The slightest scratch can cause cancerous cells to crawl to the wound and form tumors in mice, a new study finds. The work may explain why certain kinds of cancers seem to cluster around burns, surgical scars and other injuries.
“This work says that if you have a predisposition to getting cancer, wounding might enhance the chance that it will develop,” says cell biologist Anthony Oro of Stanford University School of Medicine.
A variety of human cancers have been tied to wounds, including lung, liver, bone and skin cancers, but just how and why has been unclear. In the new study, Sunny Wong and Jeremy Reiter of the University of California, San Francisco, introduced a potentially cancer-causing mutation into particular stem cells in mice.
The stem cells live in the part of a hair follicle called the follicular bulge, where they produce new follicles and hair shafts. The researchers expected to see tumors develop around the hair follicles in the mutated mice. But the mice were fine.
If the mice were wounded, however, tumors developed at the injury site. After a pencil-eraser-sized piece of skin was cut from the backs of the mice, cancerous cells migrated to the wound and formed clusters of tumors. These tumors seemed to be a slow-growing and treatable form of skin cancer called basal cell carcinoma. Small incisions similar to paper cuts also caused these stem cells to form tumors nearby, while plucking single hairs did not, the team reports in an upcoming Proceedings of the National Academy of Sciences.
“It’s a very suggestive study that needs to be confirmed on a broader level. But it will certainly stimulate a lot of discussion and interest in this area in the future,” Oro says.
Something in the hair follicle environment may keep these mutated stem cells in check. But a wound calls these stem cells out, making them leave their normal location, travel to the injury site and form tumors, the team found. Just how wounding beckons these cells is a mystery, Reiter says. “It’s a fascinating question but I don’t think anyone knows at this point.”
In the mice, mutated stem cells could still form tumors even if the injury came several weeks after the researchers introduced the mutation. “The bad news is that these primed sleeper cells can exist within the [follicular] bulge and come forward later,” Reiter says.
The new research focused on one particular mutation and one particular cell type, so further studies will be needed to test whether the same sort of thing happens in other tissues and for other kinds of cancer.
