And skin cancer is striking at ever younger ages. One-quarter of the more than 30,000 people expected to develop melanoma this year will be 39 or younger. A fourth type of growth, actinic or solar keratosis, is also of concern because it can progress into cancer. It's the most common pre-malignant skin condition, occurring in more than 5 million Americans. While there's no question that UV damages DNA, scientists had long suspected that it delivers a double whammy.
Recent research supports that idea.
Developing skin cancer is at least a two-step process, involving initiation and promotion of malignant growth. In studies with mice, Brash and colleagues showed that UV harms a mechanism for repairing cell damage. Once the repair system is impaired, cells become increasingly vulnerable to injury. Subsequent UV exposures just make matters worse, and can initiate malignancy. After UV exposure, the repair mechanism normally directs damaged cells to commit suicide.