Inhibition of UV-induced p53 mutations and skin cancers by sunscreens: implication for skin cancer prevention.

The relationship between exposure to UVB radiation and development of skin cancer has been well established. Several studies have shown that UVB induces unique mutations (C to T and CC to TT transitions) in the p53 tumor suppressor gene that are not commonly induced by other carcinogens. Our studies have demonstrated that UV-induced mouse skin cancers contain p53 mutations at a high frequency and that these mutations can be detected in UV-irradiated mouse skin well before the appearance of skin tumors. This observation suggested that it might be possible to use p53 mutations as a biological endpoint for testing the efficacy of sunscreens in photoprotection studies. Indeed, application of SPF 15 sunscreens to mouse skin before each UVB irradiation resulted in 88-92% reduction in the number of p53 mutations. Because p53 mutations represent an early essential step in photocarcinogenesis, these results imply that inhibition of this event may protect against skin cancer development. This hypothesis is confirmed by our finding that sunscreens used in p53 mutation inhibition experiments also protected mice against UVB-induced skin cancer.