Short-term and long-term cellular and molecular events following UV irradiation of skin: implications for molecular medicine.

Acute ultraviolet (UV) irradiation of normal human skin results in several clinical effects, including sunburn inflammation (erythema) and tanning, histological changes such as thickening of the epidermis, and local or systemic immunosuppression. Chronic UV irradiation leads to photoaging, sustained immunosuppression and photocarcinogenesis. Photocarcinogenesis involves the accumulation of genetic changes, as well as immune system modulation, and ultimately leads to the development of skin cancers. Recent advances in molecular and cellular biology have clarified the mechanisms of photocarcinogenesis, including the formation of DNA photoproducts, DNA repair, the mutation of proto-oncogenes and tumour suppressor genes, and UV-induced immunosuppression. Further investigation and a better understanding of photocarcinogenesis are critical to the development of effective prevention and intervention strategies for human skin cancer.