There may be an upside to allergies and asthma; protection against skin cancer

Scientists at Washington University School of Medicine in St. Louis have discovered a molecule involved in asthma and allergies that seems to make mice resistant to skin cancer.

The molecule, called TSLP (thymic stromal lymphopoietin), is produced by damaged skin and activates the immune system. Chronic low levels of TSLP are suspected in making the immune system oversensitive to what should be a harmless environment, leading to the skin rashes and overproduction of mucus common in allergies and asthma.

“But at extremely high levels, TSLP appears to train the immune system to recognize skin cancer cells, and target those cells for elimination,” says Raphael Kopan, PhD, the Alan A. and Edith L. Wolff Professor of Developmental Biology. “These experiments demonstrate that there is a way for a natural molecule to help immune cells recognize and reject tumors, at least in the skin.”

The study appears online Oct 15 in Cancer Cell.

These findings are surprising because most current evidence suggests that the allergic inflammation and release of TSLP increases — not decreases — the risk of tumor development.

The disparity may be explained by the amount of TSLP that is produced. The mice that were resistant to skin tumor growth had blood levels of TSLP that were 1,000-fold higher than normal. And levels in the skin — where it is made — may be even higher.

“This is an example of where hyper-vigilance of the immune system may end up paying dividends,” Kopan says. “Not only does it respond aggressively to an innocuous allergen, but it begins to monitor, survey and destroy cells that are mutant.”

The results are supported by another study in the same issue of Cancer Cell also showing TSLP prevents skin cancer in mice.