Defense Against Skin Cancer May Live on Your Skin
WEDNESDAY, Feb. 28, 2018 (HealthDay News) -- Bacteria that commonly live on your skin's surface just might be protecting you from cancer.
Researchers from the University of California, San Diego, said that one particular strain of bacteria appears to help ward off skin cancer by suppressing the spread of tumor cells triggered by over-exposure to the sun's ultraviolet (UV) rays.
The new research, based on studies using mice, was published in the Feb. 28 issue of Science Advances.
"Everyone has some strains of this bacterial species," explained Dr. Richard Gallo, the study's co-author. "About 20 percent seem to have this particular strain." Gallo is chairman of the university's dermatology department.
Still, the revelation that it engages in anti-cancer activity "is entirely new," he said.
So could the fresh finding lead to new skin cancer treatments or preventive interventions based on the bacterial resources of people's own "skin microbiome"?
"It is early to say for sure," Gallo said. "But the hope is that applying this could protect people as well as we have shown it works in mice."
However, experts point out that research conducted in animals frequently doesn't produce similar results in humans.
Many types of bacteria reside harmlessly on the surface of a healthy human body. But the specific bacteria in question -- a strain called Staphylococcus epidermidis -- appears to produce a specific anti-cancer compound known as 6-N-hydroxyaminopurine (6-HAP), the researchers found.
By interfering with normal DNA processes, 6-HAP appears to halt tumor cells in their tracks without causing any harm to the host.
In addition, the researchers said, preliminary animal testing suggested that even more may be possible. Injecting 6-HAP directly into the bloodstream may inhibit the onset of cancer or curtail the growth of melanoma tumors by more than 50 percent, they noted.
The study team pointed out that, each year, more than one million Americans get a new skin cancer diagnosis.
The new study began with the researchers exploring the potential of 6-HAP in a laboratory setting. Cancerous tumor cells were exposed to the compound, resulting in reduced proliferation of some types of cancer, according to their report.
Next, the researchers tested the protective potential of intravenously injecting 6-HAP into mice.
To check how safe such a procedure would be, the team injected the compound once every 48 hours for two weeks, watching for signs of toxic impact. No toxicity was observed in the mice.
Then, one of two types of the staph bacteria were injected into a pool of mice who were exposed to a particularly aggressive form of fast-growing cancer. In all cases, the "density" of the injected bacteria was described as similar to levels typically found on normal human skin.
The researchers found that one type of injected staph produced the 6-HAP compound, but the other did not.
Mice that had been injected with the bacteria that did not produce 6-HAP experienced rapid tumor growth, which the researchers said they'd expected. But those injected with 6-HAP-producing bacteria saw the number and growth of cancerous tumors fall off "significantly," the investigators found.
Gallo and his colleagues said their findings suggest that this common skin bacteria may help guard against the development of skin cancer. However, they added that more research will be needed to understand exactly how the protective process works, as well as to explore how it might be harnessed to serve as an effective anti-cancer treatment in people.
That thought was seconded by Ashani Weeraratna, a professor and co-program leader of immunology, microenvironment and metastasis at the Wistar Institute's Melanoma Research Center in Philadelphia.
"I think a lot of rigorous research is still required," she said.
"It's clear that an understanding of the microbiome -- the bacterial landscape, so to speak -- is critical to harness the full potential of some of the outstanding immunotherapy we have available to treat cancers, like melanoma," Weeraratna said.
"Therefore, these findings are very important," she noted.
"If we can understand whether a balance between one species of bacteria is better for a patient than another, we might be able to use low doses of antibiotics to encourage the growth of one bacteria over another," Weeraratna suggested.
However, she added that bacteria tend to have a high mutation rate, and thus a high potential for giving rise to antibiotic resistance. Because of this, future studies seeking to exploit the protective potential of skin bacteria "would have to be attempted with high caution," Weeraratna warned.
The U.S. National Institutes of Health has more on the human microbiome.
SOURCES: Richard L. Gallo, M.D., Ph.D., professor and chairman, dermatology, University of California, San Diego; Ashani T. Weeraratna, Ph.D., professor and co-program leader, immunology, microenvironment and metastasis, Melanoma Research Center, Wistar Institute, Philadelphia; Feb. 28, 2018,