🐸 A Frog Gut Bacterium Eliminated Colorectal Tumors in Mice
A bacterium found in the gut of Japanese tree frogs has shown a striking anti-cancer effect in mice.
Researchers at the Japan Advanced Institute of Science and Technology (JAIST) screened 45 bacterial strains isolated from amphibians and reptiles, including Japanese tree frogs, fire belly newts, and grass lizards. One strain stood out: Ewingella americana, a naturally occurring bacterium from the intestines of the Japanese tree frog.
In a mouse model of colorectal cancer, a single intravenous dose of E. americana led to complete tumor elimination in all treated mice — a 100% complete response rate in that experiment.
The bacterium appears to work in two ways.
First, it accumulates inside tumors, where oxygen levels are low and blood vessels are unusually leaky. Once there, the bacterial population increased by roughly 3,000 times within 24 hours, directly damaging cancer cells.
Second, it seems to wake up the immune system. The treatment attracted T cells, B cells, and neutrophils into the tumor and boosted inflammatory signals such as TNF-α and IFN-γ, helping the body attack the cancer more aggressively.
The safety data in mice were also encouraging. The bacteria disappeared from the bloodstream within 24 hours, did not colonize healthy organs such as the liver, spleen, lungs, kidneys, or heart, and caused only temporary mild inflammation. Over a 60-day observation period, the researchers reported no chronic toxicity.
But the caveat is essential: this is still mouse research.
Many cancer therapies look spectacular in preclinical models and fail later in humans. A living bacterium injected into the bloodstream would face a much higher safety bar in people, and the human immune response could be very different.
Still, the study is an unusually strong proof of concept for bacterial cancer therapy. Instead of simply changing the gut microbiome, the researchers used a living bacterium as a tumor-targeting agent — one that both attacks cancer cells and recruits the immune system.
The big takeaway: one of the next ideas in cancer therapy may come not from a synthetic drug library, but from the gut of a frog.
Original paper, Gut Microbes: https://www.tandfonline.com/doi/full/10.1080/19490976.2025.2599562
DOI: https://doi.org/10.1080/19490976.2025.2599562
ScienceDaily summary: https://www.sciencedaily.com/releases/2026/07/260709160655.htm
JAIST press release: https://www.jaist.ac.jp/english/whatsnew/press/2025/12/17-1.html
#CancerResearch #Microbiome #Immunotherapy #Biotech