University of California scientists found one particular strain of bacteria that lives on the skin could ward off skin cancer. It suppresses the spread of tumor cells triggered by too much exposure to the ultraviolet rays of the sun.
Although everyone has some strains of the bacterial species, only about 20 percent of people seem to have that particular strain, Dr. Richard Gallo, a physician-scientist at the University of California, San Diego, and the co-author of the study, said. However, the research – published in the February 28 issue of Science Advances – was based on studies using mice.
New skin cancer treatments
Not all studies conducted in animals produce similar results in humans. But the team hopes that by applying the knowledge they gained from the study, it could lead to new skin cancer treatments or preventive interventions based on the bacterial resources of skin microbiome in humans, Healthday reported.
The strain, Staphylococcus epidermidis, apparently produces 6-N-hydroxyaminopurine, a specific anti-cancer compound. This 6-HAP interferes with normal DNA processes by halting tumor cells in its tracks without causing any harm to the host. Because 6-HAP looks a lot like one of the building blocks of DNA, it made the researchers wonder if it interfered with DNA synthesis, Science News reported.
By injecting the strain directly into the bloodstream, it may inhibit the onset of cancer or curtail the growth of melanoma tumors by more than 50 percent. Gallo said that the unique strain of skin bacteria produces a chemical that kills several types of cancer cells but it does not appear to be toxic to normal cells, said Gallo, the chair of the University's Department of Dermatology.
At the time, the team was just looking for evidence that the Staph epidermidis can kill off pathogenic bacteria like group A strep. They were trying to expand proof that good bacteria can keep bad bacteria at bay, NBC reported.
Good bacteria help digest food, affect appetite, influence disease, and may control mood. Having healthy populations of good bacteria can out-compete pathogen-causing disease. It is the reason why doctors are using fecal transplants to treat patients with Clostridium difficile infections that can cause deadly chronic diarrhea.
Laboratory setting
The researchers started exploring the potential of 6-Hap in a laboratory setting. They exposed the cancerous tumor cells to the compound which resulted in reduced proliferation of some types of cancer. Then they tested the protective potential of intravenously injecting the 6-HAP into mice.
They injected 6-HAP into the mice once every 48 hours for two weeks to check how safe the procedure is. The researchers attempted to observe signs of toxic impact but failed to find any. They injected one of two types of the staph bacteria into a pool of mice that were exposed to a particularly aggressive form of fast-growing cancer. Their finding was that in all cases, the density of the injected bacteria was similar to levels usually found on the normal human skin.
One type of injected staph produced the 6-HAP compound, but the other did not. The mice injected with the bacteria that did not produce 6-HAP showed rapid tumor growth which was what the scientists expected. The number and growth of cancerous tumors fell from the rats injected with 6-HAP which produced bacteria.
The researchers noted previous observations that reported dybiosis -- a state of altered microbiome – may promote cancer. They cited as example observations that associate bacteria in the gut with an increase in carcinogenesis. It suggested that the effect was dependent on inflammation.
Understanding of the microbiome
Gallo said that more research needs to be conducted to understand exactly how the protective process works. Ashani Weeraratna, a professor and co-program leader of immunology, microenvironment, and metastasis at the Wistar Institute's Melanoma Research Center in Philadelphia, said an understanding of the microbiome is critical to harness the full potential of some of the outstanding immunotherapy available to treat cancers, like melanoma.
If scientists can understand whether a balance between one species of bacteria is better for a patient than another, they might be able to use low doses of antibiotics to encourage the growth of one bacteria over another. But Weeraratna said that bacteria tend to have a high mutation rate and a high potential for antibiotic resistance. She urged high caution for future studies in seeking to exploit the protective potential of the bacteria.
More than 1 million Americans get a new skin cancer diagnosis every year. These new patients are potential customers for MatriSys Bioscience, a company that Gallo helped establish to develop bacteria as medical treatments for skin conditions. Other teams are now working to develop bacteria into treatments for eczema and other skin conditions.
MatriSys has been experimenting with a lotion that uses two benign staph bacteria, the Staphylococcus hominis and Staphylococcus epidermidis, to fight the effects of the Staphylococcus aureus.
[researchpaper 리서치페이퍼=Vittorio Hernandez 기자]