Chemoprevention of Ultraviolet Radiation-induced Skin Cancer
Ronald D. Ley1 and Vivienne E. Reeve2
1Photomedicine Program, The Lovelace Institutes, Albuquerque,
New Mexico; 2Department of Veterinary Pathology, University
of Sydney, New South Wales, Australia
Abstract
The use of chemical and physical sunscreening agents has increased dramatically during the last two to three decades as an effective means of preventing sunburn. The use of high sun- protection factor sunscreens has also been widely promoted for the prevention of skin cancer, including melanoma. Whereas sunscreens are undoubtedly effective in preventing sunburn, their efficacy in preventing skin cancer, especially melanoma, is currently under considerable debate. Sunscreens have been shown to prevent the induction of DNA damage that presumably results from the direct effects of ultraviolet radiation (UVR) on DNA. DNA damage has been identified as an initiator of skin cancer formation. However, both laboratory and epidemiological studies indicate that sunscreens may not block the initiation or promotion of melanoma formation. These studies suggest that the action spectrum for erythema induction is different than the action spectrum for the induction of melanoma. Indeed, recent reports on the wavelength dependency for the induction of melanoma in a fish model indicate that the efficacy of ultraviolet A wavelengths (320-400 nm) to induce melanoma is orders of magnitude higher than would be predicted from the induction of erythema in man or nonmelanoma skin tumors in mice. Other strategies for the chemoprevention of skin cancer have also been reported. Low levels and degree of unsaturation of dietary fats protect against UVR-induced skin cancer in mice and humans. Compounds with antioxidant activity, including green tea extracts (polyphenols), have been reported to inhibit UVR-induced skin carcinogenesis. -- Environ Health Perspect 105(Suppl 4):981-984 (1997)
Key words: ultraviolet radiation, skin cancer, chemoprevention, sunscreens, DNA damage, melanoma, erythema, immunosuppression
This paper is based on a presentation at the symposium on Mechanisms and Prevention of Environmentally Caused Cancers held 21-25 October 1995 in Santa Fe, New Mexico. Manuscript received at EHP 16 April 1996; accepted 23 August 1996.
Address correspondence to Dr. R.D. Ley, The Lovelace Institutes, 2425 Ridgecrest Drive, SE, Albuquerque, NM 87108. Telephone: (505) 262-7560. Fax: (505) 262-7043. E-mail: rley@lrri.org
Abbreviations used: PABA, p-aminobenzoic acid; SPF, sun protection factor; UV-A, ultraviolet A (320-400 nm); UV-B, ultraviolet B (280-320 nm); UVR, ultraviolet radiation.
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Last Update: June 30, 1997