Researchers reveal powerful anticancer effects of a frog’s gut bacteria

What if one of the most promising new weapons against cancer didn’t come from a high-tech lab or a synthetic drug — but from nature itself? A team of researchers has ventured into an unexplored frontier between microbiology, immunology, and wildlife. Their work has revealed a surprising biological mechanism and remarkable results — a breakthrough that challenges how we think about developing cancer treatments.

It’s long been known that an imbalance in the body’s microbiota, or “dysbiosis,” can lead to serious health issues, including cancer. This relationship between gut microorganisms and tumor development may explain, for example, why fiber — which supports a healthy microbiome — offers protection, while red meat — which disrupts it — increases cancer risk.

A bold and unconventional approach

Most studies on microbiota and cancer have focused on indirect methods such as microbiome modulation or fecal transplants. But scientists at Japan’s Advanced Institute of Science and Technology (JAIST) took a radically different path — one that’s as bold as it is innovative.

They isolated and cultured 45 bacterial strains from the digestive tracts of frogs, newts, and lizards — including Japanese tree frogs (Dryophytes japonicus), red-bellied newts (Cynops pyrrhogaster), and grass lizards (Takydromus tachydromoides).

These bacteria were then injected intravenously into mice with colorectal tumors. After several weeks, the researchers examined the results — and what they found was astonishing.

A bacterium with superpowers

According to findings published in Gut Microbes, nine of the 45 bacterial strains showed strong tumor-fighting properties, but one stood out from the rest: Ewingella americana. This bacterium achieved a complete remission rate of 100% — meaning it completely eradicated all visible signs of cancer.

Even more impressively, Ewingella americana outperformed several current frontline treatments, including immune checkpoint inhibitors (anti–PD-L1 antibodies) and the chemotherapy drug liposomal doxorubicin. So, what makes it so powerful?

Two-pronged anticancer action

The researchers found that Ewingella americana fights tumors through two complementary mechanisms:

• Direct action: As an anaerobic organism, it thrives in oxygen-poor environments like tumor tissue, allowing it to multiply rapidly and unleash its natural cytotoxic effects.
• Indirect action: Its presence in the body stimulates the immune system, drawing T cells, B cells, and neutrophils to the tumor site — where they join the attack on cancer cells.

Safe, effective, and natural

Several factors make Ewingella americana especially promising. The immune system doesn’t target it, blood vessels allow it to penetrate tumor tissue, and certain tumor-related metabolites even encourage its growth.

Perhaps most importantly, it appears remarkably safe. The bacterium disappears from the bloodstream within 24 hours, never colonizes healthy organs such as the liver or lungs, causes only a mild and temporary inflammatory response, and shows no signs of toxicity even after 60 days.

Encouraged by these results, the researchers now plan to test Ewingella americana against other cancer types, including breast, pancreatic, and skin cancers. They’ll also explore whether combining it with other therapies — such as immunotherapy or chemotherapy — could enhance its effectiveness, especially in treatment-resistant cases.

Ultimately, this discovery is a reminder that nature remains one of the richest sources of medical innovation — and we’ve only just begun to uncover its potential.

Véronique Molénat

Journalist

Decoding how the body works—from organs, tissues and cells all the way down to organelles, molecules and atoms. Understanding how these elements fit together to create living systems. Figuring out why those systems sometimes go off-track. And then explaining it all in clear, accessible language. That has been my driving force for 30 years.

Trained in cell biology, animal physiology, nutrition, public health, and finally in science communication, I have explored health from many angles. Today, I put that expertise in the service of anyone who wants to make science understandable to all.