Role of UV in cutaneous melanoma.

Malignant melanoma arises from epidermal melanocytes, the cells responsible for the production of the skin pigment melanin. The photoprotective role of melanin, which is transferred to neighboring keratinocytes, in UV-induced skin carcinogenesis, specifically in nonmelanoma skin cancers, has been well documented. Although melanocyte-resident melanin is expected to offer similar protection to melanocytes from UV-induced damage, UV radiation has long been suspected to have an etiologic role in cutaneous melanoma. However, nearly three decades of efforts using a variety of in vitro and in vivo models of human skin and mouse genetic models have produced conflicting data. Epidemiologic studies have also failed to establish a definitive association between UV exposure and risk of melanoma. In this review, we evaluate the dual role of the melanin pigment as a photoprotector as well as a photosensitizer and examine the evidence for association between melanin levels (constitutive and induced) and melanoma risk. We also discuss possible reasons for the lack of signature UV mutations in melanoma oncogenes known to date and potential alternative mechanisms to explain the role of UV in melanomagenesis.