Melanocyte photobiology, ultraviolet radiation and melanoma

Of all the organs of the human body, the skin is most commonly affected by malignancy, and ultraviolet radiation has long been implicated as the primary mutagenic exposure leading to the development of many cutaneous cancers. However, as research in this field has continued, it has become clear that the effect of ultraviolet radiation on the skin is quite complex. Distinct cell types within the skin exhibit differing responses to ultraviolet radiation, and even within the same cell type, divergent effects may be observed; depending on the dose or wavelength of the radiation, or the maturational state of the affected cell, unique responses can be elicited. Melanocytes form a minor component of the outermost layer of skin, but they have an enormous impact on not only the appearance of the skin, but also the ability of the skin to withstand exposure to ultraviolet radiation. In addition, melanocytes give rise to melanoma, one of the most deadly types of skin cancer. Clearly, it is critical that we achieve a better understanding of the effect of ultraviolet radiation on melanocytes, and that we clarify its role in the oncogenesis of melanoma. Although the picture is far from complete, the mechanisms by which melanocytes respond to ultraviolet radiation are beginning to be elucidated, and, as these pathways emerge, they offer new targets for chemopreventive and chemotherapeutic intervention.