DNA mutations in skin cells may signal a risk for melanoma long before it's visible to the eye, a new study suggests.
Exposure to sun damages skin and DNA, and this damage can be measured. Using a new method for analyzing DNA harm, researchers say they can estimate the risk of developing melanoma.
"It turns out that a multitude of individual cells in so-called normal skin are riddled with mutations associated with melanoma, which are a result of sun exposure," said researcher A. Hunter Shain, an assistant professor in the department of dermatology at the University of California, San Francisco.
"Melanoma is an endpoint most often seen only after decades of mutational damage, but some people are at greater risk than others. With the techniques we have developed, those who have the most accumulated mutations can be monitored more closely and can choose to better protect themselves from sun exposure," Shain said in a university news release.
Melanoma, which can be deadly, develops in skin cells called melanocytes. When melanocyte DNA is damaged, they can grow out of control.
The American Cancer Society says melanoma rates are rising. In 2020 about 100,000 people in the United States will be diagnosed with melanoma and nearly 7,000 will die.
For the study, the researchers sequenced DNA from 133 melanocytes. The cells came from two melanoma survivors and four cadavers of people who never had the skin cancer.
Melanocytes from the former cancer patients had more mutations, including melanoma-associated mutations, than skin from those who never had melanoma, the researchers found.
"Melanomas really can appear out of nowhere," Shain said. "We found out in this work that normal skin contains numerous melanocytes that already exhibit some of the mutations associated with cancer. Essentially, we found the precursors to the 70% of melanomas that do not arise from preexisting moles. Measuring mutations may be a good way to gauge the net effect of all these variables on melanoma risk."
The researchers noted that melanoma occurs more often on intermittently sun-exposed areas such as the back or thighs, compared with chronically exposed areas, such as the face. Consistent with this, Shain's team found more mutations on the back and limbs than on the head and neck.
"We anticipate that a streamlined, automated version of these methods will one day become widely available to gauge melanoma risk and could serve as the basis for cancer-screening recommendations," Shain said.
The report was published Oct. 7 in the journal Nature.