Repair of UV-induced DNA damage and melanoma risk

Melanoma is relatively uncommon compared with nonmelanoma skin cancers, but it causes a vast majority of skin-cancer deaths. Sunlight exposure, particularly intermittent sun exposure early in life, is a well-established risk factor for melanoma. Because only a fraction of those exposed to sunlight ever developed melanoma, genetic susceptibility has long been suspected to be an etiological factor in sunlight-induced melanoma. For example, people who have a strong family history of dysplastic nevus syndrome have an increased risk of melanoma. The extremely high frequency and early onset of melanomas in patients with xeroderma pigmentosum (XP), a rare autosomal-recessive disease of mutated DNA repair genes that confer hypersensitivity to ultraviolet light, suggest that DNA repair is involved in the etiology of melanoma. Until recently, not enough population-based data were available to support the idea that DNA repair plays a role in the etiology of sporadic melanoma, but recent studies suggest that patients with sporadic melanoma, particularly those with sunlight-sensitive skin, have a low DNA repair capacity (DRC). This theory was also supported by studies showing that patients with melanomas on sun-exposed skin had a lower DRC than did patients with melanomas on unexposed skin. Furthermore, studies found that the risk of melanoma increased as DRC decreased. Taken together, these new data suggest that reduced DRC contributes to genetic susceptibility to sunlight-induced sporadic melanoma in the general population. More studies are needed to validate that DRC is a marker for genetic susceptibility to melanoma. With advances in high-throughput technology, individuals at increased risk for melanoma could be screened for functional variants of DNA repair genes, leading to primary prevention of sunlight-induced melanoma in the general population.