The Cancer Killer Hiding in a Tree Frog’s Intestines

EARTH, Laniakea Supercluster—Some amphibians emit toxins to drive predators away. Some use natural camouflage to hide in dangerous environments. These versatile animals weaponize their biology for lifesaving feats, and now we know they harbor a potential human-saving cancer killer deep inside their bowels.

In a study published in Gut Microbes, researchers from the Japan Advanced Institute of Science and Technology (JAIST) isolated an organism known as Ewingella americana from the intestines of the Japanese tree frog (Dryophytes japonicus). It was one of 45 isolates that the team looked at—so what made it so special? Turns out it’s a T-800 for cancer cells.

The facultative anaerobe thrives inside tumors like they’re low-oxygen apartments that have leaky vessels for easy entry and weak security (little immune resistance). A single, intravenous dose in a mouse model of colorectal cancer sparked explosive growth of E. americana—3,000 fold in 24 hours. The microbe erased the disease with a multi-pronged attack that mixed cytotoxicity, or being a direct toxin for the cells, and immune recruitment—shaking the body’s immune system into action.

Unlike the superheroes in our favorite movies, the bacteria did their work without damaging the surrounding area. Treated mice achieved 100 percent complete response rates (every tumor eliminated). In other words, E. americana is a terrible houseguest for the malignant tumors…but great for the host.

“Our confidence increased as independent experiments consistently reproduced the findings,” Professor Eijiro Miyako of JAIST told Milky Way News in an email.

“The combination of direct cytotoxic activity, selective tumor accumulation, immune activation, and robust antitumor efficacy in the mouse model convinced us that this strain warranted much deeper investigation.”

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Cancer isn’t prevalent in amphibians like it is with other species, according to a 2023 review in the National Library of Medicine and confirmed by Miyako. That was the initial reasoning behind opening up the team’s microbial rabbit hole which led to the recent discovery. Although there was efficacy across the assortment of tested flora, E. americana stood out for its superb results.

The finding is an important discovery in the hunt for better ways to fight cancer and the 10 million deaths it causes each year, according to the World Health Organization (WHO). Even though myriad treatments already exist, scientists are digging into what looks like a largely untouched trove of therapeutic possibilities in amphibian microbiomes.

It seems like frogs are always doing something to intrigue scientists. Colorado River toads secrete 5-MeO-DMT, a potent, promising depression-fighting psychedelic. Ecuadorian poison frogs produce epibatidine, a painkiller roughly 200 times more potent than morphine. So, for a creature with such mind-boggling and mysterious capabilities, what else could it do to push the human experience into a new era? Apparently, the answer could be in the frog’s gut.

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For all the attention paid to human and mammalian microbiomes in cancer research, the microbial world inside amphibians and reptiles has gone largely uncharted. Miyako sees that gap as an opportunity.

“Amphibians occupy unique ecological niches and harbor gut microbial communities that have been much less explored than those of mammals or environmental sources such as soil,” Miyako wrote. “We believed that these underexplored microbial communities could contain bacteria with novel biological activities.”

As far as we can tell, mice aren’t human beings. Some of the findings from these furry guys probably won’t translate to us the same way. So, in the end, the journey to unlocking another part of humanity’s cancer-killing arsenal is still being puzzled out, but Miyako sees a larger picture.

“Surgery, chemotherapy, radiation therapy, immunotherapy, cell therapy, and potentially bacteria-based therapies each have different strengths and limitations,” he wrote.

“I think this field has tremendous potential, not only for developing new therapeutic agents but also for improving the effectiveness of existing cancer treatments.”

Frog gut exploration might give Tim Burton vibes, but tiny critters like the Japanese tree frog are creating very real optimism in the fight against one of humanity’s top banes. There’s an entire microbial world inside of frogs that could save your life one day—no kisses required.