Shedding Light on the Sun's Cancer Threat

Sunlight may use a one-two punch to trigger skin cancer. Ultraviolet (UV) rays damage a key gene in skin cells involved in fighting off tumors, and at the same time appear to help these dangerous mutant cells survive sun exposure, says a report in the 26 November issue of the Proceedings of the National Academy of Sciences.

A team at Yale University, the Connecticut Center for Plastic Surgery, and the National Cancer Institute discovered that skin samples removed during plastic surgery from healthy individuals had numerous tiny patches of cells with damaged versions of the p53 tumor-suppressor gene. These patches are bigger and more common in sun-exposed skin (such as samples from nose jobs) than in shielded areas (such as those from tummy-tucks).

"The number of these [patches] was staggering," says paper co-author Douglas Brash, a Yale oncologist. On average, sun-shielded skin had three patches of mutant cells per square centimeter, whereas exposed skin had 33. The patches accounted for up to 4% of the epidermis in exposed skin.

Cells with mutant p53 genes are susceptible to cancer-causing mutations and survive UV radiation more often than do normal cells, which undergo programmed cell death when damaged by sunlight. "It's a double whammy," says Johns Hopkins University oncologist Michael Kastan, who says the study "implicates UV as an early step" in skin cancer. Amato Giaccia, a radiation oncologist at Stanford University, agrees. "It's a very important study," he says.