Japanese Tree Frog Gut Bacteria Eliminates Cancer: A Breakthrough Discovery from JAIST
A "Living Medicine" Hidden in Frog Intestines
The Japanese tree frog, a small green amphibian commonly found in rice paddies and gardens across Japan, may hold the key to revolutionizing cancer treatment.
A research team led by Professor Eijiro Miyako at the Japan Advanced Institute of Science and Technology (JAIST) has demonstrated that a bacterium called Ewingella americana, isolated from the intestines of Japanese tree frogs, can completely eliminate colorectal cancer in mice with just a single injection. This groundbreaking research was published in the international journal Gut Microbes on December 10, 2025.
Why Amphibians Caught Scientists' Attention
Have you ever heard of a frog or lizard getting cancer? Probably not. This isn't simply because we don't observe these animals closely enough. In fact, biologists have long noted that spontaneous tumors are remarkably rare in wild amphibians—a mystery that has puzzled scientists for years.
With recent advances revealing the profound influence of gut bacteria on immune function and cancer progression, the research team hypothesized that the unique gut microbiome of amphibians might harbor cancer-fighting secrets.
Finding a "Super Bacterium" Among 45 Strains
The research team collected gut bacteria from three species of amphibians and reptiles native to Japan. Their subjects included the Japanese tree frog (Dryophytes japonicus), the Japanese fire belly newt (Cynops pyrrhogaster), and the Japanese grass lizard (Takydromus tachydromoides).
From these animals, they isolated a total of 45 bacterial strains and systematically screened them for safety and antitumor effects. Nine strains showed antitumor activity, but one stood out dramatically: Ewingella americana from the Japanese tree frog.
Achieving an Unprecedented 100% Complete Response Rate
In a mouse colorectal cancer model, a single intravenous administration of E. americana achieved complete tumor elimination with a 100% complete response (CR) rate. This dramatically surpasses the efficacy of current standard treatments, including immune checkpoint inhibitors (anti-PD-L1 antibody) and chemotherapy agents (liposomal doxorubicin).
In comparative trials, chemotherapy and immunotherapy showed only partial effectiveness in some mice. In contrast, every single mouse in the bacterial treatment group saw their tumors completely disappear.
Even more remarkable was the durability of this cure. When researchers attempted to re-implant cancer cells into the cured mice 30 days later, the tumors failed to grow. This suggests that the bacterial treatment had effectively "vaccinated" the mice, generating an immunological memory that rejected cancer upon recurrence.
A Dual-Action Attack Mechanism
The exceptional anticancer effect of E. americana stems from its unique two-pronged attack mechanism.
Direct Cytotoxic Effect
This bacterium is a facultative anaerobe—it can survive in oxygen but thrives in low-oxygen environments. The core of solid tumors is typically hypoxic, creating a fortress that many anticancer drugs struggle to penetrate. For E. americana, however, this oxygen-starved environment is the perfect habitat.
Within 24 hours of administration, bacterial counts within tumors increased approximately 3,000-fold. This explosive growth enables direct destruction of cancer cells.
Immune Activation Effect
The bacterial presence powerfully stimulates the immune system, recruiting T cells, B cells, and neutrophils to the tumor site. These immune cells produce pro-inflammatory cytokines (TNF-α, IFN-γ) that further amplify immune responses and induce cancer cell apoptosis.
This combination of "direct attack" and "immune activation" produces effects that far exceed conventional treatments.
Precision Targeting: Tumors Only
Perhaps the most remarkable feature of this bacterium is its extraordinary tumor specificity. E. americana selectively accumulates in tumor tissues while showing zero colonization in normal organs.
This selectivity arises from multiple factors unique to the tumor environment. The hypoxic conditions inside tumors promote anaerobic bacterial proliferation. Cancer cells express CD47 protein, creating local immunosuppression that forms a permissive niche for bacterial survival. The abnormal, leaky blood vessels in tumor tissue facilitate bacterial entry. Additionally, tumor-specific metabolites support selective bacterial growth.
An Excellent Safety Profile
Comprehensive safety evaluation revealed impressive results. Regarding blood clearance, the bacterium has a half-life of approximately 1.2 hours and becomes completely undetectable within 24 hours. For normal organ effects, zero bacterial colonization was found in the liver, spleen, lungs, kidneys, or heart. The inflammatory response was only transient and mild, normalizing within 72 hours. Long-term observation over 60 days showed no chronic toxicity.
Importantly, the bacterium is sensitive to standard antibiotics, providing a safety "kill switch" if any problems arise during treatment.
Future Prospects and Challenges
This research has established proof-of-concept for a novel cancer therapy using natural bacteria. The research team plans to pursue several avenues. For expansion to other cancer types, they will validate efficacy in breast cancer, pancreatic cancer, melanoma, and other malignancies. For optimization of administration methods, they will develop safer and more effective delivery approaches, including dose fractionation and intratumoral injection. For combination therapy development, they will investigate synergistic effects with existing immunotherapy and chemotherapy.
However, it's crucial to note that these results were obtained in mouse models. Translation to human applications will require further research, including additional safety confirmation, determination of appropriate dosing, and detailed mechanistic studies of how the bacteria reach and attack tumors.
Biodiversity: A Treasury of Medical Innovation
Professor Miyako stated, "This research demonstrates that unexplored biodiversity represents a treasure trove for new medical technology development, while potentially providing new treatment options for patients with refractory cancers."
