Experiments on mice, reported in the Proceedings of the National Academy of Sciences, suggest that caffeine prevents UV damage.
The researchers did not apply caffeine to the mice, instead they genetically modified the animals.
Caffeine is known to interfere with a protein involved in detecting DNA damage called ATR. Scientists modified the mice so they did not produce any ATR in the skin.
Those without ATR developed their first tumour three weeks later than normal mice. "Caffeine application could be useful in preventing UV-induced skin cancers," the researchers add.
Applying caffeine on a beach to a person's skin, however, is not the same thing as genetically modifying mouse skin in a laboratory. Prof Dot Bennett, professor of cell biology, St George's, University of London, said: "The authors suggest adding caffeine or related molecules to sunscreens.
"First one might want to check there is no adverse effect of caffeine on the incidence of other cancers, especially melanoma, pigmented skin cancer, which kills over four times as many people as squamous cell carcinoma.
"But caffeine lotion might promote tanning a little, since this family of molecules stimulates pigment cells to make more pigment."
“Combined with the extensive epidemiologic data linking caffeine intake with decreased skin cancer development, these findings suggest the possibility that topical caffeine application could be useful in preventing UV-induced skin cancers.
Previous research has suggested that drinking coffee could reduce risk of developing skin cancer, as caffeine appears to kill off cells that have been damaged by ultraviolet radiation from the sun before they become cancerous.
Caffeine is known to suppress ATR, causing the damaged cells to die rather than turn cancerous, so the mice were mimicking its effect.
Epidemiological studies have shown that drinking caffeinated beverages reduces one’s chances of developing some types of cancer, including UV-associated skin cancer. Several epidemiologic studies have suggested that coffee and tea drinkers are at a decreased risk for a variety of human cancers, including UV-associated skin cancer. Mouse studies have also confirmed the link, with both ingested and topically-applied caffeine lowering skin cancer rates in the animals. By inhibiting ATR activity, caffeine could make cells more likely to die in response to UV damage, preventing damaged cells from ever becoming cancerous.
To test this hypothesis, cancer biologist and dermatologist Paul Nghiem of the University of Washington Dermatology examined mice that were sensitive to UV damage, and thus prone to skin cancer. Exposing the mice to UV radiation, the researchers found that it took transgenic mice about 3 weeks longer to develop skin cancer than their transgene-negative littermates. The researchers also tested the skin cells from the mice in vitro, adding caffeine shortly after UV exposure. To formulate [caffeine] into existing sunscreens as an additive?”