The bacterium Ewingella americana, residing in the intestines of Japanese tree frogs (Dryophytes japonicus), eradicated malignant tumors in 100% of mice with a colorectal cancer model following a single intravenous injection. This research, conducted by scientists at the Japan Advanced Institute of Science and Technology, was published in the journal Gut Microbes.
Within 24 hours of administration, the bacterium accumulated in the tumor approximately 3,000 times more intensely than in healthy tissues—enabling a targeted attack without harming surrounding organs. The half-life was merely 1.2 hours, with the bacterium completely clearing from the body within a single day.
The mechanism proved twofold. First, Ewingella americana physically destroys cancer cells. Second, it triggers an immune cascade: activating T and B lymphocytes, neutrophils, and stimulating the release of TNF-α and interferon-γ. Evidently, the bacterium blocks the CD47 protein—a “do not eat me” signal that cancer uses to evade immune cells.
In direct comparison, Ewingella americana outperformed two standard cancer therapies: the immune checkpoint inhibitor anti-PD-L1 and the chemotherapeutic agent liposomal doxorubicin.
The authors—Seigo Iwata, Nagi Yamashita, Kensuke Asukabe, Matomo Sakari, and Eijiro Miyako—emphasize that this marks the first study achieving a complete tumor response using a bacterium derived from the amphibian gut. Further safety evaluations will be necessary before human clinical trials, yet the findings open a fundamentally new avenue in “live” anticancer therapy.Bacterium Ewingella americana, which naturally occurs in the gut of Japanese tree frogs (Dryophytes japonicus), achieved complete elimination of malignant tumors in 100% of mice with a colorectal cancer model following a single intravenous injection. The study, led by researchers at the Japan Advanced Institute of Science and Technology, has been published in the journal Gut Microbes.
Within 24 hours of administration, the bacterium accumulated in tumor sites roughly 3,000 times more densely than in healthy tissues—enabling precise targeting without collateral damage to surrounding organs. Its half-life was only around 1.2 hours, and the bacterium was entirely cleared from the body within one day.
The underlying mechanism proved to operate on two distinct levels. First, Ewingella americana directly destroys cancer cells through physical means. Second, it initiates an immune response cascade: activating T and B lymphocytes and neutrophils, while driving the release of TNF-α and interferon-γ. The bacterium appears to block the CD47 protein—a “don’t eat me” signal that cancer cells exploit to evade detection by the immune system.
In head-to-head comparisons, Ewingella americana outperformed two established cancer treatments: the immune checkpoint inhibitor anti-PD-L1 and the chemotherapeutic drug liposomal doxorubicin.
The study authors—Seigo Iwata, Nagi Yamashita, Kensuke Asukabe, Matomo Sakari, and Eijiro Miyako—stress that this is the first instance of a complete tumor response achieved using a bacterium sourced from the intestinal tract of amphibians. Additional safety evaluations are needed before human clinical trials can proceed, but these findings lay the groundwork for a fundamentally novel direction in “living” anti-cancer therapy.
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