Cancer treatment has long relied on surgery, chemotherapy, and immunotherapy. In recent years, scientists have also started looking at the gut microbiome for answers. A new study from Japan has taken this idea in a bold direction. Instead of changing gut bacteria indirectly, researchers isolated natural bacteria from frogs and reptiles and tested them directly against tumors.The study, led by Prof. Eijiro Miyako at the Japan Advanced Institute of Science and Technology (JAIST) and published in the journal Gut Microbes, reports that one bacterium showed striking anticancer effects in mice. The findings open a fresh conversation about how nature’s lesser-known microbes could shape future cancer care.
What the study explored and where the bacteria came from
The research team collected bacteria from the intestines of Japanese tree frogs, fire-belly newts, and grass lizards. In total, 45 bacterial strains were isolated and studied. Out of these, nine showed the ability to fight tumors in laboratory tests.One strain stood out clearly. It was Ewingella americana, a bacterium found in the gut of Japanese tree frogs (Dryophytes japonicus). Unlike engineered or modified bacteria, this strain was completely natural. The researchers then tested whether it could safely and effectively target cancer inside the body.
Tumor results that surprised cancer researchers
In mouse models of colorectal cancer, a single intravenous dose of Ewingella americana led to complete tumor elimination. Every treated mouse showed a complete response. This result was stronger than what researchers saw with commonly used treatments like doxorubicin and anti-PD-L1 immunotherapy.What made the finding more striking was the simplicity of the approach. One dose achieved what multiple rounds of chemotherapy and immunotherapy could not in this model. These results suggest that some natural bacteria may have untapped power against solid tumors, at least in early-stage research.
How the bacterium attacks cancer in two ways
The study shows that Ewingella americana works through a dual mechanism. First, it directly kills cancer cells. Tumors often have low oxygen levels, and this bacterium thrives in such environments. Within 24 hours, bacterial numbers inside tumors increased nearly 3,000 times, leading to cancer cell destruction.Second, the bacterium wakes up the immune system. Its presence attracts T cells, B cells, and neutrophils to the tumor site. These immune cells release signals like TNF-α and IFN-γ, which help trigger cancer cell death. Together, direct killing and immune activation create a stronger, more complete tumor attack.
Why were normal organs not harmed
One of the biggest concerns with bacteria-based cancer therapies is safety. This study paid close attention to that risk. The researchers found that Ewingella americana cleared from the blood within about 24 hours and did not settle in healthy organs such as the liver, lungs, kidneys, or heart.The bacterium showed a clear preference for tumors due to their low oxygen levels, leaky blood vessels, and altered metabolism. Any inflammation seen in mice was mild and temporary, settling within three days. Even after 60 days of observation, no long-term toxicity was found. This safety profile compared favorably with genetically modified bacterial treatments.What this could mean for future cancer treatmentThis research does not claim a ready-to-use cancer cure. What it does offer is proof that unexplored microbial biodiversity holds medical promise. The study suggests that natural bacteria from lower vertebrates could be developed into new cancer therapies without heavy genetic engineering.Future work will test this approach in other cancers, including breast and pancreatic cancer. Researchers will also explore safer dosing methods and combinations with existing treatments. If these results hold up in further studies, bacterial therapies could one day complement or even reduce reliance on harsh cancer drugs.Disclaimer: This article is for informational purposes only and is based on preclinical animal research. The findings have not yet been tested in humans. This content should not be taken as medical advice or a replacement for professional cancer treatment. Always consult qualified healthcare providers for diagnosis and treatment decisions.