The discovery that a common frog's gut harbors potential weapons against one of humanity's deadliest diseases reminds us that nature still holds countless medical treasures waiting to be discovered.
What about your country? Is research on gut bacteria or microbiome-based cancer treatments advancing? Have there been any discoveries of medical applications from common animals in your region? We'd love to hear your thoughts!
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Reactions in Japan
A 100% complete response rate in mouse experiments is honestly an unbelievable level of results. But reading the paper, the methodology is solid. It's unknown how it will work in humans, but this is research I can't wait to see replicated.
As a clinical oncologist, let me say that there are countless drugs that work in mice but fail in humans. I'm hopeful, but practical application could take over 10 years. I want patients to receive this news calmly.
I can't believe the tree frogs near my house have such amazing power! There's something romantic about the idea that the frogs I used to catch and play with as a child might save humanity.
This is a perfect example showing the importance of biodiversity conservation. The potential for undiscovered useful substances and functions in familiar organisms is limitless. We need to advance research before they're lost to environmental destruction.
I really suffered from chemotherapy side effects. If a treatment with fewer side effects like this becomes practical in the future, think how many patients could be saved. Researchers, please keep up the great work.
Isn't the media headline 'cancer elimination' too sensational? This is still just at the mouse experiment stage. Remember how iPS cells were hyped as a 'dream treatment' - how's that going? I'd like to see more measured reporting.
Quality control for administering live bacteria as medicine is extremely difficult. Effects might vary with culture conditions, and establishing manufacturing processes will be a major challenge. But it's worth the challenge.
I'm proud that a world-class discovery came from JAIST! It's a graduate university in Nomi City, and many locals don't even know about it, but they were doing such amazing research. I hope they promote Hokuriku's science and technology more.
Please don't forget the ethical issues of animal experiments. Frogs and lab mice are being sacrificed for research. While celebrating the results, I think we need discussion about animal welfare too.
This research is worth watching given the potential market size. However, there are many challenges in commercializing bacterial therapy. Need to watch who JAIST partners with for clinical development.
I knew Professor Miyako's lab was doing interesting research on insects and amphibians, but I never expected such groundbreaking results. It really reminds me of the importance of basic research.
The answer was in nature after all! Treatment methods derived from nature like this seem gentler on the body than chemically synthesized drugs. I sense the possibility of medicine that doesn't rely on artificial substances.
Caution: I hope this research doesn't lead people to folk remedies like 'eating frogs cures cancer' or 'extract frog intestines.' This is strictly about purified bacteria administered under controlled conditions.
My father is battling pancreatic cancer. We've been told current treatments are unlikely to help. I sincerely hope this research proves effective for other cancers and becomes practical as soon as possible.
The frogs are paying us back for all those years. Sorry for picking on you when I was a kid... From now on, I'll salute every frog I see.
The approach utilizing the interaction between gut bacteria and the immune system is a very promising direction in cancer research. It's impressive that the JAIST team achieved such results with natural bacteria without genetic modification. However, we need to be cautious about translating from mice to humans.
Microbiome research is thriving in China too, but the approach focusing on amphibian gut bacteria is refreshing. I'm impressed by the creativity of Japanese researchers. Our lab would like to consider replicating this study.
Fantastic research, but I'm concerned about how the media is reporting it. Phrases like 'cancer disappears' might give cancer patients false hope. It highlights the challenges of science communication.
Bacterial therapy clinical trials are already underway in Germany, but I've never seen such dramatic effects. I'd like to know more about what culture conditions the Japanese team used to reproduce these results.
In India, traditional medicine has long used substances derived from animals and plants. It's fascinating that modern science is rediscovering the value of these natural resources. A fusion of Eastern wisdom and Western science.
As an immunotherapy researcher, the mechanism of immune activation by bacteria is very intriguing. However, further verification is needed regarding the safety of intravenous administration of live bacteria, including sepsis risk.
As a cancer survivor, this research gives me great hope. Chemotherapy side effects were truly devastating. I sincerely hope gentler treatments are developed. Thank you to Japanese scientists.
Microbiome research is active in France too, centered on the Pasteur Institute, but the amphibian angle is novel. Isn't this a good example of Japan's 'interdisciplinary fusion' approach paying off?
From an investor's perspective, commercializing this technology faces major challenges. Mass production of live bacteria, quality control, transportation, storage... everything differs from conventional pharmaceuticals. But market potential is huge.
Cancer treatment research using gut bacteria is advancing in Korea too, but the Japanese team's approach is unique. If researchers from both countries collaborate, we might reach clinical application faster.
I'm an oncologist working at a Spanish hospital. This research is interesting, but there's a long road ahead before European regulators approve live bacterial therapy. Still, it's a ray of hope.
Russia has a history of bacterial therapy research dating back to the 1950s, though it's not well known in the West. I hope Japanese research sparks renewed interest and reevaluation of this field.
As Singapore's biomedical research hub, we're always watching innovative research like this. We'd like to explore collaboration possibilities with JAIST. The era of Asia leading global cancer research is coming.
As an environmental activist, I'm concerned about the impact this research might have on wild frog populations. As research progresses, don't we need ethical guidelines to prevent over-harvesting of wild frogs?
Cancer rates are rising in the Middle East and North Africa region. I hope advanced research like Japan's will eventually benefit patients in our region too. Science knows no borders.