When people reach late middle age, about a quarter of their skin cells carry cancer-driving mutations caused by exposure to sunlight. This phenomenon is not only normal; it may not even signal any reason for concern about tumor growth, according to a study published in the May 22 issue of Science and reported by Tina Hesman Saey in Science News (https://www.sciencenews.org/article/mutations-drive-cancer-lurk-healthy-skin).
While researchers used to think that the types of mutations that lead to tumor growth were "rare and happened just before a cell becomes cancerous," a study of the eyelids of four people who do not have cancer demonstrates that such mutations "are staggeringly common in normal skin," according to Philip Jones, a clinical scientist at the University of Cambridge, the article explains. Jones's team procured 234 skin samples from four people ages 55 to 73 who had plastic surgery to correct droopy eyelids. After DNA sequencing, it was revealed that approximately 20 percent of the skin cells had mutations in the NOTCH1gene. According to the article in Science, that gene, when mutated, is "a driving force in some cancers, including skin cancers called squamous cell carcinomas."
Dr. Jones, who is a clinical doctor treating patients with cancer and also a scientist researching how the behavior of normal cells changes as they turn into cancer cells, is interested in tracking the fate of large numbers of cells and analyzing the data to understand the mathematical "rules" of cell behavior. "Normal cells follow a remarkably simple set of rules, which are only subtly distorted in cancer," he said.
"Once we know what the rules are, we can both predict cell fate and test how drugs and genes alter cell behavior far more efficiently than before. We are now starting to apply this work to human tissue samples and cancer cells to try to prevent cancers developing and improve cancer treatment," according to Dr. Jones in Health & Medicine News (http://hmnews.org/).
According to the National Cancer Insititute, skin cancer is the most common neoplasm in Caucasians in the United States "with a lifetime risk nearly equal to that of all other cancers combined." More than 800,000 people are likely to develop nonmelanoma skin cancer -- basal cell carcinoma (BCC) or squamous cell carcinoma (SCC)] -- annually in the United States. Sun exposure is the major environmental culprit. Although sun exposure is likely to begin early in life, the average patient with nonmelanoma skin cancer is about 60 years old. Researchers have established a connection between sun exposure and nonmelanoma skin cancer and have shown the sequence of events occurring between the time of initial sun exposure and subsequent skin cancer years later http://www.ncbi.nlm.nih.gov/pmc/articles/PMC33651/).