Beneficial skin bacteria may protect against skin cancer, according to a new study in Science Advances.

“We have identified a strain of Staphylococcus epidermidis, common on healthy human skin, that exerts a selective ability to inhibit the growth of some cancers,” says Richard Gallo, MD, PhD, Distinguished Professor and chair of the Department of Dermatology at University of California San Diego School of Medicine, in a news release. “This unique strain of skin bacteria produces a chemical that kills several types of cancer cells but does not appear to be toxic to normal cells.”

The University of California San Diego School of Medicine researchers discovered the S. epidermidis strain produces the chemical compound 6-N-hydroxyaminopurine (6-HAP). Mice with S. epidermidis on their skin that did not make 6-HAP had many skin tumors after being exposed to cancer-causing ultraviolet rays (UV), but mice with the S. epidermidis strain producing 6-HAP did not.

6-HAP is a molecule that impairs the creation of DNA and prevents the spread of transformed tumor cells as well as the potential to suppress development of UV-induced skin tumors.

Mice that received intravenous injections of 6-HAP every 48 hours over a two-week period experienced no apparent toxic effects, but when transplanted with melanoma cells, their tumor size was suppressed by more than 50 percent compared to controls, the study showed.

“There is increasing evidence that the skin microbiome is an important element of human health. In fact, we previously reported that some bacteria on our skin produce antimicrobial peptides that defend against pathogenic bacteria such as, Staph aureus,” says Gallo.

In the case of S. epidermidis, it appears to also be adding a layer of protection against some forms of cancer, says Gallo. Further studies are needed to understand how 6-HAP is produced, if it can be used for prevention of cancer or if loss of 6-HAP increases cancer risk.

PHOTO CREDIT: UC San Diego Health

PHOTO CAPTION: S. epidermidis growing on an agar plate. A strain of S. epidermidis was shown to produce a molecule that kills cancer cells and inhibits the development of skin tumors on mice.