential contributing factor to the pathogenesis of melanoma. The adverse role of UVA (320-400 nm) in this regard is less well studied, and currently there is a great deal of controversy regarding the relationship between UVA exposure and the development of melanoma. This art icle reviews evidence in the English-language literature that surrounds the controversy concerning a possible role for UVA in the origin of melanoma. Our search found that UVA causes DNA damage via photosensitized reactions t hat result in the production of oxygen radical species. WA can induce mutat ions in various cultured cell lines. Furthermore, in two animal models, the hybrid Xiphophorus fish and the opossum (Mondelphis domestica), melanomas and melanoma precursors can be induced with UVA. UVA radiation has been rep orted to produce immunosuppression in laboratory animals and in humans. Som e epidemiologic studies have reported an increase in melanomas in users of sunbeds and sunscreens and in patients exposed to psoralen and UVA (PUVA) t herapy. There is basic scientific evidence of the harmful effects of UVA on DNA, cells and animals. Collectively, these data suggest a potential role for UVA in the pathogenesis of melanoma. To date evidence from epidemiologi c studies and clinical observations are inconclusive but seem to be consist ent with this hypothesis. Additional research on the possible role of UVA i n the pathogenesis of melanoma is required.