Common Skin Bacterium Could Offer Protection Against Cancer
Mammalian skin harbors diverse microbial communities whose growth is influenced by ecological factors on the body surface such as humidity, temperature, pH, lipid content, and the presence of antimicrobials produced by the host. And this interplay of microbe and host appears is critical for establishing homeostasis but is poorly understood.
Coagulase-negative staphylococcal species, such as Staphylococcus epidermidis, Staphylococcus hominis, and others, are the predominant bacterial species that colonize normal human skin, whereas Staphylococcus aureus frequently colonizes abnormal skin such as that found in patients with atopic dermatitis.
Now, in the recent study, researchers University of California San Diego School of Medicine researchers report a potential new role for some of these bacteria on the skin: protecting against cancer.
“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,” said Richard Gallo, MD, PhD, Distinguished Professor and chair of the Department of Dermatology at UC San Diego School of Medicine. “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 finding was somewhat serendipitous. With previous
research showing that chemicals produced by Staphylococcus species commonly found on healthy human skin can kill off certain harmful bacteria, the team looked at numerous strains to explore their antimicrobial powers.
They were testing various strains of Staphylococcus from human skin, and found one that killed group A strep, which cause a range of pesky infections from strep throat to cellulitis. They can take on a flesh-eating form, causing necrotizing fasciitis, also.
Whatever it was that the staph bacteria made, it was not a protein — the usual product that cells make and secrete, they reported in the journal Science Advances.
Instead, it was a molecule called 6-N-hydroxyaminopurine (6-HAP for short). It interferes with DNA polymerase activity and slowed the proliferation of tumor cells.
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.
“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,” said Gallo.
Julian Marchesi, professor of human microbiome research at Cardiff University who was not involved in the study, welcomed the findings. “[This research] further adds to a growing understanding of how important the human microbiota, and in this case the skin microbiome, is to health. We have evolved to need these microbes and desperately need to understand all the roles they play in human biology and start to think more about what it is to be a human being,” he told The Gaurdian. “The next stage of this exciting work, will be to translate it to human clinical trials and show that this bacterially produced chemical can protect the host from skin cancers.”
