By Clare Hagerty
Caffeine guards against certain skin cancers at the molecular level, according to a study appearing online August 15, 2011, in the Proceedings of the National Academy of Sciences (PNAS) that explains how the process likely works. Senior author Dr. Paul Nghiem, associate professor of dermatology and pathology at the University of Washington School of Medicine, and colleagues genetically modified mice so the rodents would have diminished function of a protein enzyme in their skin known as ATR. Several studies have reported that in humans, caffeine consumption in the form of tea or coffee is associated with lower incidences of non-melanoma skin cancers, although the mechanism for this is unclear. (Decaffeinated beverages have no effect.)
Prior research has indicated caffeine inhibits ATR, along with other enzymes that facilitate DNA repair. While this repair activity is often beneficial, it can also contribute to the emergence of some cancers. When exposed to ultraviolet light, the genetically modified mice developed tumors three weeks after unmodified mice did. After 19 weeks of ultraviolet light exposure, the lab-generated mice had 69 percent fewer tumors than regular mice. They also developed four times fewer invasive tumors. Continued chronic ultraviolet irradiation, however, eventually caused tumor development in all of the mice after 34 weeks of exposure.
“This study has been 10 years in the making,” Nghiem explained, “since it is much more difficult to genetically target this protein enzyme specifically. But what it suggests is that caffeine’s protective effect against ultraviolet damage, which we’ve documented in other studies, is likely due to ATR inhibition.”
That means this guarding most likely works at the pre-cancerous stage, Nghiem said, before UV-induced skin cancers fully develop.
“In past studies, we’ve been able to show that caffeine decreases the incidence of skin cancer development,” Nghiem said. “In this study, we set out to determine how that works and how the body protects itself from skin cancer. We were able to show that caffeine manipulates the pathway of this protein in a live mouse by suppressing ATR’s function.”
With more than a million new cases in the United States each year, non-melanoma skin cancer is the most common form of cancer in humans. The researchers suggest that topical application of caffeine could be useful in preventing such cancers, with the added benefit that it directly absorbs UV light, thus acting as a sunscreen.